Tạp chí Khoa học Đại học Huế: Khoa học Tự nhiên
Tạp chí của Đại học Huế
Species composition and distribution characteristics of Bivalvia in the coastal ecosystem of Phu Yen
From the data collected over many years and the results of "Survey, assessment, and proposition of protected areas, preserved ecological landscape of the coastal waters of Phu Yen province", 52 species belonging to 28 genera, 13 families, 6 orders of Bivalvia were identified. In the 13 families recorded, 4 families consist of more than 5 species: Arcidae (9 species), Veneridae (6 species), Ostreidae (6 species), and Pectinidae (6 species). The results reveal that there are nine rare and endangered species with high conservation values, two of which are classified into LC (Least concern) listed in IUCN Red List 2018. Eight species are listed in Vietnam’s Red Data Book (2007), including two Endangered species (EN) and six Vulnerable species (VU). Eight species are classified into Vulnerable, listed in Decision 82/2008 issued by Vietnam’s Ministry of Agriculture & Rural development. In addition, 26 species have economic values. The species composition habitat is relatively versatile: basal layer of loam soil with some sand (30,77%), basal layer of sandy soil with some loam (28,85%); rocks (21,15%), and solid supports (19,23%).
Hue University Journal of Science: Natural Science
Some biological and morphological characteristics of great mormon (papilio memmon linnaeus, 1758– papilionidae) in Hue city and adjacent areas
Great Mormon (Papilio memnon Linnaeus, 1758) is one of the big-sized beautiful butterflies, and in spite of possessing wide distribution, they are rare in nature. This study was carried out from January 2018 to March 2019 in Hue City and the adjacent areas. The results show that the mature butterflies are relatively large (the forewing mean is 71.65 ± 0.59 mm). Female mature butterflies are in two morphologies: non-mimetic and mimetic female. Female butterflies are less numerous than male butterflies. The newly hatched larvae have a relatively rough morphology. The first instar larvae have an initial body length of 4.05 ± 0.15 mm; later, they become more slippery. The fifth instar larvae have an average body length of 54.90 ± 2.11 mm. The pupae have an average length of 39.27 ± 0.61 mm, pointed vertex, and parallel outer. The narrow top is divided into two horn-like structures by a spear-shaped space. Great Mormon larvae eat six plant species belonging to the Rutaceae family, namely Citrus au-rantifolia, C. grandis, C. sinensis, Clausena excavata, Zanthoxylum nitidum, and Atalantia buxifolia. Under the semi-natural culture conditions with the temperature of 27–40 °C (average 37.32 ± 0.27 °C) and relative humidity 70–98% (average 88.69 ± 0.48%), the caterpillars were fed on fresh pomelo leaves (Citrus grandis), and the mature individuals were cultured with several flowers including Ixora coccinea, Lantanacamara, and 50% diluted honey. The life cycle of the butterflies (from egg to mature butterfly) is 33–56 days (average of 49.8 ± 4.2 days).
Effects of gonadotropin on oestrus and reproductive indicators of delayed oestrus common palm civets (Paradoxurus hermaphroditus)
This study evaluates the effectiveness of different doses of hormones (PMSG, HCG) at the time of occurrence, duration of oestrus and reproductive performance of the delayed oestrus civets. The experiment was conducted on 54 female civets and 42 male civets at Dong Nai Biotechnology Center and Thanh Long Wildlife Farm. PMSG/HCG product (Gestavet – UK) was administered intramuscularly in three formulations (CT), namely CT1: 20 IU PMSG + 10 IU HCG; CT2: 30 IU PMSG + 15 IU HCG; CT3: 40 IU PMSG + 20 IU HCG. The results show that the duration of oestrus averages from 1.1 days to 2.6 days after injecting sex hormones. CT3 had the earliest time of estrus. The duration of oestrus lasted from 2.9 to 3.9 days. The shortest estrous time was found at CT1 and the longest estrous time was at CT3 (p < 0.05). The ratio of oestrus and pregnancy increased compared with controls in all experimental civet groups. The average number of civets born on the litter ranges from 1.67 to 3.25 civets/litter; CT3 always had birth civets higher than that on the other formulas (p < 0.05). The average birth weight is from 94.02 to 97.25 g. Formulation CT3 could be applied effectively for the treatment on the first delays and delayed oestrus of the common palm civets.
