• Title/Summary/Keyword: mechanisms

Search Result 13,273, Processing Time 0.045 seconds

An Analysis of the Study Tendency on Rheumatoid Arthritis -Focusing on Domestic Theses for a Degree and Journal Since 2004- (류마토이드 관절염의 연구동향에 대한 소고(小考) -2004년 이후의 국내 학위논문 및 학회지 논문을 중심으로-)

  • Choi, Yong-Hun;Yoon, Il-Ji
    • Journal of Korean Medicine Rehabilitation
    • /
    • v.19 no.2
    • /
    • pp.125-156
    • /
    • 2009
  • Objectives : To research the trend of studies related to rheumatoid arthritis and to indicate the hereafter direction for its study in oriental medicine and its treatment. Methods : I reviewed 75 domestic oriental medical journals, and 50 medical journals about rheumatoid arthritis published after 2004, and comparative analysis was made. And these theses were classified by college, year, field of study, subject. Results : The following are the results of this study. 1. Classified by oriental medical college, Dae-jeon college published the most theses, followed by Dong-guk, Kyung-hee, Se-myung and Dong-shin college. Han-yang college published the most theses among college of medicine. 2. Classified by type of thesis, experimental theses(70 pieces, 94%) showed higher rate than that of clinical theses(4 pieces, 5%) in oriental medical studies. However, in medical studies, clinical theses(34 pieces, 68%) showed higher rate than that of experimental theses(15 pieces, 30%). 3. Analyzed by subject, the most dealt subject in oriental medicine was herb medication, followed by herbal acupuncture, single herb, electroacupuncture, sasang & gene, acupuncture & moxibustion, complex accordingly. The most dealt subject in medical clinical journals was standards of diagnosis & prognosis, followed by medication, gene analysis, pathogenesis, clinical pattern, operative treatment and complication accordingly. 4. In theses related to herb medication, most of the subject was to evaluate anti-inflammatory and immunoregulatory effects of herb medication with geopungseup, jibitong, hwalhyeolgeoer function. The tendency of experimental methods was focusing on understanding anti-inflammatory and immunoregulatory mechanisms through molecular biologic methods by analyzing cytokine and gene. 5. Most of theses related to herbal acupuncture were experimental studies verifying ant-inflammatory and immnoregulatory effects through methods observing change of cytokine and immunoregulatory factors. Regarding remedies for herbal acupuncture, Ulmus davidiana Planch was most preferred, followed by bee venom. 6. In theses related to single herb, Boik-yak was most prefered, followed by Geopungseup-yak and Hwalhyeolgeoer-yak. Regarding methods of research, there were tendency of shifting from methods verifying travail, anti-inflammatory and anti-pyretic effects through a test of behavior, morphometry, serology and temperature measurement of the rectum and the skin into verifying anti-inflammatory and immunoregulatory effects through observing inflammatory cytokine in the joint and cells of spleen. 7. In theses related to electroacupuncture, ST36 and adjuvant were most preferred as acupoints and induced factor. The tendency of experimental methods was turning from verifying mechanism of travail effect to analyzing inflammation and pain inducing factors. 8. Diverse medical clinical studies were published. Subjects such as diagnosis and prognosis, medication, gene analysis, clinical pattern, operational treatment, complication and pathogenesis were published. Especially, studies about standards of early diagnosis, and research on possible parallel medications with methotrexate were actively inquired. 9. Most of theses related to medical experimental studies was about mediators and receptors related to inflammatory induction and osteoclasia mechanism. Also, it was presented blockage of them can be effective on rheumatoid arthritis. Conclusions : The oriental medicine studies have merit in its diversity of treatment, but it clinical studies is lacking compared to experimental studies. Also, more diversity of subjects is necessary. Therefore, complementary measures are needed. Hereafter, oriental medicine research about rheumatoid arthritis needs more clinical research verifying the effectiveness and safety in clinical field. Also, we require oriental medical standard of diagnosis and researches on pathological generation which would make early checkup and prognosis possible.

