Tip Injection Research Articles

Engineered deletions of HIV replicate conditionally to reduce disease in nonhuman primates.

Antiviral therapies with reduced frequencies of administration and high barriers to resistance remain a major goal. For HIV, theories have proposed that viral-deletion variants, which conditionally replicate with a basic reproductive ratio [R0] > 1 (termed "therapeutic interfering particles" or "TIPs"), could parasitize wild-type virus to constitute single-administration, escape-resistant antiviral therapies. We report the engineering of a TIP that, in rhesus macaques, reduces viremia of a highly pathogenic model of HIV by >3log10 following a single intravenous injection. Animal lifespan was significantly extended, TIPs conditionally replicated and were continually detected for >6 months, and sequencing data showed no evidence of viral escape. A single TIP injection also suppressed virus replication in humanized mice and cells from persons living with HIV. These data provide proof of concept for a potential new class of single-administration antiviral therapies.

Establishing a Virus-Induced Gene Silencing System in Lycoris chinensis.

Lycoris is an important plant with both medicinal and ornamental values. However, it does not have an efficient genetic transformation system, which makes it difficult to study gene function of the genus. Virus-induced gene silencing (VIGS) is an effective technique for studying gene functions in plants. In this study, we develop an efficient virus-induced gene-silencing (VIGS) system using the leaf tip needle injection method. The widely used TRV vector is constructed, and the Cloroplastos Alterados 1 (CLA1) and Phytoene Desaturase (PDS) genes are selected as visual indicators in the VIGS system. As a result, it is observed that leaves infected with TRV-LcCLA1 and TRV-LcPDS both show a yellowing phenotype (loss of green), and the chlorosis range of TRV-LcCLA1 was larger and deeper than that of TRV-LcPDS. qRT-PCR results show that the expression levels of LcCLA1 and LcPDS are significantly reduced, and the silencing efficiency of LcCLA1 is higher than that of LcPDS. These results indicate that the VIGS system of L. chinensis was preliminarily established, and LcCLA1 is more suitable as a gene-silencing indicator. For the monocotyledonous plant leaves with a waxy surface, the leaf tip injection method greatly improves the infiltration efficiency. The newly established VIGS system will contribute to gene functional research in Lycoris species.

Design optimization and flow analysis of discrete tip injection in a transonic compressor based on nonlinear harmonic method and endwall blockage attenuation

Discrete tip injection (DTI) shows great promise for improving the operating stability of transonic axial flow compressor (AFC) rotors. However, the design optimization of DTI remains a challenging task because of both the reliance on computationally expensive unsteady simulations to calculate its effects and the lack of a flow physics-based index for assessing operating stability. The present study introduces a nonlinear harmonic method for the rapid simulation of the dominant unsteady effects caused by a DTI device, and it proposes the unsteady shroud endwall blockage attenuation as an operating stability optimization index for DTI design based on analyzing the stall flow mechanism in transonic AFCs. On this basis, an efficient optimization method for DTI design is proposed in combination with an adaptive kriging-based optimization technique. This design optimization method is validated by the Coandă injector design for the transonic rotor National Aeronautics and Space Administration Rotor 37, with improved operating range and reduced injection mass flow pursued simultaneously by a comprehensive objective function. The optimal DTI design significantly reduces the stalling flow coefficient of the compressor by 4.46% at a small injection mass flow (0.72% of the compressor stalling mass flow), with a slight increase in the aerodynamic performance of the compressor. Detailed unsteady flow-field analysis shows that the main reason for the improved operating stability of the transonic AFC is a significant attenuation and delayed recovery of shroud endwall blockage, and the underlying flow mechanism is elucidated well.

