ABSTRACT
Millisecond pulsars are mainly characterized by their spin periods, B-fields and masses - quantities that are largely affected by previous interactions with a companion star in a binary ...system. In this paper, we investigate the formation mechanism of millisecond pulsars by considering the pulsar recycling process in both intermediate-mass X-ray binaries (IMXBs) and low-mass X-ray binaries (LMXBs). The IMXBs mainly lead to the formation of binary millisecond pulsars with a massive carbon-oxygen (CO) or an oxygen-neon-magnesium white dwarf (ONeMg WD) companion, whereas the LMXBs form recycled pulsars with a helium white dwarf (He WD) companion. We discuss the accretion physics leading to the spin-up line in the -diagram and demonstrate that such a line cannot be uniquely defined. We derive a simple expression for the amount of accreted mass needed for any given pulsar to achieve its equilibrium spin and apply this to explain the observed differences of the spin distributions of recycled pulsars with different types of companions. From numerical calculations we present further evidence for significant loss of rotational energy in accreting X-ray millisecond pulsars in LMXBs during the Roche-lobe decoupling phase (Tauris 2012) and demonstrate that the same effect is negligible in IMXBs. We examine the recycling of pulsars with CO WD companions via Case BB Roche-lobe overflow (RLO) of naked helium stars in post-common envelope binaries. We find that such pulsars typically accrete of the order of 0.002-0.007 M⊙ which is just about sufficient to explain their observed spin periods. We introduce isochrones of radio millisecond pulsars in the -diagram to follow their spin evolution and discuss their true ages from comparison with observations. Finally, we apply our results of the spin-up process to complement our investigation of the massive pulsar PSR J1614−2230 from Paper I, confirming that this system formed via stable Case A RLO in an IMXB and enabling us to put new constraints on the birth masses of a number of recycled pulsars.
On coral reefs, the epilithic algal matrix (EAM) is widely recognised as an important resource for herbivorous and detritivorous fishes. In comparison, little is known of the interaction between ...benthic carnivores and the EAM, despite the abundance of Crustacea within the EAM. The trophic importance of the EAM to fishes was investigated in Pioneer Bay, Orpheus Island, Great Barrier Reef. Fish densities were quantified using visual and clove oil censuses, and gut content analyses conducted on abundant fish species. Crustaceans were found to be an important dietary category, contributing between 49.5 and 100 % of the gut contents, with harpacticoid copepods being the dominant component. Of the benthic carnivores, the goby
Eviota zebrina
was found to consume the most harpacticoids with a mean of 249 copepods m
−2
day
−1
. This represents approximately 0.1 % of the available harpacticoid population in the EAM. In a striking comparison, herbivorous parrotfishes were estimated to consume over 12,000 harpacticoids m
−2
day
−1
, over 27 times more than all benthic carnivores surveyed, representing approximately 5.3 % of the available harpacticoid copepod population each day. The high consumption of harpacticoid copepods by benthic carnivores and parrotfishes indicates that harpacticoids form an important trophic link between the EAM and higher trophic levels on coral reefs.
Fast radio bursts (FRBs) are one of the most tantalizing mysteries of the radio sky; their progenitors and origins remain unknown and until now no rapid multiwavelength follow-up of an FRB has been ...possible. New instrumentation has decreased the time between observation and discovery from years to seconds, and enables polarimetry to be performed on FRBs for the first time. We have discovered an FRB (FRB 140514) in real-time on 2014 May 14 at 17:14:11.06 UTC at the Parkes radio telescope and triggered follow-up at other wavelengths within hours of the event. FRB 140514 was found with a dispersion measure (DM) of 562.7(6) cm−3 pc, giving an upper limit on source redshift of z ≲ 0.5. FRB 140514 was found to be 21 ± 7 per cent (3σ) circularly polarized on the leading edge with a 1σ upper limit on linear polarization <10 per cent. We conclude that this polarization is intrinsic to the FRB. If there was any intrinsic linear polarization, as might be expected from coherent emission, then it may have been depolarized by Faraday rotation caused by passing through strong magnetic fields and/or high-density environments. FRB 140514 was discovered during a campaign to re-observe known FRB fields, and lies close to a previous discovery, FRB 110220; based on the difference in DMs of these bursts and time-on-sky arguments, we attribute the proximity to sampling bias and conclude that they are distinct objects. Follow-up conducted by 12 telescopes observing from X-ray to radio wavelengths was unable to identify a variable multiwavelength counterpart, allowing us to rule out models in which FRBs originate from nearby (z < 0.3) supernovae and long duration gamma-ray bursts.
