Geomorphological aspects of the process of desertification in Western Sudan     

Abdelhamid Bakhit Dr.  F. N. Ibrahim 《GeoJournal》1982,6(1):19-24

Desertification involves several morphodynamic processes which serve as indicators of the highly complex process of desertification and thus play an important role in its monitoring. Ecological degradation triggers off and enhances these morphological activities, which are mainly processes of soil changes, soil erosion, and the transport and accumulation of soils. These alterations of relief and soil result in hydrological changes which have negative effects on land productivity. Both geomorphological and desertification processes are so interwoven that it becomes difficult to differentiate clearly between causes and effects. As the field studies tackled here have been carried out in the sandy regions of western Sudan, special attention is being paid to aeolian erosion and accumulation. Fluvial processes play only a subsidiary role in the processes of desertification there.  相似文献   

Ecological and economic problems of the Qattara-depression project,Egypt     

F. N. Ibrahim 《GeoJournal》1982,6(1):88-89

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Book reviews     

A. M. O'Connor  Fouad Ibrahim  W. F. Schmidt-Eisenlohr  Olof Nordström  Gunnar Alexandersson  Lutz Holzner  L. A. Kosiński 《GeoJournal》1978,2(5):492-494

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Seismicity of the northernmost part of the Red Sea (1995–1999)     

I. M. Korrat  H. M. Hussein  I. Marzouk  E. M. Ibrahim  R. Abdel-Fattah  N. Hurukawa 《Acta Geophysica》2006,54(1):33-49

Seismicity in the northernmost part of the Red Sea has been studied using data from Hurghada Seismological Network in addition to readings from the existing neighbouring networks. Relocated events in addition to data from national centers are used to obtain a complete and true picture for the seismicity of the area. The spatial distribution of earthquakes defines three earthquake zones in the Gulf of Aqaba and three zones at the entrance of the Gulf of Suez and southern tip of Sinai Peninsula. The thermal activity and the triple junction nature control the activity in this area. The activity defines also an active trend extending from the southern tip of Sinai Peninsula to the median zone of the Red Sea. The seismicity of this trend is probably related to the active spreading zone associated with the opening of the Red Sea. The b-values are derived for the entrance areas of the two gulfs and for Gulf of Aqaba. Values of b are 1.35 for the triple junction region, 1.13 for the activity before the 22 November 1995 Gulf of Aqaba mainshock and 1.25 for the aftershocks of this event.  相似文献   

Carbon monoxide levels along roadway     

F. W. L. Kho B.Sc.  P. L. Law B.SCE.  M.SCE.  M.Sc.  Sc.D.  S. H. Ibrahim M.S.c  Ph.D.  J. Sentian B.Sc.  M.Sc. 《International Journal of Environmental Science and Technology》2007,4(1):27-34

This paper predicts and compares the carbon monoxide (CO) concentration levels along Sembulan Road for years 2004 and 2014 using CAL3QHC air dispersion model at two major locations, i.e., at Sembulan Roundabout and Sutera Harbour Intersection, Kota Kinabalu, Sabah, Malaysia. The CO concentration “hot-spots” were also identified at Sutera Harbour Intersection, and the highest maximum 1-hr average ground level concentrations of CO modeled for Kpg. Air Sembulan located in the northeast of idling road was 9.33 ppm for year 2004. This study showed that there would be no extreme changes in CO concentration trends for year 2014 although a substantial increase in the number of vehicles is assumed to affect the level of CO concentrations. It was also found that the CO levels would be well below the Malaysian Ambient Air Quality Guidelines of 30 ppm for 1-hour Time-Weighted Average (TWA). Comparisons between the modeled and observed outputs using quantitative data analysis technique and statistical methods indicated that the CAL3QHC predicted results correlated well with measured data. It was predicted that receptors located near to the major intersection, in the long-term would be potentially exposed to relatively higher CO levels.  相似文献   

Petrography and geochemistry of carbonate void-filling cements in fossil reefs     

Dr. Ibrahim A. Mirsal  Prof. Dr. Heinrich Zankl 《International Journal of Earth Sciences》1979,68(3):920-951

