Mean Transport Time Research Articles

Parametrische Darstellung der Nierenfunktion mit 99mTC-Merkaptoazetyltriglyzin (MAG3)

99mTc-mercaptoacetyltriglycine (MAG3) has recently been introduced for imaging kidney function. Due to the much lower radiation dose per MBq, the total administered activity can be much higher than in the case of 131l-ortho-iodo-hippurate (OIH). The improved counting statistics make this tracer useful for parametric imaging of the kidneys. To investigate this potential of MAG3, its kinetics was compared with that of the reference tracer OIH in 38 patients. Parameters of extrarenal tracer kinetics such as the distribution volumes, the whole-body elimination times and the clearance rates showed a good correlation; however, the clearance rate of MAG3 was always lower than that of OIH. The intrarenal kinetics was investigated using the transfer function which was calculated by deconvolution analysis of the renographic curves. Parameters of the transfer function such as the amplitude, extraction fraction and mean transport time demonstrated a high correlation between the two tracers. Since MAG3 seems to be suitable for parametric imaging of kidney function, parametric images of perfusion, uptake, extraction and transport times were calculated by deconvolution analysis of the MAG3 pixel-renograms in various renal disorders. The parameters were distributed homogenously throughout the parenchyma of normal kidneys. In a kidney with a hemodynamically significant renal artery stenosis the perfusion parameter was decreased and the time parameter was prolonged. Further examples of a renal graft acute tubular necrosis, an obstructive uropathy, an obstructive nephropathy and of a horse-shoe kidney demonstrate that the parametric images are useful for quantitative investigation of regional renal function.

Air Transport Following Surgical Stabilization

A 30-month retrospective review was performed of all trauma patients initially evaluated and operatively stabilized at Level III hospitals, with subsequent specialized air transport within 48 hours of injury to the regional Level I trauma center in Seattle. Nineteen patients were identified, with a mean ISS of 44 (range, 20-66). Mean transport time and distance were 2.4 hours and 456 miles, respectively. The estimated average ground transport time for the same patients was 23.8 hours. No deaths occurred during transport, and the overall survival rate was 58%. Transport charges averaged $4,162, which was 14% of the complete hospitalization cost. We conclude that: 1) patient survival after air transport was no different than that predicted for trauma victims with immediate access to a trauma center; 2) postoperative hemodynamic instability predicted a poor outcome; 3) the higher cost of air relative to ground transport is outweighed by significant time savings in these critically injured patients; and 4) air transport following operative stabilization represents an extension of regionalized trauma care to the isolated areas of Washington and Alaska.

Effect of membrane flow on the capture of receptors by coated pits. Theoretical results

Coated pits trap cell surface receptors and mediate their internalization. Once internalized, many receptors recycle back to the cell surface. When recycled receptors are inserted into the plasma membrane, they move until they are again trapped in coated pits. The mechanisms for moving receptors from their insertion sites to coated pits are unknown. Unaided diffusion as the transport mechanism is consistent with the observed kinetics of receptor recycling. Another candidate for the transport mechanism is convection. For receptors that recycle to random positions on the cell surface, or to restricted regions about coated pits, we assess the importance of convective flow in the transport of receptors to coated pits. First we consider local flows set up by the formation of coated pits and their transformation into coated vesicles. As coated pits form and round into coated vesicles, surrounding membrane is drawn inward, creating flows directed toward the coated pit centers. We show that unless the lifetime of a coated pit is very short, 10 s or less, such local flows have a negligible effect on the time it takes receptors to reach coated pits. We also show that they are unlikely to be the mechanism that keeps receptors that have reached coated pits trapped within coated pits until they are internalized. Finally we calculate the mean time tau for a diffusing receptor to reach a coated pit in the presence of membrane flow that is constant in magnitude and direction, as may occur on moving cells. We show that for typical membrane flow velocities, tau can be reduced significantly from its value in the absence of flow. For example, a velocity v = 2.8 micron/min cuts the mean transport time in half.

Results of attempted cardiopulmonary resuscitation of patients dying suddenly outside the hospital in Reykjavik and the surrounding area, 1976-1979.

