220 research outputs found
Surface display of heterologous proteins in Bacillus thuringiensis using a peptidoglycan hydrolase anchor
<p>Abstract</p> <p>Background</p> <p>Previous studies have revealed that the lysin motif (LysM) domains of bacterial cell wall-degrading enzymes are able to bind to peptidoglycan moieties of the cell wall. This suggests an approach for a cell surface display system in Gram-positive bacteria using a LysM-containing protein as the anchoring motif. In this study, we developed a new surface display system in <it>B. thuringiensis </it>using a LysM-containing peptidoglycan hydrolase, endo-<it>β</it>-<it>N</it>-acetylglucosaminidase (Mbg), as the anchor protein.</p> <p>Results</p> <p>Homology searching in the <it>B. thuringiensis </it>YBT-1520 genome revealed a putative peptidoglycan hydrolase gene. The encoded protein, Mbg, exhibited substantial cell-wall binding capacity. The deduced amino acid sequence of Mbg was structurally distinguished as an N-terminal domain with two tandemly aligned LysMs and a C-terminal catalytic domain. A GFP-fusion protein was expressed and used to verify the surface localization by Western blot, flow cytometry, protease accessibility, SDS sensitivity, immunofluorescence, and electron microscopy assays. Low-level constitutive expression of Mbg was elevated by introducing a sporulation-independent promoter of <it>cry3Aa</it>. Truncated Mbg domains with separate N-terminus (Mbgn), C-terminus (Mbgc), LysM<sub>1</sub>, or LysM<sub>2 </sub>were further compared for their cell-wall displaying efficiencies. The Mbgn moiety contributed to cell-wall anchoring, while LysM<sub>1 </sub>was the active domain. Two tandemly repeated Mbgns exhibited the highest display activity, while the activity of three repeated Mbgns was decreased. A heterologous bacterial multicopper oxidase (WlacD) was successfully displayed onto the surface of <it>B. thuringiensis </it>target cells using the optimum (Mbgn)<sub>2 </sub>anchor, without radically altering its catalytic activity.</p> <p>Conclusion</p> <p>Mbg can be a functional anchor protein to target different heterologous proteins onto the surface of <it>B. thuringiensis </it>cells. Since the LysM domain appears to be universal in Gram-positive bacteria, the strategy presented here could be applicable in other bacteria for developing this type of system.</p
Primary Disruption of the Memory-Related Subsystems of the Default Mode Network in Alzheimer’s Disease: Resting-State Functional Connectivity MRI Study
Background: Recent studies have indicated that the default mode network (DMN) comprises at least three subsystems: The medial temporal lobe (MTL) and dorsal medial prefrontal cortex (DMPFC) subsystems and a core comprising the anterior MPFC (aMPFC) and posterior cingulate cortex (PCC). Additionally, the disruption of the DMN is related to Alzheimer’s disease (AD). However, little is known regarding the changes in these subsystems in AD, a progressive disease characterized by memory impairment. Here, we performed a resting-state functional connectivity (FC) analysis to test our hypothesis that the memory-related MTL subsystem was predominantly disrupted in AD.Method: To reveal specific subsystem changes, we calculated the strength and number of FCS in the DMN intra- and inter-subsystems across individuals and compared the FC of the two groups. To further examine which pairs of brain regional functional connections contributed to the subsystem alterations, correlation coefficients between any two brain regions in the DMN were compared across groups. Additionally, to identify which regions made the strongest contributions to the subsystem changes, we calculated the regional FC strength (FCS), which was compared across groups.Results: For the intra-subsystem, decreased FC number and strength occurred in the MTL subsystem of AD patients but not in the DMPFC subsystem or core. For the inter-subsystems, the AD group showed decreased FCS and number between the MTL subsystem and PCC and a decreased number between the PCC and DMPFC subsystem. Decreased inter-regional FCS were found within the MTL subsystem in AD patients relative to controls: The posterior inferior parietal lobule (pIPL) showed decreased FC with the hippocampal formation (HF), parahippocampal cortex (PHC) and ventral MPFC (vMPFC). Decreased inter-regional FCS of the inter-subsystems were also found in AD patients: The HF and/or PHC showed decreased FC with dMPFC and TPJ, located in the DMPFC subsystem, and with PCC. AD patients also showed decreased FC between the PCC and TLC of the dMPFC subsystem. Furthermore, the HF and PHC in the MTL subsystem showed decreased regional FCS.Conclusion: Decreased intrinsic FC was mainly associated with the MTL subsystem of the AD group, suggesting that the MTL subsystem is predominantly disrupted
OmniZoomer: Learning to Move and Zoom in on Sphere at High-Resolution
Omnidirectional images (ODIs) have become increasingly popular, as their
large field-of-view (FoV) can offer viewers the chance to freely choose the
view directions in immersive environments such as virtual reality. The M\"obius
transformation is typically employed to further provide the opportunity for
movement and zoom on ODIs, but applying it to the image level often results in
blurry effect and aliasing problem. In this paper, we propose a novel deep
learning-based approach, called \textbf{OmniZoomer}, to incorporate the
M\"obius transformation into the network for movement and zoom on ODIs. By
learning various transformed feature maps under different conditions, the
network is enhanced to handle the increasing edge curvatures, which alleviates
the blurry effect. Moreover, to address the aliasing problem, we propose two
key components. Firstly, to compensate for the lack of pixels for describing
curves, we enhance the feature maps in the high-resolution (HR) space and
calculate the transformed index map with a spatial index generation module.
