共查询到20条相似文献,搜索用时 15 毫秒
1.
Alvin M. Weinberg 《Bulletin of mathematical biology》1941,3(2):39-55
The potential distribution about a kernleiter is determined according to Weber's method. It is shown that the distribution reduces to the solution of a telegrapher's equation when the volume of the external medium is small. The velocity of propagation as a function of the external volume is determined approximately. This involves the solution of the equation
$$\frac{{\left[ {Y_0 (k\xi )} \right]^\prime }}{{\left[ {J_0 (k\xi )} \right]^\prime }} = \frac{{\left[ {\xi ^{ - a} Y_0 (\xi )} \right]^\prime }}{{\left[ {\xi ^{ - a} J_0 (\xi )} \right]^\prime }}$$ 相似文献
2.
Nitrate and phosphate removal by<Emphasis Type="Italic"> Spirulina platensis</Emphasis> 总被引:5,自引:0,他引:5
Lodi A Binaghi L Solisio C Converti A Del Borghi M 《Journal of industrial microbiology & biotechnology》2003,30(11):656-660
The cyanobacterium Spirulina platensis was used to verify the possibility of employing microalgal biomass to reduce the contents of nitrate and phosphate in wastewaters. Batch tests were carried out in 0.5 dm3 Erlenmeyer flasks under conditions of light limitation (40 mol quanta m–2 s–1) at a starting biomass level of 0.50 g/dm3 and varying temperature in the range 23–40°C. In this way, the best temperature for the growth of this microalga (30°C) was determined and the related thermodynamic parameters were estimated. All removed nitrate was used for biomass growth (biotic removal), whereas phosphate appeared to be removed mainly by chemical precipitation (abiotic removal). The best results in terms of specific and volumetric growth rates ( =0.044 day–1, Q
x =33.2 mg dm–3 day–1) as well as volumetric rate and final yield of nitrogen removal (
=3.26 mg dm–3 day–1,
=0.739) were obtained at 30°C, whereas phosphorus was more effectively removed at a lower temperature. In order to simulate full-scale studies, batch tests of nitrate and phosphate removal were also performed in 5.0 dm3 vessels (mini-ponds) at the optimum temperature (30°C) but increasing the photon fluence rate to 80 mol quanta m–2 s–1 and varying the initial biomass concentration from 0.25 to 0.86 g/dm3. These additional tests demonstrated that an increase in the inoculum level up to 0.75 g/dm3 enhanced both NO3
– and PO4
3– removal, confirming a strict dependence of these processes on biomass activity. In addition, the larger surface area of the ponds and the higher light intensity improved removal yields and kinetics compared to the flasks, particularly concerning phosphorus removal ( =0.032–0.050 day–1, Q
x =34.7–42.4 mg dm–3 day–1,
=3.24–4.06 mg dm–3 day–1,
=0.750–0.879,
=0.312–0.623 mg dm–3 day–1, and
=0.224–0.440). 相似文献
3.
The average local ionization energy [`I] ( r ) \overline {\hbox{I}} \left( {\mathbf{r}} \right) is the energy necessary to remove an electron from the point r in the space of a system. Its lowest values reveal the locations of the least tightly-held electrons, and thus the favored
sites for reaction with electrophiles or radicals. In this paper, we review the definition of [`I] ( r ) \overline {\hbox{I}} \left( {\mathbf{r}} \right) and some of its key properties. Apart from its relevance to reactive behavior, [`I] ( r ) \overline {\hbox{I}} \left( {\mathbf{r}} \right) has an important role in several fundamental areas, including atomic shell structure, electronegativity and local polarizability
and hardness. All of these aspects of [`I] ( r ) \overline {\hbox{I}} \left( {\mathbf{r}} \right) are discussed. 相似文献
4.
