Use of mineral trioxide aggregrate in the non-surgical repair of perforating invasive cervical resorption

Mineral trioxide aggregate (MTA) has shown potential as a repair material for perforations. This clinical case demonstrates that when MTA was used as a repair material for root perforation due to invasive cervical resorption, the tooth was well in function for 27 months. Both clinical and radiographic follow-up showed a stable condition without any probing defect, ongoing root resorption, or apical pathosis

리튬 이온 전지용 바나듐계 금속 산화물 전극의 리튬 저장 메커니즘 및 성능 향상

학위논문 (박사)-- 서울대학교 대학원 : 화학생물공학부, 2017. 2. 오승모.리튬 이온 전지는 현시대에 없어서는 안될 중요한 전기 에너지 저장 장치로서 큰 각광을 받고 있다. 이러한 리튬 이온 전지의 사용처가 점차 다변화 됨에 따라 더욱 향상된 에너지 밀도 또는 높은 출력 특성을 가진 전지의 개발이 진행되고 있다. 기존에 주로 사용되던 흑연계 음극재로는 리튬 이온 전지의 에너지 밀도와 출력 특성을 향상시키기에 어려움이 있기 때문에 새로운 금속 산화물 음극재가 연구되고 있다. 금속 산화물 음극재의 리튬 저장 메커니즘은 삽입반응과 전환반응 두 가지로 분류할 수 있다. 삽입반응의 경우에는 충전 시에 리튬 이온이 정해진 격자 내 공극에 저장되고 방전 시에는 가역적으로 빠져나오기 때문에 반응이 매우 안정적이라는 장점이 있으나, 공극 수의 제한으로 인해 용량이 작다는 단점을 가지고 있다. 반면 전환반응의 경우에는 삽입반응과 달리 리튬 이온이 저장되는 사이트가 정해져 있지 않아 용량이 매우 크다는 장점이 있다. 하지만 리튬 충전 시에 금속과 산소 사이의 결합이 끊어지고 방전 시에 그 결합이 다시 이어져야 하기 때문에 큰 과전압이 발생할 뿐만 아니라, 방전반응이 일어나는 전압이 상대적으로 높기 때문에 양극과 함께 셀을 구성하였을 때 에너지 밀도를 충분히 향상시킬 수 없다는 단점을 가지고 있다. 따라서 본 연구에서는 바나듐 이온을 포함한 금속 산화물을 이용하여 위에 서술한 금속 산화물 음극재의 단점을 개선하였다. 먼저 대표적인 삽입반응 금속 산화물인 티타늄 산화물의 용량을 향상시키기 위해 비정질 구조를 도입하고 바나듐 이온을 추가함으로써 비정질 바나듐 티타네이트 (aVTO) 음극재를 합성하여 그 전기화학 특성을 분석하였다. 졸겔법을 통해 합성한 비정질 바나듐 티타네이트는 100 nm 이하의 크기를 가진 일차입자가 뭉쳐져 있는 입자형상을 가지고 있는 것을 확인할 수 있었으며, 0.8 – 3.0 V (vs. Li/Li+) 영역에서 충방전 했을 때 295 mA h g‒1 에 해당하는 높은 용량을 발현하였다. 이는 원자단위로 고르게 섞인 티타늄과 바나듐 이온이 비정질상 내에서 새로운 국소구조를 형성함으로써 구조 내에 추가적인 리튬 저장 공간을 형성하고 구조의 전자 구조를 변형시켰기 때문이라 해석할 수 있다. 또한 합성 조건의 최적화를 통해 비정질 바나듐 티타네이트의 표면을 개질함으로써 음극재의 초기 효율 특성과 속도 특성을 보다 개선하였다. 두번째로는 전환반응 금속 산화물의 높은 반응 전압을 보다 낮추기 위해 0.0 V 근처의 낮은 전압에서 전환반응을 통해 리튬을 저장하는 메타바나듐산 리튬염 (LiVO3)을 제안하였다. 음극재로서 처음 제시된 메타바나듐산 리튬염의 리튬 저장 메커니즘을 전기화학, 분광학 실험 및 제일원리계산법을 통해 자세히 분석한 결과 1.5 개의 리튬 이온이 삽입반응으로 저장된 후 3.5개의 리튬이 전환반응을 통해 메타바나듐산 리튬염 내에 저장된다는 것을 확인하였다. 이는 바나듐 산화물 중에서 처음 보고되는 전환반응으로서 메타바나듐산 리튬염에서 전환반응이 일어나는 원인을 바나듐 오산화물과의 비교를 통해 분석한 결과, 리튬, 바나듐, 산소 이온이 메타바나듐산 리튬염 내부에서 보다 쉽게 이동할 수 있기 때문이라 해석할 수 있다. 또한 충방전 과정 중에 구리 금속 입자와 메타바나듐산 리튬염으로 상변이 하는 메타바나듐산 구리를 적용함으로써 메타바나듐산 리튬염을 활물질로 사용한 전극의 수명 성능을 개선하였다. 이러한 성능 향상은 충방전 과정 중에 생성된 금속 구리 입자가 전극 내에서 메타바나듐산 리튬염의 부피 변화를 완충해 주는 역할을 해줄 뿐 아니라 전극 내 전기전도 특성을 향상시키기 때문이다.Lithium-ion batteries (LIBs) are the most important energy storage devices in modern society and they are being utilized in various applications from portable devices to large scale energy storage for vehicles and grids. In order to be quali-fied in these applications, LIBs should have higher energy density and power ca-pability. To further increase the performance of LIBs, transition metal oxides have been studied as alternatives of graphite which has been conventionally used as a negative electrode material. Lithium storage in the transition metal oxides can be divided into two typesinsertion and conversion reaction. In the insertion-type metal oxides, Li+ ions are stored in the interstitial sites during charge (lithiation) and reversibly released during discharge (delithiation). Because this insertion-type of Li+ storage does not accompany large structural distortion, it is highly stable and thus suitable for batteries with long cycle life. However, its reversible capaci-ty is rather limited due to the finite amount of Li+ storage sites in the metal oxide. On the other hand, there are no limited sites for Li+ ions to reside in the conver-sion-type metal oxides. Because of this reason, these metal oxides show much larger Li+ storage capacity. Upon lithiation, metal and oxygen bonds are broken and Li+ and oxygen form new bonds to generate lithium oxide (Li2O) and nano-sized metallic compounds. However, they generally have a large hysteresis during cycles and relatively high redox potentials, which limit the increment of energy density. In this work, the shortcomings of metal oxides stated above are improved with vanadium-based metal oxides. First, amorphous vanadium titanate (aVTO) is examined to enlarge the specific capacity of insertion-type metal oxides. aVTO are synthesized in nano-sized particles (< 100 nm) flocculated to form secondary particles. The V5+ ions in aVTO are found to occupy tetrahedral sites, whereas the Ti4+ ions show five-fold coordination. Both are uniformly dispersed at the atomic scale in the amorphous oxide matrix, which has abundant structural de-fects. The first reversible capacity of aVTO electrode (295 mA h g−1) is larger than that observed with the physically mixed electrode (1:2 aV2O5aTiO2, 245 mA h g−1). The