Seagrass habitat complexity and macroinvertebrate abundance in Lakshadweep coral reef lagoons,Arabian Sea

Macrofauna of seagrass community in the five Lakshadweep atolls were studied and compared. The associated epifaunal and infaunal taxa comprising nine major taxonomic groups, showed significant differences in the total number of individuals (1041–8411 m^–2) among sites and habitats. The density of macrofauna was directly related to mean macrophytic biomass (405–895 g wet wt. m^–2). The fauna was dominated by epifaunal polychaetes, amphipods and isopods in the vegetated areas. When compared with the density of nearby unvegetated areas , seagrass meadows harbour a denser and richer macroinvertebrate assemblage .     

Emission of microorganisms from biofilters

Experiments are reported on the discharge of microbial germs by biofilter systems used for the treatment of waste gases containing volatile organic compounds. The systems investigated concern six full-scale filter installations located in the Netherlands in several branches of industry, as well as a laboratory-scale installation used for modelling the discharge process. It is concluded that the number of microbial germs (mainly bacteria and to a much smaller extent moulds) in the outlet gas of the different full scale biofilters varies between 10³ and 10⁴ m^–3, a number which is only slightly higher than the number encountered in open air and of the same order of magnitude encountered in indoor air. It is furthermore concluded that the concentration of microorganisms of a highly contaminated inlet gas is considerably reduced by the filtration process. On the basis of the experiments performed in the laboratory-scale filter bed, it is shown that the effect of the gas velocity on the discharge process results from two distinctive mechanisms: capture and emission. A theoretical model is presented describing the rate processes of both mechanisms. The model presented and the experimentally determined data agree rather well.List of Symbols a _s m^–1 specific area of the packing material - C m^–3 microbial gas phase concentration - C _e , C _i m^–3 microbial concentration in the exit and inlet gas resp. - CFU colony-forming-units - d _c , d _m m diameter of collecting and captured particle resp. - D m diameter of the filter bed - E single particle target efficiency - H m bed height - k _c s^–1 first order capture rate constant per unit of bedvolume - k _e m^–3 emission rate constant per unit of bedvolume - n number of observations - r _c , r _e m^–3 s^–1 capture and emission rate per unit of bed-volume - Re = Reynolds number - S _t = Stokes number - u m s^–1 superficial gas velocity - u _m m s^–1 superficial gas velocity at which C _e = C _i Greek Symbols void fraction of the filter bed - kg m^–3 density of the gas phase - _m kg m^–3 density of captured particle - Pa s dynamic gas phase viscosity - = filter bed efficiency     

A method for determining the maximal steady state of blood lactate concentration from two levels of submaximal exercise

The aim of this study was to estimate the characteristic exercise intensity _CL which produces the maximal steady state of blood lactate concentration (MLSS) from submaximal intensities of 20 min carried out on the same day and separated by 40 min. Ten fit male adults [maximal oxygen uptake _max 62 (SD 7) ml · min^–1 · kg^–1] exercisOed for two 30-min periods on a cycle ergometer at 67% (test 1.1) and 82% of _max (test 1.2) separated by 40 min. They exercised 4 days later for 30 min at 82% of _max without prior exercise (test 2). Blood lactate was collected for determination of lactic acid concentration every 5 min and heart rate and O₂ uptake were measured every 30 s. There were no significant differences at the 5th, 10th, 15th, 20th, 25th, or 30th min between , lactacidaemia, and heart rate during tests 1.2 and 2. Moreover, we compared the exercise intensities _CL which produced the MLSS obtained during tests 1.1 and 1.2 or during tests 1.1 and 2 calculated from differential values of lactic acid blood concentration ([1a^–]_b) between the 30th and the 5th min or between the 20th and the 5th min. There was no significant difference between the different values of _CL [68 (SD 9), 71 (SD 7), 73 (SD 6),71 (SD 11) % of _max (ANOVA test,P<0.05). Four subjects ran for 60 min at their _CL determined from periods performed on the same day (test 1.1 and 1.2) and the difference between the [la^–]_b at 5 min and at 20 min ( ([la^–]_b)) was computed. The [la^–]_b remained constant during exercise and ranged from 2.2 to 6.7 mmol · l^–1 [mean value equal to 3.9 (SD 1) mmol · l^–1]. These data suggest that the _CL protocol did not overestimate the exercise intensity corresponding to the maximal fractional utilization of _max at MLSS. For half of the subjects the _CL was very close to the higher stage (82% of _max where an accumulation of lactate in the blood with time was observed. It can be hypothesized that _CL was very close to the real MLSS considering the level of accuracy of [la^–]_b measurement. This study showed that exercise at only two intensities, performed at 65% and 80% of _max and separated by 40 min of complete rest, can be used to determine the intensity yielding a steady state of [la^–1]_b near the real MLSS workload value.     

