270 research outputs found
Spinless photon dark matter from two universal extra dimensions
We explore the properties of dark matter in theories with two universal extra
dimensions, where the lightest Kaluza-Klein state is a spin-0 neutral particle,
representing a six-dimensional photon polarized along the extra dimensions.
Annihilation of this 'spinless photon' proceeds predominantly through Higgs
boson exchange, and is largely independent of other Kaluza-Klein particles. The
measured relic abundance sets an upper limit on the spinless photon mass of 500
GeV, which decreases to almost 200 GeV if the Higgs boson is light. The
phenomenology of this dark matter candidate is strikingly different from
Kaluza-Klein dark matter in theories with one universal extra dimension.
Elastic scattering of the spinless photon with quarks is helicity suppressed,
making its direct detection challenging, although possible at upcoming
experiments. The prospects for indirect detection with gamma rays and
antimatter are similar to those of neutralinos. The rates predicted at neutrino
telescopes are below the sensitivity of next-generation experiments.Comment: 22 pages. Figure 7 corrected, leading to improved prospects for
direct detection. Some clarifying remarks include
Phenotypically distinct neutrophils patrol uninfected human and mouse lymph nodes.
Neutrophils play a key role in innate immunity. As the dominant circulating phagocyte, they are rapidly recruited from the bloodstream to sites of infection or injury to internalize and destroy microbes. More recently, neutrophils have been identified in uninfected organs, challenging the classical view of their function. Here we show that neutrophils were present in lymph nodes (LNs) in homeostasis. Using flow cytometry and confocal imaging, we identified neutrophils within LNs in naive, unchallenged mice, including LNs draining the skin, lungs, and gastrointestinal tract. Neutrophils were enriched within specific anatomical regions, in the interfollicular zone, a site of T cell activation. Intravital two-photon microscopy demonstrated that LN neutrophils were motile, trafficked into LNs from both blood and tissues via high endothelial venules and afferent lymphatics, respectively, and formed interactions with dendritic cells in LNs. Murine and human LN neutrophils had a distinct phenotype compared with circulating neutrophils, with higher major histocompatibility complex II (MHCII) expression, suggesting a potential role in CD4 T cell activation. Upon ex vivo stimulation with IgG immune complex (IC), neutrophils up-regulated expression of MHCII and costimulatory molecules and increased T cell activation. In vivo, neutrophils were capable of delivering circulating IC to LNs, suggesting a broader functional remit. Overall, our data challenge the perception that neutrophil patrol is limited to the circulation in homeostasis, adding LNs to their routine surveillance territory.L.S.C.L. was funded by Wellcome Trust (104384/Z/14/Z). M.R.C. is supported by National Institute of Health Research (NIHR) Cambridge Biomedical Research Centre, Chan-Zuckerburg Initiative Human Cell Atlas Technology Development Grant, Medical Research Council New Investigator Research Grant (MR/N024907/1), Arthritis Research UK Cure Challenge Research Grant (21777), and NIHR Research Professorship (RP-2017-08- ST2-002)
East Asia and the global/transatlantic/Western crisis
This paper introduces the special collection on East Asia and the Global Crisis. After justifying why a focus on East Asia is appropriate, it draws out the main themes that run through the individual contributions. These are the extent to which the region is decoupling from the global economy (or the West), the increasing legitimacy of statist alternatives to neoliberal development strategies, and the impact of crises on the definition of âregionâ and the functioning of regional institutions and governance mechanisms
Supersymmetry for Fermion Masses
It is proposed that supersymmetry (SUSY) maybe used to understand fermion
mass hierarchies. A family symmetry Z_{3L} is introduced, which is the cyclic
symmetry among the three generation SU(2) doublets. SUSY breaks at a high
energy scale ~ 10^{11} GeV. The electroweak energy scale ~ 100 GeV is
unnaturally small. No additional global symmetry, like the R-parity, is
imposed. The Yukawa couplings and R-parity violating couplings all take their
natural values which are about (10^0-10^{-2}). Under the family symmetry, only
the third generation charged fermions get their masses. This family symmetry is
broken in the soft SUSY breaking terms which result in a hierarchical pattern
of the fermion masses. It turns out that for the charged leptons, the tau mass
is from the Higgs vacuum expectation value (VEV) and the sneutrino VEVs, the
muon mass is due to the sneutrino VEVs, and the electron gains its mass due to
both Z_{3L} and SUSY breaking. The large neutrino mixing are produced with
neutralinos playing the partial role of right-handed neutrinos. |V_{e3}| which
is for nu_e-nu_{tau} mixing is expected to be about 0.1. For the quarks, the
third generation masses are from the Higgs VEVs, the second generation masses
are from quantum corrections, and the down quark mass due to the sneutrino
VEVs. It explains m_c/m_s, m_s/m_e, m_d > m_u and so on. Other aspects of the
model are discussed.Comment: 25 pages, 3 figures, revtex4; neutrino oscillation and many
discussions added, smallness of the electron mass due to supersymmetry
pointed out; v3: numerical errors correcte
Outside interference or Hong Kong embracing its unique identity? : The Chinese Universities Shakespeare Festival
Ongoing clashes between Hong Kong citizens and its government have foregrounded questions about outside interference in Hong Kongâs politics (largely from the government and media of Peopleâs Public of China), as well as debate about what institutions in Hong Kong are neo-colonial, heavily inflected with nostalgia for British colonialism, or in the process of being âcolonisedâ by the Peopleâs Republic of China. This article looks at Shakespeare in Hong Kong (and, to some extent, greater Chinese) theatre and education as one of those contested institutions, using the particular case of the now-defunct Chinese Universities Shakespeare Festival. The author probes their initial, surface impression of the festival as a simple outpouring of colonial sentiment and impulse, using its sizeable archives to realise a reading of the institution that highlights the complexities of international and intra-regional politics, culture and identity in Hong Kong and greater China. It builds on the Hong Kong literary critic Michael Inghamâs call for attention to Hong Kongâs quest â sometimes overt (as in the demonstrations of 2019), sometimes implicit (in the body of literature Ingham explores in his cultural and literary history) â for a unique, post-colonial identity that is inspired â but, critically, not confined â by its Chinese and British histories. The article briefly outlines the origins and set-up of the festival before juxtaposing the dominance of English language and culture in it with the opportunities it presents (seized by several teams) for intra-regional cooperation, competition and sharing diverse, greater Chinese cultures. The article offers a model for critically appraising other institutions and cultural products in Hong Kong in ways that resist easy binaries of British or Chinese, colonial or indigenous
Decreased MCM2-6 in Drosophila S2 cells does not generate significant DNA damage or cause a marked increase in sensitivity to replication interference.
