Temperature dependent barrier injection in transit time devices: Steady state

1982 ◽  
Vol 53 (9) ◽  
pp. 6236-6239 ◽  
Author(s):  
M. Mustafa ◽  
S. Ahmad
Keyword(s):  
Steady State ◽  
Transit Time ◽  
Temperature Dependent ◽  
In Transit

Nonlinear filter properties of the thick ascending limb

1997 ◽  
Vol 273 (4) ◽  
pp. F625-F634 ◽  
Author(s):  
H. E. Layton ◽  
E. Bruce Pitman ◽  
Leon C. Moore
Keyword(s):  
Steady State ◽  
Frequency Response ◽  
Transit Time ◽  
Concentration Profile ◽  
Tubuloglomerular Feedback ◽  
Thick Ascending Limb ◽  
Transport Parameters ◽  
Nodal Structure ◽  
Nacl Concentration ◽  
Fluid Transit Time

A mathematical model was used to investigate the filter properties of the thick ascending limb (TAL), that is, the response of TAL luminal NaCl concentration to oscillations in tubular fluid flow. For the special case of no transtubular NaCl backleak and for spatially homogeneous transport parameters, the model predicts that NaCl concentration in intratubular fluid at each location along the TAL depends only on the fluid transit time up the TAL to that location. This exact mathematical result has four important consequences: 1) when a sinusoidal component is added to steady-state TAL flow, the NaCl concentration at the macula densa (MD) undergoes oscillations that are bounded by a range interval envelope with magnitude that decreases as a function of oscillatory frequency; 2) the frequency response within the range envelope exhibits nodes at those frequencies where the oscillatory flow has a transit time to the MD that equals the steady-state fluid transit time (this nodal structure arises from the establishment of standing waves in luminal concentration, relative to the steady-state concentration profile, along the length of the TAL); 3) for any dynamically changing but positive TAL flow rate, the luminal TAL NaCl concentration profile along the TAL decreases monotonically as a function of TAL length; and 4) sinusoidal oscillations in TAL flow, except at nodal frequencies, result in nonsinusoidal oscillations in NaCl concentration at the MD. Numerical calculations that include NaCl backleak exhibit solutions with these same four properties. For parameters in the physiological range, the first few nodes in the frequency response curve are separated by antinodes of significant amplitude, and the nodes arise at frequencies well below the frequency of respiration in rat. Therefore, the nodal structure and nonsinusoidal oscillations should be detectable in experiments, and they may influence the dynamic behavior of the tubuloglomerular feedback system.

scholarly journals Accumulation of Non-steroidal Anti-inflammatory Drugs by Gingival Fibroblasts

2006 ◽  
Vol 85 (5) ◽  
pp. 452-456 ◽  
Author(s):  
M.M. Zavarella ◽  
O. Gbemi ◽  
J.D. Walters
Keyword(s):  
Steady State ◽  
Connective Tissue ◽  
Inflammatory Mediator ◽  
Dependent Manner ◽  
Gingival Fibroblasts ◽  
Temperature Dependent ◽  
Tnf Α ◽  
Steady State Levels ◽  
Inflammatory Drugs ◽  
Anti Inflammatory

Non-steroidal anti-inflammatory drugs (NSAIDs) are used to manage pain and inflammatory disorders. We hypothesized that gingival fibroblasts actively accumulate NSAIDs and enhance their levels in gingival connective tissue. Using fluorescence to monitor NSAID transport, we demonstrated that cultured gingival fibroblasts transport naproxen in a saturable, temperature-dependent manner with a Km of 127 μg/mL and a Vmax of 1.42 ng/min/μg protein. At steady state, the intracellular/extracellular concentration ratio was 1.9 for naproxen and 7.2 for ibuprofen. Naproxen transport was most efficient at neutral pH and was significantly enhanced upon cell treatment with TNF-α. In humans, systemically administered naproxen attained steady-state levels of 61.9 μg/mL in blood and 9.4 μg/g in healthy gingival connective tissue, while ibuprofen attained levels of 2.3 μg/mL and 1.5 μg/g, respectively. Thus, gingival fibroblasts possess transporters for NSAIDs that are up-regulated by an inflammatory mediator, but there is no evidence that they contribute to elevated NSAID levels in healthy gingiva.

