Assisted Injection Research Articles

It's time to allow assisted injection in supervised injection sites.

KEY POINTS Assisted injection is necessary to ensure equitable access to supervised injection sites based on individuals’ health care needs, not their capacity to inject. About 90 supervised injection sites have been implemented in Europe, Australia and North America; these include Insite and the

Discretization of three-dimensional free surface flows and moving boundary problems via elliptic grid methods based on variational principles

A new boundary-fitted technique to describe free surface and moving boundary problems is presented. We have extended the 2D elliptic grid generator developed by Dimakopoulos and Tsamopoulos (2003) [19] and further advanced by Chatzidai et al. (2009) [18] to 3D geometries. The set of equations arises from the fulfillment of the variational principles established by Brackbill and Saltzman (1982) [21], and refined by Christodoulou and Scriven (1992) [22]. These account for both smoothness and orthogonality of the grid lines of tessellated physical domains. The elliptic-grid equations are accompanied by new boundary constraints and conditions which are based either on the equidistribution of the nodes on boundary surfaces or on the existing 2D quasi-elliptic grid methodologies. The capabilities of the proposed algorithm are first demonstrated in tests with analytically described complex surfaces. The sequence in which these tests are presented is chosen to help the reader build up experience on the best choice of the elliptic grid parameters. Subsequently, the mesh equations are coupled with the Navier–Stokes equations, in order to reveal the full potential of the proposed methodology in free surface flows. More specifically, the problem of gas assisted injection in ducts of circular and square cross-sections is examined, where the fluid domain experiences extreme deformations. Finally, the flow-mesh solver is used to calculate the equilibrium shapes of static menisci in capillary tubes.

Water Assisted Injection Molding for Single and Multi-branched Tubular Components

To produce hollow polymeric parts with complex geometries the Fluid Assisted Injection (FAI) technology is currently used. In this technology water and gas can be employed with or without the aid of a projectile. The process consists in the injection of water at high pressures, after the closing of the mold and polymer injection, and up to the filling of the whole molding zone. The injection of water at high pressures will force the polymer from the core to be expelled to a reservoir. This material expulsion is possible, not only thanks to the high water pressures, but also because the polymer is still in a viscous state, thus facilitating the evacuation. Even though the FAI technology is by direct injection of water/gas or with aid of a projectile, there is a common limitation, which is the inability to produce hollowed parts with forking channels. However, even if creating these branches is possible, there is the impossibility of them being geometrically complex and/or extensive. In these cases, the branches are created with inserts inside the mold, meaning that they will always be limited by a molding insert, and not controlled by the water jet. For cases where it is desired to add complex and/or extensive ramifications, subsequent steps of production and assembling must be added, influencing the overall production time. This work aims, therefore, at studying a new approach for the production of hollow parts with extensive branched channels and complex geometries within a single injection cycle, and thus eliminating subsequent processes that are currently required. The first approach is the application of several water injectors, guided towards the respective branches where hollow sections are intended to be produced. This innovation will have an impact on the serial production of high complexity tubular type parts, reducing the production time with the elimination of subsequent processes. Furthermore, a saving of raw materials is achieved by eliminating the necessity of a creation of additional molds. In this work, a detailed experimental study of the water assisted injection process was done to serve as a knowledge base to the concept of the new process named Multi-Path.H2O.

Instantaneous coprecipitation of polymer/drug microparticles using the supercritical assisted injection in a liquid antisolvent

In this work, the supercritical assisted injection in a liquid antisolvent (SAILA) has been proposed as a new technique to produce composite microparticles for drug controlled release. Coprecipitation has been attempted for different non-steroidal anti-inflammatory drugs (Diclofenac, DF, Piroxicam, PX, and Indomethacin, ID) using poly-lactic-co-glycolic (PLGA) as the polymer matrix; acetone has been used as the liquid solvent and water as the liquid antisolvent. Coprecipitation was successful in all the cases and encapsulation efficiency ranged between 50 and 97%. The effect of operating parameters, such as the polymer/drug ratio, polymer concentration, injection temperature and pressure on particle morphology and drug release rate has been studied considering the system PLGA/Piroxicam. SEM analysis indicated that non-coalescing spherical microparticles formed by PLGA/PX were produced by SAILA at fast mixing conditions (higher injection pressure and higher temperature) and high polymer/drug ratios (20/1 and 10/1). All coprecipitates showed a sharp particle distribution, with diameters ranging between about 0.28 and 2.50μm.SAILA composite microparticles have been characterized by X-ray, FT-IR, EDX and UV–vis analysis. PLGA/PX coprecipitates showed a prolonged release, about 7 times slower than the physical mixture of the same compounds; moreover, the polymer/drug ratio and the concentration of polymer in the solvent revealed to be a controlling parameter for drug release. The Hoffenberg’s equation has been used to describe experimental data, showing a fair good agreement with PX release data.