Beth L. Young David A. S. Rosen Martin Haulena Allyson G. Hindle Andrew W. Trites 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2011,181(1):105-116
The ability to use heart rate (fh) to predict oxygen consumption rates (
[(V)\dot]\textO2 \dot{V}_{{{\text{O}}_{2} }} ) in Steller sea lions and other pinnipeds has been investigated in fasting animals. However, it is unknown whether established
fh:
[(V)\dot]\textO2 \dot{V}_{{{\text{O}}_{2} }} relationships hold under more complex physiological situations, such as when animals are feeding or digesting. We assessed
whether fh could accurately predict
[(V)\dot]\textO2 \dot{V}_{{{\text{O}}_{2} }} in trained Steller sea lions while fasting and after being fed. Using linear mixed-effects models, we derived unique equations
to describe the fh:
[(V)\dot]\textO2 \dot{V}_{{{\text{O}}_{2} }} relationship for fasted sea lions resting on land and in water. Feeding did not significantly change the fh:
[(V)\dot]\textO2 \dot{V}_{{{\text{O}}_{2} }} relationship on land. However, Steller sea lions in water displayed a different fh:
[(V)\dot]\textO2 \dot{V}_{{{\text{O}}_{2} }} relationship after consuming a 4-kg meal compared with the fasting condition. Incorporating comparable published fh:
[(V)\dot]\textO2 \dot{V}_{{{\text{O}}_{2} }} data from Steller sea lions showed a distinct effect of feeding after a 6-kg meal. Ultimately, our study illustrated that
both feeding and physical environment are statistically relevant when deriving
[(V)\dot]\textO2 \dot{V}_{{{\text{O}}_{2} }} from telemetered fh, but that only environment affects the practical ability to predict metabolism from fh. Updating current
bioenergetic models with data gathered using these predictive fh:
[(V)\dot]\textO2 \dot{V}_{{{\text{O}}_{2} }} equations will yield more accurate estimates of metabolic rates of free-ranging Steller sea lions under a variety of physiological,
behavioral, and environmental states. 相似文献
5.
6.
Veronique Billat Jean C. Renoux Jacques Pinoteau Bernard Petit Jean P. Koralsztein 《European journal of applied physiology and occupational physiology》1994,69(3):271-273
The aim of this study was to measure running times to exhaustion (Tlim) on a treadmill at 100% of the minimum velocity which elicits
max
max in 38 elite male long - distance runners
max = 71.4 ± 5.5 ml.kg–1.min–1 and
max = 21.8 ± 1.2 km.h–1). The lactate threshold (LT) was defined as a starting point of accelerated lactate accumulation around 4 mM and was expressed in
max. Tlim value was negatively correlated with
max (r = -0.362, p< 0.05) and
max (r = –0.347, p< 0.05) but positively with LT (%v
max) (r = 0.378, p < 0.05). These data demonstrate that running time to exhaustion at
max in a homogeneous group of elite male long-distance runners was inversely related to
max and experimentally illustrates the model of Monod and Scherrer regarding the time limit-velocity relationship adapted from local exercise for running by Hughson et al. (1984) . 相似文献
7.
Alfred Nimmerichter Johann Holdhaus Lars Mehnen Claudia Vidotto Markus Loidl Alan R. Barker 《International journal of biometeorology》2014,58(7):1503-1512
Limited research has suggested that acute exposure to negatively charged ions may enhance cardio-respiratory function, aerobic metabolism and recovery following exercise. To test the physiological effects of negatively charged air ions, 14 trained males (age: 32?±?7 years; \( \overset{\cdotp }{V}{\mathrm{O}}_{2 \max } \) : 57?±?7 mL min?1 kg?1) were exposed for 20 min to either a high-concentration of air ions (ION: 220?±?30?×?103 ions cm?3) or normal room conditions (PLA: 0.1?±?0.06?×?103 ions cm?3) in an ionization chamber in a double-blinded, randomized order, prior to performing: (1) a bout of severe-intensity cycling exercise for determining the time constant of the phase II \( \overset{\cdotp }{V}{\mathrm{O}}_2 \) response (τ) and the magnitude of the \( \overset{\cdotp }{V}{\mathrm{O}}_2 \) slow component (SC); and (2) a 30-s Wingate test that was preceded by three 30-s Wingate tests to measure plasma [adrenaline] (ADR), [nor-adrenaline] (N-ADR) and blood [lactate] (BLac) over 20 min during recovery in the ionization chamber. There was no difference between ION and PLA for the phase II \( \overset{\cdotp }{V}{\mathrm{O}}_2 \) τ (32?±?14 s vs. 32?±?14 s; P?=?0.7) or \( \overset{\cdotp }{V}{\mathrm{O}}_2 \) SC (404?±?214 mL vs 482?±?217 mL; P?=?0.17). No differences between ION and PLA were observed at any time-point for ADR, N-ADR and BLac as well as on peak and mean power output during the Wingate tests (all P?>?0.05). A high-concentration of negatively charged air ions had no effect on aerobic metabolism during severe-intensity exercise or on performance or the recovery of the adrenergic and metabolic responses after repeated-sprint exercise in trained athletes. 相似文献
8.
