High-speed Digital Video Imaging Research Articles

Dynamic Torsional and Cyclic Fracture Behavior of ProFile Rotary Instruments at Continuous or Reciprocating Rotation as Visualized with High-speed Digital Video Imaging

IntroductionThis study examined the dynamic fracture behavior of nickel-titanium rotary instruments in torsional or cyclic loading at continuous or reciprocating rotation by means of high-speed digital video imaging. MethodsThe ProFile instruments (size 30, 0.06 taper; Dentsply Maillefer, Ballaigues, Switzerland) were categorized into 4 groups (n = 7 in each group) as follows: torsional/continuous (TC), torsional/reciprocating (TR), cyclic/continuous (CC), and cyclic/reciprocating (CR). Torsional loading was performed by rotating the instruments by holding the tip with a vise. For cyclic loading, a custom-made device with a 38° curvature was used. Dynamic fracture behavior was observed with a high-speed camera. The time to fracture was recorded, and the fractured surface was examined with scanning electron microscopy. ResultsThe TC group initially exhibited necking of the file followed by the development of an initial crack line. The TR group demonstrated opening and closing of a crack according to its rotation in the cutting and noncutting directions, respectively. The CC group separated without any detectable signs of deformation. In the CR group, initial crack formation was recognized in 5 of 7 samples. The reciprocating rotation exhibited a longer time to fracture in both torsional and cyclic fatigue testing (P < .05). The scanning electron microscopic images showed a severely deformed surface in the TR group. ConclusionsThe dynamic fracture behavior of NiTi rotary instruments, as visualized with high-speed digital video imaging, varied between the different modes of rotation and different fatigue testing. Reciprocating rotation induced a slower crack propagation and conferred higher fatigue resistance than continuous rotation in both torsional and cyclic loads.

Possible contribution of pannexin-1 to capsaicin-induced ATP release in rat nasal columnar epithelial cells

ABSTRACTCurrent evidence indicates that transient receptor potential (TRP) channel activity involves a relationship between opening of pannexin-1 and release of ATP into the extracellular space. We examined the effects of agonists of thermosensitive TRP channels (TRPM8, TRPA1, TRPV1, and TRPV2) on ATP release from rat nasal mucosa, and measured ciliary beat frequency (CBF) using digital high-speed video imaging. Single-cell patch clamping from dissociated rat nasal columnar epithelial cells was performed to confirm the relationship between pannexin-1 and TRP. We demonstrated that ATP release and CBF were significantly potentiated by the heat-sensitive TRPV1 agonist capsaicin (10 μM), but not by other TRP agonists. Capsaicin-induced ATP release and CBF increase were significantly inhibited by the pannexin-1 blockers carbenoxolone (10 μM) and probenecid (300 μM). In addition, the voltage step-evoked currents in the presence of capsaicin were inhibited by the pannexin-1 blockers in single-cell patch clamping. Our results suggest the participation of TRPV1 and pannexin-1 in the physiologic functions of rat nasal mucosa.

Analyzing the Dynamics and Morphology of Cast-off Pattern at Different Speed Levels Using High-speed Digital Video Imaging.

During a bloodstain pattern analysis, one of the essential tasks is to distinguish between different kinds of applied forces as well as to estimate their level of intensity. In this study, high-speed digital imaging has been used to analyze the formation of cast-off patterns generated by a simulated backswing with a blood-bearing object. For this purpose, 0.5 mL blood was applied evenly over the last 5 cm of a blade simulant. Bloodstains were created through the controlled acceleration of a backswing at different speed levels between 1.1 m/sec and 3.8 m/sec. The flight dynamics of blood droplets were captured with an Olympus® i-Speed 3 high-speed digital camera with a Nikon® AF Nikkor 50 mm f/1.8 D lens and analyzed using the Olympus i-Speed 3 Viewer software. The video analysis showed that, during the backswing, blood droplets would move toward the lower end of the knifepoint and would be tangentially thrown off. These droplets impacted on the horizontal surface according to the arc of the swing. An increase in velocity led to longer cast-off patterns with distinct morphological characteristics. Under laboratory conditions, bloodstain pattern analysis allows certain conclusions about the intensity of a backswing and provides instructions on the position of the offender. However, due to the number of unknown variables at a crime scene, such interpretation of cast-off patterns is extremely limited and should be performed with extreme caution.

