1,325 research outputs found
Maximal supergravity in D=10: forms, Borcherds algebras and superspace cohomology
We give a very simple derivation of the forms of supergravity from
supersymmetry and SL(2,\bbR) (for IIB). Using superspace cohomology we show
that, if the Bianchi identities for the physical fields are satisfied, the
(consistent) Bianchi identities for all of the higher-rank forms must be
identically satisfied, and that there are no possible gauge-trivial Bianchi
identities () except for exact eleven-forms. We also show that the
degrees of the forms can be extended beyond the spacetime limit, and that the
representations they fall into agree with those predicted from Borcherds
algebras. In IIA there are even-rank RR forms, including a non-zero
twelve-form, while in IIB there are non-trivial Bianchi identities for
thirteen-forms even though these forms are identically zero in supergravity. It
is speculated that these higher-rank forms could be non-zero when higher-order
string corrections are included.Comment: 15 pages. Published version. Some clarification of the tex
IIA/IIB Supergravity and Ten-forms
We perform a careful investigation of which p-form fields can be introduced
consistently with the supersymmetry algebra of IIA and/or IIB ten-dimensional
supergravity. In particular the ten-forms, also known as "top-forms", require a
careful analysis since in this case, as we will show, closure of the
supersymmetry algebra at the linear level does not imply closure at the
non-linear level. Consequently, some of the (IIA and IIB) ten-form potentials
introduced in earlier work of some of us are discarded. At the same time we
show that new ten-form potentials, consistent with the full non-linear
supersymmetry algebra can be introduced. We give a superspace explanation of
our work. All of our results are precisely in line with the predictions of the
E(11) algebra.Comment: 17 page
Integrated Genomic and Transcriptomic Analysis of the Peridinin Dinoflagellate Amphidinium carterae Plastid.
The plastid genomes of peridinin-containing dinoflagellates are highly unusual, possessing very few genes, which are located on small chromosomal elements termed "minicircles". These minicircles may contain genes, or no recognisable coding information. Transcripts produced from minicircles may undergo unusual processing events, such as the addition of a 3' poly(U) tail. To date, little is known about the genetic or transcriptional diversity of non-coding sequences in peridinin dinoflagellate plastids. These sequences include empty minicircles, and regions of non-coding DNA in coding minicircles. Here, we present an integrated plastid genome and transcriptome for the model peridinin dinoflagellate Amphidinium carterae, identifying a previously undescribed minicircle. We also profile transcripts covering non-coding regions of the psbA and petB/atpA minicircles. We present evidence that antisense transcripts are produced within the A. carterae plastid, but show that these transcripts undergo different end cleavage events from sense transcripts, and do not receive 3' poly(U) tails. The difference in processing events between sense and antisense transcripts may enable the removal of non-coding transcripts from peridinin dinoflagellate plastid transcript pools.CNRS
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The funny thing about robot leadership
This is the author accepted manuscript. The final version is available from The European Business Review via the link in this recor
Ectoplasm with an Edge
The construction of supersymmetric invariant actions on a spacetime manifold
with a boundary is carried out using the "ectoplasm" formalism for the
construction of closed forms in superspace. Non-trivial actions are obtained
from the pull-backs to the bosonic bodies of closed but non-exact forms in
superspace; finding supersymmetric invariants thus becomes a cohomology
problem. For a spacetime with a boundary, the appropriate mathematical language
changes to relative cohomology, which we use to give a general formulation of
off-shell supersymmetric invariants in the presence of boundaries. We also
relate this construction to the superembedding formalism for the construction
of brane actions, and we give examples with bulk spacetimes of dimension 3, 4
and 5. The closed superform in the 5D example needs to be constructed as a
Chern-Simons type of invariant, obtained from a closed 6-form displaying Weil
triviality.Comment: 25 page
Pure Spinor Approach to Type IIA Superstring Sigma Models and Free Differential Algebras
This paper considers the Free Differential Algebra and rheonomic
parametrization of type IIA Supergravity, extended to include the BRS
differential and the ghosts. We consider not only the ghosts lambda's of
supersymmetry but also the ghosts corresponding to gauge and Lorentz
transformations. In this way we can derive not only the BRS transformations of
fields and ghosts but also the standard pure spinor constraints on lambda's.
Moreover the formalism allows to derive the action for the pure spinor
formulation of type IIA superstrings in a general background, recovering the
action first obtained by Berkovits and Howe.Comment: 1+23 pages, v2: added clarifications and a reference, misprints
corrected, v3: presentation improved, results unchange
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Treatment of bone loss in proximal femurs of postmenopausal osteoporotic women with AGN1 local osteo-enhancement procedure (LOEP) increases hip bone mineral density and hip strength: a long-term prospective cohort study.
