Sequential process optimization for a digital light processing system to minimize trial and error.

In additive manufacturing, logical and efficient workflow optimization enables successful production and reduces cost and time. These attempts are essential for preventing fabrication problems from various causes. However, quantitative analysis and integrated management studies of fabrication issues using a digital light processing (DLP) system are insufficient. Therefore, an efficient optimization method is required to apply several materials and extend the application of the DLP system. This study proposes a sequential process optimization (SPO) to manage the initial adhesion, recoating, and exposure energy. The photopolymerization characteristics and viscosity of the photocurable resin were quantitatively analyzed through process conditions such as build plate speed, layer thickness, and exposure time. The ability of the proposed SPO was confirmed by fabricating an evaluation model using a biocompatible resin. Furthermore, the biocompatibility of the developed resin was verified through experiments. The existing DLP process requires several trials and errors in process optimization. Therefore, the fabrication results are different depending on the operator's know-how. The use of the proposed SPO enables a systematic approach for optimizing the process conditions of a DLP system. As a result, the DLP system is expected to be more utilized.

Optimization of the Projection Microstereolithography Process for a Photocurable Biomass-Based Resin.

Biomass materials, an important source of chemical feedstocks, could replace fossil fuels as a resource in the future. The chemical feedstocks from biomass materials are used in many medical and pharmaceutical products and in fuels, chemicals, and functional materials. Biomass materials are expected to be used in biomedical engineering fields, especially due to their low biotoxicity. By the way, most of the demand for bio-application fields is an application targeted for customized production, so a high formability is required for production. Research on three-dimensional (3D) printing technology capable of satisfying these requirements has been ongoing. Manufacturing additives need to be investigated to use biomass materials as a resin or bioink safely for 3D printing, which is a technique widely used in biomedical engineering fields. In this study, a projection microstereolithography (PµSL) system, a 3D printing technique, was made that uses a biomass-based resin. Biomass materials are designed to be photocurable for use in the PµSL process. Various PµSL process parameters were investigated using the biomass-based resin to determine the optimum fabrication conditions for 3D structures. This study demonstrated that a biomass-based resin can be used in the PµSL process. We provide a method for its application in various biomedical engineering fields.

Preparation of Flexible Electrodes Based on Silver Nanoparticles-Carbon Nanotubes (AgNPs-CNTs) and Elastomer Composites for Soft Electronics.

For flexible electronics devices, a composite of silver nanoparticles-carbon nanotubes (AgNPs-CNTs) and polydimethylsiloxane elastomer were well mixed using a planetary mixer and a 3-roll mill. The ratio of Ag/polymer was varied by adding different size of AgNPs and modified with 12 kinds of flexible electrode compositions. The electrical and mechanical stability of the electrode was measured by combining universal test machine and cyclic voltammetry at once and it showed remarkable stability during 200% strain and 100 cycle duration test. The stable and repeatable electrical circuit was demonstrated while bending and stretching the electrode even higher than 120% strain. Furthermore, the soft gripper incorporating a flexible electrode was fabricated to lift a thin target paper based on electroadhesive force.

Retrospective analysis of risk factors of hypotensive bradycardic events during shoulder arthroscopic surgery under interscalene blockade in the sitting position.

BACKGROUND: Hypotensive bradycardic events (HBEs) are a frequent adverse event in patients who underwent shoulder arthroscopic surgery under interscalene block (ISB) in the sitting position. This retrospective study was conducted to investigate the independent risk factors of HBEs in shoulder arthroscopic surgery under ISB in the sitting position. METHODS: A total of 2,549 patients who underwent shoulder arthroscopic surgery under ISB and had complete clinical data were included in the study. The 357 patients who developed HBEs were included in the HBEs group, and the remaining 2,192 in the non-HBEs group. The potential risk factors for HBEs, such as age, sex, past medical history, anesthetic characteristics, and intraoperative medications were collected and compared between the groups. Statistically significant variables were included in a logistic regression model to further evaluate the independent risk factors for HBEs in shoulder arthroscopic surgery under ISB. RESULTS: The incidence of HBEs was 14.0% (357/2549). Logistic regression analysis revealed that the intraoperative use of hydralazine (odds ratio [OR] 4.2, 95% CI 2.9-6.3), propofol (OR 2.1, 95% CI 1.3-3.6), and dexmedetomidine (OR 3.9, 95% CI 1.9-7.8) before HBEs were independent risk factors for HBEs in patients who received shoulder arthroscopic surgery under ISB. CONCLUSIONS: The intraoperative use of antihypertensives such as hydralazine and sedatives such as propofol or dexmedetomidine leads to increased risk of HBEs during shoulder arthroscopic surgery under ISB in the sitting position.

Synthesis of BaTiO3 nanoparticles as shape modified filler for high dielectric constant ceramic-polymer composite.

