24 research outputs found
NeRF-VINS: A Real-time Neural Radiance Field Map-based Visual-Inertial Navigation System
Achieving accurate, efficient, and consistent localization within an a priori
environment map remains a fundamental challenge in robotics and computer
vision. Conventional map-based keyframe localization often suffers from
sub-optimal viewpoints due to limited field of view (FOV), thus degrading its
performance. To address this issue, in this paper, we design a real-time
tightly-coupled Neural Radiance Fields (NeRF)-aided visual-inertial navigation
system (VINS), termed NeRF-VINS. By effectively leveraging NeRF's potential to
synthesize novel views, essential for addressing limited viewpoints, the
proposed NeRF-VINS optimally fuses IMU and monocular image measurements along
with synthetically rendered images within an efficient filter-based framework.
This tightly coupled integration enables 3D motion tracking with bounded error.
We extensively compare the proposed NeRF-VINS against the state-of-the-art
methods that use prior map information, which is shown to achieve superior
performance. We also demonstrate the proposed method is able to perform
real-time estimation at 15 Hz, on a resource-constrained Jetson AGX Orin
embedded platform with impressive accuracy.Comment: 6 pages, 7 figure
Parkin Modulates ERRα/eNOS Signaling Pathway in Endothelial Cells
Background/Aims: Although a number of reports documented the important role of parkin in mitophagy, emerging evidence also indicated additional functions of parkin besides mitophagy. The present study was undertaken to investigate the role of parkin in the regulation of ERRα/eNOS pathway in endothelial cells (ECs). Methods: Mouse aortic endothelial cells (MAECs) and cardiac muscle HL-1 cells were transfected with parkin plasmid or siRNA. ERRα inhibitor XCT-790, autophagy inhibitor 3-MA and Bafilomycin A1, and caspase inhibitor Z-VAD-FMK were used to block autophagy or apoptosis. Western blotting was performed to examine the protein levels. Flow cytometry was applied to determine the cell apoptosis and ROS production. Mitochondrial membrane potential was measured using JC-1 and TMRM. Immunoprecipitation was performed to confirm the parkin effect on ERRα ubiquitination. Results: Overexpression of parkin resulted in a significant reduction of total-eNOS and p-eNOS in parallel with the downregulation of ERRα (a regulator of eNOS) protein and the enhancement of ERRα ubiquitination. To test the role of ERRα in regulating eNOS in this experimental setting, we treated ECs with ERRα inhibitor and found a decrement of total-eNOS and p-eNOS. On the contrary, overexpression of ERRα increased the levels of total-eNOS and p-eNOS. Meanwhile, parkin overexpression induced mitochondrial dysfunction and cell apoptosis in both ECs and HL-1 cells. Finally, we confirmed that the parkin effect on the regulation of eNOS was independent of the autophagy and apoptosis. Conclusion: These findings suggested that parkin overexpression downregulated eNOS possibly through the ubiquitination of ERRα in endothelial cells
The Pneumococcal Iron Uptake Protein a (PiuA) Specifically Recognizes Tetradentate FeIIIbis- and Mono-Catechol Complexes
Streptococcus pneumoniae (Spn) is an important Gram-positive human pathogen that causes millions of infections worldwide with an increasing occurrence of antibiotic resistance. Fe acquisition is a crucial virulence determinant in Spn; further, Spn relies on exogenous FeIII-siderophore scavenging to meet nutritional Fe needs. Recent studies suggest that the human catecholamine stress hormone, norepinephrine (NE), facilitates Fe acquisition in Spn under conditions of transferrin-mediated Fe starvation. Here we show that the solute binding lipoprotein PiuA from the piu Fe acquisition ABC transporter PiuBCDA, previously described as an Fe-hemin binding protein, binds tetradentate catechol FeIII complexes, including NE and the hydrolysis products of enterobactin. Two protein-derived ligands (H238, Y300) create a coordinately-saturated FeIII complex, which parallel recent studies in the Gram-negative intestinal pathogen Campylobacter jejuni. Our in vitro studies using NMR spectroscopy and 54Fe LC-ICP-MS confirm the FeIII can move from transferrin to apo-PiuA in a NE-dependent manner. Structural analysis of PiuA FeIII-bis-catechol and GaIII-bis-catechol and GaIII-(NE)2 complexes by NMR spectroscopy reveals only localized structural perturbations in PiuA upon ligand binding, largely consistent with recent descriptions of other solute binding proteins of type II ABC transporters. We speculate that tetradentate FeIII complexes formed by mono- and bis-catechol species are important Fe sources in Gram-positive human pathogens, since PiuA functions in the same way as SstD from Staphylococcus aureus
