44 research outputs found
Homotopical resolutions associated to deformable adjunctions
Given an adjunction connecting reasonable categories with weak equivalences,
we define a new derived bar and cobar construction associated to the
adjunction. This yields homotopical models of the completion and cocompletion
associated to the monad and comonad of the adjunction. We discuss applications
of these resolutions to spectral sequences for derived completions and
Goodwillie calculus in general model categories.Comment: 22 pages; v2 is the final journal version, with expository
improvements suggested by the refere
A universal characterization of higher algebraic K-theory
In this paper we establish a universal characterization of higher algebraic
K-theory in the setting of small stable infinity categories. Specifically, we
prove that connective algebraic K-theory is the universal additive invariant,
i.e., the universal functor with values in spectra which inverts Morita
equivalences, preserves filtered colimits, and satisfies Waldhausen's
additivity theorem. Similarly, we prove that non-connective algebraic K-theory
is the universal localizing invariant, i.e., the universal functor that
moreover satisfies the "Thomason-Trobaugh-Neeman" localization theorem.
To prove these results, we construct and study two stable infinity categories
of "noncommutative motives"; one associated to additivity and another to
localization. In these stable infinity categories, Waldhausen's S. construction
corresponds to the suspension functor and connective and non-connective
algebraic K-theory spectra become corepresentable by the noncommutative motive
of the sphere spectrum. In particular, the algebraic K-theory of every scheme,
stack, and ring spectrum can be recovered from these categories of
noncommutative motives.
In order to work with these categories of noncommutative motives, we
establish comparison theorems between the category of spectral categories
localized at the Morita equivalences and the category of small
idempotent-complete stable infinity categories. We also explain in detail the
comparison between the infinity categorical version of Waldhausen K-theory and
the classical definition.
As an application of our theory, we obtain a complete classification of the
natural transformations from higher algebraic K-theory to topological
Hochschild homology (THH) and topological cyclic homology (TC). Notably, we
obtain an elegant conceptual description of the cyclotomic trace map.Comment: Various revisions and correction
Type 2 diabetes mellitus and cerebrospinal fluid Alzheimer's disease biomarker amyloid β1-42 in Alzheimer's Disease Neuroimaging Initiative participants
Introduction
Type 2 diabetes mellitus (T2DM) is a risk factor for Alzheimer's disease. Cerebrospinal fluid (CSF) amyloid β (Aβ) 1-42 is an important Alzheimer's disease biomarker. However, it is inconclusive on how T2DM is related to CSF Aβ1-42.
Methods
Participants with T2DM were selected from the Alzheimer's Disease Neuroimaging Initiative by searching keywords from the medical history database. A two-way analysis of covariance model was used to analyze how T2DM associates with CSF Aβ1-42 or cerebral cortical Aβ.
Results
CSF Aβ1-42 was higher in the T2DM group than the nondiabetic group. The inverse relation between CSF Aβ1-42 and cerebral cortical Aβ was independent of T2DM status. Participants with T2DM had a lower cerebral cortical Aβ in anterior cingulate, precuneus, and temporal lobe than controls.
Discussion
T2DM is positively associated with CSF Aβ1-42 but negatively with cerebral cortical Aβ. The decreased cerebral cortical Aβ associated with T2DM is preferentially located in certain brain regions
Topological Hochschild homology of Thom spectra and the free loop space
We describe the topological Hochschild homology of ring spectra that arise as
Thom spectra for loop maps f: X->BF, where BF denotes the classifying space for
stable spherical fibrations. To do this, we consider symmetric monoidal models
of the category of spaces over BF and corresponding strong symmetric monoidal
Thom spectrum functors. Our main result identifies the topological Hochschild
homology as the Thom spectrum of a certain stable bundle over the free loop
space L(BX). This leads to explicit calculations of the topological Hochschild
homology for a large class of ring spectra, including all of the classical
cobordism spectra MO, MSO, MU, etc., and the Eilenberg-Mac Lane spectra HZ/p
and HZ.Comment: 58 page
Galois theory and Lubin-Tate cochains on classifying spaces
We consider brave new cochain extensions F(BG +,R) → F(EG +,R), where R is either a Lubin-Tate spectrum E n or the related 2-periodic Morava K-theory K n , and G is a finite group. When R is an Eilenberg-Mac Lane spectrum, in some good cases such an extension is a G-Galois extension in the sense of John Rognes, but not always faithful. We prove that for E n and K n these extensions are always faithful in the K n local category. However, for a cyclic p-group C p r, the cochain extension F(BC p r +,E n ) → F(EC p r +, E n ) is not a Galois extension because it ramifies. As a consequence, it follows that the E n -theory Eilenberg-Moore spectral sequence for G and BG does not always converge to its expected target
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Increasing phenological asynchrony between spring green-up and arrival of migratory birds
