Solar heat gain in a desert rodent: unexpected increases with wind speed and implications for estimating the heat balance of free-living animals

We quantified metabolic power consumption as a function of wind speed in the presence and absence of simulated solar radiation in rock squirrels, Spermophilus variegatus, a diurnal rodent inhabiting arid regions of Mexico and the western United States. In the absence of solar radiation, metabolic rate increased 2.2-fold as wind speed increased from 0.25 to 4.0 m·s^-1. Whole-body thermal resistance declined 56% as wind speed increased over this range, indicating that body insulation in this species is much more sensitive to wind disruption than in other mammals. In the presence of 950 W·m^-2 simulated solar radiation, metabolic rate increased 2.3-fold as wind speed was elevated from 0.25 to 4.0 m·s^-1. Solar heat gain, calculated as the reduction in metabolic heat production associated with the addition of solar radiation, increased with wind speed from 1.26 mW·g^-1 at 0.25 m·s^-1 to 2.92 mW·g^-1 at 4.0 m·s^-1. This increase is opposite to theoretical expectations. Both the unexpected increase in solar heat gain at elevated wind speeds and the large-scale reduction of coat insulation suggests that assumptions often used in heat-transfer analyses of animals can produce important errors.Abbreviations absorptivity of coat to solar radiation - kinematic viscosity of air (mm²·s^-1) - reflectivity of coat to solar radiation - a r _B expected at zero wind speed (s·m^-1) - A _P projected surface area of animal on plane perpendicular to solar beam (cm²) - A _SKIN skin surface area (cm²) - b Coefficient describing change in r _B with change in square-root of wind speed (s^1.5·m^1.5) - d hair diameter (m) - d characteristic dimension of animal (m) - D _H thermal diffusivity of air (m²·s^-1) - E evaporative heat loss (W·m^-2) - I probability per unit coat depth that photon will strike hair - k constant equalling 1200 J·m^-3·°C^-1 - l _C coat depth m) - l _H hair length (m) - M metabolic rate (W·m^-2) - n density of hairs of skin (m^-2) - Q _A solar heat gain to animal (W·m^-2) - Q _I solar irradiance intercepted by animal (W·m^-2) - RQ respiratory quotient - r _A thermal resistance of boundary layer (s·m^-1) - r _B whole-body thermal resistance (s·m^-1) - r _E thermal resistance between animal surface and environment s·m^-1) - r _R radiative resistance (s·m^-1) - r _S sum of r _B and r _E at 0.25 m·s^-1 (s·m^-1) - r _T tissue thermal resistance s·m^-1) - T _AIR air temperature (°C) - T _B body temperature (°C) - T _E operative temperature of environment (°C) - T _ES standard operative temperature of environment (°C) - u wind speed (m·s^-1)     

Thermal dependence of contractile properties of single skinned muscle fibres from Antarctic and various warm water marine fishes including Skipjack Tuna (Katsuwonus pelamis) and Kawakawa (Euthynnus affinis)

Summary Single fast fibres and small bundles of slow fibres were isolated from the trunk muscles of an Antarctic (Notothenia neglecta) and various warm water marine fishes (Blue Crevally,Carangus melampygus; Grey Mullet,Mugil cephalus; Dolphin Fish,Coryphaena hippurus; Skipjack-tuna,Katsuwonus pelamis and Kawakawa,Euthynuus affinis). Fibres were chemically skinned with the nonionic detergent Brij 58.For warm water species, maximum Ca²⁺-activated tension (P ₀) almost doubled between 5–20°C with little further increase up to 30°C. However, when measured at their normal body temperatures,P ₀ values for fast fibres were similar for all species examined, 15.7–22.5 N · cm^–2. Ca²⁺-regulation of contraction was disrupted at temperatures above 15°C in the Antarctic species, but was maintained at up to 30°C for warm water fish.Unloaded (maximum) contraction speeds (V _max) of fibres were determined by the slacktest method. In general,V _max was approximately two times higher in white than red muscles for all species studied, except Skipjack tuna. For Skipjack tuna,V _max of superficial red and white fibres was similar (15.7 muscle lengths · s^–1 (L ₀ · s^–1)) but were 6.5 times faster than theV _max of internal red muscle fibres (2.4±0.2L ₀ · s^–1) (25°C). V _max forN. neglecta fast fibres at 0–5°C (2–3L ₀ · s^–1) were similar to that of warm water species measured at 10–20°C. However, when measured at their normal muscle temperatures, theV _max for the fast muscle fibres of the warm water species were 2–3 times higher than that forN. neglecta.In general,Q _{10(15–30°C)} values forV _max were in the range 1.8–2.0 for all warm water species studied except Skipjack tuna.V _max for the internal red muscle fibres of Skipjack tuna were much more temperature dependent (Q _{10(15–30°C)}=3.1) (P<0.01) than for superficial red or white muscle fibres. The proportion of slower red muscle fibres in tuna (28% for 1 kg Skipjack) is 3–10 times higher than for most teleosts and is related to the tuna's need to sustain high cruising speeds. We suggest that the 8–10°C temperature gradient that can exist in Skipjack tuna between internal red and white muscles allows both fibre types to contract at the same speed. Therefore, in tuna, both red and white muscle may contribute to power generation during high speed swimming.     

