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A shock wave-driven needle-free syringe was developed and tested for liquid jet delivery into an artificial skin model and porcine skin samples. The device could deliver an adequate volume of liquid to a depth sufficient for drug dissemination in skin samples. The device is equipped with a splash-proof conduit and a silencer for smooth operation. The concept is expected to minimize the pain of liquid injection by (a) minimally breaching the blood vessels in the skin, (b) reducing trauma and inflammation, and aiding in regeneration of the incised spot by the liquid of the jet, and (c) preserving most of the microcirculation system in the target, enabling an effective drug uptake. A theoretical model that predicts jet penetration into viscoelastic targets is derived and presented. A sound agreement has been observed between the experimental jet penetration depths and the corresponding theoretical predictions. The development can offer a cost-effective, minimally invasive health care solution for immunization and drug delivery.

Closed-cell aluminum foams of density 0.3 to 0.46 g/cc (1 g/cc=1,000 kg/m3) were exposed to incident shock waves of 10–11 bar (1 bar=1.01325×105 N/m2) pressure in a shock tube to study...

A blunt double-cone model, equipped with a three-component accelerometer or piezofilm-based force balance system, is tested in the IITB-Shock Tunnel at 0 º and 10 º angle of inclinations during force measurement experiments. Conventional accelerometer force balance theory and soft computing-based adaptive neuro fuzzy inference system have been adopted to recover the axial and normal forces. In order to arrive at the time varying forces, these balances are calibrated using impulse hammer tests at single or multiple points. Necessity of multipoint calibration has also been demonstrated during recovery of forces for both the balances. Genetic algorithm in conjunction with adaptive neuro fuzzy inference system has been implemented herein to train the system for force prediction. Encouraging agreement has been noted between the predictions made using accelerometer force balance theory and adaptive neuro fuzzy inference system-based recovery of forces from accelerometer and piezofilm balances. Thus, present studies not only provide the methodology for calibration and implementation of piezofilm based force measurement, but also recommend its usage in short duration impulse facilities.

A blunt bi-conic aluminum model, integrated with a three component accelerometer force balance system, is tested in the IITB-Shock Tunnel at various angle of inclinations with an intention to measure aerodynamic coefficients. Initially, Genetic Algorithm (GA) is employed to deduce the orthogonal inputs and their responses from distributed point loads applied on the test model during calibration experiments. Time histories of these loads and their responses are then used to train the architecture of Adaptive Neuro Fuzzy Inference System, ANFIS. This ANFIS architecture is further employed for force prediction from the acquired acceleration responses during shock tunnel experiments. Testing of the experimental acceleration responses of 0° and 10° angle of attack experiments showed encouraging agreement for recovered aerodynamic coefficients with the accelerometer balance theory based predictions. These results clearly showed the necessity to consider multiple point loads and their acceleration responses for training the soft computing algorithm or calibration of the force balance. Further, use of only one point force and its responses, for training ANFIS, is not only seen to have discrepancy in prediction but also is noted to be non-unique due to choice of the loading point. Moreover, it is recommended to choose the loading point near the center of pressure for the tested experimental conditions to incur lower discrepancy in prediction using single point loading data for ANFIS training.

Shock-boundary layer interaction (SBLI) at hypersonic inlets can alter the flow pattern and impose adverse effects on engine operation if not controlled. A two-dimensional surface modificat...

This technical brief presents a flow separation mitigation device, called cavity-recirculator that can be used to control flow separation during shock wave–boundary layer interaction (SBLI) in high-speed intake flows. The cavity-recirculator isolates the flow separation bubble generated at the SBLI spot, thereby thinning the boundary layer and reducing the blockage of the inviscid stream in the duct. The device has a potential application in scramjet engine intakes/isolators. The cavity-recirculator was tested on a single-ramp-compression intake model in a hypersonic shock tunnel, in a freestream of Mach 8 (±0.1). The device operation and effectiveness were assessed by flow visualization and pressure measurements in the test model. The measurements and visualization displayed a mitigation of flow separation through an improved flow field with a single shock train and the absence of flow separation shock, in the inlet.

