Diatom and Diatomite: Different Focus on Natural Media to Material Science Path

Bio-silica issued from diatom, a microalgae, is attracted increasing attention in material science thanks to its peculiar nanoarchitecture and related properties with versatile applications. The present work is a deep analysis on morphological and chemical properties of bio-silica issued from fossil origin (diatomaceous earth) and living one (algal paste). An optimization in purification protocol was performed to obtain multiparous bio-silica from its raw media with keeping its original shape entirely. Multiple characterization methods as scanning electronic microscopy (SEM), infrared spectroscopy, x-ray diffraction (DRX), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), nitrogen adsorption and inverse gas chromatography (IGC), were used to check the purification protocol efficiency as well as to gather accurate information on morphology and chemical composition of diatom material obtained in large amount.

Lineaperpetua gen.nov.:a new diatom genus in the Thalassiosirales supported by morphology and molecular data

Based on a combination of morphology and molecular data of ribosomal DNA genes,a new diatom genus Lineaperpetua gen.nov.Yu,You,Kociolek&Wang is described.The features that help define Lineaperpetua at the level of genus include:a tangentially undulated valve face;continuous cribra areolae on the valve interior consisting of pores arranged as strips;single rimoportula located inside the ring of marginal fultoportulae.Additionally,phylogenetic analysis based on nuclear small subunit(SSU)rDNA sequences and nuclear large subunit(LSU)rDNA gene placed the three strains of L.lacustris in a single,monophyletic clade at a considerable sequence distance from the other genera(Thalassiosira,Conticribra,Planktoniella,Shinodiscus,and other genera)belonging to Thalassiosirales.Despite the similarities with some species of Thalassiosira,Conticribra,and Spicaticribra,the suite of features found in Lineaperpetua differentiate it from these other genera.These molecular data and morphological characters suggest an affinity of the new genus to the Thalassiosiraceae.

Yuzaoea gen. nov., a new biraphid diatom(Bacillariophyceae)genus and its phylogenetic significance

The flexed frustules in pennate diatoms are usually associated with monoraphid diatoms. Interestingly, we found a biraphid diatom species with flexed frustules in an offshore intertidal beach environment on Weizhou Island,Beihai City, Guangxi Zhuang Autonomous Region, China. Therefore, based on morphological characteristics, we described a new genus of diatoms Yuzaoea sinensis gen. et sp. nov. CH Li, HH Liu, YH Gao & CP Chen. The frustule of this genus is characterized by heterogeneous frustule with one concave valve and one convex valve,complete raphe on both valves, straight and moderately eccentric raphe, uniseriate striae and girdle bands with a single row of areolae. The most identifying feature of this genus was the flexed frustule, which is rare in biraphid diatoms and common in monoraphid diatoms. We compared the morphometric characteristics of genus Yuzaoea with genus Rhoikoneis and several genera within the family Rhoicospheniaceae, including Rhoicosphenia,Campylopyxis, and Cuneolus. Phylogenetic analyses based on SSU rRNA and rbc L showed that the genus Yuzaoea was the sister group to the clade of Rhoicosphenia with a high support value(bootstrap values = 100%), and the clade “Yuzaoea+Rhoicosphenia” was sister to the clade of monoraphid diatoms, in which the genera Achnanthidium, Planothidium and some Cocconeis with high support values(bootstrap = 100%).Morphologically, the genus Yuzaoea shares many morphological features with monoraphid diatoms like genera Achnanthidium and Planothidium and the members within the Rhoicospheniaceae. Therefore, based on a combined morphological studies and phylogenetic results we suggested that this branch may represented the evolution of one kind monoraphid diatoms, from biraphid diatoms(e.g. genus Yuzaoea), to incompleted biraphid diatoms(e.g. genera Rhoicosphenia, Campylopyxis), to monoraphid diatoms(e.g. genera Achnanthidium and Planothidium).

The Middle and Late Holocene climate change in Bohai Bay revealed by diatom proxy

A total of 98 samples from two boreholes in shallow sea area and two oyster reefs in adjacent coastal plain in the northwestern coast of Bohai Bay were collected for diatom analyses and species identification.The ratio of the marine species Thalassionema nitzschioides to the intertidal-coastal species complex Cyclotella striata/stylorum serves as a novel proxy for assessing the strength of marine influence.Chronological data,corrected for the local residence time effect,facilitated the construction of a diatom proxy-based marine influence curve for the study area.This curve delineates the dynamics of marine influence and their correlations with paleo-climate fluctuations and the East Asian monsoon variability,as well as their role in chenier formation.Results include:(1)eight periods of intensified marine influence have been documented since 7000 a BP in the study area.The peak of each period,as determined by the diatom proxy,corresponds closely to the warm climatic phases and stronger East Asian summer monsoons,suggesting that the peaks marine influence indicate typically the periods of climatic warmth and monsoon activity intensification in the region;(2)a strong correlation exists between the development of cheniers and marine influence,and chenier formation began with the increasing marine influence and terminated at the end of warm periods as marine influence weakens.The climatic changes in the coastal area,as indicated by the diatom proxy,hold significant potential for future related research endeavors.

