1,570 research outputs found

    Space shuttle launch vehicle performance trajectory, exchange ratios, and dispersion analysis

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    A baseline space shuttle performance trajectory for Mission 3A launched from WTR has been generated. Design constraints of maximum dynamic pressure, longitudinal acceleration, and delivered payload were satisfied. Payload exchange ratios are presented with explanation on use. Design envelopes of dynamic pressure, SRB staging point, aerodynamic heating and flight performance reserves are calculated and included

    Calculus and heat flow in metric measure spaces and applications to spaces with Ricci bounds from below

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    This paper is devoted to a deeper understanding of the heat flow and to the refinement of calculus tools on metric measure spaces (X,d,m). Our main results are: - A general study of the relations between the Hopf-Lax semigroup and Hamilton-Jacobi equation in metric spaces (X,d). - The equivalence of the heat flow in L^2(X,m) generated by a suitable Dirichlet energy and the Wasserstein gradient flow of the relative entropy functional in the space of probability measures P(X). - The proof of density in energy of Lipschitz functions in the Sobolev space W^{1,2}(X,d,m). - A fine and very general analysis of the differentiability properties of a large class of Kantorovich potentials, in connection with the optimal transport problem. Our results apply in particular to spaces satisfying Ricci curvature bounds in the sense of Lott & Villani [30] and Sturm [39,40], and require neither the doubling property nor the validity of the local Poincar\'e inequality.Comment: Minor typos corrected and many small improvements added. Lemma 2.4, Lemma 2.10, Prop. 5.7, Rem. 5.8, Thm. 6.3 added. Rem. 4.7, Prop. 4.8, Prop. 4.15 and Thm 4.16 augmented/reenforced. Proof of Thm. 4.16 and Lemma 9.6 simplified. Thm. 8.6 corrected. A simpler axiomatization of weak gradients, still equivalent to all other ones, has been propose

    Practical Methods for Identification of Rice Endosperm Protein Bodies and Fecal Protein Particles in Light Microscopy

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    Indigestible 1-3 ~m protein \u27cores\u27, particles that originate from protein bodies of rice endosperm, were examined in bright-field and fluorescence microscopy, using a variety of histological and histochemical procedures. Our application of histological, histochemical and chemical approaches to a study of the feces of aoimals fed rice-containing diets has resulted in the development of methods for routine identification of insoluble rice fecal protein particles. For the specific identification of rice endosperm storage protein, whether protein bodies, cores or fecal protein particles, aqueous eosin Y stain in conjunction with fluorescence microscopy, and a combination of orange G + aniline blue in bright-field microscopy appear to be reliable methods when used in conjunction with each other

    The Mtr4 Ratchet Helix and Arch Domain both Function to Promote RNA Unwinding

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    Mtr4 is a conserved Ski2-like RNA helicase and a subunit of the TRAMP complex that activates exosomemiated 3-5 turnover in nuclear RNA surveillance and processing pathways. Prominent features of the Mtr4 structure include a four-domain ring-like helicase core and a large arch domain that spans the core. The ‘ratchet helix’ is positioned to interact with RNA substrates as they move through the helicase. However, the contribution of the ratchet helix in Mtr4 activity is poorly understood. Here we show that strict conservation along the ratchet helix is particularly extensive for Ski2-like RNA helicases compared to related helicases. Mutation of residues along the ratchet helix alters in vitro activity in Mtr4 and TRAMP and causes slow growth phenotypes in vivo. We also identify a residue on the ratchet helix that influences Mtr4 affinity for polyadenylated substrates. Previous work indicated that deletion of the arch domain has minimal effect on Mtr4 unwinding activity. We now show that combining the arch deletion with ratchet helix mutations abolishes helicase activity and produces a lethal in vivo phenotype. These studies demonstrate that the ratchet helix modulates helicase activity and suggest that the arch domain plays a previously unrecognized role in unwinding substrates

    From log Sobolev to Talagrand: a quick proof

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    We provide yet another proof of the Otto-Villani theorem from the log Sobolev inequality to the Talagrand transportation cost inequality valid in arbitrary metric measure spaces. The argument relies on the recent develop- ment [2] identifying gradient flows in Hilbert space and in Wassertein space, emphasizing one key step as precisely the root of the Otto-Villani theorem. The approach does not require the doubling property or the validity of the local Poincar\ue9 inequality

    The Abresch-Gromoll inequality in a non-smooth setting

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    We prove that the Abresch-Gromoll inequality holds on infinitesimally Hilbertian CD(K,N) spaces in the same form as the one available on smooth Riemannian manifolds

    The challenges facing public libraries in the Big Society: The role of volunteers, and the issues that surround their use in England