This article presents correlations for indirect measurement of skin friction inside a laminar separation bubble induced by hypersonic shock-boundary layer interaction (SBLI) on a flat plate. The correlations, based on parameters that are known to influence the SBLI region, were developed using exhaustive numerical and analytical studies. Experiments were conducted in a hypersonic shock tunnel at Mach 8.6 (±0.22) to measure surface heat-flux and pressure in the zone of SBLI on a flat plate, which were then used to supplement and validate the correlations. The data predicted by the correlations agreed reasonably well with that of exact solutions. The case studies contained non-reacting air, behaving as a perfect gas on a flat surface.

It is important to protect assets located within cavities vulnerable to incident shock waves generated by explosions. The aim of the present work is to explore if closed cell aluminum foams can mediate and attenuate incident shocks experienced by cavities. A small cavity of 9 mm diameter and 2 mm length was created within the steel end-wall of a shock tube and exposed to shocks, directly or after isolating by aluminum foam liners. Shock waves with incident pressure of 9&ndash, 10 bar travelling at a velocity of 1000&ndash, 1050 m/s were generated in the shock tube. Compared to the no-foam condition, the pressure induced in the cavity was either equal or lower, depending on whether the foam density was low (0.28 g/cc) or high (0.31 to 0.49 g/cc), respectively. Moreover, the rate of pressure rise, which was very high without and with the low density foam barrier, reduced substantially with increasing foam density. Foams deformed plastically under shock loading, with the extent of deformation decreasing with increasing foam density. Some interesting responses such as perforation of cell walls in the front side and densification in the far side of the foam were observed by a combination of scanning electron microscopy and X-ray microscopy. The present work conclusively shows that shocks in cavities within rigid walls can be attenuated by using foam liners of sufficiently high densities, which resist densification and extrusion into the cavities. Even such relatively high-density foams would be much lighter than fully dense materials capable of protecting cavities from shocks.

Surface-roughness caused by the residue of an ablative Thermal Protection System (TPS) can alter the turbulence level and surface heating rates on a hypersonic re-entry capsule. Large-scale surface-roughness that could represent an ablated TPS, was introduced over the forebody of a 120° apex angle blunt cone, in order to test for its influence on surface heating rates in a hypersonic freestream of Mach 8.8. The surface heat transfer rates measured on smooth and roughened models under the same freestream conditions were compared. The hypersonic flow-fields of the smooth and rough-surfaced models were visualized to analyse the flow physics. Qualitative numerical simulations and pressure measurements were carried out to have an insight into the high-speed flow physics. Experimental observations under moderate Reynolds numbers indicated a delayed transition and an overall reduction of 17–46% in surface heating rates on the roughened model.

The surface heat flux on a 100 mm diameter hypersonic sphere was reduced through surface roughness on its forebody. The test model was subjected to a hypersonic freestream of Mach 8.8 and Reynolds number 1.98 million/m, in a shock tunnel. Forebody surface heat transfer rates measured on smooth and rough spheres, under the same free-stream conditions, were compared. The comparison of heat flux indicated an overall reduction in surface heating rates on the rough model, which could be attributed to the delayed nose tip transition. The surface roughness on the forebody of the model generated miniature cavities. Stability of the free shear layer over the miniature cavities and entrapment of the destabilizing vortices in the cavities, make the flow over the rough test model more stable than the attached boundary layer over the smooth model, under transitional conditions.

A needle-free vaccine/drug injector that works by virtue of the impulse of a moving shock wave is presented in this communication. The device can deliver controlled micro-volumes of liquid vaccines into skin and soft tissue targets in human with minimal invasion. The operation of the injector was investigated by delivering a dyed liquid into human skin samples and soft tissue models. The depth of penetration of the liquid was examined by histology of the targeted human skin samples. The delivery mechanics and the depth of penetration were analyzed theoretically with an elastic model for the skin and a viscoelastic model for the soft tissue targets, and a good agreement with experiments was observed. The current liquid vaccine/drug delivery technique can reduce pain, trauma and contamination, and can offer a cost-effective, needle-free, health-care solution.

