Evidence and modeling of turbulence bifurcation in L-mode confinement transitions on Alcator C-Mod

© 2020 Author(s). Analysis and modeling of rotation reversal hysteresis experiments show that a single turbulent bifurcation is responsible for the Linear to Saturated Ohmic Confinement (LOC/SOC) transition and concomitant intrinsic rotation reversal on Alcator C-Mod. Plasmas on either side of the reversal exhibit different toroidal rotation profiles and therefore different turbulence characteristics despite the profiles of density and temperature, which are indistinguishable within measurement uncertainty. Elements of this bifurcation are also shown to persist for auxiliary heated L-modes. The deactivation of subdominant (in the linear growth rate and contribution to heat transport) ion temperature gradient and trapped electron mode instabilities is identified as the only possible change in turbulence within a reduced quasilinear transport model across the reversal, which is consistent with the measured profiles and inferred heat and particle fluxes. Experimental constraints on a possible change from strong to weak turbulence, outside the description of the quasilinear model, are also discussed. These results indicate an explanation for the LOC/SOC transition that provides a mechanism for the hysteresis through the dynamics of subdominant modes and changes in their relative populations and does not involve a change in the most linearly unstable ion-scale drift-wave instability

Laser-driven acceleration of quasi-monoenergetic, near-collimated titanium ions via a transparency-enhanced acceleration scheme

Laser-driven ion acceleration has been an active research area in the past two decades with the prospects of designing novel and compact ion accelerators. Many potential applications in science and industry require high-quality, energetic ion beams with low divergence and narrow energy spread. Intense laser ion acceleration research strives to meet these challenges and may provide high charge state beams, with some successes for carbon and lighter ions. Here we demonstrate the generation of well collimated, quasi-monoenergetic titanium ions with energies ∼145 and 180 MeV in experiments using the high-contrast(<10-9) and high-intensity (6× 1020 W cm-2) Trident laser and ultra-Thin (∼100 nm) titanium foil targets. Numerical simulations show that the foils become transparent to the laser pulses, undergoing relativistically induced transparency (RIT), resulting in a two-stage acceleration process which lasts until ∼2 ps after the onset of RIT. Such long acceleration time in the self-generated electric fields in the expanding plasma enables the formation of the quasi-monoenergetic peaks. This work contributes to the better understanding of the acceleration of heavier ions in the RIT regime, towards the development of next generation laser-based ion accelerators for various applications

Fatherhood and wage inequality in Britain, Finland, and Germany

Objective This study investigates whether and how fatherhood shapes the wage distribution in Britain, Finland, and Germany. Background Existing research debates whether fatherhood is associated with greater wages. However, it remains unclear whether the association between fatherhood and wages varies along the wage distribution as well as institutional contexts. To explore this, we compare three countries that differ in their wage bargaining institutions and family policies. Method We use unconditional quantile regression on longitudinal data from the 1995 to 2016 waves of the Finnish Linked Employer Employee data, German Socio-Economic Panel, and UK Longitudinal Household Study. To control for selection into fatherhood, we combine quantile regressions with fixed effects techniques. Results Results show little evidence of substantial fatherhood wage effects along men's wage distribution. In all countries, fathers' higher wages at the median and top of the wage distribution are mostly accounted for by selection, but fatherhood shifts the bottom part of the distribution to the left particularly in the UK. Conclusions The extent to which having a child affects men's wages across the wage distribution is similar across three diverse policy contexts. Yet, differences across the wage distribution are larger in the UK. We argue this may be linked to its higher level of inequality typical of liberal labour markets

Use of pyridazinediones as extracellular cleavable linkers through reversible cysteine conjugation

Herein we report a retro-Michael deconjugation pathway of thiol-pyridazinedione linked protein bioconjugates to provide a novel cleavable linker technology. We demonstrate that the novel pyridazinedione linker does not suffer from off-target modification with blood thiols (e.g., glutathione, human serum albumin (HSA)), which is in sharp contrast to an analogous maleimide linker