Effect of multiple cavities and tip injection on the aerothermal characteristics of the squealer tip in turbine stage

For modern gas turbines, the blades of the first-stage high-pressure turbines are subject to significant aerodynamic and thermal loads. As the region where the aerothermal environment is most severe, the aerothermal performance of the blade tip is crucial. Either the tip injection or squealer tip with ribs can effectively improve the tip leakage flow distribution, and thus reduce the tip thermal loads, while the effect of the combination of the two remains to be explored, especially when the number of ribs increases. To further understand the combined effects of the rib number and the tip injections on the aerothermal characteristics, steady-state numerical simulations of the first stage turbine aerothermal field are carried out with varied rib numbers and tip injection configurations in the current study. The kω SST turbulence model was used to solve the 3D Reynolds-Averaged Navier-Stokes (RANS) equations. The heat transfer coefficient distributions and the leakage flow rate distributions are compared with those of the conventional squealer tip case. The results show that adding a rib inside the tip cavity would reduce the size of the reflux vortex near the leading edge of the blade (LE), and effectively reduce the averaged heat transfer coefficient on the tip. In addition, an increase in the rib number would make the coolant accumulate in the cavities, thus increasing the cooling performance. The averaged heat transfer coefficient of the coolant injected squealer tip with three ribs (Rib3C) decreases by 19.55%, compared with the performance of the conventional squealer tip, due to the combined action of adding the multiple ribs and the coolant injection. Comprehensively considering both improving the aerodynamic performance and reducing the blade tip heat load using TOPSIS analysis, the coolant injected squealer tip with two ribs (Rib2C) achieves the best overall performance. In general, ribs arranged in the upstream region of the blade would improve the coolant coverage by blocking the separation region at the cavity bottom. To improve the harsh tip thermal environment and reduce the tip aerodynamic loss, optimizing the rib layout inside the cavity and the coolant injection configurations is a practical solution.

Using Tip Injection to Stability Enhancement of a Transonic Centrifugal Impeller with Inlet Distortion

This paper aims to understand the effects of circumferential inlet distortion and tip injection on a transonic impeller performance and flow field. For distorted inflow, the impeller is subjected to a stationary 120-degrees circumferential total pressure distortion. Full annulus unsteady three-dimensional analysis has been used to study the inlet distortion and tip injection effects on the impeller performance, stability and flow field. The results show that the circumferential inlet distortion reduces the impeller total pressure ratio and adiabatic efficiency; however, it has no significant impact on the safe operating range. Unlike the inlet distortion, the tip injection considerably increases the operating range. According to the results, the distortion and tip injection effect on the compressor performance is mainly due to changes in tip leakage flow. The inlet distortion has unfavorable influences on the flow field, especially near the impeller tip; however, the tip injection ameliorates the flow field in this region. In both the clean and distorted inflow, the tip injection causes downstream shock transmission, weakening the shock-tip leakage interaction. Hence, stall inception is postponed, and the impeller stability is improved in the presence of the tip injection.

Contribution of Spicules to Solar Coronal Emission

Recent high-resolution imaging and spectroscopic observations have generated renewed interest in spicules’ role in explaining the hot corona. Some studies suggest that some spicules, often classified as type II, may provide significant mass and energy to the corona. Here we use numerical simulations to investigate whether such spicules can produce the observed coronal emission without any additional coronal heating agent. Model spicules consisting of a cold body and hot tip are injected into the base of a warm (0.5 MK) equilibrium loop with different tip temperatures and injection velocities. Both piston- and pressure-driven shocks are produced. We find that the hot tip cools rapidly and disappears from coronal emission lines such as Fe xii 195 and Fe xiv 274. Prolonged hot emission is produced by preexisting loop material heated by the shock and by thermal conduction from the shock. However, the shapes and Doppler shifts of synthetic line profiles show significant discrepancies with observations. Furthermore, spatially and temporally averaged intensities are extremely low, suggesting that if the observed intensities from the quiet Sun and active regions were solely due to type II spicules, one to several orders of magnitude more spicules would be required than have been reported in the literature. This conclusion applies strictly to the ejected spicular material. We make no claims about emissions connected with waves or coronal currents that may be generated during the ejection process and heat the surrounding area.

