Cu-TiB2 nanocomposite powders were obtained by means of a combination of mechanical treatment and combustion reaction. Spark plasma sintering (SPS) was used to inhibit grain growth and thereby obtain ...fully dense Cu-TiB2 sintered bodies with a nanocomposite structure. The phases of the synthesised product were identified using XRD and results showed only Cu and TiB2, with no other phases existing. The particle size of SHS powder was < 250 nm. Mechanical and electrical properties were investigated after SPS at 650 C for 30 min, the electrical conductivity decreased from 75 to 54% International Annealed Copper Standard (IACS) with the TiB2 content increasing from 2.5 to 10 wt%, while the hardness increased from 56 to 97 H(R)B. In addition, the tensile strength and wear resistance of the composites increased as the TiB2 content increased. 22 refs.
We have measured gluon splitting into bottom quarks,
g→b
b
̄
, in hadronic
Z
0 decays collected by SLD between 1996 and 1998. The analysis was performed by looking for secondary bottom production in ...4-jet events of any primary flavor. 4-jet events were identified, and in each event a topological vertex-mass technique was applied to the two jets closest in angle in order to identify them as
b or
b
̄
jets. The upgraded CCD-based vertex detector gives very high
B-tagging efficiency, especially for
B hadrons with the low energies typical of this process. We measured the rate of
g→b
b
̄
production per hadronic event,
g
b
b
̄
, to be (2.44±0.59(stat.)±0.34(syst.))×10
−3.
This paper presents an overview of the theories and computer implementation aspects of phase field models (PFM) of fracture. The advantage of PFM over discontinuous approaches to fracture is that PFM ...can elegantly simulate complicated fracture processes including fracture initiation, propagation, coalescence, and branching by using only a scalar field, the phase field. In addition, fracture is a natural outcome of the simulation and obtained through the solution of an additional differential equation related to the phase field. No extra fracture criteria are needed and an explicit representation of a crack surface as well as complex track crack procedures are avoided in PFM for fracture, which in turn dramatically facilitates the implementation. The PFM is thermodynamically consistent and can be easily extended to multi-physics problem by ‘changing’ the energy functional accordingly. Besides an overview of different PFMs, we also present comparative numerical benchmark examples to show the capability of PFMs.
•Development in phase field models and the computer implementation is reviewed.•The theories on phase field modeling are systematically summarized.•Representative numerical examples are presented for different fracture problems.
Since 1997, outbreaks of highly pathogenic (HP) H5N1 and circulation of H9N2 viruses among domestic poultry in Asia have posed a threat to public health. To better understand the extent of ...transmission of avian influenza viruses (AIV) to humans in Asia, we conducted a cross-sectional virologic study in live bird markets (LBM) in Hanoi, Vietnam, in October 2001. Specimens from 189 birds and 18 environmental samples were collected at 10 LBM. Four influenza A viruses of the H4N6 (n = 1), H5N2 (n = 1), and H9N3 (n = 2) subtypes were isolated from healthy ducks for an isolation frequency of over 30% from this species. Two H5N1 viruses were isolated from healthy geese. The hemagglutinin (HA) genes of these H5N1 viruses possessed multiple basic amino acid motifs at the cleavage site, were HP for experimentally infected chickens, and were thus characterized as HP AIV. These HA genes shared high amino acid identities with genes of other H5N1 viruses isolated in Asia during this period, but they were genetically distinct from those of H5N1 viruses isolated from poultry and humans in Vietnam during the early 2004 outbreaks. These viruses were not highly virulent for experimentally infected ducks, mice, or ferrets. These results establish that HP H5N1 viruses with properties similar to viruses isolated in Hong Kong and mainland China circulated in Vietnam as early as 2001, suggest a common source for H5N1 viruses circulating in these Asian countries, and provide a framework to better understand the recent widespread emergence of HP H5N1 viruses in Asia.
