Beam steered graphene-based Yagi-Uda array antenna with a transverse magnetic to hybrid mode conversion approach.

This work presents the existence of the mode conversion technique in a graphene-based Yagi-Uda array antenna. It comprises four arrays whose strands are placed on a silicon dioxide substrate, and are eventually connected with the graphene ring. All four driven elements of the Yagi-Uda array antenna are excited through the 50Ω silver nanostrip feedline. The proposed antenna offers mode conversion due to variation of the chemical potential of graphene. It controls conversion of the TM32δ to HEM21δ mode of the antenna. This is attributed to the change in the biasing voltage of graphene. This in turn shifts the radiation pattern from the end-fire to the broadside direction, which effectively confirms the beam reconfigurability. This antenna provides a high directivity of 12.21 dBi at 4.55 THz center frequency. The proposed antenna is designed and analyzed by using CST Microwave Studio, which is based on the finite difference time domain scheme. The beam steered graphene-based antenna has been utilized for several terahertz communication systems.

Effect of nation-wide lock-down due to Covid-19 over industrial pollution in Delhi, India.

In India, very first infection due to Covid-19 was reported by end of January 2020 and, the same has been increased with the span of time. In order to fight the increasing risk among the citizens of nation, the complete lock-down was declared on March 25, 2020 for initially 21 days and thereafter it has been subsequently increased up to its present 4th phase, which would be remain continue until May 31, 2020. First two phases of lock-down were imposed without any relaxation, however, there were gradual relaxation implemented in third and fourth lock-down phases. Air pollution depends on emission of the pollutants from vehicles and industries, as well as dust from construction activities. Due to lock-down, operations concerning these activities were completely shut down. The effect of lock-down on PM2.5, PM10, NO2, SO2, CO and AQI level was studied and comparison of PM2.5, PM10, NO2, SO2, CO and AQI during lock-down with same dates of previous year was also considered.

Peristaltic Creeping Flow of Power Law Physiological Fluids through a Nonuniform Channel with Slip Effect.

A mathematical study on creeping flow of non-Newtonian fluids (power law model) through a nonuniform peristaltic channel, in which amplitude is varying across axial displacement, is presented, with slip effects included. The governing equations are simplified by employing the long wavelength and low Reynolds number approximations. The expressions for axial velocity, stream function, pressure gradient, and pressure difference are obtained. Computational and numerical results for velocity profile, pressure gradient, and trapping under the effects of slip parameter, fluid behavior index, angle between the walls, and wave number are discussed with the help of Mathematica graphs. The present model is applicable to study the behavior of intestinal flow (chyme movement from small intestine to large intestine). It is also relevant to simulations of biomimetic pumps conveying hazardous materials, polymers, and so forth.

Immunogenetic influences on tick resistance in African cattle with particular reference to trypanotolerant N'Dama (Bos taurus) and trypanosusceptible Gobra zebu (Bos indicus) cattle.

In sub-Saharan Africa, tick infestation and tick-borne infections together with tsetse-transmitted trypanosomosis arguably constitute the main parasitological disease complex constraining livestock production. Resistance to tick attack and tick-borne micro-organisms (TBMs) varies among different breeds of cattle. The magnitude of losses due to these parasites is related to an extent to the degree of breed resistance. Generally, zebu (Bos indicus) cattle possess a higher resistance to ticks and TBMs than European (Bos taurus) cattle. The host's immune system would appear to be the single most important factor that regulates this resistance. This paper reports on the main effector immune mechanisms governing resistance against ticks and TBMs. The cellular immune response appears more effective and stable than humoral immunity in modulating resistance to ticks and TBMs. Similarities between the immune mechanisms employed by trypanotolerant N'Dama (B. taurus) cattle, when infected with trypanosomes, and those elicited by tick bites and TBMs seem to exist, particularly at the skin level in the early phases of parasitic invasion. Moreover, there is evidence that in the N'Dama breed, resistance against ticks per se also has a genetic basis. Therefore, the N'Dama appears to be a unique breed in that it exhibits resistance to several parasitic diseases and/or infections, including helminths, when compared to other cattle breeds in West Africa. It is concluded that the multi-parasite resistant traits of the N'Dama breed should be exploited in those areas where trypanosomosis, ticks and tick-borne diseases constrain animal production. This should be of benefit for low-input farming systems where the use of chemicals for prophylaxis and therapy is limited by their relatively high cost. Additionally, the potential contribution of multiple disease resistant N'Dama cattle should be considered in crossbreeding programmes with exotic dairy breeds for increasing milk production in West Africa.

