Development of appropriate dendritic arbors is crucial for neuronal information transfer. We show, using seizure-related gene 6 (
sez-6) null mutant mice, that Sez-6 is required for normal dendritic ...arborization of cortical neurons. Deep-layer pyramidal neurons in the somatosensory cortex of
sez-6 null mice exhibit an excess of short dendrites, and cultured cortical neurons lacking Sez-6 display excessive neurite branching. Overexpression of individual Sez-6 isoforms in knockout neurons reveals opposing actions of membrane-bound and secreted Sez-6 proteins, with membrane-bound Sez-6 exerting an antibranching effect under both basal and depolarizing conditions. Layer V pyramidal neurons in knockout brain slices show reduced excitatory postsynaptic responses and a reduced dendritic spine density, reflected by diminished punctate staining for postsynaptic density 95 (PSD-95). In behavioral tests, the
sez-6 null mice display specific exploratory, motor, and cognitive deficits. In conclusion, cell-surface protein complexes involving Sez-6 help to sculpt the dendritic arbor, in turn enhancing synaptic connectivity.
The CORNISH project is the highest resolution radio continuum survey of the Galactic plane to date. It is the 5 GHz radio continuum part of a series of multi-wavelength surveys that focus on the ...northern GLIMPSE region (10degrees < l < 65degrees), observed by the Spitzer satellite in the mid-infrared. Observations with the Very Large Array in B and BnA configurations have yielded a 1".5 resolution Stokes I map with a root mean square noise level better than 0.4 mJy beam super(-1). Here we describe the data-processing methods and data characteristics, and present a new, uniform catalog of compact radio emission. This includes an implementation of automatic deconvolution that provides much more reliable imaging than standard CLEANing. A rigorous investigation of the noise characteristics and reliability of source detection has been carried out. We show that the survey is optimized to detect emission on size scales up to 14" and for unresolved sources the catalog is more than 90% complete at a flux density of 3.9 mJy. We have detected 3062 sources above a 7sigma detection limit and present their ensemble properties. The catalog is highly reliable away from regions containing poorly sampled extended emission, which comprise less than 2% of the survey area. Imaging problems have been mitigated by down-weighting the shortest spacings and potential artifacts flagged via a rigorous manual inspection with reference to the Spitzer infrared data. We present images of the most common source types found: H II regions, planetary nebulae, and radio galaxies. The CORNISH data and catalog are available online at http://cornish.leeds.ac.uk.
Flow cytometry provides robust, multi-parametric and quantitative information on single cells which also exhibits enormous potential as a tool for small particle characterisation. Small extracellular ...vesicle (sEV) detection by flow cytometry remains compromised due to the high prevalence of swarm detection, which is defined by the simultaneous illumination of more than one sEV, recorded as a single event. Detection of sEVs by imaging flow cytometry presents a major advantage by having the ability to resolve single particles from swarm detection based on the image features recorded for each event. In this study, we provide a simplified protocol that facilitates the removal of both swarm events and aggregated particles to improve the accuracy of sEV analysis. Our results indicate that imaging flow cytometry should be at the forefront as a robust and sensitive technique for sEV characterisation.
•Imaging flow cytometry provides a sensitivity platform for quantification of small extracellular vesicles (sEVs)•Challenges surrounding detection of single sEV particles hinder downstream analysis•Utilisation of advanced imaging flow cytometry features permits accurate single particle characterisation.