The integration of whole-root and cellular hydraulic conductivities in cereal roots

The hydraulic conductivities of excised whole root systems of wheat (Triticum aestivum L. cv. Atou) and of single excised roots of wheat and maize (Zea mays L. cv. Passat) were measured using an osmotically induced back-flow technique. Ninety minutes after excision the values for single excised roots ranged from 1.6·10^-8 to 5.5·10^-8 m·s^-1·MPa^-1 in wheat and from 0.9·10^-8 to 4.8·10^-8 m·s^-1·MPa^-1 in maize. The main source of variation was a decrease in the value as root length increased. The hydraulic conductivities of whole root systems, but not of single excised roots, were smaller 15 h after excision. This was not caused by occlusion of the xylem at the cut end of the coleoptile. The hydraulic conductivities of epidermal, cortical and endodermal cells were measured using a pressure probe. Epidermal and cortical cells of both wheat and maize roots gave mean values of 1.2·10^-7 m·s^-1·MPa^-1 but in endodermal cells (measured only in wheat) the mean value was 0.5·10^-7 m·s^-1·MPa^-1. The cellular hydraulic conductivities were used to calculate the root hydraulic conductivities expected if water flow across the root was via transcellular (vacuole-to-vacuole), apoplasmic or symplasmic pathways. The results indicate that, in freshly excised roots, the bulk of water flow is unlikely to be via the transcellular pathway. This is in contrast to our previous conclusion (H. Jones, A.D. Tomos, R.A. Leigh and R.G. Wyn Jones 1983, Planta 158, 230–236) which was based on results obtained with whole root systems of wheat measured 14–15 h after excision and which probably gave artefactually low values for root hydraulic conductivity. It is now concluded that, near the root tip, water flow could be through a symplasmic pathway in which the only substantial resistances to water flow are provided by the outer epidermal and the inner endodermal plasma membranes. Further from the tip, the measured hydraulic conductivities of the roots are consistent with flow either through the symplasmic or apoplasmic pathways.Symbols L _{p, cell} cell hydraulic conductivity - L _{p, root} root hydraulic conductivity - L _{p, root} calculated root hydraulic conductivity - root reflection coefficient     

Changes in intra-abdominal pressure, trunk muscle activation and force during isokinetic lifting and lowering

Intra-abdominal pressure (IAP), force and electromyographic (EMG) activity from the abdominal (intra-muscular) and trunk extensor (surface) muscles were measured in seven male subjects during maximal and sub-maximal sagittal lifting and lowering with straight arms and legs. An isokinetic dynamometer was used to provide five constant velocities (0.12–0.96 m·s^–1) of lifting (pulling against the resistance of the motor) and lowering (resisting the downward pull of the motor). For the maximal efforts, position-specific lowering force was greater than lifting force at each respective velocity. In contrast, corresponding IAPs during lowering were less than those during lifting. Highest mean force occurred during slow lowering (1547 N at 0.24 m·s^–1) while highest IAP occurred during the fastest lifts (17.8 kPa at 0.48–0.96 m·s^–1). Among the abdominal muscles, the highest level of activity and the best correlation to variations in IAP (r=0.970 over velocities) was demonstrated by the transversus abdominis muscle. At each velocity the EMG activity of the primary trunk and hip extensors was less during lowering (eccentric muscle action) than lifting (concentric muscle action) despite higher levels of force (r between –0.896 and –0.851). Sub-maximal efforts resulted in IAP increasing linearly with increasing lifting or lowering force (r=0.918 and 0.882, respectively). However, at any given force IAP was less during lowering than lifting. This difference was negated if force and IAP were expressed relative to their respective lifting and lowering maxima. It appears that the IAP increase primarily accomplished by the activation of the transversus abdominis muscle can have the dual function of stabilising the trunk and reducing compression forces in the lumbar spine via its extensor moment. The neural mechanisms involved in sensing and regulating both IAP and trunk extensor activity in relation to the type of muscle action, velocity and effort during the maximal and sub-maximal loading tasks are unknown.     