A reduction in the level of some MCM proteins in human cancer cells (MCM5 in U20S cells or MCM3 in Hela cells) causes a rapid increase in the level of DNA damage under normal conditions of cell proliferation and a loss of viability when the cells are subjected to replication interference. Here we show that Drosophila S2 cells do not appear to show the same degree of sensitivity to MCM2-6 reduction. Under normal cell growth conditions a reduction of >95% in the levels of MCM3, 5, and 6 causes no significant short term alteration in the parameters of DNA replication or increase in DNA damage. MCM depleted cells challenged with HU do show a decrease in the density of replication forks compared to cells with normal levels of MCM proteins, but this produces no consistent change in the levels of DNA damage observed. In contrast a comparable reduction of MCM7 levels has marked effects on viability, replication parameters and DNA damage in the absence of HU treatment
The Gran Sasso muon puzzle
We carry out a time-series analysis of the combined data from three
experiments measuring the cosmic muon flux at the Gran Sasso laboratory, at a
depth of 3800 m.w.e. These data, taken by the MACRO, LVD and Borexino
experiments, span a period of over 20 years, and correspond to muons with a
threshold energy, at sea level, of around 1.3 TeV. We compare the best-fit
period and phase of the full muon data set with the combined DAMA/NaI and
DAMA/LIBRA data, which spans the same time period, as a test of the hypothesis
that the cosmic ray muon flux is responsible for the annual modulation detected
by DAMA. We find in the muon data a large-amplitude fluctuation with a period
of around one year, and a phase that is incompatible with that of the DAMA
modulation at 5.2 sigmas. Aside from this annual variation, the muon data also
contains a further significant modulation with a period between 10 and 11 years
and a power well above the 99.9% C.L threshold for noise, whose phase
corresponds well with the solar cycle: a surprising observation for such high
energy muons. We see no corresponding long-period oscillation in the
stratospheric temperature data.Comment: Minor changes and clarifications, matches version accepted at JCAP. 5
pages, 3 figure
Neutrino Mass from R-parity Violation in Split Supersymmetry
We investigate how the observed neutrino data can be accommodated by R-parity
violation in Split Supersymmetry. The atmospheric neutrino mass and mixing are
explained by the bilinear parameters inducing the neutrino-neutralino
mixing as in the usual low-energy supersymmetry. Among various one-loop
corrections, only the quark-squark exchanging diagrams involving the order-one
trilinear couplings can generate the solar neutrino mass
and mixing if the scalar mass is not larger than GeV. This scheme
requires an unpleasant hierarchical structure of the couplings, e.g.,
, and . On the other hand, the model has a distinct collider
signature of the lightest neutralino which can decay only to the final states,
and , arising from the bilinear mixing. Thus, the
measurement of the ratio; would provide a clean probe of the small reactor and
large atmospheric neutrino mixing angles as far as the neutralino mass is
larger than 62 GeV.Comment: 10 pages, 3 figures, version submitted to JHE
The OECD and phases in the international political economy, 1961â2011
In 2011, the OECD turned fifty. To provide a broad foundation for further thinking on this organization, we analyse its evolution over half a century from two perspectives: phases in the international political economy and the literature on IPE. By so doing, we uncover two paradoxes. Firstly, we find that the organizationâs evolution closely mirrored major phases in the postwar international political economy until recently. However, the OECDâs long-term dependence on theWest has now become an obstacle to its efforts to adapt to the latest phase, characterised by the rise of non-Western powers. Secondly, we show that, during the OECDâs âgolden ageâ, scholars paid relatively little attention to the organization but, from the 2000s, as the organization faced an unprecedented challenge of its potential economic decline, IPE literature on the organization blossomed
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