1,384 research outputs found
Magnetotransport effects of ultrathin Ni80Fe20 films probed in-situ
We have investigated the magnetoresistance of Permalloy (Ni80Fe20) films with
thicknesses ranging from a single monolayer to 12 nm, grown on Al2O3, MgO and
SiO2 substrates. Growth and transport measurements were carried out under
cryogenic conditions in UHV. Applying in-plane magnetic vector fields up to 100
mT, the magnetotransport properties are ascertained during growth. With
increasing thickness the films exhibit a gradual transition from tunneling
magnetoresistance to anisotropic magnetoresistance. This corresponds to the
evolution of the film structure from separated small islands to a network of
interconnected grains as well as the transition from superparamagnetic to
ferromagnetic behavior of the film. Using an analysis based on a theoretical
model of the island growth, we find that the observed evolution of the
magnetoresistance in the tunneling regime originates from the changes in the
island size distribution during growth. Depending on the substrate material,
significant differences in the magnetoresistance response in the transition
regime between tunneling magnetoresistance and anisotropic magnetoresistance
were found. We attribute this to an increasingly pronounced island growth and
slower percolation process of Permalloy when comparing growth on SiO2, MgO and
Al2O3 substrates. The different growth characteristics result in a markedly
earlier onset of both tunneling magnetoresistance and anisotropic
magnetoresistance for SiO2. For Al2O3 in particular the growth mode results in
a structure of the film containing two different contributions to the
ferromagnetism which lead to two distinct coercive fields in the high thickness
regime.Comment: 8 pages, 7 figure
Flavourful portal for vector-like neutrino Dark Matter and
We discuss a flavourful portal model with a coupling to fourth-family
singlet Dirac neutrino dark matter. In the absence of mixing, the is
fermiophobic, having no couplings to the three chiral families, but does couple
to a fourth vector-like family. Due to mixing effects, the gets induced
couplings to second family left-handed lepton doublets and third family
left-handed quark doublets. This model can simultaneously account for the
measured -decay ratios and and for the observed relic
abundance of dark matter. We identify the parameter space where this
explanation is consistent with existing experimental constraints from dark
matter direct and indirect detection, LHC searches, and precision measurements
of flavour mixing and neutrino processes
Sublinear Distance Labeling
A distance labeling scheme labels the nodes of a graph with binary
strings such that, given the labels of any two nodes, one can determine the
distance in the graph between the two nodes by looking only at the labels. A
-preserving distance labeling scheme only returns precise distances between
pairs of nodes that are at distance at least from each other. In this paper
we consider distance labeling schemes for the classical case of unweighted
graphs with both directed and undirected edges.
We present a bit -preserving distance labeling
scheme, improving the previous bound by Bollob\'as et. al. [SIAM J. Discrete
Math. 2005]. We also give an almost matching lower bound of
. With our -preserving distance labeling scheme as a
building block, we additionally achieve the following results:
1. We present the first distance labeling scheme of size for sparse
graphs (and hence bounded degree graphs). This addresses an open problem by
Gavoille et. al. [J. Algo. 2004], hereby separating the complexity from
distance labeling in general graphs which require bits, Moon [Proc.
of Glasgow Math. Association 1965].
2. For approximate -additive labeling schemes, that return distances
within an additive error of we show a scheme of size for .
This improves on the current best bound of by
Alstrup et. al. [SODA 2016] for sub-polynomial , and is a generalization of
a result by Gawrychowski et al. [arXiv preprint 2015] who showed this for
.Comment: A preliminary version of this paper appeared at ESA'1
Near-Optimal Induced Universal Graphs for Bounded Degree Graphs
A graph is an induced universal graph for a family of graphs if every
graph in is a vertex-induced subgraph of . For the family of all
undirected graphs on vertices Alstrup, Kaplan, Thorup, and Zwick [STOC
2015] give an induced universal graph with vertices,
matching a lower bound by Moon [Proc. Glasgow Math. Assoc. 1965].
Let . Improving asymptotically on previous results by
Butler [Graphs and Combinatorics 2009] and Esperet, Arnaud and Ochem [IPL
2008], we give an induced universal graph with vertices for the family of graphs with vertices of maximum degree
. For constant , Butler gives a lower bound of
. For an odd constant , Esperet et al.
and Alon and Capalbo [SODA 2008] give a graph with
vertices. Using their techniques for any
(including constant) even values of gives asymptotically worse bounds than
we present.
For large , i.e. when , the previous best
upper bound was due to Adjiashvili and
Rotbart [ICALP 2014]. We give upper and lower bounds showing that the size is
. Hence the optimal size is
and our construction is within a factor of
from this. The previous results were
larger by at least a factor of .