An Investigation of the distribution of Ca²⁺, Mg²⁺, Na⁺, Sr²⁺ and K⁺ as well as O¹⁸ and C¹³ in void-filling cements out of three fossil reefs — of Devonian and Triassic ages — shows a rhythmic fluctuation of these parameters in the successive layers. This reflects a similar change in the salinity conditions during cementation. It also leads to the presumption that the void filling process starts in early stages with a semi-closed system and later passes into a relatively closed one. Results obtained from factor analysis support this hypothesis.The original mineralogic constitution of the cements must have followed the rhythmic fluctuation of salinity with the result of forming alternative layers of aragonite and calcite. These lead, through inversion and grain growth, in later diagenetic stages to the formation of fibrous calcite.Blocky calcite represents the last stage of cementation. It crystallises out of exhausted solutions and shows no signs of inversion.Multivariate analysis of all investigated parameters reveals three factors. These were interpreted as representing Salinity, Temperature and original Mineralogy.

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Zusammenfassung Die Untersuchung der Verteilung von Ca²⁺, Mg²⁺, Na⁺, Sr²⁺ und K⁺, sowie O¹⁸ und C¹³ in Hohlraumzementen aus drei fossilen Riffen von devonischem und triadischem Alter zeigt eine rhythmische Schwankung in den sukzessiven Zementschalen. Die Schwankung der geochemischen Parameter reflektiert eine änderung der Salinitätsbedingungen. Dies wird unter der Annahme erklärt, daß die Ausfüllung der Hohlräume zuerst in einem halbgeschlossenen, später dann in einem relativ geschlossenen System stattfindet. Die Faktorenanalyse bestätigt diese Hypothese.Die Mineralogie der gebildeten Zemente folgt der rhythmischen Salinitätsschwankung und daraus entstand zunächst eine Wechsellagerung von calcitischen und aragonitischen Zementen.über Inversion und Sammelkristallisation bildet sich während der späteren Diagenese der fibröse Calcit, dessen rhythmische Gefügeabfolge von der ursprünglichen Mineralogie der Zemente diktiert wird. Als letzte Zementgeneration folgt blockiger Calcit aus ionenarmen Lösungen, wobei keine Umwandlung dieser Zementphase mehr erfolgt.Aus der Faktorenanalyse aller geochemischen Parameter ergeben sich drei Faktorengruppen, die die Salinität, Temperatur und ursprüngliche Bildungsmineralogie charakterisieren.

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Résumé L'examen de la répartition du Ca₂₊, Mg₂₊, Na₊, Sr₂₊ et K₊, ainsi que O¹⁸ et C¹³ dans le ciment de remplissage des vides de 3 récifs fossiles d'âge dévonien à triasique, montre une variation rythmique dans les couches successives du ciment. La variation des paramètres chimiques reflète un changement dans les conditions de la salinité. Ceci s'explique si l'on accepte que le remplissage des vides a eu lieu dans un milieu d'abord à moitié fermé, et plus tard relativement fermé. L'analyse des facteurs confirme cette hypothèse. La minéralogie du ciment formé est conforme à la variation rythmique de la salinité, d'où résulta une alternance de ciment calcitique et aragonitique.Après l'inversion et la recristallisation coalescente, il s'est formé, durant la diagenèse ultérieure de la calcite fibreuse, dont la succession structurale rythmique est dictée par la minéralogie originelle du ciment. Comme dernière génération de ciment, vient de la calcite en bloc provenant d'une solution pauvre en ions, sans qu'il s'en suive une transformation decette phase de cimentation.L'analyse des facteurs de tous les paramètres chimiques fait apparaÎtre trois groupes de facteurs qui caractérisent la salinité, la température et la minéralogie originelle de formation.

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, : Sa²⁺, Mg²⁺, Na²⁺, Sr²⁺ K⁺, ¹⁸O ¹³S . . , , , . . , . , . , , - . 3 , , .

