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  • General Chemistry  (29)
  • Life and Medical Sciences  (8)
  • Microbial biomass  (5)
  • ASTROPHYSICS
  • 1995-1999  (43)
  • 1
    Electronic Resource
    Electronic Resource
    Ergosterol and microbial biomass relationship in soil (1996)
    Springer
    Biology and fertility of soils 22 (1996), S. 299-304 
    Details
    ISSN: 1432-0789
    Keywords: Microbial biomass ; Fungal biomass ; Ergosterol ; Fumigation extraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Ergosterol and microbial biomass C were measured in 26 arable, 16 grassland and 30 forest soils. The ergosterol content ranged from 0.75 to 12.94 μg g-1 soil. The geometric mean ergosterol content of grassland and forest soils was around 5.5 μg g-1, that of the arable soils 2.14 μg g-1. The ergosterol was significantly correlated with biomass C in the entire group of soils, but not in the subgroups of grassland and forest soils. The geometric mean of the ergosterol: microbial biomass C ratio was 6.0 mg g-1, increasing in the order grassland (5.1), arable land (5.4) and woodland (7.2). The ergosterol:microbial biomass C ratio had a strong negative relationship with the decreasing cation exchange capacity and soil pH, indicating that the fungal part of the total microbial biomass in soils increased when the buffer capacity decreased. The average ergosterol concentration calculated from literature data was 5.1 mg g-1 fungal dry weight. Assuming that fungi contain 46% C, the conversion factor from micrograms ergosterol to micrograms fungal biomass C is 90. For soil samples, neither saponification of the extract nor the more effective direct saponification during extraction seems to be really necessary.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00334573
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  • 2
    Electronic Resource
    Electronic Resource
    The problem of pretreatment and unintentional variations in the fumigation-extraction method for time-course measurements in the field (1996)
    Springer
    Biology and fertility of soils 22 (1996), S. 167-170 
    Details
    ISSN: 1432-0789
    Keywords: Analytical variations ; Root intenference ; Root pre-extraction ; Fumigation-extraction ; Microbial biomass
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A control soil stored at 4°C was analyzed 38 times by fumigation-extraction during a period of 11 months to correct for variations caused by the analytical procedure. The difference in extractable C between fumigated and unfumigated samples oscillated around the average without a positive or negative trend. When data from contemporaneously extracted field samples were corrected with control soil data the variations were lowered. The deviations between corrected and uncorrected biomass C values had maxima of ±12%. Data obtained for seven dates using pre-extraction, wet-sieving, and centrifuging were compared with data obtained by the conventional procedure without any pretreatment. A negative difference from data obtained without pretreatment was found when the soil water content was decreased to 6%. The largest positive difference (+38%) was found in May during the period of highest root growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00384450
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  • 3
    Electronic Resource
    Electronic Resource
    Microbial biomass phosphorus in soils of beech (Fagus sylvatica L.) forests (1995)
    Springer
    Biology and fertility of soils 19 (1995), S. 215-219 
    Details
    ISSN: 1432-0789
    Keywords: Microbial biomass ; Acidification ; Beech forest ; Soil organic C ; Total P ; Fagus sylvatica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Thirty-eight soils from forest sites in central Germany dominated by beech trees (Fagus sylvatica L.) were sampled to a depth of about 10 cm after careful removal of the overlying organic layers. Microbial biomass P was estimated by the fumigation — extraction method, measuring the increase in NaHCO3-extractable phosphate. The size of the microbial P pool varied between 17.7 and 174.3 μg P g-1 soil and was on average more than seven times larger than NaHCO3-extractable phosphate. Microbial P was positively correlated with soil organic C and total P, reflecting the importance of soil organic matter as a P source. The mean microbial P concentration was 13.1% of total P, varying in most soils between 6 and 18. Microbial P and microbial C were significantly correlated with each other and had a mean ratio of 14.3. A wide (5.1–26.3) microbial C: P ratio indicates that there is no simple relatinship between these two parameters. The microbial C: P ratio showed strong and positive correlations with soil pH and cation exchange capacity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336162
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  • 4
    Electronic Resource
    Electronic Resource
    The problem of pretreatment and unintentional variations in the fumigation-extraction method for time-course measurements in the field (1996)
    Springer
    Biology and fertility of soils 22 (1996), S. 167-170 
    Details
    ISSN: 1432-0789
    Keywords: Key words Analytical variations ; Root interference ; Root pre-extraction ; Fumigation-extraction ; Microbial biomass
