Three dimensional (3D) bioprinting technology enables the freeform fabrication of complex constructs from various hydrogels and is receiving increasing attention in tissue engineering. The objective ...of this study is to develop a novel self-supporting direct hydrogel printing approach to extrude complex 3D hydrogel composite structures in air without the help of a support bath. Laponite, a member of the smectite mineral family, is investigated to serve as an internal scaffold material for the direct printing of hydrogel composite structures in air. In the proposed printing approach, due to its yield-stress property, Laponite nanoclay can be easily extruded through a nozzle as a liquid and self-supported after extrusion as a solid. Its unique crystal structure with positive and negative charges enables it to be mixed with many chemically and physically cross-linked hydrogels, which makes it an ideal internal scaffold material for the fabrication of various hydrogel structures. By mixing Laponite nanoclay with various hydrogel precursors, the hydrogel composites retain their self-supporting capacity and can be printed into 3D structures directly in air and retain their shapes before cross-linking. Then, the whole structures are solidified in situ by applying suitable cross-linking stimuli. The addition of Laponite nanoclay can effectively improve the mechanical and biological properties of hydrogel composites. Specifically, the addition of Laponite nanoclay results in a significant increase in the Young’s modulus of each hydrogel–Laponite composite: 1.9-fold increase for the poly(ethylene glycol) diacrylate (PEGDA)–Laponite composite, 7.4-fold increase for the alginate–Laponite composite, and 3.3-fold increase for the gelatin–Laponite composite.
Freeform three-dimensional (3D) printing of functional structures from liquid hydrophobic build materials is of great significance and widely used in various fields such as soft robotics and ...microfluidics. In particular, a yield-stress support bath-enabled 3D-printing methodology has been emerging to fabricate complex 3D structures. Unfortunately, the reported support bath materials are either hydrophobic or not versatile enough for the printing of a wide range of hydrophobic materials. The objective of this study is to propose a fumed silica nanoparticle-based yield-stress suspension as a hydrophobic support bath to enable 3D extrusion printing of various hydrophobic ink materials in a printing-then-solidification fashion. Hydrophobic ink is freeform-deposited in a hydrophobic fumed silica-mineral oil suspension and maintains its shape during printing; it is not cured until the whole structure is complete. Various hydrophobic inks including poly(dimethylsiloxane) (PDMS), SU-8 resin, and epoxy-based conductive ink are printed into complex 3D structures in the fumed silica-mineral oil bath and then cured using relevant cross-linking mechanisms, even at a temperature as high as 90 °C, to prove the feasibility and versatility of the proposed printing approach. In addition, the deposited feature can easily reach a much better resolution such as 30 μm for PDMS filaments due to the negligible interfacial tension effect.
Abstract
The Messenger Interface Monte Carlo Mappings V (M
3
) is a photoionization code adopting the fully self-consistent Monte Carlo radiative transfer (MCRT) technique, which presents a major ...advance over previous photoionization models with simple geometries. M
3
is designed for modeling nebulae in arbitrary three-dimensional geometries. In this paper, we describe the MCRT technique and the microphysics implemented in M
3
, including photoionization, collisional ionization, free–free and free–bound recombination, and two-photon radiation. We put M
3
through the Lexington/Meudon benchmarks to test the reliability of the new code. We apply M
3
to three H
ii
region models with fiducial geometries, demonstrating that M
3
is capable of dealing with nebulae with complex geometries. M
3
is a promising tool for understanding emission-line behavior in the era of SDSS-V/LVM and James Webb Space Telescope, which will provide high-quality data of spatially resolved nearby H
ii
regions and highly turbulent local and high-redshift H
ii
regions.
A simple low-cost method was used to measure the thermal diffusivity of nine different types of foods: potato, sweet potato, pumpkin, taro, radish, eggplant, lemon, tomato, and onion. We cut the ...foods into spherical shapes, inserted thermocouple sensors into their centers, and immersed them in boiling water. Fitting the time dependence of the center temperature to a heat-conduction model yielded a value for the thermal diffusivity with good consistency between spheres of different radii. This method can be generalized to determine thermal diffusivity of a wide variety of samples.
Abstract
Photoionization models frequently assume constant temperature or density within H
ii
regions. We investigate this assumption by measuring the detailed temperature and density structures of ...four H
ii
regions in the Large Magellanic Cloud and the Small Magellanic Cloud, using integral-field spectroscopic data from the Wide-Field Spectrograph on the ANU 2.3 m telescope. We analyze the distribution of emission lines of low-ionization, intermediate-ionization, and high-ionization species. We present the complex electron temperature and density structures within H
ii
regions. All four nebulae present a negative gradient in the electron density profile. Both positive and negative temperature gradients are observed in the nebulae. We create a series of nebula models with constant interstellar medium (ISM) pressure and varying temperature and density distributions. A comparison of the line ratios between our H
ii
regions and models suggests that none of the simple nebula models can reproduce the observed temperature and density structures. Comparison between the models and the data suggests that the ISM pressure of nebulae in the LMC and SMC is between log(
P
/
k
) = 6 and 7.5. Complex internal structures of the nebulae highlight the importance of future Monte Carlo photoionization codes for accurate nebula modeling, which include a comprehensive consideration of arbitrary geometries of H
ii
regions.
