Hasil untuk "Physical and theoretical chemistry"

Xuxia Wang, Fuchun Lin, Yan Kang et al.

Visual deprivation leads to structural neuroplasticity in the blind subjects, including gray matter (GM) and white matter (WM) atrophy and alterations in structural connectivity. The rat model of binocular enucleation (BE) is a frequently used animal model for studying brain plasticity induced by early blindness. Yet few neuroimaging studies have been performed on this model to investigate whether or not the BE rats have image phenotypes similar to or comparable to, those observed in the early blind subjects. The current study aimed to assess brain structural plasticity in BE rats using anatomical magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI). The results demonstrated that early BE at postnatal day 4 (P4) caused almost complete degeneration of optic nerve (ON) and optic chiasma (OCH), atrophy in a number of visual and non-visual structures, including optic tract (OT), dorsal lateral geniculate nucleus (DLG) and corpus callosum (CC). The BE rats also exhibited impairments of WM microstructural integrity in the OT, and reduction of structural connectivity between the normal-appearing visual cortex (VC) and somatosensory/motor cortices at 4 months of age, likely as manifestations of deafferentation-induced maldevelopment. The structural neuroplasticity in BE rats observable to structural MRI parallels largely with what has been reported in blind subjects, suggesting that longitudinal neuroimaging studies on animal models of sensory deprivation can provide insights into how the brain changes its wiring and function during development/adaption in response to the lack of sensory stimuli.

Mariya YAMAGISHI, Chengchao ZHONG, Daisuke SHIBATA et al.

All-solid-state batteries experience irreversible capacity loss particularly in the initial potential cycle, owing to electrolyte decomposition at the electrode/electrolyte interface. A strategy for expanding the oxidation stability of electrolytes is replacing the anion with fluorine. However, fluorine substitution has a negative influence on ionic conductivity. In this study, we introduced trace amounts of fluorine into Li3YCl6 solid electrolytes which exhibit high ionic conductivities and wide potential windows. The effect of replacement on ionic conductivity, oxidation stability, and charge–discharge characteristics were studied. The trace amounts of fluorine in Li3YCl6 did not reduce the conductivity, but improved the apparent oxidation stability. The decomposed product of LiF from the fluorine-substituted electrolyte disturbed the formation of a high-resistance layer at the electrode/electrolyte interface. The initial charge–discharge efficiency of the uncoated LiCoO2 cathode was improved by the trace amount of fluorine replacement in the Li3YCl6 solid electrolyte.

Gekière, Antoine, Michel, Apolline, Semay, Irène et al.

Intensive landscape modifications have led to the loss of floral resources, partly in early spring when bumble bee queens need suitable pollen to establish their brood. Adequate floral resources are also crucial to mitigate parasite infection, a stress compromising reproductive success. Among early blooming trees, willows represent an important and highly suitable pollen resource. Alas, riparian areas and their associated willows have been declining. In this study, we found that hedgerow and orchard pollen were at least as suitable as willow pollen for bumble bee survival and microcolony development. Moreover, orchard pollen seemed an interesting candidate to help reduce parasite infection, but unlikely due to its flavonoids. Such non-willow trees could then be favoured in agri-environmental schemes implemented in bee conservation strategies, but pollen chemicals underlying beneficial effects remain to be determined.

Mohamed K. Mostafa, Ahmed S. Mahmoud, Mohamed S. Mahmoud et al.

Predicting the adsorption performance to remove organic pollutants from wastewater is an essential environmental-related topic, requiring knowledge of various statistical tools and artificial intelligence techniques. Hence, this study is the first to develop a quadratic regression model and artificial neural network (ANN) for predicting biochemical oxygen demand (BOD) removal under different adsorption conditions. Nanozero-valent iron encapsulated into cellulose acetate (CA/nZVI) was synthesized, characterized by XRD, SEM, and EDS, and used as an efficient adsorbent for BOD reduction. Results indicated that the medium pH and adsorption time should be adjusted around 7 and 30 min, respectively, to maintain the highest BOD removal efficiency of 96.4% at initial BOD concentration Co=100 mg/L, mixing rate=200 rpm, and adsorbent dosage of 3 g/L. An optimized ANN structure of 5–10–1, with the “trainlm” back-propagation learning algorithm, achieved the highest predictive performance for BOD removal (R2: 0.972, Adj-R2: 0.971, RMSE: 1.449, and SSE: 56.680). Based on the ANN sensitivity analysis, the relative importance of the adsorption factors could be arranged as pH>adsorbent dosage>time≈stirring speed>Co. A quadratic regression model was developed to visualize the impacts of adsorption factors on the BOD removal efficiency, optimizing pH at 7.3 and time at 46.2 min. The accuracy of the quadratic regression and ANN models in predicting BOD removal was approximately comparable. Hence, these computational-based methods could further maximize the performance of CA/nZVI material for removing BOD from wastewater under different adsorption conditions. The applicability of these modeling techniques would guide the stakeholders and industrial sector to overcome the nonlinearity and complexity issues related to the adsorption process.