Impressões sobre o teste rápido para o HIV entre usuários de drogas injetáveis no Brasil

OBJECTIVE: To describe perceptions, experiences, knowledge, beliefs and the willingness of injecting drug users to be HIV tested by using rapid tests. METHODS: A qualitative exploratory study was carried out among injecting drug users from December 2003 to February 2004 in five Brazilian cities, located in four regions of Brazil. A semi-structured interview guide containing both closed and open-ended questions was used to address perceptions about non-conventional testing procedures, and non-traditional ways to provide testing access to injecting drug users. A total of 106 interviews, about 26 per region, were conducted. RESULTS: Characteristics of the population studied, common thoughts about HIV rapid testing, preference for using blood or saliva specimens, and other testing preferences, were presented together with reported advantages and disadvantages of each option. The study findings showed that the use of rapid tests among these users is feasible and that they are willing to be tested using rapid HIV tests, especially if some issues related to privacy and reliability of the test could be addressed. CONCLUSIONS: The study findings showed that rapid tests may be well accepted for this population. These tests can be considered a valuable tool, allowing a more injecting drug users to learn their HIV status and possibly be referred to treatment and should support more effective testing strategies for them.OBJETIVO: Descrever as impressões, experiências, conhecimentos, crenças e a receptividade de usuários de drogas injetáveis para participar das estratégias de testagem rápida para HIV. MÉTODOS: Estudo qualitativo exploratório foi conduzido entre usuários de drogas injetáveis, de dezembro de 2003 a fevereiro de 2004, em cinco cidades brasileiras, localizadas em quatro regiões do País. Um roteiro de entrevista semi-estruturado contendo questões fechadas e abertas foi usado para avaliar percepções desses usuários sobre procedimentos e formas alternativas de acesso e testagem. Foram realizadas 106 entrevistas, aproximadamente 26 por região. RESULTADOS: Características da população estudada, opiniões sobre o teste rápido e preferências por usar amostras de sangue ou saliva foram apresentadas junto com as vantagens e desvantagens associadas a cada opção. Os resultados mostraram a viabilidade do uso de testes rápidos entre usuários de drogas injetáveis e o interesse deles quanto à utilização destes métodos, especialmente se puderem ser equacionadas questões relacionadas à confidencialidade e confiabilidade dos testes. CONCLUSÕES: Os resultados indicam que os testes rápidos para HIV seriam bem recebidos por essa população. Esses testes podem ser considerados uma ferramenta valiosa, ao permitir que mais usuários de drogas injetáveis conheçam sua sorologia para o HIV e possam ser referidos para tratamento, como subsidiar a melhoria das estratégias de testagem entre usuários de drogas injetáveis

TOMOBFLOW: feature-preserving noise filtering for electron tomography

<p>Abstract</p> <p>Background</p> <p>Noise filtering techniques are needed in electron tomography to allow proper interpretation of datasets. The standard linear filtering techniques are characterized by a tradeoff between the amount of reduced noise and the blurring of the features of interest. On the other hand, sophisticated anisotropic nonlinear filtering techniques allow noise reduction with good preservation of structures. However, these techniques are computationally intensive and are difficult to be tuned to the problem at hand.</p> <p>Results</p> <p>TOMOBFLOW is a program for noise filtering with capabilities of preservation of biologically relevant information. It is an efficient implementation of the Beltrami flow, a nonlinear filtering method that locally tunes the strength of the smoothing according to an edge indicator based on geometry properties. The fact that this method does not have free parameters hard to be tuned makes TOMOBFLOW a user-friendly filtering program equipped with the power of diffusion-based filtering methods. Furthermore, TOMOBFLOW is provided with abilities to deal with different types and formats of images in order to make it useful for electron tomography in particular and bioimaging in general.</p> <p>Conclusion</p> <p>TOMOBFLOW allows efficient noise filtering of bioimaging datasets with preservation of the features of interest, thereby yielding data better suited for post-processing, visualization and interpretation. It is available at the web site <url>http://www.ual.es/%7ejjfdez/SW/tomobflow.html</url>.</p

Revisiting protein aggregation as pathogenic in sporadic Parkinson and Alzheimer diseases.