Accelerometer force balance (AFB), in conjunction with various force prediction methodologies, has been used in hypersonic flow regime. Present studies focus on its ability to capture small and large alterations in the force and moment coefficients. For this objective, shock tunnel experiments are conducted on a bi-conic model without and with hemispherical or sharp aerospike. A three component AFB is equipped to measure acceleration responses during the experiments. Adaptive Neuro Fuzzy Inference System (ANFIS) is employed herein for the force recovery. Aerodynamic coefficients obtained from ANFIS are noticed to have encouraging match with the AFB theory. It has been shown here that, AFB and recently developed ANFIS based force recovery methodology can precisely predict as small as 6.3% and as large as 38% change in the force along with its temporal variation. Hence, this study strengthens the use of a soft computing technique like ANFIS for predicting steady state and temporal variations of aerodynamic coefficients during shock tunnel testing of hypersonic configurations.

An acceleration-compensated skin-friction balance based on the floating-head technique was developed to measure skin friction in a hypersonic impulse facility. The balance consisted of measurement and acceleration units, the outputs of which can be coupled using a full-Wheatstone bridge to obtain pure shear output. The working of the balance was tested on a flat plate model exposed to a laminar flow with Mach number, stagnation enthalpy and Reynolds number of 8.2, 0.65 MJ kg−1 and 2.9 × 106 m−1, respectively. The measured wall shear stress agreed reasonably well with that predicted by Reynolds analogy.

This article presents a miniature shock wave driven micro-jet generator to deliver liquid drugs into human skin, to a controlled depth, with minimal invasion. The device can release the vaccine/drug to the depth of dermal blood vessels, without breaching much of the microcirculation system of dermis. The drug delivery technique is needle-free, which can reduce pain, trauma, and contamination besides minimal dosage and systemic exposure. The device can also be used to deliver liquid or colloidal drugs into soft tissues in human. The mechanical analyses of the device were carried out by analyzing the strength of the impulse of the shock wave, measuring the velocity of the generated jet and capturing the pressure exerted by the jet on the target. The penetrating ability of the jet was investigated by delivering it into sample of human skin and gelatin slabs. Theoretical analyses were carried out on the physics of the delivery and the predicted results had a close agreement with the experimental observations. The development can offer an important cost-effective solution to needle-free health care worldwide. Biotechnol. Bioeng. 2016;113: 2507-2512. © 2016 Wiley Periodicals, Inc.

Heat flux and pressure were measured on the internal walls of a scramjet engine at a hypersonic Mach number of 8 in a shock tunnel. Temperature-time history was recorded on model walls using fast-response thermocouples and the wall heat flux was deduced thereon from the temperature records. Pressure was measured at the same locations as that of heat flux using high-frequency pressure transducers. The surface measurements were used to analyze the internal flow field of the engine. The heat flux measurements revealed the regions of peak heating that may require additional thermal protection during the operation; the regions being the beginning of the constant area duct and the nozzle. The pressure measurements and the pertinent analysis indicated an optimum compression at intake through shock waves with a viable flow separation in the combustion chamber. The experimental data indicated an optimum design of the engine for a possible fuelled operation in future.

Data on surface heat flux is critical in all hypersonic missions due to the extent of risk and the penalty associated, when it is not properly accounted for. In the present study. an E-type coaxial thermocouple has been designed, fabricated, validated and benchmarked against a more established platinum thin film sensor. The study proves that coaxial thermocouples used in impulse facilities do not require cold junction compensation. The comprehensive study conducted in IIT Bombay Shock Tunnel (IITB-ST) has confirmed the performance, ruggedness and reliability of the coaxial thermocouple, ascertaining it to be an effective, impulse, heat flux sensor. (C) 2014 Elsevier Ltd. All rights reserved.

