• Journal of Biomedical Engineering Research
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• v.42 no.6
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• pp.251-258
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• 2021

Hyaluronic acid (HA) microspheres (MSs) crosslinked with polyethylene glycol diglycidyl ether (PEGDE) are prepared using a simple fluidic device (SFD) to investigate the optimized parameters. A solution mixture of PEGDE in 2-methyl-1-propanol was prepared as a continuous phase in SFD. HA solutions of 1 wt% concentration were introduced into SFD as a discontinuous phase. The HA solution prepared by stirring for more than 48 h exhibited spherical MSs at the needle tip inside the ring cap. As the flow rate of the continuous phase increased from 0.7 to 1.9 mL/min, the diameter of the MS decreased from 173±36 ㎛ to 129±13 ㎛. Although the PEGDE concentration in the range of 0.2 to 1.8 vol% did not affect the diameter of the MS, the microstructure of MS, consisting of inner hollow void and wall, was changed. The inner void and wall size decreased and increased from 79.5 ㎛ to 57.2 ㎛ and from 10.3 ㎛ to 21.4 ㎛, respectively, with increasing PEGDE concentration from 0.2 vol% to 1.8 vol%. FT-IR peaks located around 2867 cm^-1 and 1088 cm^-1 indicated that the HA MS prepared at different PEGDE concentrations were chemically crosslinked. The HA MSs containing different PEGDE concentrations exhibited quantitative cell viability of more than 98%. L-929 cells adhered well to the HA MSs and proliferated continuously with increasing culture time to 48 h regardless of PEGDE concentration, implying that the HA MSs are clinically safe and effective.

• Journal of Biomedical Engineering Research
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• v.43 no.4
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• pp.193-198
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• 2022

Contrast enhanced magnetic resonance imaging using gadolinium-based contrast agent (GBCA) is a very useful in vivo technique to visualize the inner ear pathology including endolymphatic hydrops. Although systemic intravenous (IV) administration can visualize the perilymph space, the visualization was possible by indirect passage of contrast agent through blood-perilymph barrier. All animal experimental procedures were performed under anesthesia with 5% isoflurane. Lipopolysaccharide (LPS) was instilled into the left tympanic cavity through the tympanic membrane using a sterile 27gauge needle to induce hydrops model. Tucker-Davis Technologies system was used to measure Auditory Brainstem Responses (ABRs). For intracerebroven-tricular (ICV) administration, 25 µmol of GADOVIST (Bayer, Berlin, Germany) was used and diluted GADOVIST injection was 10 µl. MR imaging was acquired with a 9.4 Tesla MRI scanner. Transmit-receive volume coil with 40 mm inner diameter and 75 mm out diameter was used. ICV administration well demonstrated the strong enhancement along the cerebrospinal fluid (CSF) microcirculation pathway including CSF fluid in the subarachnoid space and CSF space of the inner ear structures. On the other hand, IV administration showed no contrast enhancement along the CSF microcirculation pathway and showed weak enhancement in the inner ear structures. In case of rat hydrops model, ICV administration showed that the reduced contrast enhancement in the perilymph space of the hydrops induced inner ear compared to the contrast enhancement in the perilymph space of the normal inner ear. New systemic ICV administration method provide contrast enhancement of GBCA in the inner ear through CSF microcirculation pathway.

• Journal of Korean Society of Forest Science
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• v.43 no.1
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• pp.20-30
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• 1979