MODULATION OF INTRACELLULAR pH BY $Na^+/H^+$ EXCHANGER AND $HCO_3^-$ TRANSPORTER IN SALIVARY ACINAR CELLS ($Na^+/H^+$ exchanger와 $HCO_3^-$ transporter에 의한 흰쥐 타액선 선세포내 pH 조절)

  • Park, Dong-Bum;Seo, Jeong-Taeg;Sohn, Heung-Kyu;Lee, Jong-Gap
    • Journal of the korean academy of Pediatric Dentistry
    • /
    • v.25 no.2
    • /
    • pp.352-367
    • /
    • 1998
  • Intracellular pH (pHi) plays an important role in the regulation of cellular processes by influencing the acitivity of various enzymes in cells. Therefore, almost every type of mammalian cell possesses an ability to regulate its pHi. One of the most prominent mechanisms in the regulation of pHi is $Na^+/H^+$ exchanger. This exchanger has been known to be activated when cells are stimulated by the binding of agonist to the muscarinic receptors. Therefore, the aims of this study were to compare the rates of $H^+$ extrusion through $Na^+/H^+$ exchanger before and during muscarinic stimulation and to investigate the possible existence of $HCO_3^-$ transporter which is responsible for the continuous supply of $HCO_3^-$ ion to saliva. Acinar cells were isolated from the rat mandibular salivary glands and loaded with pH-sensitive fluoroprobe, 2', 7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein(BCECF), for 30min at room temperature. Cells were attached onto the coverglass in the perfusion chamber and the changes in pHi were measured on the iverted microscope using spectrofluorometer. 1. By switching the perfusate from $HCO_3^-$-free to $HCO_3^-$-buffered solution, pHi decreased by $0.39{\pm}0.02$ pH units followed by a slow increase at an initial rate of $0.04{\pm}0.007$ pH units/min. The rate of pHi increase was reduced to $0.01{\pm}0.002$ pH units/min by the simultaneous addition of 1 mM amiloride and $100{\mu}M$ DIDS. 2. An addition and removal of $NH_4^+$ caused a decrease in pHi which was followed by an increase in pHi. The increase of pHi was almost completely blocked by 1mM amiloride in $HCO_3^-$-free perfusate which implied that the pHi increase was entired dependent on the activation of $Na^+/H^+$ exchanger in $HCO_3^-$-free condition. 3. An addition of $10{\mu}M$ carbachol increased the initial rate of pHi recovery from $0.16{\pm}0.01$ pH units/min to $0.28{\pm}0.03pH$ units/min. 4. The initial rate of pHi decrease induced by 1mM amiloride was also increased by the exposure of the acinar cells to $10{\mu}M$ carbachol ($0.06{\pm}0.008pH$ unit/min) compared with that obtained before carbachol stimulation ($0.03{\pm}0.004pH$ unit/min). 5. The intracellular buffering capacity ${\beta}1$ was $14.31{\pm}1.82$ at pHi 7.2-7.4 and ${\beta}1$ increased as pHi decreased. 6. The rate of $H^+$ extrusion through $Na^+/H^+$ exchanger was greatly enhanced by the stimulation of the cells with $10{\mu}M$ carbachol and there was an alkaline shift in the activity of the exchanger. 7. An intrusion mechanism of $HCO_3^-$ was identified in rat mandibular salivary acinar cells. Taken all together, I observed 3-fold increase in $Na^+/H^+$ exchanger by the stimulation of the acinar cells with $10{\mu}M$ carbachol at pH 7.25. In addition, I have found an additional mechanism for the regulation of pHi which transported $HCO_3^-$ into the cells.

  • PDF

Relation of Interleukin-10 in Bronchoalveolar Lavage Fluid and Airway Inflammation in Bronchial Asthma (기관지천식에서 기관지폐포세척액내 IL-10과 기도염증정도의 연관성)