Theoretical investigation of excited dipole bound states of alkali-containing diatomic anions

Information about electronic excited states of molecular anions plays an important role in investigating electron attachment and detachment processes.Here we present a high-level theoretical study of the electronic structures of 12 alkali-metal-containing diatomic anions MX-(MX = LiH,LiF,LiCl,NaF,NaCl,NaBr,RbCl,KCl,KBr,RbI,KI and CsI).The equation-of-motion electron-attachment coupled-cluster singles and doubles(EOM-EA-CCSD) method is used to calculate the electron binding energies(EBEs) of 10 electronic excited states of each of the 12 molecule anions.With addition of different s-/p-/d-type diffusion functions in the basis set,we have identified possible excited dipole bound states(DBSs) of each anion.With the investigation of EBEs on the 12 MXs with dipole moment(DM) up to 12.1 D,we evaluate the dependence of the number of anionic excited DBSs on molecular DM.The results indicate that there are at least two or three DBSs of anions with a molecular DM larger than 7 D and a molecule with DM > 10 D can sustain a π-DBS of the anion.Our study has some implications for the excited DBS electronic states of alkali-metal-containing diatomic molecules.

Diatoms as indicators of environmental change in coastal areas:a case study in Lianjiang coast of East China Sea

Owing to the significant differences in environmental characteristics and explanatory factors among estuarine and coastal regions,research on diatom transfer functions and database establishment remains incomplete.This study analysed diatoms in surface sediment samples and a sediment core from the Lianjiang coast of the East China Sea,together with environmental variables.Principal component analysis of the environmental variables showed that sea surface salinity(SSS)and sea surface temperature were the most important factors controlling hydrological conditions in the Lianjiang coastal area,whereas canonical correspondence analysis indicated that SSS and pH were the main environmental factors affecting diatom distribution.Based on the modern diatom species–environmental variable database,we developed a diatom-based SSS transfer function to quantitatively reconstruct the variability in SSS between 1984 and 2021 for sediment core HK3 from the Lianjiang coastal area.The agreement between the reconstructed SSS and instrument SSS data from 1984 to 2021 suggests that diatombased SSS reconstruction is reliable for studying past SSS variability in the Lianjiang coastal area.Three low SSS events in AD 2019,2013,and 1999,together with an increased relative concentration of freshwater diatom species and coarser sediment grain sizes,corresponded to two super-typhoon events and a catastrophic flooding event in Lianjiang County.Thus,a diatom-based SSS transfer function for reconstructing past SSS variability in the estuarine and coastal areas of the East China Sea can be further used to reflect the paleoenvironmental events in this region.

The Expression Characteristics and Potential Functions of Heat Shock Factors in Diatom Phaeodactylum tricornutum

Heat shock transcription factor(HSF)are essential regulators of heat shock protein(HSP)gene expression in plants and algae,contributing to their resilience against biotic and abiotic stresses.However,the localization,structure,phylogenetic relationship,and characteristics of PtHSF genes in microalgae,especially in diatom Phaeodactylum tricornutum,remain largely unexplored.This study presents a comprehensive analysis of the PtHSF gene family in P.tricornutum.A genome-wide analysis identified 68 PtHSF genes,which were classified into two distinct subfamilies:traditional and untraditional.Motif and structure analyses revealed evidence of multiple duplication events within the PtHSF gene family.Expression profiling revealed diurnal patterns,with 34 genes being downregulated during the light period and upregulated during the dark period,while 19 genes exhibited the opposite pattern.These findings suggest that PtHSF genes may have specialized functions during the diurnal cycle and play a crucial role in maintaining cellular homeostasis in response to various stresses.Notably,PtHSF16,30,and 43 genes exhibited higher expression levels,suggesting their potential importance.This study provides a valuable foundation for future investigations into the specific functions of HSFs under different stress conditions and their regulatory mechanisms in P.tricornutum and other microalgae.

