BACKGROUND AND OBJECTIVES: Caloric nystagmus has been known since a century ago, and the thermal convection theory proposed by Barany has been widely accepted. Gravity plays an important role in thermal convection. In 1984, caloric nystagmus was reported in weightless space environments and although the response was weak, the nystagmus was found to occur in the same direction as the earth. This implies that factors other than thermal convection might participate in the caloric nystagmus. MATERIALS AND METHODS: Using 50 normal ears as subjects, this study compared the responses of conventional caloric test and reversed caloric test, which places the plane of the lateral semicircular canal upside down. RESULTS: The direction of the nystagmus was reversed, and the maximal slow phase velocity was decreased compared to that of the normal caloric test. CONCLUSION: The reversed direction of the nystagmus observed in this study basically supports the theory by Barany, however, the differences that are noted implicate that other factors with a certain direction maybe involved.
Caloric Tests* ; Convection ; Ear ; Gravitation ; Nystagmus, Physiologic ; Semicircular Canals

The life expectancy of end-stage renal disease patients undergoing regular hemodialysis (HD) remains significantly lower than in the general population. Reducing excess mortality by improving renal replacement options is an unmet medical need. Online post-dilution hemodiafiltration (HDF) has been promoted as the gold standard, offering improved clinical outcomes, based on numerous observational studies that suggest a reduced mortality risk and lower morbidity with HDF compared with standard HD. However, most randomized controlled trials (RCTs) have failed to demonstrate a significant beneficial effect of HDF on all-cause mortality. The effects on secondary outcomes were often negligible or absent. Unfortunately, these RCTs were characterized by a moderate to high risk of bias. In post-hoc analyses of the largest RCTs and meta-analysis of individual participant data from four RCTs, HDF patients receiving the highest convection volume consistently and dose-dependently saw superior outcomes. However, as these studies were not designed a priori to clarify this issue, and there are no indisputable mechanisms underlying reduced mortality risks, we cannot exclude the possibility that the health status of patients (with vascular access as a proxy) may affect outcomes more than the convective technique itself. There is currently insufficient evidence to support the contention that high-volume HDF confers relevant benefits to patients over standard HD. The conflicting data of published RCTs reduce confidence in the superiority of high-volume convective therapy. Hopefully, ongoing large RCTs (for example, CONVINCE) may supply an indisputable answer to the crucial question of high-volume HDF.
Bias (Epidemiology) ; Convection ; Hemodiafiltration ; Humans ; Kidney Failure, Chronic ; Life Expectancy ; Mortality ; Renal Dialysis

Background and OBJECTIVE: There are strong evidences that the caloric nystagmus may be due to non-convective factors in addition to the widely accepted Barany's convection theory. The influence of non-convective factor on the caloric nystagmus was interpreted by measuring the maximal slow phase eye velocity according to the head position. MATERIALS AND METHODS: In 18 normal ears, the maximal slow phase eye velocity of the cold caloric nystagmus was measured at five (-15degrees, 05degrees, 305degrees, 455degrees, 605degrees) different head positions. RESULTS: The sine value of the angle of the lateral semicircular canal (LSCC) plotted against the maximal slow phase velocity showed linear relationship without crossing the zero point in linear regression analysis. CONCLUSION: Maximal slow phase eye velocity shows linear relationship with the sine value of the angle of the LSCC. Compared with the curve expected by the convective factor, the curve in this study was biased by a constant amount (about 20%), which can be attributed to non-convective factor.
Bias (Epidemiology) ; Convection ; Ear ; Head* ; Linear Models ; Nystagmus, Physiologic* ; Semicircular Canals

The convective-diffusive problems of oxygen and carbon dioxide in human airway at normal respiratory status were studied theoretically in the present paper. The human airway was idealized as a bifurcated(two-branch) trachea tree, based on the understanding of the physiological structure of the human airway, and on Horsfield-Wanner optimization analysis about the trachea system status. It was assumed that the gases in the airway were incompressible, viscous fluid, due mainly to the characteristics of the low pressure drop and low rate of the gases within the human airway. One dimensional, non-steady convective-diffusive equations of oxygen and carbon dioxide were solved using Lax-Wendroff finite difference method, i.e., the so called three-legged finite difference method. The boundary conditions were set up according to the two different situations, respectively. The computational results showed the reasonable distributions of the concentration of oxygen and carbon dioxide in the human airway, respectively.
Bronchi ; physiology ; Carbon Dioxide ; metabolism ; Convection ; Diffusion ; Humans ; Models, Biological ; Oxygen ; metabolism ; Trachea ; physiology