  • Lee, Sook-Young;Youn, Hung-Gue;Shin, Youn;Lee, Sang-Haak;Kim, Seok-Chan;Kim, Kan-Hyoung;Moon, Hwa-Sik;Song, Jeong-Sup;Park, Sung-Hak
    • Tuberculosis and Respiratory Diseases
    • /
    • v.46 no.1
    • /
    • pp.44-52
    • /
    • 1999
  • Background : Airway infiltration by inflammatory cells, particularly of eosinophils, is one of the characteristic features of asthma. Several mechanisms for the recruitment of eosinophil is focused on the CD4+ T lymphocyte for the preferential production of Th2-c1erived cytokines. Interleukin-10(IL-10) is identified cytokine with potent antiinflammatory activity. This molecule has been shown to inhibit the release of cytokine from inflammatory cells including Th2 cell, and also to inhibit eosinophil survival. We therefore attempted to determine whether decreased synthesis of IL-10 in the lung of bronchial asthma may contribute to inflammation that is characteristics of this dease. Method: Subjects were patients with bronchial asthma(n=23) and normal controls(n=11). IL-10 produced from peripheral mononuclear cell(PBMC) and in bronchoalveolar lavage(BAL) fluid was measured by ELISA method. Degree of bronchial inflammation was assessed by total cell counts and eosinophil percents in BAL fluid, eosinophil infiltration on bronchial biopsy tissue and $PC_{20}$ for methacholine. Results: The IL-10 level produced by PBMC and in BAL fluid from patient with bronchial asthma were not different with normal controls(respectively, $901.6\pm220.4$ pg/ml, $810.9\pm290.8$ pg/ml for PBMC, $24.5\pm9.5$ pg/mL $30.5\pm13.5$ pg/ml for BAL fluid p>0.05). There were significant negative correlation between IL-10 in BAL fluid and eosinophil percents in BAL fluid or degree of eosinophil infiltration in bronchial biopsy (respectively r=-0.522, r=-0.4486 p<0.05). However there was no difference of IL-10 level according to $PC_{20}$ for methacholine. There were no correlation between IL-10 production by PBMC and peripheral blood eosinophil counts or serum eosinophilic cationic protein levels(respectively r=0.1146, r=0.0769 p>0.05). Conclusion: These observation suggest that IL-10 may participate but not acts the crucial role in regulation of the airway inflammation in bronchial asthma.

  • PDF

Clinical Investigation of Women with Asthma Worsened During Pregnancy (임신 중 천식의 악화로 내원한 환자의 임상적 고찰)

  • Kwon, Young-Hwan;Kim, Kyung-Kyu;Jung, Hye-Cheol;Lee, Sung-Yong;Kim, Je-Hyeong;Lee, So-Ra;Lee, Sang-Yeub;Lee, Sin-Hyeong;Cho, Jae-Yun;Shim, Jae-Jeong;Kang, Kyung-Ho;Yoo, Se-Hwa;In, Kwang-Ho
    • Tuberculosis and Respiratory Diseases
    • /
    • v.46 no.4
    • /
    • pp.548-554
    • /
    • 1999
  • Background : Asthma is the most common respiratory crisis encountered in clinical practice, occurring in up to 4% of all pregnancies. Pregnancy often appears to alter the course of asthma. But the mechanisms responsible for variable changes in the asthma course during pregnancy remain unknown. Poor control and exacerbations of asthma during pregnancy may result in serious maternal and fetal complications. To investigate the course of asthma during pregnancy in korean women, we did a retrograde study of 27 pregnant women who had been admitted to Korea University Hospital for asthma worsened. Method: Twenty seven pregnant women who had been visited to Korea University Hospital for asthma worsened were enrolled in our retrospective study. We reviewed medical recordings and interviewed patients with asthma. Results: Twenty seven pregnant women with asthma were evaluated, and 25 patients were enrolled to our study. Two patients experienced abortions at 6 weeks and 25 weeks gestation, respectively. The period of asthma worsened was commonly during weeks 20 to 28 of gestation. And all patients wosened were improved during the last 4 weeks of pregnancy. Twenty(80%) of 25 women whose asthma worsened during pregnancy reverted toward their prepregnancy status after delivery(p<0.002). The causes of asthma worsened during pregnancy are reduction or even complete cessaton of medication due to fears about its safety(40%), worsening after upper respiratory infection (28%), and unknown(32%). There were no adverse perinatal outcomes in 25 pregnant asthma subjects. Conclusions: A major problem of therapy for asthma during pregnancy is reduction or even complete cessation of medication due to fears of fetal effects. Therefore, maternal education and optimal clinical and pharmacologic management is necessary to mitigate maternal and fetal complications.

  • PDF

The Role of Interleukin 8 and NF(nuclear factor)-κB in Rhinovirus-Induced Airway Inflammation (Rhinovirus 유발성 기도염증반응에서 Interleukin-8과 전사인자 NF(nuclear factor)-κB의 역할에 대한 연구)