Parameter Modification Guiding Optimization Design and Tests of a Rotary Transplanting Mechanism for Rice Plug Seedlings

A parameter modification guiding optimization method combined with fuzzy optimization was applied to improve the design of a rice plug seedling transplanting mechanism using a planetary gear train with elliptical gears and an incomplete non-circular gear. The laboratory kinematics was examined, and seedling transplanting tests were conducted. Based on the work principle analysis of the transplanting mechanism for rice plug seedlings, numerical kinematic objective functions were established using fuzzy objectives requirements such as transplanting trajectory and posture. Subordinate functions were determined to describe the objective functions. Then the optimization model of the mechanism was constructed which took the value of the subordinate degree of objective functions as the optimization objectives and the motion interference, height of the transplanting trajectory and mechanical structure as the constraint conditions. Parameter guiding optimization software based on Visual Basic 6.0 was developed independently to determine a set of better parameters for the mechanism, which can reduce dependence on expert experience and improve the efficiency of the design. The mechanism structure was designed, and a physical prototype was manufactured. A high-speed digital video camera and image processing technology were used to perform the kinematics bench tests to obtain the transplanting trajectory and posture of the mechanism. The consistency between the test results and theoretical results shows that the optimized mechanism can satisfy the transplanting requirements and that the design method and results are also accurate. Finally, rice seedling transplanting tests were conducted to verify the transplanting performance of the mechanism. The mechanism extracted 200 seedlings per minute per row with a success ratio of 95.89%; the mechanism also displayed a good effect in seedling pushing, showing that the mechanism could be applied in a practical machine.

EFFECTS OF PSEUDOPLASTICITY ON SPREAD AND RECOIL DYNAMICS OF AQUEOUS POLYMERIC SOLUTION DROPLETS ON SOLID SURFACES

The postimpact spreading and recoil behavior of millimeter-size liquid droplets of pure water, water–glycerol solution, and non-Newtonian aqueous solutions of medium-grade hydroxyl ethyl cellulose (HEC 250 MR) on dry horizontal hydrophobic (Teflon) and hydrophilic (glass) substrates is presented. The drop spread–recoil dynamics are captured using a high-speed high-resolution digital video recording and image processing. The non-Newtonian effects of aqueous polymeric solutions on postimpact spreading are contrasted with those for a water–glycerol solution with identical surface tension and zero-shear rate viscosity. For a broad range of drop Weber numbers (20 ≤ We ≤ 200), dynamic visualized records of impact, spreading, and recoil are presented along with their measured temporal variations in dropdiameter-scaled spread and film height. The shear-rate-dependent viscosity of the polymer solution is found to give rise to highly complex spread–recoil dynamics compared to Newtonian liquids. During initial spread, because the shear rate tends to be high, shear-thinning or pseudoplasticity effects manifest in polymer solution drops to alter their spread dynamics. Contrarily, during recoil their higher low-shear apparent viscosity tends to retard recoil and dampen shape oscillations. Shear-rate-dependent non-Newtonian behavior is further seen at low We (low shear rate during spreading), where the maximum spread of HEC solution droplets is comparable to that of high-viscosity water–glycerol solution, whereas at high We (high shear rate during spreading), their maximum spreads are closer to those of low-viscosity water droplets.

New Adenylate Kinase 7 (AK7) Mutation in Primary Ciliary Dyskinesia

Primary ciliary dyskinesia (PCD) is a congenital hereditary disease affecting 1/20,000-60,000 people that causes chronic sinusitis, bronchiectasis, sinus hypoplasia, secretory otitis media, and low fertility. The complexity and heterogeneity of the disease make diagnosis difficult. Although the genetic origin of PCD is clear, mutations in only five genes have been associated with the disease, and, to date, no disease-causing gene has been identified. Recently, low levels of AK7 gene expression have been linked to PCD. This study was designed to determine the mutational status of the AK7 gene in 31 PCD (17 PCD and 14 Kartagener syndrome diagnosed) patients compared with 40 healthy volunteers. We also determined the AK7 sequence in two families with members with PCD and investigated ciliary activity and ciliogenesis in one patient with a mutation in AK7. We analyzed nasal mucociliary transport and cilial ultrastructure by electron microscopy and studied nasal ciliary beat frequency and beat pattern using high-resolution digital high speed video (DHSV) imaging. Mutation analyses were performed by direct resequencing of the 18 exons of the AK7 gene. Air-liquid interface differentiated cultures were studied using DHSV imaging and histochemistry. AK7 gene expression was studied by real-time reverse-transcription polymerase chain reaction. We identified two mutations in the AK7 gene, the described single nucleotide polymorphism (rs2369679), and a new mutation (c.1214insT) that, to the best of our knowledge, has not been described previously. Family and functional studies indicated that c.1214insT could be related to PCD. Our results indicate that AK7 may be involved in the development of PCD.

