The effects of vanilloid analogues structurally related to capsaicin on the transient receptor potential vanilloid 1 channel

Transient receptor potential vanilloid 1 (TRPV1) is known as a receptor of capsaicin, a spicy ingredient of chili peppers. It is also sensitive to a variety of pungent compounds and is involved in nociception. Here, we focused on the structural characteristics of capsaicin, and investigated whether vanillylmanderic acid (VMA), vanillic acid (VAcid), vanillyl alcohol (VAlc), vanillyl butyl ether (VBE), and vanillin, containing a vanillyl skeleton similar to capsaicin, affected the TRPV1 activities. For detection of TRPV1 activity, intracellular Ca²⁺ concentration ([Ca²⁺]_i) was measured in HEK 293 cells heterologously expressing mouse TRPV1 (mTRPV1-HEK) and in mouse sensory neurons. Except for vanillin, four vanilloid analogues dose-dependently increased [Ca²⁺]_i in mTRPV1-HEK. The solutions that dissolved VMA, VAcid and vanillin at high concentrations were acidic, whereas those of VAlc and VBE were neutral. Neutralized VAcid evoked [Ca²⁺]_i increases but neutralized VMA did not. Mutation of capsaicin-sensing sites diminished [Ca²⁺]_i responses to VAcid, VAlc and VBE. VAcid, VMA, and vanillin suppressed the activation of TRPV1 induced by capsaicin. VAcid and VMA also inhibited the acid-induced TRPV1 activation. In sensory neurons, VMA diminished TRPV1 activation by capsaicin or acids. The present data indicate that these structural characteristics of chemical compounds on TRPV1 may provide strategies for the development of novel analgesic drugs targeting nociceptive TRPV1.

Intraventricular pressure gradient: a promising tool to predict the post-infarction chronic congestive heart failure in rats

Funding Acknowledgements

Type of funding sources: None.

Background/Introduction: Congestive heart failure (CHF), the main reason for morbidity and mortality, is considered a serious consequence of myocardial infarction (MI). The use of left ventricular end-diastolic pressure (LVEDP) as a chief indicator of CHF becomes limited because of the possible impairment of cardiac function and induced aortic valve damage during its recording. Echocardiography is the gold standard approach to diagnose structural myocardial dysfunction. However, its ability to predict chronic CHF following MI is still limited. Recently, intraventricular pressure gradient (IVPG) was presented as a non-invasive, highly sensitive preload-independent diastolic function parameter to assess cardiac function, especially during cardiomyopathy. However, there have not been any investigations demonstrating the feasibility of IVPG in the evaluation of post-infarction chronic CHF.

Purpose

This study aimed to investigate the utility of IVPG to assess the heart function in a rat model with chronic CHF following MI with evaluating its capacity to predict these changes.

Methods

Fifty male rats were included. MI was induced via ligation of the left anterior descending artery (LAD) at the level of the atrioventricular junction (MI animals, n = 35). Sham animals were subjected to the same left thoracotomy procedure without LAD ligation (Sham animals, n = 15). Transthoracic conventional echocardiography and colour M-mode echocardiography (CMME) for IVPG were performed in all animals 6 months post-surgery. The next day, animals were anesthetized, ventilated, and euthanized after the recording of hemodynamics. The heart weight, and lung and liver wet-to-dry weight ratios were recorded. J-tree cluster-analysis was performed based on ten echocardiographic variables indicative of CHF.

Results

Based on the cluster analysis, animals were joined into two clusters; CHF+ (n = 22) and named MI/HF+, and CHF- (n = 28) that was joined from sham (n = 15), and MI/HF- (n = 13). MI/HF+ presented the most severe anatomical and echocardiographic changes indicative of CHF with significant reduction of all IVPG indices and impairment of the hemodynamics. The IVPG indices were significantly (P< 0.0001) correlated with the anatomical and echocardiographic findings, LVDP, LVEDP, HR, -dP/dtmin, and Tau. Meanwhile, LVSP was only significantly correlated with apical IVPG (R = 0.677, P = 0.022). dP/dtmax was significantly correlated with total IVPG, basal IVPG, and apical IVPG (R = 0.797, P = 0.017, R = 0.724, P = 0.003, and R = 0.652, P = 0.026 ; respectively). Moreover, total, basal, mid-to-apical, mid-, and apical IVPG were significant (P< 0.0001) predictors of chronic CHF following MI.

