In recent work with large high-symmetry viruses, single-particle electron cryomicroscopy (cryo-EM) has achieved the determination of near-atomic-resolution structures by allowing direct fitting of ...atomic models into experimental density maps. However, achieving this goal with smaller particles of lower symmetry remains challenging. Using a newly developed single electron-counting detector, we confirmed that electron beam-induced motion substantially degrades resolution, and we showed that the combination of rapid readout and nearly noiseless electron counting allow image blurring to be corrected to subpixel accuracy, restoring intrinsic image information to high resolution (Thon rings visible to ∼3 Å). Using this approach, we determined a 3.3-Å-resolution structure of an ∼700-kDa protein with D7 symmetry, the Thermoplasma acidophilum 20S proteasome, showing clear side-chain density. Our method greatly enhances image quality and data acquisition efficiency-key bottlenecks in applying near-atomic-resolution cryo-EM to a broad range of protein samples.
The mitotic spindle must function in cell types that vary greatly in size, and its dimensions scale with the rapid, reductive cell divisions that accompany early stages of development. The mechanism ...responsible for this scaling is unclear, because uncoupling cell size from a developmental or cellular context has proven experimentally challenging. We combined microfluidic technology with Xenopus egg extracts to characterize spindle assembly within discrete, geometrically defined volumes of cytoplasm. Reductions in cytoplasmic volume, rather than developmental cues or changes in cell shape, were sufficient to recapitulate spindle scaling observed in Xenopus embryos. Thus, mechanisms extrinsic to the spindle, specifically a limiting pool of cytoplasmic component(s), play a major role in determining spindle size.
We describe a new post-column imaging energy filter for (scanning) transmission electron microscopy from 60 to 300
kV operating voltage. The completely redesigned GIF quantum has a gradient magnetic ...prism, dodecapole optics, a 10-times faster 40
Mpixel/sec CCD camera, a 1
μs electrostatic shutter, and new user interface, control, and auto-alignment software. An 8 dodecapole lens system, performs full 2nd and 3rd, and partial 4th and 5th order aberration correction. The improved aberration correction has allowed the size of the entrance aperture to be nearly doubled to 9.0
mm compared to current generation post-column designs. The electrostatic shutter provides exposure control down to 1
μs, extending the exposure time range to over 7 orders of magnitude. Spectroscopy operation has been improved with a larger 2
keV field of view at 200
kV, and a maximum acquisition rate of 1000 spectra per second. A high-speed DualEELS mode simultaneously acquires core- and low-loss spectra up to 2
keV apart. A more intuitive user interface includes new capabilities such as automated exposure control and optimized full spectrum acquisition. The auto-alignment software has been significantly enhanced to use the full flexibility of the dodecapole lens system.
It is known that
Microsetella norvegica
feed on phytoplankton and provide an important link to higher trophic levels in Arctic fjords, such as fish sprat (
Sprattus sprattus
) and three-spined ...stickleback (
Gasterosteus aculeatus
). It has recently been suggested that
M. norvegica
may also contribute substantially to carbon flux attenuation during periods of high abundance. However, we still know very little about how seasonal variations in abundance and vertical distribution of
M. norvegica
impact the efficiency of the biological carbon pump in Arctic fjords. We investigated the role of
Microsetella norvegica
, a small harpacticoid copepod, for particulate organic carbon flux attenuation via aggregate feeding in a subarctic fjord. We quantified the vertical distribution and abundance of
M. norvegica
, phytoplankton, and marine snow simultaneously with a Digital Autonomous Video Plankton Recorder in Porsangerfjord, northern Norway, between August 2013 and November 2014. We estimated the highest abundance of
M. norvegica
as 4.86x10
6
individuals m
-2
in October. Our results suggest that
M. norvegica
preferred diatoms over both marine snow and the prymnesiophyte
Phaeocystis pouchetii
during euphotic bloom conditions. However, during oligotrophic conditions when phytoplankton were scarce,
M. norvegica
switched to marine snow as a food source.
M. norvegica
has the potential to explain 1.4% and 0.29% of the total carbon flux attenuation in October and November, respectively. These results suggest that small copepods feed on settling detritus when no alternative food is available. Detritus feeding by
M. norvegica
may have an ecological impact during the polar night, both via direct carbon flux attenuation, but also as secondary producers in periods with low primary production. Currently small copepods such as
M. norvegica
are not included in carbon budgets or large-scale modelling, but considering their potentially high abundance they may represent an important but overlooked pathway in both the carbon cycle and trophic level interactions.
This study adapts and validates a scale designed to measure Attitudes Toward Mentally Disordered Offenders (ATMDO). It is thought that by monitoring and subsequently improving attitudes, negative ...potentially damaging milieus within criminal justice, forensic mental health, and society in general can be minimized. Participants (N = 364) were recruited via snowball technique and data collected using an online version of the ATMDO. Psychometric properties were assessed. Test-retest and convergent validity was assessed with additional samples A (N = 30) and B (N = 50) respectively. Utilizing a cross-sectional design, differences in ATMDO scores across occupational groups were compared. The ATMDO demonstrates robust internal structure, reliability, and validity. Although ATMDO scores did not differ significantly across occupational groups, some differences were seen at a factorial level. Regression analysis demonstrates the influence of both demographic and occupation-related variables in predicting ATMDO scores. The ATMDO is robust and has clinical utility for comparison of professional groups or institutions, and within recruitment procedures. A model is proposed for the effects of exposure (catalyst factor) and professional certification training (moderating factor).
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