Exploring the Antibacterial Activity and Cellular Fates of EnterobactinâDrug Conjugates That Target Gram-Negative Bacterial Pathogens
ConspectusSiderophores are secondary metabolites
utilized by bacteria to
acquire iron (Fe), an essential transition metal nutrient. Fe levels
in the host environment are tightly regulated and can be further restricted
to starve invading bacterial pathogens in a host-defense process known
as nutritional immunity. To survive and colonize the Fe-limited host
environment, bacteria produce siderophores and express cognate siderophore
transport machinery. These active transport pathways present an opportunity
for selective and efficient drug delivery into bacterial cells, motivating
decades of research on synthetic siderophoreâantibiotic conjugates
(SACs) as a Trojan-horse strategy for the development of targeted
antibiotics.Enterobactin (Ent) is a triscatecholate siderophore
produced and
utilized by many Gram-negative bacteria, including all Escherichia
coli and Salmonella species. Within these
species, pathogenic strains cause a variety of human diseases including
urinary tract infections, gastroenteritis, and sepsis. Infections
caused by these Gram-negative pathogens can be difficult to treat
because of the impermeability of the outer membrane (OM). This impermeability
can be overcome by utilizing siderophores as drug delivery vectors
for targeting Gram-negative pathogens. Ent is a promising delivery
vector because it undergoes active transport across the OM mediated
by the Ent uptake machinery after scavenging Fe(III) from the extracellular
environment. Despite the well-elucidated chemistry and biology of
Ent, its use for SAC development was hampered by the lack of an appropriate
functional group for cargo attachment. Our laboratory addressed this
need by designing and synthesizing monofunctionalized Ent scaffolds.
Over the past decade, we have used these scaffolds to explore Ent-based
SACs with a variety of drug warheads, including ÎČ-lactam and
fluoroquinolone antibiotics, and Pt(IV) prodrugs. Investigations of
the antibacterial activities of these conjugates and their cellular
fates have informed our design principles and revealed approaches
to achieving enhanced antibacterial potency and pathogen-targeted
activity. Collectively, our studies of Entâdrug conjugates
have provided discoveries, understanding, and invaluable insights
for future design and evaluation of SACs.In this Account, we
present the story of our work on Entâdrug
conjugates that began about ten years ago with the development of
monofunctionalized Ent scaffolds and the design and synthesis of various
conjugates based on these scaffolds. We describe the antibacterial
activity profiles and uptake pathways of Entâdrug conjugates
harboring traditional antibiotics and repurposed platinum anticancer
agents as well as studies that address cellular targets and fates.
Finally, we discuss other applications of monofunctionalized Ent scaffolds,
including a siderophore-based immunization strategy. We intend for
this Account to inspire further investigations into the fundamental
understanding and translational applications of siderophores and siderophoreâdrug
conjugates
Adjusting the Morphology and Properties of SiC Nanowires by Catalyst Control
We report on the growth of SiC nanowires on a single crystal Si substrate by pyrolysis of polycarbosilane and using two catalyst (Al2O3 and Ni) films with different thickness (2, 4, and 6 nm). The catalyst films were deposited on the Si substrate, and the SiC nanowires were grown according to two mechanisms, i.e., the oxide-assisted growth mechanism and vapor- liquid-solid mechanism. As a result, pearl-chain-like SiC nanowires and straight SiC nanowires were obtained. The prepared nanowires exhibited excellent photoluminescence properties, emission spectra displaying two emission peaks at 395 and 465 nm, and have good thermal stability below 1000 °C. The experimental results revealed the importance of the catalyst in controlling the morphology and properties of SiC nanowires
Photochromism, UV-Vis, Vibrational and Fluorescence Spectroscopy of Differently Colored Hackmanite
Because of the rich fluorescent color and unique photochromic properties, hackmanite has attracted many mineralogists. In this paper, the basic gemmological characteristics and photochromic and fluorescence mechanisms of four different colors of hackmanite are further investigated through the study of their structural, compositional, and spectroscopic features. The results show the change in the color of hackmanite in photochromism is caused by the joint action of the F-center and the oxygen hole centers. The change in the UV-Vis spectra may be caused by the superposition of two peaks. Under 365 nm UV excitation, the peak of fluorescence spectra of 662 nm is related to the 2âgâ2âu transition of S2â, the blue emission at 441 nm is caused by the 3P0.1â1S0 transition of s2 ions (Pb2+, Tl+, Sn2+ Sb2+), and at 541 nm is caused by the Mn2+ center. The results are helpful in deepening the understanding of photochromism, fluorescence mechanism, and its structure, expanding the application of hackmanite
