254 research outputs found
Enhanced production of dimethyl phthalate-degrading strain Bacillus sp. QD14 by optimizing fermentation medium
Background: Integrated statistical experimental designs were applied to
optimize the medium constituents for the production of a dimethyl
phthalate (DMP)-degrading strain Bacillus sp. QD14 in shake-flask
cultures. A Plackett\u2013Burman design (PBD) was applied to screen
for significant factors, followed by the Steepest Ascent Method (SAM)
to find the nearest region of maximum response. A Box\u2013Behnken
design (BBD) of the Response Surface Methodology (RSM) was conducted to
optimize the final levels of the medium components. Results: After the
regression equation and response surface contour plots were analyzed,
the concentrations of glucose, corn meal and NaCl were found to
significantly influence the biomass of DMP-degrading bacteria. A
combination of 22.88 g/L of glucose, 11.74 g/L of corn meal, and 10.34
g/L of NaCl was optimum for maximum biomass production of Bacillus sp.
QD14. A 57.11% enhancement of the biomass production was gained after
optimization in shake-flask cultivation. The biomass production of
Bacillus sp. QD14 reached 9.13 \ub1 0.29
7 108 CFU/mL, which was
an excellent match for the predicted value, and the mean value of the
match degree was as high as 99.30%. Conclusion: In this work, the key
factors affected by the fermentation of DMP-degrading strain Bacillus
sp. QD14 were optimized by PBD, SAM and BBD (RSM); the yield was
increased by 57,11% in the conditions in our study. We propose that the
conditions optimized in the study can be applied to the fermentation
for commercialization production
Towards Privacy-Preserving and Efficient Attribute-Based Multi-Keyword Search
Searchable encryption can provide secure search over encrypted cloud-based data without infringing data confidentiality and data searcher privacy. In this work, we focus on a secure search service providing fine-grained and expressive search functionality, which can be seen as a general extension of searchable encryption and called attribute-based multi-keyword search (ABMKS). In most of the existing ABMKS schemes, the ciphertext size of keyword index (encrypted index) grows linearly with the number of the keyword associated with a file, so that the computation and communication complexity of keyword index is limited to O(m) , where m is the number of the keyword. To address this shortage, we propose the first ABMKS scheme through utilizing keyword dictionary tree and the subset cover, in such a way that the ciphertext size of keyword index is not dependent on the number of underlying keyword in a file. In our design, the complexity of computation and the complexity of the keyword index are at most O ( 2· log (n/2) ) for the worst case, but O(1) for the best case, where n is the number of keyword in a keyword dictionary. We also present the security and the performance analysis to demonstrate that our scheme is both secure and efficient in practice
Pressure-induced non-monotonic crossover of steady relaxation dynamics in a metallic glass
Relaxation dynamics, as a key to understand glass formation and glassy
properties, remains an elusive and challenging issue in condensed matter
physics. In this work, in situ high-pressure synchrotron high-energy x-ray
photon correlation spectroscopy has been developed to probe the atomic-scale
relaxation dynamics of a cerium-based metallic glass during compression.
Although the sample density continuously increases, the collective atomic
motion initially slows down as generally expected and then counter-intuitively
accelerates with further compression (density increase), showing an unusual
non-monotonic pressure-induced steady relaxation dynamics crossover at ~3 GPa.
Furthermore, by combining in situ high-pressure synchrotron x-ray diffraction,
the relaxation dynamics anomaly is evidenced to closely correlate with the
dramatic changes in local atomic structures during compression, rather than
monotonically scaling with either sample density or overall stress level. These
findings could provide new insight into relaxation dynamics and their
relationship with local atomic structures of glasses.Comment: 21 pages, 4 figure
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