Smoking is a serious global public health problem. The ability to quit smoking is closely related... more Smoking is a serious global public health problem. The ability to quit smoking is closely related to age; in addition, personal determination and education usually play an important role in quitting smoking. In order to capture such characteristics, we developed a novel age-structured smoking dynamical model. By defining the smoking generation number [Formula: see text], the local stability, global stability of the boundary equilibrium and endemic equilibrium are obtained using Lyapunov functions. The uniform persistence and the well-posedness and asymptotic smoothness of the solutions are also studied. Sensitivity analyzes show that the lower the age of onset of smoking and the higher the determination to stop, the greater the likelihood of quitting smoking and numerical studies support the theoretical results.
Blackwell Publishing, LtdLack of genetic and plumage differentiation in the red-billed quelea Que... more Blackwell Publishing, LtdLack of genetic and plumage differentiation in the red-billed quelea Quelea quelea across a migratory divide in southern
International Journal of Bifurcation and Chaos, 2016
Surgery is the traditional method for treating cancers, but it often fails to cure patients for c... more Surgery is the traditional method for treating cancers, but it often fails to cure patients for complex reasons so new therapeutic approaches that include both surgery and immunotherapy have recently been proposed. These have been shown to be effective, clinically, in inhibiting cancer cells while allowing retention of immunologic memory. This comprehensive strategy is guided by whether a population of tumour cells has or has not exceeded a threshold density. Conditions for successful control of tumours in an immune tumour system were modeled and the related dynamics were addressed. A mathematical model with state-dependent impulsive interventions is formulated to describe combinations of surgery with immunotherapy. By analyzing the properties of the Poincaré map, we examine the global dynamics of the immune tumour system with state-dependent feedback control, including the existence and stability of the semi-trivial order-1 periodic solution and the positive order-[Formula: see tex...
Cheke, R.A., Van der Walt, E., Mbereki, C., Mtobesya, B.N., Magoma, R.N., Farman, D.I., Adranyi, ... more Cheke, R.A., Van der Walt, E., Mbereki, C., Mtobesya, B.N., Magoma, R.N., Farman, D.I., Adranyi, E., McWilliam, A.
Please note that where the full text version provided on GALA is not the final published version,... more Please note that where the full text version provided on GALA is not the final published version, the version made available will be the most up-to-date full-text (post-print) version as provided by the author(s). Where possible, or if citing, it is recommended that the publisher’s (definitive) version be consulted to ensure any subsequent changes to the text are noted. Citation for this version held on GALA:
Red-billed Quelea birds (Quelea quelea) are major pests of small-grain crops throughout sub-Sahar... more Red-billed Quelea birds (Quelea quelea) are major pests of small-grain crops throughout sub-Saharan Africa. These abundant birds breed colonially when conditions permit, migrating long distances, sometimes more than 2000km, to seek appropriate breeding areas or to avoid food shortage. The birds breed in the wet season and spend the dry seasons where there are sufficient seeds of their preferred grasses available. At the start of the rains, grass seeds germinate after a threshold quantity of rain has fallen, forcing the birds to move to zones where the seeds have yet to germinate. When rain reaches the latter areas, the birds are forced to move again, usually returning in “early-rains migrations ” in the direction whence they came. By this time sufficient rain needs to have fallen to exceed another threshold within a restricted period for the new grass to have produced fresh seed. Breeding may then commence. It is the fledging birds that cause most damage to agriculture. The adult bi...
Tropical medicine and parasitology : official organ of Deutsche Tropenmedizinische Gesellschaft and of Deutsche Gesellschaft fur Technische Zusammenarbeit (GTZ), 1991
Savanna species of the Simulium damnosum complex, the major vectors of the blinding savanna type ... more Savanna species of the Simulium damnosum complex, the major vectors of the blinding savanna type of onchocerciasis, were considered to be rare in Liberia, until the dry season of 1988. In 1988 they became a serious nuisance, biting people at the Bong iron ore mine within the rain forest zone. S. damnosum s.str. and S. sirbanum were found breeding, in association with S. adersi a non man-biting savanna species, in a stream emerging from the mine's tailings pond. The local forest species were extremely rare in this stream. The water of the stream was characterized by an increased hardness and higher temperatures in comparison with those of natural watercourses in the area. The mass occurrence of flies was probably related to expansions of the tailings ponds, when rich nutrition was provided for the blackfly larvae by the decaying forests submerged by the rising water levels. The phenomenon did not recur in 1989 when only a few savanna flies were caught, and none were seen in the d...