Conclusion

Compared to the structural, and functional indices of conventional echocardiography, IVPG derived from CMME could provide a substantial non-invasive tool to diagnose and predict CHF after long-term MI.

Novel method of diastolic stress echocardiography during bottle-feeding for infants with congenital heart disease

Funding Acknowledgements

Type of funding sources: None.

Background

Recent studies have demonstrated the utility of diastolic stress echocardiography in evaluating diastolic dysfunction during exercise in adults. However, there have been no such reports in infants. This study determined whether measuring cardiac function using echocardiography during bottle feeding is a valid method of stress testing in infants with congenital heart disease.

Methods

The study population comprised 25 infants with congenital heart disease (Table 1). Echocardiographic measurements of the infants were taken during and after bottle feeding (Figure 1A). Active feeding (AF) was defined as the start of feeding during which the heart rate started increasing. End of feeding (EF) was defined as the time of completion of feeding during which the heart rate slowed down. The 25 infants were divided into two groups according to brain natriuretic peptide levels: less than 50 pg/ml (low group) and more than 50 pg/ml (high group). Cardiac function was compared between the groups using 2D speckle tracking analysis, and intraventricular pressure differences (IVPD) via color M-mode Doppler (Figures 1B and 1C) and 2D echocardiography. We compared the fractional change (FC%), defined as (AF and EF measurements)/EF measurements, between the two groups.

Results

Heart rate increased AF comparing with EF, significantly in both groups, the low group from 162 to 139 bpm; the high group from 152 to 140 bpm. The FC_IVPD was higher in the low group than in the high group (Figure.2). There were negative correlations between brain natriuretic peptide levels and the FC_IVPD (Figure 3). There were 4 cases were performed the intra-cardiac repair (ICR). In 2 cases, VSD and right ventricular outflow tract obstruction (RVOTO) velocity were increased during feeding. Indication of ICR, VSD case was aortic regurgitation with aortic cusp prolapse, TOF case was RVOTO. In VSD peak velocity in 2 cases did not increase during feeding (Table2). Indication of

ICR, two VSD cases were moderate left to right shunt, or pulmonary hypertension.

Conclusions

Our findings indicate that stress echocardiography during bottle-feeding might be a substitute for diastolic stress echocardiography in infants. The VSD or RVOT peak velocity, and FC% in IVP D and IVPG are sensitive markers for cardiac function in infants with congenital heart disease. Abstract Table1  Abstract Figure.

Assessment of anthracycline-induced cardiotoxicity in patients with childhood cancer survivor for long-term follow-up

Funding Acknowledgements

Type of funding sources: None.

Background

 Anthracycline cardiotoxicity is an important prognostic determinant in childhood cancer survivors (CCSs). That has been reported to improve with early therapeutic intervention, and because it is dose-dependent and progressive, early diagnosis and long-term follow-up are important. In adult survivors of cancer, the longitudinal strain (LS) is useful as a sensitive index of cardiac function. In childhood cancer survivors, strain abnormalities are also observed at both short-term and long-term follow-up. Global longitudinal strain (GLS) abnormalities are common during or early after chemotherapy, whereas changes in global circumferential strain (GCS) are more significant and consistent on long-term follow-up.

Purpose

 In this study, we aimed to conduct a cross-sectional study using strain analysis in childhood cancer survivors of a wide age range to clarify the mode of progression of anthracycline-induced cardiotoxicity and to identify useful indicators for long-term follow-up.