Response of left ventricular diastolic filling to graded exercise relative to the lactate threshold

During incremental exercise, the left ventricular ejection fraction increases up to the intensity of the anaerobic threshold and tends to level off at higher exercise intensities. Since there is a correlation between the response of peak filling rate and ejection fraction to exercise, this study was conducted to determine whether the response of left ventricular diastolic function is similar to the response of systolic function relative to lactate threshold. Twelve healthy men performed two exercise tests on a cycle ergometer. In the first test, lactate threshold and maximal power output were determined. In the second exercise test, gated radionuclide ventriculography was performed at rest, at the lactate threshold intensity, and at peak exercise to measure ejection fraction and peak filling rate. Ejection fraction increased significantly from rest [mean (SD): 62 (5)%] to lactate threshold [76 (7) %] and did not change significantly from lactate threshold to peak exercise [77 (7)%]. Likewise, peak filling rate (normalized for stroke counts) increased from resting [6.1 (0.9)V _s · s^–1] to lactate threshold [9.4 (1.8)V _s · s^–1] and did not change significantly from lactate threshold to peak exercise [9.6 (2.9)V _s · s^–1]. There was no correlation between the change in peak filling rate and the change in ejection fraction from rest to lactate threshold. Thus, during incremental exercise, left ventricular diastolic function responds qualitatively similar to systolic function.     

Modification of myo-electric power spectrum in fatigue from 15% maximal voluntary contraction of human elbow flexor muscles, to limit of endurance: reflection of conduction velocity variation and/or centrally mediated mechanisms?

Isometric flexion of the right elbow at 15% of the maximal voluntary contraction (MVC) was maintained to the limit of endurance (elbow angle 135°). The surface electromyogram (EMG) of the brachioradialis (BR) and biceps brachii (BB) muscles was recorded for calculation of conduction velocity (CV) by the cross-correlation method, and determination of median frequency (fm) and root mean square (rms) amplitude. Perceived exertion was rated for both muscles, and heart rate and blood pressure were measured. The EMG of ten brief 15% MVC contractions distributed over a 30-min recovery period was also recorded. Eleven males in their twenties volunteered for the investigation. The average endurance time was 906 (SD 419) s. Mean CV for the unfatigued muscles was 4.2 (SD 0.41) m·s^–1 (BR), and 4.3 (SD 0.29) m·s^–1 (BB). The contraction caused a significant decrease in CV of BR (12%,P<0.001) whereas CV variation of BB remained insignificant. Concurrently the meanf _m of both muscles dropped to approximately 66% of their initial values and their average rms amplitudes grew by approximately 380% (BR and BB:P<0.001, both parameters). The 1st min of recovery lowered the rms amplitudes by approximately 60% (BR and BB:P<0.01), while thef _m increased to approximately 88% of the initial recording (BR,P<0.01; BB,P<0.05). The accompanying small increases in CV were beyond the level of significance. Over the next 29 min a significant parallel restitution inf _m and CV took place; changes inf _m evidenced a simple one to one reflection of relative CV variation. A similar uncomplicated linear causality between relative changes in CV andf _m was hypothesized for the endurance contraction. Consequently, the 12% CV decrease of the BR accounted for only one-third of the fatigue inducedf _m reduction of 33%, while two-thirds were assumed to be attributable to centrally mediated regulatory interventions in motor unit (MU) performance. Independent of contributions from the virtually unchanged CV, thef _m of the BB muscle decreased by 35%; from one subject exhibiting a remarkably manifest burst-type pattern of MU activity it is argued that synchronization/grouping of MU firing predominantly determined the power redistribution in the BB spectrum.     

