Response of Root Exudates of Bruguiera gymnorrhiza (L.) to Exposure of Polycyclic Aromatic Hydrocarbons

Root exudates play a pivotal role in the behaviors of polycyclic aromatic hydrocarbons (PAHs) in mangrove sediments, but the knowledge of how mangrove root exudates response to PAHs pollutants is limited. This study examined the root exudates of Bruguiera gymnorrhiza (L.) (B. gymnorrhiza) under exposure in phenanthrene, pyrene, and benzo[a]pyrene solution through a 45 days hydroponic cultivation. The results showed that the root exudates of B. gymnorrhiza were mainly hydrocarbon compounds. Tartaric acid was the dominant low molecular weight organic acids (LMWOAs) in root exudates. Under PAHs stress, the proportion of hydrocarbon compounds in root exudates decreased, while the proportion of amide compounds increased. At the first 15 days exposure, the amounts of dissolved organic carbon, soluble total sugars, total organic acids and LWMOAs all increased and reached the maximum values, subsequently, the amounts of root exudates had dropped. The degradation rates of PAHs followed the sequence of phenanthrene > pyrene > benzo [a] pyrene, and the presence of root exudates can significantly enhance the degradation of PAHs. The results illustrated that PAHs stress can significantly change the concentrations and species of root exudates. This study provides the scientific reference for understanding the ability of B. gymnorrhiza response to PAHs stress.

The Influence of Residue Mixing on the Decomposition of Pepper Root Residues

(1) Background: Residue degradation plays a very important role in terrestrial ecosystems and residue mixing is the main factor affecting the degradation rates. However, in the agricultural systems, the effect of residue mixing on the degradation of pepper residues and the microbial community in pepper root residues is not clear. (2) Methods: In this study, we added different residues into soil by using double-layered nylon litterbags in culture bottles. The treatments including pepper root (P: Capsicum annuum L.), soybean [S: Glycine max (L.) Merr.] and maize (M: Zea mays L.) residue, as well as mixtures of soybean + pepper (SP), maize + pepper (MP), maize + soybean + pepper (MSP) mixtures. Litterbags were harvested after 7, 14, 28, and 56 days, respectively. Mass loss and nitrogen and phosphorus contents in pepper residue were quantified and bacterial and fungal community levels in pepper residues were analyzed using quantitative PCR and high throughput amplicon sequencing; (3) Results: The study showed that the mass loss and fungal community abundance of pepper root residue in mixtures were higher than P, except day 7. The phosphorus contents in MSP-P and MP-P were significantly lower than that for P at day 28 and day 56. Illumina MiSeq sequencing showed that the presence of maize residue significantly altered the microbial community composition of pepper root pepper. Day 56. (4) Conclusions: Our results suggest that residue mixing changed the microbial community abundance in pepper residue and promoted the degradation of pepper residues compared to pepper residue decomposition alone, especially for mixtures with soybean.

Revised Michaelis-Menten rate law with time-varying molecular concentrations

Despite over a century's use as a dominant paradigm in the description of biochemical rate processes, the Michaelis-Menten (MM) rate law stands on the restrictive assumption that the concentration of the complex of interacting molecules, at each moment, approaches an equilibrium much faster than the molecular concentration changes. The increasingly-appreciated, remedied form of the MM rate law is also based on this quasi-steady state assumption. Although this assumption may be valid for a range of biochemical systems, the exact extent of such systems is not clear. In this study, we relax the quasi-steady state requirement and propose the revised MM rate law for the interactions of molecules with active concentration changes over time. Our revised rate law, characterized by rigorously-derived time delay effects in molecular complex formation, improves the accuracy of models especially for protein-protein and protein-DNA interactions. Our simulation and empirical data analysis show that the improvement is not limited to the quantitatively better characterization of the dynamics, but also allows the prediction for qualitatively new patterns in the systems of interest. The latter include the oscillation condition and period patterns of the mammalian circadian clock and the spontaneous rhythmicity in the degradation rates of circadian proteins, both not properly captured by the previous approaches. Moreover, our revised rate law is capable of more accurate parameter estimation. This work offers an analytical framework for understanding rich dynamics of biomolecular systems, which goes beyond the quasi-steady state assumption.