Optimization of microwave-assisted extraction of betacyanin from red dragon fruit peels
Betacyanin has been widely used as natural coloring agents and dyes in food and textile industries to replace conventional toxic chemical pigments. In this study, the extraction of betacyanin from red dragon fruit peels was optimized using response surface methodology. Betacyanin was determined as the response to three independent variables, namely the ratio of extraction solvent to peels, microwave-assisted treatment time, and pH. The effect of acid ascorbic concentration during the storage of betacyanin extract, the total phenolic content, and DPPH radical scavenging activity were also investigated. The optimum extraction parameters are as follows: the ratio of extraction solvent to peels is 53% (v/w); extraction time is 91 s; pH is 5.3, with the betacyanin content being 72.13 mg/100 g peels. The betacyanin extract supplemented with 0.5% (w/v) ascorbic acid has the longest storage duration. Total phenolic concentration and DPPH radical scavenging activity (IC50) are 41.41 mg GAE/100 mL and 48.02 % (v/v), respectively.
Fermentation of dragon fruit juice by using probiotic lactic acid bacteria
Dragon fruit (Hylocereus undatus), a tropical fruit, is rich in valuable nutrients such as vitamins, minerals, and fiber. Therefore, this fruit can be considered as a suitable source for the growth of lactic acid bacteria. In Vietnam, dragon fruit is directly consumed or used for the production of alcoholic fermented beverages. In this study, the juice was fermented by using Lactobacillus acidophilus to fabricate beverages rich in probiotics to diversify the products. The optimal culture conditions are as follows: pH 6.0, initial cell density of lactic acid bacteria 4.8 × 107 (CFU/mL), dry matter concentration 16 °Bx, and fermentation time 72 h. The product consists of 10 log (or 2.5 × 1010 CFU/mL) of L. acidophilus. The survival of probiotics in fermented dragon fruit juice remains at 94.39% after 2 h in the simulated gastric fluid medium and 77.19% after 4 h in the simulated intestinal fluid medium. After 21 days of storage at 4 °C, the viable count of probiotics decreased to 9.91 log.
Effects of fabrication conditions on formation of chitosan hollow beads
Chitosan has been widely used in biomedical fields due to its high biocompatibility. Especially, chitosan beads with hollow interior are gaining attention because they can absorb more drugs and release them in a sustained manner. Previous studies showed that the formation of chitosan hollow beads required organic solvents and toxic crosslinking reagents, which might limit their application in biological systems. Therefore, this study aims to fabricate chitosan beads with a core/shell structure by using simple ionic gelation in mild conditions. Chitosan synthesized from chitin was used in bead formation with sodium tripolyphosphate (STPP) as a crosslinking agent. Beads with the largest core diameter are obtained from a 2% (w/v) 205.6 kDa chitosan solution in 1% acetic acid at pH = 9 of the STPP solution.
Preliminary study of BRCA1 and BRCA2 mutations among Vietnamese ovarian carcinomas population by using ion personal genome machine platforms
BRCA1 and BRCA2 are two important tumor suppressor genes. The germline and somatic mutations of these two genes in ovarian carcinomas are sensitive for treatment with ADP-ribose polymerase enzyme inhibitor (PARPi). Recently, several PARPi drugs, such as Olaparib and Rucaparib, have been approved for ovarian cancer with BRCA1/2 germline mutations by Food and Drug Administration (FDA), and for both germline and somatic mutations by European Medicines Agency (EMA). However, there have no been reliable data about the prevalence of mutations of these two genes in ovarian carcinomas population for treatment in Vietnam so far. Therefore, we studied the prevalence of the BRCA1/2 germline and somatic mutations among ovarian carcinomas patients in the Vietnamese population. In this study, we sequenced these two genes by using Ion Torrent PGM. The subjects of the study are 11 formalin-fixed paraffin-embedded tumor (FFPE) samples from 11 patients with ovarian carcinomas obtained from Tu Du Hospital of Obstetrics and Gynecology (Vietnam). Multiplex PCR then was performed on the DNA samples and two controls containing known mutations by using Oncomine BRCA Research Assay. Of the sequenced 11 samples, a pathogenic mutation (1/11 patient, 9.1%) detected on the BRCA1 gene was a nonsense point mutation causing stop codon at the position of amino acid 1772. Consequently, our sequencing workflow shows the success in identifying and investigating the prevalence of BRCA1/2 mutation in a small group of ovarian carcinomas with FFPE tumor samples.