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Short note: A simple nomogram for interpretation due to magnetic horizontal cylinders     

Ibrahim Kara  Davut Aydogan  F. Ahmet Yüksel 《Geophysical Prospecting》1998,46(6):659-663

The magnetic anomaly ΔF due to a long horizontal cylinder yields three points related to its extrema. A nomogram is presented for the determination of some source parameters of the causative body.  相似文献   

On the iron interpretation of the 6.4 keV emission line from SGR 1900+14     

Alaa I. Ibrahim  Hisham Anwer  Mohamed H. Soliman  Nicholas Mackie-Jones  Kalvir S. Dhuga  William C. Parke  Jean H. Swank  Tilan Ukwatta  M. T. Hussein  T. El-Sherbini 《Astrophysics and Space Science》2007,308(1-4):535-539

A 6.4 keV emission line was discovered in an unusual burst from the soft gamma repeater SGR 1900+14 with the Rossi X-ray Timing Explorer (RXTE). The line was detected in part of a complex multipeak precursor that preceded the unusual burst of 1998 August 29, i.e. two days after the giant flare of August 27 from the source. The origin of the line was not firmly identified and two possible interpretations were equally plausible including (a) Kα fluorescence from a small iron rich material that was ejected to the magnetosphere during the August 27 flare, and (b) proton or α-particle cyclotron resonance. If the iron scenario was correct, we expect to find evidence for the line during the intervening interval between the flare and the August 29 burst, i.e. on August 28. Here we present the results of the August 28 burst observation, taken with RXTE. We detect a total of seven bursts whose individual and joint spectra do not show evidence for spectral lines. We also investigated a sample of nine bursts before and after the August 29 burst (from 1998 June to December) that do not reveal evidence for a spectral line near 6.4 keV or elsewhere. These results disfavor the iron scenario and make the proton/α-particle cyclotron resonance interpretation more plausible. The appearance of the emission line in part of a complex burst and its absence from the studied sample indicate that the line is likely due to a transient phenomenon that may depend on the burst morphology, energetics and the properties of the emission region.   相似文献   

Relationships Between Interplanetary Coronal Mass Ejection Characteristics and Geoeffectiveness in the Rising Phase of Solar Cycles 23 and 24   总被引：1，自引：0，他引：1  

M. Bendict Lawrance  A. Shanmugaraju  Y.-J. Moon  M. Syed Ibrahim  S. Umapathy 《Solar physics》2016,291(5):1547-1560

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Prevalence and distribution of fecal indicator organisms in South Florida beach sand and preliminary assessment of health effects associated with beach sand exposure   总被引：2，自引：1，他引：1  

Bonilla TD  Nowosielski K  Cuvelier M  Hartz A  Green M  Esiobu N  McCorquodale DS  Fleisher JM  Rogerson A 《Marine pollution bulletin》2007,54(9):1472-1482

Fecal indicator levels in nearshore waters of South Florida are routinely monitored to assess microbial contamination at recreational beaches. However, samples of sand from the surf zone and upper beach are not monitored which is surprising since sand may accumulate and harbor fecal-derived organisms. This study examined the prevalence of fecal indicator organisms in tidally-affected beach sand and in upper beach sand and compared these counts to levels in the water. Since indicator organisms were statistically elevated in sand relative to water, the study also considered the potential health risks associated with beach use and exposure to sand. Fecal coliforms, Escherichia coli, enterococci, somatic coliphages, and F(+)-specific coliphages were enumerated from sand and water at three South Florida beaches (Ft. Lauderdale Beach, Hollywood Beach, and Hobie Beach) over a 2-year period. Bacteria were consistently more concentrated in 100g samples of beach sand (2-23 fold in wet sand and 30-460 fold in dry sand) compared to 100ml samples of water. Somatic coliphages were commonly recovered from both sand and water while F(+)-specific coliphages were less commonly detected. Seeding experiments revealed that a single specimen of gull feces significantly influenced enterococci levels in some 3.1m(2) of beach sand. Examination of beach sand on a micro-spatial scale demonstrated that the variation in enterococci density over short distances was considerable. Results of multiple linear regression analysis showed that the physical and chemical parameters monitored in this study could only minimally account for the variation observed in indicator densities. A pilot epidemiological study was conducted to examine whether the length of exposure to beach water and sand could be correlated with health risk. Logistic regression analysis results provided preliminary evidence that time spent in the wet sand and time spent in the water were associated with a dose-dependent increase in gastrointestinal illness.  相似文献