Recently, the importance of on-site detection of pathogens has drawn attention in the field of molecular diagnostics. Unlike in a laboratory environment, on-site detection of pathogens is performed under limited resources. In this study, we tried to optimize the experimental conditions for on-site detection of pathogens using a combination of ultra-fast convection polymerase chain reaction (cPCR), which does not require regular electricity, and nucleic acid lateral flow (NALF) immunoassay. Salmonella species was used as the model pathogen. DNA was amplified within 21 minutes (equivalent to 30 cycles of polymerase chain reaction) using ultra-fast cPCR, and the amplified DNA was detected within approximately 5 minutes using NALF immunoassay with nucleic acid detection (NAD) cassettes. In order to avoid false-positive results with NAD cassettes, we reduced the primer concentration or ultra-fast cPCR run time. For singleplex ultra-fast cPCR, the primer concentration needed to be lowered to 3 µM or the run time needed to be reduced to 14 minutes. For duplex ultra-fast cPCR, 2 µM of each primer set needed to be used or the run time needed to be reduced to 14 minutes. Under the conditions optimized in this study, the combination of ultra-fast cPCR and NALF immunoassay can be applied to on-site detection of pathogens. The combination can be easily applied to the detection of oral pathogens.
Convection ; DNA ; Electricity ; Immunoassay ; NAD ; Pathology, Molecular ; Polymerase Chain Reaction ; Salmonella

OBJECTIVE: To compare the changes of extracellular space (ECS) structure and local drug distribution in adult brain and aged brain at different drug delivery rates in minimally invasive treatment of encephalopathy by convection enhanced delivery (CED) via ECS pathway. METHODS: Thirty-six SD male rats were divided into adult rats group (2-8 months, n=18) and aged rats group (18-24 months, n=18) according to the age of the month. According to the drug rates (0.1 μL/min, 0.2 μL/min, and 0.3 μL/min), they were randomly divided into 3 subgroups, 6 in each subgroup. Gadolinium-diethylene triamine pentaacetic acid (Gd-DTPA) with a concentration of 10 mmol/L were introduced into the caudate nucleus of each group of rats by stereotactic injection. Tracer-based magnetic resonance imaging (MRI) was used to dynamically monitor the diffusion and distribution images of the Gd-DTPA in the brain interstitial system (ISS). Using the self-developed MRI image measurement and analysis system software to process and analyze the obtained images, the diffusion coefficient, clearance rate, volume fraction, and half-life of each group of rats in the caudate nucleus ECS could be acquired. The effects and differences of drug clearance and ECS structural function in the brain of aged rats and adult rats were compared and analyzed at different drug delivery rates. Magnetic tracer D_ECS-mapping technique was used to observe the distribution and drainage of tracer in caudate nucleus. RESULTS: At the injection rate of 0.1 μL/min, the volume fraction in the aged rats was increased compared with that in the adult rats (18.20%±0.04% vs. 17.20%±0.03%, t=3.752, P=0.004), and the degree of tortuosity was decreased (1.63±0.04 vs. 1.78±0.09, t=-3.680, P=0.004), the drug clearance rate was decreased [(1.94±0.68) mm²/s vs. (3.25±0.43) mm²/s, t=-3.971, P=0.003], and the molecular diffusion in ECS was increased [(3.99±0.21)×10^-4 mm²/s vs. (3.36±0.37)×10^-4 mm²/s, t=3.663, P=0.004]. When the rate of injection increased to 0.2 μL/min, the drug clearance in ECS of the aged rats was slowed down [(2.53±0.45) mmol/L vs. (3.37±0.72) mmol/L, t=-1.828, P=0.021]. However, there were no significant differences in volume fraction, molecular diffusion in ECS and macroscopic drug metabolism parameters. When the rate of injection increased to 0.3 μL/min, the volume fraction in the aged rats was decreased (17.20%±0.03% vs. 18.20%±0.05%, t=-0.869, P=0.045), and the drug clearance rate in ECS was significantly accelerated [(4.04±0.76) mmol/L vs. (3.26±0.55) mmol/L, t=1.786, P=0.014], and there was no significant difference in tortuosity and the rate of molecular diffusion in the ECS. CONCLUSION The drug clearance and ECS structural parameters of brain ECS in aged brain with CED administration were changed at different rates, and it has the least effect on ECS in the aged brain at the injection rate of 0.2 μL/min. For the application of CED for the treatment of encephalopathy, we should consider the influence of factors such as age and injection rate, and provide reference for the development of individualized clinical treatment plan for minimally invasive treatment of encephalopathy via ECS pathway.
Animals ; Brain ; Convection ; Extracellular Space ; Gadolinium DTPA ; Magnetic Resonance Imaging ; Male ; Rats ; Rats, Sprague-Dawley