  • Yoon, Ho Joo;Kim, Mi Ok;Sohn, Jang Won;Kim, Jung Mogg;Shin, Dong Ho;Park, Sung Soo
    • Tuberculosis and Respiratory Diseases
    • /
    • v.54 no.1
    • /
    • pp.104-113
    • /
    • 2003
  • Background : Rhinovirus(RV) infections frequently trigger dyspnea and paroxysmal cough in adult patients with asthma and are the most prevalent cause of the common cold. However, the mechanisms of a RV-induced airway inflammation is unclear. Since the RV does not directly destroy the airway epithelium, it is presumed that the immune response to the RV contributes to the pathogenesis of the respiratory symptoms. In order to test this hypothesis, this study characterized the time-sequenced alterations in interleukin(IL)-8 elaboration from the human bronchial epithelial cells and evaluated the role of NF(nuclear factor)-${\kappa}B$ in the RV-induced IL-8 production by pretreating the inhibitors of NF-${\kappa}B$ activation. Methods : The ability of RV-infected human bronchial epithelial cells and BEAS-2B cells to produce the IL-8 was compared with the controls. This study infected BEAS-2B cells with the RV14 obtained from the American Type Culture Collection. The supernatants were harvested from the RV infected BEAS-2B cells and the controls at 2hr, 4hr, 6hr, 12hr, 24hr, 48hr from the inoculation time. This study measured the IL-8 concentration using the ELISA kits. In order to elucidate the role of NF-${\kappa}B$ in the RV-induced IL-8 production, the effect of the NF-${\kappa}B$ inhibitors was evaluated on RV-induced IL-8 production. Results: The BEAS-2B cells produced small amounts of IL-8 that accumulated slowly with time in the culture. The RV was a potent stimulator of the IL-8 proteins production by BEAS-2B human bronchial epithelial cells. Antioxidants, N-acetyl-L-cysteine(NAC),\ and pyrrolidine dithiocarbamate(PDTC), blocked the IL-8 elaboration by the RV-infected BEAS-2B cells, which was dose-dependent, but N-Tosyl-L-phenylalanine chloromethyl ketone(TPCK) did not. Conclusion: Some antioxidants inhibited the RV-induced IL-8 production by blocking the NF-${\kappa}B$, which may have a therapeutic potential in asthma.

Expression of UT-A in Rat Kidney: Ultrastructural Immunocytochemistry (흰쥐 콩팥에서 요소운반체-A의 발현: 미세구조적 면역세포화학법)

  • Lim, Sun-Woo;Jung, Ju-Young;Kim, Wan-Young;Han, Ki-Hwan;Cha, Jung-Ho;Chung, Jin-Woong;Kim, Jin
    • Applied Microscopy
    • /
    • v.32 no.2
    • /
    • pp.91-105
    • /
    • 2002
  • Urea transport in the kidney is mediated by a family of transporter proteins that includes renal urea transporters (UT-A) and erythrocyte urea transporters (UT-B). The cDNA of five isoforms of rat UT-A, UTA1, UT-A2, UT-A3, UT-A4, and UT-A5 have been cloned. The purpose of this study was to examine the expression of UT-A (L194), which marked UT-A1, UT-A2 and UT-A4. Male Sprague-Dawley rats, weighing approximately 200 g, were divided into three group: control rats had free access to water, dehydrated rats were deprived of water for 3 d, and water loaded rats had free access to 3% sucrose water for 3 d before being killed. The kidneys were preserved by in vivo perfusion through the abdominal aorta with the 2% paraformaldehyde-lysine- periodate (PLP) or 8% paraformaldehyde solution for 10 min. The sections were processed for immunohistochemical studies using pre-embedding immunoperoxidase method and immunogold method. In the normal rat kidney, UT-A1 was expressed intensely in the cytoplasm of the inner medullary collecting duct (IMCD) cell and UT-A2 was expressed on the plasma membrane of the terminal portion of the shortloop descending thin limb (DTL) cells (type I epithelium) and of the long-loop DTL cells (type II epithelium) in the initial part of the inner medulla. Immunoreactivity for UT-A1 in the IMCD cells, was decreased in dehydrated animals whereas strongly increased in water loaded animals compared with control animals. In the short-loop DTL, immunoreactivity for UT-A2 was increased in intensity in both dehydrated and water loaded groups. However, in the long-loop DTL of the outer part of the inner medulla, immunoreactivity for UT-A2 was markedly increase in intensity in dehydrated group, but not in water loaded group. In conclusion, in the rat kidney, UT-A1 is located in the cytoplasm of IMCD cells, whereas UT-A2 is located in the plasma membrane of both the short-and long-loop DTL cells. Immunohistochemistry studies revealed that UT-A1 and UT-A2 may have a different role in urea transport and are regulated by different mechanisms.