Trypanosome infections and tick infestations: susceptibility in N'Dama, Gobra zebu and Gobra x N'Dama crossbred cattle exposed to natural challenge and maintained under high and low surveillance of trypanosome infections.

Susceptibility to trypanosome infections and tick infestations was assessed in 51 N'Dama, 48 Gobra zebu and 37 Gobra x N'Dama crossbred (F1) cattle exposed to field-tick infestations and natural high tsetse challenge over more than one year. From these cattle, 12 animals of each breed were randomly selected and examined parasitologically for trypanosome infections and packed cell volume (PCV) twice a week (high surveillance, group HS). In the remaining 100 cattle trypanosome infection and PCV were monitored monthly (low surveillance, group LS). Mortality rates were recorded in both groups. Tick infestation was quantified fortnightly from all animals in group HS and from four to seven randomly selected animals of each breed in group LS. In both HS and LS groups, trypanocidal drug treatment was administered to trypanosome positive animals with PCV equal to or less than 20% or when they showed clinical evidence (dullness, weight loss) of trypanosomosis. In both groups, N'Dama cattle exhibited a superior capacity to control trypanosome infections and limit tick burdens. Particularly, in group HS N'Dama cattle showed lower trypanosome infection rate, higher mean PCV value, lower requirement for trypanocide treatments and lower tick load than crossbred and Gobra cattle in the corresponding group (P < 0.05 or greater). This was also true in N'Damas in comparison with crossbreds in group LS. Unfortunately, the high mortality occurring in Gobra cattle in group LS did not allow within group comparative analysis between N'Dama, Gobra and crossbred cattle overall the study period. No death occurred in N'Dama cattle maintained under high surveillance of trypanosome infection, while approximately 8% of crossbreds and 50% of Gobras died of trypanosomosis. In group LS, all Gobra and more than 70% of crossbred cattle died. In this group, mortality in N'Dama was limited to less than 16%. In both groups, differences in mortality were significantly higher (P < 0.01) in Gobras than in N'Damas. Within breed, animals of the three breeds maintained under high surveillance of trypanosomal infection showed higher mean PCV values, lower tick burdens and required proportionally less trypanocide treatments than corresponding cattle in group LS. The infection rate in N'Dama under high surveillance was lower in comparison with N'Dama cattle in group LS. There was no significant difference in mortality between groups within the N'Dama breed. Conversely, mortality rates were lower in crossbred and Gobra in group HS than in respective cattle in group LS. It was concluded that cattle of the three breeds suffered from trypanosomosis and that trypanosome infections affected tick susceptibility. However, N'Dama showed a superior ability to limit both the pathological effects of trypanosomosis and the level of tick infestations. Therefore, considering the cost of labour and consumable equipment required for a high surveillance, use of multi-disease resistant N'Dama cattle is recommended for the low-input traditional African farming systems in areas where trypanosomosis, ticks and tick-borne diseases are constraints to livestock production. Additional comparative investigations are needed to assess the impact of high surveillance scheme of trypanosome infection in different production systems in trypanotolerant and trypanosusceptible cattle exposed to different gradients of tsetse challenge.

Effect of low temperature storage on the haemolytic complement of cattle and sheep.

Sera from cattle and sheep stored at -70, -20 and -10 degrees C were examined for haemolytic complement at Days 0, 37, 54, 86, 133 and 245. The decline in complement followed a similar trend, both by classical pathway (CPW) and alternative pathway (APW) assay methods. Both cattle and sheep sera retained 80% of their complement activity till Day 245 at -70 degrees C whereas at -20 degrees C cattle sera had lost 67% and sheep sera 80% of the activity. At -10 degrees C the decline in complement levels was, in general, similar to -20 degrees C. The complement level of sheep sera declined more rapidly than that of cattle. For reliable results, it is suggested that sera of cattle and sheep should be assayed for complement within 4-5 months at -70 degrees C and within a month at -20 or -10 degrees C.

Haemonchus contortus with low inhibited development in sheep from the highveld of Zimbabwe.

