Polyhydroxybutyrate (PHB) is a biodegradable biopolymer which is useful for various applications including packing, medical and coating materials. An endospore-forming bacterium (strain BP17) was ...isolated from composted soil and evaluated for PHB production. Strain BP17, taxonomically identified as Bacillus drentensis, showed enhanced PHB accumulation and was selected for further studies. To achieve maximum PHB production, the culture conditions for B. drentensis BP17 were optimized through response surface methodology (RSM) employing central composite rotatable design (CCRD). The final optimum fermentation conditions included: pineapple peel solution, 11.5% (v/v); tryptic soy broth (TSB), 60 g/L; pH, 6.0; inoculum size, 10% (v/v) and temperature, 28°C for 36 h. This optimization yielded 5.55 g/L of PHB compared to the non-optimized condition (0.17 g/L). PHB accumulated by B. drentensis BP17 had a polydispersity value of 1.59 and an average molecular weight of 1.15x105 Da. Thermal analyses revealed that PHB existed as a thermally stable semi-crystalline polymer, exhibiting a thermal degradation temperature of 228°C, a melting temperature of 172°C and an apparent melting enthalpy of fusion of 83.69 J/g. It is evident that B. drentensis strain BP17 is a promising bacterium candidate for PHB production using agricultural waste, such as pineapple peel as a low-cost alternative carbon source for PHB production.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Potentiodynamic broadband sum-frequency generation and electrochemistry were used to elucidate the mechanism of ethanol electrooxidation on polycrystalline platinum in acidic electrolytes.
Display ...omitted
► Electrocatalysis of ethanol on polycrystalline Pt surfaces. ► Reaction pathways revealed by sum-frequency generation (SFG) and electrochemistry. ► Surfaces-adsorbed intermediates include CO, acetate, and methyl fragment of ethanol produces –CH
x
. ► –CH
x
is difficult to oxidize. ► Electrolyte anions affect adsorption of intermediates CO and acetate.
Ethanol electrooxidation reaction (EOR) pathways on polycrystalline platinum were studied with broadband sum-frequency generation (BB-SFG) spectroscopy and electrochemistry in unprecedented detail and under working fuel cell conditions. We present the first observation of adsorbed acetate and co-adsorbed sulfuric acid anions with SFG and a discussion of their relation to the EOR. Surface-adsorbed intermediates such as CO on Pt atop sites and acetate are observed in both H
2SO
4 and HClO
4 solutions. However, CO molecules on bridge sites and sulfuric acid anions are found in H
2SO
4 only. At
E
<
0.5
V vs. Ag/AgCl, CO is the predominantly adsorbed species. Increasing the potential to
E
>
0.5
V results in the oxidative removal of CO and the adsorption of acetate anions. Experiments with isotopically labeled ethanol (
12CH
3
13CH
2OH) reveal information on the carbon–carbon bond cleavage and the subsequent CO formation. In particular, the methyl fragment (–
12CH
x
) produces far less
12CO and suggests methyl electroreduction to methane and/or the persistence of –CH
x
on the Pt surface.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPUK
A simple, surfactant-free solvothermal method is reported for the preparation of <10 nm shape-controlled platinum crystallites. Reactions were carried out in N,N -dimethyformamide (DMF) and DMF–water ...mixtures. Effects of reaction time and temperature, DMF–water ratio, and metal precursor salt were examined. When the reaction conditions were tuned, ensembles of Pt particles with dominant truncated octahedral/cuboctahedral or cubic shapes could be formed from the metal acetylacetonate (acac) precursor salt. Metal nanocrystal development was monitored through the use of high-resolution transmission electron microscopy (HR-TEM) and X-ray and electrochemical analysis methods. Voltammograms probing CO and formic acid oxidation over shape-controlled nanocrystals adsorbed to a glassy carbon electrode displayed expected features characteristic of extended (111) and (100) facets, confirming the stability and surface cleanliness of particles taken directly from the reaction mixture. A mechanism for Pt reduction and the growth and stabilization of preferentially shaped Pt nanocrystals in the DMF–water solvent system is proposed. The involvement of DMF as a reducing agent and carboxylate ions as weakly coordinating, and hence easily displaced, nanoparticle capping ligands is discussed.
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IJS, KILJ, NUK, PNG, UL, UM
We investigated the morphology, topology, and mechanical characteristics of a loosely cross-linked epoxy network as a function of the varying content of catechol moieties capable of forming ...reversible, ionic iron–catecholate cross-links. The primary epoxy network structure was kept fixed by a constant mole ratio of difunctional poly(ethylene glycol), monofunctional diluent, and diamine cross-linking agent in all samples. We then systematically replaced the catechol monoepoxide diluent by methyl glycidyl ether, which is incapable of participating in ionic complex formation. This allows the effects of the catechol content on network properties to be isolated and analyzed. Our results support a model in which increasing the concentration of catechol moieties promotes the formation of closely spaced iron–catecholate complex sites. This enables cooperative interactions between netpoints and produces a dramatic improvement in tensile properties. Such ionic interactions are thus a promising approach to creating stiff, strong, and tough load-bearing polymer networks.
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IJS, KILJ, NUK, PNG, UL, UM
Microreactors are desirable for exploring chemical and biological processes, as reactant consumption is minimal and safety issues are easily managed. Levitated drops are a class of microreactors for ...which mixing is continuous and solid/liquid interfaces are absent or of lesser importance than in channeled microfabricated flow reactors. Thus, reactant adsorption or wall catalysis possibly of importance in ordinary microfluidic systems is absent in levitated drops. Transport of gaseous reactants or products is facile. Levitated drop microreactors are amenable to batch or continuous flow study of biochemical reactions. The possibility of studying oscillatory enzyme-catalyzed reactions in drops is apparent. This review explains the physics and chemistry of levitated drop microreactors and describes practical aspects of their design, fabrication, implementation, and optimization. Such considerations as drop evaporation, thermal control, protein behavior at the gas/liquid interface, and observation with spectroscopic and electrochemical probes are discussed.
