Temporal and spatial distribution of biogenic silica and its significance in the Wuliangsuhai Lake and Daihai Lake

In this work, the concentrations, temporal and spatial distributions and the relationship between biogenic silica (BSi) and primary productivity are discussed on the basis of the geochemistry character of BSi in the water–sediment system of the Wuliangsuhai Lake and Daihai Lake. The results show that the average concentrations of SiO₃^2- and BSi are 3.0 mg/L and 3.5 mg/g in the overlying water and sediments from the Wuliangsuhai Lake, respectively, while they are 1.0 mg/L and 7.5 mg/g, respectively, in the Daihai Lake. It is the uptake and assimilation of diatom phytoplankton which results in the significant difference of the SiO₃^2- concentrations between the two lakes, and the inputs of surface runoff is one of the important factors in impacting the spatial distributions of SiO₃^2- in the overlying water. The spatial distributions of BSi suggest the Si source of the two lakes and indicate the differences of eutrophication types and ancient primary producer between the two lakes. The eutrophication precesses and ancient primary productivity of diatom phytoplankton are reconstructed by applying the geochemistry information of BSi archived in the vertical concentration profiles in the two lake sediments. The geochemistry information of BSi well responds to the paleoenvironment and paleoclimate of the Daihai drainage basin indicating silicate limitation of primary productivity by diatoms phytoplankton in the Daihai Lake.     

Mono- and sesquiterpenoids from Hydrocotyle and Centella species

Hydrocotyle sibthorpioides, H. maritima and Centella asiatica were investigated for their ter- penoid constituents. The major component of H. sibthorpioides and H. maritima is trans- β-farnesene. The latter species also elaborates α-terpinene and thymol methyl ether in respectable amount. The sesquiterpenoid constitution of C. asiatica is rather similar to H. maritima. Possible allelopathy between H. sibthorpioides and a liverwort is suggested.     

The mechanisms and process of acephate degradation by hydroxyl radical and hydrated electron

The degradation process of acephate in aqueous solution with OH and ${\text{e}}_{\text{aq}}^{?}$ produced by ⁶⁰Co-γ irradiation and electron pulse radiolysis was studied in the present paper. In the aqueous solution, acephate reacted with ${\text{e}}_{\text{aq}}^{?}$ and transformed to transient species which can absorb weakly in the wavelength range of 300–400?nm and decay very fast. According to the decay of hydrated electron, the reaction rate constant of ${\text{e}}_{\text{aq}}^{?}$ and acephate is (3.51?±?0.076)?×?10⁹?dm³·mol^?1·s^?1. The transient species produced in the reaction of OH and acephate do not distinctly absorb the light in the wavelength range of 300–700?nm, so the decay and kinetics of the transient species cannot determinedirectly. The competing reaction of KSCN oracephate with OH were studied to obtain the reaction rate constant of OH and acephate, which is (9.1?±?0.11)?×?10⁸?dm³·mol^?1·s^?1. Although acetylamide and inorganic ions were determined in the products of the reaction of acephate with OH or ${\text{e}}_{\text{aq}}^{?}$, the concentration of inorganic ions in the products of the reaction of acephate with OH is higher than that in the product of the reaction of acephate with ${\text{e}}_{\text{aq}}^{?}$. Moreover, there were sulfide in the products of the reaction of acephatewith ${\text{e}}_{\text{aq}}^{?}$. The degradation pathways of acephate by OH and ${\text{e}}_{\text{aq}}^{?}$ were also proposed based on the products from GC-MS.     

NMR and FT-IR conformational studies of 8-substituted guanine nucleosides and nucleotides and their metal adducts and cancer

NMR and FT-IR Studies of the conformational changes of guanosine and guanosine-5′-monophosphate upon substitution of the H8 of guanine by a heavy, large atom, such as bromine, are presented. The conformational forms, syn, anti, C2′-endo and C3′-endo and gg, gt and tg rotamers of the above molecules are compared to those of their metal (Mg²⁺ and P^t2+) adducts, where the metal is fixed to the N7 nitrogen atom of guanine. The antitumor activity of cisplatin is discussed with relation to the conformational form and the effect of cisplatin is compared to the effects of the Mg²⁺ ion and carcinogens.     