Methods

 In total, 116 patients (median age: 15.5 [range: 4.7-40.2] years) with childhood cancer who had passed at least 1 year after chemotherapy with anthracycline, and 116 control patients of similar age. Strain measurements were assessed for longitudinal strain (LS) and circumferential strain at the apical, papillary and basal levels using speckle tracking imaging. Estimated value at 5, 15, 25 and 35 years old were mathematically calculated.

Results

 Results were shown in tables and figures. Most of conventional echocardiographic parameters were not significantly different between CCCs and controls. LS, papillary CS and basal CS in CCCs decreased compared to normal controls at all age. The difference of estimated value between CCCs and normal controls in LS at all age were relatively constant. However, those in basal CS tended to increase with aging. Furthermore, basal CS in CCCs decreased with aging (r = 0.212, p < 0.001) and the duration after completion of anthracycline treatment (r = -0.244, p < 0.008).

Conclusions

 In childhood cancer survivors, strain analysis is a more sensitive indicators of cardiac function than conventional parameters. In addition, basal CS may decrease most markedly over time and could be useful indicator in long-term follow-up. Longitudinal studies should be conducted in the future to improve the accuracy of predicting anthracycline cardiotoxicity. These are new findings regarding the decline in cardiac function in childhood cancer survivors. Abstract Figure. Relationship between age and strains  Abstract Figure. Estimated values for each age group

Air pollution and airborne infection with mycobacterial bioaerosols: a potential attribution of soot

Atmospheric pollutants are hypothesized to enhance the viability of airborne microbes by preventing them from degradation processes, thereby enhancing their atmospheric survival. In this study, Mycobacterium smegmatis is used as a model airborne bacteria, and different amounts of soot particles are employed as model air pollutants. The toxic effects of soot on aerosolized M. smegmatis are first evaluated and excluded by introducing them separately into a chamber, being sampled on a filter, and then cultured and counted. Secondly, the bacteria-soot mixture is exposed to UV with different durations and then cultured for bacterial viability evaluations. The results show that under UV exposure, the survival rates of the low-, medium-, and high-soot groups are 1.1 (±0.8) %, 70.9 (±4.3) %, and 61.0 (±17.6) %, respectively. This evidence significantly enhanced survival rates by soot at all UV exposures, though the combinations of UV exposure and soot amounts revealed a changing pattern of survival rates. The possible influence by direct and indirect effects of UV-damaging mechanisms is proposed. This study indicates the soot-induced survival rate enhancements of M. smegmatis under UV stress conditions, representing the possible relations between air pollution and the extended pathogenic viability and, therefore, increased airborne infection probability.

Development of a human heart-on-a-chip model using induced pluripotent stem cells, fibroblasts and endothelial cells

Background

The use of animal models in cardiovascular research is associated with two serious, intrinsic problems: inaccuracy in the extrapolation of data obtained from animals such as rodents due to different cardiac physiology and animal ethics.

Purpose

To develop an artificial human heart model for cardiovascular research using organ-on-a-chip technology and human cells

Methods

Organ chips made of silicone (polydimethylsiloxane) that have two microfluidic channels, a top channel and a bottom channel, separated by a 50-μm thick membrane with 7-μm pores hexagonally packed at 40-μm intervals (Figure 1), were used in this study.

We seeded 10,000 human umbilical vein endothelial cells on the membrane surface in the bottom channel to mimic the vasculature. Next, we seeded a mixture of 100,000 human-induced pluripotent stem cells (hiPSCs) and 50,000 human gingival fibroblasts on the membrane surface in the top channel (Figure 1). Human gingival fibroblasts facilitate cardiac differentiation of hiPSCs [1]. We performed the cardiac differentiation of hiPSCs using a previously described protocol [1]. Culture medium was perfused at a constant rate of 60 μl/h to maintain the culture.