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A control soil stored at 4°C was analyzed 38 times by fumigation-extraction during a period of 11 months to correct for variations caused by the analytical procedure. The difference in extractable C between fumigated and unfumigated samples oscillated around the average without a positive or negative trend. When data from contemporaneously extracted field samples were corrected with control soil data the variations were lowered. The deviations between corrected and uncorrected biomass C values had maxima of ±12%. Data obtained for seven dates using pre-extraction, wet-sieving, and centrifuging were compared with data obtained by the conventional procedure without any pretreatment. A negative difference from data obtained without pretreatment was found when the soil water content was decreased to 6%. The largest positive difference (+38%) was found in May during the period of highest root growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00384450
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  • 5
    Electronic Resource
    Electronic Resource
    Activity and biomass of soil microorganisms at different depths (1996)
    Springer
    Biology and fertility of soils 23 (1996), S. 38-42 
    Details
    ISSN: 1432-0789
    Keywords: Microbial biomass ; Depth profile ; Fumigation-extraction method ; Soil organic matter ; Dormant population
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We measured microbial biomass C and soil organic C in soils from one grassland and two arable sites at depths of between 0 and 90 cm. The microbial biomass C content decreased from a maximum of 1147 (0–10 cm layer) to 24 μg g-1 soil (70–90 cm layer) at the grassland site, from 178 (acidic site) and 264 μg g-1 soil (neutral site) at 10–20 cm to values of between 13 and 12 μg g-1 soil (70–90 cm layer) at the two arable sites. No significant depth gradient was observed within the plough layer (0–30 cm depth) for biomass C and soil organic C contents. In general, the microbial biomass C to soil organic C ratio decreased with depth from a maximum of between 1.4 and 2.6% to a minimum of between 0.5 and 0.7% at 70–90 cm in the three soils. Over a 24-week incubation period at 25°C, we examined the survival of microbial biomass in our three soils at depths of between 0 and 90 cm without external substrate. At the end of the incubation experiment, the contents of microbial biomass C at 0–30 cm were significantly lower than the initial values. At depths of between 30 and 90 cm, the microbial biomass C content showed no significant decline in any of the four soils and remained constant up to the end of the experiment. On average, 5.8% of soil organic C was mineralized at 0–30 cm in the three soils and 4.8% at 30–90 cm. Generally, the metabolic quotient qCO2 values increased with depth and were especially large at 70–90 cm in depth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00335816
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  • 6
    Electronic Resource
    Electronic Resource
    Prenatal development of the integument in Delphinidae (Cetacea: Odontoceti) (1995)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 223 (1995), S. 269-287 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The prenatal development of epidermis, dermis, and hypodermis was studied in embryos of different ago of two delphinid species (Stenella attenuata, Delphinus delphis), using light and transmission electron microscopical methods. The delphinid embryo is covered by a multilayered tissue formed by four different epidermal generations (periderm, stratum intermedium-I, str. intermedium-II, str. spinosum) produced by the str. basale. The first layer appears at about 40-50 mm of body length, the second type (s.i.-I) about 60-160 mm, and the third type (s.i.-II) is present at 160-500 mm. The first spinosal cells are produced at 225-260 mm body length; thenceforth, the epidermis increases continuously in thickness. Epidermal ridge formation begins about 400-mm body length. The development of the dermis is characterized by the early production of thin connective tissue fibers (40- 70-mm body length) and simultaneously the cutaneuous muscle matures in structure. Vascular development intensifies between embryos of 150-225 mm, and collagen production increases markedly in fetuses of 225-260-mm length. These events are paralledled by an increase in dermal thickness. The first elastic fibers can be recognized in the skin from the abdomen at about 600-mm body length. The development of the hypodermis is marked by very rapid and constantly progressing growth, beginning about 60-mm body length. The first typical fat cells appear in animals of 360-400 mm. Regional differences are obvious for all skin layers with regard to the flippers, where structural maturation proceeds more rapidly than in dorsal or abdominal regions. © 1995 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1052230305
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  • 7
    Electronic Resource
    Electronic Resource
    Tubulin gene expression during growth and maturation of leaves with different developmental patterns (1995)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 30 (1995), S. 67-72 
    Details
    ISSN: 0886-1544