Persistent disruption of ciliated epithelium following paediatric lung transplantation

It is unclear whether ciliary function following lung transplantation is normal or not. Our aim was to study the ciliary function and ultrastructure of epithelium above and below the airway anastomosis and the peripheral airway of children following lung transplantation. We studied the ciliary beat frequency (CBF) and beat pattern, using high speed digital video imaging and ultrastructure by transmission electron microscopy, of bronchial epithelium from above and below the airway anastomosis and the peripheral airway of 10 cystic fibrosis (CF) and 10 non-suppurative lung disease (NSLD) paediatric lung transplant recipients. Compared to epithelium below the anastomosis, the epithelium above the anastomosis in the CF group showed reduced CBF (median (interquartile range): 10.5 (9.0-11.4) Hz versus 7.4 (6.4-9.2) Hz; p<0.01) and increased dyskinesia (median (IQR): 16.5 (12.9-28.2)% versus 42.2 (32.6-56.4)%; p<0.01). In both CF and NSLD groups, compared with epithelium above the anastomosis, the epithelium below the anastomosis showed marked ultrastructural abnormalities (median duration post-transplant 7-12 months). Ciliary dysfunction is a feature of native airway epithelium in paediatric CF lung transplant recipients. The epithelium below the airway anastomosis shows profound ultrastructural abnormalities in both CF and NSLD lung transplant recipients, many months after transplantation.

Ciliary dysfunction and ultrastructural abnormalities are features of severe asthma

Epithelial dysfunction has been implicated in asthma pathophysiology, but no studies have directly assessed ciliary function in asthma. To study the ciliary function and epithelial ultrastructure of patients with asthma and healthy controls. We studied ciliary beat frequency and beat pattern by using digital high-speed video imaging and ultrastructure by transmission electron microscopy of bronchial epithelial strips from 7 subjects with mild, 7 with moderate, and 19 with severe asthma and 9 healthy controls. The median (interquartile range) ciliary beat frequency was decreased in moderate (6.5 [4.4-8.5] Hz) and severe asthma (6.7 [6.1-7.6] Hz) compared with controls (10.5 [9.7-11.8] Hz; P< .01). Dyskinesia and immotility indices were higher in severe asthma (65% [43%-75%]; 6.3% [1%-9.5%], respectively) compared with controls (4% [0%-6.7%; 0%, respectively; P<.01). These abnormalities were related to disease severity (ciliary beat frequency, r(s)= -0.68; dyskinesia index, r(s)= 0.86; immotility index, r(s)= 0.65; P< .0001). The ultrastructure of the epithelium was abnormal in severe asthma with a reduction in ciliated cells, an increase in dead cells, and ciliary disorientation compared with all other groups (P< .05). Compared with patients with mild asthma and healthy controls, patients with severe asthma showed increased ciliary depletion, microtubular defects, mitochondrial damage, and cytoplasmic blebbing (P<.01). All of these changes were related to disease severity. Ciliary dysfunction and ultrastructural abnormalities are closely related to asthma severity. Ciliary dysfunction is a feature of moderate to severe asthma, and profound ultrastructural abnormalities are restricted to severe disease. Whether these changes contribute to the development of severe asthma phenotype remains to be determined.

Characterising the dynamics of expirated bloodstain pattern formation using high-speed digital video imaging

During forensic investigations, it is often important to be able to distinguish between impact spatter patterns (blood from gunshots, explosives, blunt force trauma and/or machinery accidents) and bloodstain patterns generated by expiration (blood from the mouth, nose or lungs). These patterns can be difficult to distinguish on the basis of the size of the bloodstains. In this study, high-speed digital video imaging has been used to investigate the formation of expirated bloodstain patterns generated by breathing, spitting and coughing mechanisms. Bloodstain patterns from all three expiration mechanisms were dominated by the presence of stains less than 0.5mm in diameter. Video analysis showed that in the process of coughing blood, high-velocity, very small blood droplets were ejected first. These were followed by lower velocity, larger droplets, strands and plumes of liquid held together in part by saliva. The video images showed the formation of bubble rings and beaded stains, traditional markers for classifying expirated patterns. However, the expulsion mechanism, the distance travelled by the blood droplets, and the type of surface the blood was deposited on were all factors determining whether beaded stains were generated.