The aerodynamic environment in the test section of a hypersonic shock tunnel is very hostile as the high enthalpy flows prevail over the test model for a very short test time (similar to 1 ms). It calls for the requirement of the high-speed thermal sensors to survive in this harsh environment. Coaxial surface junction thermocouples (CSJTs) have the characteristics features of very high response times that can be used to capture highly transient temperature data during short duration hypersonic flows in the shock tunnel. The present study aims at the comparative performance assessment studies of three different surface junction probes (E, J and T-type) in a hypersonic shock tunnel at a flow Mach number of 8.2. All of them are mounted simultaneously in a rake along with a pitot-probe, in the test section of the tunnel where they experience a step heat load through a slug of test gas prevailing for 1 ms flow duration. Subsequently, the transient temperature histories are recorded at stagnation point of the junction probe and surface heat fluxes are predicted through one-dimensional heat conduction modeling. Side by side, stagnation heat flux is calculated independently through numerical simulations and analytical methods under same experimental flow conditions. The surface heat flux is recovered within a reasonable accuracy for E and T-type probes when experimental results are compared with numerical simulation and analytical solutions. In contrast, substantial deviations in surface heat flux value are observed for a J-type probe, which is mainly due to inconsistency in "thermal product (TP)" value of CSJT. However, they are quite sensitive in acquiring transient data during short time scale of measurements prevailing in the shock tunnel. The performance indicators such as "sensitivity and response time" for E-type CSJTs are found to be 58.96 mu V/degrees C and 21 mu s, respectively as compared to 43.82 mu V/degrees C and 29 us for J-type and 28.47 mu V/degrees C and 24 mu s for T-type, respectively. (C) 2017 Elsevier Ltd. All rights reserved.

Viscous drag on the internal surfaces of a notional scramjet engine model has been estimated through Reynolds analogy, using measured wall heat transfer rates, in a shock tunnel at a hypersonic Mach number of 8. The study has been carried out without fuel injection and at zero degree angle of incidence of the model with the freestream. The heat transfer rate measurements were carried out on the upper and lower internal surfaces of the engine employing fast response E-type thermocouples. Application of Reynolds analogy to the wall heat transfer rates yielded the skin friction coefficient, through which the viscous drag on the surfaces could be determined. The measurements predict the salient features of the flow field of the model and are a novel reference on the data to the researchers working in the area of slender-body, hypersonic aerothermodynamics.

This article presents a miniature shock wave driven micro-jet generator to deliver liquid drugs into human skin, to a controlled depth, with minimal invasion. The device can release the vaccine/drug to the depth of dermal blood vessels, without breaching much of the microcirculation system of dermis. The drug delivery technique is needle-free, which can reduce pain, trauma, and contamination besides minimal dosage and systemic exposure. The device can also be used to deliver liquid or colloidal drugs into soft tissues in human. The mechanical analyses of the device were carried out by analyzing the strength of the impulse of the shock wave, measuring the velocity of the generated jet and capturing the pressure exerted by the jet on the target. The penetrating ability of the jet was investigated by delivering it into sample of human skin and gelatin slabs. Theoretical analyses were carried out on the physics of the delivery and the predicted results had a close agreement with the experimental observations. The development can offer an important cost-effective solution to needle-free health care worldwide. Biotechnol. Bioeng. 2016;113: 2507-2512. © 2016 Wiley Periodicals, Inc.

A hemispherical model equipped with a three component accelerometer force balance has been tested in a shock tunnel at Mach 8.0 freestream conditions. A novel technique has been devised using the Artificial Neuro-Fuzzy Inference System (ANFIS) for recovering the forces experienced by the model during the experiments. Implementation of this methodology in calibration of the force balance showed encouraging agreement with the impulse forces recovered from the calibration tests. The same recovery procedure is then adopted to obtain the time history of the forces for 0[Formula: see text] and 15[Formula: see text] angle of attack experiments. The drag recovered in steady state is found to agree well with the conventional methods with minor discrimination for the lift and pitching moment. In light of the limitation of the accelerometer force balance theory due to the unaccountability of model dynamics, the force recovery technique proposed herein is found simple to implement and can be opted as a tool for prediction of the aerodynamic coefficients and force time histories.

