Investigation of Plasma Electrolytic Oxidation of Commercially Pure Magnesium For Biomedical Applications

Permanently implanted biomaterials may cause problems to the host body associated with long term chronic inflammation which would eventually require revision surgery. The development of biodegradable materials which can be absorbed, consumed and excreted by the patient is therefore of interest. Magnesium alloys have for a long time been considered as potential biomaterials for load-bearing applications due to their excellent biological properties including superior biochemical and biomechanical compatibility compared to other alternatives such as biodegradable polymers and bioceramics. However, the application of magnesium material in the biological area is still limited due to its intrinsically poor corrosion performance in the biological environments. Therefore, various methods have been explored to control the degradation rate of magnesium in biological fluid, of which plasma electrolytic oxidation (PEO) is the most promising method. PEO is a plasma-assisted anodising process that can convert the surface of magnesium into a ceramic layer, thus preventing the corrosive medium contacting the substrate; therefore, the degradation rate can be reduced. Furthermore, highly biocompatible coatings can be produced when appropriate electrolytes are used in the PEO process. Motivated by the beneficial properties of magnesium and corrosion protection provided by the PEO technique, considerable efforts have been devoted towards the development of magnesium implants based on PEO protection. Nevertheless, the corrosion rate of magnesium has not been reduced to an acceptable level and a universal PEO process appropriate for magnesium has not yet been established. In the present study, PEO processes on commercially pure (cp) magnesium and the resulting coating characteristics have been systematically studied. Through this progressive study, a biologically friendly electrolyte containing Ca and P compounds have been developed. An appropriate current regime for this electrolyte has also been studied. Finally, a hydroxyapatite layer, intended to enhance the sample bioactivity, was deposited on the PEO coated cp magnesium. The PEO process was studied according to key electrical characteristics including voltage transient, and voltage/current waveforms. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) were employed to study the surface and cross-sectional morphology, elemental composition, phase composition of the coatings. Residual stress induced by the PEO process is also studied using XRD method. The corrosion properties of the coated samples in simulated body fluid (SBF) were studied using electrochemical methods including open circuit potential (OCP) monitoring, electrochemical impedance spectroscopy (EIS) measurement, and potentiodynamic polarisation scans. The mechanical properties, including static tensile properties and cyclic fatigue performance of the coated samples were also studied to verify the applicability of magnesium in biological areas from the mechanical point of view. The results indicated that the combination of a pulsed unipolar (PUP) current regime of 3000 Hz and an electrolyte composed of 12 g/l Na3PO4•12H2O and 2g/l Ca(OH)2 provides the best process stability and success of Ca and P incorporation. Moreover, the corrosion resistance of cp magnesium in the SBF could be improved by more than 10 times. Nevertheless, such protection is very limited as the coating was degraded rapidly in the simulated body fluid, which is due to the chemical instability of MgO at the pH of SBF. Tensile and cyclic fatigue tests demonstrated that the PEO coated cp magnesium possesses sufficient mechanical properties for general load-bearing biomedical applications even though the fatigue strength is significantly deteriorated by the surface modification. Further work required to achieve better control over the biodegradation process of Mg implants can be outlined as follows: (i) robustness of the developed PEO process should be explored on other corrosion resistant magnesium alloys containing biologically friendly elements (like Ca, Zn, Mn); (ii) addition of F-, SiO32- in the electrolyte to facilitate the formation of stable compounds besides MgO in the PEO coating, thus reducing the degradation rate of magnesium based implant

High-performance cVEP-BCI under minimal calibration

The ultimate goal of brain-computer interfaces (BCIs) based on visual modulation paradigms is to achieve high-speed performance without the burden of extensive calibration. Code-modulated visual evoked potential-based BCIs (cVEP-BCIs) modulated by broadband white noise (WN) offer various advantages, including increased communication speed, expanded encoding target capabilities, and enhanced coding flexibility. However, the complexity of the spatial-temporal patterns under broadband stimuli necessitates extensive calibration for effective target identification in cVEP-BCIs. Consequently, the information transfer rate (ITR) of cVEP-BCI under limited calibration usually stays around 100 bits per minute (bpm), significantly lagging behind state-of-the-art steady-state visual evoked potential-based BCIs (SSVEP-BCIs), which achieve rates above 200 bpm. To enhance the performance of cVEP-BCIs with minimal calibration, we devised an efficient calibration stage involving a brief single-target flickering, lasting less than a minute, to extract generalizable spatial-temporal patterns. Leveraging the calibration data, we developed two complementary methods to construct cVEP temporal patterns: the linear modeling method based on the stimulus sequence and the transfer learning techniques using cross-subject data. As a result, we achieved the highest ITR of 250 bpm under a minute of calibration, which has been shown to be comparable to the state-of-the-art SSVEP paradigms. In summary, our work significantly improved the cVEP performance under few-shot learning, which is expected to expand the practicality and usability of cVEP-BCIs.Comment: 35 pages, 5 figure