Modelling the Impedance Response of Graded LiFePO4 Cathodes for Li-Ion Batteries

Graded electrodes for Li-ion batteries aim to exploit controlled variations in local electrode microstructure to improve overall battery performance, including reduced degradation rates and increased capacity at high discharge rates. However, the mechanisms by which grading might deliver performance benefit, and under what conditions, are not yet fully understood. A Li-ion battery electrochemical model (a modified Doyle-Fuller-Newman type model capable of generating impedance functions) is developed in which local microstructural changes are captured in order to understand why and when graded electrodes can offer performance benefits. Model predictions are evaluated against experimental electrochemical impedance data obtained from electrodes with micro-scale, controlled variations in microstructure. A region locally enriched with carbon at the electrode/current collector interface is shown to significantly reduce the overpotential distribution across the thickness of a LiFePO$_4$-based Li-ion battery cathode, resulting in a lower charge transfer resistance and impedance. The insights gained from the LiFePO$_4$-based electrodes are generalised to wider design principles for both uniform and graded Li-ion battery electrodes.

Copper (II) Heterocyclic Thiosemicarbazone Complexes as Single-Source Precursors for the Preparation of Cu9S5 Nanoparticles: Application in Photocatalytic Degradation of Methylene Blue

In this study, two copper(II) complexes, [Cu(C6H8N3S2)2]Cl2 (1) and [Cu(C7H10N3S2)2]Cl2·H2O (2), were synthesized from 2-(thiophen-2-ylmethylene)hydrazine-1-carbothioamide (L1H) and 2-(1-(thiophen-2-yl)ethylidene)hydrazine-1-carbothioamide (L2H) respectively and characterized using various spectroscopic techniques and elemental analyses. The as-prepared complexes were used as single-source precursors for the synthesis of oleylamine-capped (OLA@CuxSy), hexadecylamine-capped (HDA@CuxSy), and dodecylamine-capped (DDA@CuxSy) copper sulphide nanoparticles (NPs) via the thermolysis method at 190 °C and 230 °C and then characterized using powder X-ray diffraction (p-XRD), UV-visible spectroscopy, transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The p-XRD diffraction patterns confirmed the formation of crystalline rhombohedral digenite Cu9S5 with the space group R-3m. The TEM images showed the formation of nanoparticles of various shapes including hexagonal, rectangular, cubic, truncated-triangular, and irregularly shaped Cu9S5 nanomaterials. The SEM results showed aggregates and clusters as well as the presence of pores on the surfaces of nanoparticles synthesized at 190 °C. The UV-visible spectroscopy revealed a general blue shift observed in the absorption band edge of the copper sulphide NPs, as compared to bulk CuxSy, with energy band gaps ranging from 2.52 to 3.00 eV. Energy-dispersive X-ray spectroscopy (EDX) confirmed the elemental composition of the Cu9S5 nanoparticles. The nanoparticles obtained at 190 °C and 230 °C were used as catalysts for the photocatalytic degradation of methylene blue (MB) under UV irradiation. Degradation rates varying from 47.1% to 80.0% were obtained after 90 min of exposure time using only 10 mg of the catalyst, indicating that Cu9S5 nanoparticles have potential in the degradation of organic pollutants (dyes).

COMPARATIVE STUDY ON DEGRADATION OF POLYLACTIC ACID/ SYZYGIUM AROMATICUM COMPOSITES AGEING IN OUTDOOR ENVIRONMENT AND SOIL BURIAL