Mechanism and solutions of appearance defects on microfluidic chips manufactured by UV-curing assisted injection molding

Abstract A novel method for the chemical manufacturing UV-curing assisted injection molding was proposed in this paper. A prototype of UV-curing injection molding apparatus has been manufactured. By using the prototype, we have successfully fabricated microfluidic chips, which can be practically applied in micro mixing experiments. Similar to the thermoplastic parts molded by traditional injection molding, the appearance defects such as bubbles also occurred on products fabricated by UV-curing injection molding. The generation process of bubble defect has been observed and captured through the visualization device. Because there is no gas produced in the polymerization chemical reaction, the shrinkage was considered to be the essential reason of bubble defect. In this paper, the solution of bubble defect was studied by employing single factor control variable method from the aspects of process parameters, materials, and mode of irradiation. It was noted that the bubble defect could be improved by increasing holding pressure, reducing irradiation intensity, and improving viscosity. Nevertheless, the achievement of process parameters was limited. On equal experimental conditions of process, equipment, and material, results revealed that the dynamic irradiation pattern can improve the feeding capacity significantly in UV-curing injection molding. It is further demonstrated that the bubble defect is caused by the polymerization shrinkage. Eventually, we obtained the microfluidic chips with good surface quality, high dimensional accuracy, and high transparency by UV-curing injection molding. Moreover, it provides a feasible high efficiency and low cost manufacture technology for microfluidic chips in the future.

Reduction of Injection Moulded Plastic Part Warpage Using Advanced Gas Assisted Injection Moulding

Dimensional and shape accuracy are the basic quality criteria of almost every injection moulded plastic part, manufactured in the engineering industry. They are dependent on many production conditions as part and moulding tool design, material structure properties and injection parameters. Generally, it is very difficult to achieve high geometrical accuracy during injection moulding, therefore, dimensional tolerances for plastic parts are usually many times larger than in the case of metals. However, according to requirements of the engineering industry, demands for the plastic parts dimensional accuracy keep growing permanently, what also extends to the growing shape complexity of the produced parts. Due to this tendency, engineers must look for more and more advanced solutions to meet market requirements and keep the competitiveness of their product. In consonance with all this, this paper presents a case study where the progressive gas assisted injection moulding is used as a solution for the plastic part warpage reduction while any other conventional methods failed. The study is performed making use of part from the automotive industry, initially produced with unacceptable deformations. In the first step, the real manufacturing state was studied to determine the warp behaviour. Subsequently, the process parameters and cooling conditions were unsuccessfully modified while trying to reduce deformations. Nevertheless, these were effectively eliminated by the only application of internal gas support to the melt injection phase. A numerical modelling based on Finite Volume and Finite Element Method was also used in the case study in order to mathematically represent the fluid, thermal and mechanical processes during the process of injection moulding.

Mechanical Benefits of Gas Assisted Injection Moulding Application in Design of Structural Parts

Due to of many advantages and specific properties plastics are gradually becoming the most widely used materials in the engineering industry. In the last years, more and more metal parts are converted to plastic, in the cases of mechanically loaded parts as well. However, the usage of plastic is limited by its mechanical properties and production possibilities. Conventional injection moulding as the most productive plastic part production technology mostly enables the manufacturing of thin-wall parts with uniform wall thickness, what restricts full-fledged utilization of plastics. In this study, the benefits of progressive gas assisted injection moulding is investigated in order to produce plastic parts with higher mechanical properties. The paper presents complex study with respect to structures generated in material during gas penetration state, orientation of reinforced short fibres, stress relaxation behaviour, notch effect of rough gas channel surface, producible cross-section profiles with high moment of inertia and undesirable production effects, which can occur during gas aided moulding technologies. Finally, the mechanical properties of specimen produced by conventional and gas-assisted injection moulding were compared using numerical analyses. For comparison, integration of two numerical solver - FVM for fluid analysis of plastic/gas injection and FEM for structural analysis of specimen strength/stiffness were used.