A study of excitatory efferent fibres in the intestinal nerve of the fowl (Gallus domesticus)

• 1.1. The intestinal nerve of the fowl was studied in vitro.
• 2.2. A significantly larger amplitude spike discharge was recorded in side branches of the nerve which innervate the gut when the aboral end of the main nerve trunk was stimulated than when the oral end was stimulated.
• 3.3. Postganglionic autonomic neurones innervating the smooth muscle of the ileum are not located in the intestinal nerve. Evidence is presented, however, supporting the idea that such neurones innervating the rectum are located in the rectal position of the nerve.
• 4.4. The increase in intraluminal pressure and circular muscle tension in the ileum was greater following aboral nerve stimulation than following oral nerve stimulation.
• 5.5. It is suggested that excitatory efferent nerve fibres ascend the intestinal nerve to innervate the ileum.

     

Effects of temperature on the properties of primary auditory fibres of the spectacled caiman,Caiman crocodilus (L.)

Summary The effect of temperature on the response properties of primary auditory fibres in caiman was studied. The head temperature was varied over the range of 10–35 ° C while the body was kept at a standard temperature of 27 °C (T_s). The temperature effects observed on auditory afferents were fully reversible. Below 11 °C the neural firing ceased.The mean spontaneous firing rate increased nearly linearly with temperature. The slopes in different fibres ranged from 0.2–3.5 imp s^–1 °C^–1. A bimodal distribution of mean spontaneous firing rate was found (<20 imp s^–1 and >20 imp s^–1 at T_s) at all temperatures.The frequency-intensity response area of the primary fibres shifted uniformly with temperature. The characteristic frequency (CF) increased nearly linearly with temperature. The slopes in different fibres ranged from 3–90 Hz °C^–1. Expressed in octaves the CF-change varied in each fibre from about O.14oct °C^–1 at 15 °C to about 0.06 oct °C^–1 at 30 °C, irrespective of the fibre's CF at T_s. Thresholds were lowest near T_s. Below T_s the thresholds decreased on average by 2dB°C^–1, above T_s the thresholds rose rapidly with temperature. The sharpness of tuning (Q_10db) showed no major change in the temperature range tested.Comparison of these findings with those from other lower vertebrates and from mammals shows that only mammalian auditory afferents do not shift their CF with temperature, suggesting that a fundamental difference in mammalian and submammalian tuning mechanisms exists. This does not necessarily imply that there is a single unifying tuning mechanism for all mammals and another one for non-mammals.Abbreviations BF best frequency: frequency of maximal response at an intensity 10 dB above the CF-threshold - CF characteristic frequency - FTC frequency threshold curve, tuning curve - T _s standard temperature of 27 °C     

Respiration rates of stems at different heights and their sensitivity to temperature in two broad-leaved trees in Beijing

该研究采用红外气体分析法(IRGA)于2013年3–12月原位测定了北京市东升八家郊野公园中2个主要阔叶树种(槐(Sophora japonica)、旱柳(Salix matsudana))3个高度上的枝干呼吸(Rw)日进程,旨在量化Rw的种间差异,探索种内Rw及其温度敏感系数(Q10)的时间动态和垂直分布格局。研究结果显示:(1)Rw在不同树种之间差异明显,相同月份(4月份除外)槐Rw是旱柳的1.12(7月)–1.79倍(5月)。两树种枝干表面CO2通量速率均表现出明显的单峰型季节变化,峰值分别出现在7月((5.13±0.24)μmol·m–2·s–1)和8月((3.85±0.17)μmol·m–2·s–1)。同一树种在生长月份内的平均呼吸水平显著高于非生长季,但其Q10值季节变化趋势与之相反。(2)RW随测量高度的增加而升高,并在3个高度上表现出不同的日变化规律:其中,树干基部及胸高位置为单峰格局,而一级分枝处的呼吸速率在一天内存在两个峰值,中间出现短暂的"午休"现象。温度是造成一天内呼吸变化的主要原因。此外,顶部Rw及其对温度的敏感程度明显高于基部。温度本身和Q10值差异可在一定程度上解释RW的垂直梯度变化。(3)在生长月份,单位体积木质组织的日累积呼吸速率(mmol·m–3·d–1)与受测部位直径倒数(D–1)呈极显著正相关关系。单位面积(μmol·m–2·s–1)可准确表达两树种在生长期间的RW水平,能合理有效地比较不同个体的呼吸差异及同一个体的时空变异。这些结果表明,采用局部通量法上推至树木整体呼吸时,应全面考虑Rw的时、空变异规律,并选择恰当的表达单位,以减小估测误差。     

Two stable electron-conformational states of photoactivated reaction center and their observation in primary donor recovery kinetics

We investigated the peculiarity of primary donor recovery kinetics in the reaction centers from the purple bacteriaRb. Sphaeroides at low levels of their cw photoactivation. A pronounced biphasity of the relaxation kinetics was found for the total light activating intensity <5×10¹² quanta·cm^-2·s^-1. The effect was attributed to strong dependence of an electron transfer rate constant for the reactionP ⁺Q _infA ^pup- Q_B P ⁺Q_AQ _infB ^sup- upon the RC conformational state controlled by the light. We showed the existence of two different electron-conformational states for the photoexcited RC. The first reveals itself at low intensity of cw photoactivation while the second becomes actual under the intensity >5×10¹² quanta · cm^-2 · s^-1.     