Kleefstra syndrome, caused by haploinsufficiency of euchromatin histone methyltransferase 1 (EHMT1), is characterized by intellectual disability (ID), autism spectrum disorder (ASD), characteristic ...facial dysmorphisms, and other variable clinical features. In addition to EHMT1 mutations, de novo variants were reported in four additional genes (MBD5, SMARCB1, NR1I3, and KMT2C), in single individuals with clinical characteristics overlapping Kleefstra syndrome. Here, we present a novel cohort of five patients with de novo loss of function mutations affecting the histone methyltransferase KMT2C. Our clinical data delineates the KMT2C phenotypic spectrum and reinforces the phenotypic overlap with Kleefstra syndrome and other related ID disorders. To elucidate the common molecular basis of the neuropathology associated with mutations in KMT2C and EHMT1, we characterized the role of the Drosophila KMT2C ortholog, trithorax related (trr), in the nervous system. Similar to the Drosophila EHMT1 ortholog, G9a, trr is required in the mushroom body for short term memory. Trr ChIP-seq identified 3371 binding sites, mainly in the promoter of genes involved in neuronal processes. Transcriptional profiling of pan-neuronal trr knockdown and G9a null mutant fly heads identified 613 and 1123 misregulated genes, respectively. These gene sets show a significant overlap and are associated with nearly identical gene ontology enrichments. The majority of the observed biological convergence is derived from predicted indirect target genes. However, trr and G9a also have common direct targets, including the Drosophila ortholog of Arc (Arc1), a key regulator of synaptic plasticity. Our data highlight the clinical and molecular convergence between the KMT2 and EHMT protein families, which may contribute to a molecular network underlying a larger group of ID/ASD-related disorders.
Anthropogenic impacts on biodiversity can lead to biotic homogenization (BH) and biotic differentiation (BD). BH is a process of increasing similarity in community composition (including taxonomic, ...functional, and phylogenetic components), whereas BD is a process of decreasing similarity over space and time. Here, we conducted a systematic review of BH and BD in plant communities in tropical and subtropical forests to identify trends and knowledge gaps. Our bibliometric search in the Web of Science returned 1989 papers, of which 151 matched our criteria and were included in the analysis. The Neotropical region had the largest number of articles, and Brazil was the most represented country with 92 studies. Regarding the type of change, homogenization was more frequent than differentiation (noted in 69.6% of publications). The taxonomic diversity component was measured more often than functional and phylogenetic diversity components. Most studies (75.6%) assessed homogenization and differentiation based on a single observation in time; as opposed to few studies that monitored plant community over multiple years. Forest fragmentation was cited as the main determinant of homogenization and differentiation processes (57.2% of articles). Our results highlight the importance of evaluating community composition over time and more than taxonomic components (i.e., functional and phylogenetic) to advance understanding of homogenization and differentiation. Both processes were scale dependent and not mutually exclusive. As such, future research should consider differentiation as a potential transition phase to homogenization and that potential differences in both processes may depend on the spatial and temporal scale adopted. Understanding the complexity and causes of homogenization and differentiation is essential for biodiversity conservation in a world increasingly affected by anthropogenic disturbances.
Resumen
Los impactos antropogénicos sobre la biodiversidad pueden resultar en la homogenización y diferenciación biótica. La homogenización biótica consiste en una creciente similitud de la composición comunitaria (incluidos los componentes taxonómicos, funcionales y filogenéticos), mientras que la diferenciación biótica conlleva la disminución en similitudes a lo largo del tiempo y el espacio. En este trabajo realizamos una revisión sistemática de la homogenización y diferenciación biótica en las comunidades vegetales en los bosques tropicales y subtropicales para identificar tendencias y vacíos de conocimiento. Nuestra búsqueda bibliométrica en Web of Science produjo 1989 artículos, de los cuales 151 cumplieron con nuestros criterios y fueron incluidos en el análisis. La región neotropical tuvo el mayor número de artículos y Brasil fue el país más representado con 92 estudios. Con respecto al tipo de cambio, la homogenización fue más frecuente que la diferenciación (reportada en 69.6% de las publicaciones). El componente de diversidad taxonómica se midió más veces que los componentes de diversidad funcional y filogenética. La mayoría de los estudios (75.6%) examinó la homogenización y la diferenciación con base en una sola observación en el tiempo; unos cuantos estudios sí monitorearon las comunidades vegetales a través de varios años. Se citó a la fragmentación del bosque como el principal determinante de los procesos de homogenización y diferenciación (57.2% de los artículos). Nuestros resultados resaltan la importancia de la evaluación de la composición de la comunidad a través del tiempo y más allá de los componentes taxonómicos para propiciar el entendimiento de la homogenización y la diferenciación. Ambos procesos dependieron de la escala y no se excluyeron mutuamente. Por lo tanto, las siguientes investigaciones deberían considerar a la diferenciación como una fase potencial de transición hacia la homogenización y que las posibles diferencias en ambos procesos podrían depender de la escala espacial y temporal aplicada. Son esenciales el entendimiento de la complejidad y las causas de la homogenización y la diferenciación para la conservación de la biodiversidad en un planeta que cada vez se ve más afectado por las perturbaciones antropogénicas.
