Differentiation status of limbal epithelial cells cultured on intact and denuded amniotic membrane before and after air-lifting

We have investigated differences in bovine limbal epithelial cell differentiation when expanded upon intact (amniotic epithelial cells and basement membrane remaining) and denuded human amniotic membrane, a commonly used substrate in ophthalmic surgery for corneal stem cell transplantation. Ex vivo expansion of the epithelial cells, in supplemented media, continued for 2 weeks followed by 1 week under ‘air-lifting’ conditions. Before and after air-lifting the differentiated (K3/K12 positive) and undifferentiated (K14 positive) cells were quantified by immunohistochemistry, Western blotting and quantitative PCR. Limbal epithelial cells expanded upon amniotic membrane formed 4-6 stratified layers, both on intact and denuded amniotic membrane. On denuded amniotic membrane the proportion of differentiated cells remained unaltered following airlifting. Within cells grown on intact amniotic membrane, however, the number of differentiated cells increased significantly following air-lifting. These results have important implications for both basic and clinical research. Firstly, they show that bovine limbal epithelia can be used as an alternative source of cells for basic research investigating ex vivo limbal stem cells expansion. Secondly, these findings serve as a warning to clinicians that the affect of amniotic membrane on transplantable cells is not fully understood; the use of intact or denuded amniotic membrane can produce different results in terms of the amount of differentiation, once cells are exposed to the air.

Restrictions to the adaptation of influenza A virus H5 hemagglutinin to the human host

The binding specificities of a panel of avian influenza virus subtype H5 hemagglutinin (RA) proteins bearing mutations at key residues in the receptor binding site were investigated. The results demonstrate that two simultaneous mutations in the receptor binding site resulted in H5 RA binding in a pattern similar to that shown by human viruses. Coexpression of the ion channel protein, M2, from most avian and human strains tested protected H5 RA conformation during trafficking, indicating that no genetic barrier to the reassortment of the H5 surface antigen gene with internal genes of human viruses existed at this level.

A spatial–temporal analysis of the impact of access restrictions on forest landscapes and household welfare in Tanzania

This paper explores the impact of the re-introduction of access restrictions to forests in Tanzania, through participatory forest management (PFM), that have excluded villagers from forests to which they have traditionally, albeit illegally, had access to collect non-timber forest products (NTFPs). Motivated by our fieldwork, and using a spatial–temporal model, we focus on the paths of forest degradation and regeneration and villagers' utility before and after an access restriction is introduced. Our paper illustrates a number of key points for policy makers. First, the benefits of forest conservation tend to be greatest in the first few periods after an access restriction is introduced, after which the overall forest quality often declines. Second, villagers may displace their NTFP collection into more distant forests that may have been completely protected by distance alone before access to a closer forest was restricted. Third, permitting villagers to collect limited amounts of NTFPs for a fee, or alternatively fining villagers caught collecting illegally from the protected forest, and returning the fee or fine revenue to the villagers, can improve both forest quality and villagers' livelihoods.

Simulating the interannual variability of major dust storms on Mars using variable lifting thresholds

The redistribution of a finite amount of martian surface dust during global dust storms and in the intervening periods has been modelled in a dust lifting version of the UK Mars General Circulation Model. When using a constant, uniform threshold in the model’s wind stress lifting parameterisation and assuming an unlimited supply of surface dust, multiannual simulations displayed some variability in dust lifting activity from year to year, arising from internal variability manifested in surface wind stress, but dust storms were limited in size and formed within a relatively short seasonal window. Lifting thresholds were then allowed to vary at each model gridpoint, dependent on the rates of emission or deposition of dust. This enhanced interannual variability in dust storm magnitude and timing, such that model storms covered most of the observed ranges in size and initiation date within a single multiannual simulation. Peak storm magnitude in a given year was primarily determined by the availability of surface dust at a number of key sites in the southern hemisphere. The observed global dust storm (GDS) frequency of roughly one in every 3 years was approximately reproduced, but the model failed to generate these GDSs spontaneously in the southern hemisphere, where they have typically been observed to initiate. After several years of simulation, the surface threshold field—a proxy for net change in surface dust density—showed good qualitative agreement with the observed pattern of martian surface dust cover. The model produced a net northward cross-equatorial dust mass flux, which necessitated the addition of an artificial threshold decrease rate in order to allow the continued generation of dust storms over the course of a multiannual simulation. At standard model resolution, for the southward mass flux due to cross-equatorial flushing storms to offset the northward flux due to GDSs on a timescale of ∼3 years would require an increase in the former by a factor of 3–4. Results at higher model resolution and uncertainties in dust vertical profiles mean that quasi-periodic redistribution of dust on such a timescale nevertheless appears to be a plausible explanation for the observed GDS frequency.