Bazin, Dominique, Vekeman, Jelle, Wang, Qing et al.

In this contribution, we would like to underline the peculiar chemical properties of nanometer scale metallic particles. To attain this goal, we select the case of DeNox catalysis (NOx reduction to nitrogen molecule) for which such nanomaterials play a crucial role. Experimental data as well as recent theoretical calculation through density functional theory are used to assess the relationship between the adsorption mode of NO and the behaviour of nanometre scale metallic particles.

Fan Qin, Li Jiang, Pengming Long et al.

The silanization of metal surface is a new and environmental anti-corrosion technology. SiO2 film has been prepared on copper by an electrochemically-assisted deposition technology using tetraethoxysilane as a silane reagent in this research. The effect of deposition potential on structure and performance of SiO2 film were also studied. The results indicate that SiO2 is the main component of the deposited films. As the deposition potential changes from -1.0V to -1.5V, the value of SiO2 content, film deposition rate and film thickness all increase first and then decrease. When the deposition potential is -1.4V, the deposition rate of SiO2 film is the fastest (1.13×10-5g·cm-2·s-1) and this film is also the thickest (69.1 μm). Moreover, the prepared SiO2 film has obvious barrier property and can improve the corrosion resistance of the Cu substrate.

Yang Yang, Xiuyun Chuan, Jianzhuo Li et al.

Aqueous Zn-ion battery (ZIB) is recognized as one of the most promising candidates for large-scale energy storage due to its unique properties of excellent safety, cost effectiveness and environmental benignity. However, the application of ZIB is hampered by the restricted availability of suitable cathode materials. In this work, porous tubular MoS2 was prepared by template-assisted thermal decomposition, in which (NH4)2MoS4 was utilized as a precursor and natural halloysite as a template. As a promising cathode material for ZIB, the prepared MoS2 exhibited a good specific capacity of 146.2 mAh g-1 at 0.2 A g-1 and excellent cycling performance with 74.0% capacity retention after 800 cycles. Furthermore, the proposed MoS2 demonstrated a great rate capability even at 1 A g-1. This work provides a promising cathode material for ZIBs, and opens up new possibilities for its future application in renewable energy storage.

Yuehong Pang, Qiufang Zhang, Xiulan Sun et al.

Inspired from the pathogenic process of diphenylalanine (FF) self-assembly, a key structural motif in forming Alzheimer’s β-amyloid peptide fibrils, a facile way for preparation of FF aromatic dipeptide fibrils and fabrication of an electrochemical biosensor were developed. Long persistence length FF fibrils with ultra-high aspect ratio over 1000 were obtained using cationic surfactant assisted evaporation induced self-assembly. The Cotton effects indicate a signature of dominant β-sheet arrangement and the thickness of the β-sheet monolayer is estimated to be 2.38 nm. The obvious blue-shift of intrinsic fluorescence indicates an extended H-aggregate between the phenyl rings in a parallel mode. The FF fibrils based electrochemical biosensor, taking horseradish peroxidase as a model enzyme, displayed an excellent electrocatalytic activity to the reduction of H2O2. The peak current was a linear function of concentrations ranging from 7.5×10-7 to 1.4×10-5 M, with a detection limit of 2.5×10-7 M. The apparent Michaelis-Menten constant was 7.2 μM. These results indicate that the FF fibrils with ultra-high aspect ratio providing a new and promising platform for construction of electrochemical biosensors.

George William Kajjumba, Serdar Aydın, Sinan Güneysu

The use of adsorption using nanomaterials has become a very competitive method for removal of hazardous materials from wastewater. With increasing consumption of fossil fuels and development of energy storage systems, the levels of vanadium pollution are expected to increase. Utilizing natural shale and coal waste as adsorbents, batch adsorption, isotherms, and kinetics of vanadium was studied. The adsorption characteristics of shale and coal waste were studied using Fourier Transform Infrared spectroscope and Scanning Electron Microscopy. The effect of pH, the amount of adsorbent, vanadium concentration, temperature, and contact time between adsorbate and adsorbents were also studied to obtain optimum conditions for maximum adsorption of vanadium. The Fourier Transform Infrared results show little distortion in the vibration of bands, and hence the surface properties remain unchanged for both sorbents after adsorption. The adsorption kinetics are best described by pseudo-second order, while Langmuir model fits the adsorption isotherm for both adsorbents. Maximum sorption capacity is 67.57 mg/g for shale while that of coal is 59.88 mg/g at 298 K and pH 3. For both adsorbents, the adsorption process is spontaneous, endothermic, and chemisorption in nature. Both adsorbents can effectively be recycled twice.