Ni-Ag双原子团簇催化甲烷干法重整反应的理论研究

甲烷干重整制合成气是将温室气体转换为合成气的有效途径,兼具环境效益和经济效益.本文采用密度泛函理论方法对Ni-Ag双原子团簇催化甲烷干重整反应的体系进行理论研究,对势能面上各驻点进行了全几何参数优化,通过频率分析确认了过渡态,并通过内禀反应坐标方法进行了验证,得出各基元反应的能量最低路径.研究结果对于理解在Ni上引入第二种金属Ag形成双原子团簇催化甲烷干法重整的理论研究有一定的意义,并为下一步实验研究提供理论基础.

Pigment signatures of some diatoms isolated from China seas

The photosynthetic pigments of 12 species （14 strains） of cultured diatoms from six genera under specific conditions were examined by the HPLC. The diatom genera were Skeletonema, Thalassiosira, Chaetoceros, Nitzschla, Phaeodactylum and Meuniera. All strains were isolated from China seas and most of them were from the Jiaozhou Bay, China. Fifteen pigments were identified and eight of them were various chlorophyll a derivatives. Chlorophyll a, c2 and c1 and the carotenoids fucoxanthin, diadinoxanthin, diatoxanthin and β, β-carotene existed in all species. The ratios of each pigment to chlorophyll a were compared with the results in literatures. The pigment ratios of this study generally fall within the ranges reported by the literatures although the maximum ratio of fucoxanthin to chlorophyll a was higher and the ratios of chlorophyll c and diatoxanthin to chlorophyll a were low. The pigment ratios are useful to understanding the pigment signatures of diatoms in the Jiaozhou Bay, China, and to setting up the chemotaxonomic method of phytoplankton in these sea areas.

Biomass,species composition and diversity of benthic diatoms in mangroves of the Houyu Bay,China

The biomass, species composition and diversity of benthic diatom assemblages in mud-flat soils in Kandelia candel (L.) Druce communities with and without vegetation were studied seasonally at the Houyu Bay in Fuding City, Fujian Province, China. A total of 103 taxa were identified (including varieties). Eighty-four taxa were found in the mud-flat with vegetation and 74 taxa in the mud-flat without vegetation, while the biomass was large in January and April and decreased from July to October. The most abundant species in the mud-flat with vegetation are Nitzschia cocconeiformis, Gyrosigma scalproides and N. fasciculata, compared with G. scalproides and N. obtusa var. scalpelliformis in the mud-flat without vegetation. High H' values at 2 sites during all seasons suggest that diatom assemblages in the sediments of the Houyu Bay represent an original environment. Multi-dimensional scaling of diatom assemblages from mud-flats with and without vegetation shows that a slight seasonal change and only a single association occur in the mangroves.

STUDIES ON CULTURE CONDITIONS OF BENTHIC DIATOMS FOR FEEDING ABALONE Ⅲ. EFFECTS OF IRON AND SILICON NUTRIENTS AND OF ORTHOGONAL COMBINATIONS OF NITROGEN,PHOSPHORUS,IRON AND SILICON ON GROWTH RATE

Effects of iron and silicon nutrients and of orthogonal combinations of nitrogen, phosphorus, iron and silicon on the growth rate of three benthic diatoms were studied by using an in situ OD measurement method. The results of monofactor tests of ironand silicon shawed that Fe-EDTA was bettef than ferric citrate in the culture of these diatoms;that the favourable concentration of Fe-EDTA was about 0.5 mg/L of Fe and that of silicate was 2.5 mg/L of Si or more.The orthogonal test showed that the optimal concentration ratios(mg/L)of nitrogen, phosphorus, iron and silicon were: 5. 0: 0. 25: 0.5: 2. 0 for Cocconeis scutellum var. parva; 2.5: 1.0: 1.0: 2.0 for Amphora coffeaeformis; and 5.0: 0. 15: 0.5: 2.0 for N. mollis.