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    The use of volunteers in English public libraries is nothing new, however their use is becoming ever greater and one may argue that we are increasingly seeing a mixed economy of public library provision, in the wider arena of the Big Society. This paper presents the findings of a Delphi Study of 15 library managers undertaken as part of a Professional Doctorate exploring the challenges facing public libraries in England today, particularly focusing on volunteer use. An overview of relevant supporting literature is provided to help contextualize the research, particularly focusing on concepts such as the political background surrounding policy development, community engagement, the Big Society, and volunteering. Explanation of how the Delphi Study was conducted is given, together with a discussion of the key findings. Results show that opinions of library managers cover a broad spectrum. Although volunteer use is generally viewed by the respondents as a good thing, with potential to further enhance a service and aid community engagement, there are also a number of concerns. These concerns particularly relate to the idea of the volunteer as a replacement to paid staff rather than an enhancement to the service. Other key concerns relate to the quality of service provision, the rationale behind volunteer use, and the capacity of communities to deliver. Volunteer use in public libraries on this scale is a new phenomenon, and the longevity of such a development is largely unknown. This raises the question as to whether this is simply a large scale ideological experiment, or a move to even greater community engagement

    Manifolds with small Dirac eigenvalues are nilmanifolds

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    Consider the class of n-dimensional Riemannian spin manifolds with bounded sectional curvatures and diameter, and almost non-negative scalar curvature. Let r=1 if n=2,3 and r=2^{[n/2]-1}+1 if n\geq 4. We show that if the square of the Dirac operator on such a manifold has rr small eigenvalues, then the manifold is diffeomorphic to a nilmanifold and has trivial spin structure. Equivalently, if M is not a nilmanifold or if M is a nilmanifold with a non-trivial spin structure, then there exists a uniform lower bound on the r-th eigenvalue of the square of the Dirac operator. If a manifold with almost nonnegative scalar curvature has one small Dirac eigenvalue, and if the volume is not too small, then we show that the metric is close to a Ricci-flat metric on M with a parallel spinor. In dimension 4 this implies that M is either a torus or a K3-surface

    Mathematical Reasoning: Evaluation report and executive summary

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    The Mathematical Reasoning programme aims to improve the mathematical attainment of pupils in Year 2 by developing their understanding of the logical principles underlying maths. The programme was previously tested in an EEF-funded efficacy trial (Improving Numeracy and Literacy in Key Stage 1) which suggested that it had a positive impact. The efficacy trial examined the programme under developer-led conditions. This report describes a follow-up effectiveness trial which examined the impact of the programme under everyday conditions in a large number of schools and with less involvement from the original developer. Mathematical Reasoning lessons focus on developing pupils’ understanding of number and quantitative reasoning. They cover principles such as place value and the inverse relation between addition and subtraction. The programme consists of ten units delivered to pupils by their teachers as part of their usual mathematics lessons. It is designed to be taught over a 12- to 15-week period, with each unit taking approximately one hour. Learning is supported by online games, which can be used by pupils both at school and at home. The intervention was originally developed by a team at the University of Oxford, led by Professor Terezinha Nunes and Professor Peter Bryant. The National Centre for Excellence in the Teaching of Mathematics (NCETM) contributed to the development of the training model used in this trial and coordinated the delivery of the training through the network of Maths Hubs (partnerships of schools created to lead improvements to maths education). In this trial, the teacher training was delivered using a ‘train-the-trainers’ model through eight Maths Hubs. Each Maths Hub was asked to recruit two ‘Work Group Leads’. The University of Oxford programme developers trained these Work Group Leads who then trained the teachers in participating schools to deliver the programme. To prepare them to train the teachers, Work Group Leads received an initial day of training, used the materials in their own teaching, and then received a further two days’ training. Teachers delivering the programme then received one day of training from a Work Group Lead as well as a visit from the Work Group Lead during programme delivery. They were also able to seek additional support directly from the Work Group Lead or ask questions through an online Maths Hub community. The impact of the programme on maths attainment was evaluated using a randomised controlled trial involving 160 schools. Schools were randomly allocated either to receive Mathematical Reasoning or to be in the control group, the latter having the opportunity to take part in the programme in the following school year. A process evaluation used observations of training sessions, teacher interviews, lesson observations, and an online survey of treatment and control schools to examine implementation and the factors influencing impact. The trial began in August 2015 and analysis and reporting of the trial completed in December 2018. The project was co-funded by the Worshipful Company of Actuaries

    Analytic and Reidemeister torsion for representations in finite type Hilbert modules

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    For a closed Riemannian manifold we extend the definition of analytic and Reidemeister torsion associated to an orthogonal representation of fundamental group on a Hilbert module of finite type over a finite von Neumann algebra. If the representation is of determinant class we prove, generalizing the Cheeger-M\"uller theorem, that the analytic and Reidemeister torsion are equal. In particular, this proves the conjecture that for closed Riemannian manifolds with positive Novikov-Shubin invariants, the L2 analytic and Reidemeister torsions are equal.Comment: 78 pages, AMSTe
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