Coral-like structured barium titanate (BaTiO3) nanoparticles were synthesized as filler for a high dielectric elastomer. The nanoparticle size, and shape, and the reactivity of the synthesis were modified according to temperature, time, pH, and precursor materials. Dielectric properties of poly(dimethylsiloxane) (PDMS) composites were estimated by volume fractions of BaTiO3 of 5, 10, and 15 vol% for both sphere and coral-like shapes. As a result, coral-like BaTiO3-PDMS composites had the highest dielectric constant of 10.97, which was 64% higher than the spherical BaTiO3-PDMS composites for the 15 vol% fraction. Furthermore, the phase transition process and surface modification were applied to increase the dielectric properties through calcination and improved particle dispersion in the elastomer using polyvinylpyrrolidone (PVP). The dispersion of the PVP coated BaTiO3-PDMS composite was improved compared to pristine BaTiO3 as shown by SEM imaging. The coral-like BaTiO3 embedded composite could be used for electronic devices such as piezoelectric devices or electro-adhesive grippers, which require flexible and high dielectric materials.

Cardiac arrest in a patient with anterior fascicular block after administration of dexmedetomidine with spinal anesthesia: A case report.

BACKGROUND: Dexmedetomidine is a sedative and analgesic agent that is administered intravenously as an adjunct to spinal anesthesia. It does not suppress the respiratory system significantly, but has adverse effects on the cardiovascular system, for example, bradycardia and hypotension. We here report a patient who underwent cardiac arrest during spinal anesthesia after intravenous infusion of dexmedetomidine. METHODS: A 57-year-old woman with no significant medical history underwent spinal anesthesia for arthroscopic meniscus resection after rupturing the right knee meniscus. Preoperative electrocardiogram revealed sinus bradycardia (54 beats/min) and a left anterior fascicular block. Spinal anesthesia was performed with 11 mg of 0.5% heavy bupivacaine, and the upper level of sensory loss was at T6. Dexmedetomidine infusion was planned at a loading dose of 1.0 mcg kg min over 10 minutes, followed by 0.7 mcg kg min intravenously, as a sedative. Two minutes after dexmedetomidine injection, her heart rate decreased to 31 beats/min and asystole was observed within 10 seconds. RESULTS: After a few minutes of cardiopulmonary resuscitation, spontaneous circulation returned and surgery was completed under general anesthesia. The patient was discharged, and experienced no complications. CONCLUSION: Dexmedetomidine can decrease blood pressure and heart rate, and may cause asystole in some cases. We suggest that dexmedetomidine should be carefully administered under close observation when the parasympathetic nerve system is activated during spinal anesthesia.

Use of the GlideScope video laryngoscope for intubation during ex utero intrapartum treatment in a fetus with a giant cyst of the 4th branchial cleft: A case report.

INTRODUCTION: In fetuses who are predicted to be at risk of catastrophic airway obstruction at delivery, the ex utero intrapartum treatment (EXIT) procedure is useful for securing the fetal airway while maintaining fetal oxygenation via placental circulation. Factors, including poor posture of the fetus and physician, narrow visual field, and issues of contamination in the aseptic surgical field, make fetal intubation during the EXIT procedure difficult. Herein, we report our experience of the usefulness of the GlideScope video laryngoscope (GVL) for intubation during the EXIT procedure. SYMPTOMS AND CLINICAL FINDINGS: A 28-year-old woman presented with a fetus having a cystic neck mass diagnosed on prenatal ultrasound at 25 weeks of gestation. We planned the EXIT procedure in conjunction with cesarean delivery at 38 weeks of gestation, as the mass enlarged to 4.9 cm × 3.2 cm, protruded externally at the neck, and subsequently resulted in polyhydramnios. THERAPEUTIC INTERVENTION AND OUTCOMES: After induction of anesthesia using intravenous thiopental (300 mg), adequate uterine relaxation was achieved with sevoflurane (2.0-3.0 vol%) combined with continuous intravenous infusion of nitroglycerin (0.5-1.0 µg/kg/min) for maintaining uteroplacental circulation. After hysterotomy, the head and right upper limb of the fetus were partially delivered, and fetal heart tones were monitored with a sterile Doppler probe. After oropharyngeal suctioning to improve the visual field, the fetus was intubated successfully using a sterile GVL by an anesthesiologist, and the passage of the endotracheal tube beyond the vocal cords was confirmed on the screen of the GVL system. Immediately after the fetal airway was definitely secured, the fetus was fully delivered with umbilical cord clamping. After delivery, nitroglycerine administration was ceased and sevoflurane administration was reduced to 0.5 minimum alveolar concentration. Additionally, oxytocin (10 units) and carbetocin (100 µg) were administered for recovery of uterine contraction. Cesarean delivery was successfully performed without any problems, and the neonate successfully underwent surgery for removal of the neck mass under general anesthesia on the 7th day after delivery. The neonate is developing normally. CONCLUSION: The GVL approach may be a useful noninvasive approach for establishing a clear fetal airway during the EXIT procedure.