Tip injection effects on a transonic centrifugal impeller with various tip clearances in the presence of inlet distortion

Tip injection effects on a transonic centrifugal impeller with various tip clearances in the presence of inlet distortion

Performance Evaluation of Transonic Axial Flow Compressor under Distorted Conditions by Groove Casing Technique with Tip Injection and Surface Roughness Effects

The aerodynamic performance and pressure ratio of modern aircraft engine compressor are degrading due to unsteady flow distorted aerodynamic loads and complex phenomena in the blade tip. This paper attempts to improve the performance of modern axial flow transonic compressor stage under distorted flow conditions by incorporating the combination of groove casing, tip injection technique with surface roughness effects. This is performed for the Mach number ranging between 0.8 and 1.3. The obtained numerical results are compared with experimental studies and found to be in good agreement. Through the numerical analysis, the compressor stage flow interaction with the shock waves as well as vortex formation and boundary layer separation is studied in detail. While evaluating the performance of the axial flow compressor, more emphasis is given to the flow properties like pressure, density, temperature, velocity, etc. The performance improvement is observed at a particular Mach number for a specified aerodynamic flow property.

Stall Margin Improvement in an Axial Compressor by Continuous and Pulsed Tip Injection

Stall and surge are strong limitations in the operating range of compressors and thus one of the major limits of jet engine performance. A promising way to push the stability limit of compression machines is to inject a small amount of flow at the blade tip to alter the physical mechanism responsible for stall onset. This study focuses on the experimental performance of such a system. To do so, an axial compressor test bench was equipped with 40 actuators connected to an auxiliary pressurised air supply system. They were able to generate high-speed jet blowing just at the tip of the rotor blades. The opening of each actuator was controlled by an electromagnetic valve. This allowed generating continuous or pulsed jets with frequencies up to 500 Hz at different duty cycles. The performance of the control system was investigated for various control strategies, where the injected flow rate, the injection angle, the number of injectors, the jet frequency and the duty cycle were systematically varied. This paper is concluded by a study of the energy balance of the system for various configurations. To the best of the authors’ knowledge, this constitutes a rarely seen analysis in the literature.

Comparative Study of Tip Injection in a Transonic and Subsonic Compressor

Abstract Discrete tip injection is an effective method to enhance stability of compressors. This study compares the effects of injection parameters on compressor performance and underlying mechanisms in two different compressors. The transonic compressor is studied using unsteady simulations, and the subsonic compressor is mainly investigated with experiments. Results show that tip injection improves stable operating range by 35.6% and 77.9% for the transonic compressor and subsonic compressor, respectively, without decreasing compressor efficiency. The effects of circumferential coverage percentage and injector throat height on compressor stability are similar in the two compressors when the injection velocity is double the velocity of the main flow. The optimal injector throat height which is normalized by the tip clearance size is the same for the two compressors, and the best circumferential coverage percentage for the subsonic compressor is lower than that in the transonic compressor. For the two compressors, the adaption of the main flow to the discrete tip injection is unsteady, and the hysteresis effect that the recovery of tip blockage lags behind the recovery of tip leakage vortex accounts for the improved stability using partial coverage of injection. The injection efficiency, which is defined to quantify the improved quality of the flow field in the injection domain, is proven to determine the stall limits by studying the effects of different injection parameters. The guidelines built in the subsonic compressor can be used in the transonic compressor to design tip injection, but the optimal values of some injection parameters should be reconfirmed.

Effect of Multiple Ribs and Tip Injection on the Aerothermal Characteristics of the Squealer Tip in Turbine Stage

Effect of Multiple Ribs and Tip Injection on the Aerothermal Characteristics of the Squealer Tip in Turbine Stage

