The classic problem for a logistically evolving single species population being harvested involves three parameters: rate constant, carrying capacity and harvesting rate, which are taken to be positive constants. However, in real world situations, these parameters may vary with time. This paper considers the situation where these vary on a time scale much longer than that intrinsic to the population evolution itself. Application of a multiple time scale approach gives approximate explicit closed form expressions for the changing population, that compare favorably with those generated from numerical solutions.

Given the pressing need for new antiprotozoal drugs without cross-resistance with current (failing) chemotherapy, we have explored 3-tridecylpyridinium alkaloids (3TPAs), derivatives of viscosamine, as antiparasitic agents. We have developed a simple synthetic route toward viscosamine and related cyclic and linear monomers and oligomers. Evaluation for cytotoxicity on the protozoan parasites Trypanosoma brucei, Leishmania spp., and Plasmodium falciparum revealed several 3TPAs with antiprotozoal activity in the nanomolar range. Their promising selectivity index in vitro prompted us to study the dynamics of cytotoxicity on trypanosomes in more detail. Parasites were killed relatively slowly at therapeutically safe concentrations, in a process that did not target the cell cycle. Clearance of T. brucei cultures was observed at drug concentrations of 1–10 μM.

The higher strength 7xxx aluminum alloys exhibited low resistance to stress corrosion cracking (SCC) when aged to the peak hardness (T6 temper). The overaged alloys (T7 temper) developed to enhance the SCC with loss in the strength of the alloy. Recently, retrogression and re-aging (RRA) heat treatments are used for improving the SCC behavior for alloys in T6 tempers such as 7075, 7475 and 8090. In this study, an application of retrogression and re-aging heat treatment processes are carried out to enhance toughness properties of the 7079-T651 aluminum alloy, while maintaining the higher strength of T651-temper. The results of charpy impact energy and electrical conductivity tests show a significantly increases in absorbed energy and electrical conductivity values, when the alloys are exposed to various retrogression temperatures (190, 200, 210°C) and times (20, 40, 60 minutes), and then re-aged at 160°C for 18 hours.

Steganography is the idea of embedding a secret data in different media and has become an important regulation of methods of data integration. Although the still images are generally applied in the past, is very popular in recent years for the video. The techniques of video data hiding in recent year’s emphasis on the features generated by the video compression standard, a safer method for steganography uses MPEG-4/H.264 Bit Plane Complexity Segmentation (BPCS) algorithm is proposed in this approach. The reason for choosing such a video coverage is the enormous amount of data that can be hidden in each frame of MPEG-4 video. In other words, MPEG-4 has three types of images: I-frame, B, and P frames. Unlike other techniques used to hide data, such as the LSB algorithm, PBCS can achieve better results in both mathematics expression and human vision. In this paper, data is embedded in the videos of the I-frame until the BPCS can reach high levels of integration with low distortion based on the theory that regions of low noise-levels as in a picture can be replaced by noise without a significant loss of image quality. This approach invents data hidden in high-security environments. Experimental results show the success of hidden data in the selected and extracted data from the sequence of frames and also indicate the effectiveness of the implementation plan of steganography compressed video with high security features.

Digital video steganography has attracted a great deal of research interest in the recent few years in applications. In this paper, we propose a method to embed and encrypt messages into video sequences by using steganography technique Based on the H.264 video coding standard. The system implemented in this work provides robust H.264 video compression constant, without significantly affecting the overall bit rate and quality of the video stream. The results indicate that the algorithm can be implemented steganography fast and efficiently and effect vision and peak signal to noise ratio (PSNR) of video sequences are almost unaffected after decoding.

Few studies have systematically addressed evolutionary changes in olfactory neuron assemblies, either by genetic drift or as an

adaptation to specific odor environments. We have studied the sense of olfaction in 2 congeneric scarab beetles, Pachnoda

interrupta Olivier and Pachnoda marginata Drury (Coleoptera: Scarabaeidae: Cetoniinae), which are both opportunistic

polyphages, feeding mainly on fruit and flowers. The 2 species occur in dissimilar habitats: P. interrupta is found in dry

savannah, and P. marginata in tropical parts of equatorial Africa. To study how these species may have adapted their sense of

olfaction to their odor environments, we utilized single-unit electrophysiology on olfactory sensilla with a wide selection of

food-related compounds. Despite the differences in habitat, we found that the species shared most of the physiological types

of olfactory receptor neurons (ORNs) encountered, although their proportions frequently varied between the species. The high

degree of conservation in olfaction between the species implies that a similar sensory strategy is efficient for food search in

both habitats. However, shifts in proportions of receptor neuron classes, and slight shifts in response profiles and/or presence

of some ORN classes unique to either species, may reflect adaptation to a different set of hosts.

Key words: comparative study, electrophysiology, olfaction, polyphagous herbivore, single sensillum recordings

Few studies have addressed how olfactory systems may be adapted to different odour environments. I have performed the largest study to date, comparing olfactory receptor neurons in the two congeneric species of scarab beetle, P. marginata and P. interrupta. Both species are fruit- and flower-eaters but geographically separated (equatorial versus sub-Saharan Africa, resp.). They have similar lamellate antennae covered mostly with numerous olfactory sensilla placodea (plate sensilla) and a lesser number of other types, mainly sensilla coeloconica (grooved peg), and smooth peg sensilla of unknown function. By means of single sensillum recordings with tungsten microelectrodes I screened a great number of olfactory sensilla with a large array of odorants. I compared 456 sensilla placodea, containing 212 responding cells, over the whole antennae in both species. The olfactory systems of these two species displayed an amazing degree of conservation, with 20 identified olfactory neuron classes, all except two of which were found in both species with no detectable difference in response profiles. The exceptions were two olfactory receptor neuron classes: methyl benzoate and gamma-nonalactone, which were only found in Pachnoda marginata. In general, the two species showed an almost total overlap in their receptor neuron assemblies. One aim of the study was also to test whether the arrangement of neurons within sensilla was conserved between the species, but this could not be tested as very few combinations of characterized neurons were encountered during the study.

Key words: olfaction, electrophysiology, scarab beetles, Pachnoda marginata, Pachnoda interrupta, single sensillum recording, olfactory receptor neurons

The sorghum chafer, Pachnoda interrupta Olivier

(Coleoptera: Scarabaeidae: Cetoniinae), is a key pest on

sorghum, Sorghum bicolor (L.) Moench (Poaceae), in

Ethiopia. At present there is a lack of efficient control

methods. Trapping shows promise for reduction of the pest

population, but would benefit from the development of

attractive lures. To find attractants that could be used for

control of P. interrupta, either by mass trapping or by

monitoring as part of integrated pest management, we

screened headspace collections of sorghum and the highly

attractive weed Abutilon figarianum Webb (Malvaceae) for

antennal activity using gas chromatograph-coupled electroantennographic

detection (GC-EAD). Compounds active in

GC-EAD were identified by combined gas chromatography

and mass spectrometry (GC-MS).

Information Communication Technologies (ICTs) provide an opportunity to meet the growing needs of rural areas. Many of the key features of ICT can be used to provide information and the requirements of people in rural areas. The digital divide considered is an important problem that countries face and it is much more complex than simply building out telecommunication networks and infrastructure. The divide is the result of a wide range of social factors, including but not limited to economy factors, education, literacy. Telecommunication infrastructure alone will not guarantee that users will be able to access and take advantage of services on the network. The paper begins with an introduction to the digital divide, and thus to highlight several successful initiatives provided by educational institutions and governmental organizations in Libya in the adoption of ICT. Finally, the paper provides some of the solutions proposed to reduce this divide.