Lau GY Richards JG 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2011,181(7):927-939
In the present study, we test the hypothesis that AMP-activated protein kinase (AMPK) initiates metabolic rate suppression
in isolated goldfish hepatocytes. To accomplish this, we attempted to pharmacologically activate AMPK in goldfish hepatocytes
with 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR) and the thienopyridone, A769662, to examine the effects of AMPK
activation on eukaryotic elongation factor-2 (eEF2), protein synthesis, and cellular oxygen consumption rate (
[(M)\dot]\textO 2 \dot{M}_{{{\text{O}}_{ 2} }} ). Goldfish hepatocytes treated with 1 mM AICAR under normoxic conditions (>200 μM O2) showed a modest but significant 1.1-fold increase in AMPK phosphorylation, a 7.5-fold increase in AMPK activity, a 1.4-fold
increase in eEF2 phosphorylation, and a 24% decrease in
[(M)\dot]\textO 2 \dot{M}_{{{\text{O}}_{ 2} }} . At physiologically relevant [O2] (<40 μM O2), the addition of 1 mM AICAR resulted in only a 13% decrease in cellular
[(M)\dot]\textO 2 \dot{M}_{{{\text{O}}_{ 2} }} with no change in sensitivity to [O2] as assessed by estimates of cellular P50 and P90 values. The addition of compound C, a general protein kinase inhibitor, after AICAR incubation did not reverse the effects
of AICAR on
[(M)\dot]\textO 2 \dot{M}_{{{\text{O}}_{ 2} }} in normoxia. Treatment of hepatocytes with ≤200 μM A769662 did not affect AMPK activity, AMPK phosphorylation, eEF2 phosphorylation,
or cellular
[(M)\dot]\textO 2 \dot{M}_{{{\text{O}}_{ 2} }} . These data suggest that A769662 is not an activator of AMPK in goldfish hepatocytes. Although our study provides support
for the hypothesis that AMPK plays a role in initiating metabolic rate suppression in goldfish hepatocytes, this support must
be viewed cautiously because of the known off-target effects of the pharmacological agents used. 相似文献
9.
Manganese toxicity: The significance of magnesium for the sensitivity of wheat plants 总被引:1,自引:0,他引:1
The tolerance of wheat to manganese was investigated in soil and solution culture. Although no critical toxicity concentration could be identified, growth was reduced when the ratio of magnesium to manganese in the shoots (Rp) fell below 20:1 (mgg–1/mgg–1). In soil, plant growth relative to unstressed plants (Y) could be described by the empirical equation: % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaeywaiabg2% da9iaaicdacaGGUaGaaGyoaiaaiwdacqGHsislcaaIWaGaaiOlaiaa% iMdacaaI1aGaaeyzaiaabIhacaqGWbGaaiikaiabgkHiTiaaicdaca% GGUaGaaGymaiaaiodacaaI5aGaaeOuamaaBaaaleaacaqGWbaabeaa% kiaacMcaaaa!4959!\[{\text{Y}} = 0.95 - 0.95{\text{exp}}( - 0.139{\text{R}}_{\text{p}} )\]In solution culture the value of Rp was related to the ratio of the two ions in the nutrient solution (Rs) according to the expression: % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaeysaiaab6% gacaqGGaGaaeOuamaaBaaaleaacaqGWbaabeaakiabg2da9iaaicda% caGGUaGaaGinaiaaikdacqGHRaWkcaaIWaGaaiOlaiaaisdacaaI4a% GaaeiiaiaabMeacaqGUbGaaeiiaiaabkfadaWgaaWcbaGaae4Caaqa% baGccaGGPaaaaa!47B6!\[{\text{In R}}_{\text{p}} = 0.42 + 0.48{\text{ In R}}_{\text{s}}\]The magnesium concentration in the nutrient solution for optimum growth at a given concentration of manganese was given by: % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaeysaiaab6% gacaqGGaGaae4waiaab2eacaqGNbGaaeyxaiabg2da9iaaikdacaGG% UaGaaGioaiaaiMdacqGHRaWkcaaIWaGaaiOlaiaaiwdacaaI0aGaae% iiaiaabMeacaqGUbGaaeiiaiaabUfacaqGnbGaaeOBaiaab2faaaa!4A0B!\[{\text{In [Mg]}} = 2.89 + 0.54{\text{ In [Mn]}}\]Magnesium increased the tolerance of plants to high concentrations of manganese in shoot tissue and also increased the ability of the plant to discriminate against manganese ions in translocation of nutrients from roots to shoots. 相似文献
10.