Results

We observed spontaneous contraction of hiPSC-derived cardiomyocytes 20–26 days after the start of the differentiation protocol. Simultaneously, we conducted live intracellular calcium imaging using a fluorogenic calcium-sensitive dye, Cal-520 AM (5 μM in the culture medium). hiPSC-derived cardiomyocytes exhibited a periodic, coordinated pattern of calcium influx synchronised with their contraction under fluorescence microscopy (Figure 2A). Moreover, we found that the β-adrenergic agonist noradrenaline elevated the heart rate of hiPSC-derived cardiomyocytes on the organ chips in a dose-dependent manner (Figures 2A, B).

After observing the contraction and intracellular calcium influx of hiPSC-derived cardiomyocytes, we performed immunocytochemistry. Confocal microscopy indicated that the fluorescent signal obtained from anti-cardiac troponin T antibody staining in the top channel exhibited a typical striated pattern with 1.56±0.12-μm interval that reflected sarcomere structure (Figure 2C, yellow). Moreover, the fluorescent signal obtained from anti-CD31 antibody staining in the bottom channel exhibited a typical pattern at the boundary between cells, which is expected at the cell–cell junction of endothelial cells.

Conclusion

We developed a human heart-on-a-chip model that was confirmed by the functional response to noradrenaline and the histological evidence of sarcomere structure and vasculature, with a capability of live imaging. We expect that this model would be useful for examining the physiological function and for the pharmacological analysis of not only the normal heart but also the heart that reflects specific patient's pathophysiology using patient-derived hiPSCs.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Japan Society for the Promotion of Science Figure 1Figure 2

Cardiac function in fetal and infants born to mothers with gestational diabetes

Background

The intraventricular pressure differences (IVPD) IVPD using color M-mode is a specific marker in infants of mothers with gestational diabetes mellitus (GDM). (Circulation R 2019, 378–388).

Purpose

This study investigated the myocardial performance of fetuses in mothers with GDM under the new GDM definition.

Method

The study population comprised of 27 mothers with GDM and the fetus. Women with GDM were defined as those with a glucose metabolism abnormality that existed before or began during the current pregnancy and was diagnosed using OGTTs. The 5 mothers with type 1 or type 2 DM were receiving insulin before their pregnancy. Fetal echo measurements were performed about median gestational age 35 weeks. The primary outcomes were comparisons of the fetal myocardial performance of GDM with insulin administration and without administration using echocardiography with IVPD, and IVPG. The secondary outcome has investigated the relationships between echocardiography parameters, IVPD, and IVPG, and maternal factors. For all statistical analyses, P<0.05 was considered significant.

Result

In the insulin group was higher RV output (Fig. 2A). Maternal max HbA1c was observed to have a positive correlation with fetal RV output, significantly (Fig. 2B). Maternal max fasting blood glucose was observed to have a negative correlation with the Total, Basal and Mid to apical IVPD, significantly, respectively. Serial change of LV Total IVPD from fetal to after birth shown in Slide. In both groups, LV Total IVPD was increasing from fetal and after birth significantly.

Conclusion

The mechanism associated with the favorable systolic and diastolic performances in IGDMs is suggested to involve metabolic adaptations in the heart. In diabetic mice, these adaptations seem to prevent the heart from failing during conditions of pressure overload, suggesting a restoration of the balance between glucose and fatty acid utilization is beneficial for cardiac function. In fetal LV and RV-IVPD might be interacted the mother's blood sugar control. These indexes can predict the sensitive fetal and infant's cardiac dysfunction for GDM.

Funding Acknowledgement

Type of funding sources: None.

P–145 usefulness of morphokinetic data to predict pregnancy rates of day–6 blastocyst transfers

Study question

Can a scoring model based on morphokinetic data developed to predict pregnancy rates of day–5 blastocyst transfers (KIDSCORE™D5) predict pregnancy rates of day–6 blastocyst transfers?

Summary answer

KIDSCORE™D5 was able to predict the clinical pregnancy rates of embryo transfers done on day 6 with an area under the curve (AUC) of 0.72.