Life cycle and growth ofTrichostegia minor (Curtis) in temporary woodland pools (Trichoptera: Phryganeidae)

Larvae of the caddisTrichostegia minor (Curtis) were collected from four woodland pools in The Netherlands, three of which are temporary, from August 1986 till June 1987. Eggs and larvae of this species proved to be very well adapted to drought, freezing, strongly fluctuating pH and alkalinity levels and prolonged oxygen deficit. The life cycle ofT.minor in a small woodland marsh overgrown byCalla palustris took one year. Adult flight period started at the end of May. Oviposition took place independent of water. Hatching of the eggs started in September and was probably induced by immersion. During the larval stage from September until May, 5 instars could be distinguished by the size of the head capsule. Growth of instars I, II and III during autumn was moderate. Most larvae overwintered as instar III or IV. Possibly there was a larval diapause during winter. In spring rapid growth to instar V took place prior to pupation. Growth rate, expressed as the increase of mean individual dry weight was highest from March to April (2.05±0.75% DW.m^–2.d^–1). In extremely shallow water growth in spring was initially more rapid compared to growth in deeper water. During winter the growth rate decreased to 0.038±0.071% DW.m^–2.d^–1. Net annual production based on the changes of momentary biomass was 183.2±31.7 mg DW.m^–2.y^–1 or 177.2±31.3 mg AFDW.m^–2.y^–1. Production loss during the winter season was 75.1±10.8 mg DW.m^–2.y^–1 or 72.3±10.6 mg AFDW.m^–2.y^–1.     

The distribution of Heterotrissocladius oliveri Saether (Diptera: Chironomidae) in Lake Michigan

Fifty one chironomid species were identified from 504 samples collected at depths ranging 8 to 267 m in Lake Michigan, U.S.A. Heterotrissocladius oliveri Saether occurred in 32% of these samples and had an average abundance of 22 m^–2 which was similar to other estimates from the Great Lakes. Maximum average lake-wide density was at 30 to 60 m (41 m^–2). At depths 60 m, H. oliveri was the dominant chironomid species comprising 75% of total Chironomidae. The substrate preference of H. oliveri differed within each depth regime considered: at 30–60 m, 2–3 ; at 60–120 m, 3–5 , 7–9 ; and at 120–180 m, 6–8 . Abundance was notably reduced at all depths in substrates characterized as medium silt (5–6 ). On a lake-wide basis, the distribution pattern suggested H. oliveri was most numerous from 30 to 60 m along the southwestern, eastern, and northern shorelines and at 60–120 m depths along the southern and eastern shorelines. Increased abundance in the South Basin was concurrent with evidence of increased sedimentation at 60 to 100 m. However, in several other areas of the lake, high densities were associated with medium to very fine sands relatively free of silts and clays. This observation suggested occurrence of H. oliveri was minimally affected by sediment type.Widely variable, but generally elevated water temperatures likely prevent H. oliveri from establishing a substantial population density at depths < 30 m. With increased depth, temperature fluctuation is negligible and food is more stable, though the source is variable. Factors limiting abundance of H. oliveri at depths 30 m were related to decreased food supply due to distance from shore, food sources of lower value (clays), and, most importantly, to reproductive replenishment.Although still oligotrophic in nature, high density occurrences in both high and low sedimentation areas of the lake suggest the trophic indicator status of H. oliveri might be broader than previously thought.     

