Caffeine-Induced Global Reductions in Resting-State BOLD Connectivity Reflect Widespread Decreases in MEG Connectivity.

In resting-state functional magnetic resonance imaging (fMRI), the temporal correlation between spontaneous fluctuations of the blood oxygenation level dependent (BOLD) signal from different brain regions is used to assess functional connectivity. However, because the BOLD signal is an indirect measure of neuronal activity, its complex hemodynamic nature can complicate the interpretation of differences in connectivity that are observed across conditions or subjects. For example, prior studies have shown that caffeine leads to widespread reductions in BOLD connectivity but were not able to determine if neural or vascular factors were primarily responsible for the observed decrease. In this study, we used source-localized magnetoencephalography (MEG) in conjunction with fMRI to further examine the origins of the caffeine-induced changes in BOLD connectivity. We observed widespread and significant (p < 0.01) reductions in both MEG and fMRI connectivity measures, suggesting that decreases in the connectivity of resting-state neuro-electric power fluctuations were primarily responsible for the observed BOLD connectivity changes. The MEG connectivity decreases were most pronounced in the beta band. By demonstrating the similarity in MEG and fMRI based connectivity changes, these results provide evidence for the neural basis of resting-state fMRI networks and further support the potential of MEG as a tool to characterize resting-state connectivity

Long range action in networks of chaotic elements

We show that under certain simple assumptions on the topology (structure) of networks of strongly interacting chaotic elements a phenomenon of long range action takes place, namely that the asymptotic (as time goes to infinity) dynamics of an arbitrary large network is completely determined by its boundary conditions. This phenomenon takes place under very mild and robust assumptions on local dynamics with short range interactions. However, we show that it is unstable with respect to arbitrarily weak local random perturbations.Comment: 15 page

Harmonic oscillations and their switching in elliptical optical waveguide arrays

We have studied harmonic oscillations in an elliptical optical waveguide array in which the coupling between neighboring waveguides is varied in accord with a Kac matrix so that the propagation constant eigenvalues can take equally spaced values. As a result, long-living Bloch oscillation (BO) and dipole oscillation (DO) are obtained when a linear gradient in the propagation constant is applied. Moreover, we achieve a switching from DO to BO or vice versa by ramping up the gradient profile. The various optical oscillations as well as their switching are investigated by field evolution analysis and confirmed by Hamiltonian optics. The equally spaced eigenvalues in the propagation constant allow viable applications in transmitting images, switching and routing of optical signals.Comment: 14 pages, 5 figure

Invasive trees in Singapore: Are they a threat to native forests?

Tropical Conservation Science81201-21

Educational Telecommunications Networks(Second Main Session "International Educational Networks and Development in the Pacific Basin",AN INTERNATIONAL SYMPOSIUM THE IMPACT OF HIGHER EDUCATION ON SOCIAL TRANSFORMATION IN ASIA & THE PACIFIC)

