To be better fit for highways, pavement systems are required to provide comfortable and safe driving and be structurally durable. Composite pavements can be an effective option as they are more durable by placing a high functional asphalt overlay on a rigid concrete base layer. In order to apply a composite pavement system to the field, it is necessary not only to develop technologies that prevent reflecting crack and deterioration of the base layer, but also to improve bonding performance of materials and ensure structural performance as a pavement system against traffic loading. In advanced countries like Japan, USA and Europe, high-functional composite pavement systems are being put into practice across new highway networks. In this study, we evaluated structural performance (rutting, reflecting crack, and deflection) by applying traffic loads of actual highways through an accelerated pavement tester (APT) of a composite pavement section made up of a quiet porous surface laid over a water-proofing layer, a continuously reinforced concrete base, and a lean concrete sub-base layer, which was developed with new pavement methods used for each layer prior to field application. The APT specimen was constructed with paving materials and equipment actually used on site in the same dimensions (W3.5m*L14m*H2m) as actual highway sections in Korea, and 3-axle double-wheel heavy load (45ton) cart type KALES(Korean Accelerated Loading and Environmental Simulator) traveling on the specimen in both directions was used to simulate traffic loading. After applying around 8,574,000 ESALs of traffic loads, no reflecting crack occurred on the asphalt surface of the composite pavement, without surface distress except for rutting. In order to examine what causes rutting of pavements, we surveyed thickness of pavements by layer and measured asphalt density.
In recent years, pavement distresses have been caused by diverse factors such as spalling, deterioration of repaired sections, blow-up, and alkali aggregate reaction due to changing climate environment of a concrete pavement and its construction and maintenance conditions (supply of materials, increase in use of de-icers, etc,). As a leading repair method for deteriorated concrete pavements, partial-depth repair is implemented in accordance with guidelines of material properties for joints of a concrete pavement and field application evaluation systems, but still some of the repaired sections become deteriorated again at an early stage due to poor construction quality and failure of response to environmental impacts. Distresses that can be corrected with partial-depth repairs are largely divided into those of repair materials and of the existing pavement bonded to repair materials, and combined distress of repair materials and the existing pavement. Although re-repair methods should be different by distress type and scale than conventional pavement repair methods, appropriate repair methods and guidance for re-repairs have not been in place so far, and therefore currently, re-repair practices follow the existing manual of partial depth repairs. Therefore, this study evaluated concrete bond characteristics by removing method and repair scope for an experimental section of frequently distressed pavements to determine a re-repair scope and method for deteriorated partial depth repair sections of concrete pavement, the number of which has increased over time.
Composite pavements are constructed by placing a high functional asphalt surface layer on a high performance concrete rigid base layer and provide a more durable, high functional surface to road users. Service life of composite pavements is dependent on the bonding performance of the lower rigid base and the flexible surface layer. Accordingly, it is necessary to place an impermeability layer between the functional surface layer and the rigid base to enhance bonding performance and to prevent moisture penetration into the rigid base and deterioration of pavement. In order to use optimal composite pavement sections, two types were applied to impermeability layer: highly impermeable water-tight SMA and mastic asphalt currently in use. APT (Accelerated Pavement Testing) and experimental construction were carried out to evaluate bond strengths between the rigid base and the impermeability layer depending on the type of impermeability layers. Composite pavement sections for the APT had a 22 cm concrete rigid base layer and a 5cm functional surface, as well as either 5cm of SMA impermeability layer and 5cm of mastic layer. After applying around 8,574,000 ESALs, pull-off test was conducted, which showed that the mastic section outperformed the SMA section. In the experimental construction, three types of rigid base layers, JCP (Jointed Concrete Pavement), CRCP (Continuously Reinforced Concrete Pavement), and RCCP (Roller Compacted Concrete Pavement), were used for composite pavement sections, and as in the APT, two types of impermeability layers, SMA and mastic, were used per rigid base layer of new and deteriorated concrete pavement. Therefore, seven composite pavement sections in total were constructed. We measured the bond strength over one year or so following the construction of these composite pavement sections and found that regardless of the type of rigid base layer and whether it was new or not, those sections with a mastic impermeability layer had high bond strengths.
