669 research outputs found
A Note on Odd Periodic derived Hall algebras
Let be an odd positive integer and be the
-periodic derived category of a finitary hereditary abelian category
. In this note, we prove that there is an embedding of algebras
from the derived Hall algebra of defined by Xu-Chen [12] to
the extended derived Hall algebra of defined in [15]. This
homomorphism is given on basis elements, rather than just on generating
elements, and thus it improves the main result of [5].Comment: 13 page
The role of randomization inference in unraveling individual treatment effects in clinical trials: Application to HIV vaccine trials
Randomization inference is a powerful tool in early phase vaccine trials to
estimate the causal effect of a regimen against a placebo or another regimen.
Traditionally, randomization-based inference often focuses on testing either
Fisher's sharp null hypothesis of no treatment effect for any unit or Neyman's
weak null hypothesis of no sample average treatment effect. Many recent efforts
have explored conducting exact randomization-based inference for other
summaries of the treatment effect profile, for instance, quantiles of the
treatment effect distribution function. In this article, we systematically
review methods that conduct exact, randomization-based inference for quantiles
of individual treatment effects (ITEs) and extend some results by incorporating
auxiliary information often available in a vaccine trial. These methods are
suitable for four scenarios: (i) a randomized controlled trial (RCT) where the
potential outcomes under one regimen are constant; (ii) an RCT with no
restriction on any potential outcomes; (iii) an RCT with some user-specified
bounds on potential outcomes; and (iv) a matched study comparing two
non-randomized, possibly confounded treatment arms. We then conduct two
extensive simulation studies, one comparing the performance of each method in
many practical clinical settings and the other evaluating the usefulness of the
methods in ranking and advancing experimental therapies. We apply these methods
to an early-phase clinical trail, HIV Vaccine Trials Network Study 086 (HVTN
086), to showcase the usefulness of the methods
Hydrogenation and Hydro-Carbonation and Etching of Single-Walled Carbon Nanotubes
We present a systematic experimental investigation of the reactions between
hydrogen plasma and single-walled carbon nanotubes (SWNTs) at various
temperatures. Microscopy, infrared (IR) and Raman spectroscopy and electrical
transport measurements are carried out to investigate the properties of SWNTs
after hydrogenation. Structural deformations, drastically reduced electrical
conductance and increased semiconducting nature of SWNTs upon sidewall
hydrogenation are observed. These changes are reversible upon thermal annealing
at 500C via dehydrogenation. Harsh plasma or high temperature reactions lead to
etching of nanotube likely via hydro-carbonation. Smaller SWNTs are markedly
less stable against hydro-carbonation than larger tubes. The results are
fundamental and may have implications to basic and practical applications
including hydrogen storage, sensing, band-gap engineering for novel electronics
and new methods of manipulation, functionalization and etching of nanotubes.Comment: 3 pages, 4 figure
Simple spatial scaling rules behind complex cities
Although most of wealth and innovation have been the result of human interaction and cooperation, we are not yet able to quantitatively predict the spatial distributions of three main elements of cities: population, roads, and socioeconomic interactions. By a simple model mainly based on spatial attraction and matching growth mechanisms, we reveal that the spatial scaling rules of these three elements are in a consistent framework, which allows us to use any single observation to infer the others. All numerical and theoretical results are consistent with empirical data from ten representative cities. In addition, our model can also provide a general explanation of the origins of the universal super- and sub-linear aggregate scaling laws and accurately predict kilometre-level socioeconomic activity. Our work opens a new avenue for uncovering the evolution of cities in terms of the interplay among urban elements, and it has a broad range of applications.This work is supported by the National Natural Science Foundation of China under Grant Nos. 61673070, 61773069, 71731002 and the Fundamental Research Funds for the Central Universities with the Grant No. 2015KJJCB13, and also partially supported by NSF Grants PHY-1505000, CMMI-1125290, CHE-1213217, DTRA Grant HDTRA1-14-1-0017, DOE Grant DE-AC07-05Id14517. J.Z. acknowledges discussions with Prof. Bettencourt of the Santa Fe Institute, Dr. Lingfei Wu of Arizona State University, and Profs. Yougui Wang and Qinghua Chen of Beijing Normal University. R.L. acknowledges helpful discussions with and comments from Dr. Remi Louf in CASA, University College London, Dr. Longfeng Zhao from Huazhong (Central China) Normal University, and selfless help from Prof. Yougui Wang. R.L. is also supported by the Chinese Scholarship Council. (61673070 - National Natural Science Foundation of China; 61773069 - National Natural Science Foundation of China; 71731002 - National Natural Science Foundation of China; 2015KJJCB13 - Fundamental Research Funds for the Central Universities; PHY-1505000 - NSF; CMMI-1125290 - NSF; CHE-1213217 - NSF; HDTRA1-14-1-0017 - DTRA Grant; DE-AC07-05Id14517 - DOE; Chinese Scholarship Council)Published versio
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