Secondly, considering that ODIs are inherently represented in the spherical
space, we propose a spherical resampling module that combines the index map and
HR feature maps to transform the feature maps for better spherical correlation.
The transformed feature maps are decoded to output a zoomed ODI. Experiments
show that our method can produce HR and high-quality ODIs with the flexibility
to move and zoom in to the object of interest. Project page is available at
http://vlislab22.github.io/OmniZoomer/.Comment: Accepted by ICCV 202
Radial force within two-stage axial-flow blood pump based on LES
Radial force in implantable two-stage axial flow blood pump (Artificial Heart) is a major factor affecting the operation stability. In order to investigate the transient operation characteristics of two-stage blood pumps, three-dimensional, unsteady numerical simulations were conducted by using the large eddy simulation (LES) model, PISO algorithm based on the sliding mesh technique in Fluent. The performance of the pump was obtained and compared with the experimental results. Besides, the radial force at various monitoring points were acquired; next, they were analyzed in time and frequency domains, respectively. It was demonstrated that the radial force at all the monitoring points changes periodically with time, its number of periods is identical to the number of blades but less affected by the number of guide vane blades, its frequency is close to the blade passing frequency. The frequency of radial force within the impeller increases gradually towards the impeller outlet and approaches the maximum value there, while the variation tendency of the frequency is opposite within the guide vane. The mostly dramatic radial force occurs at the impeller outlet, the main frequency at various monitoring points is almost equal to the impeller passing frequency. The amplitude of radial force coefficient at the monitoring points in the second stage impeller is higher than the first stage impeller. Additionally, the main frequency of radial force in the first stage impeller is different from the second stage guide vane
Context-Sensitive Temporal Feature Learning for Gait Recognition
Although gait recognition has drawn increasing research attention recently,
it remains challenging to learn discriminative temporal representation, since
the silhouette differences are quite subtle in spatial domain. Inspired by the
observation that human can distinguish gaits of different subjects by
adaptively focusing on temporal clips with different time scales, we propose a
context-sensitive temporal feature learning (CSTL) network for gait
recognition. CSTL produces temporal features in three scales, and adaptively
aggregates them according to the contextual information from local and global
perspectives. Specifically, CSTL contains an adaptive temporal aggregation
module that subsequently performs local relation modeling and global relation
modeling to fuse the multi-scale features. Besides, in order to remedy the
spatial feature corruption caused by temporal operations, CSTL incorporates a
salient spatial feature learning (SSFL) module to select groups of
discriminative spatial features. Particularly, we utilize transformers to
implement the global relation modeling and the SSFL module. To the best of our
knowledge, this is the first work that adopts transformer in gait recognition.
Extensive experiments conducted on three datasets demonstrate the
state-of-the-art performance. Concretely, we achieve rank-1 accuracies of
98.7%, 96.2% and 88.7% under normal-walking, bag-carrying and coat-wearing
conditions on CASIA-B, 97.5% on OU-MVLP and 50.6% on GREW.Comment: Submitted to TPAM
Massive Star-Forming Galaxies Have Converted Most of Their Halo Gas into Stars
In the local Universe, the efficiency for converting baryonic gas into stars
is very low. In dark matter halos where galaxies form and evolve, the average
efficiency varies with galaxy stellar mass and has a maximum of about twenty
percent for Milky-Way-like galaxies. The low efficiency at higher mass is
believed to be produced by some quenching processes, such as the feedback from
active galactic nuclei. We perform an analysis of weak lensing and satellite
kinematics for SDSS central galaxies. Our results reveal that the efficiency is
much higher, more than sixty percent, for a large population of massive
star-forming galaxies around . This suggests that these
galaxies acquired most of the gas in their halos and converted it into stars
without being affected significantly by quenching processes. This population of
galaxies is not reproduced in current galaxy formation models, indicating that
our understanding of galaxy formation is incomplete. The implications of our
results on circumgalactic media, star formation quenching and disc galaxy
rotation curves are discussed. We also examine systematic uncertainties in
halo-mass and stellar-mass measurements that might influence our results.Comment: Accepted for publication in A&A; 15 pages, 13 figure
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