Calcification, a process common to numerous marine taxa, has traditionally been considered to be a significant source of CO2 in tropical waters only. A number of relatively recent studies, however, have shown that significant amounts of CO2 are also produced in temperate waters, although none of these studies was carried out on rocky shores, which are considered
to be very productive systems. We compared the CO2 fluxes due to respiration and calcification in two temperate species, the cirripedes Chthamalus montagui and Elminius modestus. The population dynamics of both species were estimated at two sites during a 1-year experimental period in order to establish
mean organic (ash-free dry weight) and CaCO3 (dry shell weight) production. Based on these parameters, we estimated the CO2 fluxes due to respiration and calcification. CaCO3 production was estimated to be 481.0 and
at each site, representing 3.4 and respectively, of released CO2. These fluxes represent each 47% of the CO2 released as a result of respiration and calcification. The production of CaCO3 at the high-density site was: (1) among the highest values obtained for temperate organisms, and (2) comparable to the estimated
CO2 fluxes for coral reefs. As calcifying organisms are well represented in temperate ecosystems in terms of both density and
biomass, our results provide clear evidence that calcification of temperate organisms should not be underestimated. Additional
studies on other rocky shore taxa are needed before the relative importance of calcification in rocky intertidal carbon budgets
can be generalized. 相似文献
11.
Contribution of central versus sweat gland mechanisms to the seasonal change of sweating function in young sedentary males and females 总被引:1,自引:0,他引:1
Yumiko Taniguchi Junichi Sugenoya Naoki Nishimura Satoshi Iwase Takaaki Matsumoto Yuuki Shimizu Yoko Inukai Maki Sato 《International journal of biometeorology》2011,55(2):203-212
In summer and winter, young, sedentary male (N = 5) and female (N = 7) subjects were exposed to heat in a climate chamber in which ambient temperature (Ta) was raised continuously from 30
to 42°C at a rate of 0.1°C min−1 at a relative humidity of 40%. Sweat rates (SR) were measured continuously on forearm, chest and forehead together with tympanic
temperature (Tty), mean skin temperature ( [`T] s ) \left( {\overline {\hbox{T}} {\hbox{s}}} \right) and mean body temperature ( [`T] b ) \left( {\overline {\hbox{T}} {\hbox{b}}} \right) . The rate of sweat expulsions (Fsw) was obtained as an indicator of central sudomotor activity. Tty and ( [`T] b ) \left( {\overline {\hbox{T}} {\hbox{b}}} \right) were significantly lower during summer compared with winter in males; SR was not significantly different between summer and
winter in males, but was significantly higher during summer in females; SR during winter was higher in males compared with
females. The regression line relating Fsw to ( [`T] b ) \left( {\overline {\hbox{T}} {\hbox{b}}} \right) shifted significantly from winter to summer in males and females, but the magnitude of the shift was not significantly different
between the two subject groups. The regression line relating SR to Fsw was steepened significantly from winter to summer in
males and females, and the change in the slope was significantly greater in females than in males. Females showed a lower
slope in winter and a similar slope in summer compared to males. It was concluded that sweating function was improved during
summer mediated by central sudomotor and sweat gland mechanisms in males and females, and, although the change of sweat gland
function from winter to summer was greater in females as compared with males, the level of increased sweat gland function
during summer was similar between the two subject groups. 相似文献
12.