Energy expenditure and cardiorespiratory responses at the transition between walking and running

We investigated whether the spontaneous transition between walking and running during moving with increasing speed corresponds to the speed at which walking becomes less economical than running. Seven active male subjects [mean age, 23.7 (SEM 0.7) years, mean maximal oxygen uptake ( ), 57.5 (SEM 3.3) ml·kg ^–1·min ^–1, mean ventilatory threshold (VTh), 37.5 (SEM 3) ml·kg ^–1 ·min ^–1] participated in this study. Each subject performed four exercise tests separated by 1-week intervals: test 1, and VTh were determined; test 2, the speed at which the transition between walking and running spontaneously occurs (ST) during increasing speed (increases of 0.5 km·h ^–1 every 4 min from 5 km·h ^–1) was determined; test 3, the subjects were constrained to walk for 4 min at ST, at ST ± 0.5 km·h ^–1 and at ST ± 1 km·h ^–1; and test 4, the subjects were constrained to run for 4 min at ST, at ST±0.5 km·-h ^–1 and at ST±1 km·h ^–1. During exercise, oxygen uptake ( ), heart rate (HR), ventilation ( ), ventilatory equivalents for oxygen and carbon dioxide (% MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGabmOvayaaca% WaaSbaaSqaaiaabweaaeqaaOGaai4laiqadAfagaGaamaaBaaaleaa% caqGYaaabeaakiaacYcacaqGGaGaaeiiaiqadAfagaGaamaaBaaale% aacaqGfbaabeaakiaac+caceWGwbGbaiaacaqGdbGaae4tamaaBaaa% leaacaaIYaaabeaaaaa!4240!\[\dot V_{\text{E}} /\dot V_{\text{2}} ,{\text{ }}\dot V_{\text{E}} /\dot V{\text{CO}}_2 \]), respiratory exchange ratio (R), stride length (SL), and stride frequency (SF) were measured. The results showed that: ST occurred at 2.16 (SEM 0.04) m·s ^–1; , HR and speed at ST were significantly lower than the values measured at VTh (P< 0.001, P< 0.001 and P< 0.05, respectively); changed significantly with speed (P< 0.001) but was greater during running than walking below ST (ST minus 1 km·h ^–1, P< 0.001; ST minus 0.5 km·h ^–1, P< 0.05) with the converse above ST (ST.plus 1 km·h ^–1, P<0.05), whereas at ST the values of were very close [23.9 (SEM 1.1) vs 23.7 (SEM 0.8) ml·kg ^–1 · min ^–1 not significant, respectively, for walking and running]; SL was significantly greater during walking than running (P<0.001) and SF lower (P<0.001); and HR and were significantly greater during running than walking below ST (ST minus 1 km·h ^–1, P<0.01; ST minus 0.5 km·h ^–1, P{<0.05) with the converse above ST (ST plus 1 km·h ^–1, P·< 0.05), whereas no difference appeared for and R between the two types of locomotion. We concluded from this study that ST corresponded to the speed at which the energy expenditure of running became lower than the energy expenditure of walking but that the mechanism of the link needed further investigation.     

Changes in acid-base status of marathon runners during an incremental field test Relationship to mean competitive marathon velocity

Four top-class runners who regularly performed marathon and long-distance races participated in this study. They performed a graded field test on an artificial running track within a few weeks of a competitive marathon. The test consisted of five separate bouts of running. Each period lasted 6 min with an intervening 2-min rest bout during which arterialized capillary blood samples were taken. Blood was analysed for pH, partial pressure of oxygen and carbon dioxide (P0₂ and PCO₂) and lactate concentration ([la^–]_b). The values of base excess (BE) and bicarbonate concentration ([HCO₃ ^–]) were calculated. The exercise intensity during the test was regulated by the runners themselves. The subjects were asked to perform the first bout of running at a constant heart rate f _c which was 50 beats · min^–1 below their own maximal f _c. Every subsequent bout, each of which lasted 6 min, was performed with an increment of 10 beats · min^–1 as the target f _c. Thus the last, the fifth run, was planned to be performed with fc amounting to 10 beats · min^–1 less than their maximal f _c. The results from these runners showed that the blood pH changed very little in the bouts performed at a running speed below 100% of mean marathon velocity ( _m). However, once _mwas exceeded, there were marked changes in acid-base status. In the bouts performed at a velocity above the _mthere was a marked increase in [la^–]_b and a significant decrease in pH, [HCO₃ ^–], BE and PCO₂. The average marathon velocity ( _m) was 18.46 (SD 0.32) km·h^–1. The [la^–]_b at a mean running velocity of 97.1 (SD 0.8) % of _mwas 2.33 (SD 1.33) mmol ·l^–1 which, compared with a value at rest of 1.50 (SD 0.60) mmol·l^–1, was not significantly higher. However, when running velocity exceeded the vm by only 3.6 (SD 1.9) %, the [la^–]b increased to 6.94 (SD 2.48) mmol·l-1 (P<0.05 vs rest). We concluded from our study that the highest running velocity at which the blood pH still remained constant in relation to the value at rest and the speed of the run at which [la^–]_b began to increase significantly above the value at rest is a sensitive indicator of capacity for marathon running.     