In Korea, concrete pavements were first applied to highways in 1981 and as a result of continued increase in length over the past years, 2,592 km of concrete pavement network is currently in service, of which 1,399 km(54%) of concrete pavements is 10 years or older, and 233km(9%) is 20 years or older. The length of concrete pavement sections nationwide has been steadily on the rise every year (EXTRI, 2017). Approximately 54% of current concrete pavement highway network will reach the service life limit in 2025 which means around 660 billion won is needed for future pavement repair project (EXTRI, 2017). Given that concrete pavements beyond design life still have a remaining service life, it is economically advantageous to repair them before reconstruction. Asphalt overlays are a major repair method for older concrete pavements. Depending on the concrete pavement condition, thickness and mixture of asphalt overlays are determined. Service life of asphalt overlays varies by the presence, time and size of cracks in existing concrete pavements and reflecting crack at joints. Temperature change of concrete pavement is among the major reaction parameters of reflecting crack. Reflecting crack develops when asphalt bottom-up cracking by longitudinal shrinkage and expansion due to temperature change of the concrete base layer, top-down cracking by temperature difference between top and bottom of concrete, and shear stress by traffic loading are combined (Baek, 2010). Crack and joint behaviors of concrete pavement vary between the base layer and the concrete surface of composite pavement system, and different conductivity by mixture and thickness of asphalt overlay leads to temperature change of concrete base course. This study measured temperatures of each layer of diverse composite pavements in place on site and analyzed differences in temperature change of concrete base layer depending on mixture and thickness of asphalt overlays. Overlay thickness parameters were 5cm and 10cm, two values most widely used, while mixture parameters were SMA and porous asphalt. Based on temperature change of concrete surface, this study also evaluated the difference of temperature change in concrete base layer with an asphalt overlay on top. Findings from this study are expected to be utilized for studies on mechanism and modeling of reflecting crack in old concrete pavements with asphalt overlays.
Skeletal deformities are significant problems that affect the growth and commercial value of fish reared in hatcheries. However, studies of bone metabolic process related to skeletal deformities are limited. We investigated the potential correlation between bone deformities and plasma calcium, phosphorus, and estradiol-17β levels in reared red spotted grouper (Epinephelus akaara) juveniles. We collected E. akaara frys from private farms at 110, 140, 180 and 300 days after hatching (DAH), and classified the normal and deformed fish by observing their external shape and inner frame by soft X-ray. We also analyzed the calcium, phosphorous, and estradiol-17β levels in their plasma. A comparison between normal and deformed fish, indicated that calcium and estradiol-17β levels were higher in deformed fish than in the normal at 180 and 300 DAH. The level of phosphorus was also higher in deformed individuals than in normal fish, but only at 300 DAH. These results suggest that skeletal deformities are associated with increases in plasma calcium, phosphorus, and estradiol-17β levels.
The objective of the current study was to determine acute plasma stress responses in two size groups of juvenile Epinephelus akaara (average body weight: 8.4±2.1 and 3.3±0.6 g; 150 and 120 days after hatch, respectively) exposed to abrupt salinity drops (from 34 practical salinity unit, PSU seawater to 18, 10 PSU (experiment 1) or 26, 18, 10 PSU (experiment 2), respectively). Plasma glucose, glutamic oxalate transaminase, glutamic pyruvate transaminase, red blood cell counts, and gill histology were determined during 72 h exposure. Significantly increased plasma glucose, glutamic oxalate transaminase levels, and red blood cell counts were observed in fish exposed to 18 or 10 PSU. Histological changes, such as hyperplasia and lifting of epithelium in the gill secondary lamellae, were also observed in fish exposed to 18 or 10 PSU at 72 h post-drop. E. akaara exposed to sudden salinity drops to 18 or 10 PSU still seems to undergo the primary adjustment phase before fish reaches a new homeostasis, whereas fish exposed to 26 PSU seems to mount osmotic changes. Therefore, the no observed adverse effect levels for 72 h acute salinity challenge was 26 PSU in our study, and salinity drop to 18 PSU and below can possibly cause acute adverse effect, in which fish could be vulnerable to additional stresses such as a temperature changes or handling stress.