Myo-electric fatigue manifestations revisited: power spectrum, conduction velocity, and amplitude of human elbow flexor muscles during isolated and repetitive endurance contractions at 30% maximal voluntary contraction

A brief survey of the literature on manifestations of myo-electric fatigue has disclosed a surprisingly sharp conflict between early studies, focusing on neuromotor regulatory mechanisms, and more recent studies which stress the determinant influence of local metabolism and skewed homeostasis. Favoured explanations concerning changes in the electromyographic (EMG) spectrum were synchronization/grouping of motor unit (MU) firing and conduction velocity (CV) decreases of the action potential propagation. The notion of mutual exclusivity interwoven with these theories prompted us to reinvestigate the EMG of moderate level, static endurance contraction. Ten men in their twenties performed isometric elbow flexion (elbow angle 135°) at 30%6 maximal voluntary contraction (MVC), and the surface EMG of the brachioradialis (BR) and biceps brachii (BB) muscles was recorded. Initially the CV — determined by cross-correlation — was 4.3 m · s^–1 (BR) and 4.6 m · s^–1 (BB). At exhaustion the CV of the BR muscle had declined by 33%, roughly twice the decrease of the BB CV. Substantially larger relative median frequency (f _m) reductions of 50% (BR) and 43% (BB) were found. Simultaneously, the root-mean-square amplitudes grew by 150% (BR) and 120% (BB). All changes during contraction reached the same level of significance (P<0.001, both muscles). From the largely uniform relative increases inf _m and CV during the last 4 min of a 5-min recovery period, variations in CV were suggested to produce equivalent shifts inf _m. The gradually increasing discrepancies between relative decreases inf _m and CV during contraction presumably reflected centrally mediated regulation of MU firing patterns (notably synchronization). After the 5-min recovery another 11 endurance contractions at 30% MVC were executed, separated by 5-min intervals. The series of contractions reduced the endurance time to one-third of the 153 s initially sustained, while the terminal CV recordings increased by 1.0 (BR) and 0.6 (BB) m · s^–1, and the terminalf _m increased by 24 (BR) and 14 (BB) Hz. The relative CV decreased in direct proportion to the endurance time and thef _m decreases varied with the CV; the findings did not support a causal link between CV decrease (signifying impaired fibre excitability) and the force failure of exhaustion.     

A Histochemical Study of the Gas Gland Innervation in the Atlantic God,Gadus morhua

A histochemical study was made of the distribution of catecholamines and cholinesterases in two autonomic ganglia closely associated with the swimbladder of the Atlantic cod, Gadus morhua. The “swimbladder nerve ganglion” comprised large (40 μm) neurones, the majority of which are positive for both catecholamines and acetylcholinesterase. It is argued that these neurones are mainly adrenergic postganglionic elements of sympathetic pathways which pass through the vago-sympathetic trunk. The “gas gland ganglion” comprised small (20 μm) neurones, positive for acetylcholinesterase but showing no catecholamine reaction. It is argued that these neurones are cholinergic postganglionic elements of the parasympathetic vagal innervation of gas gland cells.     

Flight of the honey bee VII: metabolic power versus flight speed relation

The existing experimental data on metabolic power P _m of honey bees are critically discussed, partly corrected for real flight conditions and plotted as a function of flight speed v. New wind tunnel measurements of tethered flight under near-natural conditions are added in the range 3.3<v<5.1 m·s^-1, derived from exhaustion flight measurements. Within this small sector the latter measurements can be characterised by a linear correlation: P _m(mW)=6.72v (m·s^-1)+13.83, the slope of which is significantly different from zero. The over-all P _m(v) curve is significantly not a straight line of zero slope but a U-shaped minimum curve and may be approximated by a second-order polynom: P _m=49.2-8.9v+1.5v ². The same is true for relative metabolic power, P _{m rel (e)} related to empty body mass of 76.5 mg: P _{m rel(e)}=630.0-114.0v+19.2v ² (P _m in mW: P _{m rel} in mW·g^-1; v in m·s^-1). The data support the existence of a U-shaped power-versus-speed curve in bees.Abbreviations bm body mass (mg) - f full - e empty - mu muscles - P _m (mJ·s^-1=mW) metabolic power (input) - P _{m rel} (mW·g^-1) relative metabolic power - P _mec (mW) mechanical power (output) - efficiency (of the flight musculature) - t(s) flight time - v (m·s^-1) relative speed between bee and air     