The effect of firearm muzzle gases on the backspatter of blood

Injuries caused by gunshots can produce what bloodstain pattern analysts know as "backspatter." Observations about the presence or absence of backspatter on an individual may be used in court as evidence of guilt or innocence. The discharge of three firearms (.22 caliber revolver, .38 caliber revolver, and .308 caliber rifle) and the resulting impact of bullets on a blood source were recorded using high-speed digital video imaging. Blood droplets, firearm muzzle gases, and ballistic shock waves were visualized using standard reflected light and shadowgraphy imaging techniques. A significant interaction between air currents, muzzle gases, and particulate material emanating from the firearms upon discharge with backspattered blood was observed. Blood droplets, initially spattered back toward the firearm and the shooter, were observed to change direction under the influence of firearm-induced air currents and were blown forward toward and beyond their original source location. Implications for experts testifying in court and for bloodstain pattern instructors are discussed.

Zinc Increases Ciliary Beat Frequency in a Calcium-Dependent Manner

Dynamic regulation of respiratory ciliary beat frequency (CBF) is regulated by fluxes in intracellular calcium (Ca(2+)). P2X receptors (P2XR) are extracellular ATP-gated, Ca(2+)-permeable, nonselective cation channels. Zinc increases intracellular Ca(2+) in a sodium (Na(+))-free environment through activation of P2XR channels. We hypothesize that topical zinc increases CBF in a Ca(2+)-dependent fashion as a result of this mechanism. The apical surface of mouse sinonasal air-liquid interface cultures were bathed in zinc in a Na(+)-free solution with or without Ca(2+). High-speed digital video imaging captured and analyzed CBF at a sampling rate of 100 frames/s. CBF significantly increased fourfold over baseline from 5.99 +/- 3.16 Hz to 22.4 +/- 4.33 Hz in the presence of zinc chloride (50 micromoles) and calcium chloride (3 mM). This effect is abolished in the presence of extracellular Na(+) and was pH dependent. Zinc stimulates CBF in the presence of Ca(2+) likely through activation of P2X receptors. Thus, zinc represents a promising agent for stimulation of mucociliary clearance.

Mono- versus biarticular muscle function in relation to speed and gait changes: in vivo analysis of the goat triceps brachii.

The roles of muscles that span a single joint (monoarticular) versus those that span two (biarticular) or more joints have been suggested to differ. Monoarticular muscles are argued to perform work at a joint, whereas biarticular muscles are argued to transfer energy while resisting moments across adjacent joints. To test these predictions, in vivo patterns of muscle activation, strain, and strain rate were compared using electromyography and sonomicrometry in two major elbow extensors, the long and lateral heads of the triceps brachii of goats (Capra hircus), across a range of speed (1-5 m s(-1)) and gait. Muscle recordings were synchronized to limb kinematics using high-speed digital video imaging (250 Hz). Measurements obtained from four goats (25-45 kg) showed that the monoarticular lateral head exhibited a stretch-shortening pattern (6.8+/-0.6% stretch and -10.6+/-2.7% shortening; mean+/-s.e.m. for all speeds and gaits) after being activated, which parallels the flexion-extension pattern of the elbow. By contrast, the biarticular long head shortened through most of stance (-16.4+/-3.4%), despite elbow flexion in the first half and shoulder extension in the last half of stance. The magnitude of elbow flexion and shoulder extension increased with increasing speed (ANCOVA, P<0.05 and P<0.001), as did the magnitude and rate of active stretch of fascicles in the lateral head (P<0.001 for both). In all individuals, shortening fascicle strain rates increased with speed in the long head (P<0.001), and, in three of the four individuals, strain magnitude increased. Few independent effects of gait were found. In contrast to its expected function, the biarticular long head appears to produce positive work throughout stance, whereas the monoarticular lateral head appears to absorb work at the elbow. The biarticular anatomy of the long head may mitigate increases in muscle strain with speed in this muscle, because strain magnitude in the second phase of stance (when the shoulder extends) decreased with speed (P<0.05).