Synthesis, characterization, and photocatalytic activity of Cu2O/TiO2/rGO under visible light
In the present paper, the Cu2O/TiO2/rGO photocatalytic material was synthesized using the hydrothermal method. The obtained samples were characterized using X-ray diffraction (XRD), Fourier- transform infrared spectroscopy (FTIR), Energy-dispersive X-ray spectroscopy (EDX), transmission electron microscope (TEM), UV−Vis diffuse reflectance spectroscopy (UV–Vis–DRS) and nitrogen adsorption/desorption measurements. The results show that graphene oxide (GO) with oxygen-containing groups was successfully synthesized from graphite. The nanosized TiO2 in the anatase phase and nanosized Cu2O were dispersed evenly over the reduced graphene oxide (rGO) sheets. The specific surface area of the material decreases as nano-oxide particles are incorporated into the rGO and the band-gap energy of Cu2O/TiO2/rGO sample decreases compared with that of TiO2. The Cu2O/TiO2/rGO nanocomposite exhibits high photocatalytic activity in rhodamine B degradation reaction under visible light.
Screening and analysing toxic genes from Vibrio isolates causing acute hepatopancreatic necrosis disease in white-leg shrimp at Thua Thien Hue
Acute hepatopancreatic necrosis disease (AHPND) is a disease caused by bacteria, with the death ratio up to 100% in the population of Litopenaeus vannamei and Penaeus monodon, and causes great economic losses to many shrimp‐producing countries in Asia. Previous studies have shown that not all strains of Vibrio can cause AHPND because they contain different toxin genes, such as pirAvp, pirBvb, tlh, trh, and tdh. In this study, we evaluate the presence of several toxic genes on Vibrio isolates from Thua Thien Hue province and analyze the sequence of these genes. The results show that in 14 Vibrio strains carrying pirABvp gene, the tlh and toxR genes occur in 14/14 and 7/14 strains, respectively, while none of them have the two genes of trh and tdh. Analyzing the sequence of four DNA fragments shows that these genes have high similarity (98–100%) compared with the genes announced on the Genbank. Genes pirAvp and pirBvp are less different, while tlh and toxR genes are more different. The results could be used for further studies in the production of bioproducts for the prevention and treatment of acute hepatopancreatic necrosis disease in shrimp.
Morphological characteristics and distribution of Najas indica (Wild.) Cham. in Cau Hai lagoon, Thua Thien Hue province
The paper reports the morphological characteristics and distribution of Najas indica in the Cau Hai lagoon from March 2018 to March 2019. N. indica has a fairly wide distribution area in the Cau Hai lagoon, from the center towards the western bank, and exists in 10/21 surveyed sites. The coverage and biomass of N. indica differ significantly in the surveyed months. The species starts to increase its coverage and biomass in April, and the highest value of coverage is recorded from July to November (49.33 ± 15.05%÷52.60 ± 12.28%), while the biomass peak occurs in July (93,61 ± 35,60 g/m²). The distribution of N. indica partly depends on air temperature and salinity. The results demonstrate that air temperature variation is strongly correlated with biomass; whereas, water salinity shows a relatively weak correlation with the species’ biomass and coverage.
Cobalt ferrite hollow spheres: synthesis by hydrothermal method and application as catalyst
This paper describes the in situ synthesis of cobalt ferrite (CoFe2O4) using carbonaceous microspheres prepared from a glucose solution as a template, followed by subsequent heat treatment. The obtained material was characterized using energy-dispersive X-ray spectroscopy (EDX), scanning electrode microscope (SEM), vibrating sample magnetometer (VSM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption/desorption isotherms, and ultraviolet-visible spectroscopy (UV–Vis). The calcination of the precursor provides cobalt ferrite hollow spheres sized 300–400 nm with magnetic saturation of 59 eV. CoFe2O4 was used as a catalyst for rhodamine-B photocatalytic decomposition under visible light. The kinetics of rhodamine-B decomposition is also addressed.