Modification by temperature of conduction and ganglionic transmission in the gastropod nervous system

The pedal ganglia of the terrestrial gastropod Ariolimax contain junctions between nerve fibers which are shown to be preferential points of fatigue and which exhibit facilitation (summation) of preganglionic impulses to produce a postganglionic spike. These characteristics in conjunction with others previously reported (reversible susceptibility to nicotine, convergence of preganglionic impulses, and inhibition of transmission through setting up a refractory state in the postganglionic fiber) are considered sufficient to indicate synaptic transmission in the pedal ganglia. The mean conduction velocity of the fastest fibers in the pedal nerves is 0.52 meter per second for preganglionic and 0.50 meter per second for postganglionic fibers at 7.56°C. The conduction rates at 21.76°C. are respectively 0.80 meter per second and 0.83 meter per second. The mean ganglionic delay is 0.033 second at 7.56°C. and 0.019 second at 21.76°C. The mean Q₁₀'s for conduction velocity are thus 1.37 for preganglionic and 1.42 for postganglionic fibers. The mean Q₁₀ for ganglionic delay is 1.49. If the assumption is made that the Q₁₀ for ganglionic delay is that of a limiting reaction, this figure then represents a value below which the Q₁₀ for synaptic delay is statistically improbable.     

Prothrombin in Normal Human Cerebrospinal Fluid Originates from the Blood

In spite of the fact that prothrombin is produced by cells within the central nervous system, its presence in the cerebrospinal fluid (CSF) has not been investigated. We determined the concentration of prothrombin in CSF with reference to the concentration in plasma in paired samples from 18 normal control patients and 4 patients with relapsing-remitting type of multiple sclerosis (MS). The newly developed ELISA was very specific (no cross-reactivity with thrombin) and sensitive (detection limit—0.7 ng/ml) with an imprecision of CV = 8.3% (intraseries) and 7.0% (interassay). The mean prothrombin concentration in normal CSF was 0.55 mg/l (CV ± 33%, range: 0.28–0.93 mg/l), in normal plasma 121.8 mg/l ± 21%, resulting in a mean CSF/plasma concentration quotient (Q_Proth)—4.5 · 10^–3 (CV ± 35%, range: 2.1–8.3 · 10^–3) corresponding to a mean albumin quotient in this group of subjects of Q_Alb = 5.8 · 10^–3. Due to the Q_Proth and the molecular weight of prothrombin (72 kDa)—similar to that of albumin—we conclude that prothrombin in normal human CSF originates predominantly (>95%) from blood. The enzymatic activity in CSF is conserved. Comparable results obtained in MS patients with only few small MRI lesions suggest that local chronic inflammatory disease of the central nervous system does not influence prothrombin concentration in the CSF if the blood-CSF barrier function is normal.     

Strain selection,medium development and scale-up of toyocamycin production by streptomyces chrestomyceticus

The batch productivity (Q _TM) of the production of the nucleoside antibiotic toyocamycin (TM) by Streptomyces chrestomyceticus was increased ten-fold by selection of a UV generated mutant, optimization of pH, increasing incubation temperature from 28 °C to 36 °C, and addition of soy oil. Initial high oxygen transfer rates stimulated Q _TM maxima two-fold. Antibiotic production by the mutant strain, U190, however, appeared more shear sensitive than the parent culture FCRF 341 with maximum antibiotic titer being inversely related to impellor tip velocity, T _v . For this reason, scale-up could not be done at constant P/V or constant volumetric oxygen transfer. Instead, programming of impeller speed was evaluated in order to maintain optimal impeller tip velocity during scale-up. It was found that a low constant T _v maintained in scale-up in geometrically similar vessels was most beneficial for duplication of optimal antibiotic productivity, Q _TM. Pilot fermentations (120 dm³ scale) were used to determine coefficients of Q _TM variation from oxygen uptake rate (OUR) and total CO₂ evolution data for monitoring of Q _TM variation during scale-up to the 12,000 dm³ scale. This technique allowed for on-line prediction of antibiotic titer and Q _TM from fermentor exhaust gas data.List of Symbols A scale constant - B shape constant - C location of maximum constant - D m impeller diameter (m) - H m liquid height (m) - OTR MmolO₂·(dm³)^–1min^–1 oxygen transfer rate - OUR MmolO₂·(dm³)^–1min^–1 oxygen uptake rate - PCV cm³ packed cell volume - P/V watts/dm³ volumetric power consumption - Q 1 · min^–1 corrected to standard conditions of temperature, pressure aeration rate - Q _TM g/(cm³ · h) or kg/(m³ · h) antibiotic productivity - T m tank diameter - T _mix s mixing time - T _v cm · s^–1 impeller tip velocity - TM g/cm³ Toyocamycin concentration - TNP Tricyclic nucleoside phosphate     