BRTO assisted endoscopic Histoacryl injection in treating gastric varices with gastrorenal shunt

Aims: We evaluated the feasibility, efficacy and safety of a novel technique of balloon-occluded retrograde transvenous obliteration (BRTO) assisted endoscopic Histoacryl (N-buthyl-2-cyanoacrylate) injection.Material and methods: A total with 11 patients were enrolled and analyzed in this single center, open-label, prospective study. Patients with high-risk gastric varices (defined as fundal varices, large GV (>5 mm), presence of a red spot, and Child-Pugh score C) and concurrent gastrorenal shunt underwent endoscopic Histoacryl injection while the gastrorenal shunt was temporarily occluded with an occlusion balloon. Feasibility, hemostatic effect, intra- and postoperative complications, and varices recurrence were evaluated.Results: All procedures were successfully done per protocol. Except for one patient who underwent rescue Histoacryl injection due to residual varices, single therapy was sufficient to eliminate gastric varices in ten patients. Intra-operative hemorrhage occurred in one case and was stopped after additional Histoacryl injection. One patient was confirmed to have treatment-related fungemia. No death or major complications occurred, including ectopic embolism, worsening of hepatic and renal function, etc. No recurrence of the varices was found during a median follow-up time (mean ± SD) of 228 ± 153 days.Conclusions: BRTO assisted endoscopic Histoacryl injection is effective and safe for patients with high-risk gastric varices and concurrent gastrorenal shunt.

Intervention improves assisted conception intracytoplasmic sperm injection outcomes for patients with high levels of sperm DNA fragmentation: a retrospective analysis.

Sperm DNA fragmentation (SDF) is used in assisted reproductive technology (ART) programs as an indicator for sperm quality, although there is still a lack of consensus as to its clinical utility. In this retrospective study, we examined intracytoplasmic sperm injection (ICSI) outcomes of 1924 infertile patients who underwent SDF analysis using the sperm chromatin integrity test. ART patients were classified as having low [DNA fragmentation index (DFI) <29%] or high SDF (DFI ≥29%) and by whether or not an intervention [physiological intracytoplasmic sperm injection (PICSI), intracytoplasmic morphologically selected sperm injection (IMSI), testicular sperm extraction (TESE)/testicular sperm aspiration (TESA), frequent ejaculation] was performed. High SDF patients who did not have an intervention had a lower fertilization rate and poorer clinical outcomes from blastocyst transfers as compared with low SDF patients; the fertilization rate was 66.0% vs. 70.2% (p=0.042), single embryo transfer (SET) fetal heart pregnancy rate was 28.5% vs. 45.2% (p=0.042), and SET live birth rate was 24.9% vs. 40.6% (p=0.060), respectively. Furthermore, high SDF patients who had an intervention had significantly improved blastocyst transfer outcomes, similar to those of low SDF patients; the SET live birth rate for high SDF intervention patients was 43.8% as compared with 24.9% for high SDF no intervention patients (p=0.037) and 40.6% for low SDF patients (p=0.446). Analysis of the three main intervention subgroups for high SDF patients revealed that TESE/TESA patients had the highest SET live birth rate; in comparison with 24.2% for high SDF patients who did not have an intervention, PICSI patients had 38.3% (p=0.151), IMSI patients had 28.7% (p=0.680), and TESE/TESA patients had 49.8% (p=0.020). Our data suggest that SDF results indicate ICSI outcomes and that patients who have high SDF benefit from an intervention.