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► Ultrasonically-levitated drops show promise as reactors for studying biochemical kinetics. ► Such drops are most interesting for systems in which free radicals are reactants or products. ► Fluid handling and diagnostics are sufficiently developed for near-term application. ► Rate constants ≤1s−1 (first order) and ≤106M−1s−1 (second order) should be measurable. ► Complex dynamics such as chaotic oscillations should be well-suited for study in levitated drops.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
Complete genome sequencing has identified millions of DNA changes that differ between humans and chimpanzees. Although a subset of these changes likely underlies important phenotypic differences ...between humans and chimpanzees, it is currently difficult to distinguish causal from incidental changes and to map specific phenotypes to particular genome locations. To facilitate further genetic study of human-chimpanzee divergence, we have generated human and chimpanzee autotetraploids and allotetraploids by fusing induced pluripotent stem cells (iPSCs) of each species. The resulting tetraploid iPSCs can be stably maintained and retain the ability to differentiate along ectoderm, mesoderm, and endoderm lineages. RNA sequencing identifies thousands of genes whose expression differs between humans and chimpanzees when assessed in single-species diploid or autotetraploid iPSCs. Analysis of gene expression patterns in interspecific allotetraploid iPSCs shows that human-chimpanzee expression differences arise from substantial contributions of both
-acting changes linked to the genes themselves and
-acting changes elsewhere in the genome. To enable further genetic mapping of species differences, we tested chemical treatments for stimulating genome-wide mitotic recombination between human and chimpanzee chromosomes, and CRISPR methods for inducing species-specific changes on particular chromosomes in allotetraploid cells. We successfully generated derivative cells with nested deletions or interspecific recombination on the X chromosome. These studies confirm an important role for the X chromosome in
regulation of expression differences between species and illustrate the potential of this system for more detailed
and
mapping of the molecular basis of human and chimpanzee evolution.
Introduction
This survey of international experts in obesity management was conducted to achieve consensus on standardized definitions and to identify areas of consensus and non-consensus in ...metabolic bariatric surgery (MBS) to assist in an algorithm of clinical practice guidelines for the management of obesity.
Methods
A three-round Delphi survey with 136 statements was conducted by 43 experts in obesity management comprising 26 bariatric surgeons, 4 endoscopists, 8 endocrinologists, 2 nutritionists, 2 counsellors, an internist, and a pediatrician spanning six continents over a 2-day meeting in Hamburg, Germany. To reduce bias, voting was unanimous, and the statements were neither favorable nor unfavorable to the issue voted or evenly balanced between favorable and unfavorable. Consensus was defined as ≥ 70% inter-voter agreement.
Results
Consensus was reached on all 15 essential definitional and reporting statements, including initial suboptimal clinical response, baseline weight, recurrent weight gain, conversion, and revision surgery. Consensus was reached on 95/121 statements on the type of surgical procedures favoring Roux-en-Y gastric bypass, sleeve gastrectomy, and endoscopic sleeve gastroplasty. Moderate consensus was reached for sleeve gastrectomy single-anastomosis duodenoileostomy and none on the role of intra-gastric balloons. Consensus was reached for MBS in patients > 65 and < 18 years old, with a BMI > 50 kg/m
2
, and with various obesity-related complications such as type 2 diabetes, liver, and kidney disease.
Conclusions
In this survey of 43 multi-disciplinary experts, consensus was reached on standardized definitions and reporting standards applicable to the whole medical community. An algorithm for treating patients with obesity was explored utilizing a thoughtful multimodal approach.
Graphical Abstract
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The possibility of using atmospheric pressure plasma treatment (APT) without any additional functionalizing chemicals as an environmentally friendly technique for processing cotton nonwovens has been ...investigated. The quantitative determination of waxes suggested that APT results in the removal of waxes from cotton nonwovens and consequently increases its hydrophilicity. Fourier transform infrared studies showed that APT was capable of removing wax covering individual layers of cotton fibers. Intense plasma treatment causes a decrease in the strength of cotton nonwovens. Results show that APT can be a viable alternative for caustic soda treatment for dewaxing cotton.
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IJS, KILJ, NUK, PNG, UL, UM
Broad-band sum frequency generation spectroscopy (BB-SFG) was used to obtain vibrational spectra of CO adsorbates produced from formic acid oxidation on a Pt (1
0
0) electrode in sulfuric acid media.
...The BB-SFG simultaneously monitored all forms of the CO intermediates, including steady-state, as the potential was scanned at 5
mV/s. Spectra were compared to those obtained from CO adsorbed from a CO-saturated electrolyte. While adsorbed from HCOOH, the CO had a sharp atop transition near 2050
cm
−1 and a broader multiply-bonded transitions in the 1700–1900
cm
−1 range, which appear to result from bridge-like and higher-coordinated (possibly fourfold) CO. As the potential scanned from −0.2 to 0.3
V (vs. Ag/AgCl), the bridge-like CO disappeared, and the amount of atop CO increased. At potentials above 0.5
V, the CO was in steady-state, being oxidized on the surface to CO
2 and replenished by CO from HCOOH. These measurements show that BB-SFG can observe potential-dependent interconversion of different CO forms on the electrode surface and can measure steady-state reaction intermediates on a surface in real time.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPUK
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