443 research outputs found
Evidence Of Dark Matter Annihilations In The WMAP Haze
The WMAP experiment has revealed an excess of microwave emission from the
region around the center of our Galaxy. It has been suggested that this signal,
known as the ``WMAP Haze'', could be synchrotron emission from relativistic
electrons and positrons generated in dark matter annihilations. In this letter,
we revisit this possibility. We find that the angular distribution of the WMAP
Haze matches the prediction for dark matter annihilations with a cusped density
profile, in the inner kiloparsecs. Comparing the
intensity in different WMAP frequency bands, we find that a wide range of
possible WIMP annihilation modes are consistent with the spectrum of the haze
for a WIMP with a mass in the 100 GeV to multi-TeV range. Most interestingly,
we find that to generate the observed intensity of the haze, the dark matter
annihilation cross section is required to be approximately equal to the value
needed for a thermal relic, cm/s. No
boost factors are required. If dark matter annihilations are in fact
responsible for the WMAP Haze, and the slope of the halo profile continues into
the inner Galaxy, GLAST is expected to detect gamma rays from the dark matter
annihilations in the Galactic Center if the WIMP mass is less than several
hundred GeV.Comment: 4 pages, 3 figure
Prospects For Detecting Dark Matter With GLAST In Light Of The WMAP Haze
Observations by the WMAP experiment have identified an excess of microwave
emission from the center of the Milky Way. It has previously been shown that
this "WMAP Haze" could be synchrotron emission from relativistic electrons and
positrons produced in the annihilations of dark matter particles. In
particular, the intensity, spectrum and angular distribution of the WMAP Haze
is consistent with an electroweak scale dark matter particle (such as a
supersymmetric neutralino or Kaluza-Klein dark matter in models with universal
extra dimensions) annihilating with a cross section on the order of sigma
v~3x10^-26 cm^3/s and distributed with a cusped halo profile. No further exotic
astrophysical or annihilation boost factors are required. If dark matter
annihilations are in fact responsible for the observed Haze, then other
annihilation products will also be produced, including gamma rays. In this
article, we study the prospects for the GLAST satellite to detect gamma rays
from dark matter annihilations in the Galactic Center region in this scenario.
We find that by studying only the inner 0.1 degrees around the Galactic Center,
GLAST will be able to detect dark matter annihilating to heavy quarks or gauge
bosons over astrophysical backgrounds with 5sigma (3sigma) significance if they
are lighter than approximately 320-500 GeV (500-750 GeV). If the angular window
is broadened to study the dark matter halo profile's angular extension (while
simultaneously reducing the astrophysical backgrounds), WIMPs as heavy as
several TeV can be identified by GLAST with high significance. Only if the dark
matter particles annihilate mostly to electrons or muons will GLAST be unable
to identify the gamma ray spectrum associated with the WMAP Haze.Comment: 10 pages, 6 figure
Biologically active natural products from South African marine invertebrates
This thesis describes the chemical and biological investigation of the extracts of six different marine invertebrate organisms collected along the South African coastline. The work on these extracts has resulted in the isolation and structural elucidation of twenty-one previously undescribed secondary metabolites; The history of marine natural product chemistry in South Africa has not previously been reviewed and so a comprehensive review covering the literature from the 1940's up until the end of 1995 is presented here. The marine ascidian Pseudodistoma species collected in the Tsitsikamma Marine Reserve was shown to contain four new unsaturated amino alcohols [47], [48], [49] and [50] which were isolated as their acetyl derivatives. These compounds exhibited strong antimicrobial activity. Four new pyrroloiminoquinone alkaloids, the tsitsikammamines A [90] to D [93],were isolated from a new genus of Latrunculid sponge collected in the Tsitsikamma Marine Reserve. These highly pigmented compounds also possessed strong antimicrobial activity. An investigation of two phenotypic colour variants of the soft coral Capnella thyrsoidea resulted in the isolation of the known steroid 5α-pregna-1, 20-dien-3-one [97] and an additional six new metabolites, 16β-hydroxy-5α-pregna-1 ,20-dien-3-one 16-acetate [98], 3α,16β-dihydroxy-5α-pregna-1, 20-diene 3,16-diacetate [99] and four xenicane diterpenes, the tsitsixenicins A [100] to D [103]. This is the first reported isolation of xenicane diterpenes from the soft coral family Nephtheiidae. Tsitsixenicin A and B showed good anti-inflammatory activity by inhibiting superoxide production in both rabbit and human cell neutrophils. A further four new metabolites were isolated from two soft corals which could only be identified to the genus level and were designated Alcyonium species A and species B. Alcyonium species A was collected in the Tsitsikamma Marine Reserve and yielded two new polyhydroxysterols, cholest-5-ene-3β, 7β, 19-triol 19-acetate [121] and cholest-5,24-diene-3β, 7β, 19-triol 19-acetate [122]. The soft coral Alcyonium species B was collected off Aliwal Shoal and was found to contain two known xenicane diterpenes, 9-deacetoxy-14, 15-deepoxyxeniculin [110] and zahavin A [16], and two new xenicane diterpenes, 7 -epoxyzahavin A [123] and xeniolide C [124]. Compounds [110], [16] and [123] exhibited strong anti-inflammatory activity and compounds [110] and [16] showed good antithrombotic activity. The endemic soft coral A/cyanium fauri collected at Riet Point near Port Alfred yielded the new sesquiterpene hydroquinone rietone [141] in high yierd, fogether with the minor compounds 8'-acetoxyrietone [142] and 8'-desoxyrietone [143]. Rietone exhibited moderate activity in the NCl's in-vitro anti-HIV bioassays
