Chiang Mai Journal of Science

     Molybdenum disulphide (MoS₂) is emerging as one of the most attractive two-dimensional (2D) materials amongst the transition metal dichalcogenides (TMDs) group. MoS₂ exhibits a thickness-dependent band gap that changes from indirect band gap of ~1.3 eV for bulk MoS₂ to direct band gap of ~1.9 eV in monolayer form. Such indirect-to-direct gap transition due to quantum confi nement results in giant enhancement in photoluminescence quantum yield. Recent study demonstrated that the co-existence of 2H- and 1T-MoS₂ synthesized by hydrothermal method exhibited superior electronic conductivity to those with 2H semiconducting phase. Metallic 1T phase of MoS₂ is attracting much attention due to its high electronic conductivity and potential applications in supercapacitors, thermoelectric energy harvesting, and memristors. In this paper, we investigated a hybrid structure between 2H and 1T of MoS₂ by a hydrothermal process and investigated its optical property via photoluminescence spectra with changes in pH values. Our results indicated that photoluminescence occurred in the visible light region and the band gap was determined to be ~1.96–2.50 eV. In addition, pH of the precursor solution strongly affected the fi nal structure of MoS₂ nanocrystals, which in turn, affected their photoluminescence property wherein pH = 4–5 was identifi ed as optimum for 2H–1T-MoS₂ synthesis.

     In a diversity study of helicosporous hyphomycetes, a new record viz. Neohelicosporium guangxiense was collected, isolated and identified based on multi-gene phylogenetic analyses and morphological evidence. In this study, secondary metabolites of N. guangxiense were also investigated, from which four compounds were isolated and identified, including three α-tetralon derivatives (1-3) and one isocoumarin derivative (4). This is the first time that these compounds were isolated from the fungal genus Neohelicosporium, and compound 1 was firstly isolated from natural resources. Their structures were assigned based on the extensive 1D/2D NMR spectroscopic analyses, ESI-MS, and HR-ESI-MS measurements, especially the 2D NMR spectra of compound 1 were described in detail, and the absolute configuration of compound 1 was also elucidated for the first time. Furthermore, the bioactivities of all compounds were inactive in our bioassays.

     Piperine is a major component of plants of the Piperaceae family which is widely used in medical science. Botrytis cinerea is one of the most important phytopathogenic fungi causes postharvest losses in fruits and vegetables. To verify the possibility of using piperine as a botanical fungicide against B. cinerea, we determined the in vivo and in vitro antifungal activity of piperine against B. cinerea and investigated its antifungal mechanism effects on the mycelial surface, membrane integrity, soluble protein content, superoxide dismutase, catalase, succinate dehydrogenase and the malondialdehyde content of B. cinerea. The in vitro antifungal activity assay indicated that the EC₅₀ value of piperine against B. cinerea was 58.66 μg/mL and the in vivo antifungal assay showed that piperine at 400 μg/mL suppressed 93.88% growth of B. cinerea on Lycopersic esculentum. The antifungal mechanism assay showed that piperine could inhibit mycelial growth of B. cinerea by reducing antioxidant activity, inhibiting the tricarboxylic acid pathway, and lysing the cell membrane. All these results indicated that piperine as a natural component has the potential to control B. cinerea and can be considered as a botanical fungicide for postharvest disease control of gray mold.

     This research investigated the biological control of Ring Spot Disease of Brassicales caused by Alternaria brassicicola, which is an agriculturally important pathogen, using antagonistic yeasts. One hundred fifteen yeasts were isolated from 38 fruits and vegetable leaves. A total of twenty-nine yeast isolates showed the inhibitory activity of A. brassicicola more than a value of 50% by the dual culture method. The result showed that three antagonistic yeast isolates Y107, Y123, and Y16 showed high inhibitory percentages at 75.00%, 73.52%, and 70.33%, respectively. Interestingly, these yeasts inhibited spore germination of A. brassicicola after 12 h within the range of 80.90 to 90.26%. Subsequently, the efficacy of the selected antagonistic yeast against Ring Spots Disease on cabbage seedlings (Brassica oleracea L. var. capitata) and Pak choi (Brassica chinensis L. var. chinensis) was tested in the greenhouse. The result indicated that antagonistic yeast isolate Y107 inhibited the disease at 72.75% and 71.42% in Cabbage seedlings and Pak choi, respectively. However, the efficacy of isolates Y123 and Y16 were not significant in disease inhibition in both Cabbage seedlings (66.67% and 66.08%) and Pak choi (69.83% and 68.92%). Additionally, the antagonistic yeast isolates were identified by phylogenetic analysis of the D1/D2 domain of the large subunit ribosomal RNA (LSU) gene. Yeast isolates Y16 and Y123 were identified to Kurtzmaniella quercitrusa, while isolate Y107 was Hanseniaspora thailandica.