Laser light scattering determination of size and dispersity of synaptosomes and synaptic vesicles isolated from squid (Loligo pealei) optic lobes

Quasi-elastic laser light scattering has been used to investigate the size and dispersity of synaptosomes and synaptic vesicles isolated from optic lobes of the squid Loligo pealei. Synaptosomal fractions were highly polydisperse ( ) and the mean diameter ( ) ranged from 0.5–2.0 m. Size distribution histograms yielded two major components — smaller particles ( ) and a larger group of particles ( ). The heterogeneity of the synaptosomal particles detected in solution is in agreement with published data obtained using electron microscopy. Purified synaptic vesicle fractions also yielded complex particle size distribution data. A component with a mean diameter in the range 150–250 nm was detected, though a smaller particle ( ) dominated the scattering signal. This smaller particle closely resembles in size the electron lucent vesicles seen in the majority of squid optic lobe nerve terminals when examined by electron microscopy. Osmotically-induced shirnkage and swelling of the synptosomes was detected. Depolarization by veratridine (1.0×10^–4 M) did not result in a detectable change in the size of synaptosomal particles.     

The effect of ambient temperature on the relationship between ventilation and metabolism in a small parrot (Agapornis roseicollis)

Summary Values for basal metabolism, standard tidal volume (V _T), standard minute volume ( ), and mean extraction efficiency (EO₂) in the thermal neutral zone (TNZ) inAgapornis roseicollis (1.84 ml·min^–1; 0.95 ml·br^–1, STPD; and 33.3 ml·min^–1, STPD; and 22.5%; respectively) were all very similar to values for these parameters previously measured inBolborhynchus lineola, a similarly sized, closely related species from a distinctly different habitat.Having both a lower critical temperature (T_lc) below and an upper critical temperature (T_uc) above those ofB. lineola, the TNZ ofA. roseicollis extended from 25° to at least 35°C. The thermal conductance below the TNZ ofA. roseicollis was 14% less than that ofB. lineola. Therefore, at 5°C the standard metabolic rate (SMR) of the former is 17% less than that of the latter, and at 35°C it is 20% less. At 5°CA. roseicollis has a lower EO₂ and at 35°C a higher EO₂ than that ofB. lineola. The patterns of resting energy metabolism and of ventilation ofA. roseicollis and ofB. lineola are consistent with the former species being better suited to living in a more variable thermal environment than the latter.MeanV _T has a weak positive correlation with the rate of oxygen consumption ( ) at a constant ambient temperature (T _a) but a much stronger correlation when resting increases in response to a decrease inT _a.V _t is the only ventilatory parameter which is linearly correlated toT _a from 35° to –25°C. The data suggest thatT _a may have a regulatory effect onV _T somewhat independent of or .     