discrepancy seems to be due to the homogeneous mixing of V5+ and Ti4+ ions in atomic scale, which induces four-coordinated V5+ ions in aVTO. This unique structure affects the chemical potential of Li+ storage sites by modi-fying either electronic band structure or generating more structural defects to serve as Li+ storage sites. Li/aVTO cells show a large irreversible capacity in the first cycle. Prepared under nitrogen (aVTO-N), the population of surface hydrox-yl groups is greatly reduced. These groups irreversibly produce highly resistive inorganic compounds (LiOH and Li2O) leading to increased irreversible capacity and electrode resistance. As a result, the material prepared under nitrogen shows higher Coulombic efficiency and rate capability. Secondly, lithium metavanadate (LiVO3) is lithiated by a conversion reaction near 0.0 V, which is much lower po-tential for conversion-type metal oxides. The electrochemical, spectroscopic stud-ies and first-principle calculations performed on the lithiation mechanism of Li-VO3 consistently propose that a two-phase insertion-type lithiation proceeds in the early stage of lithiationLiVO3 transforms into a rock-salt structured Li2VO3. The continuing single-phase Li+ insertion into the tetrahedral sites in the above rock-salt Li2VO3 produces a more Li-rich phase (Li2.5VO3), which is highly distorted because of the unfavorable Li+ insertion into the tetrahedral sites to be vulnerable to lattice breakdown. Hence, a two-phase (nucleation/growth type) conversion reaction is followed along with a structural disintegrationthe Li2.5VO3 phase de-composes into metallic vanadium and Li2O. To determine the factors facilitating the conversion reaction of LiVO3, electrochemical and theoretical analysis are performed and the results of which are then compared to those observed with V2O5, which is not lithiated by the conversion reaction at 25°C. The results show that the quasi-equilibrium potential for the conversion reaction is more positive for LiVO3 (thermodynamically more feasible). Also, the conversion reaction is kinetically more facilitated for LiVO3 due to faster solid-state diffusion of mobile ionic species during the two-phase growth stage of metallic vanadium and lithium oxide (Li2O) in the conversion process., Furthermore, copper vanadate (CuV2O6), which generates Cu/LiVO3 nanocomposite during the first cycle, is demonstrated as a negative electrode material that can further enhance the cycle life of LiVO3 electrode. The Li/CuV2O6 cell shows a high cycle retention, which seems to due to the beneficial roles offered by the metallic copper, which plays as a buffer against the volume change of electrode component and as an electron conducting channel.1. INTRODUCTION 1 2. BACKGROUND 5 2.1. Overview on lithium-ion batteries (LIBs) 5 2.1.1. Basic principles and components of LIBs 5 2.1.2. Characteristics and general requirements of LIBs 8 2.2. Negative electrode materials 10 2.2.1. Lithium metal 10 2.2.2. Carbonaceous materials 10 2.2.3. Alloying materials 12 2.2.4. Transition metal oxides 13 3. EXPERIMENTAL 19 3.1. Synthesis of materials 19 3.1.1. Amorphous vanadium titanates (aVTO, aVTO-N) 19 3.1.2. Lithium metavanadate (LiVO3) 19 3.1.3. Copper vanadate (CuV2O6) 20 3.2. Electrochemical analysis 20 3.2.1. Electrode fabrication 20 3.2.2. Cell fabrication 21 3.2.3. Galvanostatic charge/discharge 22 3.2.4. Potentiostatic intermittent titration technique (PITT) 22 3.2.5. Electrochemical impedance spectroscopy (EIS) 22 3.2.6. Galvanostatic intermittent titration technique (GITT) 23 3.3. Material characterization 23 3.3.1. Electron microscopy 23 3.3.2. Spectroscopic analysis 24 3.3.3. Other techniques 26 3.4. Computation methods 26 4. RESULTS AND DISCUSSION 28 4.1. Insertion-type lithium storage in amorphous vanadium titanate (aVTO) and its performance improvements 28 4.1.1. Material characterization 30 4.1.2. Electrochemical properties and ex-situ analysis 39 4.1.3. Performance improvements of aVTO via modification of synthetic atmosphere 45 4.1.4. Summary of Section 4.1. 63 4.2. Conversion-type lithium storage in lithium metavanadate (LiVO3) and its performance improvements 67 4.2.1. Material characterization of lithium metavanadate (LiVO3) 72 4.2.2. Electrochemical properties and ex-situ analysis 75 4.2.3. Theoretical analysis 86 4.2.4. Lithium storage mechanism of LiVO3 94 4.2.5. Comparative study on the conversion reaction of vanadium oxides (LiVO3 and V2O5) 94 4.2.6. Performance improvements of LiVO3 via modification of the material's chemistry 102 4.2.7. Summary of Section 4.2. 123 5. CONCLUSIONS 127 REFERENCES 130 국문초록 139Docto