The abomasa of sheep grazing on natural pastures in the highveld of Zimbabwe were examined for Haemonchus contortus. Of 304 abomasa, 213 (70%) harboured H. contortus. The worm burden increased during the rains to reach the peak in February-March. This was followed by a decline with low worm loads throughout the dry season. The fourth stage larvae (L4) accounted for 1-7% of the total H. contortus population, except during July and August when they comprised 22 and 54% of the worm burden, respectively. It appears that the inhibition of H. contortus is not common in the commercial farming sector where sheep are treated very frequently.

Epidemiology of Oestrus ovis infection of sheep in the highveld of Zimbabwe.

During a period of 13 months, 507 heads of sheep, obtained from an abattoir near Harare, were examined for infection with Oestrus ovis larvae. The prevalence of infection varied from 6 to 52%, the highest being in November and the lowest in April. The mean annual larval burden was 1.12. The maximum number of larvae recovered from a single head was 57 in the month of November. Two larval peaks were observed, the first and highest in November and the second in August/September. Some flies are present throughout the year, except in May. There are at least 3 generations of flies per year. The wet summer period from January to May seems to be unfavourable, as very few flies are present. There is no overwintering of first instar larvae in the heads of sheep.

Anthelmintic resistance of trichostrongylids in sheep in the highveld of Zimbabwe.

A survey was conducted on the occurrence of anthelmintic resistance of trichostrongylids on commercial sheep farms in the highveld of Zimbabwe. On ten farms the efficacy of fenbendazole, levamisole and rafoxanide was tested by a faecal egg count reduction test. Benzimidazole resistance was additionally examined using an egg hatch assay with thiabendazole. Results of the faecal egg count reduction tests and larval differentiations showed fenbendazole resistance of Haemonchus sp. on all investigated farms. Resistance of Haemonchus sp. against rafoxanide was demonstrated on all farms with reliable egg counts. Levamisole resistance of Haemonchus sp. was found on most farms but 2 farms showed an efficacy of 100%.

Development of Hyalomma lusitanicum under laboratory conditions.

At the constant temperature of 25 degrees C and relative humidity (RH) of 84%, the average pre-oviposition period of Hyalomma lusitanicum was 47 days, the oviposition lasted an average of 26 days and the total egg production was an average of 6320 per female. At 16 degrees C the females did not lay eggs at all, but those which survived for 1 year and were transferred thereafter to 25 degrees C and 84% RH laid viable eggs. At 35 degrees C, the oviposition was identical at all levels of RH tested (25, 62 and 93%). At 25 degrees C, the pre-oviposition period was shorter at 93% RH, and the number of eggs laid was fewer at 25% RH. The eggs hatched in 32-40 days, the hatching percentage being lower in batches of eggs laid at the beginning and at the end of the oviposition period. The larval and nymphal moultings were not influenced by the type of host. As the temperature increased, the pre-moult period became shorter. The engorged larvae were more sensitive to the low RH than the engorged nymphs, whose moulting percentage was always greater than 72 in all regimes. Low temperature and high humidity had a favourable effect on the survival of unfed nymphs. The female-to-male ratio was 1:2. Hyalomma lusitanicum always behaved as a 3-host tick. The adults did not engorge on rabbits. The female ticks engorged on calves weighed an average 543 mg. Ticks maintained at 25 degrees C and 84% RH and engorged on calves completed the life cycle in 138-196 days, which does not include the period of chitinization of about 30 days. More than half of this period was spent in egg laying and hatching.

Coccidia of goats in Zimbabwe.

Faecal samples from goats were collected per rectum from February 1989 to January 1990. The numbers of oocysts per gram (OPG) of faeces were determined by the McMaster technique and identification of oocysts was made on sporulation. Infection was seen throughout the year, infecting on average 89.9% of 1092 adults and 94.0% of 151 kids. OPG of less than 1000 were found in 61.2% of adults and 43.3% of kids, whereas OPG of 1000-5000 were observed in 29.0% of adults and 34.6% of kids. Two kids showed over 10(6) OPG. Twelve species of Eimeria coccidia were identified. The percentage of animals harbouring different species were: E. alijevi and E. ninakohlyakimovae, 99%; E. hirci, 83.5%; E. arloingi, 80.6%; E. caprina, 77.6%; E. aspheronica, 64.8%; E. ahsata, 63%; E. christenseni 60%; E. granulosa, 42.8%; E. pallida, 6.2%; E. intricata, 2% E. punctata, 0.3%. Two percent of goats harboured three species, 5.6% four, 9.5% five, 26.3% six, 25.7% seven, 23.7% eight, 6.3% nine, 0.6% ten and 0.3% eleven species. E. alijevi was the most predominant species, followed by E. ninakohlyakimovae, E. ahsata, E. arloingi, E. granulosa, E. caprina, E. christenseni, E. hirci, E. aspheronica and E. pallida in decreasing order. E. intricata and E. punctata never showed predominance. All the species are reported from Zimbabwe for the first time.

