Parallel asynchronous systems and image processing algorithms

A new hardware approach to implementation of image processing algorithms is described. The approach is based on silicon devices which would permit an independent analog processing channel to be dedicated to evey pixel. A laminar architecture consisting of a stack of planar arrays of the device would form a two-dimensional array processor with a 2-D array of inputs located directly behind a focal plane detector array. A 2-D image data stream would propagate in neuronlike asynchronous pulse coded form through the laminar processor. Such systems would integrate image acquisition and image processing. Acquisition and processing would be performed concurrently as in natural vision systems. The research is aimed at implementation of algorithms, such as the intensity dependent summation algorithm and pyramid processing structures, which are motivated by the operation of natural vision systems. Implementation of natural vision algorithms would benefit from the use of neuronlike information coding and the laminar, 2-D parallel, vision system type architecture. Besides providing a neural network framework for implementation of natural vision algorithms, a 2-D parallel approach could eliminate the serial bottleneck of conventional processing systems. Conversion to serial format would occur only after raw intensity data has been substantially processed. An interesting challenge arises from the fact that the mathematical formulation of natural vision algorithms does not specify the means of implementation, so that hardware implementation poses intriguing questions involving vision science

Parallel asynchronous hardware implementation of image processing algorithms

Research is being carried out on hardware for a new approach to focal plane processing. The hardware involves silicon injection mode devices. These devices provide a natural basis for parallel asynchronous focal plane image preprocessing. The simplicity and novel properties of the devices would permit an independent analog processing channel to be dedicated to every pixel. A laminar architecture built from arrays of the devices would form a two-dimensional (2-D) array processor with a 2-D array of inputs located directly behind a focal plane detector array. A 2-D image data stream would propagate in neuron-like asynchronous pulse-coded form through the laminar processor. No multiplexing, digitization, or serial processing would occur in the preprocessing state. High performance is expected, based on pulse coding of input currents down to one picoampere with noise referred to input of about 10 femtoamperes. Linear pulse coding has been observed for input currents ranging up to seven orders of magnitude. Low power requirements suggest utility in space and in conjunction with very large arrays. Very low dark current and multispectral capability are possible because of hardware compatibility with the cryogenic environment of high performance detector arrays. The aforementioned hardware development effort is aimed at systems which would integrate image acquisition and image processing

FOREST REGENERATION IMMEDIATELY, AFTER TRADITIONAL SHIFTING CULTIVATION IN THE NORTHERN DRY ZONE OF SRI LANKA

The forest regeneration immediately after traditional shifting cultivation wasstudied in an abandoned shifting cultivation field at Sigiriya in the northern dryzone of Sri Lanka. Biotic and abiotic factors that are responsible for the forestregeneration process were also identified.The vegetation and the soil seed bank (both surface and sub-surface) wereenumerated before clearing the land for shifting cultivation and one month afterthe abandonment. In addition, the soil seed bank was investigated 15 hours afterburning of the land (i.e. a 12-15 year old secondary forest) prior to cultivation.Some physical environmental parameters were recorded after the abandonment ofthe land.Regeneration after traditional shifting cultivation was mainly by roots and stembases of woody plants, which existed before cultivation. Thus, many early andlate survivalspecies were regenerated. The ground of recently abandoned shiftingcultivation land was very open (% canopy opennes = 69.39±4.80 and this resultsin to have high soil temperatures and low soil moisture contents. Wind dispersedseeds of grass and agricultural weed species frequently disperse into the burntland. Few seeds of some pioneer species are capable of withstanding fire and mayoccur as a soil seed store. However, seeds in the soil seed bank may not involvein forest regeneration at this early stage. Underlying reasons for that are alsodiscussed.

