Thermal Diffusivity Measurement of Two-Layer Optical Thin-Film Systems Using Photoacoustic Effect1

In this study, we designed and developed two-layer antireflection (AR) optical coating samples on glass substrates, using different evaporation conditions of coating rates and substrate temperatures for two dielectric materials, MgF₂ and ZnS, with different refractive indices. The through-plane thermal diffusivity of these systems was measured using the photoacoustic effect. The optical thicknesses of MgF₂ and ZnS layers were fixed at 5/4 (=514.5 nm) and , respectively, and the thermal diffusivities of the samples were obtained from the measured amplitude of the photoacoustic signals by changing the chopping frequency of the Ar⁺ laser beam. The results demonstrated that the thermal diffusivity of the sample fabricated under the conditions of 10Å·s^–1 and 150°C had the maximum value and that the results were directly related to the microstructure of the film system.     

Thermal power estimation by fouling phenomena compensation using wavelet and principal component analysis

A small percentage of reactor thermal power can be overestimated because of fouling phenomena in a secondary feedwater flowmeter. This study proposes a signal processing technique for the compensation of a degraded flowmeter such a secondary feedwater flowmeter in nuclear power plants. The technique proposed is mainly focused on noise classification and step-by-step noise reduction. The noises focused are classified into the rapid distortion caused by environmental interference, the flow fluctuation according to plant state transition and the degradation by fouling phenomena qualitatively. The multi-step de-noising technique reduces each noise by three techniques step-by-step. The wavelet analysis as a low frequency pass filter to remove the rapid distortion, the linear principal component analysis (PCA) to predict a steady-state value from the fluctuation, and the non-linear PCA implemented as an autoassociative neural network (AANN) to predict an original value from the signal including fouling phenomena are developed. The main purpose of this approach is to make an AANN concentrate on compensating the degradation by fouling phenomena itself. For the demonstration the signals from a simulator and signal modeling were used so that the role and the performance of each noise removal step was represented. In addition a thermal power deviation estimator is proposed to recognize the degradation effect of each operating parameter for reactor thermal power calculation.     

Emerging Prospects of Exosomes for Cancer Treatment: From Conventional Therapy to Immunotherapy

Exosomes are a class of extracellular vesicles of around 100 nm in diameter that are secreted by most cells and contain various bioactive molecules reflecting their cellular origin and mediate intercellular communication. Studies of these exosomal features in tumor pathogenesis have led to the development of therapeutic and diagnostic approaches using exosomes for cancer therapy. Exosomes have many advantages for conveying therapeutic agents such as small interfering RNAs, microRNAs, membrane-associated proteins, and chemotherapeutic compounds; thus, they are considered a prime candidate as a delivery tool for cancer treatment. Since exosomes also provide an optimal microenvironment for the effective function of immunomodulatory factors, exosomes harboring bioactive molecules have been bioengineered as cancer immunotherapies that can effectively activate each stage of the cancer immunity cycle to successfully elicit cancer-specific immunity. This review discusses the advantages of exosomes for treating cancer and the challenges that must be overcome for their successful clinical development.     

Integrating Deep Learning and Machine Translation for Understanding Unrefined Languages

In the field of natural language processing (NLP), the advancement of neural machine translation has paved the way for cross-lingual research. Yet, most studies in NLP have evaluated the proposed language models on well-refined datasets. We investigate whether a machine translation approach is suitable for multilingual analysis of unrefined datasets, particularly, chat messages in Twitch. In order to address it, we collected the dataset, which included 7,066,854 and 3,365,569 chat messages from English and Korean streams, respectively. We employed several machine learning classifiers and neural networks with two different types of embedding: word-sequence embedding and the final layer of a pre-trained language model. The results of the employed models indicate that the accuracy difference between English, and English to Korean was relatively high, ranging from 3% to 12%. For Korean data (Korean, and Korean to English), it ranged from 0% to 2%. Therefore, the results imply that translation from a low-resource language (e.g., Korean) into a high-resource language (e.g., English) shows higher performance, in contrast to vice versa. Several implications and limitations of the presented results are also discussed. For instance, we suggest the feasibility of translation from resource-poor languages for using the tools of resource-rich languages in further analysis.     