MYC is a major oncogenic driver of multiple myeloma (MM) and yet almost no therapeutic agents exist that target MYC in MM. Here we report that the let-7 biogenesis inhibitor LIN28B correlates with ...MYC expression in MM and is associated with adverse outcome. We also demonstrate that the LIN28B/let-7 axis modulates the expression of MYC, itself a let-7 target. Further, perturbation of the axis regulates the proliferation of MM cells in vivo in a xenograft tumor model. RNA-sequencing and gene set enrichment analyses of CRISPR-engineered cells further suggest that the LIN28/let-7 axis regulates MYC and cell cycle pathways in MM. We provide proof of principle for therapeutic regulation of MYC through let-7 with an LNA-GapmeR (locked nucleic acid-GapmeR) containing a let-7b mimic in vivo, demonstrating that high levels of let-7 expression repress tumor growth by regulating MYC expression. These findings reveal a novel mechanism of therapeutic targeting of MYC through the LIN28B/let-7 axis in MM that may impact other MYC-dependent cancers as well.
Recent studies have developed varied delivery systems incorporating natural compounds to improve the limitations of plant extracts for clinical use while enabling their controlled release at ...treatment sites. For the first time, ethanolic limeberry extract (Triphasia trifolia) has been successfully encapsulated in thermo-sensitive chitosan hydrogels by a facile in situ loading. The extract-incorporated chitosan hydrogels have a pH value of nearly 7.00, gelation temperatures in the range of 37–38 °C, and exhibit an open-cell porous structure, thus allowing them to absorb and retain 756 % of their mass in water. The in vitro extract release from the hydrogels is driven by both temperature and pH, resulting in more than 70 % of the initial extract being released within the first 24 h. Although the release half-life of hydrogels at pH 7.4 is longer, their release capacity is higher than that at pH 6.5. Upon a 2 °C increase in temperature, the time to release 50 % initial extract is sharply reduced by 20–40 %. The release kinetics from the hydrogels mathematically demonstrated that diffusion is a prominent driving force over chitosan relaxation. Consequently, the developed hydrogels encapsulating the limeberry extract show their heat and pH sensitivity in controlled release for treating chronic wounds.
Social distancing plays a pivotal role in preventing the spread of viral diseases illnesses such as COVID-19. By minimizing the close physical contact among people, we can reduce the chances of ...catching the virus and spreading it across the community. This two-part paper aims to provide a comprehensive survey on how emerging technologies, e.g., wireless and networking, artificial intelligence (AI) can enable, encourage, and even enforce social distancing practice. In this Part I, we provide a comprehensive background of social distancing including basic concepts, measurements, models, and propose various practical social distancing scenarios. We then discuss enabling wireless technologies which are especially effect- in social distancing, e.g., symptom prediction, detection and monitoring quarantined people, and contact tracing. The companion paper Part II surveys other emerging and related technologies, such as machine learning, computer vision, thermal, ultrasound, etc., and discusses open issues and challenges (e.g., privacy-preserving, scheduling, and incentive mechanisms) in implementing social distancing in practice.
In this study, the explosive behavior of syngas/air mixtures was investigated numerically in a 3-D cylindrical geometric model, using ANSYS Fluent. A chamber with the same dimensions as the geometry ...in the simulation was used to investigate the explosion process experimentally. The outcome was in good agreement with experimental results for most equivalence ratios at atmospheric pressure, while discrepancies were observed for very rich mixtures (ϕ > 2.0) and at elevated pressure conditions. Both the experimental and simulated results showed that for syngas/air mixture, the maximum explosion pressure increased from lean (ϕ = 0.8) to an equivalence ratio of 1.2, then decreased significantly with richer mixtures, indicating that maximum explosion pressure occurred at the equivalence ratio of 1.2, while explosion time was shortest at an equivalence ratio of 1.6. Increasing H2 content in the fuel blends significantly raised laminar burning velocity and shortened the explosion time, thereby increasing the maximum rate of pressure rise and deflagration index. Normalized peak pressure, the maximum rate of pressure rise and the deflagration index were sensitive to the initial pressure of the mixture, showing that they increased significantly with increased initial pressure.
Display omitted
•Explosive behavior of syngas/air was investigated numerically and experimentally.•The maximum explosion pressure occurred at an equivalence ratio of 1.2.•The explosion time was shortest at an equivalence ratio of 1.6.•(dP/dt)max and KG increased with increased H2 content in the fuel blends.•(dP/dt)max and KG increased significantly with increased initial pressure.
PDF