(Invited) Trench-Gated MOSFET Instability Caused by High Temperature Reverse-Bias Stress

The trench-gated MOSFET is widely used in power management applications because of its ultra-low on resistance [1]. Studies of trench-gate MOSFET reliability and degradation of blocking voltage and leakage current as well as edge termination effects are becoming increasingly important as the device dimensions shrink and its applications are diversified. The HTRB (high temperature reverse-bias) and HAST (highly accelerated temperature & humidity stress test) are often used in reliability assessment of planar discrete power MOSFETs [2] and are currently used in trench-gated MOSFET. The both HTRB stress and HAST stress apply a reverse bias voltage on the drain side with the source and gate grounded at elevated temperature in a MOSFET device. However, the HAST stress is at 85% HR relative humidity under pressure condition. The possible failure modes for HTRB and HAST stress are IDSS (drain to source) leakage current increase or shift, breakdown voltage shift or degradation, and Vth (threshold voltage) shift or instability. The failure mechanism under various failures is complex. They depend on not only device design and process, but also package process and its materials such as mold compound, as well as interaction between device and package. In this paper, we discuss the instability of n-channel trench-gated MOSFET under HTRB and HAST reliability stresses. The devices are packaged by using state-of-the-art “low pitch” wafer-level-chip-scale package (WLCSP) without the use of mold compound or leads frame. We have observed that the HTRB and HAST stress increases gate oxide interface trap density. However humid HAST stress is observed to further introduce mobile positive charge in the gate oxide of the trench-gated MOSFET. This positive charge is argued to comprise protons (H+s) [3]. The proton is generated through electric-field assisted interaction and hole injection into the gate oxide at the bottom of the trench. The mobility of these protons is observed to cause gate-voltage induced modulation in the threshold voltage and leakage current of the trench-gated MOSFET. In order to determine the mechanism by which H+s are introduced in the oxide, SEM inspection of the n-channel trench-gated MOSFET deprocessed to passivation showed the presence of passivation cracks in the device’s edge termination which cause moisture penetrated in the device during the HAST stress. Furthermore, the experimental and simulation results lead us to conclude that in this study we are observing negative bias temperature instability (NBTI) in a parasitic p-MOSFET structure arising at the bottom of the trench in an n-channel trench-gated MOSFET during HTRB stress [4]. The NBTI is enhanced by the presence of moisture in the oxide.

Role of FNAC mapping to guide directed sperm retrieval in infertile males for in-vitro fertilisation (IVF)

Background: Focal areas of spermatogenesis may exist in men even with small atrophic testis, raised follicle stimulating hormone (FSH) and in men previously considered to be having absence of spermatogenesis such as sertoli cell only syndrome. The study conducted by us has evaluated the regional differences in spermatogenesis by fine needle aspiration cytology (FNAC) mapping according to a standard template. This study aims at finding a possibility of directed sperm retrieval from region with better spermatogenesis for use in assisted reproduction techniques and intra-cytoplasmic sperm injection. Aimsand Objectives: The study was conducted with an aim to compare histological grading of spermatogenesis in testicular tissue by FNAC and biopsy in infertile males and to map the pattern of spermatogenesis in the testis of infertile males. Materials and Methods: Forty azoospermic men were taken into study and everyone underwent FNAC from eight different segments of one testis. They further underwent open biopsy from the segment, which showed better spermatogenesis. Results of FNAC and biopsy were compared. Results: Frequency of normal spermatogenesis was equivalent in all segments of testis by FNAC mapping (P value = 0.986). Sperm detection rate was 90% by eight-segment FNAC mapping in azoospermic participants. Correlation between results of FNAC and biopsy showed 85% concordance and 15% discordance. The eight-segment FNAC mapping showed sensitivity of 100%, specificity of 44.5%, and accuracy rate of 87.5% in detecting normal spermatogenesis. Conclusion: It is recommended to do FNAC mapping for every nonobstructive azoospermic subject, before undergoing retrieval procedure for better localization of spermatogenesis.

Ultrasonically-assisted Polymer Molding: An Evaluation

Energy reduction in extrusion and injection molding processes can be achieved by the introduction of ultrasonic energy. Polymer flow can be enhanced on application of ultrasonic vibration, which can reduce the thermal and pressure input requirements to produce the same molding; higher productivity may also be achieved. In this paper, a design of an ultrasound–assisted injection mold machine is explored. An extrusion-die design was augmented with a commercial 1.5kW ultrasonic transducer and sonotrode designed to resonate close to 20kHz with up to 100μm vibration amplitude. The design was evaluated with modal and thermal analysis using finite-element analysis software. The use of numerical techniques, including computational fluid dynamics, fluid-structure interaction and coupled Lagrangian-Eulerian method, to predict the effect of ultrasound on polymer flow was considered. A sonotrode design utilizing ceramic to enhance thermal isolation was also explored.