Growth promoting and inhibiting effects of extracellular substances of soil microalgae and cyanobacteria on Escherichia coll and Micrococcus luteus

Different taxa of chlorophycean, trebouxiophycean and xanthophycean soil microalgae and of cyanobacteria have been tested for the release of substances that inhibit the growth of either Echerichia coli (Migula) Castellani et Chalmersor Micrococcus luteus (Schroeter) Cohn. Experiments suggest two types of antibacterial effects: one type is constitutive; that is, the antibacterial activity is always present in the algal culture medium, as is the case with the Chroococcus turgidus (medium that inhibits the growth of Escherichia coli). The other type is induced; that is, the antibacterial activity occurs only when algae are in contact with bacteria. This is the case when growth of Micrococcus luteus is inhibited in co‐culture with Chroococcus turgidus (Kützing) Nägeli or with Xanthonema debile (Vischer) Silva and when growth of Escherichia coll is inhibited in co‐culture with Tetracystis sp. As well as inhibition, promotion of bacterial growth was observed. This was probably an unspecific effect resulting from soluble organic and inorganic substances, such as carbohydrates, that are generally present in algal cultures.     

Sulfide Tolerance and Detoxification in Arenicola marina and Sipunculus nudus

SYNOPSIS. The lugworm Arenicola marina and the peanut worm Sipunculusnudus both inhabit intertidal flats. Sulfide concentrationsin the pore water of the sediment can be as high as 340 µMin the habitat of A. marina. Sulfide levels in the burrow waterand in the coelomic fluid increase during low tide. In contrast,S. nudus is only rarely exposed to sulfide. Neither A. marinanor S. nudus is able to exclude sulfide completely from itsbody. However, both worms accumulate only 15 to 40% respectivelyof the external sulfide concentration during hypoxic 1 mM sulfideincubations. During normoxia, sulfide accumulation is more thanten-fold lower than under hypoxic conditions in both species.When oxygen is available, sulfide is oxidized to thiosulfate.The oxidation rate is about 5 times higher in A. marina thanin S. nudus. A major component of sulfide oxidation is due tothe mitochondria of both species. Mitochondrial sulfide oxidationin the tissues of A. marina is insensitive to low cyanide andto high sulfide concentrations, but can be inhibited by salicylhydroxamicacid. The existence of an alternative terminal oxidase is suggested.When the sulfide level in the body of A. marina and S. nudusincreases above a toxic level, both species survive by switchingto an anaerobic metabolism.     

A theoretical and experimental analysis of the qP and qN coefficients of chlorophyll fluorescence quenching and their relation to photochemical and nonphotochemical events

The initial (F₀), maximal (F_M) and steady-state (F_S) levels of chlorophyll fluorescence emitted by intact pea leaves exposed to various light intensities and environmental conditions, were measured with a modulated fluorescence technique and were analysed in the context of a theory for the energy fluxes within the photochemical apparatus of photosynthesis. The theoretically derived expressions of the fluorescence signals contain only three terms, X=J₂p_2F/(1–G), Y=T/(1–G) and V, where V is the relative variable fluorescence, J₂ is the light absorption flux in PS II, p_2F is the probability of fluorescence from PS II, G and T are, respectively, the probabilities for energy transfer between PS II units and for energy cycling between the reaction center and the chlorophyll pool: F₀=X, F_M=X/(1–Y) and F_S=X(1+(YV/(1–Y))). It is demonstrated that the amplitudes of the previously defined coefficients of chlorophyll fluorescence quenching, q_P and q_N, reflect, not just photochemical (q_P) or nonphotochemical (q_N) events as implied in the definitions, but both photochemical and nonphotochemical processes of PS II deactivation. The coefficient q_P is a measure of the ratio between the actual macroscopic quantum yield of photochemistry in PS II (41-1) in a given light state and its maximal value measured when all PS II traps are open (41-2) in that state, with 41-3 and 41-4. When the partial connection between PS II units is taken into consideration, 1-q_P is nonlinearily related to the fraction of closed reaction centers and is dependent on the rate constants of all (photochemical as well as nonphotochemical) exciton-consuming processes in PS II. On the other hand, 1-q_N equals the (normalized) ratio of the rate constant of photochemistry (k_2b) to the combined rate constant (k_N) of all the nonphotochemical deactivation processes excluding the rate constant k₂₂ of energy transfer between PS II units. It is demonstrated that additional (qualitative) information on the individual rate constants, k_N-k₂₂ and k_2b, is provided by the fluorescence ratios 1/F_M and (1/F₀)–(1/F_M), respectively. Although, in theory, 41-5 is determined by the value of both k_2b and k_N-k₂₂, experimental results presented in this paper show that, under various environmental conditions, 41-6 is modulated largely through changes in k _N, confirming the idea that PS II quantum efficiency is dynamically regulated in vivo by nonphotochemical energy dissipation.Abbreviations Chl chlorophyll - F₀, F_M and F_S initial, maximal and steady-state levels of modulated Chl fluorescence emitted by light-adapted leaves - PS I and II photosystem I and II - q_P and q_N (previously defined) photochemical and nonphotochemical components of Chl fluorescence quenching     