Alzheimer’s disease (AD) is chronic neurodegenerative dementia representing the most common cause of dementia in the elderly population. It is a major source of morbidity, mortality, and healthcare ...expenditure worldwide. Although the molecular and cellular properties related to AD have been demonstrated decades before the onset of clinical symptoms, AD’s pathogenesis is still unknown as a combination of risk factors causes it. Today, pathogenesis theories focused on senile plaques (SP) formed by the extracellular accumulation and deposition of Aβ peptides and neurofibrillary tangles (NFTs), which are composed of the hyperphosphorylated tau protein. Furthermore, growing evidence points out that toxic Aβ plays a primary causal role in the induction and transmission of pathology and neuronal dysfunction and loss. Therefore, Aβ is crucial to the development of AD and is a noteworthy issue in AD research. This review shows the formation of Aβ and the differences of cytotoxicity of its various isoforms and aggregation states. It also summarizes the mechanisms by which Aβ induce AD through its neurotoxicity and state how these mechanisms interact and reinforce each other.
Back in 2008, Panofsky gave an empirical formula, T=11.5W2/3, for turkey baking time, T, in hours vs turkey weight, W, in pounds, the so-called Panofsky formula or Panofsky constant. Compared to the ...previously existed recipes that are based on the simple linear relationship between turkey weight and baking time, the Panofsky formula provides a more accurate estimate for the baking time. For instance, a general guideline of 13–20 min/lb was widely recommended in all previous turkey baking recipes. In this work, we conduct a comprehensive study of the turkey baking process that leads to a mathematical derivation of the Panofsky formula under some approximations. We also generalize the Panofsky formula to define a general Panofsky formula, T=1PW2/3, where P is defined as the Panofsky constant. Under spherical approximations, we then apply an accurate physical solution of the heat transfer equation and use the rigorous solution with numerical methods to study the generalized Panofsky formula and the Panofsky constant. We found that the generalized Panofsky formula can be perfectly applied to all turkey baking scenarios for baking time calculations. Furthermore, we did a careful analysis of the Panofsky constant, which equals 1.5 in the original Panofsky formula. The dependency of the new Panofsky constant on thermal properties of the turkeys and other initial parameters of baking, e.g., initial and final center temperature of the turkeys, oven temperature, thermal conductivity, specific heat, and turkey’s density, was carefully analyzed and mapped out. The Panofsky constant, P, could vary from 1.1 to 1.9 depending on these thermal parameters.
Abstract
The origin of the low-ionization nuclear emission-line region (LINER) prevalent in local galaxies and its relationship with supermassive black holes have been debated for decades. We perform ...a comprehensive evaluation of traditional photoionization models against the circumnuclear ionized gas in M81, for which recent CAHA/PPAK integral-field spectroscopic observations reveal a LINER characteristic out to a galactocentric radius of ∼1 kpc. Constructed with the photoionization code
cloudy
, the models have the novel aspect of their primary parameters being well constrained by extensive observations of a prototypical low-luminosity active galactic nucleus (LLAGN) and an old stellar bulge in M81. Additionally, these models incorporate a reasonably broad range of uncertain nebular properties. It is found that the integrated photoionization by the LLAGN and hot, low-mass stars distributed in the bulge can roughly reproduce the observed radial intensity distributions of the H
α
, H
β,
and N
ii
lines, with the bulge stars dominating the ionizing flux at radii ≳200 pc. However, the models generally fail to reproduce a similarly declining profile of the O
iii
line or an accordingly flat profile of the O
iii
/H
β
ratio. This clearly points to a deficiency of ionizing photons in the outer regions despite an extended photoionization source. The discrepancy might be alleviated if much of the observed O
iii
line arose from a bulge-filling, low-density gas surrounding a denser, H
α
-emitting disk, or by a higher AGN luminosity in the recent past. The case of M81 has important implications for the ionization mechanism of LINERs and low-ionization emission-line regions in general.
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Since December 2019, coronavirus disease (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has become a great challenge to the world's public health ...system. Nosocomial infections have occurred frequently in medical institutions worldwide during this pandemic. Thus, there is an urgent need to construct an effective surveillance and early warning system for pathogen exposure and infection to prevent nosocomial infections in negative-pressure wards. In this study, visualization and construction of an infection risk assessment of SARS-CoV-2 through aerosol and surface transmission in a negative-pressure ward were performed to describe the distribution regularity and infection risk of SARS-CoV-2, the critical factors of infection, the air changes per hour (ACHs) and the viral variation that affect infection risk. The SARS-CoV-2 distribution data from this model were verified by field test data from the Wuhan Huoshenshan Hospital ICU ward. ACHs have a great impact on the infection risk from airborne exposure, while they have little effect on the infection risk from surface exposure. The variant strains demonstrated significantly increased viral loads and risks of infection. The level of protection for nurses and surgeons should be increased when treating patients infected with variant strains, and new disinfection methods, electrostatic adsorption and other air purification methods should be used in all human environments. The results of this study may provide a theoretical reference and technical support for reducing the occurrence of nosocomial infections.
Abstract
We create a photoionization model embedded in the turbulent interstellar medium (ISM) by using the state-of-the-art Messenger Monte Carlo MAPPINGS V code (M
3
) in conjunction with the ...CMFGEN stellar atmosphere model. We show that the turbulent ISM causes the inhomogeneity of electron temperature and density within the nebula. The fluctuation in the turbulent ISM creates complex ionization structures seen in nearby nebulae. The inhomogeneous density distribution within the nebula creates a significant scatter on the spatially resolved standard optical diagnostic diagrams, which cannot be represented by the spherical constant-density photoionization model. We analyze the dependence of different optical emission lines on the complexity of nebular geometry, finding that the emission lines residing on the nebular boundary are highly sensitive to the complexity of nebular geometry, while the emission lines produced throughout the nebula are sensitive to the density distribution of the ISM within the nebula. Our fractal photoionization model demonstrates that a complex nebular geometry is required for the accurate modeling of H
ii
regions and emission-line galaxies, especially for the high-redshift galaxies, where the ISM is highly turbulent based on increasing observational evidence.
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