Small strongyle infections in donkeys from the highveld in Zimbabwe.

In total, 14 male donkeys aged between 2 and 10 years were obtained in July and November 1986, and January and April 1987 from a communal area in the Zimbabwean highveld, with the aim of studying their parasite populations. Thirteen species of small strongyles were found, numbers ranging between 3900 and 222 767 worms. The small strongyle populations consisted predominantly of adult worms in all donkeys. These results suggest that rather stable, small strongyle populations, mainly consisting of long-living adult worms, occur in Zimbabwean donkeys. The species found were, in order of abundance, Cyathostomum montgomeryi, Cylicostephanus minutus, Cylicocyclus nassatus, Cylicocyclus auriculatus, Cyathostomum tetracanthum, Cylicostephanus bidentatus, Triodontophorus nipponicus, Cyathostomum coronatum, Cylicocyclus adersi, Cyathostomum alveatum, Triodontophorus serratus, Cylicocyclus elongatus and Cylicodontophorus bicoronatus.

Strongylus vulgaris in donkeys (Equus asinus) from the highveld of Zimbabwe.

Strongylus vulgaris populations in the cranial mesenteric arteries, caecum and colon were studied in 14 donkeys obtained from a communal area of the Zimbabwean highveld during July and November, 1986, and January and April 1987. Adult parasites were present in all animals and larvae in the cranial mesenteric arteries of 12 animals. Aged animals had high worm burdens. The number of adult parasites varied from 63 to 1255 (mean 382) and of larvae in the arteries from 0 to 181 (mean 69). The mean adult worm burdens were highest in July (400) and November (488), and lowest in April (107). The mean arterial larval burden was highest in July (130) and lowest in November (21). These observations indicate that infection with S. vulgaris takes place during the rainy season resulting in the heavy arterial larval population from January onwards and the heavy adult population during the dry season.

Anthelmintic resistance in Haemonchus contortus from sheep in Malaysia.

Albendazole, oxfendazole, fenbendazole, levamisole, closantel, ivermectin and febantel were administered to sheep on four farms and their efficacy assessed by faecal egg count reduction test. High level of resistance of Haemonchus contortus was found to benzimidazoles (albendazole, oxfendazole, fenbendazole) on all farms and to febantel on the one farm where it was tested. No resistance to closantel and levamisole was observed. Resistance to ivermectin was absent on the three farms examined under this study, but has been reported on the fourth farm in earlier work. It is concluded that anthelmintic resistance to benzimidazoles and the probenzimidazole, febantel, is a serious and widespread problem in H. contortus in sheep in Malaysia.

Stomach parasites of donkeys in Morocco: habitat and interspecific interactions.

One hundred and four donkeys originating from several regions of Morocco were necropsied during 1 year. The parasites in their stomachs were counted and locations determined in the cardiac, fundic and pyloric portions. Synergistic or antagonistic interactions between parasites were assessed by a principal component analysis. Gasterophilus intestinalis was only found in the cardiac portion and G. nasalis was mostly found in the pyloric portion. Habronema were principally encountered in the pyloric portion, whereas Trichostrongylus axei was found in the fundic portion. The parasites were synergistically associated in their habitat interaction, except for T. axei on the fundic portion which was antagonistic to other parasites.

Effect of infection by Babesia spp. on the development and survival of free-living stages of Boophilus annulatus.

Oviposition, egg hatching and survival of newly-hatched larvae of Boophilus annulatus were studied in relation to infection by Babesia species and different temperature regimens. Infection of female ticks by Babesia bigemina or B. bovis had no effect on the time elapsed between engorgement and oviposition. The duration of oviposition was shorter in infected females incubated at 25 degrees C or 35 degrees C and infected females laid fewer eggs than the controls. No larvae hatched at 16 degrees C. B. bigemina-infected eggs hatched more quickly than uninfected eggs at 35 degrees C. The hatching percentage of B. bigemina-infected eggs was reduced by 50% at an incubation temperature of 25 degrees C and by 75% at 35 degrees C. At 16 degrees C there was no difference in the duration of survival of infected and non-infected larvae but at 25 degrees C and 35 degrees C the mean survival period of infected larvae was significantly lower than those of controls.