A shock wave assisted biolistic (biological ballistic) device has been developed to deliver DNA/dr-ug-coated micro-projectiles into soft living targets. The device consists of an Nd:YAG laser, an optical setup to focus the laser beam and, a thin aluminum (Al) foil (typically 100 mu m thick) which is a launch pad for the micro-projectiles. The DNA/drug-coated micro-particles to be delivered are deposited on the anterior surface of the foil and the posterior surface of the foil is ablated using the laser beam with an energy density of about 32 x 10(9) W/cm(2). The ablation launches a shock wave through the foil that imparts an impulse to the foil surface, due to which the deposited particles accelerate and acquire sufficient momentum to penetrate soft targets. The device has been tested for particle delivery by delivering 1 gm size tungsten particles into liver tissues of experimental rats and in vitro test models made of gelatin. The penetration depths of about 90 and 800 mu m have been observed in the liver and gelatin targets, respectively. The device has been tested for in vivo DNA [encoding beta-glucuronidase (GUS) gene] transfer by delivering plasmid DNA-coated, 1-mu m size gold (Au) particles into onion scale, tobacco leaf and soybean seed cells. The GUS activity was detected in the onion, tobacco and soybean cells after the DNA delivery. The present device is totally non-intrusive in nature and has a potential to get miniaturized to suit the existing medical procedures for DNA and/or drug delivery.

This paper presents the measurement of side force, pitching, and yawing moments on a model, using an accelerometer force balance, in a short duration hypersonic shock tunnel. The test model is a blunt-nosed, flapped delta wing, mounted on a support sting through a force balance. The flexible rubber bushes constituting the balance allow the model to float freely on the sting during the test. The accelerometers were located in the model to record accelerations in the directions of interest. The model was tested in shock tunnel at Mach 8 at different angles of incidence with the freestream. Dynamic calibration of the test assembly was carried out for the acquisition of impulse response functions for the above components of force and moments, using an impulse hammer. The convolution technique was applied to derive the impulse response functions. The accelerometer outputs from the model in the hypersonic freestream were processed using the respective impulse response functions to derive the unknown aerodynamic force and moments. The newly adopted convolution technique has been found very effective for data reduction from accelerometer force balances developed for shock tunnel applications.

An accelerometer-based force balance was designed and developed for the measurement of drag, lift, and rolling moment on a blunt-nosed, flapped delta wing in a short-duration hypersonic shock tunnel. Calibration and validation of the balance were carried out by a convolution technique using hammer pulse test and surface pressure measurements. In the hammer pulse test, a known impulse was applied to the model in the appropriate direction using an impulse hammer, and the corresponding output of the balance (acceleration) was recorded. Fast Fourier Transform (FFT) was operated on the output of the balance to generate a system response function, relating the signal output to the corresponding load input. Impulse response functions for three components of the balance, namely, axial, normal, and angular, were obtained for a range of input load. The angular system response function was corresponding to rolling of the model. The impulse response functions thus obtained, through dynamic calibration, were operated on the output (signals) of the balance under hypersonic aerodynamic loading conditions in the tunnel to get the time history of the unknown aerodynamic forces and moments acting on the model. Surface pressure measurements were carried out on the model using high frequency pressure transducers, and forces and moments were deduced thereon. Tests were carried out at model angles of incidence of 0, 5, 10, and 15 degrees. A good agreement was observed among the results of different experimental methods. The balance developed is a comprehensive force/moment measurement device that can be used on complex, lifting, aerodynamic geometries in ground-based hypersonic test facilities.

Yawing moment, pitching moment and side-force on a blunt, triangular, lifting model were measured in a shock tunnel using an accelerometer balance at a hypersonic Mach number of 8. The measurements were carried out at different angles of incidence of the model with the freestream. The balance was instrumented with accelerometers to sense the model acceleration in the desired directions, and was equipped with a soft suspension system such that the model had a free flight during the tests in the shock tunnel. Pressure measurements on the surfaces of the model were carried out using high frequency pressure transducers to validate the output of the force balance. The moment and force coefficients obtained through both the measurement techniques have a good agreement reciprocally. The force and moment coefficients for the test model were analytically estimated using Newtonian theory to compare with the measured coefficients. The comparison between theory and experiments has been found quite encouraging. (C) 2012 Elsevier Ltd. All rights reserved.

