Feasibility of small bowel flow rate measurement with MRI

To evaluate whether it is feasible to measure the segmental flux of small bowel content using MR phase-contrast (PC) pulse sequences.

Dental erosion and salivary flow rate in cerebral palsy individuals with gastroesophageal reflux

A high prevalence of gastroesophageal reflux (GERD) has been observed in individuals with cerebral palsy (CP). One of the main risks for dental erosion is GERD. This study aimed to evaluate the presence of GERD, variables related to dental erosion and associated with GERD (diet consumption, gastrointestinal symptoms, bruxism), and salivary flow rate, in a group of 46 non-institutionalized CP individuals aged from 3 to 13 years.

Vertebroplasty: experimental characterization of polymethylmethacrylate bone cement spreading as a function of viscosity, bone porosity, and flow rate

STUDY DESIGN: This is an experimental study on an artificial vertebra model and human cadaveric spine. OBJECTIVE: Characterization of polymethylmethacrylate (PMMA) bone cement distribution in the vertebral body as a function of cement viscosity, bone porosity, and injection speed. Identification of relevant parameters for improved cement flow predictability and leak prevention in vertebroplasty. SUMMARY OF BACKGROUND DATA: Vertebroplasty is an efficient procedure to treat vertebral fractures and stabilize osteoporotic bone in the spine. Severe complications result from bone cement leakage into the spinal canal or the vascular system. Cement viscosity has been identified as an important parameter for leak prevention but the influence of bone structure and injection speed remain obscure. METHODS: An artificial vertebra model based on open porous aluminum foam was used to simulate bone of known porosity. Fifty-six vertebroplasties with 4 different starting viscosity levels and 2 different injection speeds were performed on artificial vertebrae of 3 different porosities. A validation on a human cadaveric spine was executed. The experiments were radiographically monitored and the shape of the cement clouds quantitatively described with the 2 indicators circularity and mean cement spreading distance. RESULTS: An increase in circularity and a decrease in mean cement spreading distance was observed with increasing viscosity, with the most striking change occurring between 50 and 100 Pas. Larger pores resulted in significantly reduced circularity and increased mean cement spreading distance whereas the effect of injection speed on the 2 indicators was not significant. CONCLUSION: Viscosity is the key factor for reducing the risk of PMMA cement leakage and it should be adapted to the degree of osteoporosis encountered in each patient. It may be advisable to opt for a higher starting viscosity but to inject the material at a faster rate.

Milk flow-controlled changes of pulsation ratio and pulsation rate affect milking characteristics in dairy cows

To test a system with milk flow-controlled pulsation, milk flow was recorded in 29 Holstein cows during machine milking. The three different treatments were routine milking (including a pre-stimulation of 50-70 s), milking with a minimum of teat preparation and milking with milk flow-controlled b-phase, i.e. with a gradually elongated b-phase of the pulsation cycle with increasing milk flow rate and shortening again during decreasing milk flow. For data evaluation the herd was divided into three groups based on the peak flow rate at routine milking (group 1: <3.2 kg/min; group 2: 3.2-4.5 kg/min; group 3: >4.5 kg/min). Compared with routine milking, milking with milk flow-controlled b-phase caused a significant elevation of the peak flow rate and the duration of incline lasted longer especially in cows with a peak flow rate of >3.2 kg/min in routine milking. In milking with a minimum of teat preparation the duration of incline lasted longer compared with the two other treatments. Bimodality of milk flow, i.e. delayed milk ejection at the start of milking, was most frequent at milking with a minimum of teat preparation. No significant differences between routine milking and milking with milk flow-controlled b-phase were detected for all other milking characteristics. In summary, milking with milk flow-controlled b-phase changes the course of milk removal, however mainly in cows with high peak flow rates.

Development and in-vitro characterization of an implantable flow sensing transducer for hydrocephalus

An implantable transducer for monitoring the flow of Cerebrospinal fluid (CSF) for the treatment of hydrocephalus has been developed which is based on measuring the heat dissipation of a local thermal source. The transducer uses passive telemetry at 13.56 MHz for power supply and read out of the measured flow rate. The in vitro performance of the transducer has been characterized using artificial Cerebrospinal Fluid (CSF) with increased protein concentration and artificial CSF with 10\% fresh blood. After fresh blood was added to the artificial CSF a reduction of flow rate has been observed in case that the sensitive surface of the flow sensor is close to the sedimented erythrocytes. An increase of flow rate has been observed in case that the sensitive surface is in contact with the remaining plasma/artificial CSF mix above the sediment which can be explained by an asymmetric flow profile caused by the sedimentation of erythrocythes having increased viscosity compared to artificial CSF. After removal of blood from artificial CSF, no drift could be observed in the transducer measurement which could be associated to a deposition of proteins at the sensitive surface walls of the packaged flow transducer. The flow sensor specification requirement of +-10\% for a flow range between 2 ml/h and 40 ml/h. could be confirmed at test conditions of 37 degrees C.