‘Gobbling drops’: the jetting–dripping transition in flows of polymer solutions

This paper discusses the breakup of capillary jets of dilute polymer solutions and the dynamics associated with the transition from dripping to jetting. High-speed digital video imaging reveals a new scenario of transition and breakup via periodic growth and detachment of large terminal drops. The underlying mechanism is discussed and a basic theory for the mechanism of breakup is also presented. The dynamics of the terminal drop growth and trajectory prove to be governed primarily by mass and momentum balances involving capillary, gravity and inertial forces, whilst the drop detachment event is controlled by the kinetics of the thinning process in the viscoelastic ligaments that connect the drops. This thinning process of the ligaments that are subjected to a constant axial force is driven by surface tension and resisted by the viscoelasticity of the dissolved polymeric molecules. Analysis of this transition provides a new experimental method to probe the rheological properties of solutions when minute concentrations of macromolecules have been added.

Polygenic Modulation of Cardiac Dysfunction in Drosophila Assessed by High-speed Video Imaging, Motion Detection Analysis and Fluorescent Microscopy

Hypertrophic (HCM), dilated (DCM) and restrictive (RCM) cardiomyopathies are cardiac disorders often resulting from contractile protein mutations. They are frequently dominantly inherited and are characterized by a high degree of clinical heterogeneity proposed to result from modifying genetic factors. For example, HCM patients with multiple causal mutations present a more severe phenotype compared to single-mutation carriers. We employed high-speed digital video imaging and novel motion detection software to characterize in vivo cardiac structure and performance of homozygous Drosophila mutants, quantitatively assessing cardiac diameters, contractile periodicities, fractional shortening and rhythmicity parameters. Fly hearts expressing myosin with depressed or enhanced biomechanical properties exhibited hallmarks of human DCM or RCM respectively. To determine if the Drosophila cardiac phenotypes exhibit dominant modes of inheritance we studied the effects of heterozygotic expression of the myosin mutations. Interestingly, both mutations induced dominant cardiac dilatory responses. This suggests the homozygotic RCM-like phenotype is initiated by a unique cardiac remodeling pathway not activated in the presence of a wild-type myosin gene copy. We also used live-cell imaging and fluorescent microscopy to measure normalized cardiac tube area, in order to investigate polygenic effects of specific sarcomeric mutations on the severity of cardiac phenotypes in double heterozygotes. Combining a dilation-inducing troponin I mutation with the reduced function myosin mutation resulted in a dilatory cardiac phenotype at advanced age, which was more severe than that observed in single heterozygotes. However, combining the troponin mutation with the increased function myosin mutation appeared to prevent the cardiac dilation characteristic of the single heterozygotes. This suggests molecular combinations of certain mutations may have cardioprotective effects. Thus, Drosophila may serve as an effective in vivo tool for identifying and studying genetic enhancers and suppressors of cardiac dysfunction.

PACAP27 regulates ciliary function in primary cultures of rat brain ependymal cells

Ependymal cells line the brain ventricles and separate the CSF from the underlying neuronal tissue. The function of ependymal cilia is largely unclear however they are reported to be involved in the regulation of CSF homeostasis and host defence against pathogens. Here we present data that implicates a role of pituitary adenylate cyclase-activating polypeptide (PACAP) in the inhibition of ependymal ciliary function, and also that the PACAP effects are not entirely dependent on adenylyl cyclase activation. Primary ependymal cultures were treated with increasing doses of PACAP27 or adenylyl cyclase toxin (ACT), and ciliary beating was recorded using high-speed digital video imaging. Ciliary beat frequency (CBF) and amplitude were determined from the videos. Ependymal CBF and ciliary amplitude were attenuated by PACAP27 in a concentration- and time-dependent manner. The peptide antagonist PACAP6-27 blocked PACAP27-induced decreases in amplitude and CBF. Treatment with ACT caused a decrease in amplitude but had no effect on CBF, this suggests that the inhibition of CBF and amplitude seen with PACAP27 may not be completely explained by G(s)-AC-cAMP pathway. We present here the first observational study to show that activation of PAC1 receptors with PACAP27 has an important role to play in the regulation of ependymal ciliary function.

