Velocity-range relation for fission fragments

In two recent notes(1,2) a number of features of the penetration of uranium fission fragments through matter as revealed by cloud-chamber photographs were discussed. In particular, it was pointed out that we have here to do with a velocity-range relation of a novel character which depends on the interplay between electron capture by the fragments over their entire range, and the ultimate stopping by nuclear collisions

Understanding rapid infant weight gain prevention: a systematic review of quantitative and qualitative evidence.

This is the author accepted manuscriptBACKGROUND: Rapid infant weight gain (RIWG) is strongly related to childhood overweight and obesity, and prevention of RIWG is an approach to early years obesity prevention. This systematic review aimed to explore effectiveness, deliverers' and recipients' experiences of involvement, and key intervention components and processes of such prevention activities. METHODS: Key databases and websites were searched systematically for quantitative and qualitative studies covering intervention effectiveness, experiences with intervention involvement or process outcomes. After duplicate screening and quality assessment, papers were analyzed through narrative synthesis, thematic synthesis and intervention component analysis. RESULTS: Seven quantitative and seven qualitative studies were eligible for inclusion. Most intervention studies reported small, but significant results on infant weight gain. More significant results were measured on weight gain during the first compared with the second year of life. A weak evidence base made elaboration of the relationship between intervention effectiveness and content challenging. Home-delivered interventions may be more relevant for parents. Contextual factors, such as social norms, beliefs and professional identity should be considered during intervention development. Stakeholder involvement can be key to increase intervention acceptability and feasibility. CONCLUSIONS: The field of RIWG prevention is new and evolving, but more research is needed before further conclusions about intervention effectiveness and intervention content can be drawn. Future interventions should take parents, health professionals and other contextual needs into account to improve chances of success. More research on long-term effects on overweight and obesity is needed.UK Clinical Research Collaboratio

Inflammatory bowel disease at a young age – implications for achieving upper secondary education

BACKGROUND: The incidence of inflammatory bowel disease (IBD) among children and adolescence is increasing worldwide. Having a chronic condition at a young age may affect educational achievement and later employment and self-support. The study aims to examine the impact of being diagnosed with IBD before 18 years of age on achieving an upper secondary education before 25 years of age. METHODS: Using the Danish National Patient Register (1980-2018) all patients (born 1970-1994) diagnosed with IBD at a young age (<18 years) were identified. The IBD-patients were matched on age and sex with 10 references without IBD at the index date (date of diagnosis of IBD). The outcome was achieving an upper secondary education using data from Danish Education Registers. The association between IBD diagnosis and achieving an upper secondary education was analyzed using Cox regression with robust variance estimation adjusting for parents’ highest educational level. Furthermore, stratified analyses were performed on parental socioeconomic status (education and income). RESULTS: We identified 3,178 patients with IBD: Crohn’s disease (CD) n = 1,344, Ulcerative colitis (UC) n = 1,834. Reference n = 28,220. The median age at diagnosis was 15.3 years (IQR: [13.0;16.9]). At the age of 25 74.0% (CI: 71.6-76.4) for CD, 75.8% (CI: 73.8-77.8) for UC, and 69.7% (CI: 69.2-70.3) for references had achieved an upper secondary education. The adjusted Hazard ratio (HR) of achieving an upper secondary education was 1.05 (CI: 1.00 -1.11) for CD and 1.09 (CI: 1.04 -1.15) for UC. When stratifying the IBD-patient with the lowest socioeconomic status performed better than their peers. CONCLUSIONS: Being diagnosed with IBD before 18 years of age did not reduce the chance of achieving an upper secondary education. Patients with low socioeconomic status performed better than their peers, however the study gives no explanation of this. KEY MESSAGES: • Children diagnosed with IBD before 18 years of age had at least the same chance of achieving an upper secondary education compared to references. • IBD patients with low social economic status performed better than their peers

Periodic magnetoconductance fluctuations in triangular quantum dots in the absence of selective probing

We have studied the magnetoconductance of quantum dots with triangular symmetry and areas down to 0.2 square microns, made in a high mobility two-dimensional electron gas embedded in a GaAs-AlGaAs heterostructure. Semiclassical simulations show that the gross features in the measured magnetoconductance are caused by ballistic effects. Below 1 K we observe a strong periodic oscillation, which may be explained in terms of the Aharanov-Bohm flux quantization through the area of a single classical periodic orbit. From a numerical and analytical analysis of possible trajectories in hard- and soft-walled potentials, we identify this periodic orbit as the enscribed triangle. Contrary to other recent experiments, this orbit is not accessible by classical processes for the incoming collimated beam.Comment: RevTex 8 pages, including 5 postscript figure