A force balance to measure roll, lift and drag on a lifting aerodynamic body in an ultrashort-duration hypersonic test facility, such as a shock tunnel, has been developed and tested on a flapped, blunt-nosed, triangular lifting body at a freestream Mach number of 8. The flow total enthalpy and the freestream unit Reynolds number were 0.83 MJ kg(-1) and 0.98 million, respectively. The balance structure has a soft suspension that allows the model to have a free flight during the short-duration aerodynamic test. The balance was mounted inside the hollow model and was equipped with accelerometers to sense the aerodynamic moment and forces on the model. The measurements were carried out at different angles of incidence of the model and the acquired signals of the accelerometers were reduced to the aerodynamic moment and the force coefficients based on the theories of applied mechanics and aerodynamics. Also, the moment and force coefficients were theoretically calculated based on the Newtonian theory, which is an accepted analytical approach for hypersonic bodies. Good agreement has been observed between the experimental and the analytical results. The method of measurement of roll and lift, and the data on the rolling moment of a lifting body presented in this note are novel.

A chromel-constantan coaxial surface junction thermocouple has been designed, fabricated, calibrated, and tested to measure the temperature-time history on the surface of a body in a hypersonic freestream of Mach 8 in a shock tunnel. The coaxial thermocouple with a diameter of 3.25 mm was flush mounted in the surface of a hemisphere of 25 mm diameter. The hypersonic freestream was of a very low temperature and density, and had a flow time of about a millisecond. Preliminary test results indicate that the thermocouple is quite sensitive to low temperature-rarefied freestreams, and also has a response time of a few microseconds (≈5 μs) to meet the requirements of short duration transient measurements. The sensor developed is accurate, robust, reproducible, and is highly inexpensive.

IMPOSED bluntness at the nose of a hypersonic vehicle is necessary to alleviate the oncoming heat load. However, increased wave drag is the immediate consequence of the forced bluntness. Hence, research in the field of hypersonics is always centered on the reduction of wave drag encountered by the space vehicles during their ascent phase. Most of the drag-reduction techniques are directed towards modifying the flowfield ahead of the stagnation point. Among the drag-reduction techniques, retractable spike is the simplest and is an easy-to-implement technique; hence, the forward-facing aerospike technique has attracted many researchers to consider various issues. Various configurations of aerospikes were assessed by Menezes et al. [1] to arrive at the best configuration for drag reduction on a 120 deg apex angle blunt cone, and a flat-disc-tipped aerospike of unity L=D (spike length-to-cone base-diameter ratio) with a disc diameter of 1 4 D was observed to be the most efficient drag-reducing agent. Therefore, a similar flat-disctipped aerospike configuration is considered in the present study to evaluate its effect on drag of a 120 deg apex-angle blunt cone under various total-enthalpy conditions. An accelerometer-based force balance was used to measure drag on the model in a conventional hypersonic shock tunnel, IITB-ST (Indian Institute of Technology Bombay—Shock Tunnel), at low-enthalpy conditions (1:1 0:02 and 1:5 0:03 MJ=kg), and high-enthalpy tests (5 0:44 MJ=kg) were conducted on the same model in a free-piston-driven hypersonic shock tunnel, HST3. Flowfield modifications brought about by the disc-tipped spike were expected to depend on the total enthalpy of the flow, as such a dependence was observed in the case of drag-reduction studies using a fluidic spike [2]. Details of the experimental methodology and the results are presented in the following sections. II. Test Facilities, Model, and Force Balance

Ablation created by a Q-switched Nd:Yttrium Aluminum Garnet (Nd:YAG) laser beam focusing on a thin aluminum foil surface spontaneously generates a shock wave that propagates through the foil and deforms it at a high speed. This high-speed foil deformation can project dry micro- particles deposited on the anterior surface of the foil at high speeds such that the particles have sufficient momentum to penetrate soft targets. We used this method of particle acceleration to develop a drug delivery device to deliver DNA/drug coated microparticles into soft human-body targets for pharmaceutical applications. The device physics has been studied by observing the process of particle acceleration using a high-speed video camera in a shadowgraph system. Though the initial rate of foil deformation is over 5 km/s, the observed particle velocities are in the range of 900–400 m/s over a distance of 1.5–10 mm from the launch pad. The device has been tested by delivering microparticles into liver tissues of experimental rats and artificial soft human-body targets, modeled using gelatin. The penetration depths observed in the experimental targets are quite encouraging to develop a future clinical therapeutic device for treatments such as gene therapy, treatment of cancer and tumor cells, epidermal and mucosal immunizations etc.

