scholarly journals A Transient Method for Determining Thermal Diffusivity of Tobacco Stems

1989 ◽  
Vol 14 (5) ◽  
pp. 321-326
Author(s):  
NN Barthakur ◽  
NP Arnold
Keyword(s):  
Thermal Diffusivity ◽  
Cooling Curves ◽  
Microwave Generator ◽  
Unsteady State ◽  
Transient Method ◽  
Flow Rates ◽  
Heating And Cooling ◽  
Air Stream ◽  
Stem Temperature

AbstractA microwave generator and a closed-circuit wind tunnel were used to measure the thermal diffusivity of tobacco (Nicotianatabacum L.) stems in vivo by the unsteady-state method. A simple mathematical model for heat flow, based on Fourier's heat-conduction equation and Newton's law of cooling, was used in this study. The microwave method was found to be relatively rapid as both heating and cooling of a cylindrical stem in an air stream could be completed in approximately 30 minutes for thermal-diffusivity determinations. Thermal-diffusivity value of the tobacco stems, containing 94 % moisture and a mean stem temperature of 30°C, was found to be (1.38 ± 0.06) × 10-7 m2 s-1. The coefficient of variation for the measurements did not exceed 1.4 % as determined through the analysis of cooling curves for five different air-flow rates over the stems. This study showed that the microwave technique could be effectively used to determine both accurately and reliably the thermal diffusivity of tobacco stems in vivo.

A Liquid Desiccant System for Solar Cooling and Dehumidification

2004 ◽  
Vol 126 (3) ◽  
pp. 879-885 ◽  
Author(s):  
K. Gommed ◽  
G. Grossman
Keyword(s):  
Direct Contact ◽  
Cooling System ◽  
Low Cost ◽  
Cooling Water ◽  
Ambient Air ◽  
Low Grade ◽  
Liquid Desiccant ◽  
Flow Rates ◽  
Heating And Cooling ◽  
Air Stream

The growing demand for air conditioning, particularly in hot and humid climates has caused a significant increase in demand for energy resources. A promising solar technology with potential to alleviate the problem is an open absorption system, where humidity is absorbed directly from the air to be treated by direct contact with the absorbent. The absorbent is then regenerated, again in direct contact with an external air stream, at relatively low temperatures of the heat source. The paper describes a study of a liquid desiccant cooling system designed to air-condition a group of offices on the top floor of a building in the Mediterranean city of Haifa, Israel. The system is capable of using as its source of power low-grade solar heat, of the type obtainable from low-cost flat plate collectors, and has a potential to provide both cooling and dehumidification in variable ratios, as required by the load. Several cycle variations have been considered, corresponding to different design options. A parametric study shows that entrance conditions of the ambient air significantly affect the heat and mass transfer occurring during the dehumidification process. The temperatures and flow rates of the heating and cooling water and the flow rates of solution through the dehumidifier and regenerator affect the humidity of the supply air delivered to the conditioned space, and show an optimum in certain cases.

TCA cycle flux estimates from NMR- and GC-MS-determined [13C]glutamate isotopomers in liver

1997 ◽  
Vol 272 (6) ◽  
pp. C2049-C2062 ◽  
Author(s):  
J. A. Vogt ◽  
D. M. Yarmush ◽  
Y. M. Yu ◽  
C. Zupke ◽  
A. J. Fischman ◽  
...  
Keyword(s):  
Tca Cycle ◽  
Gas Chromatography Mass Spectrometry ◽  
Flow Rates ◽  
13C Nuclear Magnetic Resonance ◽  
Two Factors ◽  
Subsequent Measurement ◽  
System 1 ◽  
Relative Flow

Infusion of 13C-labeled lactate into rabbits and the subsequent measurement of glutamate isotopomers by 13C nuclear magnetic resonance (NMR) spectroscopy enables one to calculate relative flow rates associated with the tricarboxylic acid (TCA) cycle, albeit with a lower precision than one would obtain using a perfused organ. Two factors contribute to the lower precision in the determination of relative flow rates for the in vivo system: 1) a poorly defined pyruvate input and 2) low levels of 13C-enriched oxaloacetate and acetyl-CoA isotopomers, which give rise to weaker glutamate isotopomer NMR signals. To help overcome these limitations, we introduce a procedure to 1) include experimental data from gas chromatography-mass spectrometry (GC-MS) and 2) account for the uncertainty in the labeling of the input to pyruvate by creating the labeling as a measurement that is subject to measurement error. The effects of the uncertainties in the input labeling, NMR data, and MS data are evaluated via a Monte Carlo method. The change in the precision of the relative fluxes for the cases of high/low NMR and high/low MS precision is given. An uncertainty in the lactate measurements of up to 10% does not add significantly to the imprecision of the relative flow rates.

scholarly journals Assessment of Lentiviral Vector Mediated CFTR Correction in Mice Using an Improved Rapid in vivo Nasal Potential Difference Measurement Protocol

2021 ◽  
Vol 12 ◽  
Author(s):  
P. Cmielewski ◽  
J. Delhove ◽  
M. Donnelley ◽  
D. Parsons
Keyword(s):  
Ion Transport ◽  
Lentiviral Vector ◽  
Chloride Transport ◽  
Diagnostic Technique ◽  
Potential Difference ◽  
Third Generation ◽  
Flow Rates ◽  
Measurement Protocol ◽  
Nasal Potential Difference