Effects of dissolved oxygen concentration on lipase production by Rhizopus delemar

Summary The influence of the concentration of oxygen on lipase production by the fungus Rhizopus delemar was studied in different fermenters. The effect of oxygen limitation ( 47 mol/l) on lipase production by R. delemar is large as could be demonstrated in pellet and filamentous cultures. A model is proposed to describe the extent of oxygen limitation in pellet cultures. Model estimates indicate that oxygen is the limiting substrate in shake flask cultures and that an optimal inoculum size for oxygen-dependent processes can occur.Low oxygen concentrations greatly negatively affect the metabolism of R. delemar, which could be shown by cultivation in continuous cultures in filamentous growth form (D_optimal=0.086 h^-1). Continuous cultivations of R. delemar at constant, low-oxygen concentrations are a useful tool to scale down fermentation processes in cases where a transient or local oxygen limitation occurs.Symbols and Abbreviations CO Oxygen concentration in the gas phase at time = 0 (kg·m^-3) - C_{O 2i} Oxygen concentration at the pellet liquid interface (kg·m^-3) - C_{O 2i} Oxygen concentration in the bulk (kg·m^-3) - D Dilution rate (h^-1) - ID_{O 2} Diffusion coefficient for oxygen (m²·s^-1) - dw Dry weight of biomass (kg) - f Conversion factor (rs _{O 2} to oxygen consumption rate per m³) (-) - k Radial growth rate (m·s^-1) - K Constant - kla Volumetric mass transfer coefficient (s^-1) - klA Oxygen transfer rate (m^-3·s^-1) - kl Mass transfer coefficient (m·s^-1) - K _{O 2} Affinity constant for oxygen (mol·m^-3) - K _w Cotton plug resistance (m^-3·s^-1) - M Henry coefficient (-) - NV Number of pellets per volume (m^-3) - R Radius (m) - RO Radius of oxygen-deficient core (m) - RQ Respiration quotient (mol CO₂/mol O₂) - rs _{O 2} Specific oxygen consumption rate per dry weight biomass (kg O₂·s^-1[kg dw]^-1) - rX Biomass production rate (kg·m^-3·s^-1) - SG Soytone glucose medium (for shake flask experiments) - SG ₄ Soytone glucose medium (for tower fermenter and continuous culture experiments) - V Volume of medium (m^-3) - X Biomass (dry weight) concentration (kg·m^-3) - XR _o Biomass concentration within RO for a given X (kg·m^-3) - Y _{O 2} Biomass yield calculated on oxygen (kg dw/kg O₂) - Thiele modulus - Efficiency factor =1-(RO/R)³ (-) - Growth rate (m^-1·s^-1·kg^1/3) - Dry weight per volume of pellet (kg·m^-3)     

Cross-flow filtration as a method of separating fungal cells and purifying the polysaccharide produced