Photoinduced toxicity single and binary mixtures of four polycyclic aromatic hydrocarbons to the marine diatom Skeletonema costatum

Diatom Skeletonema costatum Cleve is one of the main predominant phytoplankton species in the Changjiang Estuary in China. In order to provide some basic information for future assessment of the potential risk on phytoplankton communities in this estuary caused by polycyclic aromatic hydrocarbons（ PAHs）, this alga was selected as a representative to investigate the photoinduced toxicity of PAHs, in single and mixture. Four PAHs including three-ring phenanthrene and anthracene, four-ring fluoranthene and pyrene were tested in the laboratory. The single toxicity of each PAH on this microalga was compared with and without the simulated solar UV radiation. The results showed that this microalga was sensitive to PAH＇ s photoinduced toxicity. Ratios of the 72 h median effect concentration obtained for fluorescent and UV light tests were about 8.4 for phenanthrene, 13.0 for anthracene, 6. 5 for fluoranthene, and 5.7 for pyrene, indicating that UV light enhanced the PAH toxicity to this alga significantly. Under the fluorescent radiation （lacking UV ）, the dose-response curves based on chemical concentrations revealed that the order of toxic strength was fluoranthene greater than pyrene greater than anthracene greater than phenanthrene; while under the UV radiation （476 μW/cm^2 for UVA, 6.5 μW/cm^2 for UVB） it became fluoranthene approximately equaling anthracene greater than pyrene greater than phenanthrene, indicating that the UV light also changed its relative toxicity to this alga. The photoinduced toxicity of PAHs to the marine diatom S. costatum might be a synergistic effect of photosensitization reactions （ e. g. , generation of singlestate oxygen） and photomodification （photooxidation and/or photolysis）. The combined effects of six binary mixtures on the marine diatom S. costatum were investigated using the additive-index method. Four binary-mixtures （ phenanthrene plus anthracene ; phenanthrene plus pyrene ; anthracene plus fluoranthene ; anthracene plus pyrene） were found to be synergistic joint action mode, while two binary-mixtures （phenanthrene plus fluoranthene; fluoranthene plus pyrene） displayed antagonist, revealing a complex pattern of possible interactions. The combined action mode of PAHs might be related to various factors such as the mixture compounds, mixture ratios and test conditions, etc.

Toxic effects of fluoranthene and copper on marine diatom Phaeodactylum tricornutum

To investigate the effects of polycyclic aromatic hydrocarbons (PAHs) and metals on the population reproduction,antioxidative defense system and cell ultrastructure of the marine diatom,fluoranthene and Cu2+ were selected to test their toxicity to Phaeodactylum tricorntum,in the laboratory.The results indicated that both fluoranthene and Cu2+ inhibited population reproduction of P.tricorntum.When the algal cells were exposed to fluoranthene or Cu2+ for 72 h,ultrastructure damage in the cells was observed un...

The environmental implication of diatom fossils in the surface sediment of the Changjiang River estuary(CRE) and its adjacent area

In order to depict the distribution of diatom fossils in surface sediments and to establish a reliable reference data for further paleoenvironmental study in the Changjiang (Yangtze) River estuary and its adjacent waters, the diatom fossils from 34 surface sediment samples and their relationship with environmental variables were analyzed by principal component analysis and redundancy correspondence analysis. The diversity and abundance of diatom fossils were analyzed. Some annual average parameters of the overlying water (salinity, temperature, turbidity, dissolved oxygen, depth, dissolved inorganic nitrogen, dissolved inorganic phosphate and dissolved inorganic silicate) were measured at each sampling site. A total of 113 diatom taxa and one silicoflagellate species were identified in the investigation area. Diatom fossils were better preserved in fine sediments. The absolute abundance of diatom fossils did not significantly diff er between inshore and off shore areas, the species diversity decreased from inshore to off shore. This may be because high nutrients and low salinity promoted the growth of more brackish species in coastal waters. The diatom taxa were divided into three groups, on the basis of their response and indication to environmental changes. For example, Actinocyclus ehrenbergii and Cyclotella stylorum were dominant in coastal waters (Group 1 and Group 3) with high nutrients and low salinity;the relative abundances of Paralia sulcata and Podosira stelliger were significantly higher in off shore sites (Group 2, average 39.5%), which were characterized by high salinity and deep water. Four environmental variables (salinity, dissolved inorganic nitrogen, temperature and water depth) explained the composition and distribution of diatom taxa independently ( P< 0.05), this finding can be applied in further paleoenvironmental reconstruction research in this area.

