2,093 research outputs found
Search for energetic cosmic axions utilizing terrestrial/celestial magnetic fields
Orbiting -detectors combined with the magnetic field of the Earth or
the Sun can work parasitically as cosmic axion telescopes. The relatively short
field lengths allow the axion-to-photon conversion to be coherent for
eV, if the axion kinetic energy is above
keV (Earth's field), or, MeV (Sun's field), allowing thus to search
for axions from annihilations, from supernova explosions, etc. With a
detector angular resolution of , a more efficient sky survey for
energetic cosmic axions passing {\it through the Sun} can be performed. Axions
or other axion-like particles might be created by the interaction of the cosmic
radiation with the Sun, similarly to the axion searches in accelerator beam
dump experiments; the enormous cosmic energy combined with the built-in
coherent Primakoff effect might provide a sensitive detection scheme, being out
of reach with accelerators. The axion signal will be an excess in -rays
coming either from a specific celestial place behind the Sun, e.g. the Galactic
Center, or, from any other direction in the sky being associated with a violent
astrophysical event, e.g. a supernova. Earth bound detectors are also of
potential interest. The axion scenario also applies to other stars or binary
systems in the Universe, in particular to those with superstrong magnetic
fields.Comment: 9 pages, LaTeX, small changes in text and bibliograph
Recommended from our members
Data assurance in opaque computations
The chess endgame is increasingly being seen through the lens of, and therefore effectively defined by, a data âmodelâ of itself. It is vital that such models are clearly faithful to the reality they purport to represent. This paper examines that issue and systems engineering responses to it, using the chess endgame as the exemplar scenario. A structured survey has been carried out of the intrinsic challenges and complexity of creating endgame data by reviewing the past pattern of errors during work in progress, surfacing in publications and occurring after the data was generated. Specific measures are proposed to counter observed classes of error-risk, including a preliminary survey of techniques for using state-of-the-art verification tools to generate EGTs that are correct by construction. The approach may be applied generically beyond the game domain
Status of inshore demersal scalefish stocks on the south coast of Western Australia. NRM Project 12034 Final Report
Inshore demersal scalefish in waters of 20-250 m depth in the South Coast Bioregion (SCB) are an important resource targeted by commercial, recreational and charter fishing sectors
Brachial artery characteristics and micro-vascular filtration capacity in rock climbers
Rock climbers perform repeated isometric forearm muscle contractions subjecting the vasculature to repeated ischaemia and distorted haemodynamic signals. This study investigated forearm vascular characteristics in rock climbers compared to healthy untrained controls. Eight climbers (CLIMB) (BMI; 22.3, s = 2.0 kg/m2, isometric handgrip strength; 46, s = 8 kg) were compared against eight untrained controls (CON) (BMI; 23.8, s = 2.6 kg/m2, isometric handgrip strength; 37, s = 9 kg). Brachial artery diameter and blood flow were measured, using Doppler ultrasound, at rest and following 5-mins ischaemia (peak diameter) and ischaemic exercise (maximal dilation) to calculate flow mediated dilation (FMD) and dilatory capacity (DC). Capillary filtration capacity was assessed using venous occlusion plethysmography. Resting (4.30, s = 0.26 vs. 3.79, s = 0.39 mm), peak (4.67, s = 0.31 vs. 4.12, s = 0.45 mm) and maximal (5.14, s = 0.42 vs. 4.35, s = 0.47 mm) diameters were greater (P < 0.05) in CLIMB than CON, respectively, despite no difference in FMD (9.2, s = 2.6 vs. 8.7, s = 2.9%). Peak reactive hyperaemic blood flow (1136, s = 504 vs. 651, s = 221 ml/min) and capillary filtration capacity (3.8, s = 0.9 vs. 5.2, s = 0.7 ml.minâ1.mmHgâ1.100 ml tissueâ1 Ă 10â3) were greater (P < 0.05) in CLIMB compared to CON, respectively. Rock climbers exhibit structural vascular adaptation compared to untrained control participants but have similar vascular function. This may contribute to the enhanced ability of climbers to perform repeated isometric contractions
Very high precision bound state spectroscopy near a Rb Feshbach resonance
We precisely measured the binding energy of a molecular state near the
Feshbach resonance in a Rb Bose-Einstein condensate (BEC). Rapid
magnetic field pulses induced coherent atom-molecule oscillations in the BEC.
We measured the oscillation frequency as a function of B-field and fit the data
to a coupled-channels model. Our analysis constrained the Feshbach resonance
position [155.041(18) G], width [10.71(2) G], and background scattering length
[-443(3) a] and yielded new values for , , and . These
results improved our estimate for the stability condition of an attractive BEC.