We experimentally evaluated the impulsive motion of free-surface of water on impingement of shock-waves of moderate strength. This physical process creates the initial acceleration in shock-wave based micro-fluidic devices, which have promising medical and drug/DNA delivery applications. The velocities of the water interfaces were measured through real-time high-temporal/spatial resolution visualizations. Based on modified Tait equation-of-state and the concept of Reimann-invariants, an analytical expression was deduced to calculate the particle velocity behind the unloading wave. The experiments and analyses confirm that the mass motion behind the shock-wave accelerates to very high velocities, a requirement for effective momentum delivery in micro-jet devices. (C) 2015 AIP Publishing LLC.

Object.A pressure-driven continuous jet of water has been reported to be a feasible tool for neuroendoscopic dissection owing to its superiority at selective tissue dissection in the absence of thermal effects. With respect to a safe, accurate dissection, however, continuous water flow may not be suitable for intraventricular use. The authors performed experiments aimed at solving problems associated with continuous flow by using a pulsed holmium:yttrium-aluminum-garnet (Ho:YAG) laser-induced liquid jet (LILJ). They present this candidate neuroendoscopic LILJ dissection system, having examined its mechanical characteristics and evaluated its controllability both in a tissue phantom and in a rabbit cadaveric ventricle wall.Methods.The LILJ generator was incorporated into the tip of a No. 4 French catheter so that the LILJ could be delivered via a neuroendoscope. Briefly, the LILJ was generated by irradiating an internally supplied column of physiological saline with a pulsed Ho:YAG laser (pulse duration time 350 µsec; laser energy 250–700 mJ/pulse) within a No. 4 French catheter (internal diameter 1 mm) and ejecting it from a metal nozzle (internal diameter 100 µm). The Ho:YAG laser energy pulses were conveyed by an optical fiber (core diameter 400 µm) at 3 Hz, whereas physiological saline (4°C) was supplied at a rate of 40 ml/hour. The mechanical characteristics of the pulsed LILJ were investigated using high-speed photography and pressure measurements; thermal effects and controllability were analyzed using an artificial tissue model (10% gelatin of 1 mm thickness). Finally, the ventricle wall of a rabbit cadaver was dissected using the LILJ.Jet pressure increased in accordance with laser energy from 0.1 to 2 bar; this translated into a penetration depth of 0.08 to 0.9 mm per shot in the ventricle wall of the rabbit cadaver. The gelatin phantom could be cut into the desired shape without significant thermal effects and in the intended manner, with a good surgical view.Conclusions.The present results show that the pulsed LILJ has the potential to become a safe and reliable dissecting method for endoscopic procedures.

Although water jet technology has been considered as a feasible neuroendoscopic dissection methodology because of its ability to perform selective tissue dissection without thermal damage, problems associated with continuous use of water and the ensuing fountain-effect-with catapulting of the tissue-could make water jets unsuitable for endoscopic use, in terms of safety and ease of handling. Therefore, the authors experimented with minimization of water usage during the application of a pulsed holmium:yttrium-aluminum-garnet (Ho:YAG) laser-induced liquid jet (LILJ), while assuring the dissection quality and the controllability of a conventional water jet dissection device. We have developed the LILJ generator for use as a rigid neuroendoscope, discerned its mechanical behavior, and evaluated its dissection ability using the cadaveric rabbit ventricular wall.The LILJ generator is incorporated into the tip of a stainless steel tube (length: 22 cm; internal diameter: 1.0 mm; external diameter: 1.4 mm), so that the device can be inserted into a commercial, rigid neuroendoscope. Briefly, the LILJ is generated by irradiating an internally supplied water column within the stainless steel tube using the pulsed Ho:YAG laser (wave length: 2.1 microm, pulse duration time: 350 microseconds) and is then ejected through the metal nozzle (internal diameter: 100 microm). The Ho:YAG laser pulse energy is conveyed through optical quartz fiber (core diameter: 400 microm), while cold water (5 degrees C) is internally supplied at a rate of 40 ml/hour. The relationship between laser energy (range: 40-433 mJ/pulse), standoff distance (defined as the distance between the tip of the optical fiber and the nozzle end; range: 10-30 mm), and the velocity, shape, pressure, and average volume of the ejected jet were analyzed by means of high-speed camera, PVDF needle hydrophone, and digital scale. The quality of the dissection plane, the preservation of blood vessels, and the penetration depth were evaluated using five fresh cadaveric rabbit ventricular walls, under neuroendoscopic vision.Jet velocity (7.0-19.6 m/second) and pressure (0.07-0.28 MPa) could be controlled by varying the laser energy, which determined the penetration depth in the cadaveric rabbit ventricular wall (0.07-1.30 mm/shot). The latter could be cut into desirable shapes-without thermal effects-under clear neuroendoscopic vision. The average volume of a single ejected jet could be confined to 0.42-1.52 microl/shot, and there was no accompanying generation of shock waves. Histological specimens revealed a sharp dissection plane and demonstrated that blood vessels of diameter over 100 microm could be preserved, without thermal damage.The present pulsed LILJ system holds promise as a safe and reliable dissection device for deployment in a rigid neuroendoscope.