Cross-flow filtration (CFF) has been investigated as a method of separating filamentously growing fungal cells and purifying the polysaccharide produced. The effects of transmembrane pressure, module geometry (e.g. channel height or tube diameter), tangential feed velocity and cell as well as polysaccharide concentration are discussed. Apart from these experiments, influences by the recirculation pump used are shown.List of Symbols b _f fouling index - b factor refering to the behaviour of the sublayer - C kg · m^–3 concentration - C _g kg · m^–3 solute concentration at the membrane - C _b kg · m^–3 solute concentration in the bulk phase - D s_-1 shear rate - k m · s^–1 mass-transfer coefficient - K mPa · sⁿ consistency index - n flow behaviour index - P _w m³ · s^–1 · m^–2 rate of permeation - P _w1 m³ · s^–1 · m^–2 rate of permeation at 1 minute - P _w m³ · s^–1 · m^–2 rate of permeation at the beginning - p Pa pressure - Q m² largest cross-section of a particle - q m² smallest cross-section of a particle - Re Reynolds number - R _f ^–1 fouling resistance - R _m m^–1 membrane resistance - t s time - w m · s^–1 tangential feed velocity Greek Symbols friction factor - pTM Pa transmembrane pressure - mPa · s shear viscosity - _sp specific viscosity (rel. increase of viscosity _sp=_rel-1) - [] m³· kg^–1 intrinsic viscosity - _w m² · s^–1 kinematic viscosity - kg · m^–3 density Indices b bulk - cell cells - f fouling - g gelling - PS polysaccharide - rel relative - sp specific - w water     

Organic reduction of tapioca wastewaters using modified RBC

A modified Rotating Biological Contactor (RBC) was used for the treatability studies of synthetic tapioca wastewaters. The RBC used was a four stage laboratory model and the discs were modified by attaching porous nechlon sheets to enhance biofilm area. Synthetic tapioca wastewaters were prepared with influent concentrations from 927 to 3600 mg/l of COD. Three hydraulic loads were used in the range of 0.03 to 0.09 m³·m^–2·d^–1 and the organic loads used were in the range of 28 to 306 g COD· m^–2·d^–1. The percentage COD removal were in the range from 97.4 to 68. RBC was operated at a rotating speed of 18 rpm which was found to be the optimal rotating speed. Biokinetic coefficients based on Kornegay and Hudson models were obtained using linear analysis. Also, a mathematical model was proposed using regression analysis.List of Symbols A m² total surface area of discs - d m active depth of microbial film onany rotating disc - K _s mg ·l^–1 saturation constant - P mg·m^–2·^–1 area capacity - Q l·d^–1 hydraulic flow rate - q m³·m^–2·d^–1 hydraulic loading rate - S ₀ mg·l^–1 influent substrate concentration - S _e mg·l^–1 effluent substrate concentration - w rpm rotational speed - V m³ volume of the reactor - X _f mg·l^–1 active biomass per unit volume ofattached growth - X _s mg·l^–1 active biomass per unit volume ofsuspended growth - X mg·l^–1 active biomass per unit volume - Y _s yield coefficient for attachedgrowth - Y _A yield coefficient for suspendedgrowth - Y yield coefficient, mass of biomass/mass of substrate removed Greek Symbols hr mean hydraulic detention time - (_max)_A d^–1 maximum specific growth rate forattached growth - (_max)_s d^–1 maximum specific growth rate forsuspended growth - _max d^–1 maximum specific growth rate - d^–1 specific growth rate - _v mg·l^–1·hr^–1 maximum volumetric substrateutilization rate coefficient     

Assessment of cardiac output from noninvasive determination of arterial pressure profile in subjects at rest

The stroke volume of the left ventricle (SV) was calculated from noninvasive recordings of the arterial pressure using a finger photoplethysmograph and compared to the values obtained by pulsed Doppler echocardiography (PDE). A group of 19 healthy men and 12 women [mean ages: 20.8 (SD 1.6) and 22.2 (SD 1.6) years respectively] were studied at rest in the supine position. The ratio of the area below the ejection phase of the arterial pressure wave (A _s) to SV, as obtained by PDE, yielded a calibration factor dimensionally equal to the hydraulic impedance of the system (Z _ao =A _s ·SV ^–1). TheZ _ao amounted on average to 0.062 (SD 0.018) mmHg · s · cm^–3 for the men and to 0.104 (SD 0.024) mmHg · s · cm^–3 for the women. TheZ _ao was also estimated from the equation:Z _ao = a · (d + b ·HR + c ·PP + e ·MAP)^–1, whereHR was the heart rate,PP the pulse pressure,MAP the mean arterial pressure and the coefficients of the equation were obtained by an iterating statistical package. The value ofZ _ao thus obtained allowed the calculation of SV from measurements derived from the photoplethysmograph only. The mean percentage error between the SV thus obtained and those experimentally determined by PDE amounted to 14.8 and 15.6 for the men and the women, respectively. The error of the estimate was reduced to 12.3 and to 11.1, respectively, if the factorZ _ao, experimentally obtained from a given heart beat, was subsequently applied to other beats to obtain SV from theA _s measurement in the same subject.