We sought to identify optimal temperatures for aquaculture of juveniles at a length of 7.2 cm ± 0.1 cm. The impact of four temperatures (20℃, 24℃, 28℃, and 32℃) on feeding rate, growth performance, and stress responses (i.e., blood cortisol, glucose, alanine transaminase [ALT], and aspartate transaminase [AST] content) of juvenile red-spotted grouper was measured over a period of 6 wks.
Red-spotted grouper had significantly higher final body weight (g) at 24℃ and 28℃ than at 20℃ or 32℃, and greater percentage body weight increase/day at 24℃ than at 28℃. There were significant differences in feeding rate, depending on the number of weeks. The 6-wk feeding rate was highest at 28℃, followed by 32℃, 24℃, and 20℃, while the lowest feed conversion ratio occurred at 24℃, followed by 28℃, 32℃, and 20℃. After 6 wks, there were no significant differences in plasma cortisol or AST levels. However, there were significant increases in plasma glucose and ALT levels at 32℃ compared to at 20℃. Although red-spotted grouper at 32℃ did not show a significant increase in blood cortisol levels, our results suggested that at 32℃ the red-spotted grouper experiences high energy-demand (i.e., high glucose level) and stress (i.e., high ALT), especially in the liver.
Based on body weight, % body weight increase/day, feed conversion ratio, and stress indicators, the optimal temperature for aquaculture of red-spotted grouper was ~24℃. Additional studies at temperatures between 24℃ and 28℃ will be required to identify the exact optimal temperature for juvenile red-spotted grouper culture.
This study was conducted to determine the stress response [ethological (operculum movement number (OMN)), hematological (hematocrit and hemoglobin), biochemical (glucose, cortisol and glutamic oxaloacetic transaminase (GOT))] in red spotted grouper, Epinephelus akaara during exposure of different water temperature in winter season. This species (Total length, 18.56±0.34 cm) previously maintained in water temperature of 15°C were transferred to 15, 20 and 25°C. During experimental period (7 days), OMN, hematocrit (Ht), glucose and GOT values were significantly high in 15°C when compared to 20 and 25°C. Hemoglobin value was also increased at 15°C, but no significant differences. There was no differences in cortisol levels among the temperature groups. No fish mortality was observed during the experimental period. From these results, 15°C is likely more stressful to red spotted grouper than 20°C and 25°C. These observations confirm that red spotted grouper adapts better to temperatures between 20 and 25°C during the winter season.
In this study, oocyte steroidogenesis are investigated in relation to oocyte development in the starry flounder, Platichthys stellatus, a marine multiple spawner. Vitellogenic (0.52 and 0.55 mm oocyte diameter) and mature oocytes (0.63, 0.66 and 0.71 mm oocyte diameter) were incubated in vitro in the presence of [3H]17α-hydroxyprogesterone ([3H]17α- OHP) as a precursor. Steroid metabolites were extracted from the incubated media and oocytes, the extracts were separated and identified by thin-layer chromatography (TLC), high performance liquid chromatography (HPLC) and gas chromatographymass spectrometry (GC-MS). The major metabolites produced from [3H]17α-OHP were androgens [androstenedione (A4) and testosterone (T)] and estrogens [17β-estradiol (E2) and estrone (E1)] and progestins [17α,20α-dihydroxy-4-pregnen- 3-one (17α20αP) and 17α,20β-dihydroxy-4-pregnen-3-one (17α20βP)] in vitellogenic and mature oocytes. The results from this study suggest the potential roles of E1 in the oocytes with diameter 0.52-0.71 mm, 17α20αP and 17α20βP at the oocytes of 0.63, 0.66 and 0.71 mm.
