53 research outputs found
Traffic density, congestion externalities, and urbanization in China
<p>Although there is an abundant regional literature analyzing traffic congestion, only a few studies have explored extending such analysis with spatial effects. This study uses a dynamic spatial Durbin model and city-level panel data for the period 2003â14 to investigate the spatial spillover effects of traffic congestion on urbanization in China. The results show that there is an inverted âUâ-shaped relationship between urbanization and traffic density in local and neighbouring cities, and congestion effects have appeared. In the short and long run, the spatial effects of traffic congestion have become an important force restricting the effective promotion of urbanization in China.</p
Substituent Effect of Phenolic Aldehyde Inhibition on Alcoholic Fermentation by Saccharomyces cerevisiae
Phenolic compounds significantly
inhibit microbial fermentation
of biomass hydrolysates. To understand the quantitative structureâinhibition
relationship of phenolic aldehydes on alcoholic fermentation, the
effect of 11 different substituted benzaldehydes on the final ethanol
yield was examined. The results showed that the degree of phenolic
benzaldehyde inhibition was strongly associated with the position
of phenolic hydroxyl groups but not the number of phenolic hydroxyl
groups. It was observed that <i>ortho</i>-substituted 2-hydroxybenzaldehyde
resulted in 15â20-fold higher inhibition than the <i>meta</i>- or <i>para</i>-substituted analogues of 3- and 4-hydroxybenzaldehydes.
From the correlation of the molecular descriptors to inhibition potency
in yeast fermentation, we found a strong relationship between the
octanol/water partition coefficient (log <i>P</i>) of aldehydes
and the EC<sub>50</sub> value. The most inhibitory 2-hydroxybenzaldehyde
has the highest log <i>P</i> and possesses an <i>ortho</i> âOH group capable of forming an intramolecular hydrogen bond,
which can potentially increase the cell membrane permeability and
toxicity. The results also indicated that the calculated free energy
change between phenolic aldehydes and amino acids can be used to predict
their structureâinhibitory activity relationship
Inhibitory Activity of Carbonyl Compounds on Alcoholic Fermentation by Saccharomyces cerevisiae
Aldehydes and acids play important
roles in the fermentation inhibition
of biomass hydrolysates. A series of carbonyl compounds (vanillin,
syringaldehyde, 4-hydroxybenzaldehyde, pyrogallol aldehyde, and <i>o</i>-phthalaldehyde) were used to examine the quantitative
structureâinhibitory activity relationship of carbonyl compounds
on alcoholic fermentation, based on the glucose consumption rate and
the final ethanol yield. It was observed that pyrogallol aldehyde
and <i>o</i>-phthalaldehyde (5.0 mM) reduced the initial
glucose consumption rate by 60 and 89%, respectively, and also decreased
the final ethanol yield by 60 and 99%, respectively. Correlating the
molecular descriptors to inhibition efficiency in yeast fermentation
revealed a strong relationship between the energy of the lowest unoccupied
molecular orbital (<i>E</i><sub>LUMO</sub>) of aldehydes
and their inhibitory efficiency in fermentation. On the other hand,
vanillin, syringaldehyde, and 4-hydroxybenzaldehyde (5.0 mM) increased
the final ethanol yields by 11, 4, and 1%, respectively. Addition
of vanillin appeared to favor ethanol formation over glycerol formation
and decreased the glycerol yield in yeast fermentation. Furthermore,
alcohol dehydrogenase (ADH) activity dropped significantly from 3.85
to 2.72, 1.83, 0.46, and 0.11 U/mg at 6 h of fermentation at vanillin
concentrations of 0, 2.5, 5.0, 10.0, and 25.0 mM correspondingly.