A three-component accelerometer balance system is used to study the drag reduction effect of an aerodisc on large angle blunt cones flying at hypersonic Mach numbers. Measurements in a hypersonic shock tunnel at a freestream Mach number of 5.75 indicate more than 50% reduction in the drag coefficient for a 120degrees apex angle blunt cone with a forward facing aerospike having a flat faced aerodisc at moderate angles of attack. Enhancement of drag has been observed for higher angles of attack due to the impingement of the flow separation shock on the windward side of the cone. The flowfields around the large angle blunt cone with aerospike assembly flying at hypersonic Mach numbers are also simulated numerically using a commercial CFD code. The pressure and density levels on the model surface, which is under the aerodynamic shadow of the flat disc tipped spike, are found very low and a drag reduction of 64.34% has been deduced numerically.

We experimentally examined interaction of blast waves with water-air/air-water interfaces through high-speed-real-time visualization and measurement of pressure across the waves. The underwater shock wave, which was expected to reflect totally at the water-air interface, was observed transmitting a shock front to air. Transmission of a blast wave from air to water was also visualized and evaluated. Underwater shock waves are used in several medical/biological procedures, where such unforeseen transmissions can result in detriments. The details provide a guideline to evaluate blast wave transmissions, which can induce tissue and brain injuries. The results explain mechanisms behind blast-induced traumatic brain injury. (C) 2014 AIP Publishing LLC.

A shock‐wave‐based biolistic device has been developed to deliver DNA/drug‐coated micro‐projectiles into soft living targets. The device consists of an Nd:yttrium aluminum garnet laser, equipped with a suitable optical setup and a thin aluminum (Al) foil (typically 100‐μm thick). The powdered vaccines to be delivered are deposited on the anterior surface of the foil and the posterior surface of the foil is ablated using the laser beam. The ablation launches a shock wave through the foil that imparts an impulse to the foil surface, due to which the deposited particles accelerate to high velocities that are sufficient to enable them to penetrate soft targets. The device has been tested for in vivo DNA delivery by delivering plasmid‐coated, 1‐μm size, gold (Au) particles into onion and tobacco cells. The GUS activity was detected in the onion and tobacco cells after the addition of an artificial substrate. The present device is totally nonintrusive in nature and has a potential to get miniaturized to suit the existing medical procedures for drug delivery.

A nonintrusive, minimally invasive, needle-less technique to deliver liquids into soft targets is presented. The technique uses a laser-induced shock wave to drive a liquid microjet at a very high speed such that the jet has sufficient momentum to penetrate soft targets. The method can be used to deliver liquid drugs into soft tissues in the human body. The liquid to be delivered is sandwiched between 200 mu m thick aluminum foil and a base plate with a perforation of 100 mu m diameter. The aluminum foil is ablated using an Nd:YAG laser beam in order to launch a shock wave through it. The shock wave from the foil is transmitted to the sandwiched liquid, which becomes pressurized by the shock propagation and emanates as a microjet through the perforation in the base plate. The microjet thus generated has a steady, average speed of over 200 m/s. The technique has been tested on gelatin models (5% gelatin), in which the jet penetrated to a depth of more than a millimeter. (C) 2009 [doi:10.1063/1.3245320]