The site of regulation of light capture in Symbiodinium: Does the peridinin-chlorophyll a-protein detach to regulate light capture?

Dinoflagellates from the genus Symbiodinium form symbiotic associations with cnidarians including corals and anemones. The photosynthetic apparatuses of these dinoflagellates possess a unique photosynthetic antenna system incorporating the peridinin-chlorophyll a-protein (PCP). It has been proposed that the appearance of a PCP-specific 77 K fluorescence emission band around 672-675 nm indicates that high light treatment results in PCP dissociation from intrinsic membrane antenna complexes, blocking excitation transfer to the intrinsic membrane-bound antenna complexes, chlorophyll a-chlorophyll c 2-peridinin-protein-complex (acpPC) and associated photosystems (Reynolds et al., 2008 Proc Natl Acad Sci USA 105:13674-13678).We have tested this model using time-resolved fluorescence decay kinetics in conjunction with global fitting to compare the time-evolution of the PCP spectral bands before and after high light exposure. Our results show that no long-lived PCP fluorescence emission components appear either before or after high light treatment, indicating that the efficiency of excitation transfer from PCP to membrane antenna systems remains efficient and rapid even after exposure to high light. The apparent increased relative emission at around 675 nm was, instead, caused by strong preferential exciton quenching of the membrane antenna complexes associated with acpPC and reaction centers. This strong non-photochemical quenching (NPQ) is consistent with the activation of xanthophyll-Associated quenching mechanisms and the generally-observed avoidance in nature of long-lived photoexcited states that can lead to oxidative damage. The acpPC component appears to be the most strongly quenched under high light exposure suggesting that it houses the photoprotective exciton quencher. © 2014 Elsevier B.V

Spud 1.0: generalising and automating the user interfaces of scientific computer models

The interfaces by which users specify the scenarios to be simulated by scientific computer models are frequently primitive, under-documented and ad-hoc text files which make using the model in question difficult and error-prone and significantly increase the development cost of the model. In this paper, we present a model-independent system, Spud, which formalises the specification of model input formats in terms of formal grammars. This is combined with an automated graphical user interface which guides users to create valid model inputs based on the grammar provided, and a generic options reading module, libspud, which minimises the development cost of adding model options. <br><br> Together, this provides a user friendly, well documented, self validating user interface which is applicable to a wide range of scientific models and which minimises the developer input required to maintain and extend the model interface

Circuit Design to Stabilize the Reflectometer Local Oscillator Signals

Reflectometry, which uses the microwave radar technique to probe the magnetically confined fusion plasmas, is a very powerful tool to observe the density fluctuations in the fusion plasmas. Typically, two or more microwave beams of different frequencies are used to study the plasma density fluctuations. The frequency separation between these two beams of the PPPL designed reflectometer system upgrade on the DIII-D tokamak can be varied over 18 GHz. Due to the performance of the associated electronics, the local oscillator (LO) power level at the LO port of the I/Q demodulator suffers more than 12 dB of power fluctuations when the frequency separation is varied. Thus, the I/Q demodulator performance is impaired. In order to correct this problem, a power leveling circuit is introduced in the PPPL upgrade. According to the test results, the LO power fluctuation was regulated to be within 1 dB for greater than 16 dB of input power variation over the full dynamic bandwidth of the receiver

Multiscale modelling of auxin transport in the plant-root elongation zone

In the root elongation zone of a plant, the hormone auxin moves in a polar manner due to active transport facilitated by spatially distributed influx and efflux carriers present on the cell membranes. To understand how the cell-scale active transport and passive diffusion combine to produce the effective tissue-scale flux, we apply asymptotic methods to a cell-based model of auxin transport to derive systematically a continuum description from the spatially discrete one. Using biologically relevant parameter values, we show how the carriers drive the dominant tissue-scale auxin flux and we predict how the overall auxin dynamics are affected by perturbations to these carriers, for example, in knockout mutants. The analysis shows how the dominant behaviour depends on the cells' lengths, and enables us to assess the relative importance of the diffusive auxin flux through the cell wall. Other distinguished limits are also identified and their potential roles discussed. As well as providing insight into auxin transport, the study illustrates the use of multiscale (cell to tissue) methods in deriving simplified models that retain the essential biology and provide understanding of the underlying dynamics

Carbon Emission Flow in Networks

As the human population increases and production expands, energy demand and anthropogenic carbon emission rates have been growing rapidly, and the need to decrease carbon emission levels has drawn increasing attention. The link between energy production and consumption has required the large-scale transport of energy within energy transmission networks. Within this energy flow, there is a virtual circulation of carbon emissions. To understand this circulation and account for the relationship between energy consumption and carbon emissions, this paper introduces the concept of “carbon emission flow in networks” and establishes a method to calculate carbon emission flow in networks. Using an actual analysis of China's energy pattern, the authors discuss the significance of this new concept, not only as a feasible approach but also as an innovative theoretical perspective