This first-in-human study of AGN1 LOEP demonstrated that this minimally-invasive treatment durably increased aBMD in femurs of osteoporotic postmenopausal women. AGN1 resorption was coupled with new bone formation by 12 weeks and that new bone was maintained for at least 5-7 years resulting in substantially increased FEA-estimated femoral strength.IntroductionThis first-in-human study evaluated feasibility, safety, and in vivo response to treating proximal femurs of postmenopausal osteoporotic women with a minimally-invasive local osteo-enhancement procedure (LOEP) to inject a resorbable triphasic osteoconductive implant material (AGN1).MethodsThis prospective cohort study enrolled 12 postmenopausal osteoporotic (femoral neck T-score ≤ - 2.5) women aged 56 to 89 years. AGN1 LOEP was performed on left femurs; right femurs were untreated controls. Subjects were followed-up for 5-7 years. Outcomes included adverse events, proximal femur areal bone mineral density (aBMD), AGN1 resorption, and replacement with bone by X-ray and CT, and finite element analysis (FEA) estimated hip strength.ResultsBaseline treated and control femoral neck aBMD was equivalent. Treated femoral neck aBMD increased by 68 ± 22%, 59 ± 24%, and 58 ± 27% over control at 12 and 24 weeks and 5-7 years, respectively (p < 0.001, all time points). Using conservative assumptions, FEA-estimated femoral strength increased by 41%, 37%, and 22% at 12 and 24 weeks and 5-7 years, respectively (p < 0.01, all time points). Qualitative analysis of X-ray and CT scans demonstrated that AGN1 resorption and replacement with bone was nearly complete by 24 weeks. By 5-7 years, AGN1 appeared to be fully resorbed and replaced with bone integrated with surrounding trabecular and cortical bone. No procedure- or device-related serious adverse events (SAEs) occurred.ConclusionsTreating femurs of postmenopausal osteoporotic women with AGN1 LOEP results in a rapid, durable increase in aBMD and femoral strength. These results support the use and further clinical study of this approach in osteoporotic patients at high risk of hip fracture
Argumentation in school science : Breaking the tradition of authoritative exposition through a pedagogy that promotes discussion and reasoning
The value of argumentation in science education has become internationally recognised and has been the subject of many research studies in recent years. Successful introduction of argumentation activities in learning contexts involves extending teaching goals beyond the understanding of facts and concepts, to include an emphasis on cognitive and metacognitive processes, epistemic criteria and reasoning. The authors focus on the difficulties inherent in shifting a tradition of teaching from one dominated by authoritative exposition to one that is more dialogic, involving small-group discussion based on tasks that stimulate argumentation. The paper builds on previous research on enhancing the quality of argument in school science, to focus on how argumentation activities have been designed, with appropriate strategies, resources and modelling, for pedagogical purposes. The paper analyses design frameworks, their contexts and lesson plans, to evaluate their potential for enhancing reasoning through foregrounding the processes of argumentation. Examples of classroom dialogue where teachers adopt the frameworks/plans are analysed to show how argumentation processes are scaffolded. The analysis shows that several layers of interpretation are needed and these layers need to be aligned for successful implementation. The analysis serves to highlight the potential and limitations of the design frameworks
Managing water scarcity at a river basin scale with economic instruments
This paper presents a conceptual framework for both assessing the role of economic instruments, and reshaping them in order to enhance their contribution to the goals of managing water scarcity. Water management problems stem from the mismatch between a multitude of individual decisions, on the one hand, and the current and projected status of water resources on the other. Economics can provide valuable incentives that drive individual decisions, and can design efficient instruments to address water governance problems in a context of conflicting interests and relevant transaction costs. Yet, instruments such as water pricing or trading are mostly based on general principles of welfare economics that are not readily applicable to assets as complex as water. A flaw in welfare economic approaches lies in the presumption that economic instruments may be good orbad on their own (e.g., finding the "right" price). This vision changes radically when we focus on the problem, instead of the instrument. In this paper, we examine how economic instruments to achieve welfare-enhancing water resource outcomes can realize their full potential in basin-scale management contexts. We follow a political economy perspective that views conflicts between public and private interest as the main instrumental challenge of water management. Our analysis allows us to better understand the critical importance of economic instruments for reconciling individual actions towards collective ambitions of water efficiency, equity and sustainability with lessons for later-adopting jurisdictions. Rather than providing panaceas, the successful design and implementation of economic instruments as key river basin management arrangements involves high transaction costs, wide institutional changes and collective action at different levels
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