An assessment of the impact of local processes on dust lifting in martian climate models

Simulation of the lifting of dust from the planetary surface is of substantially greater importance on Mars than on Earth, due to the fundamental role that atmospheric dust plays in the former’s climate, yet the dust emission parameterisations used to date in martian global climate models (MGCMs) lag, understandably, behind their terrestrial counterparts in terms of sophistication. Recent developments in estimating surface roughness length over all martian terrains and in modelling atmospheric circulations at regional to local scales (less than O(100 km)) presents an opportunity to formulate an improved wind stress lifting parameterisation. We have upgraded the conventional scheme by including the spatially varying roughness length in the lifting parameterisation in a fully consistent manner (thereby correcting a possible underestimation of the true threshold level for wind stress lifting), and used a modification to account for deviations from neutral stability in the surface layer. Following these improvements, it is found that wind speeds at typical MGCM resolution never reach the lifting threshold at most gridpoints: winds fall particularly short in the southern midlatitudes, where mean roughness is large. Sub-grid scale variability, manifested in both the near-surface wind field and the surface roughness, is then considered, and is found to be a crucial means of bridging the gap between model winds and thresholds. Both forms of small-scale variability contribute to the formation of dust emission ‘hotspots’: areas within the model gridbox with particularly favourable conditions for lifting, namely a smooth surface combined with strong near-surface gusts. Such small-scale emission could in fact be particularly influential on Mars, due both to the intense positive radiative feedbacks that can drive storm growth and a strong hysteresis effect on saltation. By modelling this variability, dust lifting is predicted at the locations at which dust storms are frequently observed, including the flushing storm sources of Chryse and Utopia, and southern midlatitude areas from which larger storms tend to initiate, such as Hellas and Solis Planum. The seasonal cycle of emission, which includes a double-peaked structure in northern autumn and winter, also appears realistic. Significant increases to lifting rates are produced for any sensible choices of parameters controlling the sub-grid distributions used, but results are sensitive to the smallest scale of variability considered, which high-resolution modelling suggests should be O(1 km) or less. Use of such models in future will permit the use of a diagnosed (rather than prescribed) variable gustiness intensity, which should further enhance dust lifting in the southern hemisphere in particular.

Contractual restrictions on lawful use of information: sole-source databases protected by the back door?

This article is concerned with the risks associated with the monopolisation of information that is available from a single source only. Although there is a longstanding consensus that sole-source databases should not receive protection under the EU Database Directive, and there are legislative provisions to ensure that lawful users have access to a database’s contents, Ryanair v PR Aviation challenges this assumption by affirming that the use of non-protected databases can be restricted by contract. Owners of non-protected databases can contractually exclude lawful users from taking the benefit of statutorily permitted uses, because such databases are not covered from the legislation that declares this kind of contract null and void. We argue that this judgment is not consistent with the legislative history and can have a profound impact on the functioning of the digital single market, where new information services, such as meta-search engines or price-comparison websites, base their operation on the systematic extraction and re-utilisation of materials available from online sources. This is an issue that the Commission should address in a forthcoming evaluation of the Database Directive.

Long-run restrictions and survey forecasts of output, consumption and investment

We consider the extent to which long-horizon survey forecasts of consumption, investment and output growth are consistent with theory-based steady-state values, and whether imposing these restrictions on long-horizon forecasts will enhance their accuracy. The restrictions we impose are consistent with a two-sector model in which the variables grow at different rates in steady state. The restrictions are imposed by exponential-tilting of simple auxiliary forecast densities. We show that imposing the consumption-output restriction yields modest improvements in the long-horizon output growth forecasts, and larger improvements in the forecasts of the cointegrating combination of consumption and output: the transformation of the data on which accuracy is assessed plays an important role.

