2,328 research outputs found

    The impact of Arctic sea ice loss on mid-Holocene climate.

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    Mid-Holocene climate was characterized by strong summer solar heating that decreased Arctic sea ice cover. Motivated by recent studies identifying Arctic sea ice loss as a key driver of future climate change, we separate the influences of Arctic sea ice loss on mid-Holocene climate. By performing idealized climate model perturbation experiments, we show that Arctic sea ice loss causes zonally asymmetric surface temperature responses especially in winter: sea ice loss warms North America and the North Pacific, which would otherwise be much colder due to weaker winter insolation. In contrast, over East Asia, sea ice loss slightly decreases the temperature in early winter. These temperature responses are associated with the weakening of mid-high latitude westerlies and polar stratospheric warming. Sea ice loss also weakens the Atlantic meridional overturning circulation, although this weakening signal diminishes after 150-200 years of model integration. These results suggest that mid-Holocene climate changes should be interpreted in terms of both Arctic sea ice cover and insolation forcing

    Proper holomorphic maps between bounded symmetric domains with small rank differences

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    In this paper we study the rigidity of proper holomorphic maps f ⁣:ΩΩf\colon \Omega\to\Omega' between irreducible bounded symmetric domains Ω\Omega and Ω\Omega' with small rank differences: 2rank(Ω)<2rank(Ω)12\leq \text{rank}(\Omega')< 2\,\text{rank}(\Omega)-1. More precisely, if either Ω\Omega and Ω\Omega' have the same type or Ω\Omega is of type~III and Ω\Omega' is of type~I, then up to automorphisms, ff is of the form f=ıFf=\imath\circ F, where F=F1×F2 ⁣:ΩΩ1×Ω2F = F_1\times F_2\colon \Omega\to \Omega_1'\times \Omega_2'. Here Ω1\Omega_1', Ω2\Omega_2' are bounded symmetric domains, the map F1 ⁣:ΩΩ1F_1\colon \Omega \to \Omega_1' is a standard embedding, F2:ΩΩ2F_2: \Omega \to \Omega_2', and ı ⁣:Ω1×Ω2Ω\imath\colon \Omega'_1\times \Omega'_2 \to \Omega' is a totally geodesic holomorphic isometric embedding. Moreover we show that, under the rank condition above, there exists no proper holomorphic map f:ΩΩf: \Omega \to \Omega' if Ω\Omega is of type~I and Ω\Omega' is of type~III, or Ω\Omega is of type~II and Ω\Omega' is either of type~I or III. By considering boundary values of proper holomorphic maps on maximal boundary components of Ω\Omega, we construct rational maps between moduli spaces of subgrassmannians of compact duals of Ω\Omega and Ω\Omega', and induced CR-maps between CR-hypersurfaces of mixed signature, thereby forcing the moduli map to satisfy strong local differential-geometric constraints (or that such moduli maps do not exist), and complete the proofs from rigidity results on geometric substructures modeled on certain admissible pairs of rational homogeneous spaces of Picard number 1

    A scoping review of music-based interventions for swallowing difficulties: implications for treating older adults with presbyphagia

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    ObjectivesPresbyphagia refers to age-related changes in the swallowing mechanism (e.g., reduced skeletal muscle strength that decreases bolus control). If left untreated, these changes can lead to dysphagia, which refers to impaired swallowing (e.g., coughing or choking when eating). Given that swallowing difficulties are common among older adults that they make up the fastest growing age group globally, the need for interventions to address presbyphagia is gaining urgency. To begin to address this need, we conducted a scoping review to analyze music therapy research aimed at enhancing swallowing function. The objective was to identify key intervention characteristics and propose clinical implications for treating presbyphagia using music therapy.MethodsThis review followed the methodological frameworks outlined by Arksey and O’Malley and Levac et al. and used the Preferred Reporting Items for Systematic Reviews and Meta-Analysis for Scoping Reviews for analysis and reporting. Four electronic databases (i.e., ProQuest, PubMed, RISS, Web of Science) were searched for quantitative and qualitative studies in English or Korean that used music-based interventions to address swallowing function in older adults. Content analysis was conducted to identify and compare the main features of music interventions for swallowing difficulties among older adults.ResultsTen articles were identified and analyzed. It was found that three core components–respiration, vocalization, and singing–were employed to enhance swallowing function in populations with neurological impairments, dementia, or head and neck cancer. Notably, actions closely linked to swallowing function, such as laryngeal elevation and oral movements, were utilized therapeutically to speak or sing. Based on these characteristics, clinical implications are proposed to address presbyphagia.ConclusionSinging entails a systematic and focused incorporation of stepwise activities that can be used to address swallowing disorders. In this context, critical clinical implications that music therapists should consider when treating individuals with presbyphagia include warmup breathing, vocalizing targeting laryngeal control, and singing targeting oral motor control. This review can contribute to the expansion of music therapy with older adults and the advancement of music therapy techniques

    Isolation of human Dna2 endonuclease and characterization of its enzymatic properties

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    In eukaryotes, the creation of ligatable nicks in DNA from flap structures generated by DNA polymerase δ-catalyzed displacement DNA synthesis during Okazaki fragment processing depends on the combined action of Fen1 and Dna2. These two enzymes contain partially overlapping but distinct endonuclease activities. Dna2 is well-suited to process long flaps, which are converted to nicks by the subsequent action of Fen1. In this report, we purified human Dna2 as a recombinant protein from human cells transfected with the cDNA of the human homologue of Saccharomyces cerevisiae Dna2. We demonstrated that the purified human Dna2 enzyme contains intrinsic endonuclease and DNA-dependent ATPase activities, but is devoid of detectable DNA helicase activity. We determined a number of enzymatic properties of human Dna2 including its substrate specificity. When both 5′ and 3′ tailed ssDNAs were present in a substrate, such as a forked-structured one, both single-stranded regions were cleaved by human Dna2 (hDna2) with equal efficiency. Based on this and other properties of hDna2, it is likely that this enzyme facilitates the removal of 5′ and 3′ regions in equilibrating flaps that are likely to arise during the processing of Okazaki fragments in human cells

    Heterogeneous nuclear ribonucleoprotein (hnRNP) L promotes DNA damage-induced cell apoptosis by enhancing the translation of p53

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    The tumor suppressor p53 is an essential gene in the induction of cell cycle arrest, DNA repair, and apoptosis. p53 protein is induced under cellular stress, blocking cell cycle progression and inducing DNA repair. Under DNA damage conditions, it has been reported that post-transcriptional regulation of p53 mRNA contributes to the increase in p53 protein level. Here we demonstrate that heterogeneous nuclear ribonucleoprotein (hnRNP) L enhances p53 mRNA translation. We found that hnRNP L is increased and binds to the 5&apos; UTR of p53 mRNA in response to DNA damage. Increased hnRNP L caused enhancement of p53 mRNA translation. Conversely, p53 protein levels were decreased following hnRNP L knock-down, rendering them resistant to apoptosis and arrest in the G2/M phase after DNA damage. Thus, our findings suggest that hnRNP L functions as a positive regulator of p53 translation and promotes cell cycle arrest and apoptosis.11Ysciescopu
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