Comparison of a tube-holder (Rescuefix) versus tape-tying for minimizing double-lumen tube displacement during lateral positioning in thoracic surgery: A prospective, randomized controlled study.

BACKGROUND: Double-lumen endotracheal tubes (DLTs) are often displaced during change from the supine to the lateral decubitus position. The aim of this study was to determine whether Rescuefix, a recently developed tube-holder device, is more effective than the traditional tape-tying method for tube security during lateral positioning. METHODS: Patients were randomly assigned to a Rescuefix (R) group (n = 22) or a tape (T) group (n = 22). After intubation with a left-sided DLT and adjustment of the appropriate DLT position using a fiberoptic bronchoscope, the DLT was fixed firmly at the side of the mouth by either Rescuefix or Durapore tape. "Tracheal depth" (from the tracheal carina to the elbow connector of the DLT) and "bronchial depth" (from the left bronchial carina to the elbow connector of the DLT) were measured in the supine position using the fiberoptic bronchoscope. After positional change, tracheal and bronchial depths were measured as described above. As the primary endpoint, displacement of the DLT during positional change was evaluated by obtaining the difference in depths measured when the patient was in the supine and lateral decubitus positions. In addition, after lateral positioning of the patient, any requirement for repositioning the DLT was recorded. RESULTS: After lateral positioning, there were no significant differences in changes in tracheal and bronchial depths between the groups (tracheal depth 6.1 ±â€Š4.4 mm [R group] and 9.1 ±â€Š5.6 mm [T group], P = 0.058; bronchial depth 6.5 ±â€Š4.4 mm [R group], and 8.5 ±â€Š4.6 mm [T group], P = 0.132). Although the amount of change in tracheal and bronchial depths was not different between the groups, the need to reposition the DLT was significantly lower in the R group than in the T group (32% vs 68%, P = 0.016). CONCLUSION: This study demonstrated that use of Rescuefix did not reduce the amount of DLT displacement, but it did significantly lower the incidence of DLT repositioning compared with the tape-tying method. Therefore, Rescuefix appears to be an effective alternative to minimizing DLT displacement during lateral positioning in thoracic surgery. TRIAL REGISTRATION: http://cris.nih.go.kr identifier: KCT0001949.

Hypoxia in a transient estuary caused by summer lake-water discharge from artificial dykes into Chunsu Bay, Korea.

We investigated bottom-water hypoxia induced by freshwater discharge from two artificial dykes into Chunsu Bay (CSB), Korea, during the summer of 2010. Field observations and model results of the dynamic and water-quality parameters indicated that the triggering mechanism of the hypoxia was strong stratification formed by the freshwater discharge from both dykes, which limited the dissolved oxygen (DO) supply in bottom water. Beneath the pycnocline, DO was consumed by sediment oxygen demand (SOD) during the summer. To investigate these processes, model experiments were conducted using a simplified DO budget model coupled with a 3D hydrodynamic model. The DO concentration in the northern part of CSB reached hypoxic conditions very quickly after 3.4days of discharge and lasted 18days until normal conditions resumed. In sum, in the CSB, marked stratification and its maintenance played a critical role in hypoxia in bottom water.

Predicting the difficulty in performing a neuraxial blockade.

BACKGROUND: Traumatic placement of a needle during a neuraxial blockade has been related to many complications such as postdural puncture headache, trauma to neural structures and even spinal hematoma, causing permanent neurologic deficits. Although efforts to minimize the complications caused by traumatic neuraxial blockade have been made, nothing was found to be clear. The authors investigated the predictors of difficult neuraxial blockade using the first puncture success and number of attempts as measures to assess the difficulty. METHODS: In this prospective observational study, 253 patients scheduled for elective surgery underwent spinal or epidural anesthesia. Patient data (age, sex, height, weight, body mass index, and quality of anatomical landmarks), the provider's level of experience, type of blockade (spinal or epidural), needle type/gauge and the distance from skin to subarachnoid or epidural space were recorded. Significant variables were first determined by Student's t-test and Pearson's chi square test and then logistic and Poisson regression tested the association of the first puncture success and number of attempts with the significant variables. RESULTS: The provider's level of experience and the distance from skin to subarachnoid or epidural space were significant in logistic and Poisson regression. Body mass index was significant only in Poisson regression and the quality of anatomical landmarks was significant only in logistic regression. CONCLUSIONS: Provider's level of experience and the distance from skin to subarachnoid or epidural space influenced the difficulty in performing a neuraxial blockade.