Characteristics of composition species of three aquatic insect orders in Phong Dien Nature Reserve, Thua Thien Hue province
This paper provides the biodiversity data of the species composition of three aquatic insect orders in Phong Dien Nature Reserve, Thua Thien Hue province. Specimens were collected in seven sites (from upper to lower reaches) of streams from February 2018 to March 2019. The results show a total of 54 species of 37 genera and 18 families, belonging to the following orders: Ephemeroptera, Trichoptera, and Plecoptera. The Ephemeroptera (Mayflies) is the most diversified with 34 species (62.96%), 20 genera (54.05%), and 9 families (50.0%). The second is the Trichoptera (Cadisflies) with 11 species (20.37%), 10 genera (27.03%), and 5 families (27.78%). The third is Plecoptera (Stonflies) with 9 species (16.67%), 7 genera (18.92%), and 4 families (22.22%). The number of collected species decreases with decreasing altitudes. The altitudinal distribution is as follows: 46 species, 31 genera, and 15 families under 500 m; 23 species, 19 genera, and 13 families above 500 m. In addition, the number of species individuals of aquatic insects prevails in lotic water compared with lentic water.
Spectroscopic characteristics of M2Al2SiO7: Eu (M: Sr, Ca) phosphors
The europium-ion-doped M2Al2SiO7 (M: Ca, Sr) materials with tetragonal phase structure were successfully synthesized by using the solid-state reaction method. The Eu2+-doped M2Al2SiO7 materials emit green radiation. The photoluminescent spectra have a board band, peaking at 510 nm for the Sr2Al2SiO7 phosphor and 521 nm for the Ca2Al2SiO7 phosphor. Meanwhile, the photoluminescent spectra of the Eu3+-doped M2Al2SiO7 material have narrow lines, emitting red radiation. The role of the europium activation centers in the lattice greatly depends on the conditions of the sample preparation. The crystal field effect of Ca2Al2SiO7 lattice acting on Eu2+ ions is stronger than that of Sr2Al2SiO7 lattice.
Effects of sintering temperature on physical properties of (K0.5Na0.5)NbO3 ceramics
This paper reports the synthesis of K0.5Na0.5NbO3 (KNN) ceramics by using an improved conventional method. The influence of sintering temperatures of the fabricated ceramics on the piezoelectric and dielectric properties was studied. It was found that density increases greatly within a narrow temperature range, and reaches the highest value of 4.2 g/cm3 at 1090 °C, corresponding to a dense microstructure with the tetragonal grain shape. However, when sintering temperature slightly exceeds the optimal one, the density tends to decrease, accompanied by the appearance of abnormal grain growth, which is considered to be due to the intensified volatilization of alkali metal oxides. At a sintering temperature of 1090 °C, the highest values of electromechanical coupling factor (kp) and the piezoelectric coefficient (d33) of the ceramics being 0.22 and 61 pC/N, respectively, may be related to homogenous grains size of orthorhombic phase.
Effects of medium composition on Xa den (Ehretia asperula Zoll. et Mor.) cell cultures
Xa den (Ehretia asperula Zoll. et Mor.) belongs to the Boraginaceae family and appears in Southeast Asian countries. Xa den is often used to treat diseases such as tumors, emphysema, and detoxification. The effects of plant growth regulators and carbon sources on the formation and proliferation of callus from Xa den leaves in vitro were studied. The results show that callus proliferates well on the medium supplemented with 30 mg/L glucose, 0.4 mg/L 2,4-D, and 0.1 mg/L BA. In this medium, the callus is yellowish-green, friable, and rapid proliferating. After the first subculture, the callus is milky white and friable after 10 weeks of culture. This callus is used as a material for cell suspension cultures. Suspension cells grow in the dark better than in the light with the highest biomass after four weeks of culture (149.933 g/L).
Fibers of rational maps and Rees algebras of their base ideals
We consider a ratinonal map $\phi$ from m-dimensional projective space to n-dimensional projective space that is a parameterization of m-dimensional variety. Our main goal is to study the (m-1)-dimensional fibers of $\phi$ in relation with the m-th local cohomology modules of Rees algebra of its base ideal.
