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        검색결과 34

        1.
        2023.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Background: Reproductive management practices play crucial roles to maximize the reproductive performance of cows, and thus contribute to farm profitability. We aimed to assess the reproductive management of cows currently practiced in the dairy farms in an urban farming system. Methods: A total of 62 dairy farms were randomly selected considering all size of farms such as small (1-5 cattle), medium (6-20 cattle) and large farms (> 20 cattle) from selected areas of Dhaka city in Bangladesh. The reproductive managementrelated parameters viz. estrus detection, breeding method, pregnancy diagnosis, dry cow and parturition management, vaccination and treatment of reproductive problems etc. were obtained in a pre-defined questionnaire during the farm visit. Results: The visual observation method was only used (100.0%; 62/62) for estrus detection irrespective of size of the farms; while farmers observed cows for estrus 4-5 times a day, but only for 20-60 seconds each time. Regardless of farm size, 89.0% (55/62) farms used artificial insemination (AI) for breeding the cows. Intriguingly, all farms (100.0%) routinely checked the cows for pregnancy at 35-40 days post-breeding using rectal palpation technique by registered veterinarian. However, only 6.5% (4/62) farms practiced dry cow management. Notably, all farms (100.0%) provided nutritional supplements (Vit D, Ca and P) during late gestation. However, proper hygiene and cleanliness during parturition was not practiced in 77.4% (48/62) farms; even though 96.7% (60/62) farms treated cows by registered veterinarian for parturition-related problems. Conclusions: While farmers used AI service for breeding and timely check their cows for pregnancy; however, they need to increase observation time (30 minutes/ observation, twice in a day: early morning and early night) for estrus detection, consider dry cow management and ensure hygienic parturition for maximizing production.
        4,000원
        2.
        2022.08 KCI 등재 구독 인증기관 무료, 개인회원 유료
        We report the behaviour of carbon black (CB) nanoparticles (spherical carbon shells), subjected to external pressure, using diamond anvil cell at synchrotron facility. CB nanoparticles have been synthesized by lamp black method using olive oil as combustion precursor and ferrocene as an organometallic additive. The catalyst-assisted CB has an iron oxide (γ-Fe2O3) core and amorphous carbon shell (i.e. core–shell structure). Our present study suggests that the carbon shells are partially transparent to the applied high pressure, and result in the reduction of effective pressure that gets transferred to the iron oxide core. High-pressure Raman spectroscopy results indicate that the surrounding carbon shells get compressed with pressure and this change is reversible. However, no structural transformation was observed till the highest applied pressure (25 GPa). The Raman spectroscopy results also suggests that the carbon shells are less pressure sensitive as their pressure coefficients (dω/dP) of G-peak were calculated (3.79 cm− 1/GPa) to be less than that for other carbon allotropes.
        4,000원
        3.
        2022.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Individual multi-walled carbon nanotubes (MWCNTs) were exposed to the electron beam of 200 kV energy and high resolution transmission electron micrographs were recorded at several time intervals. Interestingly, the nucleation of diamond nanoparticles with in the highly disordered MWCNT matrix upon electron-irradiation is observed. This happens without any assistance of high pressures and temperatures. High pressure X-ray diffraction experiments were performed on core/shell structures which suggest that even the closed structures of carbon resist any inward pressure, thereby ruling out the possibility of a hypothetical internal pressure under the electron irradiation conditions. Our experiments suggest that the transformation of graphitic carbon into diamond in the size window of a few nanometers is possible due to the stability of the diamond and a selective dissolution effect of 200 kV electrons on graphite. A mechanism for the same is proposed.
        4,300원
        11.
        2018.01 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Gold functionalized graphene oxide (GOAu) nanoparticles were reinforced in acrylonitrilebutadiene rubbers (NBR) via solution and melt mixing methods. The synthesized NBR-GOAu nanocomposites have shown significant improvements in their rate of curing, mechanical strength, thermal stability and electrical properties. The homogeneous dispersion of GOAu nanoparticles in NBR has been considered responsible for the enhanced thermal conductivity, thermal stability, and mechanical properties of NBR nanocomposites. In addition, the NBR-GOAu nanocomposites were able to show a decreasing trend in their dielectric constant (ε´) and electrical resistance on straining within a range of 10–70%. The decreasing trend in ε´ is attributed to the decrease in electrode and interfacial polarization on straining the nanocomposites. The decreasing trend in electrical resistance in the nanocomposites is likely due to the attachment of Au nanoparticles to the surface of GO sheets which act as electrical interconnects. The Au nanoparticles have been proposed to function as ball rollers in-between GO nanosheets to improve their sliding on each other and to improve contacts with neighboring GO nanosheets, especially on straining the nanocomposites. The NBR-GOAu nanocomposites have exhibited piezoelectric gauge factor (GFε´) of ~0.5, and piezo-resistive gauge factor (GFR) of ~0.9 which clearly indicated that GOAu reinforced NBR nanocomposites are potentially useful in fabrication of structural, high temperature responsive, and stretchable strain-sensitive sensors.
