Abstract
The existence of black holes (BHs) with masses in the range between stellar remnants and supermassive BHs has only recently become unambiguously established. GW190521, a gravitational wave ...signal detected by the LIGO/Virgo Collaboration, provides the first direct evidence for the existence of such intermediate-mass BHs (IMBHs). This event sparked and continues to fuel discussion on the possible formation channels for such massive BHs. As the detection revealed, IMBHs can form via binary mergers of BHs in the “upper mass gap” (≈40–120
M
⊙
). Alternatively, IMBHs may form via the collapse of a very massive star formed through stellar collisions and mergers in dense star clusters. In this study, we explore the formation of IMBHs with masses between 120 and 500
M
⊙
in young, massive star clusters using state-of-the-art Cluster Monte Carlo models. We examine the evolution of IMBHs throughout their dynamical lifetimes, ending with their ejection from the parent cluster due to gravitational radiation recoil from BH mergers, or dynamical recoil kicks from few-body scattering encounters. We find that
all
of the IMBHs in our models are ejected from the host cluster within the first ∼500 Myr, indicating a low retention probability of IMBHs in this mass range for globular clusters today. We estimate the peak IMBH merger rate to be
≈
2
Gpc
−
3
yr
−
1
at redshift
z
≈ 2.
Abstract Very massive stars (VMSs) formed via a sequence of stellar collisions in dense star clusters have been proposed as the progenitors of massive black hole seeds. VMSs could indeed collapse to ...form intermediate-mass black holes, which would then grow by accretion to become the supermassive black holes observed at the centers of galaxies and powering high-redshift quasars. Previous studies have investigated how different cluster initial conditions affect the formation of a VMS, including mass segregation, stellar collisions, and binaries, among others. In this study, we investigate the growth of VMSs with a new grid of Cluster Monte Carlo star cluster simulations—the most expansive to date. The simulations span a wide range of initial conditions, varying the number of stars, cluster density, stellar initial mass function (IMF), and primordial binary fraction. We find a gradual shift in the mass of the most massive collision product across the parameter space; in particular, denser clusters born with top-heavy IMFs provide strong collisional regimes that form VMSs with masses easily exceeding 1000 M ⊙ . Our results are used to derive a fitting formula that can predict the typical mass of a VMS formed as a function of the star cluster properties. Additionally, we study the stochasticity of this process and derive a statistical distribution for the mass of the VMS formed in one of our models, recomputing the model 50 times with different initial random seeds.
Abstract
The objective of this systematic review was to evaluate which salivary biomarkers are altered in patients with burning mouth syndrome (BMS) compared to a control group (CG). A comprehensive ...literature search was conducted in four databases. Case–control studies evaluating salivary biomarkers in BMS patients were included. Risk of bias was assessed using the Newcastle‐Ottawa tool. RevMan was used for meta‐analysis. Seventeen studies were selected. The included studies collected 54 different biomarkers. Of these biomarkers, only three (cortisol, α‐amylase, and dehydroepiandrosterone) were analyzed in three or more studies. Dehydroepiandrosterone obtained contradictory results among the studies. However, cortisol and α‐amylase levels were found to be higher in BMS patients. Cortisol was the only biomarker which could be included for meta‐analysis. Cortisol levels were significantly higher in the BMS group compared to the CG (Mean Difference = 0.39; 95% CI 0.14–0.65;
p
= 0.003). In conclusion, different studies investigated salivary biomarkers in patients with BMS compared to a CG, with controversial results. Meta‐analysis, confirmed by trial‐sequential analysis, showed how cortisol levels were significantly higher in BMS. Cortisol emerges as an interesting salivary biomarker in BMS, but future properly designed studies are needed to evaluate its role in diagnosis and/or response to treatment.
Plant species produce far more seedlings than those surviving to adulthood. It would seem reasonable to take advantage of that excess production, by relocating seedlings to desired restoration sites. ...There is, however, little information available on this issue. In the present study, we collected naturally regenerated seedlings of two native species,
Calophyllum brasiliense
(“barí”) and
Vochysia guatemalensis
(“corpo”), in old‐growth forest patches, and transplanted them for the enrichment of a secondary tropical forest in Veracruz, Mexico. For transplanted
C. brasiliense
seedlings, overall survival was 32% after 20 months, and for
V. guatemalensis
seedlings it was 66% after 26 months. The mean height (±standard error) of all
C. brasiliense
and
V. guatemalensis
seedlings that survived until the end of the study, was 33 ± 2 cm (from initially 12.9 ± 0.2 cm) and 52 ± 5 cm (from 4.6 ± 0.1 cm), respectively. We applied a cost–benefit model to assess the trade‐off between initial‐investment costs and the resulting survival of transplanting naturally regenerated seedlings in the current study, in comparison with direct seeding (with and without the protection of seeds and emerged seedlings) reported in a previous study for the same area and species. For
C. brasiliense
, the success of transplanting naturally regenerated seedlings was always inferior to direct seeding without protection, whereas for
V. guatemalensis
it was always superior. Comparing the transplantation of naturally regenerated seedlings with direct seeding with protection, the best propagation strategy depended on the (monetary) value that a treelet is expected to be worth after 2 years.