Cardiopulmonary resuscitation (CPR) was attempted in 222 cases of sudden death at the City Hospital, Reykjavik, during 1976-79. Of the 68 patients (31%) successfully resuscitated, 47 died in the hospital and 21 (9%) were discharged, 17 in good mental and physical condition. The mean combined response and transport time was 12.1 min and the ambulance mean time of response 7.3 min. The first ECG revealed considerable prognostic indications. Of the 90 patients who had ventricular fibrillation on admission, 42 (47%) were successfully resuscitated and 18 (20%) were subsequently discharged. Among 114 patients with asystole, resuscitation was successful in 23 (20%) and two (2%) were discharged. Immediate first aid in situ had a definite prognostic influence. These results compare favourably with those obtained elsewhere where the organization of first aid and emergency transport is similar. They do not, however, match the results achieved by fully specialized resuscitation teams trained to operate outside the hospital. Results of CPR of patients with cardiac arrest out of hospital in Reykjavik show increasing improvement over the years. This may be partly explained by a considerable public debate on this issue in 1978 and subsequent streamlining of activities.

Rapid continuous separation procedures for zirconium, niobium, technetium, bromine and iodine from complex reaction product mixtures

Fast, continuous methods for the separation of radiochemically pure samples of Zr, Nb, Tc, Br and I from fission product mixtures are described. The procedures involve multistage solvent extraction separations with the centrifuge facility “SISAK 2” connected to a gas-jet recoil transport system. The mean transport time between production and measurement amounts to 5–9 s depending on the element to be separated.

Analysis of Flow Control in Alternative Manufacturing Configurations

A mathematical model of workflow, based on queueing network theory, is used to compare the performance of four alternative layout configurations for manufacturing systems: a product layout (or flowshop), a process layout (or job shop), and two layouts which have been used in computerized manufacturing system. It is shown that, under appropriate conditions, any one of the four layouts could be the preferred choice. The impact of part mix, process selection, and the ratio of mean process time to mean transport time on the layout design are revealed and quantified.

Factors in successful resuscitation by paramedics

The out-of-hospital reports of 2152 consecutive paramedic fire rescue responses were reviewed. Examination of emergency department records and outcome was conducted in all cardiopulmonary arrests (120), major trauma (59) or nontraumatic hemorrhage (9) and one half (95 of 199 patients) with chest pain or possible myocardial infarction. Predominant age was 50 to 70 (66%) and men outnumbered women by four to one. At the scene arrival was under five minutes in over 70% of the cases. Thirty of the 120 patients with cardiopulmonary arrest (12 occurred after paramedic arrival) responded to initial cardiopulmonary resuscitation, 24 patients entered the coronary care unit, and 16 were discharged alive. Ventricular fibrillation (50) and asystole (40) were the documented rhythms. All survivors had ventricular fibrillation. Evaluation of the trauma and nontraumatic blood loss victims indicated that, after the paramedic places an intravenous line, the paramedic role is less well defined. Mean transportation time was 36 (trauma) and 38 (hemorrhage) minutes to the hospital.

Daily spermatozoal production, epididymal spermatozoal reserves and transit time of spermatozoa through the epididymis of the rhesus monkey.

Experiments were performed to establish the daily level of testicular production of spermatozoa, the distribution of spermatozoa within the epididymis, and the time required for transport of spermatozoa through the epididymis in 8 sexually rested rhesus monkeys (Macaca mulatta) of at least 6 years of age. The daily production of spermatozoa was similar among all animals, averaging a production rate of 23 times 10 (6) sperm/gm of testicular parenchyma per day. However, the weight of testicular parenchyma ranged from 15 to 32 gm. Per testis , the average daily spermatozoal production was found to be 547 plus or minus 69 tomes 10(6). Consequently, the normal average production of spermatozda for the rhesus monkey per day during the breeding seasson is about 1.1 times 10(9). The number of sperm in the caput, corpus, and cauda epididymis was found to be .6 plus or minus .1, 2.1 plus or minus .3, and 2.9 plus or minus .3 times 10(9), respectively. 1 plus or minus .1 times 10(9) sperm were found in the proximal 49-70 mm of the ductus deferens. The mean transport times of sperm through the caput, corpus, and cauda epididymis were approximately 1.1, 3.8, and 5.6 days, respectively. The rate of transport of sperm through the epididymis was virtually the same between 2-5.5 days, even though a 265-fold difference in epididymal reserves was found. The results indicate that sperm matures within the epididymis of this species within 5 days.