Magnetic property of nanoparticle La1-xAxFeO3 (A = Y, Nd) prepared by high-energy milling method
Perovskite ABO3 is a kind of the material possessing various interesting electric and magnetic properties, and these properties can be changed dramatically by doping with rare-earth metals. In this paper, nanocrystalline La1–xYxFeO3 and La1-xNdxFeO3 (0 ≤ x ≤ 0.3) were prepared by using the high-energy milling method. The X-ray diffraction (XRD) analysis reveals that the doped samples are single-phased with orthorhombic structure. The average size of particles, calculated according to the Scherrer equation, is about 16 nm. The doping of Y and Nd into the A position of ABO3 affects the structure and magnetic properties of the material. The magnetic properties of La1–xAxFeO3 exhibit clearly in the hysteresis loop M(H), measured at room temperature. The samples show weak ferromagnetic properties, close to the superparamagnetic state at room temperature.
Representation of some special functions on transcendence basis
The special functions such as multiple harmonic sums, polyzetas or multiple polylogarithm functions are compatible with quasi-shuffle algebras. By using transcendence bases of the quasi-shuffle algebras studied in the paper [4], we will express non-commutative generating series of these special functions and then identify on the local coordinates to reduce their polynomial relations or asymptotic expansions indexed by these bases.
Chemical constituents and cytotoxicity of Aspidistra letreae
A phytochemical investigation of whole Aspidistra letreae plants led to the isolation of 2H-chromen-2-one (1), α-tocopherol (2), (E)-phytol (3), asparenydiol (4) and (25S)-spirost-1β,3α,5β-triol (5). Their structures were determined on the basis of NMR spectral evidences and in comparison with the reported data. Of these, asparenydiol (4) was isolated from the genus Aspidistra for the first time. This is also the first report on the separation and structural determination of (25S)-spirost-1β,3α,5β-triol (5) as a pure compound. The methanol extract from the whole plants of Aspidistra letreae exhibits moderate cytotoxicity against the LU-1, HeLa, MDA-MB-231, Hep-G2, and MKN-7 human cancer cell lines with IC50 values ranging from 52.58 ± 3.65 to 64.78 ± 4.89 μg/mL.
A theoretical study of structure, bonding and property of platinum(II)-8-hydroxyquinolines complexes with carbene and heavier homologues
In this work, a theoretical study for platinum(II)-8-hydroxyquinoline-tetrylene complexes [{PtCl–C9H6NO}–NHEPh] (Pt–EPh) is carried out for the first time by using the density functional theory (DFT). Quantum chemical calculations with DFT and charge methods at the BP86 level with basic sets SVP and TZVPP have been perfomed to get insight into the structures and property of Pt–EPh. The optimization of equilibrium geometries of the ligands EPh in Pt–EPh, bonded in the distorted end-on way to the Pt fragment is studied, in which the bending angle slightly decreases from carbene Pt–CPh to germylene Pt–GePh. Quantum chemical parameters such as EHOMO, ELUMO, the energy gap (ELUMO – EHOMO), electronegativity, global hardness, and global softness in the neutral molecules have been calculated and discussed. Bond dissociation energies decrease from the slighter to the heavier homologues. The hybridization of atoms E has large p characters, while the hybridization of atom Pt has a greater d character. Thus, the Pt–E bond possesses not only NHEPh→{PtCl–C9H6NO} strong -donation but also a significant contribution of π-donation NHEPh→{PtCl–C9H6NO}, and a weak π-backdonation metal-ligand NHEPh←{PtCl-C9H6NO} in complexes Pt-EPh is also considered.
Higher-order nonclassical and entanglement properties in photon-added trio coherent state
This paper studies the higher-order nonclassical and entanglement properties in the photon-added trio coherent state (PATCS). We use the criterion of higher-order single-mode antibunching to evaluate the role of the photon addition operation. Furthermore, the general criteria for detection of higher-order three-mode sum squeezing and entanglement features in the PATCS are also investigated. The results show that the photon addition operation to a trio coherent state can enhance the degree of both the higher-order single-mode antibunching and the higher-order three-mode sum squeezing and enlarge the value of the higher-order three-mode entanglement factor in the photon-added trio coherent state. In addition, the manifestation of the single-mode antibunching and the entanglement properties are more obvious with increasing the higher values of orders.