    Keywords: Nicotiana ; Hordeum ; microtubule ; cell differentiation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Changes in the tubulin-protein and -poly(A)+RNA contents were monitored by means of Western and Northern blot analyses, respectively, during growth and maturation of leaves of a dicotyledonous (tobacco) and monocotyledonous (barley) plant. It was recently argued from immunofluorescence and preliminary biochemical data that the density of microtubular networks and concomitantly the tubulin content are distinctly reduced after cessation of cell growth in leaves [Jung et al., 1993]. The results presented now confirm and extend this view. There appeared to be clear differences between the monocot and the dicot: (1) the loss of tubulin during leaf development was much slower in the dicot than in the monocot leaves (within months instead of days); (2) the degree of loss was more dramatic in the monocot leaf and only very low threshold levels of tubulin were retained in fully differentiated tissues; and (3) the loss of tubulin in the monocot leaf tissue appeared to be correlated with the decrease in the mRNA content, whereas the high level of tubulin-RNA in fully differentiated or even almost senescent dicot leaves indicated a gene expression control at the posttranscriptional level.The comparatively rapid and very distinct tubulin-protein and -RNA disappearance during development of the monocot leaf tissues confirm at the molecular level that differentiation proceeds much faster and is much more determinative in these leaves, as was postulated from histological and physiological data. The differences in the behaviour of the microtubular cytoskeleton perhaps even reflect the differences in the ability of the differentiated leaf cells to dedifferentiate, i.e., to establish new sets of microtubules and to reenter the mitotic cell cycle, e.g., during would response, tumour induction or in vitro culture. © 1995 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970300108
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  • 8
    Electronic Resource
    Electronic Resource
    The Formal Total Synthesis of Epothilone A (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 2817-2823 
    Details
    ISSN: 1434-193X
    Keywords: Epothilone A ; Ring-closing metathesis ; Aldol reactions ; Lactones ; Diastereoselective alkylation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The formal total synthesis of epothilone A is described. The key steps in the synthesis of the northern hemisphere are a Z-selective ten-membered ring-closing metathesis reaction (RCM) and the diastereoselective alkylation at C8. Aldehyde 3 is formed by introduction of the thiazole moiety by a Wittig reaction and subsequent functional group transformation. An efficient route to keto acid 5 is described.
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  • 9
    Electronic Resource
    Electronic Resource
    Clusters on Clusters: closo-Dodecaborate as a Ligand for Au55 Clusters (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2051-2055 
    Details
    ISSN: 1434-1948
    Keywords: Gold clusters ; closo-Dodecaborate ; Conductivity ; Charging energy ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The exchange of PPh3 in Au55(PPh3)12Cl6 by Na2[B12H11SH] using a phase-transfer reaction from CH2Cl2 to water needs 6 weeks for reaction, but finally results in the quantitative formation of Au55[(B12H11SH)Na2]12Cl6 (2). Cluster 2, which is of considerable stability in aqueous solution, has been characterized by 1H-NMR, 11B-NMR, and IR spectroscopy as well as by transmission electron microscopy (TEM). The Na+ cations can be exchanged by (octyl)4N+ making the resulting cluster 4 soluble in polar organic solvents. The electrical properties of 2 and 4 are compared with those of Au55[Ph2PC6H4SO3N(octyl)4]12Cl6 (3), the ammonium derivative of the sodium salt. Cluster 3 shows the expected increase of activation energy in the temperature range of 130-250 K owing to the increase of cluster spacing compared with the sodium derivative. However, clusters 2 and 4, show electromigration in the electric field, caused by the huge amount of ionic charges in the ligand shell.
    Additional Material: 4 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Borane Insertion into Group-4 Metal-to-Carbon Bonds: The Reaction of HB(C6F5)2 with (η2-Formaldehyde)zirconocene Dimer and with (Butadiene)zirconocene (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2243-2247 
    Details
    ISSN: 1434-1948
    Keywords: Metallaoxirane ; HBR2 addition ; (Formaldehyde)zirconocene ; (Butadiene)zirconocene ; Heterocycles ; Boron ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (η2-Formaldehyde)zirconocene dimer (8) cleanly adds one or two molar equivalents of the borane HB(C6F5)2 by insertion of the H-[B] unit into the zirconium-carbon bond of the metallaoxirane moieties to form the mono- and bis-insertion products 16 and 17, respectively. These systems contain five-membered heterocyclic rings that are built up by connecting five different elements, namely H, B, C, O, and Zr. The bis(borane) insertion product 17 was characterized by an X-ray crystal structure analysis. (Butadiene)zirconocene reacts with HB(C6F5)2 in a similar way by insertion of the H-[B] unit into the (butadiene)C4-Zr linkage to form the metallacycle 18.
    Additional Material: 1 Ill.
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