【摘要】
人类活动对生物多样性的影响可以导致生物同质化和分化。生物同质化是群落组成(包括类群、功能和系统发育组分)相似性增加的过程, 而生物分化则是在时空上相似性减少的过程。本文对热带和亚热带森林植物群落的生物同质化和分化进行了系统综述, 确定了研究趋势和知识空缺。我们在Web of Science网站上进行文献检索, 得到了1989篇论文, 其中151篇符合我们的标准并被纳入分析。我们发现, 文章数量最多的地区是新热带区, 而研究涉及最多的国家是巴西, 有92项研究。在两种变化类型中, 同质化比分化的研究更多(有69.6%的发表论文中提及)。研究中类群多样性组分比功能和系统发育多样性组分测量得更多。大多数研究(75.6%)只基于单次观察来评估同质化和分化, 少数研究对植物群落进行了多年监测。此外, 森林破碎化被认为是同质化和分化过程的主要决定因素(57.2%的文章)。我们的结果强调了对群落组成进行长期评估及类群组分以外(即功能和系统发育组分)研究的重要性, 以帮助促进对同质化和分化的理解。这两个过程都是尺度依赖的, 且并不相互排斥。因此, 未来的研究应将分化视为同质化的一个潜在过渡阶段, 这两个过程的潜在差异可能取决于研究采用的空间和时间尺度。了解同质化和分化的复杂性及原因, 对于在人为干扰日渐加剧的背景下保护生物多样性至关重要。【翻译:胡怡思;审校:聂永刚】
Abstract Background Several triage systems have been developed for use in the emergency department (ED), however they are not designed to detect deterioration in patients. Deteriorating patients may ...be at risk of going undetected during their ED stay and are therefore vulnerable to develop serious adverse events (SAEs). The National Early Warning Score (NEWS) has a good ability to discriminate ward patients at risk of SAEs. The utility of NEWS had not yet been studied in an ED. Objective To explore the performance of the NEWS in an ED with regard to predicting adverse outcomes. Design A prospective observational study. Patients Eligible patients were those presenting to the ED during the 6 week study period with an Emergency Severity Index (ESI) of 2 and 3 not triaged to the resuscitation room. Intervention NEWS was documented at three time points: on arrival (T0), hour after arrival (T1) and at transfer to the general ward/ICU (T2). The outcomes of interest were: hospital admission, ICU admission, length of stay and 30 day mortality. Results A total of 300 patients were assessed for eligibility. Complete data was able to be collected for 274 patients on arrival at the ED. NEWS was significantly correlated with patient outcomes, including 30 day mortality, hospital admission, and length of stay at all-time points. Conclusion The NEWS measured at different time points was a good predictor of patient outcomes and can be of additional value in the ED to longitudinally monitor patients throughout their stay in the ED and in the hospital.
In light of the recently discovered neutron star populations, we discuss the various estimates for the birthrates of these populations. We revisit the question as to whether the Galactic supernova ...rate can account for all of the known groups of isolated neutron stars. After reviewing the rates and population estimates, we find that if the estimates are in fact accurate, the current birthrate and population estimates are not consistent with the Galactic supernova rate. We discuss possible solutions to this problem including whether or not some of the birthrates are hugely overestimated. We also consider a possible evolutionary scenario between some of the known neutron star classes which could solve this potential birthrate problem.
Aims
To determine the acute effect of glucagon‐like peptide‐1 (GLP‐1) receptor agonist exenatide and the involvement of nitric oxide (NO) on renal haemodynamics and tubular function, in healthy ...overweight men.