     Cold plasma is a disinfection technique widely used in food, agricultural, and medical industries. This work used cold plasma to sterilize Pseudomonas aeruginosa and cell survivability was determined. RNA sequencing was used to determine the bacterial responses at 1 minute (T1), 3 minutes (T3), and 5 minutes (T5) of cold plasma treatments. The results show that longer treatment leads to lower cell survivability. Cold plasma induced rapid cell responses in P. aeruginosa. Gene Ontology enrichment analysis showed that T5 had the most enriched terms compared to T1 and T3. The most affected genes were those involved in antioxidant production, transcriptional regulators, ribosome formation, transporters, chemotaxis, and cell motility. P. aeruginosa’s initial response (T1) to cold plasma involved the upregulation of antioxidant genes, followed by the downregulation of transcriptional regulators, transporters, chemotaxis, and cell motility as the intermediate response (T3), and the final response (T5) included heavy downregulation in ribosome formation. Previous transcriptome studies of cold plasma focused mainly on prokaryotic cells such as E. coli and B. subtilis, while studies on P. aeruginosa are limited. This study demonstrated the sequential response of P. aeruginosa against cold plasma via transcriptome analysis.

      Dengue virus (DENV) infection has been reported to be continuously increasing worldwide. Currently, there is no effective treatment specific to DENV infection, in addition, the efficiencies of the vaccines are not fully effective against all four circulating DENV serotypes. Therefore, the development of an anti-viral agent to combat DENV infection and lower the risk of disease progression is needed, especially in the endemic area. This study investigated the effect of Terminalia bellirica extract and its combination with alpha-mangostin (α-MG) in lowering the DENV serotype 2 infection in Vero cells and A549 lung adenocarcinoma cells. The phytochemical characterization of T. bellirica extract demonstrated that T. bellirica extract contained a total phenolic compound of 198.29 ± 15.95 mg gallic acid/g extract in which the gallic acid was the major bioactive compound, judged by HPLC. Treatment with 50 μg/mL of T. bellirica extract caused over 50% of DENV envelope protein reduction in Vero cells and showed no significant attenuation upon the six rounds of thermal stress exposures. At an equal concentration, the efficiency of T. bellirica extract in A549 cells was lower than that of Vero cells; however, combination with low-dose α-MG (0.5-2 μg/mL) showed to significantly improve the inhibitory activity of T. bellirica extract. This study demonstrated the great stability of T. bellirica extract to inhibit DENV infection and suggested a combination approach with α-MG offered protection against the DENV tissue tropism.

     The sound absorption performance of rice bran composites was quantitatively investigated through an improved semi-phenomenological approach. Rice bran (RB) was employed as the primary and structural component in the creation of granular-type sound absorbers with urea-formaldehyde (UF) adhesive. The sound absorption coefficient (SAC) was measured by the two-microphone impedance tube method. Samples with a rice bran per volume ratio lower than 253 kg/m3 show peak-valley characteristics in the saturation region of their SAC spectrum. Five non-acoustic parameters for each sample were obtained by direct measurement and fitting the experimental SACs to the semi-phenomenological Johnson-Champoux-Allard (JCA) equivalent fluid model using the least-squares fitting method. Samples with higher proportions of RB demonstrate lower porosity (ϕ), viscous characteristic length (Λ), and thermal characteristic length (Λ'). Flow resistivity (σ) was the only parameter that noticeably increases when RB increased while tortuosity (α_∞) did not show a strong correlation. For the uncertainty analysis of the experimental SAC, multivariate method was used in this study. A new model (NM) was predicated on the power-law relation introduced by Delany and Bazley, in which the SAC was a function of flow resistivity alone. The new model predicted the SAC of RB composites more precisely than the standard Delany-Bazley model (¯Δ_abs(DBM) ≈4.0¯Δ_abs(NM)). The proposed model had the potential to be extended into a more unified empirical model of SAC for granular-typed sound absorbers in future investigations with a broader spectrum of granular materials.

     A series of novel nano-structured manganese pyranopyrazole Schiff base complex (3a-l) has been synthesized and described. This synthetic complexation involved sequential reactions of domino four-component one-pot reaction for the template of pyranopyrazole (1), imination reaction (2) and finally completed by the complexation reaction with manganese to furnish the title compounds (3a-l). The salient of this nano-Schiff base synthetic reaction protocol is that diverse chemical functionalities were successfully incorporated, simple reaction protocol, and easy workup procedure to yield the title compounds from reasonable to moderate yield. All synthesized compounds were characterized by means of NMR, FTIR, EDX, and elemental analyzer, and by comparing the acquired spectra with the literature precedent for different manganese complexes. These findings revealed that the pyranopyrazole derivatives were successfully complexed with manganese to generate nano-Mn-Schiff base compounds. Further complexation of these derivatives generated 12 novel types of the title compounds (3a-l), which can then be subjected for future chemical applications.

      Members of the genus Tulostoma are commonly referred to as stalked puffballs that are known to be found in tropical and temperate regions. More than 155 species had been published worldwide, while 57 species had been reported in Asia. Herein, we present a brief review of the current findings through an overview of recently published literature involving taxonomic updates, diversity, distribution, and sequence data of Tulostoma in Asia. Moreover, two specimens of Tulostoma were collected during the period from 2021 to 2022 in northern Thailand. These two specimens were identified as T. exasperatum based on morphological characteristics. Till today, no sequence data of this species have been recorded. The present study offers the first record of T. exasperatum in Thailand along with the phylogenetic placement of this species within the genus Tulostoma. Comprehensive descriptions, photographic documentation, and comparisons with morphologically similar and phylogenetically related species are provided.