Focused Ultrasound Enabled Trans‐Blood Brain Barrier Delivery of Gold Nanoclusters: Effect of Surface Charges and Quantification Using Positron Emission Tomography

Focused ultrasound (FUS) technology is reported to enhance the delivery of ⁶⁴Cu‐integrated ultrasmall gold nanoclusters (⁶⁴Cu‐AuNCs) across the blood‐brain barrier (BBB) as measured by positron emission tomography (PET). To better define the optimal physical properties for brain delivery, ⁶⁴Cu‐AuNCs with different surface charges are synthesized and characterized. In vivo biodistribution studies are performed to compare the individual organ uptake of each type of ⁶⁴Cu‐AuNCs. Quantitative PET imaging post‐FUS treatment shows site‐targeted brain penetration, retention, and diffusion of the negative, neutral, and positive ⁶⁴Cu‐AuNCs. Autoradiography is performed to compare the intrabrain distribution of these nanoclusters. PET Imaging demonstrates the effective BBB opening and successful delivery of ⁶⁴Cu‐AuNCs into the brain. Of the three ⁶⁴Cu‐AuNCs investigated, the neutrally charged nanostructure performs the best and is the candidate platform for future theranostic applications in neuro‐oncology.     

Role of lead in electrochemical reaction of alloy 600, alloy 690, Ni,Cr, and Fe in water

It has been reported that lead causes stress corrosion cracking (SCC) in the secondary side of steam generators (SG) in pressurized water reactors (PWR). The materials of SG tubings are alloy 600, alloy 690, or alloy 800, among which the main alloying elements are Ni, Cr, and Fe. The effect of lead on the electrochemical behaviors of alloy 600 and alloy 690 using an anodic polarization technique was evaluated. We also obtained polarization curves of pure Ni, Cr, and Fe in water containing lead. As the amount of lead in the solution increased, critical current densities and passive current densities of alloy 600 and alloy 690 increased, while the breakdown potential of the alloys decreased. Lead increased critical current density and the passive current of Cr in pH 4 and pH 10. The instability of passive film of steam generator tubings in water containing lead might arise from the instability of Cr passivity.     

Differences in embryonic development in sensitive and resistant matings to pregnancy block stimuli in mice

Pregnancy block from exposure to foreign male mouse pheromones is sensitive to both male and female mating strain, as well as the foreign male pheromone-producing strain. Incidence of pregnancy block by male pheromones in mice is different depending on the combination of females, stud males and stimulus males. BALB/cA females mated with BALB/cA males showed a 100% pregnancy block when exposed to males of the DDK strain (Chung et al., 1997). In contrast, BALB/cA females mated with males of dissimilar strain show high rates of pregnancy even if they are exposed to DDK males; this difference is thought to be due to the difference in viability of embryos (Chung et al., 1999). The present study investigated how development of BALB/cA and F1 embryos differ under the influence of pregnancy block stimuli. F1 embryos had significantly higher numbers of cells than did the BALB/cA embryos (P<0.05) at day 3 of pregnancy after exposure to DDK males or after bromocriptine (dopamine agonist, 4 mg kg(-1), i.p.) treatment. Histological observation after bromocriptine treatment revealed that: (i) on day 4 of pregnancy, BALB/cA embryos tended to form a large blastocoel, but showed abnormalities such as degeneration of primitive endoderm and depression of the outer trophoblast-distal endoderm layer at the periphery of the inner cell mass (ICM) or detachment of the ICM from the outer layer. In contrast, 60-70% of F1 embryos were normal late blastocysts and incipient egg cylinders, but 28-40% of early blastocysts were degenerating; and (ii) day 5 BALB/cA embryos were in the range from incipient egg cylinder with a large proamniotic cavity to ectoplacental cone only, but their proximal endoderm and trophoblast-distal endoderm layer were degenerating. In contrast, the F1 embryos were mostly at the egg cylinder stage and maintained normal structure except for occasional enlargement of the developing yolk sac cavity. These results indicate that the lining of the inner surface of trophoblast by distal endoderm layer may be more firmly established and that the inner environment for development of F1 embryos may be more effectively maintained, thereby making them more resistant to deleterious influences due to pregnancy block stimuli than are BALB/cA embryos.     

A microfluidic bioreactor based on hydrogel-entrapped E. coli: cell viability,lysis, and intracellular enzyme reactions

Viable E. coli cells were entrapped in hydrogel micropatches photopolymerized within microfluidic systems. The microfluidic channels and the micropatches have sizes on the order of 100-500 microm. Small molecules, such as dyes and surfactants, present in the solution surrounding the hydrogel, are able to diffuse into the gel and encounter the cells, but the cells are sufficiently large to be retained. For example, sodium dodecyl sulfate is a lysis agent that is able to penetrate the hydrogel and disrupt the cellular membrane. Entrapment of viable cells within hydrogels, followed by lysis, could provide a convenient means for preparing biocatalysts without the need for enzyme extraction and purification. Hydrogel-immobilized cells are able to carry out chemical reactions within microfluidic channels. Specifically, a nonfluorescent dye, BCECF-AM, is able to penetrate both the hydrogel and the bacterial membrane and be converted into a fluorescent form (BCECF) by the interior cellular machinery. These results suggest that cells immobilized within microfluidic channels can act as sensors for small molecules and as bioreactors for carrying out reactions.