Two-Proton Correlations near Midrapidity in p+Pb and S+Pb Collisions at the CERN SPS

Correlations of two protons emitted near midrapidity in p+Pb collisions at 450 GeV/c and S+Pb collisions at 200A GeV/c are presented, as measured by the NA44 Experiment. The correlation effect, which arises as a result of final state interactions and Fermi-Dirac statistics, is related to the space-time characteristics of proton emission. The measured source sizes are smaller than the size of the target lead nucleus but larger than the sizes of the projectiles. A dependence on the collision centrality is observed; the source size increases with decreasing impact parameter. Proton source sizes near midrapidity appear to be smaller than those of pions in the same interactions. Quantitative agreement with the results of RQMD (v1.08) simulations is found for p+Pb collisions. For S+Pb collisions the measured correlation effect is somewhat weaker than that predicted by the model simulations, implying either a larger source size or larger contribution of protons from long-lived particle decays.Comment: 10 pages (LaTeX) text, 4 (EPS) figures; accepted for publication in Phys. Lett.

(Anti)Proton and Pion Source Sizes and Phase Space Densities in Heavy Ion Collisions

NA44 has measured mid-rapidity deuteron spectra from AA collisions at sqrt{s}=18GeV/A at the CERN SPS. Combining these spectra with published proton, antiproton and antideuteron data allows us to calculate, within a coalescence framework, proton and antiproton source sizes and phase space densities. These results are compared to pion source sizes and densities, pA results and to lower energy (AGS) data. The antiproton source is larger than the proton source at sqrt{s}=18GeV/A. The phase space densities of pions and protons are not constant but grow with system size. Both pi+ and proton radii decrease with transverse mass and increase with sqrt{s}. Pions and protons do not freeze-out independently. The nature of their interaction changes as sqrt{s}, and the pion/proton ratio increases.Comment: 4 pages, Latex 2.09, 3 eps figures. Changes for January 2001. The proton source size is now calculated assuming a more realistic Hulthen, rather than Gaussian, wavefunction. A new figure shows the effect of this change which is important for small radii. A second new figure shows the results of RQMD calculations of the proton source size and phase density. Because of correlations between position and momentum coalesence does not show the full proton source size. The paper has been streamlined and readability improve

Harmonic Content of Strain-induced Potential Modulation in Unidirectional Lateral Superlattices

Detailed analysis of the commensurability oscillation (CO) has been performed on unidirectional lateral superlattices with periods ranging from a=92 to 184 nm. Fourier analysis reveals the second (and the third) harmonics along with the fundamental oscillation for a>=138 nm (184 nm) at low-enough temperature, evincing the presence of corresponding harmonics in the profile of the potential modulation. The harmonics manifest themselves in CO with demagnified amplitude due to the low-pass filtering action of the thermal damping factor; with a suitable consideration of the damping effect, the harmonics of the modulation potential are found to have the amplitudes V_2 and V_3 up to roughly 30% of that of the fundamental component V_1, despite the small ratio of the period a to the depth d = 99 nm of the two-dimensional electron gas (2DEG) from the surface. The dependence of V_n on a indicates that the fundamental component originates at the surface, while the higher harmonics arise from the effect of the strain that penetrates down into subsurface. The manipulation of high harmonics thus provides a useful technique to introduce small length-scale modulation into high-mobility 2DEGs located deep inside the wafer.Comment: 9 pages, 5 figure

Nuclear Stopping in Au+Au Collisions at sqrt(sNN) = 200 GeV

Transverse momentum spectra and rapidity densities, dN/dy, of protons, anti-protons, and net--protons (p-pbar) from central (0-5%) Au+Au collisions at sqrt(sNN) = 200 GeV were measured with the BRAHMS experiment within the rapidity range 0 < y < 3. The proton and anti-proton dN/dy decrease from mid-rapidity to y=3. The net-proton yield is roughly constant for y<1 at dN/dy~7, and increases to dN/dy~12 at y~3. The data show that collisions at this energy exhibit a high degree of transparency and that the linear scaling of rapidity loss with rapidity observed at lower energies is broken. The energy loss per participant nucleon is estimated to be 73 +- 6 GeV.Comment: 5 pages, 4 figure