1,241 research outputs found
Using Forbush decreases to derive the transit time of ICMEs propagating from 1 AU to Mars
The propagation of 15 interplanetary coronal mass ejections (ICMEs) from
Earth's orbit (1 AU) to Mars (~ 1.5 AU) has been studied with their propagation
speed estimated from both measurements and simulations. The enhancement of
magnetic fields related to ICMEs and their shock fronts cause the so-called
Forbush decrease, which can be de- tected as a reduction of galactic cosmic
rays measured on-ground. We have used galactic cosmic ray (GCR) data from
in-situ measurements at Earth, from both STEREO A and B as well as GCR
measurements by the Radiation Assessment Detector (RAD) instrument onboard Mars
Science Laboratory (MSL) on the surface of Mars. A set of ICME events has been
selected during the periods when Earth (or STEREO A or B) and Mars locations
were nearly aligned on the same side of the Sun in the ecliptic plane
(so-called opposition phase). Such lineups allow us to estimate the ICMEs'
transit times between 1 and 1.5 AU by estimating the delay time of the
corresponding Forbush decreases measured at each location. We investigate the
evolution of their propagation speeds before and after passing Earth's orbit
and find that the deceleration of ICMEs due to their interaction with the
ambient solar wind may continue beyond 1 AU. We also find a substantial
variance of the speed evolution among different events revealing the dynamic
and diverse nature of eruptive solar events. Furthermore, the results are
compared to simulation data obtained from two CME propagation models, namely
the Drag-Based Model and ENLIL plus cone model
Staging of endometrial cancer with MRI: Guidelines of the European Society of Urogenital Imaging
The purpose of this study was to define guidelines for endometrial cancer staging with MRI. The technique included critical review and expert consensus of MRI protocols by the female imaging subcommittee of the European Society of Urogenital Radiology, from ten European institutions, and published literature between 1999 and 2008. The results indicated that high field MRI should include at least two T2-weighted sequences in sagittal, axial oblique or coronal oblique orientation (short and long axis of the uterine body) of the pelvic content. High-resolution post-contrast images acquired at 2min ± 30 s after intravenous contrast injection are suggested to be optimal for the diagnosis of myometrial invasion. If cervical invasion is suspected, additional slice orientation perpendicular to the axis of the endocervical channel is recommended. Due to the limited sensitivity of MRI to detect lymph node metastasis without lymph node-specific contrast agents, retroperitoneal lymph node screening with pre-contrast sequences up to the level of the kidneys is optional. The likelihood of lymph node invasion and the need for staging lymphadenectomy are also indicated by high-grade histology at endometrial tissue sampling and by deep myometrial or cervical invasion detected by MRI. In conclusion, expert consensus and literature review lead to an optimized MRI protocol to stage endometrial cance
Curvature-coupling dependence of membrane protein diffusion coefficients
We consider the lateral diffusion of a protein interacting with the curvature
of the membrane. The interaction energy is minimized if the particle is at a
membrane position with a certain curvature that agrees with the spontaneous
curvature of the particle. We employ stochastic simulations that take into
account both the thermal fluctuations of the membrane and the diffusive
behavior of the particle. In this study we neglect the influence of the
particle on the membrane dynamics, thus the membrane dynamics agrees with that
of a freely fluctuating membrane. Overall, we find that this curvature-coupling
substantially enhances the diffusion coefficient. We compare the ratio of the
projected or measured diffusion coefficient and the free intramembrane
diffusion coefficient, which is a parameter of the simulations, with analytical
results that rely on several approximations. We find that the simulations
always lead to a somewhat smaller diffusion coefficient than our analytical
approach. A detailed study of the correlations of the forces acting on the
particle indicates that the diffusing inclusion tries to follow favorable
positions on the membrane, such that forces along the trajectory are on average
smaller than they would be for random particle positions.Comment: 16 pages, 8 figure
"Safe" Coulomb Excitation of 30Mg
We report on the first radioactive beam experiment performed at the recently
commissioned REX-ISOLDE facility at CERN in conjunction with the highly
efficient gamma spectrometer MINIBALL. Using 30Mg ions accelerated to an energy
of 2.25 MeV/u together with a thin nat-Ni target, Coulomb excitation of the
first excited 2+ states of the projectile and target nuclei well below the