Apparent viscosity for non-Newtonian fermentation media in bioreactors

The apparent viscosity of non-Newtonian fermentation media is examined. The present state of this subject is discussed. The energy dissipation rate concept is used for a new evaluation of the apparent viscosity in bioreactors, i.e. stirred tank and bubble column bioreactors. The proposed definition of the apparent viscosity is compared with the definitions available in the literature.List of Symbols A _d m ² downcomer cross-sectional area - A _r m ² riser cross-sectional area - a m^–1 specific surface area - C constant in eq. (13) - D m column diameter - D _I m impeller diameter - g m s^–2 gravitational acceleration - h J m^–2 s^–1 K^–1 heat transfer coefficient - K Pa s ⁿ consistency index in a power-law model - k constant in eq. (3) - k _L m s ^–1 liquid-phase mass transfer coefficient - N s^–1 impeller speed - n flow index in a power-law model - P W power input - Re Reynolds number ND _I ^/2 /(/) - U _sg m s ^–1 superficial gas velocity - (U _sg ) _r m s^–1 superficial gas velocity based on riser - V-m³ liquid volume - v ₀ m s^–1 friction velocity Greek Symbols s^–1 shear rate - _c s^–1 characteristic shear rate - W kg^–1 energy dissipation rate per unit mass - W kg^–1 characteristic energy dissipation rate per unit mass - Pa s viscosity - _app Pa s apparent viscosity - kg m^–3 density - Pa shear stress     

Prediction of individual oxygen uptake on-step transients from frequency responses

Power-oxygen uptake ( ) frequency responses can be used to predict responses to arbitrary exercise intensity patterns. It is still an open question for which range of exercise intensities such computed response patterns yield valid predictions. In the present study, we determined the power- frequency response of nine sports students by means of pseudo-randomised switching between 20 W and 80 W during upright and supine cycle exercise. Starting from a baseline of 20 W each subject also performed sustained step increases to 40 W, 80 W, 120 W, and 160 W in both positions. The individual step responses were then compared with the expected time-courses predicted on the basis of the individual frequency responses. The comparison showed a close agreement for the 20 W–40 W and 20 W–80 W steps in both positions. With larger step amplitudes the kinetics became increasingly slower than the predicted time course in both positions. During additional ramp tests (10 W · 30 s^–1) whole blood lactic acid concentration [1a^–]_b tended to be higher in the supine position at exercise intensities higher than 160 W. The mean power at 4 mmol · 1^–1 [la^–]_b amounted to 234 (SD 32) W and 253 (SD 44) W (P<5%) in the supine and the upright position, respectively. The maximal oxygen uptake relative to body mass was not found to be significantly different [upright, mean 57 (SD 10) ml · (min · kg)^–1;supine, mean 54 (SD 10) ml · (min · kg)]. These findings would suggest that for a range of mild exercise intensities kinetics are not appreciably influenced by the step amplitude or by cardiovascular changes associated with the upright and the supine position.     

Energy requirements of Adélie penguin (Pygoscelis adeliae) chicks

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)     

A comparative study of the mechanism of Na+ and Cl? excretion by the gill ofMugil capito andFundulus heteroclitus: Effects of Stress

Summary In seawater (SW)-adaptedMugil andFundulus, gill effluxes of Na⁺ and of Cl^– and the simultaneously recorded transgill potential (P.D.) differ according to whether they are measured in stressed or rested animals.In rested animals of the two species, transfer to Ringer's solution considerably reduces the P.D. but not . InFundulus, is also decreased. Transfer of the two species from SW to fresh water (FW) reduces and by 75 to 85% and leads to a large inversion of P.D. When K⁺ is added to FW, a gill depolarization occurs, as well as a large increase of and .These results suggest that: 1) the P.D. originates primarily from the diffusion of cations, the gill permeability to Na⁺ ( ) being greater than that to Cl^– ( ), 2) a Cl^–/Cl^– exchange independent of P.D. is associated with the Cl^– pump; 3) Cl^– pump activity is linked to Na⁺/K⁺ exchange which in turn is associated to a Na⁺/Na⁺ exchange diffusion mechanism.In stressed individuals of the two species, the P.D. in SW, as well as the P.D. changes observed during transfer experiments, are considerably reduced. The decrease of and observed after transfer from SW to FW are also minimised. Changes are smaller inFundulus. The decrease of P.D. characterizing stressed animals may be at least in part due to a 3 to 4 fold increase of which becomes equal to in both species.As a result of stress, the K⁺-activated Na⁺ and Cl^– excretion mechanisms are totally inhibited inFundulus and partially so inMugil.Stress response seems more intense inFundulus and recovery from stress faster inMugil.     