546 Antegrade in-stent CTO recanalization

Abstract Methods and results A 64-year-old man with prior PCI and stent of proximal LAD due to an anterior ST-elevation myocardial infarction (STEMI) presented with exertional angina (CCS III), despite optimal medical therapy (OMT). The echocardiogram showed a dilatated left ventricle with anterior and apical akinesia and a severely reduced left ventricle ejection fraction. Coronarography was performed and a chronic total occlusion was found at the proximal edge of the stent previously implanted in the proximal LAD, with a thin tapered entry (J-CTO score 1). Moderate angiographic disease was present in the circumflex (LCX) and in the right coronary artery (RCA). Interventional collaterals were absent. Dobutamine stress echocardiogram was performed to unmask myocardial viability. Indeed, during intravenous Dobutamine administration, we registered an increase in the left ventricle function, whereas only apex remained still akinetic. Accordingly, the patient underwent LAD CTO PCI using a 7 Fr EBU 4.0 guiding catheter, via right femoral artery access. The RCA ostium was engaged with a 6 Fr Judkins right 4.0 guiding catheter, via right radial artery access. Antegrade wire escalation technique was attempted. Due to scarce support, a 7 Fr Guidion guiding catheter extension and a Corsair microcatheter were placed in the proximal LAD. Antegrade crossing was very difficult due to intrastent high plaque burden. The occlusion was crossed with an Asahi Conquest Pro 9 guidewire. Subsequently, an Asahi Gaia third guidewire was advanced through the intrastent segment and then in the distal part of LAD. The advance of microcatheter was challenging but successfully achieved taking advantage of the low profile, high torqueability and trackability of the Asahi Corsair Pro microcatheter. Microcatheter tip injection confirmed the correct position in the vessel’s true lumen. An Asahi Grand Slam guidewire was placed in the distal LAD to provide extra support for delivery of interventional devices. The lesion was pre-dilated with progressively larger balloon, starting from a 1.1 mm diameter semi-compliant over-the-wire balloon (OTW). Two stents were implanted with a minimal overlap at the distal edge of the proximal stent (Resolute Onyx 3.0 × 38 mm and 2.5 × 24 mm). The result was improved with stents high-pressure post-dilatation and with selective intracoronary adenosine and nitroglycerin administration with final Thrombolysis in Myocardial Infarction (TIMI) grade 3 flow. The total amount of contrast media used was 210 ml. The total procedure time was with 125 min with 45 min of fluoroscopy. No complications occurred. Conclusions CTO PCI still represents one of the most challenging subsets of coronary interventions despite the improvement in technology and techniques. Although data regarding percutaneous PCI CTO are still inconsistent, successful CTO recanalization has been associated with relief of angina and ischemia-related dyspnoea (Werner at al., 2018). In stable patients CTO PCI has been associated with a lower risk of death, stroke, and coronary artery bypass grafting and less recurrent angina pectoris in some registry studies (Christakopoulos et al., 2015). Additionally, CTO PCI increased left ventricle function in a subgroup of patients with LAD CTO (Henriques et al., 2016). Conversely, randomized multicentre failed to demonstrate a superiority of CTO PCI medical to OMT in terms of major adverse cardiac events (MACE) and all-cause mortality.

Rotating tip clearance asymmetry and role of endwall injection in stability desensitization of a transonic fan

The current study is aimed at understanding the effect of rotating tip clearance asymmetry on the operability and performance of a transonic compressor. Another objective of this investigation is to determine the influence of tip injection on reducing the detrimental effects of clearance asymmetry. Three dimensional unsteady Reynolds-averaged Navier–stokes simulations have been performed from choke to stall for different arrangements of non-uniform blade heights in a transonic fan. Furthermore, numerical computations have been conducted with endwall injection of air. The numerical results have been validated against experimental data. Results show that having the same mean tip clearance, the asymmetric compressor is less stable than the axisymmetric configuration. However, the peak pressure rise is found to be almost linearly correlated to the mean tip clearance for both the axisymmetric and asymmetric compressors. It is found that tip injection can desensitize the compressor to the tip clearance asymmetry. Results further reveal that tip clearance asymmetry does not change the compressor path to instability. However, endwall injection is found to be able to change the compressor stalling mode. Investigations concerning rotating non-uniformity (caused by non-uniform blade heights) are very few in open literature. The obtained results can assist in predicting the effect of rotating tip clearance asymmetry on the stability and performance of high-speed compressor rotors. Furthermore, the results uncover how tip injection can desensitize the compressor stability and affect its path into instability, which is one of the most important questions in the turbomachinery world.