Trustworthy Cross-Border Interoperable Identity System for Developing Countries
Foundational identity systems (FIDS) have been used to optimise service
delivery and inclusive economic growth in developing countries. As developing
nations increasingly seek to use FIDS for the identification and authentication
of identity (ID) holders, trustworthy interoperability will help to develop a
cross-border dimension of e-Government. Despite this potential, there has not
been any significant research on the interoperability of FIDS in the African
identity ecosystem. There are several challenges to this; on one hand, complex
internal political dynamics have resulted in weak institutions, implying that
FIDS could be exploited for political gains. On the other hand, the trust in
the government by the citizens or ID holders is habitually low, in which case,
data security and privacy protection concerns become paramount. In the same
sense, some FIDS are technology-locked, thus interoperability is primarily
ambiguous. There are also issues of cross-system compatibility, legislation,
vendor-locked system design principles and unclear regulatory provisions for
data sharing. Fundamentally, interoperability is an essential prerequisite for
e-Government services and underpins optimal service delivery in education,
social security, and financial services including gender and equality as
already demonstrated by the European Union. Furthermore, cohesive data exchange
through an interoperable identity system will create an ecosystem of efficient
data governance and the integration of cross-border FIDS. Consequently, this
research identifies the challenges, opportunities, and requirements for
cross-border interoperability in an African context. Our findings show that
interoperability in the African identity ecosystem is vital to strengthen the
seamless authentication and verification of ID holders for inclusive economic
growth and widen the dimensions of e-Government across the continent.Comment: 18 pages, 4 figures, In 2023 Trustworthy Digital Identity
International Conference, Bengaluru, Indi
Atomic tiles: Manipulative resources for exploring bonding and molecular structure
A simple manipulative resource, Atomic Tiles, is described for scaffolding the learning of Lewis structures without using algorithmic, rule-based methods of drawing. Students use Atomic Tiles to (1) create models of bonding that lead to drawing Lewis structures, (2) use the structures they create to infer patterns required for rational structures and common organic functional groups, (3) translate between Lewis structures and molecular models, and (4) use molecular models to identify isomers
Recommended from our members
Prospects for detecting dark matter with GLAST in light of the WMAP haze
Observations by the WMAP experiment have identified an excess of microwave emission from the center of the Milky Way. It has previously been shown that this "WMAP Haze" could be synchrotron emission from relativistic electrons and positrons produced in the annihilations of dark matter particles. In particular, the intensity, spectrum and angular distribution of the WMAP Haze is consistent with an electroweak scale dark matter particle (such as a supersymmetric neutralino or Kaluza-Klein dark matter in models with universal extra dimensions) annihilating with a cross section on the order of sigma v~3x10^-26 cm^3/s and distributed with a cusped halo profile. No further exotic astrophysical or annihilation boost factors are required. If dark matter annihilations are in fact responsible for the observed Haze, then other annihilation products will also be produced, including gamma rays. In this article, we study the prospects for the GLAST satellite to detect gamma rays from dark matter annihilations in the Galactic Center region in this scenario. We find that by studying only the inner 0.1 degrees around the Galactic Center, GLAST will be able to detect dark matter annihilating to heavy quarks or gauge bosons over astrophysical backgrounds with 5sigma (3sigma) significance if they are lighter than approximately 320-500 GeV (500-750 GeV). If the angular window is broadened to study the dark matter halo profile's angular extension (while simultaneously reducing the astrophysical backgrounds), WIMPs as heavy as several TeV can be identified by GLAST with high significance. Only if the dark matter particles annihilate mostly to electrons or muons will GLAST be unable to identify the gamma ray spectrum associated with the WMAP Haze.Astronom
Control of Biohazards: A High Performance Energetic Polycyclized Iodine-Containing Biocide