Targeted Therapies and Radiation for the Treatment of Head and Neck Cancer (두경부 암의 표적 지향적 방사선 치료)

  • Kim, Gwi-Eon
    • Radiation Oncology Journal
    • /
    • v.22 no.2
    • /
    • pp.77-90
    • /
    • 2004
  • Purpose: The purpose of this review Is to provide an update on novel radiation treatments for head and neck cancer Recent Findings: Despite the remarkable advances In chemotherapy and radiotherapy techniques, the management of advanced head and neck cancer remains challenging. Epidermal growth factor receptor (EGFR) Is an appealing target for novel therapies In head and neck cancer because not only EGFR activation stimulates many important signaling pathways associated with cancer development and progression, and importantly, resistance to radiation. Furthermore, EGFR overexpression Is known to be portended for a worse outcome in patients with advanced head and neck cancer. Two categories of compounds designed to abrogate EGFR signaling, such as monoclonal antibodies (Cetuxlmab) and tyrosine kinase inhibitors (ZD1839 and 051-774) have been assessed and have been most extensively studied In preclinical models and clinical trials. Additional TKIs In clinical trials include a reversible agent, Cl-1033, which blocks activation of all erbB receptors. Encouraging preclinical data for head and neck cancers resulted In rapid translation Into the clinic. Results from Initial clinical trials show rather surprisingly that only minority of patients benefited from EGFR inhibition as monotherapy or In combination with chemotherapy. In this review, we begin with a brief summary of erbB- mediated signal transduction. Subsequently, we present data on prognostic-predictive value of erbB receptor expression in HNC followed by preclinlcal and clinical data on the role of EGFR antagonists alone or in combination with radiation In the treatment of HNC. Finally, we discuss the emerging thoughts on resistance to EGFR biockade and efforts In the development of multiple-targeted therapy for combination with chemotherapy or radiation. Current challenges for investigators are to determine (1 ) who will benefit from targeted agents and which agents are most appropriate to combine with radiation and/or chemotherapy, (2) how to sequence these agents with radiation and/or cytotoxlc compounds, (3) reliable markers for patient selection and verification of effective blockade of signaling in vivo, and (4) mechanisms behind intrinsic or acquired resistance to targeted agents to facilitate rational development of multi-targeted therapy, Other molecuiar-targeted approaches In head and neck cancer were briefly described, Including angloenesis Inhibitors, farnesyl transferase inhibitors, cell cycle regulators, and gene therapy Summary: Novel targeted theraples are highly appealing in advanced head and neck cancer, and the most premising strategy to use them Is a matter of intense Investigation.

The Modulation of Radiosensitivity by Combined Treatment of Selective COX-2 Inhibitor, NS 398 and EGF Receptor Blocker AG 1478 in HeLa Cell Line (선택적 COX-2 억제제 NS 398과 EGF 수용체 차단제 AG 1478의 복합투여가 HeLa 세포주의 방사선 감수성에 미치는 영향)

  • Youn Seon Min;Oh Young Kee;Kim Joo Heon;Park Mi Ja;Seong In Ock;Kang Kimun;Chai Gyuyong
    • Radiation Oncology Journal
    • /
    • v.23 no.1
    • /
    • pp.51-60
    • /
    • 2005
  • Purpose : Selective inhibition of multiple molecular targets may improve the antitumor activity of radiation. Two specific inhibitors of selective cyclooxygenase-2 (COX-2) and epidermal growth factor receptor (EGFR) were combined with radiation on the HeLa cell line. To investigate cooperative mechanism with selective COX-2 inhibitor and EGFR blocker, in vitro experiments were done. Materials and Methods : Antitumor effect was obtained by growth inhibition and apoptosis analysis by annexin V-Flous method. Radiation modulation effects were determined by the clonogenic cell survival assay. Surviving fractions at 2 Gy ($SF_2$) and dose enhancement ratio at a surviving fraction of 0.25 were evaluated. To investigate the mechanism of the modulation of radiosensitivity, the cell cycle analyses were done by flow cytometry. The bcl-2 and bax expressions were analyzed by western blot. Results : A cooperative effect were observed on the apoptosis of the HeLa ceil line when combination of the two drugs, AG 1478 and NS 398 with radiation at the lowest doses, apoptosis of $22.70\%$ compare with combination of the one drug with radiation, apoptosis of $8.49\%$. In cell cycle analysis, accumulation of cell on $G_0/G_l$ phase and decrement of S phase fraction was observed from 24 hours to 72 hours after treatment with radiation, AG 1478 and NS 398. The combination of NS 398 and AG 1478 enhanced radiosensitivity on a concentration-dependent manner in HeLa cells with dose enhancement ratios of 3.00 and $SF_2$ of 0.12 but the combination of one drug with radiation was not enhanced radlosensitivity with dose enhancement ratios of 1.12 and SF2 of 0.68 (p=0.005). The expression levels of bcl-2 and bax were reduced when combined with AG 1478 and NS 398. Conclusion : Our results indicate that the selective COX-2 inhibitor and EGFR blocker combined with radiation have potential additive or cooperative effects on radiation treatment and may act through various mechanisms including direct inhibition of tumor cell proliferation, suppression of tumor cell cycle progression and inhibition of anti-apoptotic proteins.