We also found evidence for a mean-field shift to the binding energy.Comment: 5 pages, 2 figures, submitted to PR
The mediating effect of task presentation on collaboration and children's acquisition of scientific reasoning
There has been considerable research concerning peer interaction and the acquisition of children's scientific reasoning. This study investigated differences in collaborative activity between pairs of children working around a computer with pairs of children working with physical apparatus and related any differences to the development of children's scientific reasoning. Children aged between 9 and 10 years old (48 boys and 48 girls) were placed into either same ability or mixed ability pairs according to their individual, pre-test performance on a scientific reasoning task. These pairs then worked on either a computer version or a physical version of Inhelder and Piaget's (1958) chemical combination task. Type of presentation was found to mediate the nature and type of collaborative activity. The mixed-ability pairs working around the computer talked proportionally more about the task and management of the task; had proportionally more transactive discussions and used the record more productively than children working with the physical apparatus. Type of presentation was also found to mediated children's learning. Children in same ability pairs who worked with the physical apparatus improved significantly more than same ability pairs who worked around the computer. These findings were partially predicted from a socio-cultural theory and show the importance of tools for mediating collaborative activity and collaborative learning
Excited Baryons in Lattice QCD
We present first results for the masses of positive and negative parity
excited baryons calculated in lattice QCD using an O(a^2)-improved gluon action
and a fat-link irrelevant clover (FLIC) fermion action in which only the
irrelevant operators are constructed with APE-smeared links. The results are in
agreement with earlier calculations of N^* resonances using improved actions
and exhibit a clear mass splitting between the nucleon and its chiral partner.
An correlation matrix analysis reveals two low-lying J^P=(1/2)^- states with a
small mass splitting. The study of different Lambda interpolating fields
suggests a similar splitting between the lowest two Lambda1/2^- octet states.
However, the empirical mass suppression of the Lambda^*(1405) is not evident in
these quenched QCD simulations, suggesting a potentially important role for the
meson cloud of the Lambda^*(1405) and/or a need for more exotic interpolating
fields.Comment: Correlation matrix analysis performed. Increased to 400
configurations. 22 pages, 13 figures, 15 table
The McKean-Vlasov Equation in Finite Volume
We study the McKean--Vlasov equation on the finite tori of length scale
in --dimensions. We derive the necessary and sufficient conditions for the
existence of a phase transition, which are based on the criteria first
uncovered in \cite{GP} and \cite{KM}. Therein and in subsequent works, one
finds indications pointing to critical transitions at a particular model
dependent value, of the interaction parameter. We show that
the uniform density (which may be interpreted as the liquid phase) is
dynamically stable for and prove, abstractly, that a
{\it critical} transition must occur at . However for
this system we show that under generic conditions -- large, and
isotropic interactions -- the phase transition is in fact discontinuous and
occurs at some \theta\t < \theta^{\sharp}. Finally, for H--stable, bounded
interactions with discontinuous transitions we show that, with suitable
scaling, the \theta\t(L) tend to a definitive non--trivial limit as
Prospective Registry Trial Assessing the Use of Magnetic Seeds to Locate Clipped Nodes After Neoadjuvant Chemotherapy for Breast Cancer Patients
Background Targeted axillary dissection (TAD) involves locating and removing both clipped nodes and sentinel nodes for assessment of the axillary response to neoadjuvant chemotherapy (NAC) by clinically node-positive breast cancer patients. Initial reports described radioactive seeds used for localization, which makes the technique difficult to implement in some settings. This trial was performed to determine whether magnetic seeds can be used to locate clipped axillary lymph nodes for removal. Methods This prospective registry trial enrolled patients who had biopsy-proven node-positive disease with a clip placed in the node and treatment with NAC. A magnetic seed was placed under ultrasound guidance in the clipped node after NAC. All the patients underwent TAD. Results Magnetic seeds were placed in 50 patients by 17 breast radiologists. All the patients had successful seed placement at the first attempt (mean time for localization was 6.1 min; range 1-30 min). The final position of the magnetic seed was within the node (n = 44, 88%), in the cortex (n = 3, 6%), less than 3 mm from the node (n = 2, 4%), or by the clip when the node could not be adequately visualized (n = 1, 2%). The magnetic seed was retrieved at surgery from all the patients. In 49 (98%) of the 50 cases, the clip and magnetic seed were retrieved from the same node. Surgeons rated the transcutaneous and intraoperative localization as easy for 43 (86%) of the 50 cases. No device-related adverse events occurred. Conclusions Localization and selective removal of clipped nodes can be accomplished safely and effectively using magnetic seeds
Current trials to reduce surgical intervention in ductal carcinoma in situ of the breast: critical review
The high proportion of ductal carcinoma in situ (DCIS) presented in mammographic screening and the relatively low risk of progression to invasive disease have raised questions related to overtreatment. Following a review of current DCIS management protocols a more conservative approach has been suggested. Clinical trials have been introduced to evaluate the option of avoiding surgical intervention in a proportion of patients with DCIS defined as âlow-riskâ using certain clinicopathological criteria. These trials can potentially provide evidence-based models of active surveillance (with or without endocrine therapy) as a future management approach. Despite the undisputable fact of our need to address the obvious overtreatment of screen-detected DCIS, some important questions need to be considered regarding these trials including the eligibility criteria and definition of risk, the proportion of patient eligible for inclusion, and the length of time required for proper analysis of the trials' outcome in view of the long-term natural history of DCIS progression particularly the low-risk group. These factors can potentially affect the practicality and future impact of such trials. This review provides critical analysis of current DCIS management trials and highlights critical issues related to their practicality and the expected outcome
- âŠ