AIDS, mobility and commercial sex in Ethiopia: Implications for policy

Since the emergence of the AIDS pandemic in sub-Saharan Africa, male mobility has been highlighted as one of the reasons for the spread of the disease with men employing the services of commercial sex workers while away from home. However, sex workers' mobility and the implications of this for their access to prevention services, has largely been ignored. This paper, based on multi-method qualitative research with 60 young sex workers in two Ethiopian towns, reveals that sex workers are highly mobile, moving in order to attract a wider or different client base, for adventure and to conceal illnesses which might be associated with AIDS. In addition, sex workers are affected by restrictions on their movements, with girls working in bars and red-light areas having little free time to access projects. This paper advocates that policy approaches need to take account of this mobility in three ways: first, by exploring ways for girls to access information and maintain contact with support structures while moving between places of work; second, by building the capacity of sex workers to take greater control over decision-making in their day-to-day lives and third, by developing outreach strategies for taking services into bars and red-light areas.

Orographic precipitation in the tropics: large-eddy simulations and theory

Recent radar and rain-gauge observations from the island of Dominica, which lies in the eastern Caribbean sea at 15 N, show a strong orographic enhancement of trade-wind precipitation. The mechanisms behind this enhancement are investigated using idealized large-eddy simulations with a realistic representation of the shallow trade-wind cumuli over the open ocean upstream of the island. The dominant mechanism is found to be the rapid growth of convection by the bulk lifting of the inhomogenous impinging flow. When rapidly lifted by the terrain, existing clouds and other moist parcels gain buoyancy relative to rising dry air because of their different adiabatic lapse rates. The resulting energetic, closely-packed convection forms precipitation readily and brings frequent heavy showers to the high terrain. Despite this strong precipitation enhancement, only a small fraction (1%) of the impinging moisture flux is lost over the island. However, an extensive rain shadow forms to the lee of Dominica due to the convective stabilization, forced descent, and wave breaking. A linear model is developed to explain the convective enhancement over the steep terrain.

Orographic precipitation in the tropics: experiments in Dominica

The “natural laboratory” of mountainous Dominica (15°N) in the trade wind belt is used to study the physics of tropical orographic precipitation in its purest form, unforced by weather disturbances or by the diurnal cycle of solar heating. A cross-island line of rain gauges and 5-min radar scans from Guadeloupe reveal a large annual precipitation at high elevation (7 m yr^{−1}) and a large orographic enhancement factor (2 to 8) caused primarily by repetitive convective triggering over the windward slope. The triggering is caused by terrain-forced lifting of the conditionally unstable trade wind cloud layer. Ambient humidity fluctuations associated with open-ocean convection may play a key role. The convection transports moisture upward and causes frequent brief showers on the hilltops. The drying ratio of the full air column from precipitation is less than 1% whereas the surface air dries by about 17% from the east coast to the mountain top. On the lee side, a plunging trade wind inversion and reduced instability destroys convective clouds and creates an oceanic rain shadow.

Official warnings on thromboembolism risk with oral contraceptives fail to inform users adequately

Following the 1995 “pill scare” relating to the risk of venous thrombosis from taking second- or third-generation oral contraceptives, the Committee on Safety of Medicines (CSM) withdrew their earlier recommended restrictions on the use of third-generation pills and published recommended wording to be used in patient information leaflets. However, the effectiveness of this wording has not been tested. An empirical study (with 186 pill users, past users, and non-users) was conducted to assess understanding, based on this wording, of the absolute and relative risk of thrombosis in pill users and in pregnancy. The results showed that less than 12% of women in the (higher education) group fully understood the absolute levels of risk from taking the pill and from being pregnant. Relative risk was also poorly understood, with less than 40% of participants showing full understanding, and 20% showing no understanding. We recommend that the CSM revisit the wording currently provided to millions of women in the UK.