58 research outputs found
Physicist\u27s Reformed Critique of Nonreductive Physicalism and Emergence
Two figures are included. Dr. Sikkema has obtained permission from the first author of the paper from which Fig. 2 is adapted, as well as from the publisher
Science & Grace: God\u27s Reign in the Natural Sciences (Book Review)
Reviewed Title: Morris, Tim, and Don Petcher. Science & Grace: Godâs Reign in the Natural Sciences. Wheaton Illinois: Crossway Books, 2006. 352pp. ISBN 978-1-58134-549-0
Scientific Theology, Vol. I: Nature (Book Review)
Reviewed Title: A Scientific Theology, Vol. I: Nature, by Alister E. McGrath (Grand Rapids: Eerdmans, 2001). 325 pp. Cloth $40.00. ISBN 0-8028-3925-8
Spinning Tubes: An Authentic Research Experience in a Three-hour Laboratory
We discuss a three-hour laboratory that is a microcosm of physics research, starting with the discovery of an intriguing phenomenon, and including participation in âresearch conferencesâ and the interplay of theory and experiment. Students are given a small segment of PVC pipe marked at opposite ends with different symbols and asked to observe what happens when the pipe is placed on a horizontal surface and one end is pushed downward by a finger to initiate a rotation. Most students immediately recognize that the symbol at one end is visible while the other is not, and set about trying to understand why. Students initially work in pairs and are provided with opportunities to request equipment from a âgranting agencyâ and conferences and collaborations are encouraged. Students are quickly caught up in their search for explanations, usually culminating in a full-class effort with significant contributions coming from all students
Phase Transitions in the One-Dimensional Pair-Hopping Model: a Renormalization Group Study
The phase diagram of a one-dimensional tight-binding model with a
pair-hopping term (amplitude V) has been the subject of some controvery. Using
two-loop renormalization group equations and the density matrix renormalization
group with lengths L<=60, we argue that no spin-gap transition occurs at
half-filling for positive V, contrary to recent claims. However, we point out
that away from half-filling, a *phase-separation* transition occurs at finite
V. This transition and the spin-gap transition occuring at half-filling and
*negative* V are analyzed numerically.Comment: 7 pages RevTeX, 6 uuencoded figures which can be (and by default are)
directly included. Received by Phys. Rev. B 20 April 199
Spin Gap in a Doped Kondo Chain
We show that the Kondo chain away from half-filling has a spin gap upon the
introduction of an additional direct Heisenberg coupling between localized
spins. This is understood in the weak-Kondo-coupling limit of the
Heisenberg-Kondo lattice model by bosonization and in the strong-coupling limit
by a mapping to a modified t-J model. Only for certain ranges of filling and
Heisenberg coupling does the spin gap phase extend from weak to strong
coupling.Comment: 4 pages RevTeX including 4 eps figures; minor corrections and
clarification
Tracking the international spread of SARS-CoV-2 lineages B.1.1.7 and B.1.351/501Y-V2
Publisher Copyright: © 2021 O'Toole à et al.Late in 2020, two genetically-distinct clusters of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) with mutations of biological concern were reported, one in the United Kingdom and one in South Africa. Using a combination of data from routine surveillance, genomic sequencing and international travel we track the international dispersal of lineages B.1.1.7 and B.1.351 (variant 501Y-V2). We account for potential biases in genomic surveillance efforts by including passenger volumes from location of where the lineage was first reported, London and South Africa respectively. Using the software tool grinch (global report investigating novel coronavirus haplotypes), we track the international spread of lineages of concern with automated daily reports, Further, we have built a custom tracking website (cov-lineages.org/global_report.html) which hosts this daily report and will continue to include novel SARS-CoV-2 lineages of concern as they are detected.Peer reviewe
The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance
INTRODUCTION
Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic.
RATIONALE
We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs).
RESULTS
Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants.
CONCLUSION
Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century
- âŠ