Pairing effects on neutron elastic scattering at low energies
For the first time, a realistic microscopic calculation for low-energy neutron-nucleus elastic scattering off open-shell nuclei is carried out within the framework of particle-vibration coupling (PVC). In this study, the pairing correlations of the ground state are taken into account. The dependence of the angular distributions on the pairing gaps is discussed.
In vitro antioxidant activity and Content of compounds from Curculigo orchioides rhizome
Curculigo orchioides Gaertn. is used in traditional medicine in Vietnam. Its antioxidant potential was evaluated through DPPH radical scavenging and the total antioxidant capacity method. The data resulted from DPPH radical scavenging activity indicate that Curculigo orchioides display high activity with a low IC50 value (22.78μg/mL), approximately 1.5 times less than that of curcumin (34.34 μg/mL). The total antioxidant capacity of the extract is equivalent to 132.48 ± 1.48 mg GA/g or 264.45 ± 2.34 μmol AS/g. The composition of Curculigo orchioides, including the total phenolic, total flavonoid, polysaccharides, and triterpenoid saponins, was examined by using the colorimetric method with reagents, and their quantity is equivalent to 196.24 ± 1.45 mg GAE/g, 78.49 ± 1.78 mg QE/g, 4.34 ± 0.08 %, 47.60 ± 0.24 mg Rb1/g (Rb1: Gypenoside III), respectively. Specifically, the total triterpenoid saponins content of Curculigo orchioides has been reported for the first time.
Fabrication and electrical characterization of lead-free BiFe0.91(Mn0.47Ti0.53)0.09O3–BaTiO3 ceramics
The (1-x)BiFe0.91(Mn0.47Ti0.53)0.09O3–xBaTiO3 (BFMT–BT) lead-free ceramics have been fabricated by the conventional solid-state reaction method. The phase structure of BFMT-BT investigated by X–ray diffraction shows a single perovskite phase. Although 20% mol of Bi2O3 was added to the raw materials, the evaporation of Bi3+ ions during calcining and sintering processes is from 20 to 30% wt. relative to other elements. The effect of BaTiO3content on electrical properties of BFMT-BT ceramic has been investigated. At BaTiO3concentration of 0.3 mol and the sintering temperature of 950oC, electrical properties of ceramics are best with the density (r) of 7.6 g/cm3, the electromechanical coupling factor (kp) of 0.28, the dielectric constant (εr) of 1028, and the difference in polarizations at zero field is about 10.5 mC/cm2.
Fabrication CdS/Au/TiO2 sandwich nanofibers for enhanced photoelectrochemical water-splitting efficiency
The sandwich-structured CdS/Au/TiO2 nanofibers (NFs) act as a photoanode in the photoelectrochemical cell (PEC) for hydrogen generation by splitting water. The gold nanoparticles sandwiched between the TiO2 nanofibers and the CdS quantum dots (QDs) layers play an important role in enhancing the solar-to-chemical-energy conversion efficiency. The structure and morphology of the materials were characterized by using field-emission scanning electron microscopy (FE–SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The surface plasmon resonance (SPR) of the Au nanoparticles was investigated by using ultraviolet-visible (UV–Vis) diffuse reflectance spectroscopy. The PEC properties of the photoanode were measured on a three-electrode electrochemical analyzer. The obtained photoconversion efficiency of the CdS/Au/TiO2 NFs is 4.1% under simulated-sunlight illumination with a 150 W xenon lamp. Working photoelectrode stability was tested, and the mechanism of the enhanced PEC performance was discussed.