This paper focuses on the networking that is in place, required and proposed for the University of the South Pacific (USP). The map of the countries should clearly give one reason, our university is in the region and not just of the region. There are three complexes, two campuses, nine extension centres, seven institutes and two teaching units spread over more than 32 million square kilometres of ocean. Thus because of the nature of the University and its physical spread, communication between staff, and between staff and students needs to be reliable, comprehensive and of a high standard. The students\u27 point of communication with teachers through the extension Centres, is via satellite tutorials, visiting tutorials, comments on assignments or circulars. A dilemma exists, however: is the proposed communications system to be used as a supplement to USP\u27s distance programme, or is it to become an integral part of the learning package? If the latter position is taken then the questions of equity, equality and access become major considerations. The link between tertiary institutions in the region is sparse. This is also true of connections with institutions outside the region. The Japanese government, in association with a university in Tokyo, has sent a team to USP to establish an experimental earth station for the ETS-V project. This is scheduled to be operational this month. USP recognises the development of other networks in the Pacific as being of critical importance. Notable amongst these are: PEACESAT, SIDEN, FFANET, MICRONET and the proposed COL initiatives. (I note on the programme that there are speakers from the Solomon Islands and Hawaii who will no doubt speak about their systems. Thus I only mention them in passing here.) One of the major features of the new USPNET must be connectivity to other networks, both in the region and world. The University considers this an integral part of its net, and has applied for connection to PEACESAT through the establishment of an earth station in Suva. There is also a PEACESAT terminal at its Alafua campus. The system will ensure that connectivity within and outside the region is achieved. An example of what can be achieved with cooperation and dedication is PIMRIS. The implications of the proposed system for the University, its distance education programme and its service to the region are discussed. The fundamental questions of: _ education and development for what? _ education and development for whom? _ education and development by whom? are considered. Due to the lack of communication, the education wheel is continuously being reinvented. This should not be the case once the USP\u27s system is in place. Until this happens, (and it can only happen with the support of developed nations if the telecommunications system is to reach the outer islands where it is needed most urgently), the \u27taming of distance and time\u27 will only be a dream. The conclusion is that USP considers that the need for its educational network is sufficiently large and unique to justify a venture of its own. It would like to be connected to other networks, but it requires 24 hours availability under autonomous management and full control. USP appreciates, however, that any communications system is only as good as the use to which it is put and to this end a lot of effort is being directed. There are many staff in \u27outposts\u27 who tend to feel isolated just like the students there so the paper closes with a poem that was written by one of them

Characterization of a Specificity Factor for an AAA+ ATPase Assembly of SspB Dimers with ssrA-Tagged Proteins and the ClpX Hexamer

AbstractSspB, a specificity factor for the ATP-dependent ClpXP protease, stimulates proteolysis of protein substrates bearing the ssrA degradation tag. The SspB protein is shown here to form a stable homodimer with two independent binding sites for ssrA-tagged proteins or peptides. SspB by itself binds to ClpX and stimulates the ATPase activity of this enzyme. In the presence of ATPγS, a ternary complex of SspB, GFP-ssrA, and the ClpX ATPase was sufficiently stable to isolate by gel-filtration or ion-exchange chromatography. This complex consists of one SspB dimer, two molecules of GFP-ssrA, and one ClpX hexamer. SspB dimers do not commit bound substrates to ClpXP degradation but increase the affinity and cooperativity of binding of ssrA-tagged substrates to ClpX, facilitating enhanced degradation at low substrate concentrations

An Expanded Conformation of Single-Ring GroEL-GroES Complex Encapsulates an 86 kDa Substrate

SummaryElectron cryomicroscopy reveals an unprecedented conformation of the single-ring mutant of GroEL (SR398) bound to GroES in the presence of Mg-ATP. This conformation exhibits a considerable expansion of the folding cavity, with ∼80% more volume than the X-ray structure of the equivalent cis cavity in the GroEL-GroES-(ADP)7 complex. This expanded conformation can encapsulate an 86 kDa heterodimeric (αβ) assembly intermediate of mitochondrial branched-chain α-ketoacid dehydrogenase, the largest substrate ever observed to be cis encapsulated. The SR398-GroES-Mg-ATP complex is found to exist as a mixture of standard and expanded conformations, regardless of the absence or presence of the substrate. However, the presence of even a small substrate causes a pronounced bias toward the expanded conformation. Encapsulation of the large assembly intermediate is supported by a series of electron cryomicroscopy studies as well as the protection of both α and β subunits of the substrate from tryptic digestion

A Translational Polarization Rotator

We explore a free-space polarization modulator in which a variable phase introduction between right- and left-handed circular polarization components is used to rotate the linear polarization of the outgoing beam relative to that of the incoming beam. In this device, the polarization states are separated by a circular polarizer that consists of a quarter-wave plate in combination with a wire grid. A movable mirror is positioned behind and parallel to the circular polarizer. As the polarizer-mirror distance is separated, an incident liear polarization will be rotated through an angle that is proportional to the introduced phase delay. We demonstrate a prototype device that modulates Stokes Q and U over a 20% bandwidth