The purpose of present study is to analyze the genetic variation of natural stand of Pinus densiflora. In 1976 following after the seletion of 1974 and 1975, twenty trees from each of three natural populations of the species were selected and seeds were collected, and the locations and conditions of populations are presented in table 1, 2 and figure 1. Some morphological traits of the populations were already detailed in our fifth report of this series. The morphological traits of cone, seed and seed-wing, and also the growth performances and needle characters of the seedling were observed in the present study according to the previous methods. The results obtained are summarized as follows; 1. The meteorological data obtained by averaging the records of 30 year period(1931~1960) measured from the nearest meteorological station to each population are shown in fig. 2, 3, 4. The distributional patterns of investigated climate factors are generally considered to be similar among the locations. However, the precipitation density during growing season and the air temperature during dormant season on Samchuk area (Pop. 9) were quite different from those of the other areas. 2. The measurements of fresh cone weight, length, diameter and cone index (i.e.: length to diameter ratio) are presented in table 7. As shown in table 7, all these traits except for cone diameter seem to be not significant in population and to be highly significant in family differences within population. 3. The morohological traits of seed and seed-wing are detailed in table 8, 9, and highly significant differences are recognized among the populations and the families within population in seed weight, seed length, seed thickness but not among the populations in the other observed traits. The values of correlation between the characteristics of cone and seed are presented in table 12. As shown, the correlation between cone length and seed wing length, between seed wing width and seed width were significantly positive in population 8 and 9 but in population 7. The positive correlations between seed length and seed width were calculated in all populations studied 4. Significant statistical differences among populations and families within population are observed in the growth performances of 1-0 seedling height of these progenies. But the differences in 1-1 seedling height and root collar diameter are shown only among familes within population. As shown in table 13, the most parts of correlations are not significant statistically between the growth performances of seedling and the seed characters. 5. As shown in table 15, statistical differences are considered to be significant among the populations in stomata row on both sides of the needle but not in serration density. The correlations between progenies and parents are not generally observed in the investigated traits of needle as shown in table 16.

• Journal of the Korean Ceramic Society
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• v.43 no.2 s.285
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• pp.126-130
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• 2006

Nano-sized hydroxyapatite (HAp) powders were synthesized by a microwave-hydrothermal method using $H_3PO_4\;and\;Ca(OH)_2$ as starting materials. The applied microwave powers and mole ratio of Ca/P were served as powerful factors in the synthesis of calcium phosphate. In the case of relatively low microwave power of 450 Wand Ca/P ratio of 1.57, the mixed calcium phosphate compounds were detected in the synthesized powders. But in the case of running at 550 Wand 1.67(Ca/P), the synthesized powder showed the monophase of HAp having two kinds of morphologies. One was a needle shape with $5\~15\;nm$ in width and $20\~50\;nm$ in length, and the other was a spherical shape of $10\~40\;nm$ in diameter.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.5
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• pp.547-550
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• 2011

We have developed a laser-based needle-free liquid drug-injection device. A laser beam is focused inside the liquid contained in the rubber chamber of a micro-scale. The focused laser beam causes explosive bubble growth, and the sudden volume increase in a sealed chamber drives a microjet of liquid drug through the micronozzle. The exit diameter of a nozzle is less than 100 ${\mu}m$, and we verify that the injected microjet is fast enough to penetrate soft human tissue. In the experiment, the microjet penetrated a 5% gelatin-water solution that replicates the human thrombus and pork-fat tissue.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.7
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• pp.441-446
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• 2017

Aluminum nitride fibers were synthesized by carbothermal reduction and nitridation of precursor fibers obtained by electrospinning. The starting materials used to synthesize the AlN fibers were $Al(NO_3)_3{\cdot}9H_2O$ and urea. Polyvinylpyrrolidone with increasing viscidity was used as the carbon source to obtain a composite solution. The mixed solution was drawn into a plastic syringe with a stainless steel needle, which was used as the spinneret and connected to a 20 kV power supply. A high voltage was supplied to the solution to facilitate the formation of a dense net of fibers on the collector. The precursor fibers were dried at $100^{\circ}C$ and then heated to $1,400^{\circ}C$ for 1 h in a microwave furnace under $N_2$ gas flow for the carbothermal reduction and nitridation. X-ray diffraction studies indicated that the synthesized fibers consisted of the AlN phase. Field emission scanning electron microscopy studies indicated that the diameter of the calcined fibers was approximately 100 nm.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2003.11a
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• pp.151-155
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• 2003