The epithelial-to-mesenchymal transition (EMT) is a biological process in which a non-motile epithelial cell changes to a mesenchymal state with invasive capacities. However, the EMT program is ...involved in both physiological and pathological processes. Cancer-associated EMT is known to contribute to increase invasiveness and metastasis, resistance to therapies, and generation of cell populations with stem cell-like characteristics and therefore is deeply involved in tumor progression. This process is finely orchestrated by multiple signaling pathways and regulatory transcriptional networks. The hallmark of EMT is the loss of epithelial surface markers, mainly E-cadherin, and the acquisition of mesenchymal phenotype. These events can be mediated by EMT transcription factors which can cooperate with several enzymes to repress the E-cadherin expression and regulate EMT at the epigenetic and post-translational level. A growing body of evidence indicates that cancer cells can reside in various phenotypic states along the EMT spectrum, where cells can jointly retain epithelial traits with mesenchymal ones. This type of phenotypic plasticity endows cancer cells with tumor-initiating potential. The identification of the signaling pathways and modulators that lead to activation of EMT programs during these disease processes is providing new insights into the plasticity of cellular phenotypes and possible therapeutic interventions.
Higher education institutions routinely use Learning Management Systems (LMS) for multiple purposes; to organise coursework and assessment, to facilitate staff and student interactions, and to act as ...repositories of learning objects. The analysis reported here involves staff (n=46) and student (n=470) responses to surveys as well as data collected in interviews and focus groups. The research focuses on participants' perceptions of two broad affordances of the LMS: accessibility and interactivity. Differences were found between student and staff views in relation to accessibility of online materials, with students rating its contribution to their learning more highly than staff. However, the two groups held similar views with regards to the effectiveness of LMS tools to enable interactivity. Applying interaction equivalency theory (Anderson, 2003), the results reveal the importance of the key choices made by teaching staff in deciding which LMS tools to use in order to maximise student participation and learning. Author abstract
A priority in restoration research is to seek methods that reach high levels of plant establishment at the lowest possible cost. Here, we test how direct seeding works with and without a plastic ...protector that covers seeds and seedlings in an early‐successional rainforest in Veracruz (Mexico). Two native species, Calophyllum brasiliense (barí) and Vochysia guatemalensis (corpo), at three topographic positions, were used. Germination rates with and without the protector were 84 versus 79% for C. brasiliense, and 98 versus 89% for V. guatemalensis, respectively. The protector significantly improved the germination only of V. guatemalensis. Plant survivorship of V. guatemalensis 27 months after seeding was significantly higher with the protector (78%) than without it (46%). For C. brasiliense, there were no differences in survivorship after 22 months with (61%) and without (54%) protector. In both species, the protector had no effect on height growth, which was significantly larger for seedlings located at the toeslope position. We developed a cost–benefit model that provides a threshold value at which the investment for protectors is justified by a resulting higher survivorship: If 27 months after seeding a treelet of V. guatemalensis is worth at least 0.83 USD on our sites, then the effect of the protector is worth the cost of its implementation (for C. brasiliense, survivorship was statistically undistinguishable with and without protector). We suggest that direct seeding with a plastic protector could be a promising alternative for forest restoration with suitable tree species.
Background
Cachexia is a metabolic syndrome that affects up to 50–80% of cancer patients. The pathophysiology is characterized by a variable combination of reduced food intake and abnormal ...metabolism, including systemic inflammation and negative protein and energy balance. Despite its high clinical significance, defined diagnostic criteria and established therapeutic strategies are lacking. The ‘omics’ technologies provide a global view of biological systems. We hypothesize that blood‐based metabolomics might identify findings in cachectic patients that could provide clues to gain knowledge on its pathophysiology, and eventually postulate new therapeutic strategies.
Methods
This is a cross‐sectional observational study in two cohorts of cancer patients, with and without cachexia. Patients were consecutively recruited from routine clinical practice of a General Oncology Department at ‘12 de Octubre’ University Hospital. Selected clinical and biochemical features were collected. Blood metabolite fingerprinting was performed using three analytical platforms, gas chromatography coupled to mass spectrometry (GC–MS), capillary electrophoresis coupled to mass spectrometry (CE–MS), and liquid chromatography coupled to mass spectrometry (LC–MS). Besides, we performed pathway‐based metabolite analyses to obtain more information on biological functions.