In addition, fermentation inhibition by acetic acid and benzoic acid
was pH-dependent. Addition of acetate, benzoate, and potassium chloride
increased the glucose consumption rate, likely because the salts enhanced
membrane permeability, thus increasing glucose consumption
Women and tropical diseases. Introduction
Conversion of chemical signals into mechanical force is very important for implementation of stimuli-responsive hydrogels. We design a coreâshell hydrogel capsule that can translate the variations of alcohol concentration into mechanical force. Oil-in-water-in-oil (O/W/O) emulsions are prepared with microfluidic technique and serve as templates for the synthesis of the coreâshell capsules. The oil core is ejected from the capsule by the mechanical force generated from the deswelling of the capsule membrane upon increasing the alcohol concentration at a certain temperature below the lower critical solution temperature. The influences of alcohol concentration and temperature on the deswelling process of capsule membranes are investigated systematically. The deswelling rate also plays an important role in the ejection of the oil core. These demonstrations of conversion of alcohol concentration variations into mechanical force provide proof that these coreâshell capsules can function as both sensors and actuators of alcohols
Comprehensive Effects of Metal Ions on Responsive Characteristics of P(NIPAM-<i>co</i>-B18C6Am)
Comprehensive investigations of the effects of species
and concentrations
of metal ions on the ion-responsive behaviors of polyÂ(<i>N</i>-isopropylacrylamide-<i>co</i>-benzo-18-crown-6-acrylamide)
(PÂ(NIPAM-<i>co</i>-B18C6Am)) are systematically carried
out with a series of PÂ(NIPAM-<i>co</i>-B18C6Am) linear copolymers
and cross-linked hydrogels containing different crown ether contents.
The results show that when the B18C6Am receptors form stable B18C6Am/M<sup><i>n</i>+</sup> hostâguest complexes with special
ions (M<sup><i>n</i>+</sup>), such as K<sup>+</sup>, Sr<sup>2+</sup>, Ba<sup>2+</sup>, Hg<sup>2+</sup>, and Pb<sup>2+</sup>,
the LCST of PÂ(NIPAM-<i>co</i>-B18C6Am) increases due to
the repulsion among charged B18C6Am/M<sup><i>n</i>+</sup> complex groups and the enhancement of hydrophilicity, and the order
of the shift degree of LCST of PÂ(NIPAM-<i>co</i>-B18C6Am)
is Pb<sup>2+</sup> > Ba<sup>2+</sup> > Sr<sup>2+</sup> >
Hg<sup>2+</sup> > K<sup>+</sup>. With increasing the content of
pendent crown ether
groups, the LCST shift degree increases first and then stays unchanged
when the B18C6Am content is higher than 20 mol %. Remarkably, it is
found for the first time that there exists an optimal ion-responsive
concentration for the PÂ(NIPAM-<i>co</i>-B18C6Am) linear
copolymer and cross-linked hydrogel in response to special metal ions,
at which concentration the PÂ(NIPAM-<i>co</i>-B18C6Am) exhibits
the most significant ion-responsivity either in the form of linear
copolymers or cross-linked hydrogels. With an increase of the content
of crown ether groups, the value of corresponding optimal ion-responsive
concentration increases. Interestingly, there exists an optimal molar
ratio of metal ion to crown ether for the PÂ(NIPAM-<i>co</i>-B18C6Am) copolymer in response to Pb<sup>2+</sup>, which is around
4.5 (mol/mol). If the ion concentration is too high, the ion-responsive
behaviors of PÂ(NIPAM-<i>co</i>-B18C6Am) may even become
surprisingly unobvious. Therefore, to achieve satisfactory ion-responsive
characteristics of PÂ(NIPAM-<i>co</i>-B18C6Am)-based materials,
both the operation temperature and the ion concentration should be
optimized for the specific ion species. The results in this study
provide valuable guidance for designing and applying PÂ(NIPAM-<i>co</i>-B18C6Am)-based ion-responsive materials in various applications
Wetting-Induced Coalescence of Nanoliter Drops as Microreactors in Microfluidics
Controllable
one-to-one coalescence of surfactant-stabilized nanoliter water drops
is successfully achieved from wetting-induced drop engulfing in microfluidics
by surrounding one of the drops with a thin layer of immiscible wetting
fluid. This wetting layer can spread over the other drop to drain
away the liquid film between the two drops, thereby inducing coalescence.