Tropical medicine and parasitology : official organ of Deutsche Tropenmedizinische Gesellschaft and of Deutsche Gesellschaft fur Technische Zusammenarbeit, 1988
Adult female Simulium damnosum s.l. were caught at human and cattle bait at Djodji in Togo. Two m... more Adult female Simulium damnosum s.l. were caught at human and cattle bait at Djodji in Togo. Two members of the Simulium damnosum complex, the Djodji form of S. sanctipauli (74.9% of the total catch) and S. squamosum (25.1%), were identified and both were mainly anthropophilic. Although each species was also recorded feeding on cattle or turkey baits, most flies which were caught at animal baits did not take blood from them. Flies caught unfed at the cattle bait tended to be larger and have higher parous rates than those caught on man. S. sanctipauli flies were on average larger than S. squamosum but the sizes of both species varied seasonally. Infections with Onchocerca volvulus were found in both species. The infection rates varied seasonally with the highest levels occurring in the wet season. The Djodji form of S. sanctipauli is potentially a much more efficient vector (162 L3/1000 biting flies) than both S. squamosum (48 L3/1000 biting flies) and the S. sanctipauli s.l. found in...
Different subspecies of Red-billed Quelea, Quelea quelea, occur in different parts of Africa and ... more Different subspecies of Red-billed Quelea, Quelea quelea, occur in different parts of Africa and each has its own migration pathways determined by local rainfall patterns and the availability of grass seed. The migration patterns of Q. q. lathamii, the subspecies present in southern Africa, began to be understood in the 1970s. Only now, however, are sufficient remote-sensed data on rainfall distribution and vegetation growth available over southern Africa as a whole to make the accurate prediction of quelea movements in any one year a realistic possibility. The DFID-funded project ‘Models of quelea movements and improved control strategies’ has assembled a computerised database of 3543 historical records of quelea occurrences throughout southern Africa, from which a forecasting model has been developed to assist pest managers in predicting control needs and targeting them effectively. In parallel with this project, a DNA microsatellite study is being conducted to try to identify pos...
The numbers of maturing oocytes in gravid Simulium damnosum s.l. were related to the sizes of the... more The numbers of maturing oocytes in gravid Simulium damnosum s.l. were related to the sizes of the flies and when this was taken into account the numbers fell into two groups. It was concluded that the group with the highest oocyte counts were nulliparous and that the remainder were parous flies. No evidence was found to suggest that flies in their third or subsequent gonotrophic cycles matured fewer oocytes than those in their second cycles. However, the results did suggest reduced fecundity of those flies infected with Onchocerca spp. The frequency distributions of the Onchocerca spp. infections for each of three different stages can be fitted to negative binomial distributions with similar values (0·04–0·07) for the parameter k.
Smoking is a serious global public health problem. The ability to quit smoking is closely related... more Smoking is a serious global public health problem. The ability to quit smoking is closely related to age; in addition, personal determination and education usually play an important role in quitting smoking. In order to capture such characteristics, we developed a novel age-structured smoking dynamical model. By defining the smoking generation number [Formula: see text], the local stability, global stability of the boundary equilibrium and endemic equilibrium are obtained using Lyapunov functions. The uniform persistence and the well-posedness and asymptotic smoothness of the solutions are also studied. Sensitivity analyzes show that the lower the age of onset of smoking and the higher the determination to stop, the greater the likelihood of quitting smoking and numerical studies support the theoretical results.
Blackwell Publishing, LtdLack of genetic and plumage differentiation in the red-billed quelea Que... more Blackwell Publishing, LtdLack of genetic and plumage differentiation in the red-billed quelea Quelea quelea across a migratory divide in southern
International Journal of Bifurcation and Chaos, 2016
Surgery is the traditional method for treating cancers, but it often fails to cure patients for c... more Surgery is the traditional method for treating cancers, but it often fails to cure patients for complex reasons so new therapeutic approaches that include both surgery and immunotherapy have recently been proposed. These have been shown to be effective, clinically, in inhibiting cancer cells while allowing retention of immunologic memory. This comprehensive strategy is guided by whether a population of tumour cells has or has not exceeded a threshold density. Conditions for successful control of tumours in an immune tumour system were modeled and the related dynamics were addressed. A mathematical model with state-dependent impulsive interventions is formulated to describe combinations of surgery with immunotherapy. By analyzing the properties of the Poincaré map, we examine the global dynamics of the immune tumour system with state-dependent feedback control, including the existence and stability of the semi-trivial order-1 periodic solution and the positive order-[Formula: see tex...
Cheke, R.A., Van der Walt, E., Mbereki, C., Mtobesya, B.N., Magoma, R.N., Farman, D.I., Adranyi, ... more Cheke, R.A., Van der Walt, E., Mbereki, C., Mtobesya, B.N., Magoma, R.N., Farman, D.I., Adranyi, E., McWilliam, A.