Effects of strobe light stimulation on postnatal developing rat retina

The nature and intensity of visual stimuli have changed in recent years because of television and other dynamic light sources. Although light stimuli accompanied by contrast and strength changes are thought to have an influence on visual system development, little information is available on the effects of dynamic light stimuli such as a strobe light on visual system development. Thus, this study was designed to evaluate changes caused by dynamic light stimuli during retinal development. This study used 80 Sprague-Dawley rats. From eye opening (postnatal day 14), half of the rats were maintained on a daily 12-h light/dark cycle (control group) and the remaining animals were raised under a 12-h strobe light (2 Hz)/dark cycle (strobe light-reared group). Morphological analyses and electroretinogram (ERG) were performed at postnatal weeks 3, 4, 6, 8, and 10. Among retinal neurons, tyrosine hydroxylase-immunoreactive (TH-IR, dopaminergic amacrine cells) cells showed marked plastic changes, such as variations in numbers and soma sizes. In whole-mount preparations at 6, 8, and 10 weeks, type I TH-IR cells showed a decreased number and larger somata, while type II TH-IR cells showed an increased number in strobe-reared animals. Functional assessment by scotopic ERG showed that a-wave and b-wave amplitudes increased at 6 and 8 weeks in strobe-reared animals. These results show that exposure to a strobe light during development causes changes in TH-IR cell number and morphology, leading to a disturbance in normal visual functions