FACTORS AFFECTING THE VEGETATION SUCCESSION OF MOIST·DECIDUOUS FORESTS AT SIGIRIYA SANCTUAR~SRILANKA

This study examines the vegetation succession of moist deciduous forests at the Sigiriyasanctuary and some factors affecting for this. Thirty eight 20x20m2 experimental plotswere established in sites ranging in disturbance history from areas abandoned for onemonth after swidden farming to forests not known to have been recently disturbed. Thevegetation was enumerated while the canopy openness, soil moisture and soil temperaturewere measured. Seed rain was monitored while the soil seed bank was enumerated threetimes over a year in four month intervals. Seedling bank was also enumerated in lx2m2quadrat in each experimental plot. Seed predation was examined by keeping seeds ofChloroxylon swietenia seeds in the experimental plots and by continuous observations.Succession appears to be a process of progressive change in species dominance and lossof less shade-tolerant subordinates rather than accumulation of new colonists. Both seedrain and soil seed bank in all these young successional forests contain many agriculturalweed species but the density of seeds of climax species is negligible. Consequently, theseedling bank is very poor and contains many agricultural weed and light demandingshrub species. The soil temperature in young successional forests is higher while the soilmoisture is lower than the older successional or high forests. After 18-20 years, the treesare released and shade-out light demanding species. This results in the death of most ofthe light demanding shrubs and as a consequence, root competition is reduced and morespace is available for the establishment of new immigrant climax forest species. The seedrain, soil seed bank and the seedling bank of 20-25 year old forests contain some seeds ofclimax forest species.High forests contain many climax forest tree ,IUd shrub species but seeds a.id seedlings ofvaluable timber tree species are rare in them. High seed predation is one reason for thissituation. Seedling bank is very fragmented and mostly contains individuals of climaxforest shrub species.It seems that the studied moist deciduous forests are somewhat degraded and thevegetation succession after a large scale disturbance is a slow process. Therefore,protection and rehabilitation of these forests are vital activities for their perpetuity.

PHYSIOGNOMY AND NATURAL REGENERATION OF DRY DECIDUOUS FORESTS AT SIGIRIYA, SRI LANKA

Although, poor natural regeneration of tropical dry forest has been observed in Sri Lanka.India. Africa and in Latin America. the factors affecting this have not been well studied.In this paper. the physiognomy of dry deciduous forests at Sigiriya in the northern dry zoneof Sri Lanka and some major factors which affect their natural regeneration wereestimated.The vegetation was enumerated in six 20x20m experimental plots. The diameter 01' trees25cm at breast height (dhh) was measured. Seed rain was detected hy collecting seedsusing wooden trays. allowing them to he germinated and enumerating the germinants overa period of eleven months. The seed bank was examined by collecting ten soil samplesfrom each plot three times within a year. Seedlings were recorded in 2x2m quadrates ineach plot and their growth and survival was recorded throughout an year. Soiltemperature, soil moisture and the canopy openness were also detected.The species composition and dominant species were identified for dry deciduous forest inthe arca. The beta diversity of forests is high implying the importance of conserving largeareas of dry forests. Seasonality of seed production. seed predation. lack of a persistentseed bank, unfavourahle environmental factors arc found to be affecting the regeneration ofdry deciduous forest. Possibilities of sustainable timber production in dry deciduous forestand the participation of local people in forest management arc also discussed.

A Review on the Comparative Analysis of Synthetic Insect Repellents and Essential Oil Based Sustained-release Insect Repellent Formulations

The necessity of developing insect repellents with highly effective sustained release properties has attracted more attention due to the vast spread of arthropod-borne diseases such as dengue and malaria, which must be controlled with proper measures, and also due to the devastating damage caused by severe infestation of insect pests on crops and stored food. Natural and synthetic insect repellents are used against insect vectors and insect pests. Topical insect repellent formulations should be less toxic, less irritant, and less skin permeable. Irrespective of the type and form of the repellent, the mechanism of action depends on the formation of a vapour barrier/ odour barrier, that would deviate the insect from reaching the host. Synthetic insect repellents are highly efficient but due to their high toxicity, degradation resistance, and bio accumulation, they raise environmental and ecological issues. Due to the adverse effects caused by synthetic insect repellents, more attention is given to insect repellents consisting of natural products.Essential oils are among the widely used natural insect repellents available due to their biocompatibility and non-toxicity. High volatility of essential oils is the major problem that hampers the application of essential oils as insect repellent agents. The high volatility that reduces the length of application, and its activity can be successfully addressed by the formulation of slow-release insect repellent composites by incorporating essential oils into adsorbing or encapsulating matrices. Zeolites, montmorillonite, β-cyclodextrin, polymeric materials, and electrospun nanomaterials are commonly used to develop slow-release formulations with essential oils. Among these, polymeric microcapsules are the most extensively studied and developed slow-release insect repellent systems that are based on natural and synthetic active compounds. Key words: Formulation, Insects, Microcapsules, Repellents, Zeolit

