Staying in the science stream: patterns of participation in A-level science subjects in the UK.

This paper describes patterns of participation and attainment in A-level physics, chemistry and biology from 1961 to 2009. The A-level has long been seen as an important gateway qualification for higher level study, particularly in the sciences. This long term overview examines how recruitment to these three subjects has changed in the context of numerous policies and initiatives that seek to retain more young people in the sciences. The results show that recruitment to the pure sciences has stagnated, general trends have hardly varied and the track record of government policy in influencing change is not strong. There is no evidence for increasing achievement gaps between the sexes at A-level and even national policy requiring that all young people study science up to the age of 16 appears to have had little impact on recruitment at this leve

Low Thrust Augmented Spacecraft Formation-Flying

Ballistic spacecraft formation-flying with zero thrust has great utility, but it is limited to a comparatively small set of relative trajectories. However, through the application of continuous low thrust, rich new families of formation-flying trajectories can be accessed. This new and novel problem provides a wide range of potentially useful alternatives to natural ballistic formationflying. In this paper, the standard Clohessy-Wiltshire approximation of relative spacecraft motion is used to investigate the motion of a chase spacecraft about a target spacecraft which is in a circular Earth orbit. Families of non-Keplerian relative motion are systematically explored, generating analytical representations of the relative motion trajectories and the required thrust commands for both simple static formations and more complex new forced relative orbits. It is found that the impulse, and therefore propellant, required for maintenance of such relative orbits is small, and so the concept of low thrust augmented formation-flying is deliverable in the near term with existing thruster technology

DEVELOPMENT OF A LIST OF REFERENCE CHEMICALS FOR EVALUATING ALTERNATIVE METHODS TO IN VIVO FISH BIOACCUMULATION TESTS

The aim to reduce the number of animals in experiments has highlighted the need to develop and validate nonanimal methods as alternatives to bioaccumulation studies using fish. The present study details a novel 3-tier approach to develop a list of reference compounds to aid this process. The approach was based on 1) the inclusion of relevant chemical classes supported by high-quality in vivo data for the bioconcentration factor (BCF), whole-body biotransformation rates (Kmet), and metabolism characterization for rainbow trout (Oncorhynchus mykiss) and common carp (Cyprinus carpio) (tiers I and II); and 2) the refinement to ensure a broad coverage of hydrophobicity, bioconcentration potential, molecular weight, maximum molecular diameter, whole-body biotransformation half-lives, and metabolic pathways (tier III). In silico techniques were employed to predict maximal log BCF and molecular and metabolic properties. Of the 157 compounds considered as reference compounds, 144 were supported by high-quality BCF data, 8 were supported by Kmet data, and 5 were supported by in vivo metabolism data. Additional criteria for refinement of the list of reference compounds were suggested to aid practical implementation in experimental efforts. The present list of reference compounds is anticipated to facilitate the development of alternative approaches, enhance understanding of in vivo and in vitro bioaccumulation relationships, and refine in silico BCF and metabolism predictions. Environ Toxicol Chem 2014;33:2740–2752. © 2014 SETA

Orbit period modulation for relative motion using continuous low thrust in the two-body and restricted three-body problems

This paper presents rich new families of relative orbits for spacecraft formation flight generated through the application of continuous thrust with only minimal intervention into the dynamics of the problem. Such simplicity facilitates implementation for small, low-cost spacecraft with only position state feedback, and yet permits interesting and novel relative orbits in both two- and three-body systems with potential future applications in space-based interferometry, hyperspectral sensing, and on-orbit inspection. Position feedback is used to modify the natural frequencies of the linearised relative dynamics through direct manipulation of the system eigenvalues, producing new families of stable relative orbits. Specifically, in the Hill–Clohessy–Wiltshire frame, simple adaptations of the linearised dynamics are used to produce a circular relative orbit, frequency-modulated out-of-plane motion, and a novel doubly periodic cylindrical relative trajectory for the purposes of on-orbit inspection. Within the circular restricted three-body problem, a similar minimal approach with position feedback is used to generate new families of stable, frequency-modulated relative orbits in the vicinity of a Lagrange point, culminating in the derivation of the gain requirements for synchronisation of the in-plane and out-of-plane frequencies to yield a singly periodic tilted elliptical relative orbit with potential use as a Lunar far-side communications relay. The Δv requirements for the cylindrical relative orbit and singly periodic Lagrange point orbit are analysed, and it is shown that these requirements are modest and feasible for existing low-thrust propulsion technology

Does biased gene conversion influence polymorphism in the circumsporozoite protein-encoding gene of Plasmodium vivax?