Diversity of flowering plants in natural vegetation in Quang Tri province’s sand dune region
Species composition was determined from 455 random quadrats of size 100 m2. The survey results in 311 species belonging to 226 genera, 94 families, 59 orders, and 12 subclasses. The study adds 29 species, 20 genera, and 5 families to the flowering flora at the locality. The flowering flora endemic to Vietnam consists of 36 species, accounting for 11.57% of the total species. The dominant families include Cyperaceae (26 species), Poaceae (21 species), Rubiaceae (15 species), Asteraceae (14 species), Myrtaceae (11 species), Fabaceae (11 species), Phyllanthaceae (9 species), Apocynaceae (9 species), Lauraceae (8 species), Euphorbiaceae (8 species), and Verbenaceae (8 species). The life-form spectrum of flowering plants in the study area is 48.23 Ph + 4.18 Ch + 18.33 He + 9.97 Cr + 19.29 Th. The main geographical elements of this flora include Tropical Asia (18.01 %), Indo-China (16.40 %), and India (12.54 %). The natural vegetation exhibits high Simpson’s diversity index (0.915) and low Simpson’s evenness index (0.038).
Selection and culture condition optimisation for amylase biosynthesis of marine fungal strains isolated from Nha Trang Bay and Van Phong Bay, Khanh Hoa province
Marine fungi play an important role in marine ecosystems and provide numerous valuable industrial products. This study screens for amylase-producing marine fungi strains and studies the appropriate culture conditions to obtain enzymes. From 160 isolated strains, all yeast strains do not exhibit amylase activity (0/112 strains), while the molds display amylase activity with a high rate at 70.8% (34/48 strains). Among these molds, the DM12M strain has the highest amylase activity (13.0 U/mL). Suitable culture conditions for amylase production of this strain are the modified Czapek–Dox medium supplemented with 1% soluble starch, 0.3% NaNO3, 0.5% NaCl, and 5 days incubation at pH 6.0 and 30 °C. Under these conditions, the amylase activity of the DM12M strain reaches 59.0 U/mL, approximately 4.5 times higher than that under pre-optimalization conditions. The DM12M strain has the ITS1-5.8S-ITS2 nucleotide sequence of 99.8–100% similarity to the strains of Aspergillus aculeatus; this reveals that it may belong to this species. The research provides scientific data on the factors affecting the ability of the marine fungi to produce extracellular amylase and opens up their potential for industrial application.
Nature of bonding in Si2M clusters doped with monovalent metals (M = Li, Na, K, Cu, and Cr)
The density functional theory at the B3P86/6-311+G(d) level was used to study the geometric structures, stability, and chemical bonding of doped silicon clusters Si2M (M = Li, Na, K, Cu, and Cr). The results reveal that the most stable isomers of Si2M have isosceles triangle structure with the C2v symmetry, existing in two quasi-degenerate electronic states of A1 and B1 at the same spin multiplicity (doublet or quintet). The Si–M bonds are mainly formed via the electron transfer from the AO-s of M atoms to the Si2 moiety in the case of M being Li, Na, and K, while via the overlap between AO-s and AO-3d of Cu, Cr atoms and the MO-s of the Si2 moiety. The Si2Cr cluster is the most stable in the considered clusters.
Extraction of pectin from watermelon peels for pineapple and aloe vera jam fabrication
This study aims at the determination of the optimal parameters in the pectin extraction from watermelon peels, namely, pH, time, temperature, solvent, and material/water ratio. The results show that the highest pectin content is obtained by using nitric acid at pH 1.65; the precipitate solvent is isopropanol; the material/water ratio is 2.5:50 (g/mL); the temperature is 95 °C, and the time is 90 minutes. The appropriate pectin concentration to make gel in jam is 1.5%. The pectin extraction is simple, and therefore it can be applied to the production of pectin, pineapple jam, and aloe vera jam in the laboratory and industrial scales.
Diversity of terrestrial mollusks in Nam Dong, Thua Thien Hue
The survey and sampling the terrestrial gastropods were conducted in Nam Dong area, Thua Thien Hue province, from May 2018 to March 2019. A total of 39 species and subspe­cies belonging to 33 genera, 14 families of three subclasses (Neritimorpha, Caenogastropoda, and Heterobranchia) was recorded. The subclass Heterobranchia dominates with 25 species (64.10%). Among the sample, 13 species are first recorded in Thua Thien Hue area; 8 species are endemic to Central Vietnam, and 6 species are endemic to Vietnam. The abundant families include Cyclophoridae (8 species), Camaenidae (5 species), Streptaxidae (5 species), Pupinidae (4 species), and Achatinidae (4 species). Other families have 1 to 3 species.