        4,500원
        12.
        2017.06 구독 인증기관 무료, 개인회원 유료
        Until today, success in germline cells and tissue cryopreservation is limited mainly due to the poor understanding of the complex physiological processes can lead to cell damage during cryopreservation. Germline cells, from both male and female, have unique ability to differentiate into one or more cell lines and thus it becomes a crucial point to store them in subzero temperature with the minimal damage of their functional properties and maximum recovery of unchanged and viable cells when thawed. In the past three decades, a vast research has been performed using various different animal models which in fact have led to development of new methodologies and optimization of older one. However, successful use of animal model has provided the opportunity in research with human germline cells and tissues preservation, but not in all the cases. Therefore, the use of new cryo-protective chemicals and modified protocols have been often found in different groups of researchers based on the types, physical structures, utility and animal species of the specimens to be cryopreserved. This review discusses about the basics of different types of cryopreservation methodologies and commonly used optimized protocols and cryoprotectants for germline cells and tissues preservation.
        4,000원
        13.
        2016.10 구독 인증기관·개인회원 무료
        Spermatogonial stem cells (SCCs) is foundation for spermatogenesis throughout male adult life because they have ability of self-renewal and differentiation into spermatozoa. Storage of such SSCs is very important to study on male reproduction, which would contribute human male infertility to be treated. However, during cryopreservation, the most cells are damaged by cryoinjury such as apoptosis, necrosis, osmotic stress, oxidative stress and so on. For the reason, in cryopreservation technique, targeting purpose is what cells are stored stably without cryoinjury. The purpose of this study was to develop the cryoprotectant for decrease in cryoinjury of SSCs by using melatonin and necrostatin-1 as additive cryoprotectant. The SSCs with melatonin or necrostatin-1 was frozen for 1 month, and then thawed to evaluate survival, recovery and proliferation rate. The result showed that necrostatin-1 50 mM was significantly greater than DMSO control. Furthermore, we conducted the characterization of cryo-thawed SSCs with necrostatin-1 50 mM to confirm whether the SSCs could maintain the undifferentiated state. As a result, the normal expression of each marker, which is PLZF, GFRa1 and VASA, was observed except for C-kit, meaning that the cells could maintain the undifferentiated state regardless of cryopreservation. Therefore, the result indicates that the cryo-thawed SSCs have ability of proliferation and self-renewal. In conclusion, our finding verifies that cryopreservation of SSC with necrostatin-1 50 mM could be helpful to preserve the SSCs stably, contributing to various studies on male reproduction and infertility treatment
        14.
        2016.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Isroaniso matrix precursor synthesized from commercially available petroleum pitch was stabilized in air. The influence of oxygen mass gain during stabilization on the yield of matrix precursor was studied. Additionally, the influence of pressure on the yield of the stabilized matrix precursor in a real system was studied. The fourier transform infrared spectrometry (FTIR), thermogravimetric analysis (TGA), yield, yield rate, and yield impact were used to check the effect of stabilization and pressure on the yield of the matrix precursor and the end properties of the composite thereafter. The results showed that the yield increased with stabilization duration up to 20 h whereas it decreased for stabilization duration beyond 20 h. Further results showed that the stabilized matrix precursor for a duration of 5 h could withstand almost two-fold greater hot-pressing pressure without resulting in exudation as compared to that of a 1 h stabilized matrix precursor. The enhanced hot-pressing pressure significantly improved the yield of the matrix precursor. As a consequence, the densification and mechanical properties were increased significantly. Further, the matrix precursor stabilized for a duration of 20 h or more failed to provide proper and uniform binding of the reinforcement.
        4,000원
        15.
        2015.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The study was carried out to assess the production performances of Japanese quail parent stock raised under open housing system and the study was conducted in a local farm with 2000 Japanese parent stock quail birds (Coturnix coturnix japonica). Observed body weight gain was recorded in each weekend up to 7 weeks of their age; birds gained weight 15.73, 31.45, 47.20, 90.80, 125.27, 153.14 and 175.20 grams, respectively. There have been observed sharp decline of fertility and hatchability of birds with increase of their age. Optimum fertility was recorded at third week and optimum hatchability at fifth week of their age. Average flock uniformity was found 83.68%. The hen day egg production of the flock was recorded 81, 83, 85, 86, 89, 89, 89, 89 and 88% in each weekend, respectively. It may therefore be concluded that Japanese quail parent stock performs well under open housing system in Bangladesh and future study can be taken to better understand their production performances.
        4,000원
        16.