To Plot Graph and Establish Relationship Between Component Weight and Wall Thickness for a Component Manufacturing in Gas Assist Injection Moulding

To check the Quality of Gas Assist Molded Part very difficult, because it depends on its Gas Channel Geometry and uniform wall thickness. These can be check only after cross section cut and those parts will be rejected, so we have to find one more factor which can be validate process and insure quality with easy method. In GAIM, Part weight is very important criteria and now we need to established relation with part wall thickness. The GAIM study, trials, result, analysis and our experiment provides part weight have proportional related with part wall thickness.

Supercritical assisted injection in a liquid antisolvent for PLGA and PLA microparticle production

Biodegradable and biocompatible polymers PLA (poly lactic acid) and PLGA (poly lactic-co-glycolic acid) have been processed using supercritical assisted injection in a liquid antisolvent (SAILA), to evaluate the possibility to produce microparticles of controlled size and distribution. SAILA experiments were performed varying the process parameters, studying the influence of temperature, gas to liquid ratio (GLR) and polymer concentration on particle size distribution. Spherical, smooth and not coalescing particles were obtained at all process conditions; sub-microparticles (0.46±0.17μm) and microparticles (2.1±0.84μm) of PLA and PLGA have been produced with a fairly good control of particle size distribution.Preliminary encapsulation tests have also been performed, using Piroxicam as a model drug. An encapsulation efficiency of about 60% has been obtained. Coprecipitated drug/polymer microparticles allowed a controlled release of the drug for about 5days.

Exploring the role of an unsanctioned, supervised peer driven injection facility in reducing HIV and hepatitis C infections in people that require assistance during injection

BackgroundSupervised consumption rooms or supervised injection facilities (SIFs) are venues that have reduced the risk of needle sharing and deaths caused by drug overdose among people who inject drugs (PWID). As a result of such a decline in the mortality rate, numerous studies have been able to illustrate its cost-effectiveness. However, studies have neglected to examine the same phenomena for unsanctioned SIFs that are run by peer drug users and provide assisted injections.MethodsThe current study will determine whether the former unsanctioned SIF, that provided assisted injection and was operated by the grass root organization called Vancouver Area Network of Drug Users (VANDU), cost less than the health care consequences of not having such a program in Vancouver, Canada. By analyzing data gathered in 2013, this paper relies on two mathematical models to estimate the number of new HIV and HCV infections prevented by the former unsanctioned facility in Vancouver’s Downtown Eastside.ResultsA conservative estimate indicates that the SIF location that provided assisted injections has a benefit-cost ratio of 33.1:1 due to its low operational cost. At the baseline sharing rate, the facility, on an average, reduced 81 HCV and 30 HIV cases among PWID each year. Such reductions in blood borne infections among PWID resulted in annual savings worth CAN$4.3 million dollars in health care expenditure. In addition to this, the current paper relies on a sensitivity analysis based on different needle sharing rate scenarios.ConclusionsThe sensitivity analysis and the baseline rates indicate that funding SIF facilities operated by peer drug users that facilitate assisted injection appear to be an efficient and effective use of financial resources in the public health domain since they lead to a significant decline in the rate of mortality within a vulnerable population.

Application of ultrasonic-assisted injection molding for improving melt flowing and floating fibers

Abstract In this study, we investigated the use of ultrasonic technology in assisted injection molding and mold designs. We used an ultrasonic device installed in a mold to vibrate a melt directly, thereby converting kinetic energy into thermal energy. In addition, we developed three flat specimens of different thicknesses (3, 1, and 3-1-3 mm) produced by ultrasonic-assisted injection molds. An ultrasonic oscillation device 45 mm in diameter was placed in the cavity and used to vibrate a polycarbonate or a polycarbonate with 30% glass fiber melt at a frequency of 20 kHz. Furthermore, cavity pressure sensors were positioned at the front and rear of the vibration region for analyzing the melt flow behavior under ultrasonic-assisted injection molding conditions. Because of the absorption of ultrasonic energy, local heat was generated inside the resin, thus forming an oscillatory flow during the packing and holding stages, improving the flow characteristics of the melt, and changing the melt flow behavior around the skin layer to reduce the molecular orientation and high shear effect. The freezing rate of the melt was also reduced to eliminate the glass fiber streaks, floating fibers, and fiber orientation, particularly for thinner parts; the hesitation phenomena were then improved to increase the weld line strength.