The characterization of a viscoelasticity parameter and other rheological properties of various xanthan gum fermentation broths and solutions

Viscoelasticity has important implications in mass transfer and mixing processes. Previous studies regarding to the viscoelastic behaviour of xanthan solutions have been carried out with diluted solutions or they have not covered a wide range of polymer concentrations. In this study, it was shown that the first normal stress difference measured in fermentation broths is highly dependent on shear rate, and this viscoelastic level is modified by the heat treatment to which the broths are subjected as a postfermentative procedure. The viscoelasticity level is different for xanthan solutions prepared with products arising from different sources and for fermentation broths before the heat treatment, if compared with that measured in end-products. In general, the higher the polymer concentration, the higher the viscoelasticity (expressed as first normal stress difference or Weissenberg number). The addition of a biocide, the change in ionic strength and the addition of sucrose to the xanthan solutions, lead to significant changes in the first normal stress difference.List of Symbols A Pa.S^b constant in first normal stress difference power law (N ₁= ) - b constant in first normal stress difference power law (N ₁= ) - c kg m^–3 polymer concentration - K Nsⁿ m^–2 consistency index - N ₁ Pa first normal stress difference - n flow behaviour index - Wi Weissenberg number,N ₁/ - s^–1 shear rate - Pa shear stress - _y Pa Yield stress     

The influence of road salts on the salinity and the meromictic stability of Lake Svinsjøen,southeastern Norway

Primarily as a result of road salting, the water masses ofLake Svinsjøen, a small meromictic lake in southeasternNorway, have been subject to great changes in salinity duringthe period 1947–1995. The greatest change in saltconcentration has occurred in the upper part of themonimolimnion (depth 10–15 m) where mean conductivityincreased 104.2 per cent, from 143 to 292 S cm^–1. Inthe upper mixolimnion (depth 0-5 m), mean conductivity rosefrom 130 to 238 S cm^–1 during the same period. Theions responsible for the salinity changes were Na⁺ andCl^– from de-icing salts, and Ca²⁺ and Cl^– fromsalts used to keep down dust from roads. Further sources ofCa²⁺ are the road asphalt and increased weathering andleaching of the lime-rich rocks caused by acid precipitation,the main source of the additional inputs of SO tothe lake. The salinity changes caused major changes inmeromictic stability, S . In the period1947-1966, S increased by 24 g cm cm^–2,and the maximum level of meromictic stability, 125 gcm^–2, was found in 1966. As a result of higher rate ofsalt accumulation in the upper part of the monimolimnion andin the mixolimnion, S decreased by 30 g cmcm^–2 during the period 1966-1991, and a simultaneousrise in the chemocline took place. In the period 1991-1995 anadditional decrease of 26 g cm cm^–2 occurred. Continuedectogenic inputs of salts through processes typical of thetime period investigated will in future further weaken thelake's meromictic stability, and may cause the demise ofmeromixis in Lake Svinsjøen, a development which may haveimportant implications for primary productivity of thelake.     

Mathematical modeling of mixing in a horizontal rotating tubular bioreactor: “Simple flow” model