The requirements for harsh environment electronic controllers in automotive applications have been steadily becoming more and more stringent. Electronic substrate technologists have been responding to this challenge effectively in an effort to meet the performance, reliability and cost requirements. An effect of the plasma cleaning at the alumina substrate and the IMC layer between $Sn-37wt\%Pb$ solder and Ag-Pd thick film conductor after reflow soldering has been studied. Organic residual carbon layer was removed by the substrate plasma cleaning. So the interfacial adhesive strength was enhanced. As a result of AFM measurement, Ag-Pd conductor pad roughness were increased from 304nm to 330nm. $Cu_6Sn_5$ formed during initial ref]ow process at the interface between TiWN/Cu UBM and solder grew by the succeeding reflow process so the grains had a large diameter and dense interval. A cellular-shaped $Ag_3Sn$ was observed at the interface between Ag-Pd conductor pad and solder. The diameters of the $Ag_3Sn$ grains ranged from about $0.1\~0.6{\mu}m$. And a needle-shaped $Ag_3Sn$ was also observed at the inside of the solder.

• Korean Journal of Veterinary Service
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• v.39 no.3
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• pp.193-197
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• 2016

A 12-years-old Maltese (castrated male) dog with jaundice and purulent discharge from the shoulder was referred to the Veterinary Medical Teaching Hospital of Chungnam National University. A physical and laboratory examination revealed that the mucosa of the conjunctiva and the sclera were icteric, and the liver functional enzyme level and the total bilirubin level were increased. Duodenal caudal deviation caused by suspected masses in diameter of about 2 cm was shown by radiographic and ultrasonographic examinations. Using fine needle aspiration (FNA) and computed tomography (CT), the dog was diagnosed with alimentary lymphoma. The dog was treated with chemotherapy. Hematuria was discovered and dysuria occurred because of sterile hemorrhagic cystitis, which is a unique complication resulting from the use of cyclophosphamide.

• Korean Journal of Head & Neck Oncology
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• v.15 no.1
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• pp.89-91
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• 1999

We experienced a case of the papillary thyroid carcinoma seen as a huge solid lateral neck mass. The mass grew very slowly over the period of 30years up to 10cm in diameter while relatively well sparing the surrounding tissues. Physical examinations, CT scan, and fine needle aspiration cytology did not reveal any strong suggestions for evidence of malignancy. But it was pathologically diagnosed as metastatic thyroid carcinoma by excisional biopsy. We emphasize that for a large solitary neck mass which persists for several decades, head and neck surgeons should always keep in mind the possibility of metastasis from the malignancy of thyroid gland.

• Journal of Pharmaceutical Investigation
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• v.29 no.4
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• pp.323-327
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• 1999

To protect ${\beta}-carotene$ at the stomach and to release rapidly at the intestine we prepared alginate beads containing ${\beta}-carotene$. ${\beta}-carotene$ and alginate solution was homogenized and prepared o/w emulsion was prepared. It was poured into $Ca^{2+}$ solution through syringe needle. The gel was formed spontaneously and alginate beads containing ${\beta}-carotene$ were prepared. ${\beta}-Carotene$ was incorporated into the beads more than 95%. The release rate of ${\beta}-carotene$ was dependent on the concentration of $Ca^{2+}$, ${\beta}-carotene$ and surfactants. However, the concentration of alginate did not affect the release rate of ${\beta}-carotene$. The high concentration of $Ca^{2+}$ slowed down the release rate of ${\beta}-carotene$. The addition of surfactants in the ${\beta}-carotene$beads increased the release rate of ${\beta}-carotene$ in the order of Tween 80 > Cremophor > Span 20. The contents of ${\beta}-carotene$ and diameter of ${\beta}-carotene$ beads did not change significantly at $50^{\circ}C$ for 20 days.