Consistent with a warming climate, birds are shifting the timing of their migrations, but it remains unclear to what extent these shifts have kept pace with the changing environment. Because bird migration is primarily cued by annually consistent physiological responses to photoperiod, but conditions at their breeding grounds depend on annually variable climate, bird arrival and climate-driven spring events would diverge. We combined satellite and citizen science data to estimate rates of change in phenological interval between spring green-up and migratory arrival for 48 breeding passerine species across North America. Both arrival and green-up changed over time, usually in the same direction (earlier or later). Although birds adjusted their arrival dates, 9 of 48 species did not keep pace with rapidly changing green-up and across all species the interval between arrival and green-up increased by over half a day per year. As green-up became earlier in the east, arrival of eastern breeding species increasingly lagged behind green-up, whereas in the west—where green-up typically became later—birds arrived increasingly earlier relative to green-up. Our results highlight that phenologies of species and trophic levels can shift at different rates, potentially leading to phenological mismatches with negative fitness consequences
Topological Andr\'e-Quillen homology for cellular commutative -algebras
Topological Andr\'e-Quillen homology for commutative -algebras was
introduced by Basterra following work of Kriz, and has been intensively studied
by several authors. In this paper we discuss it as a homology theory on CW
-algebras and apply it to obtain results on minimal atomic -local
-algebras which generalise those of Baker and May for -local spectra and
simply connected spaces. We exhibit some new examples of minimal atomic
-algebras.Comment: Final revision, a version will appear in Abhandlungen aus dem
Mathematischen Seminar der Universitaet Hambur
Lrp4 Mediates Bone Homeostasis and Mechanotransduction through Interaction with Sclerostin In Vivo
Wnt signaling plays a key role in regulating bone remodeling. In vitro studies suggest that sclerostin's inhibitory action on Lrp5 is facilitated by the membrane-associated receptor Lrp4. We generated an Lrp4 R1170W knockin mouse model (Lrp4KI), based on a published mutation in patients with high bone mass (HBM). Lrp4KI mice have an HBM phenotype (assessed radiographically), including increased bone strength and formation. Overexpression of a Sost transgene had osteopenic effects in Lrp4-WT but not Lrp4KI mice. Conversely, sclerostin inhibition had blunted osteoanabolic effects in Lrp4KI mice. In a disuse-induced bone wasting model, Lrp4KI mice exhibit significantly less bone loss than wild-type (WT) mice. In summary, mice harboring the Lrp4-R1170W missense mutation recapitulate the human HBM phenotype, are less sensitive to altered sclerostin levels, and are protected from disuse-induced bone loss. Lrp4 is an attractive target for pharmacological targeting aimed at increasing bone mass and preventing bone loss due to disuse
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BioTIME: A database of biodiversity time series for the Anthropocene.
MotivationThe BioTIME database contains raw data on species identities and abundances in ecological assemblages through time. These data enable users to calculate temporal trends in biodiversity within and amongst assemblages using a broad range of metrics. BioTIME is being developed as a community-led open-source database of biodiversity time series. Our goal is to accelerate and facilitate quantitative analysis of temporal patterns of biodiversity in the Anthropocene.Main types of variables includedThe database contains 8,777,413 species abundance records, from assemblages consistently sampled for a minimum of 2 years, which need not necessarily be consecutive. In addition, the database contains metadata relating to sampling methodology and contextual information about each record.Spatial location and grainBioTIME is a global database of 547,161 unique sampling locations spanning the marine, freshwater and terrestrial realms. Grain size varies across datasets from 0.0000000158 km2 (158 cm2) to 100 km2 (1,000,000,000,000 cm2).Time period and grainBioTIME records span from 1874 to 2016. The minimal temporal grain across all datasets in BioTIME is a year.Major taxa and level of measurementBioTIME includes data from 44,440 species across the plant and animal kingdoms, ranging from plants, plankton and terrestrial invertebrates to small and large vertebrates.Software format.csv and .SQL
Protein phosphatase 2A plays a crucial role in Giardia lamblia differentiation
Author Posting. © The Authors, 2006. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Molecular and Biochemical Parasitology 152 (2007): 80-89, doi:10.1016/j.molbiopara.2006.12.001.The ability of Giardia lamblia to undergo two distinct differentiations in
response to physiologic stimuli is central to its pathogenesis. The giardial
cytoskeleton changes drastically during encystation and excystation. However, the
signal transduction pathways mediating these transformations are poorly
understood. We tested the hypothesis that PP2A, a highly conserved
serine/threonine protein phosphatase, might be important in giardial differentiation.
We found that in vegetatively growing trophozoites, gPP2A-C protein localizes to
basal bodies/centrosomes, and to cytoskeletal structures unique to Giardia: the
ventral disk, and the dense rods of the anterior, posterior-lateral, and caudal
flagella. During encystation, gPP2A-C protein disappears from only the anterior
flagellar dense rods. During excystation, gPP2A-C localizes to the cyst wall in
excysting cysts but is not found in the wall of cysts with emerging excyzoites.
Transcriptome and immunoblot analyses indicated that gPP2A-C mRNA and
protein are upregulated in mature cysts and during the early stage of excystation
that models passage through the host stomach. Stable expression of gPP2A-C
antisense RNA did not affect vegetative growth, but strongly inhibited the
formation of encystation secretory vesicles (ESV) and water-resistant cysts.
Moreover, the few cysts that formed were highly defective in excystation.
Thus, gPP2A-C localizes to universal cytoskeletal structures and to
structures unique to Giardia. It is also important for encystation and excystation,
crucial giardial transformations that entail entry into and exit from dormancy.This work was funded
by NIH grants GM61896, AI51687, AI42488, and DK35108. Dr. A.G. McArthur was
supported by NIH grant AI51089 and the Marine Biological Laboratory’s Program
in Global Infectious Diseases, funded by the Ellison Medical Foundation