Cystic Fibrosis (CF) is caused by a defect in the CF transmembrane conductance regulator (CFTR) gene responsible for epithelial ion transport. Nasal potential difference (PD) measurement is a well established diagnostic technique for assessing the efficacy of therapies in CF patients and animal models. The aim was to establish a rapid nasal PD protocol in mice and quantify the efficacy of lentiviral (LV) vector-based CFTR gene therapy. Anaesthetised wild-type (WT) and CF mice were non-surgically intubated and nasal PD measurements were made using a range of buffer flow rates. Addition of the cAMP agonist, isoproterenol, to the buffer sequence was then examined. The optimised rapid PD technique was then used to assess CFTR function produced by second and third generation LV-CFTR vectors. V5 epitope tagged-CFTR in nasal tissue was identified by immunohistochemistry. When intubated, mice tolerated higher flow rates. Isoproterenol could discriminate between WT and CF mice. Improved chloride transport was observed for the second and third generation LV-CFTR vectors, with up to 60% correction of the cAMP-driven chloride response towards WT. V5-CFTR was located in ciliated epithelial cells. The rapid PD technique enables improved functional assessment of the bioelectrical ion transport defect for both current and potential CF therapies.

Vascular peripheral resistance and compliance in the lobster Homarus americanus

1997 ◽  
Vol 200 (3) ◽  
pp. 477-485 ◽  
Author(s):  
J Wilkens ◽  
G Davidson ◽  
M Cavey
Keyword(s):  
Striated Muscle ◽  
Peripheral Resistance ◽  
Systolic Pressure ◽  
Body Part ◽  
Homarus Americanus ◽  
Arterial System ◽  
Flow Rates ◽  
Flow Through ◽  
Lateral Walls

The peripheral resistance to flow through each arterial bed (in actuality, the entire pathway from the heart back to the pericardial sinus) and the mechanical properties of the seven arteries leaving the lobster heart are measured and compared. Resistance is inversely proportional to artery radius and, for each pathway, the resistance falls non-linearly as flow rate increases. The resistance of the hepatic arterial system is lower than that predicted on the basis of its radius. Body-part posture and movement may affect the resistance to perfusion of that region. The total vascular resistance placed on the heart when each artery is perfused at a rate typical of in vivo flow rates is approximately 1.93 kPa s ml-1. All vessels exhibit adluminal layers of fibrils and are relatively compliant at pressures at or below heart systolic pressure. Arteries become stiffer at pressures greater than peak systolic pressure and at radii greater than twice the unpressurized radius. The dorsal abdominal artery possesses striated muscle in the lateral walls. This artery remains compliant over the entire range of hemolymph pressures expected in lobsters. These trends are illustrated when the incremental modulus of elasticity is compared among arteries. All arteries should function as Windkessels to damp the pulsatile pressures and flows generated by the heart. The dorsal abdominal artery may also actively regulate its flow.

scholarly journals The use of slotted – displacement ceiling diffuser in rooms with stationary workplaces with computer equipment

2019 ◽  
Vol 100 ◽  
pp. 00090
Author(s):  
Agnieszka Zając
Keyword(s):  
Vertical Plane ◽  
Heat Losses ◽  
Public Utility ◽  
Air Distribution ◽  
Transverse Axis ◽  
Heating And Cooling ◽  
Computer Equipment ◽  
Air Stream ◽  
Plane Passing ◽  
Winter Time

This paper presents a specification of premises with a stationary workstations. An analysis of thermal loads occurring in a public utility rooms equipped with a computer, electronic and multimedia equipment was carried out. Attention was drawn to an annual occurrence of a positive heat balances in an occupied workstations and heat losses in winter time in unoccupied premises. For an air distribution a slotted displacement ceiling diffuser was proposed, used for mixing ventilation (MV) in up-up type of air exchange in room. The results of measurements in the form of air flows in the area of its operation are provided. The graphs show the graphical distribution of air velocities and temperatures in the vertical plane passing through the transverse axis of the air diffuser. The study focused on one of the representative airflow of supply air and the behaviour of the air stream during heating and cooling was presented.

scholarly journals Major differences in noradrenaline action on lipolysis and blood flow rates in skeletal muscle and adipose tissue in vivo

Diabetologia ◽  
2005 ◽  
Vol 48 (5) ◽  
pp. 946-953 ◽  
Author(s):  
V. Quisth ◽  
S. Enoksson ◽  
E. Blaak ◽  
E. Hagström-Toft ◽  
P. Arner ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Blood Flow ◽  
Adipose Tissue ◽  
Flow Rates

Forced-Convection Mass Transfer From Wetted Grooves

1972 ◽  
Vol 94 (4) ◽  
pp. 715-719
Author(s):  
R. G. Bressler
Keyword(s):  
Mass Transfer ◽  
Forced Convection ◽  
Test Facility ◽  
Reynolds Analogy ◽  
Flow Rates ◽  
Capillary Action ◽  
Air Stream ◽  
Partial Pressures ◽  
Evaporative Heat Transfer ◽  
Wetted Wall Column

A wetted-wall column was used to measure liquid flow rates in capillary grooves on vertical surfaces. The test facility contained interchangeable grooved surfaces (2-in. OD) which contacted a liquid reservoir in such a way that the test surfaces were partially wetted by capillary action. The wetted portion was exposed to a forced-convection air stream, so that surface evaporation took place because of the different partial pressures of the vapor at the liquid-vapor interface and at the center of the air stream. All data were obtained in steady-state and nearly isothermal conditions. Experimental results with carbon tetrachloride on brass surfaces were in agreement with approximate predictions, which were computed for evaporative heat transfer and then related to mass transfer by using Reynolds analogy for pipe flow.

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