To evaluate the effects of benzo[a]pyrene (B[a]P), one of polycyclic aromatic hydrocarbons (PAHs), on in vitro oocyte maturation (GVBD) and sex steroid hormone production, maturing oocytes (oocyte diameters=0.74, 0.88 and 0.93 mm) of the longchin goby, Chasmichthys dolichognathus were incubated with B[a]P (1, 10 and 100 ng/mL) for 24 hours. After incubation, the oocytes were fixed with clearing solution (ethanol:formalin:glacial acrtic acid=6:3:1). The location of the germinal vesicle was observed under low-power magnification using a dissecting microscope. Steroids in aliquots of the incubation media were extracted twice using five volumes of ethylacetate:cyclohexane (1:1). Then, the T, E2 and 17α20βP levels were measured by RIA. In oocytes 0.74 mm diameter (vitellogenic oocytes), B[a]P had no significant effect on GVBD at the concentrations tested. In oocytes 0.88 mm diameter (fully vitellogenic oocytes), B[a]P inhibited GVBD significantly at 1 and 100 ng/mL. T production was decreased and the ratio of E2/T was increased significantly at 1 and 10 ng/mL compared with control. In 0.93 mm diameter oocytes (germinal vesicle located near the center of oocytes), B[a]P induced GVBD significantly at 10 and 100 ng/mL and decreased the ratio of E2/T significantly at 1 and 10 ng/mL compared with control. These findings suggest that B[a]P has different sensitivity to the oocyte maturation according to the oocyte diameters.
We investigated the changes in plasma sex steroid hormones, testosterone (T), estradiol-17β (E2), 17,20 β-dihydroxy-4-pregnen-3-one (17α20βOHP), 11-ketotestosterone (11KT) and cortisol levels from ribbed gunnel, Dictyosoma burgeri in associated with annual reproductive cycle. The fish were collected at the coastal waters of Dadaepo, Busan, Korea from August 2002 to March 2003. Body weight, liver weight and gonad weight were measured for calculation of hepatosomatic index (HSI) and gonadosomatic index (GSI). Plasma steroid and cortisol levels were measured by radioimmunoassay and data were analyzed using the Kruskal-Wallis test and the Spearman rank correlation. The GSI of females increased from November, peaked in February (13.21±2.27) and decreased rapidly from March (1.05±0.23). The GSI of males also increased from November, peaked in December (0.36±0.12) and remained high to February. In females, E2 levels increased and remained high from December to February (19.81±7.46～22.85±6.18 ng/ ㎖). The levels of T showed a similar tendency and correlated (rs=0.813, p=0.0001) significantly with E2 levels. The levels of 17α20βOHP increased rapidly in February (4.78±1.01 ng/㎖) and peaked in July (5.08±0.65 ng/㎖). Cortisol level was peaked in March (2081.07±1140.02 ng/㎖) and correlated significantly with 17α20βOHP levels (rs=0.790, p=0.0001). In males, the levels of T was peaked in January (2.43±0.17 ng/㎖) and then decreased rapidly. The levels of 11KT were remained high from October to January (3.27±1.55～4.28±1.53 ng/㎖) and correlated significantly with T levels (rs=0.513, p=0.002). On the other hand, the levels of 17α20βOHP fluctuated during reproductive cycle and the variation pattern of cortisol levels were similar to females. These results suggest that plasma sex steroids in ribbed gunnels have annual periodicity, and that cortisol may involve in maturation of females.