Suppression of STAT3 and HIF-1 Alpha Mediates Anti-Angiogenic Activity of Betulinic Acid in Hypoxic PC-3 Prostate Cancer Cells

Background: Signal transducer and activator of transcription 3 (STAT3) is a transcription factor that regulates various cellular processes such as cell survival, angiogenesis and proliferation. In the present study, we examined that betulinic acid (BA), a triterpene from the bark of white birch, had the inhibitory effects on hypoxia-mediated activation of STAT3 in androgen independent human prostate cancer PC-3 cells. Methodology/Principal Findings: BA inhibited the protein expression and the transcriptional activities of hypoxia-inducible factor-1a (HIF-1a) under hypoxic condition. Consistently, BA blocked hypoxia-induced phosphorylation, DNA binding activity and nuclear accumulation of STAT3. In addition, BA significantly reduced cellular and secreted levels of vascular endothelial growth factor (VEGF), a critical angiogenic factor and a target gene of STAT3 induced under hypoxia. Furthermore, BA prevented in vitro capillary tube formation in human umbilical vein endothelial cells (HUVECs) maintained in conditioned medium of hypoxic PC-3 cells, implying anti-angiogenic activity of BA under hypoxic condition. Of note, chromatin immunoprecipitation (ChiP) assay revealed that BA inhibited binding of HIF-1a and STAT3 to VEGF promoter. Furthermore, silencing STAT3 using siRNA transfection effectively enhanced the reduced VEGF production induced by BA treatment under hypoxia. Conclusions/Significance: Taken together, our results suggest that BA has anti-angiogenic activity by disturbing th

Suppression of the Sweat Gland Sensitivity to Acetylcholine Applied Iontophoretically in Tropical Africans Compared to Temperate Japanese

Tropical inhabitants possess the ability of heat-tolerance through permanent residence in the tropics. Previously, we had shown that tropical African and Thai subjects regulate the core temperature with less amount of sweat against heat compared to temperate Japanese subjects and that suppression of sweating in tropical subjects was attributed to suppression in both central and peripheral sudomotor mechanisms. To elucidate the peripheral mechanisms of the suppressed thermal sweating in tropical natives, sweating responses to acetylcholine (ACh), a primary transmitter of the sudomotor innervation, were compared between Japanese (20 healthy males) and Africans (10 healthy males). ACh was iontophoretically administered on the forearm. Directly activated and axon reflex-mediated sweat responses were evaluated by quantitative sudomotor axon reflex test. The sweat on-set-time was 0.72 min shorter (P<0.01) and the sweat volumes were 72% - 110% higher (P<0.01) in the Japanese than the Africans. Iodine-impregnated paper method revealed that sweat gland density was 50.6% higher (P<0.001) and sweat gland output per single gland was 20.4% larger (P<0.001) in the Japanese compared to the Africans. The Japanese showed the a 0.17℃ higher oral temperature and a 0.30℃ higher forearm skin temperature compared to the Africans (P<0.05, respectively) at rest under a thermoneutral condition. ACh iontophoresis did not produce any influences on oral temperature, but increased the local skin temperature in both the Japanese and the Africans. These results indicate that suppressed thermal sweating in Africans is, at least in part, attributed to the suppressed glandular sensitivity to ACh through both recruitment of sweat glands and sweat output per each gland

Coffee intake may promote sudomotor function activation via the contribution of caffeine

ObjectivesTo determine whether drinking coffee with caffeine accelerates the sympathetic response to acetylcholine (ACh).MethodsTests were performed twice at 1-week intervals following the intake of coffee. Subjects were randomly divided into two groups: Group A was administered 16 fluid oz of water (CON), while Group B was given 16 fluid oz of coffee (Coffee). After 1 week, Group A was administered 16 fluid oz of coffee (Coffee), while Group B was given 16 fluid oz of water (CON). The quantitative sudomotor axon reflex test (QSART) was performed after intake of coffee and water and a 40 min break. QSART with iontophoresis and 10% ACh was performed to determine axon reflex (AXR) mediated with and without iontophoresis [AXR (1) and AXR (2), respectively], and directly activated sweating (DIR).ResultsThe sweat onset time of the AXR was shorter in the Coffee compared with the CON (p &lt; 0.05). The sweat rates in AXR (1) AXR (2) and DIR were significantly higher in the Coffee than in the CON (p &lt; 0.05, p &lt; 0.05, p &lt; 0.01, respectively). In addition, the Coffee showed significantly higher density of activated sweat glands and activated sweat gland output than the CON (p &lt; 0.05, p &lt; 0.01, respectively). The overall results of this study showed that coffee intake could stimulate higher activation in both AXR and DIR sweat responses.ConclusionCoffee intake can improve sweating sensitivity in both the AXR and DIR by the contribution of caffeine contained in coffee. This suggests that other compounds in coffee may not inhibit the sympathetic response to ACh. Therefore, coffee may be clinically worth considering as a supplement for the activation of the cholinergic and sudomotor function