Epidemiological observations on Gasterophilus intestinalis and G. nasalis in donkeys from Morocco.

During a 24 month period, 198 donkeys were examined for Gasterophilus intestinalis and Gasterophilus nasalis larvae. Gasterophilus intestinalis was found in 97.5% and G. nasalis in 95.5% of donkeys. The third instars (L3) of both species occurred during all months of the year and so did the second instars (L2), except in April (G. nasalis) and May (G. intestinalis). Over 75% of the animals had up to 200 larvae and 1.5% had over 600 larvae. The maximum number of both L2 and L3 larvae found in any animal was 418 G. intestinalis, 433 G. nasalis and 715 of both species combined. The seasonal variation in the numbers and development status of larvae indicated that the period of greatest activity of adult flies of G. intestinalis was from August/September to November, and that of G. nasalis from May to September. Consequently, the L2 larvae in the stomachs were in peak numbers between November and January for G. intestinalis and between July and September for G. nasalis. The L3 larvae of G. intestinalis had peak numbers between December and July, and those of G. nasalis between October and March. During January-March, most of the L2 larvae of G. nasalis were trapped in polypous nodules near the pyloric end of the stomach. It is concluded that the high-risk period for infection is during late spring and autumn, leading to the heavy larval burden of Gasterophilus in the stomach of donkeys during winter.

Seasonal prevalence of gastrointestinal nematodes in communal land goats from the highveld of Zimbabwe.

On six occasions during a 1 year period, goats run on communal pastures by small-scale farmers, were purchased, housed indoors for 3 weeks and autopsied for examination of their gastrointestinal nematode burden. All of the 32 goats examined were infected. The four dominant species, Haemonchus contortus, Trichostrongylus axei, Trichostrongylus colubriformis and Oesophagostomum columbianum, were present in 88-97% of the animals. Three other nematodes, Strongyloides papillosus, Bunostomum spp. and Trichuris spp. occurred respectively in 9%, 3% and 21% of the goats. The total nematode burden was least at the end of the dry season in November and increased gradually through the rainy season to reach a peak at the end of the rains in April. The population of H. contortus followed the same trend as that of the total worm burden. Trichostrongylus colubriformis showed a peak in April and T. axei in June. The fourth stage larvae (L4) of H. contortus accounted for 0-6.8% of the total H. contortus population during most of the year except in August, when they comprised 46.1% of the burden. It can be concluded that there is a direct relationship between rainfall and intensity of infection with gastrointestinal nematodes.

Effect of temperature on development of the free-living stages of Ostertagia circumcincta.

Hatching of the eggs of Ostertagia circumcincta was studied by recovering them from faeces and incubating them in distilled water at temperatures of 4, 16, 25 and 35 degrees C. Hatching occurred at all the temperatures. The rate of hatching increased with the rise in temperature. Development of larvae to the infective third stage (L3) was studied in faecal cultures incubated at 4, 16, 25, 30, 35, 40 and 45 degrees C. Except at 4 degrees C, L3 developed at all temperatures, the optimum temperature being 16 degrees C. The rate of development of L3 increased with the rise in temperature. This resulted in a corresponding decrease in the percentage recovery of larvae.

Epidemiological observations on gastro-intestinal nematodes in communal land cattle from the highveld of Zimbabwe.

Monthly individual faecal samples from 12 calves, 12 heifers, 17 steers, 12 lactating and 10 dry cows from the communal lands near Harare in the Mashonaland province of Zimbabwe, were collected over a period of one year. Eggs per gram (epg) were determined and the infective larvae (L3) examined, following culture of pooled samples from each group of animals. The lowest counts were found in steers and the highest in calves. The lactating cows had egg counts as high or higher than the heifers. The general trend of epg was related to the rainfall pattern. The egg counts rose from December to reach a peak during April and May, followed by a decline and low levels during the dry period, from June to December. Cooperia, Haemonchus, Trichostrongylus, Oesophagostomum and Strongyloides (in calves only) were identified on coproculture. About 73-83% of L3 belonged to Cooperia and Haemonchus. The high level of infection by nematodes in the communal land cattle was thought to be due to overstocking, overgrazing and poor pasture quality.