Modeling of Heat Transfer in Microchannel Gas Flow

Due to the existence of a velocity slip and temperature jump on the solid walls, the heat transfer in microchannels significantly differs from the one in the macroscale. In our research, we have focused on the pressure driven gas flows in a simple finite microchannel geometry, with an entrance and an outlet, for low Reynolds (Re<200) and low Knudsen (Kn<0.01) numbers. For such a regime, the slip induced phenomena are strongly connected with the viscous effects. As a result, heat transfer is also significantly altered. For the optimization of flow conditions, we have investigated various temperature gradient configurations, additionally changing Reynolds and Knudsen numbers. The entrance effects, slip flow, and temperature jump lead to complex relations between flow behavior and heat transfer. We have shown that slip effects are generally insignificant for flow behavior. However, two configuration setups (hot wall cold gas and cold wall hot gas) are affected by slip in distinguishably different ways. For the first one, which concerns turbomachinery, the mass flow rate can increase by about 1% in relation to the no-slip case, depending on the wall-gas temperature difference. Heat transfer is more significantly altered. The Nusselt number between slip and no-slip cases at the outlet of the microchannel is increased by about 10%.

Milk flow-dependent vacuum loss in high-line milking systems: effects on milking characteristics and teat tissue condition

To study the effects of a milking system that partially compensates for milk flow-dependent vacuum loss compared with a standard (high-line) milking unit in a tie-stall barn, milk flow and vacuum patterns were recorded in 10 cows during machine milking with 2 milking systems in a crossover design for 7 d each. Before and after each treatment period postmilking teat condition was recorded by ultrasound cross-sectioning. Additionally, 2 methods to measure teat tissue condition were compared: longitudinal teat ultrasound cross-sectioning and teat tissue density measurements with the spring-loaded caliper (cutimeter method). The partial compensation of milk flow-dependent vacuum loss caused an elevation of the peak flow rate (4.74+/-0.08 vs. 4.29+/-0.07 kg/min) and a shorter duration of plateau (1.57+/-0.06 vs. 1.96+/-0.07 min) compared with the standard milking system. Total milk yield, duration of incline and decline of milk flow, average milk flow, time until peak flow rate, main milking time, and total milking time did not differ between treatments (overall means: 13.75+/-0.17 kg; 0.65+/-0.01 min; 2.88+/-0.09 min; 2.82+/-0.05 kg/min; 1.65+/-0.03 min; 5.23+/-0.09 min, and 5.30+/-0.10 min, respectively). The vacuum drop in the short milk tube during periods of high milk flow was less in the compensating vacuum than in the standard milking system (11+/-1.1 vs. 15+/-0.7 kPa). Teat measures as determined by ultrasound remained unchanged over the entire experimental period with both milking systems. Postmilking teat tissue measures including their recovery within 20 min after the end of milking show a correlation (0.85 and 0.71, respectively) between the methods used (ultrasound and cutimeter method). In conclusion, a more constant vacuum at the teat tip (within the short milk tube) during periods of high milk flow affected milk flow patterns, mainly increasing peak flow rate. However, the reduced vacuum loss did not increase the overall speed of milking. In addition, effects of higher vacuum stability on teat condition and udder health were not obvious.

Relative impact of respiratory muscle activity on tidal flow and end expiratory volume in healthy neonates

INTRODUCTION: It has been suggested that infants dynamically regulate their tidal flow and end-expiratory volume level. The interaction between muscle activity, flow and lung volume in spontaneously sleeping neonates is poorly studied, since it requires the assessment of transcutaneous electromyography of respiratory muscles (rEMG) in matched comparison to lung function measurements. METHODS: After determining feasibility and repeatability of rEMG in 20 spontaneously sleeping healthy neonates, we measured the relative impact of intercostal and diaphragmatic EMG activity in direct comparison to the resulting tidal flow and FRC. RESULTS: We found good feasibility, repeatability and correlation of timing indices between rEMG activity and flow. The rEMG amplitude was significantly dependent on the resistive load of the face mask. Diaphragm and intercostal muscle activity commenced prior to the onset of flow and remained active during the expiratory cycle. The relative contribution of intercostal and diaphragmatic activity to flow was variable and changed dynamically. CONCLUSION: Using matched rEMG, air flow and lung volume measurements, we have found good feasibility and repeatability of intercostal and diaphragm rEMG measurements and provide the first quantitative measures of the temporal relationship between muscle activity and flow in spontaneously sleeping healthy neonates. Lung mechanical function is dynamically regulated and adapts on a breath to breath basis. So, non-invasive rEMG measurements alone or in combination with lung function might provide a more comprehensive picture of pulmonary mechanics in future studies. The data describing the timing of EMG and flow may be important for future studies of EMG triggered mechanical ventilation.