Microsomal and photochemical oxidation and reduction of 1-piperidinoanthraquinone

In microsomes of control Wistar rats, the NADPH-dependent reduction of 1-piperidinoanthraquinone (1-PA) to the corresponding hydroquinone, in the absence of oxygen, has been observed. Two facts ((i) inhibition of the formation of 1-piperidinoanthrahydroquinone (1-PAH) by metyrapone and antibodies to cytochrome P-450, and (ii) increase in the rate of 1-PAH formation upon induction of rats by phenobarbital) indicate that cytochrome P-450 participates in the reduction of 1-PA. Since 1-PA is a substrate of cytochrome P-450 and is oxidized in microsomes to (N-anthraquinonyl-1)-δ-aminovaleric acid (AAV), model experiments have been conducted to examine whether the reduced forms of 1-PA are involved in its oxidation. During photochemical generation of 1-PAH and its subsequent oxidation (N-anthraquinonyl-1)-β-aminovaleric aldehyde (AAVal) is formed. However, this product is formed without participation of activated forms of the substrate and oxygen. AAVal) is formed. However, photochemical systems, apparently, is a precursor of AAV in microsomal oxidation of 1-PA. AAVal is a substrate of cytochrome P-450 (the Type I of binding) and is oxidized quantitatively in microsomal systems to yield AAV. The data obtained enable us to propose a possible mechanism of enzyme oxidation of 1-PA.     

Plato and Peirce on Likeness and Semblance

In his well-known essay, ??What Is a Sign???(CP 2.281, 285) Peirce uses ??likeness?? and ??resemblance?? interchangeably in his definition of icon. The synonymity of the two words has rarely, if ever, been questioned. Curiously, a locus classicus of the pair, at least in F. M. Cornford??s English translation, can be found in a late dialogue of Plato, namely, the Sophist. In this dialogue on the myth and truth of the sophists?? profession, the mysterious ??stranger??, who is most likely Socrates?? persona, makes the famous distinction between eikon (likeness) and phantasma (semblance) (236a,b). For all his broad knowledge in ancient philosophy, Peirce never mentioned this parallel; nor has any Peircean scholar identified it. There seems to be little problem with eikon as likeness, but phantasma may give rise to a puzzle which this paper will attempt to solve. Plato uses two pairs of words: what eikon is to phantasma is eikastikén (the making of likeness [235d]) to phantastikén (semblance making [236c]). In other words, icons come into being because of the act of icon-making, which is none other than indexicality. Witness what Peirce says about the relationship between photographs and the objects they represent: ??But this resemblance is due to the photographs having been produced under such circumstances that they were physically forced to correspond point by point to nature.?? (Ibid.) Thus the iconicity which links the representamen (sign) and its object is made possible not only by an interpretant, but also by idexisation. Their possible etymological and epistemological links aside, the Peircean example of photographing and the Platonic discussion of painting and sculpturing in the Sophist, clearly show the physio-pragmatic aspect of iconicity. The paper will therefore reread the Peircean iconicity by closely analysing this relatively obscure Platonic text, and by so doing restore to the text its hidden semiotic dimension.     

Techno-economical study of ethanol and biogas from spruce wood by NMMO-pretreatment and rapid fermentation and digestion

Given that N-methylmorpholine-N-oxide (NMMO) is a promising alternative for the pretreatment of lignocelluloses, a novel process for ethanol and biogas production from wood was developed. The solvent, NMMO, is concentrated by multistage evaporation, and the wood is pretreated with the concentrated NMMO. Thereafter, ethanol is produced by the non-isothermal simultaneous saccharification and fermentation (NSSF) method, which is a rapid and efficient process. The wastewater is treated by upflow anaerobic sludge blanket (UASB) digester for rapid production of biogas. The process was simulated by Aspen plus®. Using mechanical vapor recompression for evaporators in the pretreatment and multi-pressure distillation columns, the energy requirements for the process were minimized. The economical feasibility of the developed biorefinery for five different plant capacities was studied by Aspen Icarus Process Evaluator. The base case was designed to utilize 200,000 tons of spruce wood per year and required M€ 58.3 as the total capital investment, while the production cost of ethanol is calculated to be €/l 0.44.     