Methods
Renal haemodynamics and tubular electrolyte handling were measured in 10 healthy overweight men (aged 20–27 years; BMI 26–31 kg/m2) during intravenous administration of placebo (saline 0.9%), exenatide, and exenatide combined with the NO‐synthase inhibitor L‐NG‐monomethyl arginine (L‐NMMA). Glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were determined by inulin and para‐aminohippurate clearance techniques, respectively, based on timed urine sampling. Glomerular hydrostatic pressure and vascular resistance of afferent and efferent renal arterioles were calculated using the Gomez formulae. Urinary electrolytes, osmolality and pH were also measured.
Results
GFR increased by a mean of 18 ± 20 (+20%; p = 0.021) and ERPF increased by a median (interquartile range) of 68 (26; 197) ml/min/1.73 m2 (+14%; p = 0.015) during exenatide infusion versus placebo. During L‐NMMA infusion, exenatide increased GFR by mean 8 ± 12 ml/min/1.73 m2 (+9%; p = 0.049). Exenatide increased estimated glomerular pressure by +6% (p = 0.015) and reduced afferent renal vascular resistance by −33% (p = 0.038), whereas these effects were blunted during L‐NMMA infusion. Exenatide increased absolute and fractional sodium excretion, urinary osmolality and urinary pH. The tubular effects of exenatide were not altered by concomitant L‐NMMA infusion.
Conclusions
Exenatide infusion in healthy overweight men acutely increases GFR, ERPF and glomerular pressure, probably by reducing afferent renal vascular resistance, and at least partially in an NO‐dependent manner. As baseline renal haemodynamics in patients with type 2 diabetes differ from those in healthy individuals, clinical studies on the renal effects of GLP‐1 receptor agonists are warranted.
Scattering analysis of LOFAR pulsar observations Geyer, M; Karastergiou, A; Kondratiev, V. I ...
Monthly notices of the Royal Astronomical Society,
09/2017, Letnik:
470, Številka:
3
Journal Article
Recenzirano
Odprti dostop
Abstract
We measure the effects of interstellar scattering on average pulse profiles from 13 radio pulsars with simple pulse shapes. We use data from the LOFAR High Band Antennas, at frequencies ...between 110 and 190 MHz. We apply a forward fitting technique, and simultaneously determine the intrinsic pulse shape, assuming single Gaussian component profiles. We find that the constant τ, associated with scattering by a single thin screen, has a power-law dependence on frequency τ ∝ ν−α, with indices ranging from α = 1.50 to 4.0, despite simplest theoretical models predicting α = 4.0 or 4.4. Modelling the screen as an isotropic or extremely anisotropic scatterer, we find anisotropic scattering fits lead to larger power-law indices, often in better agreement with theoretically expected values. We compare the scattering models based on the inferred, frequency-dependent parameters of the intrinsic pulse, and the resulting correction to the dispersion measure (DM). We highlight the cases in which fits of extreme anisotropic scattering are appealing, while stressing that the data do not strictly favour either model for any of the 13 pulsars. The pulsars show anomalous scattering properties that are consistent with finite scattering screens and/or anisotropy, but these data alone do not provide the means for an unambiguous characterization of the screens. We revisit the empirical τ versus DM relation and consider how our results support a frequency dependence of α. Very long baseline interferometry, and observations of the scattering and scintillation properties of these sources at higher frequencies, will provide further evidence.
ABSTRACT
Detections from the repeating fast radio burst FRB 121102 are clustered in time, noticeable even in the earliest repeat bursts. Recently, it was argued that the source activity is periodic, ...suggesting that the clustering reflected a not-yet-identified periodicity. We performed an extensive multiwavelength campaign with the Effelsberg telescope, the Green Bank telescope, and the Arecibo Observatory to shadow the Gran Telescope Canaria (optical), NuSTAR (X-ray) and INTEGRAL (γ-ray). We detected 36 bursts with Effelsberg, one with a pulse width of 39 ms, the widest burst ever detected from FRB 121102. With one burst detected during simultaneous NuSTAR observations, we place a 5σ upper limit of 5 × 1047 erg on the 3–79 keV energy of an X-ray burst counterpart. We tested the periodicity hypothesis using 165 h of Effelsberg observations and find a periodicity of 161 ± 5 d. We predict the source to be active from 2020 July 9 to October 14 and subsequently from 2020 December 17 to 2021 March 24. We compare the wait times between consecutive bursts within a single observation to Weibull and Poisson distributions. We conclude that the strong clustering was indeed a consequence of a periodic activity and show that if the few events with millisecond separation are excluded, the arrival times are Poisson distributed. We model the bursts’ cumulative energy distribution with energies from ∼1038–1039 erg and find that it is well described by a power law with slope of γ = −1.1 ± 0.2. We propose that a single power law might be a poor descriptor of the data over many orders of magnitude.
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