Please note that where the full text version provided on GALA is not the final published version,... more Please note that where the full text version provided on GALA is not the final published version, the version made available will be the most up-to-date full-text (post-print) version as provided by the author(s). Where possible, or if citing, it is recommended that the publisher’s (definitive) version be consulted to ensure any subsequent changes to the text are noted. Citation for this version held on GALA:
Red-billed Quelea birds (Quelea quelea) are major pests of small-grain crops throughout sub-Sahar... more Red-billed Quelea birds (Quelea quelea) are major pests of small-grain crops throughout sub-Saharan Africa. These abundant birds breed colonially when conditions permit, migrating long distances, sometimes more than 2000km, to seek appropriate breeding areas or to avoid food shortage. The birds breed in the wet season and spend the dry seasons where there are sufficient seeds of their preferred grasses available. At the start of the rains, grass seeds germinate after a threshold quantity of rain has fallen, forcing the birds to move to zones where the seeds have yet to germinate. When rain reaches the latter areas, the birds are forced to move again, usually returning in “early-rains migrations ” in the direction whence they came. By this time sufficient rain needs to have fallen to exceed another threshold within a restricted period for the new grass to have produced fresh seed. Breeding may then commence. It is the fledging birds that cause most damage to agriculture. The adult bi...
Tropical medicine and parasitology : official organ of Deutsche Tropenmedizinische Gesellschaft and of Deutsche Gesellschaft fur Technische Zusammenarbeit (GTZ), 1991
Savanna species of the Simulium damnosum complex, the major vectors of the blinding savanna type ... more Savanna species of the Simulium damnosum complex, the major vectors of the blinding savanna type of onchocerciasis, were considered to be rare in Liberia, until the dry season of 1988. In 1988 they became a serious nuisance, biting people at the Bong iron ore mine within the rain forest zone. S. damnosum s.str. and S. sirbanum were found breeding, in association with S. adersi a non man-biting savanna species, in a stream emerging from the mine's tailings pond. The local forest species were extremely rare in this stream. The water of the stream was characterized by an increased hardness and higher temperatures in comparison with those of natural watercourses in the area. The mass occurrence of flies was probably related to expansions of the tailings ponds, when rich nutrition was provided for the blackfly larvae by the decaying forests submerged by the rising water levels. The phenomenon did not recur in 1989 when only a few savanna flies were caught, and none were seen in the d...
Tropical medicine and parasitology : official organ of Deutsche Tropenmedizinische Gesellschaft and of Deutsche Gesellschaft fur Technische Zusammenarbeit, 1988
Adult female Simulium damnosum s.l. were caught at human and cattle bait at Djodji in Togo. Two m... more Adult female Simulium damnosum s.l. were caught at human and cattle bait at Djodji in Togo. Two members of the Simulium damnosum complex, the Djodji form of S. sanctipauli (74.9% of the total catch) and S. squamosum (25.1%), were identified and both were mainly anthropophilic. Although each species was also recorded feeding on cattle or turkey baits, most flies which were caught at animal baits did not take blood from them. Flies caught unfed at the cattle bait tended to be larger and have higher parous rates than those caught on man. S. sanctipauli flies were on average larger than S. squamosum but the sizes of both species varied seasonally. Infections with Onchocerca volvulus were found in both species. The infection rates varied seasonally with the highest levels occurring in the wet season. The Djodji form of S. sanctipauli is potentially a much more efficient vector (162 L3/1000 biting flies) than both S. squamosum (48 L3/1000 biting flies) and the S. sanctipauli s.l. found in...
Different subspecies of Red-billed Quelea, Quelea quelea, occur in different parts of Africa and ... more Different subspecies of Red-billed Quelea, Quelea quelea, occur in different parts of Africa and each has its own migration pathways determined by local rainfall patterns and the availability of grass seed. The migration patterns of Q. q. lathamii, the subspecies present in southern Africa, began to be understood in the 1970s. Only now, however, are sufficient remote-sensed data on rainfall distribution and vegetation growth available over southern Africa as a whole to make the accurate prediction of quelea movements in any one year a realistic possibility. The DFID-funded project ‘Models of quelea movements and improved control strategies’ has assembled a computerised database of 3543 historical records of quelea occurrences throughout southern Africa, from which a forecasting model has been developed to assist pest managers in predicting control needs and targeting them effectively. In parallel with this project, a DNA microsatellite study is being conducted to try to identify pos...
The numbers of maturing oocytes in gravid Simulium damnosum s.l. were related to the sizes of the... more The numbers of maturing oocytes in gravid Simulium damnosum s.l. were related to the sizes of the flies and when this was taken into account the numbers fell into two groups. It was concluded that the group with the highest oocyte counts were nulliparous and that the remainder were parous flies. No evidence was found to suggest that flies in their third or subsequent gonotrophic cycles matured fewer oocytes than those in their second cycles. However, the results did suggest reduced fecundity of those flies infected with Onchocerca spp. The frequency distributions of the Onchocerca spp. infections for each of three different stages can be fitted to negative binomial distributions with similar values (0·04–0·07) for the parameter k.
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Papers by R.A. Cheke