Occipito-temporal contributions to reading

The debate regarding the role of ventral occipito-temporal cortex (vOTC) in visual word recognition arises in part from difficulty delineating the functional contributions of vOTC as separate from other areas of the reading network. Successful transcranial magnetic stimulation (TMS) of the area could provide a novel source of information regarding the area’s function, by offering the possibility of temporarily, non-invasively perturbing its information processing and assessing the consequences on behaviour. However, the area is often considered too deep to successfully stimulate with TMS. Thus the initial step was the demonstration of the feasibility of stimulation, which I proved in the first series of experiments. The stimulation resulted in a disruption in visual word recognition that was stimulus- and site- specific. The second series of experiments further investigated the stimulus-specificity, demonstrating that the nature of this specificity was task-dependent. The final series of TMS experiments in the thesis utilised the high temporal resolution of TMS to map out the dynamics of processing in both left and right vOTC, revealing hemispheric asymmetries in the time course of ventral occipito-temporal processing consistent for both visual words and objects. To complete these experiments, I acquired a large amount of functional localiser data for neuronavigated TMS. This allowed the investigation of the effectiveness of fMRI localisation for TMS and in addition the investigation of the important issue of how consistent the functional regions of interest (fROI) produced by these scans are. The first of two experiments showed these fROIs may have surprisingly poor reliability while the second investigated how best they can be optimised, maximising reliability. In conclusion, my PhD has demonstrated the feasibility and potential of using TMS to investigate vOTC contributions to visual word and object recognition, providing a novel source of information capable of informing the ongoing debate concerning vOTC

The Role Of Mergers In Galaxy Formation And Transformations

Large scale structure and cosmolog

Galaxy evolution in all five CANDELS fields and IllustrisTNG: morphological, structural, and the major merger evolution to z 3

Large scale structure and cosmolog

Ridge Formation and De-Spinning of Iapetus via an Impact-Generated Satellite

We present a scenario for building the equatorial ridge and de-spinning Iapetus through an impact-generated disk and satellite. This impact puts debris into orbit, forming a ring inside the Roche limit and a satellite outside. This satellite rapidly pushes the ring material down to the surface of Iapetus, and then itself tidally evolves outward, thereby helping to de-spin Iapetus. This scenario can de-spin Iapetus an order of magnitude faster than when tides due to Saturn act alone, almost independently of its interior geophysical evolution. Eventually, the satellite is stripped from its orbit by Saturn. The range of satellite and impactor masses required is compatible with the estimated impact history of Iapetus.Comment: 19 pages, 3 figures; Icarus, in pres

Blockchain for Power Grids

Sharing information is an important part of regulating and maintaining efficient and safe power grids. This project’s goal is to develop a way of using blockchain technology to share transaction information among different power grids in a secure, controlled, monitored, and efficient manner. The biggest concern regarding the data is integrity. By leveraging blockchain technology, the data will be reliable and resilient to attacks, such as man-in-the-middle and data spoofing attacks. The Hyperledger Fabric implementation provides a permissioned network in which power grids will act as nodes that maintain ledger information. By using a distributed ledger to validate transactions through the process of consensus, the system can share information in a manner that is more secure and transparent than traditional information sharing systems in which data is less secure and takes longer to validate. The additional layers of security and speed that Hyperledger technology provides help to prevent issues, such as power grid failures, that could stem from the latency or integrity issues involved with traditional methods of validating, processing, and reacting to shared data

Revealing new high-redshift quasar populations through Gaussian mixture model selection

Galaxie

H110alpha recombination-line emission and 4.8-GHz continuum emission in the Carina Nebula

We present results from observations of H110alpha recombination-line emission at 4.874 GHz and the related 4.8-GHz continuum emission towards the Carina Nebula using the Australia Telescope Compact Array. These data provide information on the velocity, morphology and excitation parameters of the ionized gas associated with the two bright HII regions within the nebula, Car I and Car II. They are consistent with both Car I and Car II being expanding ionization fronts arising from the massive star clusters Trumpler 14 and Trumpler 16, respectively. The overall continuum emission distribution at 4.8 GHz is similar to that at lower frequencies. For Car I, two compact sources are revealed that are likely to be young HII regions associated with triggered star formation. These results provide the first evidence of ongoing star formation in the northern region of the nebula. A close association between Car I and the molecular gas is consistent with a scenario in which Car I is currently carving out a cavity within the northern molecular cloud. The complicated kinematics associated with Car II point to expansion from at least two different centres. All that is left of the molecular cloud in this region are clumps of dense gas and dust which are likely to be responsible for shaping the striking morphology of the Car II components.Comment: 10 pages, 7 figures, accepted for publication in MNRA

Coulomb blockade of strongly coupled quantum dots studied via bosonization of a channel with a finite barrier

A pair of quantum dots, coupled through a point contact, can exhibit Coulomb blockade effects that reflect an oscillatory term in the dots' total energy whose value depends on whether the total number of electrons on the dots is even or odd. The effective energy associated with this even-odd alternation is reduced, relative to the bare Coulomb blockade energy for uncoupled dots, by a factor (1-f) that decreases as the interdot coupling is increased. When the transmission coefficient for interdot electronic motion is independent of energy and the same for all channels within the point contact (which are assumed uncoupled), the factor (1-f) takes on a universal value determined solely by the number of channels and the dimensionless conductance g of each individual channel. This paper studies corrections to the universal value of (1-f) that result when the transmission coefficent varies over energy scales of the size of the bare Coulomb blockade energy. We consider a model in which the point contact is described by a single orbital channel containing a parabolic barrier potential, and we calculate the leading correction to (1-f) for one-channel (spin-split) and two-channel (spin-degenerate) point contacts in the limit where the single orbital channel is almost completely open. By generalizing a previously used bosonization technique, we find that, for a given value of the dimensionless conductance g, the value of (1-f) is increased relative to its value for a zero-thickness barrier, but the absolute value of the increase is small in the region where our calculations apply.Comment: 13 pages, 3 Postscript figure

The spectral energy distributions of active galactic nuclei

Galaxie

Flavor changing single top quark production channels at e^+e^- colliders in the effective Lagrangian description

We perform a global analysis of the sensitivity of LEP2 and e^+e^- colliders with a c.m. energy in the range 500 - 2000 GeV to new flavor-changing single top quark production in the effective Lagrangian approach. The processes considered are sensitive to new flavor-changing effective vertices such as Ztc, htc, four-Fermi tcee contact terms as well as a right-handed Wtb coupling. We show that e^+ e^- colliders are most sensitive to the physics responsible for the contact tcee vertices. For example, it is found that the recent data from the 189 GeV LEP2 run can be used to rule out any new flavor physics that can generate these four-Fermi operators up to energy scales of \Lambda > 0.7 - 1.4 TeV, depending on the type of the four-Fermi interaction. We also show that a corresponding limit of \Lambda > 1.3 - 2.5 and \Lambda > 17 - 27 TeV can be reached at the future 200 GeV LEP2 run and a 1000 GeV e^+e^- collider, respectively. We note that these limits are much stronger than the typical limits which can be placed on flavor diagonal four-Fermi couplings. Similar results hold for \mu^+\mu^- colliders and for tu(bar) associated production. Finally we briefly comment on the necessity of measuring all flavor-changing effective vertices as they can be produced by different types of heavy physics.Comment: 34 pages, plain latex, 7 figures embadded in the text using epsfig. Added new references and discussions regarding their relevance to the paper. Added more comments on the comparison between flavor-changing and flavor-diagonal contact terms and on the importance of measuring the Ztc verte