This study is to survey the ultrastructure of gamete cells and micropyle of pre-fertilized and post-fertilized eggs after HCG hormone treatment by transmission and scanning electron microscopy (TEM and SEM) in E. akaara, E. bruneus and E. septemfasciatus. These fishes are economical importance species for Jeju coastal area resources. In spite of its an importance resources, details studies on the ultrastructural aspects of gamete cells for its reproductive biology have not been undertaken. Morphological features of ovulation process have been studied during its normal occurrence in the reproductive cycle of these fish by light microscopy. Moreover, it has been studied for many years to induce spawning by environmental factors (day length, water temperature etc) or injection of HCG for ovulation in these species. Studies on the micropyle was mainly focused on the eggs of insects, fresh water and a few sea water fishes. Micropylar structure of fish displays morphological characteristics of interspecies-specific by inhabitant environment and spawning feature. On the other hand, it is an importance cue for a taxonomical indicator and identification fish eggs. SEM studies were performed on growing and mature oocytes obtained by stripping and cannulation from 3 grouper species sampled between July and August in spawning season. The outer layer of chorion of preovulatory growing stage oocytes could be divided into four layers; zona pellucida, follicular cell layers consisted of granulosa and thecal cells layer and the most outer ovigerous lamella. Ovulation process of mature stage oocytes initiated by rupture of ovigerous lamella and ovulated by contraction of follicular cell layers. Besides, the micropylar shape of ripe stage oocytes in E. akaara, E. bruneus and E. septemfasciatus presented volcano or crateriform-like cylindrical form. Internal structure of micropylar vestibule displayed cylindrical clockwise 8 or 10 spiral arrangement structure in these species. The micropyle diameter and apparatus at the animal pole differ significantly among the 3 species. The difference in their diameters suggests species-specific in the correlation between spermatozoal head size and micropylar diameter for polyspermy prevention and hybridization during fertilization. Besides, after artificial fertilization, the vestibule morphologically transformed into dom-shape and pillar-shape for fertilization cone formation. Pores of various sizes in the 3 grouper species were somewhat regularly distributed in concentric circles only around the micropyle. In particular, large pores had numerous gill filament-shaped projections connected to oolemma. These structures are suggested to be related to gas exchange, osmoregulation, and micronutrient influx or efflux between eggs and water during fertilization and egg development. In addition, spermatozoa ultrastructure was examined in 3 grouper species. TEM investigation revealed that, in all species, spermatozoa display a round head, a nucleus containing highly condensed, filamentous chromatin clusters, no acrosome, a short midpieces consisting of numerous mitochondria and the proximal and distal centrioles and a flagellum exhibiting the typical axoneme structure (9+2). Especial, both E. akaara and E. bruneus display regular laternal fins in flagella, but in E. septemfasciatus, no fins in flagella with hook shape tails.
본 연구에서는 해산어를 이용하여 bisphenol A(BPA)와 nonylphenol(NP)이 난모세포 성숙 과정에 어떤 영향을 미치는지 조사하기 위해 성숙단계에 있는 노래미(Hexagrammos agrammus) 난모세포(난경 약 1.88 ㎜)를 대상으로 in vitro에서 BPA와 NP 처리에 의한 난모세포의 성스테로이드 생성농도를 조사하였다. 난모세포에 BPA와 NP를 농도구별(0.1, 1, 10, 100, 1,000 ng/㎖)로 첨가하고, 50 IU의 human chorionic gonadotropin(HCG)를 농도구별 BPA 또는 NP와 함께 첨가하거나 하지 않고 48시간 동안 배양하였다. 배양 후 배양액 내의 17α,20β-dihydroxy-4-pregnen-3-one(17α20βOHP), estradiol-17β(E2) 그리고 testosterone(T)의 농도를 방사면역측정법(RIA)을 통해 정량하였다. BPA 처리구에서는 100 ng/㎖의 농도구에서 HCG 처리 유무에 상관없이 E2 생성이 촉진되었다. HCG 처리하에서 0.1 ng/㎖의 농도구에서 T 생성은 촉진되었으나, HCG를 처리하지 않은 실험구의 모든 농도구에서 T 생성은 저해되었다. NP 처리구에서는 HCG를 처리하지 않은 실험구의 10 ng/㎖의 농도구에서 17α20βOHP와 T 생성이 촉진되었고, 1 ng/㎖의 농도구에서는 E2 생성이 억제되었다. 이상의 결과를 종합하면, 노래미의 성숙단계의 난모세포에서 BPA는 약한 estrogen-agonistic 효과를, NP는 estrogen- antagonistic 효과를 지니는 것으로 사료된다.