Heat capacity and pairing transition in nuclei

A simple model based on the canonical-ensemble theory is outlined for hot nuclei. The properties of the model are discussed with respect to the Fermi gas model and the breaking of Cooper pairs. The model describes well the experimental level density of deformed nuclei in various mass regions. The origin of the so-called S-shape of the heat capacity curve Cv(T) is discussed.Comment: 6 pages + 8 figure

Pairing transition of nuclei at finite temperature

Pairing transition at finite temperature was investigated by the shell model and BCS calculations. The definitive signature of pairing transition is identified by a "transition temperature" $T_t$ estimated from a "thermal" odd-even mass difference, while there is no sharp phase transition because of the finiteness of nucleus. It is found that $T_t$ is in good agreement with predictions of critical temperature $T_c$ in the BCS approximation, and the pairing correlations almost vanish at two points of the transition temperature $T\approx 2T_{t}$. The BCS calculations show that the critical temperature $T_c$ increases with increasing deformation.Comment: 12 pages, 6 figures, accepted for publication in Nuclear Physics

Level densities and γ\gamma-strength functions in 148,149^{148,149}Sm

The level densities and $\gamma$-strength functions of the weakly deformed $^{148}$Sm and $^{149}$Sm nuclei have been extracted. The temperature versus excitation energy curve, derived within the framework of the micro canonical ensemble, shows structures, which we associate with the break up of Cooper pairs. The nuclear heat capacity is deduced within the framework of both the micro canonical and the canonical ensemble. We observe negative heat capacity in the micro canonical ensemble whereas the canonical heat capacity exhibits an S-shape as function of temperature, both signals of a phase transition. The structures in the $\gamma$-strength functions are discussed in terms of the pygmy resonance and the scissors mode built on exited states. The samarium results are compared with data for the well deformed $^{161,162}$Dy, $^{166,167}$Er and $^{171,172}$Yb isotopes and with data from (n,$\gamma$)-experiments and giant dipole resonance studies.Comment: 12 figure

Level density and gamma strength function in 162-Dy from inelastic 3-He scattering

Complementary measurements have been performed for the level density and gamma strength function in 162-Dy using inelastic 3-He scattering. Comparing these results to previous measurements using the 163-Dy(3-He,alpha) reaction, reveals that the measured quantities above 1.5 MeV do not depend significantly on the nuclear reaction chosen.Comment: 15 pages, including 7 figure

Level density and thermal properties in rare earth nuclei

A convergent method to extract the nuclear level density and the gamma-ray strength function from primary gamma-ray spectra has been established. Thermodynamical quantities have been obtained within the microcanonical and canonical ensemble theory. Structures in the caloric curve and in the heat capacity curve are interpreted as fingerprints of breaking of Cooper pairs and quenching of pairing correlations. The strength function can be described using models and common parameterizations for the E1, M1 and pygmy resonance strength. However, a significant decrease of the pygmy resonance strength at finite temperatures has been observed.Comment: 15 pages including 8 figures. Proceedings article for the conference Nuclear Structure and Related Topics, Dubna, Russia, June 6-10, 200

Home learning environments and children’s language and literacy skills: A meta-analytic review of studies conducted in low- and middle-income countries

A robust finding from research in high-income countries is that children living in resource-poor homes are vulnerable to difficulties with language and literacy but less is known about this association in low- and middle-income (LMI) countries. We present a meta-analysis of 6,678 correlations from studies in 43 LMI countries. Overall, the results indicate a small but significant association (r = .08) between home language and literacy environment and children's language and literacy skills. After examining a range of moderators, adult literacy practices and books-at-home had a significantly larger association with children's language and literacy skills than did home tutoring. Studies using customized measures demonstrated a more marked association between home attributes and children's outcomes (r = .14) than studies using a common measure across multiple sites (r = .06). Published studies showed significantly larger associations than unpublished studies, and countries with greater income inequality showed a larger association than relatively egalitarian societies. We conclude that the small overall association should not be taken as support for the absence of, or a vanishingly small relationship between the home learning environment and children's language and literacy skills in LMI countries. Rather, an important factor in detecting this relationship is that assessments must better reflect the nature of homes in different cultures to capture true variation in the population. Such contextually situated measurement would lead to an inclusive conceptualization of home learning environments and can better inform intervention programs to enhance children's educational success, a critical target for many LMI countries. (PsycInfo Database Record (c) 2024 APA, all rights reserved)

Landau-Ginzburg method applied to finite fermion systems: Pairing in Nuclei

Given the spectrum of a Hamiltonian, a methodology is developed which employs the Landau-Ginsburg method for characterizing phase transitions in infinite systems to identify phase transition remnants in finite fermion systems. As a first application of our appproach we discuss pairing in finite nuclei.Comment: 14 pages, 4 figure

Anisotropic Conformal Infinity

We generalize Penrose's notion of conformal infinity of spacetime, to situations with anisotropic scaling. This is relevant not only for Lifshitz-type anisotropic gravity models, but also in standard general relativity and string theory, for spacetimes exhibiting a natural asymptotic anisotropy. Examples include the Lifshitz and Schrodinger spaces (proposed as AdS/CFT duals of nonrelativistic field theories), warped AdS_3, and the near-horizon extreme Kerr geometry. The anisotropic conformal boundary appears crucial for resolving puzzles of holographic renormalization in such spacetimes.Comment: 11 page

Risk assessment of the biocontrol product Nemaslug 2.0 with the active organisms Phasmarhabditis californica (strain P19D) and Moraxella osloensis

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Gastric cancer and Helicobacter pylori: a combined analysis of 12 case control studies nested within prospective cohorts

BACKGROUND: The magnitude of the association between Helicobacter pylori and incidence of gastric cancer is unclear. H pylori infection and the circulating antibody response can be lost with development of cancer; thus retrospective studies are subject to bias resulting from classifi- cation of cases as H pylori negative when they were infected in the past. AIMS: To combine data from all case control studies nested within prospective cohorts to assess more reliably the relative risk of gastric cancer associated with H pylori infection.To investigate variation in relative risk by age, sex, cancer type and subsite, and interval between blood sampling and cancer diagnosis. METHODS: Studies were eligible if blood samples for H pylori serology were collected before diagnosis of gastric cancer in cases. Identified published studies and two unpublished studies were included. Individual subject data were obtained for each. Matched odds ratios (ORs) and 95% confidence intervals (95% CI) were calculated for the association between H pylori and gastric cancer. RESULTS: Twelve studies with 1228 gastric cancer cases were considered. The association with H pylori was restricted to noncardia cancers (OR 3.0; 95% CI 2.3–3.8) and was stronger when blood samples for H pylori serology were collected 10+ years before cancer diagnosis (5.9; 3.4–10.3). H pylori infection was not associated with an altered overall risk of cardia cancer (1.0; 0.7–1.4). CONCLUSIONS: These results suggest that 5.9 is the best estimate of the relative risk of non-cardia cancer associated with H pylori infection and that H pylori does not increase the risk of cardia cancer. They also support the idea that when H pylori status is assessed close to cancer diagnosis, the magnitude of the non-cardia association may be underestimated