. F. zpolat B. Alm E. akar M. Bykyldz M. Kurudirek 《Radiation and environmental biophysics》2020,59(2):321-329
The purpose of the present work is robust calculation of effective atomic numbers ($${Z}_{\text{eff}}$$s) for photon, electron, proton, alpha particle and carbon ion interactions through the newly developed software, Phy-X/ZeXTRa (Zeff of materials for X-Type Radiation attenuation). A pool of total mass attenuation and energy absorption coefficients (for photons) and total mass stopping powers (for charged particles) for elements was constructed first. Then, a matrix of interaction cross sections for elements Z = 1–92 was constructed. Finally, effective atomic numbers were calculated for any material by interpolating adjacent cross sections through a linear logarithmic interpolation formula. The results for $${Z}_{\text{eff}}$$ for photon interaction were compared with those calculated through Mayneord’s formula, which suggests a single-valued $${Z}_{\text{eff}}$$ for any material for low-energy photons for which photoelectric absorption is the dominant interaction process. The single-valued $${Z}_{\text{eff}}$$ was found to agree well with that obtained by other methods, in the low-energy region. In addition, $${Z}_{\text{eff}}$$ values of various materials of biological interest were compared with those obtained experimentally at 59.54 keV. In general, the agreement between values calculated with Phy-X/ZeXTRa and Auto-Zeff and those measured were satisfactory. A comparison of $${Z}_{\text{eff}}$$ values for photon energy absorption calculated with Phy-X/ZeXTRa and literature values for a nucleotide base, adenine, was made, and the relative difference (RD) in $${Z}_{\text{eff}}$$ between Phy-X/ZeXTRa and literature values was found to be 2% < RD < 11%, at low photon energies (1–100 keV), while it was less than 1% at energies higher than 100 keV. Highest $${Z}_{\text{eff}}$$ values were observed at low photon energies, where photoelectric absorption dominates photon interaction. For electrons, corresponding RD(%) values in $${Z}_{\text{eff}}$$ were found to be in the range 0.4 ≤ RD(%) ≤ 1.7, while for heavy charged particle interactions it was 2.4 ≤ RD(%) ≤ 4.2 for total proton interaction and 0 ≤ RD(%) ≤ 8 for total alpha particle interaction. In view of the importance of $${Z}_{\text{eff}}$$ for identifying and differentiating tissues in diagnostic imaging as well as for estimating accurate dose in radiotherapy and particle-beam therapy, Phy-X/ZeXTRa could be used for fast and accurate calculation of $${Z}_{\text{eff}}$$ in a wide energy range for both photon and charged particle (electrons, protons, alpha particles and C ions) interactions. 相似文献
13.
Pseudomonas aeruginosa phosphorylcholine phosphatase (PchP) catalyzes the hydrolysis of phosphorylcholine, which is produced by the action of hemolytic
phospholipase C on phosphatidylcholine or sphyngomielin, to generate choline and inorganic phosphate. Among divalent cations,
its activity is dependent on Mg2+ or Zn2+. Mg2+ produced identical activation at pH 5.0 and 7.4, but Zn2+ was an activator at pH 5.0 and became an inhibitor at pH 7.4. At this higher pH, very low concentrations of Zn2+ inhibited enzymatic activity even in the presence of saturating Mg2+ concentrations. Considering experimental and theoretical physicochemical calculations performed by different authors, we
conclude that at pH 5.0, Mg2+ and Zn2+ are hexacoordinated in an octahedral arrangement in the PchP active site. At pH 7.4, Mg2+ conserves the octahedral coordination maintaining enzymatic activity. The inhibition produced by Zn2+ at 7.4 is interpreted as a change from octahedral to tetrahedral coordination geometry which is produced by hydrolysis of
the
[ \textZn 2+ \textL 2 - 1 \textL 20 ( \textH 2 \textO ) 2 ] \left[ {{\text{Zn}}^{ 2+ } {\text{L}}_{ 2}^{ - 1} {\text{L}}_{ 2}^{0} \left( {{\text{H}}_{ 2} {\text{O}}} \right)_{ 2} } \right] complex. 相似文献
14.
Jean-Philippe Bellenger Françoise Arnaud-Neu Zouhair Asfari Satish C. B. Myneni Edward I. Stiefel Anne M. L. Kraepiel 《Journal of biological inorganic chemistry》2007,12(3):367-376
Azotochelin is a biscatecholate siderophore produced by the nitrogen-fixing soil bacterium Azotobacter vinelandii. The complexation properties of azotochelin with a series of oxoanions [Mo(VI), W(VI) and V(V)] and divalent cations [Cu(II),
Zn(II), Co(II) and Mn(II)] were investigated by potentiometry, UV–vis and X-ray spectroscopy. Azotochelin forms a strong 1:1
complex with molybdate (log K = 7.6 ± 0.4) and with tungstate and vanadate; the stability of the complexes increases in the order Mo < V < W (log K
appMo = 7.3 ± 0.4; log K
appV = 8.8 ± 0.4 and log K
appW = 9.0 ± 0.4 at pH 6.6). The Mo atom in the 1:1 Mo–azotochelin complex is bound to two oxo groups in a cis position and to the two catecholate groups of azotochelin, resulting in a slightly distorted octahedral configuration. Below
pH 5, azotochelin appears to form polynuclear complexes with Mo in addition to the 1:1 complex. Azotochelin also forms strong
complexes with divalent metals. Of the metals studied, Cu(II) binds most strongly to azotochelin , followed by Zn(II) , Mn(II) and Co(II) . Since very few organic ligands are known to bind strongly to oxoanions (and particularly molybdate) at circumneutral pH,
the unusual properties of azotochelin may be used for the separation and concentration of oxoanions in the laboratory and
in the field. In addition, azotochelin may prove useful for the investigation of the biogeochemistry of Mo, W and V in aquatic
and terrestrial systems.
Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. 相似文献
15.
Yue Fu Kevin E. Bruce Britta Rued Malcolm E. Winkler David P. Giedroc 《Biomolecular NMR assignments》2016,10(1):89-92
FtsX is an integral membrane protein from Streptococcus pneumoniae (pneumococcus) that harbors an extracellular loop 1 domain (\({\text{FtsX}}^{\text{ECL1}}_{Spn}\)) that interacts with PcsB, an peptidoglycan hydrolase that is essential for cell growth and division. Here, we report nearly complete backbone and side chain resonance assignments and a secondary structural analysis of \({\text{FtsX}}^{\text{ECL1}}_{Spn}\) (residues 47–168 of FtsX) as first steps toward structure determination of \({\text{FtsX}}^{\text{ECL1}}_{Spn}\). 相似文献
16.
A. C. Fischer O. M. Steinebach K. R. Timmermans H. T. Wolterbeek 《Journal of applied phycology》2007,19(1):71-77
Diatoms in the Southern Ocean are limited by iron and light, and therefore produce little biomass. Sufficient biomass for
analysis under these conditions requires large sample volumes, and diatom samples are therefore often pre-concentrated on
a filter. A method for the digestion of diatom cells on polycarbonate filters, that is also suitable for trace metal analysis,
is described here. Additional analysis by inductively coupled plasma-optical emission spectroscopy (ICP-OES) is used for the
determination of biogenic silicon. Although several procedures were tested, the method of Hauptkorn et al., which uses tetramethylammonium
hydroxide for the destruction of silicon is adapted here [Hauptkorn et al. (2001) Fres J Anal Chem 370:246–250]. Additional
nitric acid is added to destroy the polycarbonate filters. The described method results in clear digests and a good correlation
between cell numbers and silicon content. Using this procedure, the cellular silicon content for Chaetoceros brevis was determined as 86 ± 4 fmol cell−1. For Thalassiosira sp. a sensitivity effect was observed, and silicon content was determined as . The obtained cellular silicon contents are in good agreement with values presented in the literature. 相似文献
17.
Limnology and plankton periodicity of Jos Plateau water reservoir,Nigeria, West Africa 总被引:1,自引:1,他引:0
Limnological data (Dec. 1980–Jan. 1982) on the plankton and water chemistry of Lamingo Dam, located within the Jos biotite granite area of the Plateau State (Nigeria) are presented. The water-body falls in Beadle's (1981) category I of African lakes (conductivity < 40 µS cm–1). Alkalinity (% MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0Jf9crFfpeea0xh9v8qiW7rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGabmiEayaara% aaaa!3914!\[\bar x\] = 0.3 meq l–1), principally composed of bicarbonates, dominated the anions % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0Jf9crFfpeea0xh9v8qiW7rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaK4waiaajI% eacaqIdbGaaK4tamaaxababaGaeyOeI0caleaacaaIZaaabeaakiaa% b6dacaqIdbGaaKiBaiaaj2cacaqG+aGaaK4uaiaaj+eadaqhaaWcba% GaaKinaaqaaiaajkdacaqITaaaaOGaaKyxaaaa!4657!\[\user1{[HCO}\mathop -\limits_3 {\text{ > }}\user1{Cl - }{\text{ > }}\user1{SO}_\user1{4}^{\user1{2 - }} \user1{]}\]The plankton were characterized by a moderate standing crop of phytoplankton, and zooplankton were, generally, very limited in species and abundance. The order of dominance for the categories of phyto and zooplankton was: [Bacillariophyceae > Chlorophyceae > Dinophyceae] and [Rotifera > Crustacea] respectively. A diel cycle was characterized by nocturnal upward migration of the zooplankton, and the reverse behaviour in the phytoplankton.Interrelations between the biotic assemblages of plankters and various physical and chemical variables are discussed. 相似文献
18.