Fully integrated lab-on-a-disc for simultaneous analysis of biochemistry and immunoassay from whole blood

We report a fully integrated device that can perform both multiple biochemical analysis and sandwich type immunoassay simultaneously on a disc. The whole blood is applied directly to the disposable &quot;lab-on-a-disc&quot; containing different kinds of freeze-dried reagents for the blood chemistry analysis as well as reagents required for the immunoassay. The concentrations of different kinds of analytes are reported within 22 min by simply inserting a disc to a portable device. Using the innovative laser irradiated ferrowax microvalves together with the centrifugal microfluidics, the total process of plasma separation, metering, mixing, incubation, washing, and detection is fully automated. The analyzer is equipped with an optical detection module to measure absorbances at 10 different wavelengths to accommodate the various kinds of reaction protocols. Compared to the conventional blood analysis done in clinical laboratories, it is advantageous for point-of-care applications because it requires a smaller amount of blood (350 mu L vs. 3 mL), takes less time (22 min vs. several days), does not require specially trained operators or expensive instruments to run biochemical analysis and immunoassay separately.close554

Design and Evaluation of Passive Shoulder Joint Tracking Module for Upper-Limb Rehabilitation Robots

As the number of people suffering from shoulder movement disabilities increases, there is a rising demand for shoulder rehabilitation. The natural motion of the shoulder joint [glenohumeral (GH) joint] includes not only three-degrees-of-freedom (DOF) rotation but also three-DOF translation of the joint center due to simultaneous motion of the shoulder girdle. If the motion of the shoulder girdle is restricted, then the arm cannot be raised above a certain posture. This paper presents a passive shoulder joint tracking device that allows three-DOF translation of the shoulder joint while compensating for gravity. The single-DOF vertical tracker with a constant-force spring compensates for the gross weight of the user's arm, the upper limb rehabilitation device, and the tracker itself while allowing vertical tracking motion. The two-DOF horizontal tracker consists of two linear guides arranged perpendicular to each other. The tracker freely follows the shoulder joint in the horizontal plane. The effect of using the passive shoulder joint tracking device was evaluated by means of experiments by combining two popular commercial upper limb rehabilitation apparatuses with the proposed tracker. Nineteen subjects (8 healthy persons and 11 patients with shoulder impairments) participated in the evaluation study. The movement of the GH joint and the interactive force between the subject and the commercial rehabilitation device were analyzed when subjects made the following shoulder movements: flexion/extension and abduction/adduction. The improved tracker allowed a greater range of motion and reduced interaction. The tracker can be combined with existing commercial rehabilitation devices for more natural shoulder movement during rehabilitation tasks

Haulage Methods in Different Areas of Nepal and the Health Condition of the Porters in Kathmandu

The complicated geographical features of Nepal make transport of goods difficult. People have to depend on human power even today, especially porters who use a number of different transport styles. The objectives of this study were to document (1) the characteristics of haulage methods in relation to the geographical conditions, and (2) the diurnal activities and health of porters in Kathmandu. The observed methods used by the porters in Nepal to carry loads were divided into four main classes: (1) on the top of the head, (2) by handcart, (3) in baskets on a yoke across the shoulders, and (4) on the back using a tumpline. The method of carrying a load on the back with a tumpline was most commonly observed, although this style might cause damage to the spinal vertebrae. The study of the diurnal activities and health condition of porters was limited to those in Kathmandu. For this purpose seven porters were interviewed orally. The results can be summarised as follows: (1) luggage of about 60kg to 110kg could be carried, (2) six of the seven porters habitually smoked tobacco and drank alcohol, (3) many porters wore cloth tightly twisted around their waist, and (4) complaints of severe neck pain were not made, but all porters complained of knee and/or back pains. The cervical and lumbar vertebrae of these porters were examined by roentgenological analysis, but no abnormal changes were observed