This innovative approach is totally spontaneous and highly potential
in a myriad of fields, such as quantitative analysis, microreaction,
and high-throughput injection. To demonstrate this potential, we successfully
perform the drop-coalescence-triggered microreaction in microchannels
for pH indicator and syntheses of functional materials including
micro- and nanoparticles
Additional file 1: of A modified endoscopic submucosal dissection for a superficial hypopharyngeal cancer: a case report and technical discussion
A novel method-Lianjun Di video of ESD procedure, this is video of ESD procedure for the patient. (MP4 88400 kb
Portable Diagnosis Method of Hyperkalemia Using Potassium-Recognizable Poly(<i>N</i>âisopropylacrylamide-<i>co</i>-benzo-15-crown-5-acrylamide) Copolymers
A novel,
simple, portable, and low-cost method for diagnosis of
hyperkalemia by using K<sup>+</sup>-recognizable polyÂ(<i>N</i>-isopropylacrylamide-<i>co</i>-benzo-15-crown-5-acrylamide)
[polyÂ(NIPAM-<i>co</i>-B15C5Am)] linear copolymer as indicator
is presented in this work. The pendent 15-crown-5 units in the linear
copolymers can selectively and specifically recognize K<sup>+</sup> to form stable 2:1 âsandwichâ hostâguest complexes,
which cause the copolymer chains to change from the hydrophilic state
to the hydrophobic state isothermally, whereas other tested metal
ions (e.g., Li<sup>+</sup>, Na<sup>+</sup>, Cs<sup>+</sup>, Mg<sup>2+</sup>, Ca<sup>2+</sup>, Sr<sup>2+</sup>, Ba<sup>2+</sup>, Cu<sup>2+</sup>, Fe<sup>3+</sup>, Pb<sup>2+</sup>, Cd<sup>2+</sup>, Cr<sup>3+</sup>) cannot be recognized. With increasing the 15-crown-5 content
or the K<sup>+</sup> concentration, the polyÂ(NIPAM-<i>co</i>-B15C5Am) linear copolymers exhibit higher sensitivity to K<sup>+</sup>. The hyperkalemia can be simply diagnosed by observing the K<sup>+</sup>-induced optical transmittance change of human blood samples
with polyÂ(NIPAM-<i>co</i>-B15C5Am) linear copolymer as an
indicator. Normal blood samples with low potassium level containing
the polyÂ(NIPAM-<i>co</i>-B15C5Am) linear copolymer are almost
transparent since the copolymer is hydrophilic and soluble at the
operating temperature. However, severe hyperkalemia samples with high
potassium level become completely cloudy since the copolymer is hydrophobic
and insoluble at this temperature. The presented diagnosis method
with polyÂ(NIPAM-<i>co</i>-B15C5Am) linear copolymer as indicator
is quite simple and low-cost, and it would bring a new candidate material
to design simple and portable tools for diagnosis of hyperkalemia
in the general population. Moreover, the results in this work provide
valuable guidance for building novel polyÂ(NIPAM-<i>co</i>-B15C5Am)-based artificial K<sup>+</sup>-recognizable âsmartâ
or âintelligentâ systems in various application fields
Conversion of Alcoholic Concentration Variations into Mechanical Force via CoreâShell Capsules
Conversion of chemical signals into mechanical force is very important for implementation of stimuli-responsive hydrogels. We design a coreâshell hydrogel capsule that can translate the variations of alcohol concentration into mechanical force. Oil-in-water-in-oil (O/W/O) emulsions are prepared with microfluidic technique and serve as templates for the synthesis of the coreâshell capsules. The oil core is ejected from the capsule by the mechanical force generated from the deswelling of the capsule membrane upon increasing the alcohol concentration at a certain temperature below the lower critical solution temperature. The influences of alcohol concentration and temperature on the deswelling process of capsule membranes are investigated systematically. The deswelling rate also plays an important role in the ejection of the oil core. These demonstrations of conversion of alcohol concentration variations into mechanical force provide proof that these coreâshell capsules can function as both sensors and actuators of alcohols
Rational Optimization of Bifunctional Organoboron Catalysts for Versatile Polyethers via Ring-Opening Polymerization of Epoxides
Quaternary ammonium and phosphonium borane bifunctional
catalysts
have shown high catalytic performance in ring-opening polymerization
(ROP) of epoxides to produce polyether. Herein, we systematically
investigate a series of well-defined organoboron catalysts by varying
the electronic and steric properties of the Lewis acidic boron (B)
centers, manipulating the steric hindrance on the ammonium cation
(N+), adjusting the distance between B and N+, and regulating the nucleic B number of the catalysts. The investigation
on the dinuclear catalysts indicated that the reactivity of a given
catalyst could be speculated by its BâNâB angle and
the B···B distance. We found that the increase of Lewis
acidity and the number of B centers of the organoboron catalysts are
useful for a high catalytic activity for ROP of epoxides. The Lewis
acidity of the B centers was determined using the acceptor numbers,
showing an order of borinane (23.4) > BBN (21.7) > BCy2 (18.8) > Bpin (15.5). Moreover, we demonstrated the production
of
various telechelic polyols in the presence of different chain transfer
agents using the organoboron catalysts. The produced telechelic samples
have a well-defined terminal functionality with controllable molecular
weight. Lastly, these organoboron catalysts were utilized to produce
block copolymers, allyl-terminated macromonomers, and random copolymers
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