Major environmental problems resulting from non-degradable components of plastic wastes have awakened great attention to bioplastic as an alternative material. Among various bioplastic materials, polylactic acid (PLA) is recognised as a promising material especially as a food packaging material. The development of PLA composites using various fillers has extensively been in focus in order to preserve the high quality, safety, and extended shelf-life of packed food. Among the interesting fillers is Syzygium aromaticum (SA). SA, also known as clove, has biological activities such as antibacterial, antifungal, insecticidal, and antioxidant properties. This work investigated the effects of SA filler on the degradations of virgin PLA (VPLA) and recycled PLA (RPLA). The VPLA/SA composites and RPLA/SA composites were prepared using the solvent casting method. The content of SA filler varied in the range of 0 to 20 wt%. The composites were aged in outdoor environment and soil burial. The results revealed that the degradation rate was increased with the increase of SA filler in both ageing environments. After 10 weeks of ageing in the outdoor environment, the weight loss of VPLA/SA composites and RPLA/SA composites containing 20 wt% of SA were 7.7% and 12.8% respectively. Whereas in soil burial, the weight loss of VPLA/SA composites and RPLA/SA composites with similar SA content were 25.6% and 38.3% respectively. The degradation rate was observed to be more rapid in the soil burial as compared to the outdoor environment. Comparably, RPLA and RPLA/SA composites experienced higher degradation rates than VPLA and VPLA/SA composites. The degradation rate was consistent with scanning electron microscope (SEM) images which observed the formation of holes, cavities, cleavages, and grooves on the surfaces of the samples. Thermogravimetric analysis (TGA) results on aged samples showed that VPLA/SA composites and RPLA/SA composites that had aged in soil burial decomposed at lower temperatures. The shortening of degradation time of the VPLA/SA composites and RPLA/SA composites could increase their potential to be used as food packaging materials. ABSTRAK: Masalah utama terhadap alam sekitar yang disebabkan oleh sisa plastik yang sukar terurai, telah menarik perhatian terhadap bioplastik sebagai bahan alternatif. Di antara pelbagai jenis bahan bioplastik sedia ada, asid polilaktik(PLA) dilihat sebagai bahan yang paling sesuai terutamanya sebagai bahan pembungkusan makanan. Perkembangan di dalam penghasilan komposit asid polilaktik yang ditambah dengan pelbagai bahan pengisi telah menjadi fokus terutamanya bagi tujuan meningkatkan kualiti, kesegaran dan jangka hayat makanan. Salah satu pengisi yang mendapat perhatian adalah Syzygium aromaticum (SA). SA yang juga dikenali sebagai bunga cengkeh mempunyai aktiviti biologi, seperti sifat antibakteria, antijamur, racun serangga dan antioksidan yang tinggi. Didalam kajian ini, siasatan terhadap kesan penambahan SA terhadap penguraian PLA asal (VPLA) dan PLA kitar semula (VPLA). Komposit VPLA/SA dan komposit RPLA/SA disediakan dengan menggunakan kaedah pelarutan pelarut. Kandungan pengisi SA adalah didalam julat 0 – 20% mengikut berat. Komposit tersebut dibiarkan menua didalam persekitaran luaran dan didalam tanah. Keputusan kajian mendapati bahawa kadar penguraian semakin meningkat dengan penambahan peratus berat bahan pengisi SA setelah melalui penuaan didalam kedua-dua persekitaran. Setelah penuaan selama10 minggu di dalam persekiran luaran, pengurang berat komposit VPLA/SA dan komposit RPLA/SA yang mengandungi 20 wt% SA adalah 7.7% dan 12.8%. Manakala bagi penuaan didalam tanah, pengurangan berat komposit VPLA/SA dan komposit RPLA/SA dengan kandungan SA yang sama masing-masing adalah 25.6% dan 38.3%. Kadar penguraian diperhatikan lebih cepat bagi penuan didalam tanah dibandingkan dengan penuaan didalam persekitaran luaran. Disamping itu, RPLA dan komposit RPLA/SA mengalami kadar penguraian yang lebih tinggi berbanding VPLA dan komposit VPLA/SA. Kadar penguraian adalah konsisten dengan imej yang dihasilkan oleh imbasan mikroskop elektron (SEM) dimana dapat dilihat pembentukan lubang, rongga, pembelahan dan alur di permukaan sampel. Hasil analisis termogravimetri (TGA) terhadap sampel yang telah dituakan menunjukkan bahawa komposit VPLA/SA dan komposit RPLA/SA yang melalui penuaan didalam tanah terurai pada suhu yang lebih rendah. Tempoh penguraian komposit VPLA/SA dan komposit RPLA/SA yang lebih pendek ini meningkatkan potensi penggunaannya komposit ini sebagai bahan pembungkusan makanan.

Photocatalytic Degradation of 4,4′-Isopropylidenebis(2,6-Dibromophenol) on Sulfur-Doped Nano TiO2

In present work, we examine the photocatalytic properties of S-doped TiO2 (S1, S2) compared to bare TiO2 (S0) in present work. The photocatalytic tests were performed in alkaline aqueous solutions (pH = 10) of three differently substituted phenols (phenol (I), 4,4′-isopropylidenebisphenol (II), and 4,4′-isopropylidenebis(2,6-dibromophenol) (III)). The activity of the catalysts was evaluated by monitoring I, II, III degradation in the reaction mixture. The physicochemical properties (particle size, ζ-potential, Ebg, Eu, E0cb, E0vb, σo, KL) of the catalysts were established, and we demonstrated their influence on degradation reaction kinetics. Substrate degradation rates are consistent with first-order kinetics. The apparent conversion constants of the tested compounds (kapp) in all cases reveal the sulfur-loaded catalyst S2 to show the best photocatalytic activity (for compound I and II S1 and S2 are similarly effective). The different efficiency of photocatalytic degradation I, II and III can be explained by the interactions between the catalyst and the substrate solution. The presence of bromine substituents in the benzene ring additionally allows reduction reactions. The yield of bromide ion release in the degradation reaction III corresponds to the Langmuir constant. The mixed oxidation-reduction degradation mechanism results in higher degradation efficiency. In general, the presence of sulfur atoms in the catalyst network improves the degradation efficiency, but too much sulfur is not desired for the reduction pathway.