Variability of shallow overland flow velocity and soil aggregate transport observed with digital videography

AbstractField experiments at Tiramoana station 30 km north of Christchurch, New Zealand using an erosion plot 16·5 m long, 0·6 m wide, and with a slope of 14–14·5° on rendzina soil aimed to measure the variability of flow velocity and of soil aggregates transport rate in shallow overland flow. Discharge/cross‐section area ratio was used to estimate mean velocity, and high‐speed digital video camera and image analysis provided information about flow and sediment transport variability. Six flow runs with 0·5–3·0 L s−1 discharges were supercritical with Froude numbers close to or more than 1. Mean flow velocity followed Poiseuille law, float numbers were more than 1·5 and hydraulic resistance was an inverse proportional function of the Reynolds number, which is typical for laminar flows. Hence actual velocity varied through time significantly and the power spectrum was of ‘red‐noise’, which is typical for turbulent flow. Sediment transport rates had even higher variability, and soil aggregates transport was a compound Poisson process. Copyright © 2008 John Wiley &amp; Sons, Ltd.

B30 高速度ビデオカメラの画像解析を用いたスキージャンプの空力解析(スキー・リュージュ)

A ski jumping flight analysis was attempted on the basis of the high-speed digital video image taken at Hakuba Ski Jumping Stadium in Japan. Initial 40m of flights of 120-m jumping after take-off were recorded by a fixed high-speed video camera at a frame rate of 250 frames/s. After some corrections, a number of time series data were extracted for the loci of key parts of a jumper such as the waist, the ski boots and the ski tip as well as for key angles representing a jumper posture such as the ski angle and the forward leaning angle. It is demonstrated that the aerodynamic force data during real jumping flights, in particular in the early phase of a flight can be derived from video image.

Quantification of Ciliary Beat Frequency in Sinonasal Epithelial Cells Using Differential Interference Contrast Microscopy and High-Speed Digital Video Imaging

Mucociliary clearance is a critical upper airway host defense mechanism. Ciliated epithelium in the mammalian airway continually beat at a baseline frequency. Importantly, during times of stress such as exercise or infection, the cilia beat faster to increase clearance. Nasal epithelial ciliary beat frequency (CBF) has been analyzed previously in ex vivo specimens using a variety of methods including photodiode detectors and conventional video recording. Recent studies performed using lower airway ciliated mucosa have shown poor correlation between CBF quantified by photodiode/conventional video and those using high-speed digital video capture at temperatures close to physiological temperatures. Thus, to more rigorously interrogate sinonasal CBF at physiological conditions, we have incorporated a high-speed digital video camera to our CBF analysis system. This is the first report of sinonasal epithelial CBF analysis performed using high-speed video digital analysis. Ex vivo samples of sinonasal epithelium were placed in lactated Ringer's in a temperature-controlled microscope stage chamber. An edge of tissue containing beating cilia was observed at a magnification of 630x using differential interference contrast microscopy. The images were captured using a high-speed digital camera with a sampling rate of 250 frames per second. CBF was determined using computerized data analysis. The mean nasal CBF was calculated from a minimum of five regions for each sample. Temperature curves were generated from tissue obtained from chronically infected subjects. Analysis of high-speed digital video capture of sinonasal CBF observed under differential interference contrast microscopy is a powerful method to investigate environmental as well as host influences on mucociliary clearance within the upper airways.

A17 高速度ビデオカメラの画像解析を基にしたスキージャンプの空力特性の研究(サッカー・流れ)

A ski jumping flight analysis was attempted on the basis of the high-speed digital video image taken at Hakuba Ski Jumping Stadium in Japan. Initial 40m of flights of 120-m jumping after take-off were recorded by a fixed high-speed video camera at a frame rate of 250 frames/s. After some corrections, a number of time series data were extracted for the loci of key parts of a jumper such as the waist, the ski boots and the ski tip as well as for key angles representing a jumper posture such as the ski angle and the forward leaning (ski-body) angle. The primary purpose of the present study is to derive the aerodynamic force data during real jumping flights, in particular in the early phase of a flight.

CONVECTIVE BOILING IN PARALLEL MICROCHANNELS

Experiments were performed with clear water and with surfactant flowing in parallel triangular microchannels. The study is based on systematic measurements of temperature and flow pattern by infrared radiometry and high-speed digital video imaging. Different flow patterns were observed simultaneously in various microchannels at a fixed value of water or surfactant flow rates. Depending on flow and heat flux, pressure and temperature instabilities in the heated microchannels were studied. This work develops a practical modeling approach for two-phase microchannel heat sinks and also considers effect of surfactant on convective boiling in microchannels.