As a part of the above, proving a conjecture by Esperet et al., we construct
an induced universal graph with vertices for the family of graphs with
max degree . In addition, we give results for acyclic graphs with max degree
and cycle graphs. Our results imply the first labeling schemes that for any
are at most bits from optimal
Widening participation students’ experience and perception of flipped learning statistics compared with traditional teaching in higher education
This paper presents data from a study comparing student experience and attainment when teaching statistics using Traditional Teaching (TT) and Flipped Learning (FL) approaches on a Foundation level module at a UK university. A survey of students’ experience and perception of FL was conducted at the end of the year. The results showed that the students liked the flexibility of FL and believed that studying asynchronously encouraged them to improve their independent learning skill and motivated them to search for more information for the subject, a finding broadly supported by other studies (Price and Walker, 2021). However, what was surprising, is that students believed they learned ‘better’ with TT than with FL, a perception supported by student overall attainment data. The study concludes that careful considerations must be made to make FL effective. These include the student demographic and their mathematics competency, the module contents and difficulty level. Otherwise, the use of FL may reduce students’ engagement and academic performance in Maths at Foundation level
Cdc53p acts in concert with Cdc4p and Cdc34p to control the G1 to S phase transition and identifies a conserved family of proteins
Regulation of cell cycle progression occurs in part through the targeted degradation of both activating and inhibitory subunits of the cyclin-dependent kinases. During G1, CDC4, encoding a WD-40 repeat protein, and CDC34, encoding a ubiquitin-conjugating enzyme, are involved in the destruction of these regulators. Here we describe evidence indicating that CDC53 also is involved in this process. Mutations in CDC53 cause a phenotype indistinguishable from those of cdc4 and cdc34 mutations, numerous genetic interactions are seen between these genes, and the encoded proteins are found physically associated in vivo. Cdc53p defines a large family of proteins found in yeasts, nematodes, and humans whose molecular functions are uncharacterized. These results suggest a role for this family of proteins in regulating cell cycle proliferation through protein degradation
Testosterone Influence on Gene Expression in Lacrimal Glands of Mouse Models of Sjögren Syndrome
Purpose:
Sjögren syndrome is an autoimmune disorder that occurs almost exclusively in women and is associated with extensive inflammation in lacrimal tissue, an immune-mediated destruction and/or dysfunction of glandular epithelial cells, and a significant decrease in aqueous tear secretion. We discovered that androgens suppress the inflammation in, and enhance the function of, lacrimal glands in female mouse models (e.g., MRL/MpJ-Tnfrsf6lpr [MRL/lpr]) of Sjögren syndrome. In contrast, others have reported that androgens induce an anomalous immunopathology in lacrimal glands of nonobese diabetic/LtJ (NOD) mice. We tested our hypothesis that these hormone actions reflect unique, strain- and tissue-specific effects, which involve significant changes in the expression of immune-related glandular genes.
Methods:
Lacrimal glands were obtained from age-matched, adult, female MRL/lpr and NOD mice after treatment with vehicle or testosterone for up to 3 weeks. Tissues were processed for analysis of differentially expressed mRNAs using CodeLink Bioarrays and Affymetrix GeneChips. Data were analyzed with bioinformatics and statistical software.
Results:
Testosterone significantly influenced the expression of numerous immune-related genes, ontologies, and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways in lacrimal glands of MRL/lpr and NOD mice. The nature of this hormone-induced immune response was dependent upon the autoimmune strain, and was not duplicated within lacrimal tissues of nonautoimmune BALB/c mice. The majority of immune-response genes regulated by testosterone were of the inflammatory type.
Conclusions:
Our findings support our hypothesis and indicate a major role for the lacrimal gland microenvironment in mediating androgen effects on immune gene expression
Nods, Nalps and Naip: intracellular regulators of bacterial-induced inflammation
The innate immune system is the most ancestral and ubiquitous system of defence against microbial infection. The microbial sensing proteins involved in innate immunity recognize conserved and often structural components of microorganisms. One class of these pattern-recognition molecules, the Toll-like receptors (TLRs), are involved in detection of microbes in the extracellular compartment whereas a newly discovered family of proteins, the NBS-LRR proteins (for nucleotide-binding site and leucine-rich repeat), are involved in intracellular recognition of microbes and their products. NBS-LRR proteins are characterized by three structural domains: a C-terminal leucine-rich repeat (LRR) domain able to sense a microbial motif, an intermediary nucleotide binding site (NBS) essential for the oligomerization of the molecule that is necessary for the signal transduction induced by different N-terminal effector motifs, such as a pyrin domain (PYD), a caspase-activating and recruitment domain (CARD) or a baculovirus inhibitor of apoptosis protein repeat (BIR) domain. Two of these family members, Nod1 and Nod2, play a role in the regulation of pro-inflammatory pathways through NF-κB induced by bacterial ligands. Recently, it was shown that Nod2 recognizes a specific peptidoglycan motif from bacteria, muramyl dipeptide (MDP). A surprising number of human genetic disorders have been linked to NBS-LRR proteins. For example, mutations in Nod2, which render the molecule insensitive to MDP and unable to induce NF-κB activation when stimulated, are associated with susceptibility to a chronic intestinal inflammatory disorder, Crohn's disease. Conversely, mutations in the NBS region of Nod2 induce a constitutive activation of NF-κB and are responsible for Blau syndrome, another auto-inflammatory disease. Nalp3, which is an NBS-LRR protein with an N-terminal Pyrin domain, is also implicated in rare auto-inflammatory disorders. In conclusion, NBS-LRR molecules appear as a new family of intracellular receptors of innate immunity able to detect specific bacterial compounds and induce inflammatory response; the dysregulation of these processes due to mutations in the genes encoding these proteins is involved in numerous auto-inflammatory disorders.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75732/1/j.1462-5822.2003.00304.x.pd
- …