Variation between North Korean and Latin American isolates in the circumsporozoite (CS) protein encoding gene of the human malaria parasite Plasmodium vivax was studied. Polymorphic positions are confined to the central tandemly repeated sequences. Nucleotide substitutions in the tandem repeats produce variants; these substituted positions within the repeat array tend to be conserved between genes. The North Korean CS gene has a short insertion after the repeats encoding a 4-amino acid repeat (Ala-Gly-Gly-Asn) not found in the New World P. vivax genes. This sequence is found both flanking and within the tandem repeats of the CS genes of several strains of the Southeast Asian simian malaria parasite, Plasmodium cynomolgi. The intraspecific conservation of positions of variants within tandem repeat arrays and the interspecific conservation of probably ancestral repeat motifs at the end of these arrays are consistent with the occurrence of nonreciprocal genetic exchanges between the tandem repeats of these genes. However, a striking asymmetry in strand nucleotide composition within the tandem repeats of all CS genes leads us to suggest that biased correction of heteroduplexes formed during recombination plays a role in the evolution of these genes

Access to financial services by women entrepreneurs in Migori County: A Case of West Sakwa Ward

Women entrepreneurs’ access to finance services is crucial to the economic development and growth in a particular area. They need to have access to financial services to make their work easier regarding saving, investing and even insuring their businesses against disasters like the fire that can lead to many losses. Accessing financial services improves the living standards and reduces the economic dependency of individuals, families and even groups. It is a fundamental aspect towards poverty reduction and development of a particular area since it opens up employment opportunities, attracts both local and foreign investors, leads to the development of infrastructure and economic growth. The study aimed at exploring the factors affecting women entrepreneurs’ access to financial services in Migori County, West Sakwa ward. Given that their financial access restricted regarding options available, there are few m-past shops, one Equity bank agent and KCB mtaani agent, all owned by one person worsening the situation in case the owner has an emergency to attend to or is not around. Determination of the effects of financial exclusion and effects of economic illiteracy on women entrepreneurs’ access to financial services in Migori County, West Sakwa ward were the specific objectives. The study used random sampling method and 378 female entrepreneurs of Migori County, West Sakwa ward as the appropriate sample size. The study adopted descriptive design. The study was conducted in West Sakwa ward, Migori County. Data collection was done by using questionnaires; SPSS was used to analyze the data collected. The analyzed data was submitted in various forms; charts, graphs, and tables. The major findings of the study established that culture is the greatest barriers to access to financial services for the women entrepreneurs, small levels of education has had a great impact on their access to financial services, more than half of the respondents only have the primary school education

Eleven years of malaria surveillance in a Sudanese village highlights unexpected variation in individual disease susceptibility and outbreak severity

An analysis is presented of continuous data collected over 11 years based on 1 902 600 person/days of observation on the malaria experience of the people of Daraweesh, a village in eastern Sudan. Malaria transmission is hypo-endemic: the acquisition of clinical immunity with age is not as obvious as in more holo-endemic areas and malaria remained a problem in all age groups throughout the study. However, this population, who are of Fulani origin, showed a distinctly variable level of disease susceptibility. Thirty-two percent of the village never reported malaria symptoms or required malaria treatment while others experienced up to 8 clinical episodes over the 11 years of observation. Malaria incidence was clearly influenced by drought but much less obviously by rainfall. To what extent outbreak patterns are explicable in terms of anopheline factors, and to human immune factors, remains an interesting question for malaria modelling in this, and in other low transmission zones, such as the burgeoning urban areas of modern Africa