Stability of maternal serum free β-hCG following whole blood sample transit: First trimester Down’s syndrome screening in Scotland

2021 ◽  
pp. 000456322110452
Author(s):  
Angela Ballantyne ◽  
Lorna Rashid ◽  
Rebecca Pattenden
Keyword(s):  
Transit Time ◽  
Down's Syndrome ◽  
Down’S Syndrome ◽  
First Trimester ◽  
Maternal Serum ◽  
Dependent Manner ◽  
Serum Free ◽  
Β Hcg ◽  
In Transit ◽  
The Impact

Background Maternal serum free beta human chorionic gonadotrophin (free β-hCG) is used as a biomarker in first trimester screening for fetal Down’s syndrome. Production of free β-hCG can occur in vitro in a time- and temperature-dependent manner; thus, the current Scottish screening protocol states samples must be received by the laboratory within 72 h. To assess the validity of the protocol, an audit was conducted to determine the impact of transit time on maternal serum free β-hCG multiple of median (MoM) values in the Scottish screened population. Methods Corrected MoM values from antenatal screening carried out over one year (April 2017 to March 2018) were stratified according to sample transit time and compared. To investigate possible environmental temperature effects, the data were split according to season and maternal serum free β-hCG concentrations from summer and winter compared. Results Of the 28,368 samples included in the study, 24,368 were received on the day of phlebotomy or after one day in transit. Only 1.5% of samples were received after 3 days in transit. The difference in maternal serum free β-hCG MoM values due to transit time was not significant. No statistical difference was found between maternal serum free β-hCG concentrations from samples collected in summer and winter months. Conclusion The current sample receipt protocol in use by the Scottish Down’s syndrome screening programme is fit for purpose.

scholarly journals Ecosystem carbon transit versus turnover times in response to climate warming and rising atmospheric CO<sub>2</sub> concentration

2018 ◽  
Vol 15 (21) ◽  
pp. 6559-6572 ◽  
Author(s):  
Xingjie Lu ◽  
Ying-Ping Wang ◽  
Yiqi Luo ◽  
Lifen Jiang
Keyword(s):  
Steady State ◽  
Transit Time ◽  
Climate Warming ◽  
Age Structure ◽  
C Sequestration ◽  
Turnover Time ◽  
Atmospheric Co2 ◽  
Ecosystem Carbon ◽  
Subsequent Decrease ◽  
Diagnostic Time

Abstract. Ecosystem carbon (C) transit time is a critical diagnostic parameter to characterize land C sequestration. This parameter has different variants in the literature, including a commonly used turnover time. However, we know little about how different transit time and turnover time are in representing carbon cycling through multiple compartments under a non-steady state. In this study, we estimate both C turnover time as defined by the conventional stock over flux and mean C transit time as defined by the mean age of C mass leaving the system. We incorporate them into the Community Atmosphere Biosphere Land Exchange (CABLE) model to estimate C turnover time and transit time in response to climate warming and rising atmospheric [CO2]. Modelling analysis shows that both C turnover time and transit time increase with climate warming but decrease with rising atmospheric [CO2]. Warming increases C turnover time by 2.4 years and transit time by 11.8 years in 2100 relative to that at steady state in 1901. During the same period, rising atmospheric [CO2] decreases C turnover time by 3.8 years and transit time by 5.5 years. Our analysis shows that 65 % of the increase in global mean C transit time with climate warming results from the depletion of fast-turnover C pool. The remaining 35 % increase results from accompanied changes in compartment C age structures. Similarly, the decrease in mean C transit time with rising atmospheric [CO2] results approximately equally from replenishment of C into fast-turnover C pool and subsequent decrease in compartment C age structure. Greatly different from the transit time, the turnover time, which does not account for changes in either C age structure or composition of respired C, underestimated impacts of warming and rising atmospheric [CO2] on C diagnostic time and potentially led to deviations in estimating land C sequestration in multi-compartmental ecosystems.

