Tree species diversity under pastoral and farming systems in Kilosa District, Tanzania

Loss of tree diversity through improper land use practices such as overgrazing and poor farming practices in tropical areas and other natural ecosystems is one of today's most worrying environmental problems. This study was conducted to assess the impact of farming and pastoralism on tree species diversity in two forests each owned and managed by pastoral and farming communities in Kilosa District. Household survey solicited information on perceptions of local communities on drivers that influenced tree stocking and diversity of their forests. A forest inventory was conducted involving twenty circular in each system plots laid along two transects. In each plot, trees and shrubs with DBH > 5 cm were measured for DBH and height. A total of 48 different species were recorded out of which 75%were tree species and 25% shrubs species. The forest under pastoral system had a Shannon - Wiener Index (H’) of 3.13 as opposed to farming system with an index of 2.05. Average stocking for the forest under pastoral system was 235 stem ha-1, whereas that of farming system was 209 stem ha-1. Basal areas of 13m2ha-1 and 6m2 ha-l were recorded for forests under pastoral and farming systems respectively. Standing volume showed the same tendency where 216m3ha-1 was recorded from the forest under pastoral system as opposed to 100.12 m3ha-1 from the other forest. The high loss of species diversity and stocks particularly in the forest under farming system were attributed to anthropogenic disturbances including cutting trees for farm expansion, charcoal making and house construction. Although the assessment on the community perception on the loss of tree diversity in the area showed conflicting interests between the two societies each blaming activities of each community as major causes of forest degradation. This calls for more enforcement of rules and regulations and tree planting in degraded areas predominantly in the farming communities. The study further revealed that the existing tensions over land resource ownership between the two communities of farmers and pastoralists may be contributing factors of unsustainable use of tree species and other forest resources. It is recommended that interventions should be done to settle conflicts over land resource ownership and management between the two villages as well control proliferation and dominance of Acacia nilotica as a way to improve pasture and improve species diversity in the area. Key words: Tree stocking - rules and regulations - anthropogenic disturbance

Productive Efficiency of Small Scale Sawmilling Industries in Mufindi District, Tanzania

This study was carried out to examine the productive efficiency of small-scale sawmills in Mufindi District. The specific objectives were: (i) to assess the relative efficiency of small-scale sawmills in Mufindi, (ii) to identify factors for variation in the small scale sawmill’s relative efficiency and (iii) to provide policy recommendations for efficiency improvement in utilization of forest resources. A structured questionnaire was used to collect data from 80 small-scale sawmills in Mufindi District. Data were analysed using descriptive as well as quantitative methods. Technical, scale and allocative efficiency score of sawmills were computed using data envelopment analysis programme developed by Coelli. Censored regression models were estimated to identify factors for inefficiency of smallscale sawmills. Results showed a mean technical efficiency of 84% (CRS model) and 92% (VRS model), allocative efficiency of 84% (CRS model) and 89% (VRS model) and cost efficiency of 70% (CRS model) and 81 % (VRS model). Furthermore, results from the censored regression model revealed that Owners/manager’s education, experience, the size of the sawmill timber yard and partnership ownership had positive effects on sawmill’s efficiency while machine age had a negative effect on sawmill’s efficiency. Recommendations for enhancing small-scale sawmills production efficiency are: Strengthening extension services to increase sawmilling experience, and insistence on partnership ownership of sawmills. Since mill size positively enhanced sawmills’ relative efficiency, anincrease of the size of mills must receive priority. Squeezing sawmill area as a result of increased number of sawmills leads to inefficiency. Lastly but not least, the use of sawmilling by products particularly chips, saw dusts and slabs should be promoted as it is a way of increasing efficiency in sawmilling

Comparison of the subspecies of Sclerocarya birreaby sex and environment

A comparison of stand parameters between wild and on farm populations of the 3 subspecies of Sclerocarya birrea was done. Using plot-less sampling technique, 100 trees from six populations were measured for diameter at breast height (Dbh), branching height, height and crown diameter. There was significant (p<0.001) difference in Dbh, branching height and tree height between the three subspecies and between the populations. For all subspecies and populations, male trees were taller than female trees although the difference was not significant. While S. birrea subspecies birrea and caffra had trees in the wild taller than those on farm, the opposite was observed among trees of S. birrea subspecies multifoliolata. The mean crown sizes of male and female trees differed significantly (p<0.001) between the three subspecies and within a population. There were positive correlations (p> 50) between altitude and tree diameter, branching height, tree-height and crown diameter. Tree size was not found to increase due to farmers’ selection pressure and farming practices in Tanzania, probably because they are not retained purposely for their fruits as is the case in other countries in southern Africa.Key words: Sclerocarya birrea, Tanzania, population, habitat, gende

Asymmetric triplex metallohelices with high and selective activity against cancer cells

Small cationic amphiphilic α-helical peptides are emerging as agents for the treatment of cancer and infection, but they are costly and display unfavourable pharmacokinetics. Helical coordination complexes may offer a three-dimensional scaffold for the synthesis of mimetic architectures. However, the high symmetry and modest functionality of current systems offer little scope to tailor the structure to interact with specific biomolecular targets, or to create libraries for phenotypic screens. Here, we report the highly stereoselective asymmetric self-assembly of very stable, functionalized metallohelices. Their anti-parallel head-to-head-to-tail ‘triplex’ strand arrangement creates an amphipathic functional topology akin to that of the active sub-units of, for example, host-defence peptides and ​p53. The metallohelices display high, structure-dependent toxicity to the human colon carcinoma cell-line HCT116 ​p53++, causing dramatic changes in the cell cycle without DNA damage. They have lower toxicity to human breast adenocarcinoma cells (MDA-MB-468) and, most remarkably, they show no significant toxicity to the bacteria methicillin-resistant Staphylococcus aureus and Escherichia coli. At a glanc