PURPOSE: This study was conducted to examine prerequisite-program performance of the hospital foodservice operation and develop measures for improvement of prerequisite-program performance. METHODS: Data were collected through surveys administered to 168 hospital dieticians in the Seoul, Incheon, Gyeonggi-do, Daegu, and North Gyeongsang areas. Out of total questionnaires, 65 questionnaires were usable and the response rate was 38.7%. Statistical analyses were performed using the SPSS program (ver 20.0) for chi2-test and one-way ANOVA. RESULTS: According to the result of the prerequisite-program evaluation, the percentage of 'appropriate', 'needs to be improved', and 'inappropriate' was 44.6%, 47.7%, and 7.7%, respectively. The score for the 'inappropriate' group was significantly lower than that of the 'appropriate' group or 'needs to be improved' group on the food safety management (p < 0.001), preparation facility management (p < 0.001), water management (p < 0.001), and storage.transportation management (p < 0.05) parts. Holding rate of foodservice facility and equipments in the 'appropriate' group were significantly higher than in the others on convection oven (p < 0.01), air conditioner (p < 0.01), three-compartment sink (p < 0.01), hot-holding equipment (p < 0.01), cold-holding equipment (p < 0.05), exclusive thawing refrigerator (p < 0.05), and sterilizer for sanitary shoes (p < 0.05) items. CONCLUSION: To improve the quality of hospital foodservice, foodservice managers and HACCP specialists should develop and implement a prerequisite-program and a HACCP plan considering the characteristics of the hospital foodservice operation.
Convection ; Daegu ; Food Safety ; Gyeonggi-do ; Hazard Analysis and Critical Control Points* ; Hospitals, General* ; Incheon ; Nutritionists ; Seoul ; Shoes ; Specialization ; Water

The trace toxic metal copper was assayed using mercury immobilized on a carbon nanotube electrode (MCW), with a graphite counter and a reference electrode. In this study, a macro-scale convection motor was interfaced with a MCW three-electrode system, in which a handmade MCW was optimized using cyclic-and square-wave stripping voltammetry. An analytical electrolyte for tap water was used instead of an expensive acid or base ionic solution. Under these conditions, optimum parameters were 0.09 V amplitude, 40 Hz frequency, 0.01 V incremental potential, and a 60-s accumulation time. A diagnostic working curve was obtained from 50.0 to 350 microg/L. At a constant Cu(II) concentration of 10.0 microg/L, the statistical relative standard deviation was 1.78% (RSD, n = 15), the analytical accumulation time was only 60 s, and the analytical detection limit approached 4.6 microg/L (signal/noise = 3). The results were applied to non-treated drinking water. The content of the analyzed copper using 9.0 and 4.0 microg/L standards were 8.68 microg/L and 3.96 microg/L; statistical values R2 = 0.9987 and R2 = 0.9534, respectively. This method is applicable to biological diagnostics or food surveys.
Convection ; Copper ; Diagnosis ; Drinking Water* ; Drinking* ; Electrodes ; Graphite ; Limit of Detection ; Metals* ; Nanotubes, Carbon ; Organothiophosphorus Compounds ; Reference Standards ; Drinking Water

BACKGROUNDS AND OBJECTIVES: The direction of caloric nystagmus depends on the head position as long as vestibular function is remaining but the it does not depend on head position change in the lateral semicircular canal (SCC) plugged ear, which is attributed to thermoconvection in the lateral SCC. So determination of head position dependency using ice water test is recommended in the evaluation of peripheral vestibulopathy in which dead labyrinth is suspected. Since ice water test in prone position is frequently skipped and neglected in many vestibular laboratories, we investigated the importance and necessity of evaluating head position dependency for the candidates of ice water test and estimated the amount of head position non-dependent component in discussion. MATERIALS AND METHOD: From January through September 2003, 25 patients, who showed no nystagmus during warm irrigation, were included in this study. Following forty milliliter of ice water irrigation in supine & prone position, the maximum slow phase eye velocity (SPEV) and direction of nystagmus were assessed using video nystagmography system. RESULT: Eleven cases showed head-position dependency and were interpreted as hypofunction of lateral SCC. Fourteen cases did not show head position dependency suggesting the absence of end organ function. However, in the latter group, 6 patients, who showed definite nystagmus to ice water irrigation in supine position, can be midinterpreted as hypofunction if ice water test in prone position is not performed. CONCLUSION: Evaluation of head position dependency in ice water irrigation is an important procedure in the determination of lateral SCC function and can provide valuable information when vestibular ablative procedures are considered.
Caloric Tests ; Convection ; Ear ; Ear, Inner ; Head* ; Humans ; Ice* ; Nystagmus, Physiologic ; Prone Position ; Semicircular Canals ; Supine Position ; Water*

Continous renal replacement therapy(CRRT) is becoming increasingly popular for the support of critically ill patients with acute renal failure, and the development of pump-driven volumetric-control CRRT machines with small extracorporeal volumes has lead to the widespread use of venovenous form of CRRT in pediatric field. Basic principles are diffusion and convection. CRRT is indicated in the hemodynamically unstable pediatric patients for hypervolemic anuric acute renal failure, electrolyte abnormalities, multiorgan failure, catabolic patients with increased nutritional needs and hyperammonemia, etc. To date, experiences are limited for pediatric CRRT, but current reports support that CRRT is feasible and useful in children and even infants, and the survival rate of the patients on CRRT is as same as adults. We describe the basic principles, equipments, methods and complications of CRRT, with special considerations on small children to meet the current need for CRRT.
Acute Kidney Injury ; Adult ; Child ; Convection ; Critical Illness ; Diffusion ; Humans ; Hyperammonemia ; Infant ; Pediatrics* ; Renal Replacement Therapy* ; Survival Rate