Coulomb barrier was observed. From the measured relative de-excitation gamma
ray yields the B(E2; 0+ -> 2+) value of 30Mg was determined to be 241(31)
e2fm4. Our result is lower than values obtained at projectile fragmentation
facilities using the intermediate-energy Coulomb excitation method, and
confirms the theoretical conjecture that the neutron-rich magnesium isotope
30Mg lies still outside the ``island of inversion''
Nuclear data from AMS & nuclear data for AMS - some examples
We summarize some recent cross-section measurements using accelerator mass spectrometry (AMS). AMS represents an ultra-sensitive technique for measuring a limited, but steadily increasing number of longer-lived radionuclides. This method implies a two-step procedure with sample activation and subsequent AMS measurement. Applications include nuclear astrophysics, nuclear technology (nuclear fusion, nuclear fission and advanced reactor concepts and radiation dose estimations). A series of additional applications involves cosmogenic radionuclides in environmental, geological and extraterrestrial studies. Lack of information exists for a list of nuclides as pointed out by nuclear data requests. An overview of some recent measurements is given and the method is exemplified for some specific neutron-induced reactions.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard
Recommended from our members
Cobalt and nickel uptake by silica-based extractants
The pKas of ethyl/butyl phosphonate silica (EBP-Si) have been determined, and the removal of cobalt and nickel from solution was investigated as a function of various parameters and compared with those of Purolite S950. pH uptake experiments suggested a combination of ion exchange and acid dissociation of the surface occurring. Isotherm data, fitted using the Langmuir and Dubinin–Radushkevich (D-R) models, indicated that stronger complexes formed with S950 than with EBP-Si. Kinetic data, fitted using a pseudo-second-order model, suggested that the rate-determining process is the reaction of metal ions with the chelating functionality of the resin. Uptake by EBP-Si is two to three times faster than that on S950
REX-ISOLDE: post-accelerated radioactive BEAMS at CERN-ISOLDE
The ISOLDE RIB-facility at CERN has today been producing a vast range of radioactive beams since more than 30 years. The low-energy beams of ISOLDE will be complemented by a post-accelerator, REX-ISOLDE, currently being assembled. In order to convert the pseudo-DC, singly-charged beam from the ISOLDE mass separators into a cooled and bunched beam at higher charge states a novel scheme of trapping, cooling and charge-state breeding has been devised, using a linear Penning trap and an Electron Beam Ion Source (EBIS). This allows for subsequent acceleration by a short, cost-effective LINAC consisting of an RFQ, an IH-structure and three seven-gap resonators, reaching 0.8 - 2.2 MeV/u. The installation of REX-ISOLDE is well underway and the first post-accelerated radioactive beams are expected to be obtained during late 2000
Common variants at 2q11.2, 8q21.3, and 11q13.2 are associated with major mood disorders
Bipolar disorder (BPD) and major depressive disorder (MDD) are primary major mood disorders. Recent studies suggest that they share certain psychopathological features and common risk genes, but unraveling the full genetic architecture underlying the risk of major mood disorders remains an important scientific task. The public genome-wide association study (GWAS) data sets offer the opportunity to examine this topic by utilizing large amounts of combined genetic data, which should ultimately allow a better understanding of the onset and development of these illnesses. Genome-wide meta-analysis was performed by combining two GWAS data sets on BPD and MDD (19,637 cases and 18,083 controls), followed by replication analyses for the loci of interest in independent 12,364 cases and 76,633 controls from additional samples that were not included in the two GWAS data sets. The single-nucleotide polymorphism (SNP) rs10791889 at 11q13.2 was significant in both discovery and replication samples. When combining all samples, this SNP and multiple other SNPs at 2q11.2 (rs717454), 8q21.3 (rs10103191), and 11q13.2 (rs2167457) exhibited genome-wide significant association with major mood disorders. The SNPs in 2q11.2 and 8q21.3 were novel risk SNPs that were not previously reported, and SNPs at 11q13.2 were in high LD with potential BPD risk SNPs implicated in a previous GWAS. The genome-wide significant loci at 2q11.2 and 11q13.2 exhibited strong effects on the mRNA expression of certain nearby genes in cerebellum. In conclusion, we have identified several novel loci associated with major mood disorders, adding further support for shared genetic risk between BPD and MDD. Our study highlights the necessity and importance of mining public data sets to explore risk genes for complex diseases such as mood disorders
- …