The article of record as published may be found at http://dx.doi.org/10.1021/acs.inorgchem.8b01600Biohazards and chemical hazards as well as radioactive hazards have always been a threat to human health. The search for solutions to these problems is an ongoing worldwide effort. In order to control biohazards by chemical methods, a synthetically useful fused tricyclic iodine-rich compound, 2,6-diiodo-3,5-dinitro-4,9-dihydrodipyrazolo [1,5a:5',1'-d][1,3,5]triazine (5), with good detonation performance was synthesized, characterized, and its properties determined. This compound which acts as an agent defeat weapon has been shown to destroy certain microorganisms effectively by releasing iodine after undergoing decomposition or combustion. The small iodine residues remaining will not be deleterious to human life after 1 month.Financial support of the Office of Naval Research (N00014-16- 1-2089), and the Defense Threat Reduction Agency (HDTRA 1-15-1-0028) is gratefully acknowledged. The M. J. Murdock Charitable Trust (No. 2014120) is thanked for funds supporting the purchase of a 500 MHz NMR.Financial support of the Office of Naval Research (N00014-16- 1-2089), and the Defense Threat Reduction Agency (HDTRA 1-15-1-0028) is gratefully acknowledged. The M. J. Murdock Charitable Trust (No. 2014120) is thanked for funds supporting the purchase of a 500 MHz NMR
Determining Histories of Slip on Normal Faults With Bedrock Scarps Using Cosmogenic Nuclide Exposure Data
Cosmogenic exposure data can be used to calculate time-varying fault slip rates on normal faults with exposed bedrock scarps. The method relies on assumptions related to how the scarp is preserved, which should be consistent at multiple locations along the same fault. Previous work commonly relied on cosmogenic data from a single sample locality to determine the slip rate of a fault. Here we show that by applying strict sampling criteria and using geologically informed modeling parameters in a Bayesian-inference Markov chain Monte Carlo method, similar patterns of slip rate changes can be modeled at multiple sites on the same fault. Consequently, cosmogenic data can be used to resolve along-strike fault activity. We present cosmogenic 36Cl concentrations from seven sites on two faults in the Italian Apennines. The average slip rate varies between sites on the Campo Felice Fault (0.84 ± 0.23 to 1.61 ± 0.27 mm yr−1), and all sites experienced a period of higher than average slip rate between 0.5 and 2 ka and a period of lower than average slip rate before 3 ka. On the Roccapreturo fault, slip rate in the center of the fault is 0.55 ± 0.11 and 0.35 ± 0.05 mm yr−1 at the fault tip near a relay zone. The estimated time since the last earthquake is the same at each site along the same fault (631 ± 620 years at Campo Felice and 2,603 ± 1,355 years at Roccapreturo). These results highlight the potential for cosmogenic exposure data to reveal the detailed millennial history of earthquake slip on active normal faults
Temporal changes in innate immune signals in a rat model of alcohol withdrawal in emotional and cardiorespiratory homeostatic nuclei.
BACKGROUND: Chronic alcohol use changes the brain\u27s inflammatory state. However, there is little work examining the progression of the cytokine response during alcohol withdrawal, a period of profound autonomic and emotional upset. This study examines the inflammatory response in the central nucleus of the amygdala (CeA) and dorsal vagal complex (DVC), brain regions neuroanatomically associated with affective and cardiorespiratory regulation in an in vivo rat model of withdrawal following a single chronic exposure.
METHODS: For qRT-PCR studies, we measured the expression of TNF-α, NOS-2, Ccl2 (MCP-1), MHC II invariant chain CD74, and the TNF receptor Tnfrsf1a in CeA and DVC samples from adult male rats exposed to a liquid alcohol diet for thirty-five days and in similarly treated animals at four hours and forty-eight hours following alcohol withdrawal. ANOVA was used to identify statistically significant treatment effects. Immunohistochemistry (IHC) and confocal microscopy were performed in a second set of animals during chronic alcohol exposure and subsequent 48-hour withdrawal.
RESULTS: Following a chronic alcohol exposure, withdrawal resulted in a statistically significant increase in the expression of mRNAs specific for innate immune markers Ccl2, TNF-α, NOS-2, Tnfrsf1a, and CD74. This response was present in both the CeA and DVC and most prominent at 48 hours. Confocal IHC of samples taken 48 hours into withdrawal demonstrate the presence of TNF-α staining surrounding cells expressing the neural marker NeuN and endothelial cells colabeled with ICAM-1 (CD54) and RECA-1, markers associated with an inflammatory response. Again, findings were consistent in both brain regions.
CONCLUSIONS: This study demonstrates the rapid induction of Ccl2, TNF-α, NOS-2, Tnfrsf1a and CD74 expression during alcohol withdrawal in both the CeA and DVC. IHC dual labeling showed an increase in TNF-α surrounding neurons and ICAM-1 on vascular endothelial cells 48 hours into withdrawal, confirming the inflammatory response at the protein level. These findings suggest that an abrupt cessation of alcohol intake leads to an acute central nervous system (CNS) inflammatory response in these regions that regulate autonomic and emotional state
- …