The \u201cDirect tip injection in occlusive lesions (DIOL)\u201d fashion

BackgroundThe successful intervention for peripheral artery disease is limited by complex chronic total occlusions (CTOs). During CTO wiring, without the use of intravascular or extravascular ultrasound, the guidewire position is unclear, except for calcified lesions showing the vessel path. To solve this problem, we propose a novel guidewire crossing with plaque modification method for complex occlusive lesions, named the “Direct tip Injection in Occlusive Lesions (DIOL)” fashion.Main textThe “DIOL” fashion utilizes the hydraulic pressure of tip injection with a general contrast media through a microcatheter or an over-the-wire balloon catheter within CTOs. The purposes of this technique are 1) to visualize the “vessel road” of the occlusion from expanding a microchannel, subintimal, intramedial, and periadventitial space with contrast agent and 2) to modify plaques within CTO to advance CTO devices safely and easily. This technique creates dissections by hydraulic pressure. Antegrade-DIOL may create dissections which extend to and compress a distal lumen, especially in below-the-knee arteries. A gentle tip injection with smaller contrast volume (1–2 ml) should be used to confirm the tip position which is inside or outside of a vessel. On the other hand, retrograde-DIOL is used with a forceful tip injection of moderate contrast volume up to 5-ml to visualize vessel tracks and to modify the plaques to facilitate the crossing of CTO devices. Case-1 involved a severe claudicant due to right superficial femoral artery occlusion. After the conventional bidirectional subintimal procedure failed, we performed two times of retrograde-DIOL fashion, and the bidirectional subintimal planes were successfully connected. After two stents implantation, a sufficient flow was achieved without complications and restenosis for two years. Case-2 involved multiple wounds in the heel due to ischemia caused by posterior tibial arterial occlusion. After the conventional bidirectional approach failed, retrograde-DIOL was performed and retrograde guidewire successfully crossed the CTO, and direct blood flow to the wounds was obtained after balloon angioplasty. The wounds heeled four months after the procedure without reintervention.ConclusionsThe DIOL fashion is a useful and effective method to facilitate CTO treatment.

Implementation of stability-enhancement with tip air injection in a multi-stage axial flow compressor

Tip air injection for stall margin extension is experimentally investigated in a multi-stage axial flow compressor. By comparing the stall margin improvement (SMI) under tip air injection in different stages, injected air only upstream from the first stage can causes a 20% SMI. This is because stall inception appears in the first stage. From the trend curve of SMI versus injected momentum ratios applied in the first stage, two demarcation points are found that separate the curve into micro, macro, and overlarge injections. Micro injection with a small SMI only weakens the tip leakage flow. Macro and overlarge injections influence both the tip leakage flow and mainstream flow, which contribute to a large SMI. However, overlarge injection causes the second stage to stall first, and causes the SMI to remain constant with further increases in the injected momentum ratio. The outlet axial velocity and flow angle measured using a five-hole probe indicate that with the overlarge injection in the first stage, the separation of the rotor blade passage in the second stage is more adverse than those in the other stages. The adverse passage separation originating from the hub region results in the second stage losing its working capability and stalling first. Moreover, at this point, the blade tip injection in the second stage has no additional effect on the extension of the stall margin.

Investigation of the tip injection for stall control in a transonic compressor with inlet distortion

Experimental studies have shown that tip injection upstream of the rotor can extend its operational range when subjected to circumferential inlet distortion. Typically, injectors are placed uniformly around the annulus. However, such arrangement consumes a large amount of high-pressure air and decreases the overall efficiency of the compression system. The aim of this paper is to minimise the amount of the injected air by determining the most effective circumferential location for the injector. In this study, NASA stage 35 was used as the test case. The experiment was conducted with a circumferential total pressure distortion of 120 degrees. In the first part of this paper, numerical simulations were compared against the experimental data and good match was obtained. In the second part, tip injection at three different positions were tested: the clean flow region (Position 1), the distorted region (Position 2) and the border between the clean and distorted regions (Position 3). It was found that a mild injection (0.66% of the main flow) at Position 2 and Position 3 can extend the stall margin by 1.8% and 2.7%, respectively. No obvious improvement was observed for the injection at Position 1. With a larger injection of 1.5% of main flow at Position 3, the stall margin improved further with no efficiency loss.

Novel Needle for Intravitreal Drug Delivery: Comparative Study of Needle Tip Aspirates, Injection Stream and Penetration Forces.