Heterogeneous Diffusion in Highly Supercooled Liquids

The diffusivity of tagged particles is demonstrated to be very heterogeneous on time scales comparable to or shorter than the $\alpha$ relaxation time $\tau_{\alpha}$ ($\cong$ the stress relaxation time) in a highly supercooled liquid via 3D molecular dynamics simulation. The particle motions in the relatively active regions dominantly contribute to the mean square displacement, giving rise to a diffusion constant systematically larger than the Einstein-Stokes value. The van Hove self-correlation function $G_s(r,t)$ is shown to have a long distance tail which can be scaled in terms of $r/t^{1/2}$ for t \ls 3\tau_{\alpha}. Its presence indicates heterogeneous diffusion in the active regions. However, the diffusion process eventually becomes homogeneous on time scales longer than the life time of the heterogeneity structure ($\sim 3 \tau_{\alpha}$).Comment: 4 pages, 5 figure

SEED ECOLOGY OF SOME SELECTED DRY FOREST SPECIES OF SRI LANKA

This study examines seed ecology of ten native dry zone forest species: Manilkarahexandra, Drypetes sepiaria, Salvadora persica, Bauhinia racemosa, Cassia fistula,Cassia siamea, Schlechera oleosa, Oroxylum indicum, Randia uliginosa, Dichrostachyscineria and in one alien invasive species: Prosopis juliflora.Seed samples were collected from the dry zone of Sri Lanka (in Anuradhapura,Polonnaruwa, Monaragala and Hambanthota districts). Morphology (colour, width,length of seeds) and the weight of 60 seeds per each species were recorded in threereplicates. Viability of seeds was tested using standard TIC test while the percentagegermination of seeds was recorded in moist petridishes laid according to RandomizeComplete Block Design. Rate of water absorption of seeds and seed coat widths were alsomeasured, while the presence of water-soluble growth inhibitors were examined througha bioassay using Brasica juncea seeds. Hot water treatments, Hot air treatments,Gibberalic acid treatments, Manual scarification and combinations of above treatmentswere tested to break the seed dormancy of these species. Seed and plant characteristicswere observed to determine the ecological state (Climax or Pioneer) of study species.Seed predation and dispersal mechanisms were observed during field visits.P.jutiflora and 0. indicum seeds are recalcitrant, while the remaining species showedseed dormancy. D.cineria Cfistula, Csiamea and B.racemosa seeds appeared to bedormant due to its water impermeable seed coat and the dormancy can be overcome bymanual-scarification. S.persica seeds contain underdeveloped embryo and hot watertreatment (at 45°C for 5 days) was found to be the best treatment to break the seeddormancy. D.sepiaria, S.oleosa and R.uliginosa seeds seem to be dormant due to thepresence Of a growth inhibitor and the hard seed coat. Manual scarification together withGibberalic acid (4000ppm) treatment was found to be suitable to break the seed dormancyof the species. M.hexandra seeds too have an undeveloped embryos and hard seed coats,which may cause seed dormancy, but seed germination can be improved by hot watertreatment (at 85°C for 15minutes) fallowed by manual scarification. o'indicum andR. uliginosa can be described as Pioneer species. Other 8 natural forest species can bedescribed as climax species, which mainly dispersed by animals. High seed predationcan be observed in these species. Especially insects including termites and several larvaeof insects attack the seeds of tbese species.