1,359 research outputs found
Structural synthetic biology strategy for the design of a new metabolic pathway
To date, notable successes have been made in producing valuable chemicals and fuels from renewable resources by simply modifying and optimizing the metabolic pathways in microorganisms. However, to design a more efficient and desirable pathway with high efficiency from ubiquitously existing multi-branched and multi-level regulated ones, a new approach is needed other than conventional systematic analysis of every bottlenecks embedded in the biosynthetic pathways. Here, we present a strategy combining rational enzyme design and synthetic biology to construct a new metabolic pathway which evades from the highly regulated nature. As a proof-of-concept, we implemented our approach to the design of a new L-methionine biosynthetic pathway. To this end, structure of the MetZ enzyme, which is a key to the construction of new biosynthetic pathway in Corynebacterium glutamicum, was modelled, and its substrate specificity was rationally altered toward a substrate required for redirecting the metabolic flux in the pathway. Furthermore, we used mutational approach to relieve feedback inhibition of other enzymes which regulate the metabolic flux in the methionine biosynthetic pathway. As a result, the L-methionine level reached a gram scale in flask culture by recombinant Corynebacterium glutamicum with the methionine biosynthetic pathway. We demonstrate that the “structural synthetic biology” strategy can boost our ability to generate a more efficient metabolic pathway for the production of valuable chemicals
EFFECTS OF MO, CR, AND V ADDITIONS ON TENSILE AND CHARPY IMPACT PROPERTIES OF API X80 PIPELINE STEELS
In this study, four API X80 pipeline steels were fabricated by varying Mo, Cr, and V additions, and their microstructures and crystallographic orientations were analyzed to investigate the effects of their alloying compositions on tensile properties and Charpy impact properties. Because additions of Mo and V promoted the formation of fine acicular ferrite (AF) and granular bainite (GB) while prohibiting the formation of coarse GB, they increased the strength and upper-shelf energy (USE) and decreased the energy transition temperature (ETT). The addition of Cr promoted the formation of coarse GB and hard secondary phases, thereby leading to an increased effective grain size, ETT, and strength, and a decreased USE. The addition of V resulted in a higher strength, a higher USE, a smaller effective grain size, and a lower ETT, because it promoted the formation of fine and homogeneous of AF and GB. The steel that contains 0.3 wt pct Mo and 0.06 wt pct V without Cr had the highest USE and the lowest ETT, because its microstructure was composed of fine AF and GB while its maintained excellent tensile properties.X1126sciescopu
Automatic Three-Dimensional Cephalometric Annotation System Using Three-Dimensional Convolutional Neural Networks
Background: Three-dimensional (3D) cephalometric analysis using computerized
tomography data has been rapidly adopted for dysmorphosis and anthropometry.
Several different approaches to automatic 3D annotation have been proposed to
overcome the limitations of traditional cephalometry. The purpose of this study
was to evaluate the accuracy of our newly-developed system using a deep
learning algorithm for automatic 3D cephalometric annotation. Methods: To
overcome current technical limitations, some measures were developed to
directly annotate 3D human skull data. Our deep learning-based model system
mainly consisted of a 3D convolutional neural network and image data
resampling. Results: The discrepancies between the referenced and predicted
coordinate values in three axes and in 3D distance were calculated to evaluate
system accuracy. Our new model system yielded prediction errors of 3.26, 3.18,
and 4.81 mm (for three axes) and 7.61 mm (for 3D). Moreover, there was no
difference among the landmarks of the three groups, including the midsagittal
plane, horizontal plane, and mandible (p>0.05). Conclusion: A new 3D
convolutional neural network-based automatic annotation system for 3D
cephalometry was developed. The strategies used to implement the system were
detailed and measurement results were evaluated for accuracy. Further
development of this system is planned for full clinical application of
automatic 3D cephalometric annotation
Seismic response of beam-column joints rehabilitated with FRP sheets and buckling restrained braces
An experimental test was performed to evaluate the seismic resistance of reinforced concrete beam-column joints rehabilitated with FRP sheets and Buckling Restrained Braces (BRBs). Six beam-column joints were rehabilitated and tested. The test results were compared in terms of hysteresis loops, stiffness degradation, energy dissipation and ductility. The comparison result showed that wrapping FRP sheets can contribute to increase the effect of confinement and to delay crack development in the joints. Also retrofitting buckling restrained braces (BRBs) can improve the stiffness and energy dissipation capacity. Both FRP sheets and BRBs can effectively improve the strength, stiffness and ductility
Performance of a lead rubber damper under cyclic shear loading and its applicability to a full-scale structure
In this paper, we investigate the performance of a new lead rubber damper (LRD) and its applicability to a full-scale structure. This device is more advanced than existing lead-rubber based isolation devices. In contrast to the existing devices, multiple lead cores are installed in the LRD in order to enhance the performance of the laminated rubber and lead. It is able to perform effectively under the application of shear force. An experiment was performed to investigate its dependency on the level of shear strain and frequency. The applicability of this new device to a full-scale structure is also examined by performing a vibration test on a five floor modal-test tower
Two distinct red giant branch populations in the globular cluster NGC 2419 as tracers of a merger event in the Milky Way
Recent spectroscopic observations of the outer halo globular cluster (GC) NGC
2419 show that it is unique among GCs, in terms of chemical abundance patterns,
and some suggest that it was originated in the nucleus of a dwarf galaxy. Here
we show, from the Subaru narrow-band photometry employing a calcium filter,
that the red giant-branch (RGB) of this GC is split into two distinct
subpopulations. Comparison with spectroscopy has confirmed that the redder RGB
stars in the [=(Ca] index are enhanced in [Ca/H] by 0.2
dex compared to the bluer RGB stars. Our population model further indicates
that the calcium-rich second generation stars are also enhanced in helium
abundance by a large amount (Y = 0.19). Our photometry, together with
the results for other massive GCs (e.g., Cen, M22, and NGC 1851),
suggests that the discrete distribution of RGB stars in the index might be
a universal characteristic of this growing group of peculiar GCs. The planned
narrow-band calcium photometry for the Local Group dwarf galaxies would help to
establish an empirical connection between these GCs and the primordial building
blocks in the hierarchical merging paradigm of galaxy formation.Comment: 4 pages, 4 figures, 1 table, accepted for the publication in ApJ
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