Investigation of SiderophoreâPlatinum(IV) Conjugates Reveals Differing Antibacterial Activity and DNA Damage Depending on the Platinum Cargo
The growing threat of bacterial infections coupled with
the dwindling
arsenal of effective antibiotics has heightened the urgency for innovative
strategies to combat bacterial pathogens, particularly Gram-negative
strains, which pose a significant challenge due to their outer membrane
permeability barrier. In this study, we repurpose clinically approved
anticancer agents as targeted antibacterials. We report two new siderophoreâplatinum(IV)
conjugates, both of which consist of an oxaliplatin-based Pt(IV) prodrug
(oxPt(IV)) conjugated to enterobactin (Ent), a triscatecholate siderophore
employed by Enterobacteriaceae for iron acquisition. We demonstrate
that l/d-Ent-oxPt(IV) (l/d-EOP)
are selectively delivered into the Escherichia coli cytoplasm, achieving targeted antibacterial activity,
causing filamentous morphology, and leading to enhanced Pt uptake
by bacterial cells but reduced Pt uptake by human cells. d-EOP exhibits enhanced potency compared to oxaliplatin and l-EOP, primarily attributed to the intrinsic antibacterial activity
of its non-native siderophore moiety. To further elucidate the antibacterial
activity of EntâPt(IV) conjugates, we probed DNA damage caused
by l/d-EOP and the previously reported cisplatin-based
conjugates l/d-Ent-Pt(IV) (l/d-EP). A comparative analysis of these four conjugates reveals a correlation
between antibacterial activity and the ability to induce DNA damage.
This work expands the scope of Pt cargos targeted to the cytoplasm
of Gram-negative bacteria via Ent conjugation, provides insight into
the cellular consequences of EntâPt(IV) conjugates in E. coli, and furthers our understanding of the potential
of Pt-based therapeutics for antibacterial applications
Sb-Containing Metal Oxide Catalysts for the Selective Catalytic Reduction of NOx with NH3
Sb-containing catalysts (SbZrOx (SbZr), SbCeOx (SbCe), SbCeZrOx (SbCeZr)) were prepared by citric acid method and investigated for the selective catalytic reduction (SCR) of NOx with NH3 (NH3-SCR). SbCeZr outperformed SbZr and SbCe and exhibited the highest activity with 80% NO conversion in the temperature window of 202–422 °C. Meanwhile, it also had good thermal stability and resistance against H2O and SO2. Various characterization methods, such as XRD, XPS, H2-TPR, NH3-TPD, and in situ diffuse reflectance infrared Fourier transform (DRIFT), were applied to understand their different behavior in NOx removal. The presence of Sb in the metal oxides led to the difference in acid distribution and redox property, which closely related with the NH3 adsorption and NO oxidation. Brønsted acid and Lewis acid were evenly distributed on SbCe, while Brønsted acid dominated on SbCeZr. Compared with Brønsted acid, Lewis acid was slightly active in NH3-SCR. The competition between NH3 adsorption and NO oxidation was dependent on SbOx and metal oxides, which were found on SbCe while not on SbCeZr
Role of Low-Molecular-Mass Penicillin-Binding Proteins, NagZ and AmpR in AmpC ÎČ-lactamase Regulation of Yersinia enterocolitica
Yersinia enterocolitica encodes a chromosomal AmpC ÎČ-lactamase under the regulation of the classical ampR-ampC system. To obtain a further understanding to the role of low-molecular-mass penicillin-binding proteins (LMM PBPs) including PBP4, PBP5, PBP6, and PBP7, as well as NagZ and AmpR in ampC regulation of Y. enterocolitica, series of single/multiple mutant strains were systematically constructed and the ampC expression levels were determined by luxCDABE reporter system, reverse transcription-PCR (RT-PCR) and ÎČ-lactamase activity test. Sequential deletion of PBP5 and other LMM PBPs result in a continuously growing of ampC expression level, the ÎČ-lactamse activity of quadruple deletion strain YEÎ4Î5Î6Î7 (pbp4, pbp5, pbp6, and pbp7 inactivated) is approached to the YEÎD123 (ampD1, ampD2, and ampD3 inactivated). Deletion of nagZ gene caused two completely different results in YEÎD123 and YEÎ4Î5Î6Î7, NagZ is indispensable for YEÎ4Î5Î6Î7 ampC derepression phenotype but dispensable for YEÎD123. AmpR is essential for ampC hyperproduction in these two types of strains, inactivation of AmpR notable reduced the ampC expression level in both YEÎD123 and YEÎ4Î5Î6Î7