Detection of instantaneous phase changes in gas-liquid mixtures

The paper presents a direct quantitative comparison of three phase detection systems for determination of local instantaneous phase changes in gas-liquid mixture flows. These include constant temperature heat transfer probes, various resistivity probes and an infrared absorption system. For each probe system estimates could be made of local void fractions, and these values indicated that the single needle resistivity probes caused least disturbance to the flow and were capable of resolving the smallest bubbles. With two such probes displaced axially, the mean transport time of the bubbles could be determined. These values were used to estimate local gas phase velocities which could be integrated to give average gas phase velocities. Values determined in this manner were compared to values from flow rate measurements and showed an average deviation of less than 6.2%.

Application of the helium-jet technique for fission fragment transport from spontaneous fission sources

The helium-jet method has been adapted for the transport of fission products from a 252Cf source. It has been found that the helium carrier gas must be seeded with H 2O vapor and irradiated with an ultra-violet light source to obtain high efficiencies. There is indication of the role of free radicals in producing high- molecular-weight species that are necessary for the transport of the fission products. Transport efficiencies of about 55% and mean transport times of 30 s have been achieved.

The Role of Estrogens in Egg Transport Through the Ampullae of Oviducts of Castrate Rabbits

This article presents a description of patterns of muscle activity and ovum transport through the ampullae of the oviducts of 12 sexually mature New Zealand White female ovariectomized rabbits in 3 circumstances: 1) with no hormonal treatment; 2) 1-3 hr. after the last of a series of estrogen injections; 3) 30-32 hr. after the last injection in the series. The estrogen injected was estradiol-17-beta given in portions of 6 mcg. The time required for 89 supravitally stained donor eggs to pass through the ampullae of the oviducts for each of the 3 groups was as follows: 1) 25 ova in 4 castrate rabbits of Group 1 mean transport time 15.2 plus or minus 3.6 min.; 2) Group 2 rabbits 30 ova in 3 rabbits mean transport time 12.0 plus or minus .7 min.; 3) Group 3 rabbits 34 ova in 5 rabbits mean transport time 2.4 plus or minus 1.6 min. The rabbits were castrated for periods ranging from 84-165 days prior to ovum transport observations. The decrease in transport time from Group 1 to Group 3 is associated with an increase in activity of the ampullary musculature. The increase in muscle activity and rate of ovum transport are interpreted as being related in some manner with a reduction in the amount of estrogen present in the estrogen-primed smooth musculature of the ampulla.

National External Quality Assurance Scheme For Hiv Testing Using Dried Blood Spot: A Feasibility Study

Introduction: Dried Blood Spot (DBS) for National External Quality Assurance Scheme (NEQAS) is becoming popular in resource limited and geographically constrained settings. The feasibility of using DBS for EQAS for HIV testing in Nepal is studied. Methodology: National Public Health Laboratory (NPHL) and fi ve Voluntary Counseling and Testing Centers (VCT) located at the Mid-Western and Central region of Nepal were chosen as the organizing and participating laboratories, respectively. HIV tests were performed on 35 samples using rapid test kits following the National algorithm. Two sets of samples were blotted on a DBS card, dried, packed, stored and posted to NPHL using normal postal delivery. The eluted DBS were tested by rapid test and ELISA and results were compared. Results: All DBS cards were received in a good condition. The rapid test result obtained at VCT and NPHL was 100% concordant. By ELISA, 32 (91.4%) and 3 (8.6%) samples were concordant and discordant, respectively. The sensitivity and specifi city of the rapid test were 88.9% and 94.0%, respectively. The DBS was stable with mean transportation time of 2.25 days and storage time of one month. Conclusion: DBS is an easy, simple, cost effective and a dynamic platform for blood collection in a country like Nepal and can be considered for implementation for NEQAS for HIV testing. DOI: http://dx.doi.org/10.3126/saarctb.v8i2.5897 SAARCTB 2011; 8(2): 23-27