DIATOM COMMUNITY SUCCESSION AND NUTRIENT EVOLUTION RECORDED FROM A SEDIMENT CORE OF THE LONGGAN LAKE, A LARGE SHALLOW LAKE IN EAST CHINA

The Longgan Lake is a shallow mesotrophic macrophyte-dominated lake. According to the high-resolution diatom research from its sediment core, the diatom community succession was built, and the total phosphorus (TP) and chlorophyll-a (Chl-a) concentration were quantitatively reconstructed for the past 2000 years, based on the diatom-TP and diatom-Chla transfer functions. The shifts of diatom assemblages also mirrored the developments of aquatic plant, reflecting the characters of aquatic ecosystem evolution. The inferred epilimnetic TP concentration fluctuated within a small range of 36 to 62μg/L, indicating the lake remained a relative stable mesotrophic status in the long historical period. The periodical variations of the diatom assemblage and trophic status suggest a mitigating function of shallow macrophyte-dominated lakes to nutrient input. The changes of lakes’ trophic status don’t linearly respond to the human disturbance in the catchment. The dynamics mechanism of phosphorus in macrophyte-dominated lakes, as inferred from diatoms, will provide a scientific foundation for the prediction of trophic status change in a shallow lake, as well as the lake ecological restoration and management decisions.

Rotation and vibration of diatomic molecule oscillator with hyperbolic potential function

The explicit expressions of energy eigenvalues and eigenfunctions of bound states for a three-dimensional diatomic molecule oscillator with a hyperbolic potential function are obtained approximately by means of the hypergeometric series method. Then for a one-dimensional system, the rigorous solutions of bound states are solved with a similar method. The eigenfunctions of a one-dimensional diatomic molecule oscillator, expressed in terms of the Jacobi polynomial, are employed as an orthonormal basis set, and the analytic expressions of matrix elements for position and momentum operators are given in a closed form.

Late Quaternary diatom and sea level changes in estuarine plain of the Jiulong River

Four units and twenty-four zones of diatom have been discerned in the Borehole ZK5 in the estuarine plain of the Jiulong River, Fujian Province. Comprehensive analysis of these, together with microbiological assemblages and age determinations in some other boreholes, shows that during the Late Wurm Glacial, sea level of the study area rose and fell frequently, but had principally been in the environments of estuary-bay. This mainly resulted from the tectonic subouction. In this period 3 low sea levels occurred. at 18, 16 and 12 kaBP respectively. During Holocene, sea weter intruded massively and the sea level over the transgnaion maximum had been 5-10 m higher than that of the present.

Nonsequential double ionization of nonaligned diatomic molecules N_2 and O_2

Nonsequential double ionization （NSDI） processes of nonaligned diatomic molecules N2 and O2 are studied using the S-matrix theory. Our results show that the NSDI process significantly depends on the molecular symmetry and structure. The ratio of NSDI rate to single ionization rate as a function of the field intensity is obtained. It is found that N2 behaves closely with its companion atom Ar in the ratios over the entire intensity range, while O2 exhibits an obvious suppression effect, which is qualitatively consistent with the experiment.

Morphology and molecular phylogeny of Pleurosira nanjiensis sp. nov., a new marine benthic diatom from the Nanji Islands, China

A new marine benthic diatom, Pleurosira nanjiensis sp. nov., is described from the rocky intertidal zone of the Xiaochaiyu Island of the Nanji Islands in China. Its morphology was examined with light and scanning electron microscopy. Molecular phylogeny was reconstructed based on SSU rRNA and rbcL gene sequences. Pleurosira nanjiensis differs from congeners in possession of a combination of morphological features including the domed valve with broadly lanceolate, elliptical or circular valve outline, two elevated marginal ocelli, two （rarely three） rimportulae, and radiate striae.

Preparation and hygrothermal performance of composite phase change material wallboard with humidity control based on expanded perlite/diatomite/paraffin

Phase change material(PCM)can reduce the indoor temperature fluctuation and humidity control material can adjust relative humidity used in buildings.In this study,a kind of composite phase change material particles(CPCMPs)were prepared by vacuum impregnation method with expanded perlite(EP)as supporting material and paraffin as phase change material.Thus,a PCM plate was fabricated by mould pressing method with CPCMPs and then composite phase change humidity control wallboard(CPCHCW)was prepared by spraying the diatom mud on the surface of PCM plate.The composition,thermophysical properties and microstructure were characterized using X-ray diffraction instrument(XRD),differential scanning calorimeter(DSC)and scanning electron microscope(SEM).Additionally,the hygrothermal performance of CPCHCW was characterized by temperature and humidity collaborative test.The results can be summarized as follows:(1)CPCMPs have suitable phase change parameters with melting/freezing point of 18.23°C/29.42°C and higher latent heat of 54.66 J/g/55.63 J/g;(2)the diatom mud can control the humidity of confined space with a certain volume;(3)the combination of diatom mud and PCM plate in CPCHCW can effectively adjust the indoor temperature and humidity.The above conclusions indicate the potential of CPCHCW in the application of building energy efficiency.