Probing the isovector transition strength of the low-lying nuclear excitations induced by inverse kinematics proton scattering

A compact approach based on the folding model is suggested for the determination of the isoscalar and isovector transition strengths of the low-lying ($\Delta S=\Delta T=0$) excitations induced by inelastic proton scattering measured with exotic beams. Our analysis of the recently measured inelastic $^{18,20}$O+p scattering data at $E_{\rm lab}=30$ and 43 MeV/nucleon has given for the first time an accurate estimate of the isoscalar $\beta_0$ and isovector $\beta_1$ deformation parameters (which cannot be determined from the (p,p') data alone by standard methods) for 2$^+_1$ and $3^-_1$ excited states in $^{18,20}$O. Quite strong isovector mixing was found in the 2$^+_1$ inelastic $^{20}$O+p scattering channel, where the strength of the isovector form factor $F_1$ (prototype of the Lane potential) corresponds to a $\beta_1$ value almost 3 times larger than $\beta_0$ and a ratio of nuclear transition matrix elements $M_n/M_p\simeq 4.2$.Comment: 5 pages, 3 figure

SWI/SNF remains localized to chromatin in the presence of SCHLAP1

SCHLAP1 is a long noncoding RNA that is reported to function by depleting the SWI/SNF complex from the genome. We investigated the hypothesis that SCHLAP1 affects only specific compositions of SWI/SNF. Using several assays, we found that SWI/SNF is not depleted from the genome by SCHLAP1 and that SWI/SNF is associated with many coding and noncoding RNAs, suggesting that SCHLAP1 may function in a SWI/SNF-independent manner

The invasion ecology of sleeper populations: prevalence, persistence, and abrupt shifts

It is well established that nonnative species are a key driver of global environmental change, but much less is known about the underlying drivers of nonnative species outbreaks themselves. In the present article, we explore the concept and implications of nonnative sleeper populations in invasion dynamics. Such populations persist at low abundance for years or even decades—a period during which they often go undetected and have negligible impact—until they are triggered by an environmental factor to become highly abundant and disruptive. Population irruptions are commonly misinterpreted as a recent arrival of the nonnative species, but sleeper populations belie a more complex history of inconspicuous occurrence followed by an abrupt shift in abundance and ecological impact. In the present article, we identify mechanisms that can trigger their irruption, and the implications for invasive species risk assessment and management

The Cost of Privatization

Software transactional memory (STM) guarantees that a transaction, consisting of a sequence of operations on the memory, appears to be executed atomically. In practice, it is important to be able to run transactions together with nontransactional legacy code accessing the same memory locations, by supporting privatization. Privatization should be provided without sacrificing the parallelism offered by today’s multicore systems and multiprocessors. This paper proves an inherent cost for supporting privatization, which is linear in the number of privatized items. Specifically, we show that a transaction privatizing k items must have a data set of size at least k, in an STM with invisible reads, which is oblivious to different non-conflicting executions and guarantees progress in such executions. When reads are visible, it is shown that Ω(k) memory locations must be accessed by a privatizing transaction, where k is the minimum between the number of privatized items and the number of concurrent transactions guaranteed to make progresss, thus capturing the tradeoff between the cost of privatization and the parallelism offered by the STM

Biological invasions in the Cape Floristic Region: history, current patterns, impacts, and management challenges

The Cape Floristic Region (CFR) is the most invaded terrestrial area in South Africa in terms of: the conspicuous prominence of (mainly woody) invasive plants (Fig 12.1, Plate 12) (Henderson 2007); the area invaded as surveyed (Kotzé et al. 2010); and the numbers of animal invaders (Picker and Griffiths 2011). At the same time its status as a globally important system for the study of plant invasions is firmly established. Tree invasions in the region provide model systems that have been influential in the development of plant invasion ecology; in particular work on pine species (Richardson et al. 1994) and Australian acacias (Richardson et al. 2011). In fact, the observation of alien trees invading pristine fynbos shows that widespread invasions are not, as suggested by Charles Elton, confined to ecosystems markedly altered by human activities (Elton 1958). This provided part of the stimulus for a major international programme on invasions in the 1980s funded by the Scientific Committee on Problems of the Environment