UCL University College London Eprints
UCL Eprints collects the work of UCL researchers and makes it freely available over the web, helping the worldwide scholarly community to discover UCL research. Institutional repositories like UCL Eprints complement the traditional academic publishing and scholarly communications processes. They raise the visibility of research and help to maximise its impact. UCL researchers are encouraged to deposit a copy of each journal article, conference paper, working paper, and any other research output, in the UCL Eprints at the earliest opportunity, ensuring that their research reaches as wide an audience as possible.
Motor skill learning requires active central myelination. - McKenzie, IA; Ohayon, D; Li, H; de Faria, JP; Emery, B; Tohyama, K; Richardson, WD
Myelin-forming oligodendrocytes (OLs) are formed continuously in the healthy adult brain. In this work, we study the function of these late-forming cells and the myelin they produce. Learning a new motor skill (such as juggling) alters the structure of the brain's white matter, which contains many OLs, suggesting that late-born OLs might contribute to motor learning. Consistent with this idea, we show that production of newly formed OLs is briefly accelerated in mice that learn a new skill (running on a "complex wheel" with irregularly spaced rungs). By genetically manipulating the transcription factor myelin regulatory factor in OL precursors, we...
The impact of the Neolithic agricultural transition in Britain: A comparison of pollen-based land-cover and archaeological C date-inferred population change - Woodbridge, J; Fyfe, RM; Roberts, N; Downey, S; Edinborough, K; Shennan, S
Britain's landscapes were substantially transformed as a result of prehistoric agricultural clearance and deforestation. This process began in the Neolithic and is recorded in multiple different "archives", notably those deriving from archaeological site excavations and from off-site pollen records. This paper assesses the extent to which these two independent sources show common trends and timing in terms of demographic and environmental change across Britain during the millennia prior to and after the appearance of the first farming communities. This period is analysed within the wider context of the 9000-3400cal.BP time frame. We compare land-cover change aggregated from 42 pollen records...
Developing a novel comprehensive framework for the investigation of cellular and whole heart electrophysiology in the in situ human heart: Historical perspectives, current progress and future prospects - Taggart, P; Orini, M; Hayward, M; Lambiase, PD; Hanson, B; Clayton, R; Dobrzynski, H; Yanni, J; Boyett, M
Understanding the mechanisms of fatal ventricular arrhythmias is of great importance. In view of the many electrophysiological differences that exist between animal species and humans, the acquisition of basic electrophysiological data in the intact human heart is essential to drive and complement experimental work in animal and in-silico models. Over the years techniques have been developed to obtain basic electrophysiological signals directly from the patients by incorporating these measurements into routine clinical procedures which access the heart such as cardiac catheterisation and cardiac surgery. Early recordings with monophasic action potentials provided valuable information including normal values for the invivo human...
Notes from the field: Tradition - Udechukwu, O; Brewer, J; Clarke, JA; Guha-Thakurta, T; Hayden, H; Horowitz, GM; Da Costa Kaufmann, T; Küchler, S; Loh, MH; Phillips, RB; Prange, R; Russo, A
High-gain triple-band reconfigurable Vivaldi antenna - Fortuny, CB; Tong, KF; Chetty, K; Brittan, P
A frequency agile Vivaldi antenna whose operating frequency band can be switched is proposed. High-performance radio-frequency micro-electromechanical system (RF-MEMS) switches allow tuning of the operational band between 2.0 GHz, 3.7 GHz and 5.2 GHz. The average gains of the antenna for the low, mid and high bands are 8.5 dBi, 12.5 dBi and 13.7 dBi, respectively. This reconfigurable antenna offers improved performance over multiple, wideband and multiband antennas without increases in cost and size.
The Lindi Formation (upper Albian-Coniacian) and Tanzania Drilling Project Sites 36-40 (Lower Cretaceous to Paleogene): Lithostratigraphy, biostratigraphy and chemostratigraphy - Jiménez Berrocoso, A; Huber, BT; MacLeod, KG; Haynes, SJ; Petrizzo, MR; Falzoni, F; Lees, JA; Bown, PR; Wendler, I; Coxall, H; Mweneinda, AK; Singano, JM; Birch, H; Robinson, SA
The 2009 Tanzania Drilling Project (TDP) expedition to southeastern Tanzania cored a total of 572.3. m of sediments at six new mid-Cretaceous to mid-Paleocene boreholes (TDP Sites 36, 37, 38, 39, 40A, 40B). Added to the sites drilled in 2007 and 2008, the new boreholes confirm the common excellent preservation of planktonic and benthic foraminifera and calcareous nannofossils from core samples that will be used for biostratigraphy, evolutionary studies, paleoceanography and climatic reconstructions from the Tanzanian margin, with implications elsewhere. The new sites verify the presence of a relatively expanded Upper Cretaceous succession in the region that has allowed a...