What is known already

KIDSCORE™D5 is a scoring model based on morphokinetic data developed to predict the pregnancy rates of day–5 blastocysts. In 2019, Regnier et al. reported that the AUC of KIDSCORE™D5 for predicting clinical pregnancy rates of day–5 blastocyst transfers was 0.6. However, as KIDSCORE™D5 is constructed based on morphological characteristics and developmental dynamics of day–5 blastocysts, it is unclear whether KIDSCORE™D5 can predict pregnancy rates of day–6 blastocyst transfers. Since there are many cases of day–6 blastocyst transfers, it is important to know if KIDSCORE™D5 can predict pregnancy rates of day–6 blastocyst transfers.

Study design, size, duration

This retrospective single-center study, which included 162 day–5 and 72 day–6 blastocyst transfers, respectively, was conducted at Takahashi Women’s clinic from January to December 2019. Blastocysts derived from 146 patients who underwent intracytoplasmic sperm injection. All blastocysts were cryopreserved and were transferred singly.

Participants/materials, setting, methods

We used EmbryoScope+™ (Vitrolife) for in-vitro culture and calculated KIDSCORE™D5 (ver.3) using Embryoviewer™ (Vitrolife). Blastocyst scoring was done from 1.0 to 9.9. Clinical pregnancy was defined as the presence of a gestational sac confirmed by transvaginal ultrasonography. Statistical analysis was performed with JMP Pro 15.00 (SAS). The relationship between KIDSCORE™D5 and clinical pregnancy was evaluated by the AUC using ROC curve analysis and multivariate analysis adjusted for patient age.

Main results and the role of chance

The mean KIDSCORE™D5 of day–5 and day–6 blastocysts was 7.1±1.7 and 3.7±1.5, respectively. KIDSCORE™D5 of day–6 blastocysts was significantly lower than that of day–5 blastocysts (p < 0.0001, Wilcoxon test). ROC curve analysis showed that the KIDSCORE™D5 could predict clinical pregnancy rates with an AUC of 0.62 for day–5 blastocysts and 0.72 for day–6 blastocysts. The cut-off values for KIDSCORE™D5 were 5.7 and 4.9 for day–5 and day–6 blastocysts, respectively. Blastocysts above the cut off value on both day–5 and day–6 had a significantly higher pregnancy rate than those below the cut off value (day–5: 61.9% vs. 33.3%(p = 0.0023), day–6: 47.4% vs. 7.6%(p = 0.0003)). Multivariate analysis adjusted for patient age showed that KIDSCORE™D5 correlated with clinical pregnancy rates of days 5 and 6 of blastocyst transfer with AUCs of 0.66 and 0.73, respectively.

Limitations, reasons for caution

This study had a small sample size, and it was a retrospective single-center study. In addition, the relationship between KIDSCORE™D5 and clinical pregnancy rates may vary among facilities. Therefore, a prospective multicenter validation is necessary.

Wider implications of the findings: Our study results indicated that KIDSCORE™D5 predicted clinical pregnancy and that morphokinetic parameters related to clinical pregnancy were similar between day–5 and day–6 blastocysts. Hence, morphokinetic evaluation can serve as a criterion for deciding which of multiple day–6 blastocysts can be transferred.

Trial registration number

Not applicable

Multi-Instrument Characterization of Magnetospheric Cold Plasma Dynamics in the June 22, 2015 Geomagnetic Storm