Studying the fate of non-volatile organic compounds in a commercial plasma air purifier

Degradation of non-volatile organic compounds-environmental toxins (methyltriclosane and phenanthrene), bovine serum albumin, as well as bioparticles (Legionella pneumophila, Bacillus subtilis, and Bacillus anthracis)-in a commercially available plasma air purifier based on a cold plasma was studied in detail, focusing on its efficiency and on the resulting degradation products. This system is capable of handling air flow velocities of up to 3.0m s(-1) (3200Lmin(-1)), much higher than other plasma-based reactors described in the literature, which generally are limited to air flow rates below 10Lmin(-1). Mass balance studies consistently indicated a reduction in concentration of the compounds/particles after passage through the plasma air purifier, 31% for phenanthrene, 17% for methyltriclosane, and 80% for bovine serum albumin. L. pneumophila did not survive passage through the plasma air purifier, and cell counts of aerosolized spores of B. subtilis and B. anthracis were reduced by 26- and 15-fold, depending on whether it was run at 10Hz or 50Hz, respectively. However rather than chemical degradation, deposition on the inner surfaces of the plasma air purifier occured. Our interpretation is that putative "degradation" efficiencies were largely due to electrostatic precipitation rather than to decomposition into smaller molecules.

A compact and portable deposition chamber to study nanoparticles in air-exposed tissue

BACKGROUND Epidemiological studies show that elevated levels of particulate matter in ambient air are highly correlated with respiratory and cardiovascular diseases. Atmospheric particles originate from a large number of sources and have a highly complex and variable composition. An assessment of their potential health risks and the identification of the most toxic particle sources would require a large number of investigations. Due to ethical and economic reasons, it is desirable to reduce the number of in vivo studies and to develop suitable in vitro systems for the investigation of cell-particle interactions. METHODS We present the design of a new particle deposition chamber in which aerosol particles are deposited onto cell cultures out of a continuous air flow. The chamber allows for a simultaneous exposure of 12 cell cultures. RESULTS Physiological conditions within the deposition chamber can be sustained constantly at 36-37°C and 90-95% relative humidity. Particle deposition within the chamber and especially on the cell cultures was determined in detail, showing that during a deposition time of 2 hr 8.4% (24% relative standard deviation) of particles with a mean diameter of 50 nm [mass median diameter of 100 nm (geometric standard deviation 1.7)] are deposited on the cell cultures, which is equal to 24-34% of all charged particles. The average well-to-well variability of particles deposited simultaneously in the 12 cell cultures during an experiment is 15.6% (24.7% relative standard deviation). CONCLUSIONS This particle deposition chamber is a new in vitro system to investigate realistic cell-particle interactions at physiological conditions, minimizing stress on the cell cultures other than from deposited particles. A detailed knowledge of particle deposition characteristics on the cell cultures allows evaluating reliable dose-response relationships. The compact and portable design of the deposition chamber allows for measurements at any particle sources of interest.

Influence of microphysical schemes on atmospheric water in the Weather Research and Forecasting model

This study examines how different microphysical parameterization schemes influence orographically induced precipitation and the distributions of hydrometeors and water vapour for midlatitude summer conditions in the Weather Research and Forecasting (WRF) model. A high-resolution two-dimensional idealized simulation is used to assess the differences between the schemes in which a moist air flow is interacting with a bell-shaped 2 km high mountain. Periodic lateral boundary conditions are chosen to recirculate atmospheric water in the domain. It is found that the 13 selected microphysical schemes conserve the water in the model domain. The gain or loss of water is less than 0.81% over a simulation time interval of 61 days. The differences of the microphysical schemes in terms of the distributions of water vapour, hydrometeors and accumulated precipitation are presented and discussed. The Kessler scheme, the only scheme without ice-phase processes, shows final values of cloud liquid water 14 times greater than the other schemes. The differences among the other schemes are not as extreme, but still they differ up to 79% in water vapour, up to 10 times in hydrometeors and up to 64% in accumulated precipitation at the end of the simulation. The microphysical schemes also differ in the surface evaporation rate. The WRF single-moment 3-class scheme has the highest surface evaporation rate compensated by the highest precipitation rate. The different distributions of hydrometeors and water vapour of the microphysical schemes induce differences up to 49 W m−2 in the downwelling shortwave radiation and up to 33 W m−2 in the downwelling longwave radiation.

[Subcutaneous emphysema following non-surgical peri-implantitis therapy using an air abrasive device: a case report]

Subcutaneous emphysema are rare complications in periodontology. In most cases, they resolve spontaneously. However, air might disperse into deeper facial spaces causing life-threatening complications such as compression of the tracheobronchial tree or the development of pneumomediastinum. Moreover, microorganisms might spread from the oral cavity into deeper spaces. Hence, rapid diagnosis of subcutaneous emphysema is important. Characteristic signs are both a shiftable swelling and a crepitation. In this case report, the case of a 69-year old man with a subcutaneous emphysema immediately after peri-implantitis therapy with the use of a glycine-based powder air-polishing device is described. Following therapy, air accumulated in the left side of the face. Seven days after non-surgical peri-implantitis therapy, the patient was asymptomatic with complete resolution of the emphysema.