The construction of the horizontal rotating tubular bioreactor (HRTB) represents a combination of a thin-layer bioreactor and a biodisc reactor. The bioreactor was made of a plastic tube whose interior was divided by the O-ring shaped partition walls. For the investigation of mixing properties in HRTB the temperature step method was applied. The temperature change in the bioreactor as a response to a temperature step in the inlet flow was monitored by six Pt-100 sensors (t ₉₀ response time 0.08 s and resolution 0.002 °C) which were connected with an interface unit and personal computer. Mixing properties of the bioreactor were modeled using the modified tank in series concept which divided the bioreactor into ideally mixed compartments. A mathematical mixing model with simple flow was developed according to the physical model of the compartments network and corresponding heat balances. Numerical integration of an established set of differential equations was done by the Runge-Kutt-Fehlberg method. The final mathematical model with simple flow contained four adjustable parameters (N1,Ni, F _cr andF _p ) and five fixed parameters.List of Symbols A _u m² inner surface of bioreactor's wall - A _ui m² i-th part of inner surface of bioreactor's wall - A _v m² outlet surface of bioreactor's wall - A _vi m² i-th part of outlet surface of bioreactor's wall - C _p kJ kg^–1 K^–1 heat capacity of liquid - C _pr kJ kg^–1 K^–1 heat capacity of bioreactor's wall - D h^–1 dilution rate - E °C °C^–1 h^–1 error of mathematical model - F _cr dm³s^–1 circulation flow in the model - F _p dm³ s^–1 back flow in the model - F _t dm³s^–1 inlet flow in the bioreactor - I °C intensity of temperature step, the difference in temperature between the temperature of the inlet liquid flow and the temperature of liquid in the bioreactor before the temperature step - K1 Wm^–2K^–1 heat transfer coefficient between the liquid and bioreactor's wall - K2 Wm^–2K^–1 heat transfer coefficient between the bioreactor's wall and air - m _s kg mass of bioreactor's wall - L m length of bioreactor - L _k m wetted perimeter of bioreactor - n min^–1 rotational speed of bioreactor - n _s number of temperature sensors - N1 number of cascades - Ni number of compartments inside the cascade - Nu Nusselt number - Pr Prandtl number - r _u m inner diameter of bioreactor - r _v m outside diameter of bioreactor - Re Reynolds number - s(t) step function - t s time - T °C temperature - T _c °C calculated temperature - T _m °C measured temperature - T _N1,Ni °C temperature of liquid in a defined compartment inside cascade - T _N1,S °C temperature of defined part of bioreactor's wall - T _S °C temperature of bioreactor's wall - T _v °C temperature of liquid in bioreactor - T _z °C temperature of surrounding air - V _t dm³ volume of liquid in the bioreactor Greek Symbols kJm^–1s^–1 K^–1 thermal conductivity of liquid in the bioreactor - kgm^–3 density of liquid in the bioreactor - m²s^–1 kinematic viscosity of liquid in the bioreactor Matrix Coefficient B - C - D - E B+C+D - G1 - G2 - G3 - A _ui - A _vi - Q ₁ - Q ₂ - Q ₃      

Thermoregulation,gas exchange,and ventilation in Adelie penguins (Pygoscelis adeliae)

Summary Adelie penguins (Pygoscelis adeliae) experience a wide range of ambient temperatures (T _a) in their natural habitat. We examined body temperature (T _b), oxygen consumption ( ), carbon dioxide production ( ), evaporative water loss ( ), and ventilation atT _a from –20 to 30 °C. Body temperature did not change significantly between –20 and 20°C (meanT _b=39.3°C).T _b increased slightly to 40.1 °C atT _a=30°C. Both and were constant and minimal atT _a between –10 and 20°C, with only minor increases at –20 and 30°C. The minimal of adult penguins (mean mass 4.007 kg) was 0.0112 ml/[g·min], equivalent to a metabolic heat production (MHP) of 14.9 Watt. The respiratory exchange ratio was approximately 0.7 at allT _a. Values of were low at lowT _a, but increased to 0.21 g/min at 30°C, equivalent to 0.3% of body mass/h. Dry conductance increased 3.5-fold between –20 and 30°C. Evaporative heat loss (EHL) comprised about 5% of MHP at lowT _a, rising to 47% of MHP atT _a=30°C. The means of ventilation parameters (tidal volume [VT], respiration frequency [f], minute volume [I], and oxygen extraction [ ]) were fairly stable between –20 and 10°C (VT did not change significantly over the entireT _a range). However, there was considerable inter- and intra-individual variation in ventilation patterns. AtT _a=20–30°C,f increased 7-fold over the minimal value of 7.6 breaths/min, and I showed a similar change. fell from 28–35% at lowT _a to 6% atT _a=30°C.Abbreviations C thermal conductance - EHL evaporative heat loss - oxygen extraction - f respiratory frequency - MHP metabolic heat production - evaporative water loss - LCT lower critical temperature - RE respiratory exchange ratio - T _a ambient temperature - T _b body temperature - rate of oxygen consumption - rate of carbon dioxide production - I inspiratory minute volume - VT tidal volume     

Maximal oxygen uptake, maximal voluntary isometric contraction and physical activity in young Danish adults