The effect of dielectric constant (D) of the solvent on the viscosity of heparin was examined using the relation \documentclass{article}\pagestyle{empty}\begin{document}$ \eta _{{\rm sp}} /c = [\eta ]_\infty (1 + k/\sqrt c) $\end{document}, where [η]∞ is the shielded intrinsic viscosity obtained by extrapolating \documentclass{article}\pagestyle{empty}\begin{document}$ \eta _{{\rm sp}} /c\,{\rm vs}{\rm . }\,1/\sqrt c ) $\end{document} to infinite concentration, and k is an interaction parameter independent of the dielectric constant of the solvent. This equation was previously reported by the authors9 for describing the reduced viscosities of strong polyelectrolytes in salt-free polar solvents. It was found that the [η]∞ of heparin increases linearly with increasing dielectric constant of the solvent whereas the k values were, within experimental error, independent of D in the range 54.7 < D < 93.2 examined. Graded hydrolysis of heparin from its acid form (heparinic acid) at 57°C resulted in samples of varying degree of desulfation with corresponding decrease in biological activity. It was found that both [η]∞ and k decrease with increasing desulfation. 相似文献
19.
B. Culik A. J. Woakes D. Adelung R. P. Wilson N. R. Coria H. J. Spairani 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1990,160(1):61-70
Summary The energy requirements of Adélie penguin (Pygoscelis adeliae) chicks were analysed with respect to body mass (W, 0.145–3.35 kg, n=36) and various forms of activity (lying, standing, minor activity, locomotion, walking on a treadmill). Direct respirometry was used to measure O2 consumption (
) and CO2 production. Heart rate (HR, bpm) was recorded from the ECG obtained by both externally attached electrodes and implantable HR-transmitters. The parameters measured were not affected by hand-rearing of the chicks or by implanting transmitters. HR measured in the laboratory and in the field were comparable. Oxygen uptake ranged from
in lying chicks to
at maximal activity, RQ=0.76. Metabolic rate in small wild chicks (0.14–0.38 kg) was not affected by time of day, nor was their feeding frequency in the colony (Dec 20–21). Regressions of HR on
were highly significant (p< 0.0001) in transmitter implanted chicks (n=4), and two relationships are proposed for the pooled data, one for minor activities (
), and one for walking (
). Oxygen consumption, mass of the chick (2–3 kg), and duration of walking (T, s) were related as
, whereas mass-specific O2 consumption was related to walking speed (S, m·s-1) as
.Abbreviations
bpm
beats per minute
-
D
distance walked (m)
-
ECG
electrocardiogram
-
HR
heart rate (bpm)
-
ns
number of steps
-
RQ
respiratory quotient
-
S
walking speed (m·s-1)
-
T
time walked (s)
-
W
body mass (kg) 相似文献
20.
Glutamine-free culture of Vero cells has previously been shown to cause higher cell yield and lower ammonia accumulation than
that in glutamine-containing culture. Nitrogen metabolism of asparagine and glutamate as glutamine replacer was studied here
using nuclear magnetic resonance (NMR) spectroscopy. 15N-labelled glutamate or asparagine was added and their incorporation into nitrogenous metabolites was monitored by heteronuclear
multiple bond coherence (HMBC) NMR spectroscopy. In cells incubated with l-[15N]glutamate, the 15N label was subsequently found in a number of metabolites including alanine, aspartate, proline, and an unidentified compound.
No detectable signal occurred, indicating that glutamate was utilized by transamination rather than by oxidative deamination. In cells
incubated with l-[2-15N]asparagine, the 15N label was subsequently found in aspartate, the amine group of glutamate/glutamine, and in two unidentified compounds. Incubation
of cells with l-[4-15N]asparagine showed that the amide nitrogen of asparagine was predominantly transferred to glutamine amide. There was no detectable
production of , showing that most of the asparagine amide was transaminated by asparagine synthetase rather than deaminated by asparaginase.
Comparing with a glutamine-containing culture, the activities of phosphate-activated glutaminase (PAG), glutamate dehydrogenase
(GDH) and alanine aminotransferase (ALT) decreased significantly and the activity of aspartate aminotransferase (AST) decreased
slightly. 相似文献