An extant stock of wild pallid sturgeon Scaphirhynchus albus persists in the fragmented upper Missouri River basin of Montana and North Dakota. Although successful spawning and hatch of embryos has ...been verified, long‐term catch records suggest that recruitment has not occurred for several decades as the extant stock lacks juvenile size classes and is comprised exclusively of large, presumably old individuals. Ages of 11 deceased (death years 1997–2007) wild S. albus (136–166 cm fork length) were estimated based on pectoral fin spines, sagittal otoliths and bomb radiocarbon (¹⁴C) assays of otoliths to test the hypothesis that members of this stock are old and to provide inferences on recruitment years that produced the extant stock. Age estimations based on counts of presumed annuli were about 2 years greater for otoliths (mean = 51 years, range = 43–57 years) than spines (mean = 49 years, range = 37–59 years). Based on ¹⁴C assays, confirmed birth years for all individuals occurred prior to 1957, thus establishing known longevity of at least 50 years. Estimated age based on presumed otolith annuli for one S. albus was validated to at least age 49. Although ¹⁴C assays confirmed pre‐1957 birth years for all S. albus, only 56% of estimated ages from spines and 91% of estimated ages from otoliths depicted pre‐1957 birth years. Both ageing structures were subject to under‐ageing error (up to 15 years). Lack of or severe curtailment of S. albus recruitment in the upper Missouri River basin since the mid‐1950s closely parallels the 1953–1957 timeframe when a mainstem reservoir was constructed and started to fill. This reservoir may function as a system‐wide stressor to diminish recruitment success of S. albus in the upper Missouri River basin.
Pacific Northwest National Laboratory has recently opened a shallow underground laboratory intended for measurement of low-concentration levels of radioactive isotopes in samples collected from the ...environment. The development of a low-background liquid scintillation counter is currently underway to further augment the measurement capabilities within this underground laboratory. Liquid scintillation counting is especially useful for measuring charged particle (e.g., β and α) emitting isotopes with no (or very weak) gamma-ray yields. The combination of high-efficiency detection of charged particle emission in a liquid scintillation cocktail coupled with the low-background environment of an appropriately designed shield located in a clean underground laboratory provides the opportunity for increased-sensitivity measurements of a range of isotopes. To take advantage of the 35m-water-equivalent overburden of the underground laboratory, a series of simulations have evaluated the scintillation counter's shield design requirements to assess the possible background rate achievable. This report presents the design and background evaluation for a shallow underground, low background liquid scintillation counter design for sample measurements.
•Graded-shielding can produce an ultra-low-background liquid scintillation counter.•Location in a shallow underground cleanroom further enhances background reduction.•A novel light collection design and selected low background materials are utilized.•The background is predicted to be 10–100 times below typical commercial systems.•Simulations tentatively predict a background rate of order 10 counts per day.
Abstract The superb image quality, stability, and sensitivity of JWST permit deconvolution techniques to be pursued with a fidelity unavailable to ground-based observations. We present an assessment ...of several deconvolution approaches to improve image quality and mitigate the effects of the complex JWST point-spread function (PSF). The optimal deconvolution method is determined by using WebbPSF to simulate JWST’s complex PSF and MIRISim to simulate multiband JWST/Mid-Infrared Imager Module (MIRIM) observations of a toy model of an active galactic nucleus (AGN). Five different deconvolution algorithms are tested: (1) Kraken deconvolution, (2) Richardson–Lucy, (3) the adaptive imaging deconvolution algorithm, (4) sparse regularization with the Condat–Vũ algorithm, and (5) iterative Wiener filtering and thresholding. We find that Kraken affords the greatest FWHM reduction of the nuclear source of our MIRISim observations for the toy AGN model while retaining good photometric integrity across all simulated wave bands. Applying Kraken to Galactic Activity, Torus, and Outflow Survey (GATOS) multiband JWST/MIRIM observations of the Seyfert 2 galaxy NGC 5728, we find that the algorithm reduces the FWHM of the nuclear source by a factor of 1.6–2.2 across all five filters. Kraken images facilitate detection of extended nuclear emission ∼2.″5 (∼470 pc, position angle ≃ 115°) in the SE–NW direction, especially at the longest wavelengths. We demonstrate that Kraken is a powerful tool to enhance faint features otherwise hidden in the complex JWST PSF.
The Ultra-Low Background Liquid Scintillation Counter developed by Pacific Northwest National Laboratory will expand the application of liquid scintillation counting by enabling lower detection ...limits and smaller sample volumes. By reducing the overall count rate of the background environment approximately 2 orders of magnitude below that of commercially available systems, backgrounds on the order of tens of counts per day over an energy range of ~3–3600keV can be realized. Initial test results of the ULB LSC show promising results for ultra-low background detection with liquid scintillation counting.