Results
A total of 15 subjects were included in this study, 8 cachectic and 7 non‐cachectic patients. Metabolomic analyses were able to correctly classify their samples in 80% (GC–MS), 97% (CE–MS), 96% LC–MS (positive mode), and 89% LC–MS (negative mode) of the cases. The most prominent metabolic alteration in plasma of cachectic patients was the decrease of amino acids and derivatives especially arginine, tryptophan, indolelactic acid, and threonine, with 0.4‐fold change (FC) compared with non‐cachectic patients, along with the reduction of glycerophospholipids mainly lysophosphatidylcholines(O‐16:0) and lysophosphatidylcholines(20:3) sn‐1, FC = 0.1 and sphingolipids SM(d30:0), FC = 0.5. The metabolite with the highest increase was cortisol (FC = 1.6). Such alterations suggest a role of the following metabolic pathways in the pathophysiology of cancer cachexia: arginine and proline metabolism; alanine, aspartate, and glutamate metabolism; phenylalanine metabolism; lysine degradation; aminoacyl‐tRNA biosynthesis; fatty acid elongation in mitochondria; tricarboxylic acids cycle; among others.
Conclusions
These findings suggest that plasma amino acids and lipids profiling has great potential to find the mechanisms involved in the pathogenesis of cachexia. Metabolic profiling of plasma from cancer patients show differences between cachexia and non‐cachexia in amino acids and lipids that might be related to mechanisms involved in its pathophysiology. A better understanding of these mechanisms might identify novel therapeutic approaches to palliate this unmet medical condition.
There is a significant concern in Australia that insufficient numbers of students are enrolling in, and graduating from, engineering degree programmes. Research studies and government reports ...continue to reveal that young people's negative views of engineering are a major factor contributing to this phenomenon. To unearth how these views are formed and evolve, we investigated a sample of primary (n = 555), secondary (n = 493) and university (n = 1517) students in Australia. The students completed a survey that examined their interests in, attitudes towards, and knowledge and understandings of engineering. Key findings were that primary students were more positively predisposed towards engineering and its related sub-disciplines than secondary students; and that in terms of influences on career choice, an innate interest in science or engineering is a stronger influence than the potential earning power of an engineering position. It was also evident that careers advisors were seen to have a strong influence on secondary students' choices. We argue that there is strong potential to harness and work with interest in engineering at an early age, and that there is considerable work needed to leverage advice and sustain interest at secondary level.
Dopaminergic denervation in patients with Parkinson's disease is associated with changes in brain metabolism. Cerebral in-vivo mapping of glucose metabolism has been studied in severe stable ...parkinsonian monkeys, but data on brain metabolic changes in early stages of dopaminergic depletion of this model is lacking. Here, we report cerebral metabolic changes associated with progressive nigrostriatal lesion in the pre-symptomatic and symptomatic stages of the progressive 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) monkey model of Parkinson's Disease. Monkeys (Macaca fascicularis) received MPTP injections biweekly to induce progressive grades of dopamine depletion. Monkeys were sorted according to motor scale assessments in control, asymptomatic, recovered, mild, and severe parkinsonian groups. Dopaminergic depletion in the striatum and cerebral metabolic patterns across groups were studied in vivo by positron emission tomography (PET) using monoaminergic (11C-dihydrotetrabenazine; 11C-DTBZ) and metabolic (2-18F-fluoro-2-deoxy-d-glucose; 18F-FDG) radiotracers. 11C-DTBZ-PET analysis showed progressive decrease of binding potential values in the striatum of monkeys throughout MPTP administration and the development of parkinsonian signs. 18F-FDG analysis in asymptomatic and recovered animals showed significant hypometabolism in temporal and parietal areas of the cerebral cortex in association with moderate dopaminergic nigrostriatal depletion. Cortical hypometabolism extended to involve a larger area in mild parkinsonian monkeys, which also exhibited hypermetabolism in the globus pallidum pars interna and cerebellum. In severe parkinsonian monkeys, cortical hypometabolism extended further to lateral-frontal cortices and hypermetabolism also ensued in the thalamus and cerebellum. Unbiased histological quantification of neurons in Brodmann's area 7 in the parietal cortex did not reveal neuron loss in parkinsonian monkeys versus controls. Early dopaminergic nigrostriatal depletion is associated with cortical, mainly temporo-parietal hypometabolism unrelated to neuron loss. These findings, together with recent evidence from Parkinson's Disease patients, suggest that early cortical hypometabolism may be associated and driven by subcortical changes that need to be evaluated appropriately. Altogether, these findings could be relevant when potential disease modifying therapies become available.
•Major features of early PD metabolism are recapped in the parkinsonian monkey model.•Early dopamine loss is related with cortical, mainly temporo-parietal hypometabolism.•Cortical hypometabolism is not related to neuronal loss in the cortex.
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