In a randomly selected sample of 88 men and 115 women, aged 23–27 years from Denmark, maximal oxygen uptake ( O_2max), maximal voluntary isometric contraction (MVC) in four muscle groups and physical activity were studied. The O_2max was 48.0 ml · min^–1 kg^–1 and 39.6 ml · min^–1 · kg^–1 for the men and the women, respectively. The MVC was 10% lower than in a comparable group of Danes of the same age and height studied 35 years ago. Only in men was sports activity directly related to O_2max (ml · min^–1 · kg^–1; r=0.31, P<0.01). The MVC of the knee extensors was related to O_2max in the men (r=0.31, P<0.01), but there was no relationship between the other measurements of MVC and O_2max. In the women O_2max (ml · min^–1 · kg^–1) was only related to body size, i.e. body mass index, percentage body fat and body mass [(r= –0.47, –0.48 (both P<0.001) and –0.34. (P<0.01), respectively)]. There were differences in O_2max in the men, according to education and occupation. Blue collar workers and subjects attending vocational or trade schools in 1983 had lower O_2max and more of them were physically inactive. In the women differences were also found, but there was no clear pattern among the groups. More of the women participated regularly in sports activity, but more of the men were very active compared to the women.     

Light dependent sediment-water exchange of dissolved reactive phosphorus and silicon in a producing microflora mat

Light dependent sediment-water exchange rates of dissolved reactive silicon (DRSi) and phosphorus (DRP) were studied on field station Archipel (3 m water depth) in Lake Grevelingen (SW Netherlands). Bell jars, either light or darkened, were fixed permanently over a productive microflora mat of mainly Navicula spp.; sediment-water exchange was monitored over an 11 days period. Gross primary production values in the mat amounted to 1000 mg C·m^–2·day^–1.In the dark bell jar, DRSi and DRP release rates from the sediment were ca. 275 and 85 mg·m^–2·day^–1, respectively. Release rates in the light bell jars were on average only 15% of these values. Parallel bell jar experiments under different environmental conditions indicate a direct relationship between the primary production figures and nutrient sediment-water exchange rates.Communication nr. 369 of the Delta Institute for Hydrobiological Research, Yerseke, the Netherlands. This paper was presented at the first International Workshop on phosphorus fractionation, availability and release of the Sediment Phosphorus Group, held in Vienna, 23–26 March, 1986.     

Effects of ambient temperature and altitude on ventilation and gas exchange in deer mice (Peromyscus maniculatus)

Summary The effects of different ambient temperatures (T _a) on gas exchange and ventilation in deer mice (Peromyscus maniculatus) were determined after acclimation to low and high altitude (340 and 3,800 m).At both low and high altitude, oxygen consumption ( ) decreased with increasingT _a atT _a from –10 to 30 °C. The was 15–20% smaller at high altitude than at low altitude atT _a below 30 °C.Increased atT _a below thermoneutrality was supported by increased minute volume ( ) at both low and high altitude. At mostT _a, the change in was primarily a function of changing respiration frequency (f); relatively little change occurred in tidal volume (V _T) or oxygen extraction efficiency (O₂EE). AtT _a=0 °C and below at high altitude, was constant due to decliningV _T and O₂EE increased in order to maintain high .At high altitude, (BTP) was 30–40% higher at a givenT _a than at low altitude, except atT _a below 10 °C. The increased at high altitude was due primarily to a proportional increase inf, which attained mean values of 450–500 breaths/min atT _a below 0 °C. The (STP) was equivalent at high and low altitude atT _a of 10 °C and above. At lowerT _a, (STPD) was larger at low altitude.At both altitudes, respiratory heat loss was a small fraction (<10%) of metabolic heat production, except at highT _a (20–30 °C).Abbreviations EHL evaporative heat loss - f respiration frequency - HL _a heat loss from warming tidal air - HL _e evaporative heat loss in tidal air - HL total respiratory heat loss - MHP metabolic heat production - O ₂ EE oxygen extraction efficiency - RQ respiratory quotient - T _a ambient temperature - T _b body temperatureT _lc lower critical temperature - carbon dioxide production - evaporative water loss - oxygen consumption - minute volume - V _T tidal volume