We present a comparison of magnetospheric plasma mass/electron density observations during an 11-day interval which includes the geomagnetic storm of June 22, 2015. For this study we used: Equatorial plasma mass density derived from geomagnetic field line resonances (FLRs) detected by Van Allen Probes and at the ground-based magnetometer networks EMMA and CARISMA; in situ electron density inferred by the Neural-network-based Upper hybrid Resonance Determination algorithm applied to plasma wave Van Allen Probes measurements. The combined observations at L ∼ 4, MLT ∼ 16 of the two longitudinally separated magnetometer networks show a temporal pattern very similar to that of the in situ observations: A density decrease by an order of magnitude about 1 day after the Dst minimum, a partial recovery a few hours later, and a new strong decrease soon after. The observations are consistent with the position of the measurement points with respect to the plasmasphere boundary as derived by a plasmapause test particle simulation. A comparison between plasma mass densities derived from ground and in situ FLR observations during favorable conjunctions shows a good agreement. We find however, for L < ∼3, the spacecraft measurements to be higher than the corresponding ground observations with increasing deviation with decreasing L, which might be related to the rapid outbound spacecraft motion in that region. A statistical analysis of the average ion mass using simultaneous spacecraft measurements of mass and electron density indicates values close to 1 amu in plasmasphere and higher values (∼2-3 amu) in plasmatrough.

Inhibitory effect of polysulfide, an endogenous sulfur compound, on oxidative stress-induced TRPA1 activation

Polysulfide (PS), an endogenous sulfur compound, generated by oxidation of hydrogen sulfide, has a stimulatory action on the nociceptive TRPA1 channel. TRPA1 is also activated by reactive oxygen species such as hydrogen peroxide (H₂O₂) produced during inflammation. Here, we examined the effect of PS on H₂O₂-induced responses in native and heterologously expressed TRPA1 using a cell-based calcium assay. We also carried out behavioral experiments in vivo. In mouse sensory neurons, H₂O₂ elicited early TRPA1-dependent and late TRPA1-independent increases of [Ca²⁺]_i. The former was suppressed by the pretreatment with PS. In cells heterologously expressed TRPA1, PS suppressed [Ca²⁺]_i responses to H₂O₂. Simultaneous measurement of [Ca²⁺]_i and the intracellular PS level revealed that scavenging effect of PS was not related to the inhibitory effect. Removal of extracellular Ca²⁺, a calmodulin inhibitor and dithiothreitol attenuated the inhibitory effect of PS. Pretreatment with PS diminished nociceptive behaviors induced by H₂O₂. The present data suggest that PS suppresses oxidative stress-induced TRPA1 activation due to cysteine modification and Ca²⁺/calmodulin signaling. Thus, endogenous sulfurs may have regulatory roles in nociception via functional changes in TRPA1 under inflammatory conditions.

A multicenter cohort study of osimertinib compared with afatinib as first-line treatment for EGFR-mutated non-small-cell lung cancer from practical dataset: CJLSG1903

Background

FLAURA, the prospective trial of osimertinib as a first-line therapy compared with first-generation epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs), did not show superior survival benefit for osimertinib in either the subgroup of Asians or the subgroup with the L858R mutation. In addition, the superiority of osimertinib compared with second-generation EGFR-TKI is thus far unclear.

Patients and methods

We reviewed the clinical data of all consecutive patients who were treated with osimertinib or afatinib as first-line therapy between May 2016 and October 2019 from 15 institutions in Japan. We defined the groups based on first-line EGFR-TKI as the afatinib group and the osimertinib group. Outcomes included time to discontinuation of any EGFR-TKI (TD-TKI), overall survival (OS), and time to treatment failure, with propensity score analysis carried out as an exploratory analysis in the survival and subgroup analyses.

Results

A total of 554 patients were enrolled. Data on 326 patients in the osimertinib group, and 224 patients in the afatinib group were analyzed. TD-TKI adjusted by propensity score in the afatinib and osimertinib groups was 18.6 months (95% confidence interval 15.8 to 22.0) and 20.5 months (95% confidence interval 13.8 to not reached), respectively, without significant difference (P = 0.204). OS adjusted by propensity score favored the afatinib group with a significant difference (P = 0.018). Subgroup analysis with propensity score showed that patients with L858R and without brain metastasis had superior survival benefit with afatinib compared with osimertinib (P < 0.001).