        2015.01 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The prime objective of this research was to study the influence of hot-pressing pressure and matrix-to-reinforcement ratio on the densification of short-carbon-fiber-reinforced, randomly oriented carbon/carbon-composite. Secondary objectives included determination of the physical and mechanical properties of the resulting composite. The ‘hybrid carbon-fiberreinforced mesophase-pitch-derived carbon-matrix’ composite was fabricated by hot pressing. During hot pressing, pressure was varied from 5 to 20 MPa, and reinforcement wt% from 30 to 70. Densification of all the compacts was carried at low impregnation pressure with phenolic resin. The effect of the impregnation cycles was determined using measurements of microstructure and density. The results showed that effective densification strongly depended on the hot-pressing pressure and reinforcement wt%. Furthermore, results showed that compacts processed at lower hot-pressing pressure, and at higher reinforcement wt%, gained density gradually during three densification cycles and showed the symptoms of further gains with additional densification cycles. In contrast, samples that were hot-pressed at moderate pressure and at moderate reinforcement wt%, achieved maximum density within three densification cycles. Furthermore, examination of microstructure revealed the formation of cracks in samples processed at lower pressure and with low reinforcement wt%.
        4,000원
        17.
        2014.07 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This study highlights a novel method and mechanism for the rapid and effective milling of carbon fibers (CFs) in silicon carbide (SiC) powder, and also the dispersion of CFs in SiC powder. The composite powders were prepared by chopping and exfoliation of CFs, and ball milling of CFs and SiC powder in isopropyl alcohol. A wide range of CFs loading, from 10 to 50 vol%, was studied. The milling of CFs and SiC powder was checked by measuring the average particle size of the composite powders. The dispersivity of CFs in SiC powder was checked through scanning electron microscope. The results show that the usage of exfoliated CF tows resulted in a rapid and effective milling of CFs and SiC powder. The results further show an excellent dispersion of CFs in SiC powder for all CFs loading without any dispersing agent.
        4,000원
        18.
        2012.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        화학합성 농약을 대체하기 위한 친환경 방제법 개발을 위해 1, 2, 4%의 도꼬마리 열매 수용성 추출물을 이용하여 팥바구미 살충력을 실험하였다. 실험한 추출 농도에서 곤충 치사율, 기피성, 산란율과 성충 우화 및 팥의 피해 억제에 효과를 보여 주었다. 4%의 추출물은 처리 후 2일 후에26%의 치사율과 처리 후 3시간에 53.3%의 기피율을 각각 보였다. 또한 4%의 추출물을 팥과 섞었을 때 가장 낮은 산란율(113.7/암컷)과, 성충 우화율이 가장 많이 억제(37.0%)되었고 종자 손상을 가장 적게(42.3%) 받았다. 이러한 결과는 도꼬마리 추출물이 저장곡물을 팥바구미로부터 보호하는 종합적 방제수단으로 사용될 수 있다.
        4,000원
        19.
        2012.06 구독 인증기관 무료, 개인회원 유료
        Understanding climate change is not only complex but also extensive. Humanity has never embarked on such a huge challenge of trans-national scope: a problem that began in the past continues now and will be continuing for a long time in the future. Nepalese have also significantly felt the impact of global climate change. The scenarios of climate change indicate that the increased temperatures will cause snow-melt which will result in floods, droughts, and uneven weather patterns. The impact of such unexpected climate hazards and weather patterns have already been felt and will continue to be felt in Nepal. These climate change-induced hazards and risks particularly threaten the agriculture sector, which results in food insecurity and makes poor and vulnerable people face increasingly unanticipated impacts to their lives and wellbeing. This paper explores the climate vulnerability of the Nepalese in terms of their physical, social, economic and primarily agricultural losses due to the increasing impact of climate change. The paper argues the need for a timely adaptation of measures to maintain an environment suitable for agriculture and for the well-being of the population residing in the area.
        4,200원
        20.
        2012.03 구독 인증기관 무료, 개인회원 유료
        Experiments were conducted in order to assess the healing effect of bee venom (BV) cream on full-thickness skin wounds in rabbits. BV cream was compared with silver sulfadiazine (SS) as a topical medicament against a control on experimentally created full-thickness wounds. Two wounds measuring 2 × 2 cm were created bilaterally (four wounds/rabbit) on the dorsolateral aspect of the trunk of seven New Zealand white rabbits. Wound treatments were evenly distributed on four sites, using a Latin square design. The contact layer of wounds was treated with physiological saline (control), SS cream, and BV cream over a period of 28 days. Assessment of wound healing was based on scab hardness, wound exudates, wound area, unepithelialized granulation tissue, and histopathological findings. Topical application of BV and SS creams to wounds resulted in reduced inflammation, debridement of necrotic tissue, and promoted granulation and epithelialization. Wound healing was faster, with statistical significance in BV and SS treatments, compared to the control (P<0.05). Treatment with BV evoked an anti-inflammation effect in a rabbit model. BV cream produced a wound healing effect similar to that of commercially available SS cream. Anti-inflammation effect as a topical treatment with BV cream appears to be better than that with SS cream. These results suggest that topical application of BV cream may be an alternative treatment for full-thickness skin wounds.
        4,000원
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