High Prevalence of Assisted Injection Among Street-Involved Youth in a Canadian Setting.

Many people who inject illicit drugs receive manual assistance when injecting, and this practice has been linked to increased risk of HIV infection and other harms. Little is known, however, about this practice among youth. This study uses a multivariate generalized estimating equation to identify factors associated with receiving assistance with injecting among a cohort of street-involved youth aged 14-26 in Vancouver, Canada. A total of 253 participants reported injecting drugs during the study period, and 49 % (n = 125) of these youth reported receiving assistance with injecting in the past 6 months. In multivariate analysis, younger age, female gender, binge drug use, heroin injecting, cocaine injecting, crystal methamphetamine injecting, and syringe sharing were positively and independently associated with assisted injection (all p < 0.05). These findings underscore the need for expanding substance abuse treatment alongside HIV prevention and health promotion interventions to empower youth to enact safer injection practices.

Graphene coating assisted injection molding of ultra‐thin thermoplastics

High strength light weight parts are critical for the development of new technologies, particularly electronic devices, such as laptop computers, smart phones, and tablet devices. Injection molded plastics and composites are excellent choices for mass producing such parts. As the part thickness decreases from traditional injection molding (&gt;2 mm thickness) to thin wall molding (∼1 mm thickness), and lastly, to ultra‐thin wall molding (&lt;0.5 mm thickness), avoiding incomplete filling (short shots) becomes more challenging. Even though, methods exist today for molding thin‐wall plastic parts (i.e., fast heating/fast cooling injection molding), they require multiple steps resulting in a noncost efficient process. In this article, we demonstrate the technical feasibility of using graphene coating to facilitate flow, by promoting slip at the mold walls. We evaluate the influence of coated and uncoated mold inserts on fiber orientation. We present experimental results using un‐reinforced polypropylene and a 40% by weight carbon fiber reinforced polycarbonate/acrylonitrile butadiene styrene. POLYM. ENG. SCI., 55:1374–1381, 2015. © 2015 Society of Plastics Engineers

Large scale formation of various highly oriented structures in polyethylene/polycarbonate microfibril blends subjected to secondary melt flow

A strong shear flow was imposed on the melt of polycarbonate (PC) microfibril reinforced high density Polyethylene (HDPE) during a secondary melt flow process, i.e. gas assisted injection molding (GAIM). Classic shish-kebabs and typical transcrystallinity were simultaneously observed in the entire thickness of the GAIM HDPE/PC microfibril composites, which were closely related to the strong shear flow that was further amplified and distributed by incorporated PC microfibrils. Interestingly, some nano-sized ultrafine PC microfibril inclined to absorb extended chain bundles to form shish nuclei on its surface first, which subsequently evolved into hybrid shish-kebab superstructures. It was deemed that the induced formation of hybrid shish-kebab superstructures on nano-sized ultrafine PC microfibril was due to the absorbing of extended chain bundles for hybrid shish nuclei with the strong shear flow serving as the driving force. Importantly, large scale formation of these highly oriented crystalline superstructures can bring significant mechanical reinforcement in GAIM HDPE/PC microfibril composite. For GAIM HDPE/PC microfibril composites, its yield strength is increased by 68% and 66%, compared to the GAIM HDPE parts and the common injection molded (CIM) HDPE/PC composites, respectively; meanwhile, the Young's modulus is enhanced by 253% and 17%, compared to the GAIM HDPE parts and the CIM HDPE/PC composites, respectively.

Optimization study of third harmonic generation in quantum cascade lasers.

A systematic optimization study of quantum cascade lasers with integrated nonlinearity for third-harmonic generation is performed. To model current transport the Pauli master equation is solved using a Monte Carlo approach. A multi-objective particle swarm optimization algorithm is applied to obtain the Pareto front. Our theoretical analysis indicates an optimized structure with five orders of magnitude increase in the generated third-harmonic power with respect to the reference design. This striking performance comes with a low threshold current density of about 1.6 kA/cm2 and is attributed to double resonant phonon scattering assisted extraction and injection scheme of the laser.