The effect of air quality and humidity on aged characteristics of beeswax-treated paper during artificial aging (인공열화 시 공기질 및 습도가 밀랍지의 열화에 미치는 영향)

  • Yang, Eun Jeong;Choi, Kyoung Hwa;Kang, Yeong Seok;Cho, Jung hye;Jeong, Hye Young
    • 보존과학연구
    • /
    • s.33
    • /
    • pp.45-55
    • /
    • 2012
  • A beeswax-treated paper has no air permeability but has the water repellency compared with a general Hanji. Because of these properties, the differences of the aging factors and mechanisms between the outer partition of beeswax-treated paper that is affected by the surrounding conservation environment and the inner partition of it that is not affected are bigger than general books. In this research, we analyzed and compared the aging characteristics through the accelerated aging of the beeswax-treated paper by some air and humidity conditions. The results of the physical and optical analysis after the artificial aging, it was shown that the oxygen accelerates the aging of the beeswax-treated paper and the condition with the humidity 50% RH is more stable than the condition with the humidity 0% RH. The results of the CG/MS analysis that was conducted to figure out the decomposition charateristics of the beeswax according to the air quality and the humidity, a low molecular weight compound that the number of carbon is C9-C20 including a fatty acid such as a palmitic acid was increased as the aging was progressed. However, under the same environment, a compound that the number of carbon is C21-C36 including a hydrocarbon and a aliphatic alcohol and a high molecular weight compound that the number of carbon is more than C34 including a wax ester were decreased. A rate of change according to the air quality and the humidity was similar to the beeswax-treated papers.

  • PDF

A Study on the Recovery of Radiation Hardening of PWR Pessure Vessel Steel Using Michrohardness and Positron Annihilation (미세경도와 양전자 소멸을 이용한 PWR 압력용기강의 조사 경화 회복에 관한 연구)

  • Garl, Seong-Je;Yoon, Young-Ku;Park, Soon-Pil;Park, Yong-Ki
    • Nuclear Engineering and Technology
    • /
    • v.22 no.4
    • /
    • pp.337-350
    • /
    • 1990
  • A post-irradiation annealing study was conducted with use of reactor pressure vessel(RPV) steel A533B Cl.1 base metal irradiated to a dose of 4.84$\times$10$^{18}$ n/$\textrm{cm}^2$ at about 38$0^{\circ}C$. Microhardness and positron annihilation (PA) methods were used to obtain better understanding of the recovery of radiation hardening. Isochronal anneal experiments indicated that two recovery processes occur during annealing of irradiated specimens. The first recovery process occurs in the temperature range of 280-3O5$^{\circ}C$, Michrohardness and positron annihilation (PA) methods were used to obtain better understanding of the recovery of radiation hardening. Isochronal anneal experiments indicated that two recovery processes occur during annealing of irradiated specimens. The first recovery process occurrs in the temperature range of 280-305$^{\circ}C$. The variations of Ip, Iw and R parameters indicated that the formation of vacancy clusters by vacancy agglomeration and the annihilation of monovacancies are the first recovery process. The second recovery process occurs in the range of 405-49$0^{\circ}C$ and positron annihilation parameters measured indicated that the dissolution of carbon atoms decorated around vacancy-type defects and possible precipitates, and the annihilation of monovacancies give rise to the second recovery process. It was further indicated that radiation anneal hardening (RAH) in the range of 305-405$^{\circ}C$ between the temperature ranges for the two processes occurs due to the formation of carbon-decorated vacancy clusters and precipitates. The activation energies, orders of reaction and other characteristics of recovery processes were determined by the Meechan-Brinkman method. The activation energy for the first recovery process was determined as 1.76 eV and that for the second recovery process as 2.00eV. These values are lower than those obtained by other workers. This difference may be attributed to the lower copper content of the RPV steel used in the present study. The order of reaction for the first recovery process was determined as 1.78, while that for the second recovery process as 1.67 Non-integer orders of reaction for recovery processes seem to be attributed to the fact that several mechanisms for the first order and the second order of reaction are compounded in one process. This result also supports for the above conclusions from measurements of PA parameters.

  • PDF