Charge Generation in PbS Quantum Dot Solar Cells Characterized by Temperature-Dependent Steady-State Photoluminescence

ACS Nano ◽  
2014 ◽  
Vol 8 (12) ◽  
pp. 12814-12825 ◽  
Author(s):  
Jianbo Gao ◽  
Jianbing Zhang ◽  
Jao van de Lagemaat ◽  
Justin C. Johnson ◽  
Matthew C. Beard
Keyword(s):  
Solar Cells ◽  
Steady State ◽  
Quantum Dot ◽  
Temperature Dependent ◽  
Charge Generation ◽  
Quantum Dot Solar Cells ◽  
Pbs Quantum Dot

Effects of lumen volume transit time and pressure on loop of Henle function

1979 ◽  
Vol 237 (3) ◽  
pp. F196-F203 ◽  
Author(s):  
A. D. Baines ◽  
D. Basmadjian ◽  
B. C. Wang
Keyword(s):  
Transit Time ◽  
Distal Tubule ◽  
Salt Transport ◽  
Perfusion Rate ◽  
Luminal Diameter ◽  
Lumen Volume ◽  
Unstirred Layers ◽  
Transit Times ◽  
Two Samples ◽  
In Transit

Experiments on Henle's loops were designed to demonstrate the relationships of absorption to distal pressure, transit time, and luminal diameter. Loops of superficial nephrons in hydropenic rats, isolated from the rest of the nephron by oil or solid paraffin blocks, were microperfused at 13.6--20 nl/min. Two samples of fluid were collected from the early distal tubule--one with suction in order to lower distal pressure and reduce luminal volume, the other without suction so that the lumen was distended. Transit times were 30 +/- 2 s without and 19 +/- 2 s with suction. Proximal tubule pressure and perfusion rate were not altered by collection with suction. Absolute absorption, however, descreased from 10.6 +/- 0.4 to 8.4 +/- 0.4 nl/min (P less than 0.001). When salt transport was inhibited by 10(-4) M furosemide in the perfusate, water absorption was 7.8 +/- 0.7 nl/min without suction and 6.1 +/- 0.8 nl/min with suction (P less than 0.01). Computer simulation of Henle's loop shows that these observations cannot be explained by changes in transit time, hydrostatic pressure, or unstirred layers. The observations are simulated when radial fluxes depend on wall thickness and surface area in the descending thin limb.

scholarly journals Short-Term Daily Intake of Polydextrose Fiber Does Not Shorten Intestinal Transit Time in Constipated Adults: A Randomized Controlled Trial

Nutrients ◽  
2018 ◽  
Vol 10 (7) ◽  
pp. 920 ◽  
Author(s):  
Peter Duncan ◽  
Catherine Enters-Weijnen ◽  
Nashmil Emami ◽  
Peter McLean ◽  
Tiago Nunes ◽  
...  
Keyword(s):  
Transit Time ◽  
Controlled Trial ◽  
Daily Intake ◽  
Intestinal Transit ◽  
Double Blind ◽  
Intestinal Transit Time ◽  
Gi Symptoms ◽  
Marker Distribution ◽  
Clinical Measures ◽  
In Transit

Chronic constipation (CC) remains a common gastrointestinal (GI) disorder that conveys a substantial healthcare burden. Expert guidelines recommend increasing fiber intake, yet the clinical evidence to support this needs strengthening for specific fibers. The aim was to evaluate changes in intestinal transit time and GI symptoms in CC patients who consumed polydextrose. In a randomized, double-blind, placebo-controlled trial, 128 adults with CC received 8 g or 12 g polydextrose, or placebo, daily for 4 weeks. Transit time, as primary outcome, was assessed by radiopaque marker distribution after 2-weeks intervention. Bowel habits, GI symptoms and quality of life (QOL) were assessed by questionnaire, including the Patient-Assessment of Constipation (PAC) Symptoms (SYM), and PAC-QOL. Following 2-weeks intervention, no reduction was seen in transit time in any group and following 2- or 4-weeks intervention, no improvements were seen in stool frequency or consistency in any group. After 2-weeks intervention with 8 g/day polydextrose an improvement was seen in the PAC-SYM rectal score (p = 0.041). After 4-weeks intervention both rectal (p = 0.049) and stool (p = 0.029) scores improved while improvement in the QOL satisfaction score did not reach significance (p = 0.071). Overall, the results suggest that 2-weeks consumption of 8 or 12 g/day polydextrose does not significantly improve physiological measures of gut function in CC adults. Longer term consumption may improve clinical measures, but further studies will be required to substantiate this.

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