5 research outputs found
Mechanically Robust Fluorinated Graphene/Poly(<i>p</i>âPhenylene Benzobisoxazole) Nanofiber Films with Low Dielectric Constant and Enhanced Thermal Conductivity: Implications for Thermal Management Applications
Low-dielectric materials have found broad applications
in microelectronics
but are limited by poor mechanical properties and thermal conductivity.
In this study, a class of nanocomposite films based on fluorinated
graphene (FG) was developed by replacing the traditional polymer matrix
with a 3D interconnected poly(p-phenylene benzobisoxazole)
(PBO) nanofiber network. The FG nanosheets are uniformly distributed
in the porous network of PBO nanofibers (PBONF) and stacked orderly
to form a nacre-like layered structure while paving effective thermal
conduction paths. Ultimately, the strong interfacial bonding and efficient
synergy between FG and PBONF endow the composite films with unparalleled
tensile properties (strength and modulus up to 295.4 MPa and 7.79
GPa, respectively) and folding endurance (no drop in tensile properties
after 1000 folds), ultralow dielectric constant (as low as 1.71),
and excellent thermal conductivity (12.13 W mâ1 Kâ1). In addition, these FG/PBONF composite films also
exhibit an ultrahigh thermal stability (5% weight loss temperature
higher than 540 °C), which makes them promising for the heat
dissipation of high-power electronic devices in extreme environments
Crystallization and Rheology of Poly(ethylene oxide) in Imidazolium Ionic Liquids
Polymer and ionic liquid (IL) mixtures
have attracted an increasing
amount of attention due to their unique properties and potential applications.
The interactions between polyÂ(ethylene oxide) (PEO) and imidazolium
ILs of different cation alkyl lengths and anion structures have been
investigated by measuring melting points (<i>T</i><sub>m</sub>), contact angles, and rheological properties. <i>T</i><sub>m</sub> of crystalline PEO dramatically decreased when it was
blended with ILs. Similarly, the contact angles of different ILs on
a PEO surface proportionally decreased. The interaction energy, as
calculated from melting point depression using the Flory equation,
increased with the length of imidazolium alkyl cations and the size
of anions. The different anionic structures had a more significant
influence on the interaction energy than the alkyl chain lengths of
cations. These trends accorded with the solubility obtained by high-energy
X-ray diffraction and swelling ratio measurements of PEO in different
ILs [Asai Macromolecules 2013, 46, 2369â2375] and the solubility of polyÂ(methyl methacrylate)
in different ILs [Ueno Langmuir 2014, 30, 3228â3235]. The
rheological behavior of PEO in three different anionic ILs has also
been studied to determine the effect of the anions on PEO conformations.
The molecular weight dependence of the intrinsic viscosity of PEO
in ILs revealed that the solvent quality of ILs (from poor solvents
to good solvents) is highly influenced by anionic structures, which
was consistent with the results of the melting point depression and
contact angle
Metabonomics Approach To Comparing the Antistress Effects of Four Panax ginseng Components in Rats
Different components of Panax ginseng have different properties and medicinal
effects. Metabonomics was
a prospective approach to analyze the global response of endogenous
metabolites to physiological and pathological processes. In this study,
an untargeted metabonomics method using GC/TOFMS combined with multivariate
statistical techniques was applied to compare entire metabolite differences
and the antistress variations among four components of P. ginseng, namely, total ginsenosides (TG), panaxadiol
(PD), panaxatriol (PT), and ginseng polysaccharide (PS), in Wistar
rats. The results of metabolite analysis showed that numerous urine
metabolites involving neurotransmitters, amino acids, organic acids,
and gut microbiota metabolites were changed after administration of
the four components of P. ginseng,
with TG having the least impact on urinary metabolites. The urinary
metabolite profiling of these rats exposed to acute combined stress
(forced swimming and behavior restriction) demonstrated that the four
ginseng components attenuated urine metabolite changes involving gut
microbiota metabolites, tricarboxylic acid (TCA) cycle and energy
metabolites, and organic acids to different degrees, with TG improving
most of the metabolites altered by stress
Global and Targeted Metabolomics Evidence of the Protective Effect of Chinese Patent Medicine <i>Jinkui Shenqi</i> Pill on Adrenal Insufficiency after Acute Glucocorticoid Withdrawal in Rats
Glucocorticoids
are commonly used in anti-inflammatory and immunomodulatory
therapies, but glucocorticoid withdrawal can result in life-threatening
risk of adrenal insufficiency. Chinese patented pharmaceutical product <i>Jinkui Shenqi</i> pill (JKSQ) has potent efficacy on clinical
adrenal insufficiency resulting from glucocorticoid withdrawal. However,
the underlying molecular mechanism remains unclear. We used an animal
model to study JKSQ-induced metabolic changes under adrenal insufficiency
and healthy conditions. SpragueâDawley rats were treated with
hydrocortisone for 7 days with or without 15 days of JKSQ pretreatment.
Sera were collected after 72 h hydrocortisone withdrawal and used
for global and free fatty acids (FFAs)-targeted metabolomics analyses
using gas chromatography/time-of-flight mass spectrometry and ultraperformance
liquid chromatography/quadruple time-of-flight mass spectrometry.
Rats without hydrocortisone treatment were used as controls. JKSQ
pretreatment normalized the significant changes of 13 serum metabolites
in hydrocortisone-withdrawal rats, involving carbohydrates, lipids,
and amino acids. The most prominent effect of JKSQ was on the changes
of FFAs and some [product FFA]/[precursor FFA] ratios, which represent
estimated desaturase and elongase activities. The opposite metabolic
responses of JKSQ in adrenal insufficiency rats and normal rats highlighted
the â<i>Bian Zheng Lun Zhi</i>â (treatment
based on ZHENG differentiation) guideline of TCM and suggested that
altered fatty acid metabolism was associated with adrenal insufficiency
after glucocorticoid withdrawal and the protective effects of JKSQ
Strategy for an Association Study of the Intestinal Microbiome and Brain Metabolome Across the Lifespan of Rats
There is increased
appreciation for the diverse roles of the microbiome-gut-brain
axis on mammalian growth and health throughout the lifespan. Numerous
studies have demonstrated that the gut microbiome and their metabolites
are extensively involved in the communication between brain and gut.
Association study of brain metabolome and gut microbiome is an active
field offering large amounts of information on the interaction of
microbiome, brain and gut but data size and complicated hierarchical
relationships were found to be major obstacles to the formation of
significant, reproducible conclusions. This study addressed a two-level
strategy of brain metabolome and gut microbiome association analysis
of male Wistar rats in the process of growth, employing several analytical
platforms and various bioinformatics methods. Trajectory analysis
showed that the age-related brain metabolome and gut microbiome had
similarity in overall alteration patterns. Four high taxonomical level
correlated pairs of âmetabolite type-bacterial phylumâ,
including âlipids-Spirochaetesâ, âfree fatty
acids (FFAs)-Firmicutesâ, âbile acids (BAs)-Firmicutesâ,
and âNeurotransmitters-Bacteroidetesâ, were screened
out based on unit- and multivariant correlation analysis and function
analysis. Four groups of specific âmetabolite-bacteriumâ
association pairs from within the above high level key pairs were
further identified. The key correlation pairs were validated by an
independent animal study. This two-level strategy is effective in
identifying principal correlations in big data sets obtained from
the systematic multiomics study, furthering our understanding on the
lifelong connection between brain and gut