Conclusions

TD-TKI in the afatinib group was not significantly prolonged compared with the osimertinib group in the practical data. In the exploratory analysis of patients with L858R-mutated non-small-cell lung cancer without brain metastasis, afatinib showed more benefit in OS over osimertinib.

•

The large-scale practical data of 550 patients who were treated with osimertinib or afatinib as first-line therapy were analyzed.

•

The superiority of osimertinib compared with afatinib could not be demonstrated in all populations.

•

Osimertinib therapy showed effectiveness in patients with brain metastasis.

•

Afatinib therapy showed potential benefit in patients with L858R mutation and without brain metastasis.

Anti-USAG-1 therapy for tooth regeneration through enhanced BMP signaling

Uterine sensitization-associated gene-1 (USAG-1) deficiency leads to enhanced bone morphogenetic protein (BMP) signaling, leading to supernumerary teeth formation. Furthermore, antibodies interfering with binding of USAG-1 to BMP, but not lipoprotein receptor-related protein 5/6 (LRP5/6), accelerate tooth development. Since USAG-1 inhibits Wnt and BMP signals, the essential factors for tooth development, via direct binding to BMP and Wnt coreceptor LRP5/6, we hypothesized that USAG-1 plays key regulatory roles in suppressing tooth development. However, the involvement of USAG-1 in various types of congenital tooth agenesis remains unknown. Here, we show that blocking USAG-1 function through USAG-1 knockout or anti-USAG-1 antibody administration relieves congenital tooth agenesis caused by various genetic abnormalities in mice. Our results demonstrate that USAG-1 controls the number of teeth by inhibiting development of potential tooth germs in wild-type or mutant mice missing teeth. Anti-USAG-1 antibody administration is, therefore, a promising approach for tooth regeneration therapy.

Promotion in solid phase reaction of Pt/SiOx bilayer film by electron-orbital-selective-excitation

A thermally impossible positive free energy reaction can proceed by electron-orbital-selective excitation. When the Si 2p core level is photo-excited in Pt/SiO_x bilayer films, Coulomb repulsion at the final two-hole state localized in the valence band by an interatomic Auger transition induces dissociation of the O atom and formation of a Si–Pt bond. Consequently, Pt₂Si silicide is formed by a positive free energy reaction. Under a single particle excitation of the valence band, low probability of the coexistence of the two-hole state for picosecond order suppresses to allow the reaction to proceed.

A thermally impossible positive free energy reaction can proceed by electron-orbital-selective excitation.

REACTOR PHYSICS EXPERIMENT IN A GRAPHITE-MODERATION SYSTEM FOR HTGR

The Japan Atomic Energy Agency (JAEA) started the Research and Development (R&D) to improve nuclear prediction techniques for High Temperature Gas-cooled Reactors (HTGRs). The objectives are to introduce a generalized bias factor method to avoid full mock-up experiment for the first commercial HTGR and to introduce reactor noise analysis to High Temperature Engineering Test Reactor (HTTR) experiment to observe sub-criticality. To achieve the objectives, the reactor core of graphite-moderation system named B7/4”G2/8”p8EUNU+3/8”p38EU(1) was newly composed in the B-rack of Kyoto University Critical Assembly (KUCA). The core is composed of the fuel assembly, driver fuel assembly, graphite reflector, and polyethylene reflector. The fuel assembly is composed of enriched uranium plate, natural uranium plate and graphite plates to realize the average fuel enrichment of HTTR and it’s spectrum. However, driver fuel assembly is necessary to achieve the criticality with the small-sized core. The core plays a role of the reference core of the bias factor method, and the reactor noise was measured to develop the noise analysis scheme. In this study, the overview of the criticality experiments is reported. The reactor configuration with graphite moderation system is rare case in the KUCA experiments, and this experiment is expected to contribute not only for an HTGR development but also for other types of a reactor in the graphite moderation system such as a molten salt reactor development.