A randomized controlled trial evaluating the effects of transversus abdominis plane block with compound lidocaine hydrochloride injection on postoperative pain and opioid consumption and gastrointestinal motility in patients undergoing gynecological laparotomy

IntroductionIncorporation of transversus abdominis plane (TAP) block into multimodal analgesia has been emphasized in Enhanced Recovery protocols (ERPs). However, benefit is limited in clinical practice. A potential explanation is the short duration of analgesia of standard local anesthetics. Herein, this randomized, double-blind, controlled trial evaluated whether TAPB with long-acting compound lidocaine hydrochloride injection reduces postoperative pain.Methods164 patients undergoing elective gynecological laparotomy under sevoflurane anesthesia randomly received ultrasound-guided TAP block with either saline, or ropivacaine, or compound lidocaine before anesthesia induction. The postoperative pain intensity (primary outcome) was evaluated by pain 11-point numerical rating scale. We also recorded sufentanil consumptions, time to first flatus, side-effects and hospital stay after surgery.ResultsWe reported that pain scores at rest at postoperative 3h in group 0.375% ropivacaine was lower than that in group saline [mean 2.4 (SD 1.2) vs. 3.0 (1.0), p = 0.036]. Compared with saline, 0.4% and 0.6% compound lidocaine caused lower pain scores at rest at postoperative 12h [2.8 (0.9) vs. 2.1 (0.9) and 2.0 (0.9), p = 0.016 and p = 0.006]. Sufentanil usage for the first postoperative 48h was lower in group 0.6% compound lidocaine than group saline [24.2 (5.4) vs. 45.6 (7.5) µg, p  < 0.001]. Time to first flatus and hospital stay after surgery was shortest and the incidence of postoperative nausea was lowest in patients receiving 0.6% compound lidocaine.ConclusionTAP block with 0.6% compound lidocaine hydrochloride injection attenuates postoperative pain, reduces opioid consumption, accelerates gastrointestinal function recovery, and shortens length of hospital stay in patients after gynecological laparotomy.Trial registrationClinicalTrials.gov, identifier: NCT04938882

Argon-helium knife cryoablation plus programmed cell death protein 1 inhibitor in the treatment of advanced soft tissue sarcomas: there is no evidence of the synergistic effects of this combination therapy

BackgroundEffective treatment for advanced soft tissue sarcomas (STSs) is necessary for improved outcomes. Previous studies have suggested that cryoablation can have a synergistic effect with programmed cell death protein-1 (PD-1) inhibitor in the treatment of malignancy. This study aimed to clarify the efficacy and safety of argon-helium knife cryoablation in combination with PD-1 inhibitor in the treatment of STSs.MethodsRetrospectively collected and analyzed the clinical data of patients with advanced STS who underwent cryoablation and PD-1 inhibitor between March 2018 and December 2021.ResultsThis study included 27 patients with advanced STS. In terms of target lesions treated with cryoablation, 1 patient achieved complete response, 15 patients had partial response (PR), 10 patients had stable disease, and 1 patient had progressive disease. This corresponded to an overall response rate of 59.3% and a disease control rate of 96.3%. In terms of distant target lesions untreated with cryoablation, only two patients had a PR compared to the diameter of the lesion before ablation. The combination therapy was relatively well tolerated. None of the patients experienced treatment-related death or delayed treatment due to adverse events.ConclusionCryoablation combined with PD-1 inhibitors in the therapy of advanced STS is safe and can effectively shrink the cryoablation-target lesion. However, there is no evidence of the synergistic effects of this combination therapy

Estimation of mechanics parameters of rock in consideration of confining pressure using monitoring while drilling data

During the drilling process, high-strength rock can lead to various issues such as drilling suppression, bit wear, and increased operational costs. To ensure safe and efficient drilling operations, it is crucial to accurately predict the strength parameters of the rock and recommend modifications to operational procedures. This paper proposes a low-cost and fast measurement method for predicting the strength parameters of rock in the field. To evaluate the effectiveness of this method, a drilling process monitoring experiment was conducted on sandstone, limestone, and granite. The experiment studied the effect of confining pressure on the response of cutting with an impregnated diamond bit. By analyzing the relationship between the thrust force, torque force, and penetration depth under different confining pressures, the researchers developed an analytical model for drilling that considers confining pressure, compressed crushed zone, and bit geometry. The results show that the confining pressure has a significant effect on the cutting response. As the confining pressure increases, the thrust force, torque force, and penetration depth at the cutting point also increase. Furthermore, a new measurement method was proposed to determine the strength parameters, such as cohesion, internal friction angle, and unconfined compressive strength. The estimated strength parameters for the three rock types using the drilling method were in good agreement with those of the standard laboratory test, with an error range of 10%. This method of estimating rock strength parameters is a practical tool for engineers. It can continuously and quickly obtain the drilling parameters of in-situ rocks