Bounds and Decays of New Heavy Vector-like Top Partners

We study the phenomenology of new heavy vector-like fermions that couple to the third generation quarks via Yukawa interactions, covering all the allowed representations under the standard model gauge groups. We first review tree and loop level bounds on these states. We then discuss tree level decays and loop-induced decays to photon or gluon plus top. The main decays at tree level are to W b and/or Z and Higgs plus top via the new Yukawa couplings. The radiative loop decays turn out to be quite close to the naive estimate: in all cases, in the allowed perturbative parameter space, the branching ratios are mildly sensitive on the new Yukawa couplings and small. We therefore conclude that the new states can be observed at the LHC and that the tree level decays can allow to distinguish the different representations. Moreover, the observation of the radiative decays at the LHC would suggest a large Yukawa coupling in the non-perturbative regime.Comment: 32 pages, 2 tables, 10 figure

An Agent-based Collective Model to Simulate Peer Pressure Effect on Energy Consumption

This paper presents a novel model for simulating peer pressure effect on energy awareness and consumption of families. The model is built on two well-established theories of human behaviour to obtain realistic peer effect: the collective behaviour theory and the theory of cognitive dissonance. These theories are implemented in a collective agentbased model that produces fine-grained behaviour and consumption data based on social parameters. The model enables the application of different energy efficiency interventions which aim to obtain more aware occupants and achieve more energy saving. The presented experiments show that the implemented model reflects the human behaviour theories. They also provide examples of how the model can be used as an analytical tool to interpret the effect of energy interventions in the given social parameters and decide the optimal intervention needed in different cases

Enhancement of apixaban's solubility and dissolution rate by inclusion complex (β-cyclodextrin and hydroxypropyl β-cyclo¬dextrin) and computational calculation of their inclusion complexes

Background and Purpose: Apixaban (AP) is a factor X inhibitor, an orally active drug that inhibits blood coagulation for better prevention of venous thromboembolism. It has poor solubility, dissolution rate and low bioavailability. The aim of this study was to improve the aqueous solubility and dissolution rate of oral AP as a step to enhance its bioavailability by preparing it as an inclusion complex with beta- and hydroxy propyl beta-cyclodextrin. Experimental Approach: A simple, rapid method of analysis of AP was developed using ultraviolet spectrophotometry (UV) and partially validated in terms of linearity, precision and accuracy, recovery, and robustness. AP was prepared as a complex with beta cyclodextrin (βCD) and hydroxy propyl beta cyclodextrin (HPβCD) in weight ratios 1:1, 1:2, and 1:3 by kneading, solvent evaporation and spray drying methods and characterized by Fourier transfer infra-red (FTIR), differential scanning calorimetry (DSC), and percent drug content in each of the prepared complex. Using the computer simulation, the interactions of AP with βCD and HPβCD were investigated. Key Results: The phase solubility study showed that the solubility of AP was greatly enhanced from 54×10-3 mmol /L to 66 mmol/L using HPβCD with acceptable stability constant. Computer docking supports the formation of a stable 1:1 complex between AP and CD’s. The dissolution test results showed that the complex gave a significantly higher percentage of drug release (95%) over one hour compared to the free AP (60%) (p<0.05). Conclusion: AP- HPβCD complex in the ratio of 1:2 (w/w) can significantly improve the solubility and in vitro dissolution rate of AP

Rare Z-decay into light CP-odd Higgs bosons: a comparative study in different new physics models

Various new physics models predict a light CP-odd Higgs boson (labeled as $a$) and open up new decay modes for Z-boson, such as $Z \to \bar{f} f a$, $Z\to a\gamma$ and $Z\to aaa$, which could be explored at the GigaZ option of the ILC. In this work we investigate these rare decays in several new physics models, namely the type-II two Higgs doublet model (type-II 2HDM), the lepton-specific two Higgs doublet model (L2HDM), the nearly minimal supersymetric standard model (nMSSM) and the next-to-minimal supersymmetric standard model (NMSSM). We find that in the parameter space allowed by current experiments, the branching ratios can reach $10^{-4}$ for $Z \to \bar{f} f a$ ($f=b,\tau$), $10^{-9}$ for $Z\to a\gamma$ and $10^{-3}$ for $Z\to aaa$, which implies that the decays $Z \to \bar{f} f a$ and $Z \to a a a$ may be accessible at the GigaZ option. Moreover, since different models predict different patterns of the branching ratios, the measurement of these rare decays at the GigaZ may be utilized to distinguish the models.Comment: Version in JHEP (discussions added, errors corrected

Ferritins: furnishing proteins with iron

Ferritins are a superfamily of iron oxidation, storage and mineralization proteins found throughout the animal, plant, and microbial kingdoms. The majority of ferritins consist of 24 subunits that individually fold into 4-α-helix bundles and assemble in a highly symmetric manner to form an approximately spherical protein coat around a central cavity into which an iron-containing mineral can be formed. Channels through the coat at inter-subunit contact points facilitate passage of iron ions to and from the central cavity, and intrasubunit catalytic sites, called ferroxidase centers, drive Fe2+ oxidation and O2 reduction. Though the different members of the superfamily share a common structure, there is often little amino acid sequence identity between them. Even where there is a high degree of sequence identity between two ferritins there can be major differences in how the proteins handle iron. In this review we describe some of the important structural features of ferritins and their mineralized iron cores and examine in detail how three selected ferritins oxidise Fe2+ in order to explore the mechanistic variations that exist amongst ferritins. We suggest that the mechanistic differences reflect differing evolutionary pressures on amino acid sequences, and that these differing pressures are a consequence of different primary functions for different ferritins