Distribution and some properties of NADPH and NADH oxidase in parenchymal and nonparenchymal liver cells

The activities of NADPH and NADH oxidase were determined in homogenates of isolated pure parenchymal and nonparenchymal rat liver cells at neutral (7.4) and acid (5.5) pH. The NADPH oxidase at pH 7.4 is about equally active in parenchymal and nonparenchymal cells and in both cell types is rather insensitive to KCN (1 mm) inhibition. By lowering the pH to 5.5, the NADPH oxidase of the nonparenchymal cells is stimulated (twofold) while the activity in parenchymal cells is decreased. The NADH consumption at neutral pH in parenchymal cells is 75% inhibited by KCN, while this activity in nonparenchymal cells is relatively insensitive to KCN. The NADH oxidase in both parenchymal and nonparenchymal liver cells is less active when the pH is lowered from 7.4 to 5.5. The distribution of NAD(P)H oxidases between parenchymal and nonparenchymal liver cells and the effect of pH on their activities suggest that in the nonparenchymal cells, the NADPH oxidase might play a role in the synthesis of H₂O₂ within the phagocytic vacuole. A scheme is proposed which describes the metabolic events involved in H₂O₂ formation and catabolism of endo(phago)cytosed particles in nonparenchymal liver cells.     

Pre- and perinatal brain development and enculturation

Ample evidence from various quarters indicates that the perceptual-cognitive competence of the pre- and perinatal human being is significantly greater than was once thought. Some of the evidence of this emerging picture of early competence is reviewed, and its importance both as evidence of the biogenetic structural concept of “neurognosis” and for a theory of enculturation is discussed. The literature of pre- and perinatal psychology, especially that of developmental neuropsychology, psychobiology, and social psychophysiology, is incorporated, and some of the implications of these data for a theory of enculturation are suggested. This paper was presented at the annual meeting of the American Anthropological Association, Washington, D.C., November 1989. Charles D. Laughlin, Professor of Anthropology at Carleton University, Ottawa, Canada, has done ethnographic fieldwork among the So of northeastern Uganda and among Tibetan lamas in Nepal and India. He completed postdoctoral studies in neurophysiology at the Institute of Neurological Sciences, University of Pennsylvania. He is editor of both theNeuroanthropology Network Newsletter and thePre- and Peri-Natal Psychology Journal.     

Peptide and glycopeptide dendrimers and analogous dendrimeric structures and their biomedical applications

The size of information that can be stored in nucleic acids, proteins, and carbohydrates was calculated. The number of hexamers for peptides is 64,000,000 (20⁶) and seems to be impressive in comparison with 4,096 (4⁶) hexanucleotides, but the number of isomers of hexasaccharides is 1.44 × 10¹⁵. Carbohydrates are therefore the best high-density coding system. This language has been named glycocode resp. sugar code. In comparison with peptide dendrimers, the amount of information carried by glycopeptide dendrimers or glycodendrimers is therefore much higher. This is reflected by the variability of structures and functions (activities). This review is about the broad area of peptide and glycopeptide dendrimers. The dendrimeric state and physicochemical properties and general consequences are described, together with a cluster effect. The impact of cluster effect to biological, chemical, and physical properties is discussed. Synthesis of dendrimers by convergent and divergent approaches, “Lego” chemistry, ligation strategies, and click chemistry is given with many examples. Purification and characterization of dendrimers by chromatographic methods, electromigration methods, and mass spectrometry are briefly mentioned. Different types of dendrimers with cyclic core, i.e. RAFTs, TASPs and analogous cyclic structures, carbopeptides, carboproteins, octopus glycosides, inositol-based dendrimers, cyclodextrins, calix[4]arenes, resorcarenes, cavitands, and porphyrins are given. Dendrimers can be used for creation of libraries, catalysts, and solubilizing agents. Biocompatibility and toxicity of dendrimers is discussed, as well as their applications in nanoscience, nanotechnology, drug delivery, and gene delivery. Carbohydrate interactions of glycopeptide dendrimers (bacteria, viruses, and cancer) are described. Examples of dendrimers as anti-prion agents are given. Dendrimers represent a fast developing area which partly overlaps with nanoparticles and nanotechnologies.