Is constant needle motion during soft tissue filler injections a safer procedure?:A theoretical mathematical model for evaluating patient safety

BackgroundThe safety rationale behind the constant needle motion injection technique is based on the assumption that due to the constant needle motion and simultaneous soft tissue filler material administration a smaller amount of product per area may be injected into an artery if an artery within the range of the moving needle is inadvertently entered.ObjectiveTo perform mathematical calculations for determining the probability for causing intra-arterial product administration when constantly moving the needle during facial aesthetic soft tissue filler injections.MethodsThis study was designed as a theoretical investigation into the probabilities for causing adverse events due to intravascular injection of soft tissue filler material when constantly moving a 27-G needle during facial soft tissue filler administration.ResultsIt was revealed that with a higher number of conducted injection passes a greater soft tissue area can be covered by the needle. The odds of encountering an artery within the covered soft tissue volume and the odds of injecting any volume greater than zero into the arterial blood stream increases with the number of performed injection passes. This increase is greatest between 1 and 10 performed injection passes.ConclusionThis model demonstrates that the constant needle motion technique increases the probability of encountering an artery within the treatment area and thus increases the odds for intra-arterial product administration. The constant needle motion technique does not increase safety but rather may increase the odds of causing intra-arterial product administration with the respective adverse consequences for the patient

Reverse dark current in organic photodetectors and the major role of traps as source of noise

Organic photodetectors have promising applications in low-cost imaging, health monitoring and near-infrared sensing. Recent research on organic photodetectors based on donor–acceptor systems has resulted in narrow-band, flexible and biocompatible devices, of which the best reach external photovoltaic quantum efficiencies approaching 100%. However, the high noise spectral density of these devices limits their specific detectivity to around 1013 Jones in the visible and several orders of magnitude lower in the near-infrared, severely reducing performance. Here, we show that the shot noise, proportional to the dark current, dominates the noise spectral density, demanding a comprehensive understanding of the dark current. We demonstrate that, in addition to the intrinsic saturation current generated via charge-transfer states, dark current contains a major contribution from trap-assisted generated charges and decreases systematically with decreasing concentration of traps. By modeling the dark current of several donor–acceptor systems, we reveal the interplay between traps and charge-transfer states as source of dark current and show that traps dominate the generation processes, thus being the main limiting factor of organic photodetectors detectivity

Field Effect versus Driving Force: Charge Generation in Small-Molecule Organic Solar Cells

Efficient charge generation in organic semiconductors usually requires an interface with an energetic gradient between an electron donor and an electron acceptor in order to dissociate the photogenerated excitons. However, single-component organic solar cells based on chloroboron subnaphthalocyanine (SubNc) have been reported to provide considerable photocurrents despite the absence of an energy gradient at the interface with an acceptor. In this work, it is shown that this is not due to direct free carrier generation upon illumination of SubNc, but due to a field-assisted exciton dissociation mechanism specific to the device configuration. Subsequently, the implications of this effect in bilayer organic solar cells with SubNc as the donor are demonstrated, showing that the external and internal quantum efficiencies in such cells are independent of the donor-acceptor interface energetics. This previously unexplored mechanism results in efficient photocurrent generation even though the driving force is minimized and the open-circuit voltage is maximized

Orientation dependent molecular electrostatics drives efficient charge generation in homojunction organic solar cells

Organic solar cells usually utilise a heterojunction between electron-donating (D) and electron-accepting (A) materials to split excitons into charges. However, the use of D-A blends intrinsically limits the photovoltage and introduces morphological instability. Here, we demonstrate that polycrystalline films of chemically identical molecules offer a promising alternative and show that photoexcitation of α-sexithiophene (α-6T) films results in efficient charge generation. This leads to α-6T based homojunction organic solar cells with an external quantum efficiency reaching up to 44% and an open-circuit voltage of 1.61 V. Morphological, photoemission, and modelling studies show that boundaries between α-6T crystalline domains with different orientations generate an electrostatic landscape with an interfacial energy offset of 0.4 eV, which promotes the formation of hybridised exciton/charge-transfer states at the interface, dissociating efficiently into free charges. Our findings open new avenues for organic solar cell design where material energetics are tuned through molecular electrostatic engineering and mesoscale structural control

Evaluation of Cannula Safety in Injection of Poly-L-Lactic Acid

Andreas Nikolis,1,2 Luiz E Avelar,3,4 Kaitlyn M Enright2 1Division of Plastic Surgery, McGill University Health Center, Montreal, QC, Canada; 2Erevna Innovations Clinical Research Unit, Montreal, QC, Canada; 3Department of Forensic Anthropology, Civil Police Department, Minas Gerais, Brazil; 4Private Practice, Belo Horizonte, BrazilCorrespondence: Andreas NikolisErevna Innovations Clinical Research Unit, Montreal, QC, CanadaEmail [email protected] and Objective: Poly-L-lactic acid (PLLA) has been used in various medical applications for decades, including aesthetic ones. The use of a cannula technique in injecting PLLA has been proposed in order to lower the incidence rate of adverse events (AEs) following treatment. Such AEs include nodule formation, which may occur less frequently by fanning the product with a cannula, thus creating a more uniform product placement compared to that resulting from the use of a needle. Currently, however, there is a lack of comparative research regarding the safety of cannulas versus needles for PLLA injections, as the selection of either remains highly subjective. Therefore, the objective of our study was to investigate the safety of cannula use in the administration of PLLA, in order to report safety outcomes.Materials and Methods: A single-center, retrospective chart review was conducted to examine the data of patients who had previously undergone treatment with PLLA in the form of Sculptra® Aesthetic™ in the face and/or neck regions. Twenty-seven subject charts met eligibility. Descriptive data regarding treatment and follow-up visits were collected and analyzed.Results: A total of seven AEs resulted from eighty-two treatment sessions (8.54%), with 6/27 patients having experienced at least one AE (22.22%). Mild bruising was the most commonly reported AE (57.14%). The majority of the AEs were mild and transient in nature, with one moderate AE being a nodule that was possibly related to a concomitant treatment. All AEs were resolved with follow-up care.Conclusion: Mild AEs such as bruising, swelling and pain should be expected following the use of a cannula for PLLA injections. However, the incidence rates of AEs following treatment can remain low if proper product preparation and treatment techniques are utilized.Keywords: poly-L-lactic acid, adverse events, cannula, injection techniques, antiagin