•Observed background is within a factor of 2 of the predictions from simulation.•Background achieved is 2 orders of magnitude below commercially available systems.•Backgrounds are in tens of counts per day over an energy range of ~3– 3600keV.•Initial results show promise for ultra-low background detection with the ULB LSC.
Over a dozen millisecond pulsars are ablating low-mass companions in close binary systems. In the original 'black widow', the eight-hour orbital period eclipsing pulsar PSR J1959+2048 (PSR B1957+20)
..., high-energy emission originating from the pulsar
is irradiating and may eventually destroy
a low-mass companion. These systems are not only physical laboratories that reveal the interesting results of exposing a close companion star to the relativistic energy output of a pulsar, but are also believed to harbour some of the most massive neutron stars
, allowing for robust tests of the neutron star equation of state. Here we report observations of ZTF J1406+1222, a wide hierarchical triple hosting a 62-minute orbital period black widow candidate, the optical flux of which varies by a factor of more than ten. ZTF J1406+1222 pushes the boundaries of evolutionary models
, falling below the 80-minute minimum orbital period of hydrogen-rich systems. The wide tertiary companion is a rare low-metallicity cool subdwarf star, and the system has a Galactic halo orbit consistent with passing near the Galactic Centre, making it a probe of formation channels, neutron star kick physics
and binary evolution.
Prominence cavities in coronal helmet streamers are readily detectable in white-light coronagraph images, yet their interpretation may be complicated by projection effects. In order to determine a ...cavity's density structure, it is essential to quantify the contribution of noncavity features along the line of sight. We model the coronal cavity as an axisymmetric torus that encircles the Sun at constant latitude and fit it to observations of a white- light cavity observed by the Mauna Loa Solar Observatory (MLSO) MK4 coronagraph from 2006 January 25 to 30. We demonstrate that spurious noncavity contributions (including departures from axisymmetry) are minimal enough to be incorporated in a density analysis as conservatively estimated uncertainties in the data. We calculate a radial density profile for cavity material and for the surrounding helmet streamer (which we refer to as the 'cavity rim') and find that the cavity density is depleted by a maximum of 40% compared to the surrounding helmet streamer at low altitudes (1.18 R sub(image)) but is consistently higher (double or more) than in coronal holes. We also find that the relative density depletion between cavity and surrounding helmet decreases as a function of height. We show that both increased temperature in the cavity relative to the surrounding helmet streamer and a magnetic flux rope configuration might lead to such a flattened density profile. Finally, our model provides general observational guidelines that can be used to determine when a cavity is sufficiently unobstructed to be a good candidate for plasma diagnostics.
Extreme events, such as heat waves, are predicted to increase in frequency, duration, and severity as a consequence of climate change. However, global change research generally focuses on increases ...in mean temperatures and fails to address the potential impacts of increasingly severe heat waves. In addition, climate change may interact with another primary threat to biodiversity, non‐native species invasions. We assessed the impacts of a short‐term heat wave on the marine epibenthic fouling community of Bodega Harbor, California, USA, by exposing experimental mesocosms to a simulated heat wave in the laboratory and then monitoring community development in the field. We hypothesized that (1) juveniles would be more susceptible to heat waves than adults, (2) native species would be more susceptible than non‐native species, and (3) non‐native species would recover more quickly than native species. We observed no effect of the heat wave on juvenile species richness, either initially or during the recovery period, relative to communities at ambient seawater temperatures. In contrast, total adult species richness initially declined in response to the heat wave. Adult community composition also changed in heat‐wave treatments, with non‐natives representing the majority of species and occupying more cover than native species. The reduction in native richness associated with the heat wave persisted through the recovery period, whereas invasive richness was actually higher on heat‐wave versus ambient plates at 95 days. Heat waves have the potential to alter the composition of this community because of species‐, taxon‐, and/or origin‐specific responses; for example, non‐native bryozoans displayed greater resistance than native and non‐native tunicates. Recovery from the heat wave occurred via growth of resistant individuals and larval recruitment. Our study highlights the importance of considering species' and community responses to heat waves, and not just mean predicted temperature increases, to evaluate the consequences of climate change.
PDF