Biometry of Upper Cretaceous (Cenomanian-Maastrichtian) coccoliths - a record of long-term stability and interspecies size shifts - Linnert, C; Mutterlose, J; Bown, PR
Biometric measurements of Mesozoic coccoliths (coccolith length and width) have been used in short-term biostratigraphic, taxonomic and palaeoecologic studies, but until now, not over longer time scales. Here, we present a long time-series study (∼. 30. million years) for the Upper Cretaceous, which aims to identify broad trends in coccolith size and to understand the factors governing coccolith size change over long time scales. We have generated biometric data for the dominant Upper Cretaceous coccolith groups,. Broinsonia/. Arkhangelskiella,. Prediscosphaera,. Retecapsa and. Watznaueria, from 36 Cenomanian-Maastrichtian (100.5-66. Ma) samples from Goban Spur in the northeast Atlantic (DSDP Site 549). These data...
Memorandum - Harris, AJL; Harvey, N; Smith, LA; Stainforth, DA; Thomson, E
The effect of alcohol consumption on the adolescent brain: A systematic review of MRI and fMRI studies of alcohol-using youth - Feldstein Ewing, SW; Sakhardande, A; Blakemore, S-J
Conclusions Alcohol consumption during adolescence was associated with significant differences in structure and function in the developing human brain. However, this is a nascent field, with several limiting factors (including small sample sizes, cross-sectional designs, presence of confounding factors) within many of the reviewed studies, meaning that results should be interpreted in light of the preliminary state of the field. Future longitudinal and large-scale studies are critical to replicate the existing findings, and to provide a more comprehensive and conclusive picture of the effect of alcohol consumption on the developing brain.
Transmit-Power Efficient Linear Precoding Utilizing Known Interference for the Multiantenna Downlink - Razavi, SM; Ratnarajah, T; Masouros, C
It has been shown that the knowledge of both channel and data information at the base station prior to downlink transmission can help increase the received signal-to-noise ratio (SNR) of each user without the need to increase the transmitted power. Achievability is based on the idea of phase alignment (PA) precoding, where instead of nulling out the destructive interference, it judiciously rotates the phases of the transmitted symbols. In this way, they add up coherently at the intended user and yield higher received SNRs. In addition, it is well known that regularized channel inversion (RCI) precoding improves the performance of...
Optimizing interference as a source of signal energy with non-linear precoding - Garcia-Rodriguez, A; Masouros, C
Exploiting interference as a useful resource will be one of the main innovations in 5G communications. In this paper, we explore how to handle the interference to reduce the total transmit power of the Tomlinson-Harashima precoder (THP). We show that the energy efficiency can be improved by adaptively scaling the constellation symbols so that they are better aligned with the interfering signals to be canceled. The theoretical and simulation results of this paper prove that the proposed technique is not only able to preserve the average performance of the conventional THP, but it can also increase its power efficiency by...
Regularized phase alignment precoding for the MISO downlink - Razavi, SM; Ratnarajah, T; Masouros, C; Sellathurai, M
With the knowledge of both channel and data information at the base station prior to downlink transmission, we can increase the received signal-to-noise ratio (SNR) of each user without the need to increase the transmitted power. Achievability is based on the idea of phase alignment (PA) precoding where instead of removing the destructive interference, it judiciously rotates the phases of the transmitted symbols. In this way, for each user, the received interference from the other users add up coherently, and consequently we can glean higher received SNRs at all mobile terminals. In addition, it is well-known that the regularized channel...
Early Eocene sedimentary recycling in the Kailas area, southwestern Tibet: Implications for the initial India–Asia collision - Wang, J-G; Hu, X-M; BouDagher-Fadel, M; Wu, F-Y; Sun, G-Y
Syncollisional sedimentary rocks in the Himalayan orogen record important information about the early history of the India–Asia collision. This article presents a combined stratigraphic, sedimentologic, micropaleontologic, and provenance data for the Early Eocene clastic strata (Dajin Formation) in the Kailas area, southwestern Tibet. The Dajin Formation comprises ungraded and normally graded, matrix- and clast-supported conglomerates, ungraded and cross-stratified sandstones, and massive to poorly laminated mudstones. Deposition of the rocks is characterized by subaerial and subaqueous debris flows, waning gravity flows and suspension fallout. The larger benthic foraminifera and the youngest ages of the detrital zircons constrain the depositional age to...
Xigaze forearc basin revisited (South Tibet): Provenance changes and origin of the Xigaze Ophiolite - An, W; Hu, X; Garzanti, E; BouDagher-Fadel, MK; Wang, J; Sun, G
Our new stratigraphic, sedimentological, and micropaleontological analysis, integrated with basalt geochemistry, sandstone petrography, and detrital-zircon U-Pb and Hf isotope data, suggests the revision of current models for the geological evolution of the Asian active margin during the Cretaceous. The Xigaze forearc basin began to form in the late Early Cretaceous, south of the Gangdese arc, during the initial subduction of the Neotethyan oceanic lithosphere under the Lhasa terrane. Well-preserved stratigraphic successions document the classical upwardshallowing pattern of the forearc-basin strata and elucidate the origin of the associated oceanic magmatic rocks. The normal midocean- ridge basalt (N-MORB) geochemical signature and stratigraphic...