An HIV epidemic is ready to emerge in the Philippines

<p>Abstract</p> <p>Background</p> <p>The state of the HIV epidemic in the Philippines has been described as "low and slow", which is in stark contrast to many other countries in the region. A review of the conditions for HIV spread in the Philippines is necessary.</p> <p>Methods</p> <p>We evaluated the current epidemiology, trends in behaviour and public health response in the Philippines to identify factors that could account for the current HIV epidemic, as well as to review conditions that may be of concern for facilitating an emerging epidemic.</p> <p>Results</p> <p>The past control of HIV in the Philippines cannot be attributed to any single factor, nor is it necessarily a result of the actions of the Filipino government or other stakeholders. Likely reasons for the epidemic's slow development include: the country's geography is complicated; injecting drug use is relatively uncommon; a culture of sexual conservatism exists; sex workers tend to have few clients; anal sex is relatively uncommon; and circumcision rates are relatively high.</p> <p>In contrast, there are numerous factors suggesting that HIV is increasing and ready to emerge at high rates, including: the lowest documented rates of condom use in Asia; increasing casual sexual activity; returning overseas Filipino workers from high-prevalence settings; widespread misconceptions about HIV/AIDS; and high needle-sharing rates among injecting drug users.</p> <p>There was a three-fold increase in the rate of HIV diagnoses in the Philippines between 2003 and 2008, and this has continued over the past year. HIV diagnoses rates have noticeably increased among men, particularly among bisexual and homosexual men (114% and 214% respective increases over 2003-2008). The average age of diagnosis has also significantly decreased, from approximately 36 to 29 years.</p> <p>Conclusions</p> <p>Young adults, men who have sex with men, commercial sex workers, injecting drug users, overseas Filipino workers, and the sexual partners of people in these groups are particularly vulnerable to HIV infection. There is no guarantee that a large HIV epidemic will be avoided in the near future. Indeed, an expanding HIV epidemic is likely to be only a matter of time as the components for such an epidemic are already present in the Philippines.</p

Chemical bonding in zeolites

A review is given with 28 refs. on the current status of chem. bonding of zeolites and AlPO's. Short range covalent bonding dominates, the tetrahedra have to be considered relatively rigid and the Si-O-Si bond angle flexible. Differences in energy of the SiO2 or AlPO4 polymorphs are small. The relative stability depends on a proper accounting of the small changes in electrostatic energy. The deprotonation energy is also mainly detd. by short range covalent interactions. These are only properly accounted for when full lattice relaxation is included in the calcns. Isomorphous substitution effects are also dominated by changes in covalent interaction energ

Comparison of two different physical activity monitors

<p>Abstract</p> <p>Background</p> <p>Understanding the relationships between physical activity (PA) and disease has become a major area of research interest. Activity monitors, devices that quantify free-living PA for prolonged periods of time (days or weeks), are increasingly being used to estimate PA. A range of different activity monitors brands are available for investigators to use, but little is known about how they respond to different levels of PA in the field, nor if data conversion between brands is possible.</p> <p>Methods</p> <p>56 women and men were fitted with two different activity monitors, the Actigraph™ (Actigraph LLC; AGR) and the Actical™ (Mini-Mitter Co.; MM) for 15 days. Both activity monitors were fixed to an elasticized belt worn over the hip, with the anterior and posterior position of the activity monitors randomized. Differences between activity monitors and the validity of brand inter-conversion were measured by <it>t</it>-tests, Pearson correlations, Bland-Altman plots, and coefficients of variation (CV).</p> <p>Results</p> <p>The AGR detected a significantly greater amount of daily PA (216.2 ± 106.2 vs. 188.0 ± 101.1 counts/min, P < 0.0001). The average difference between activity monitors expressed as a CV were 3.1 and 15.5% for log-transformed and raw data, respectively. When a conversion equation was applied to convert datasets from one brand to another, the differences were no longer significant, with CV's of 2.2 and 11.7%, log-transformed and raw data, respectively.</p> <p>Conclusion</p> <p>Although activity monitors predict PA on the same scale (counts/min), the results between these two brands are not directly comparable. However, the data are comparable if a conversion equation is applied, with better results for log-transformed data.</p

The magic nature of 132Sn explored through the single-particle states of 133Sn

Atomic nuclei have a shell structure where nuclei with 'magic numbers' of neutrons and protons are analogous to the noble gases in atomic physics. Only ten nuclei with the standard magic numbers of both neutrons and protons have so far been observed. The nuclear shell model is founded on the precept that neutrons and protons can move as independent particles in orbitals with discrete quantum numbers, subject to a mean field generated by all the other nucleons. Knowledge of the properties of single-particle states outside nuclear shell closures in exotic nuclei is important for a fundamental understanding of nuclear structure and nucleosynthesis (for example the r-process, which is responsible for the production of about half of the heavy elements). However, as a result of their short lifetimes, there is a paucity of knowledge about the nature of single-particle states outside exotic doubly magic nuclei. Here we measure the single-particle character of the levels in 133Sn that lie outside the double shell closure present at the short-lived nucleus 132Sn. We use an inverse kinematics technique that involves the transfer of a single nucleon to the nucleus. The purity of the measured single-particle states clearly illustrates the magic nature of 132Sn.Comment: 19 pages, 5 figures and 4 table