The gold standard for a definitive diagnosis of Parkinson disease (PD) is the pathologic finding of aggregated α-synuclein into Lewy bodies and for Alzheimer disease (AD) aggregated amyloid into plaques and hyperphosphorylated tau into tangles. Implicit in this clinicopathologic-based nosology is the assumption that pathologic protein aggregation at autopsy reflects pathogenesis at disease onset. While these aggregates may in exceptional cases be on a causal pathway in humans (e.g., aggregated α-synuclein in SNCA gene multiplication or aggregated β-amyloid in APP mutations), their near universality at postmortem in sporadic PD and AD suggests they may alternatively represent common outcomes from upstream mechanisms or compensatory responses to cellular stress in order to delay cell death. These 3 conceptual frameworks of protein aggregation (pathogenic, epiphenomenon, protective) are difficult to resolve because of the inability to probe brain tissue in real time. Whereas animal models, in which neither PD nor AD occur in natural states, consistently support a pathogenic role of protein aggregation, indirect evidence from human studies does not. We hypothesize that (1) current biomarkers of protein aggregates may be relevant to common pathology but not to subgroup pathogenesis and (2) disease-modifying treatments targeting oligomers or fibrils might be futile or deleterious because these proteins are epiphenomena or protective in the human brain under molecular stress. Future precision medicine efforts for molecular targeting of neurodegenerative diseases may require analyses not anchored on current clinicopathologic criteria but instead on biological signals generated from large deeply phenotyped aging populations or from smaller but well-defined genetic-molecular cohorts

Environmental novelty exacerbates stress hormones and Aβ pathology in an Alzheimer’s model

Cognitive stimulation has been proposed as a non-pharmacological intervention to be used in primary, secondary and tertiary prevention approaches for Alzheimer’s disease. A common familial Alzheimer’s disease transgenic model showed heightened levels of the stress hormone, corticosterone. When exposed to periodic enhanced cognitive stimulation, these animals demonstrated further heightened levels of corticosterone as well as increased Aβ pathology. Hence, Alzheimer’s disease may be associated with hypothalamic-pituitary-adrenal (HPA) axis dysfunction, causing stimulatory environments to become stress-inducing, leading to a glucocorticoid-pathology cycle contributing to further Aβ release and plaque formation. This finding suggests that stimulation-based interventions and local environments for people with Alzheimer’s disease need to be designed to minimise a stress response that may exacerbate brain pathology

Complete genome sequence of a novel extrachromosomal virus-like element identified in planarian Girardia tigrina

BACKGROUND: Freshwater planarians are widely used as models for investigation of pattern formation and studies on genetic variation in populations. Despite extensive information on the biology and genetics of planaria, the occurrence and distribution of viruses in these animals remains an unexplored area of research. RESULTS: Using a combination of Suppression Subtractive Hybridization (SSH) and Mirror Orientation Selection (MOS), we compared the genomes of two strains of freshwater planarian, Girardia tigrina. The novel extrachromosomal DNA-containing virus-like element denoted PEVE (Planarian Extrachromosomal Virus-like Element) was identified in one planarian strain. The PEVE genome (about 7.5 kb) consists of two unique regions (Ul and Us) flanked by inverted repeats. Sequence analyses reveal that PEVE comprises two helicase-like sequences in the genome, of which the first is a homolog of a circoviral replication initiator protein (Rep), and the second is similar to the papillomavirus E1 helicase domain. PEVE genome exists in at least two variant forms with different arrangements of single-stranded and double-stranded DNA stretches that correspond to the Us and Ul regions. Using PCR analysis and whole-mount in situ hybridization, we characterized PEVE distribution and expression in the planarian body. CONCLUSIONS: PEVE is the first viral element identified in free-living flatworms. This element differs from all known viruses and viral elements, and comprises two potential helicases that are homologous to proteins from distant viral phyla. PEVE is unevenly distributed in the worm body, and is detected in specific parenchyma cells