PurposeTo study the efficacy of a novel needle for intravitreal injection (IVI) in comparison to the conventional needle under experimental conditions.MethodsThe newly designed 30-gauge (G) needle (NDN) (EP 18158 542.3, patent pending) with occluded outer orifice and a side port for drug delivery was compared to the conventional standard hypodermic 30 G needle for IVI (SHN). An animal study to obtain needle tip aspirates was performed on 10 albino rat eyes. During IVIs, cellular content, which was cut by the needle tip, was aspirated. Cellular material was studied in regard to cell types and their quantity. The injection stream was studied using trypan blue dye in vitro and pig cadaver eyes. The penetration force was tested on polyurethane Testing Foil Strips PU 04 (Melab, Leonberg, Germany) by applying a velocity of 100 mm/min. The results were analyzed using descriptive statistics, correlation matrices and t-test methods with p<0.05 as statistically significant.ResultsCytological analysis of the needle aspirates showed the presence of cellular content in each case. The amount of conjunctival, ciliary body epithelial cells and granulated basophilic protein sediments (sign of cellular damage) in the case of the NDN tips was significantly lower compared to the SHN. The average penetration force of the NDN was 0.791 N, and in the case of the SHN was 0.566 N. The injection stream study revealed a difference in the initial injection phase between the two needle types, although the diffuse filling of the vitreous area which surrounded the needle tip appeared to be similar.DiscussionThe NDN demonstrated superior performance with regard to a significantly reduced number of cells being captured by the needle tip. Delivery of the injected fluid into the vitreous cavity was comparable. In order to investigate superior properties of the NDN needle design, further studies with improved prototypes would be necessary.

Effect of tip injection on the flow characteristics of an aeroengine compressor rotor

Existing experiments, simulations, and analysis have shown that the flow field of the blade tip has a significant effect on rotating stall and acoustic resonance in aeroengine compressors. Based on the numerical simulation of NASA rotor 37, the steady influence of air injection at blade tip was investigated in this investigation. The results show that the injected flow could obviously extend the stability margin of the axial compressor to varying degrees. The tip injection reduces the blockage caused by the tip leakage, and reduces the backflow in the trailing edge area of the blade tip, thereby delaying the occurrence of stall. Furthermore, in this paper, different types of rotors are constructed to verify the effect of injection parameters on the stability extension. The results show that the improvement of rotor stall margin is positively correlated with the injector inlet total pressure, and when the injector inlet flow conditions are of the same magnitude, the improvement of the rotor stall margin is negatively related to the distance between the injector and the leading edge of the blade.

Suprazygomatic maxillary nerve block: an ultrasound and cadaveric study to identify correct sonoanatomical landmarks.

Following an ultrasound-guided SMB with dye injection on 2 embalmed cadavers, pre-tragal face-lift style incision with a full thickness flap dissection was performed allowing accurate visualization of the bony landmarks being used for sonography and identification of the location of the injected dye. This study identifies the correct sonoanatomic landmarks as the maxilla and the coronoid process of the mandible which suggests that the block needle tip and local anesthetic injection are within the infratemporal fossa as opposed to the previously reported pterygopalatine fossa. An improved understanding of the sonoanatomy will aid clinicians who are learning, performing and teaching the ultrasound-guided suprazygomatic approach to the maxillary nerve block.

Gas dynamic-thermal-concentration fields and evaporation process of quartz particles in Ar–H2 inductively coupled plasma

The gas dynamic-thermal-concentration fields and evaporation process of quartz particles in the TICP torch of argon–hydrogen plasma have been studied. The effects of different methods of supplying hydrogen on the hydrogen concentration and gas temperature distributions, as well as on the vortex flow patterns have been discussed. The particle injection conditions in the pure argon and argon–hydrogen plasma have been determined. The dependences of the axial gas temperature and velocity distributions on the hydrogen volume fraction, flow rate of central gas and particle feed rate have been established. The effect of hydrogen volume fraction and different methods of supplying hydrogen on the evaporation degree of quartz particle in the TICP torch has been determined. The influences of the particle injection conditions (flow rate of central gas, probe tip position and injection patterns) on the evaporation degree in the TICP torch have also been evaluated. The specific heat cost for quartz particle evaporation has been calculated to evaluate the utilization efficiency of thermal energy.