Optics: a bibliometric approach to detect emerging research domains and intellectual bases

Optics is an important research domain both for its scientific interest and industrial applications. In this paper, we constructed a citation network of papers and performed topological clustering method to investigate the structure of research and to detect emerging research domains in optics. We found that optics consists of main five subclusters, optical communication, quantum optics, optical data processing, optical analysis and lasers. Then, we further investigated the detailed subcluster structures in it. By doing so, we detected some emerging research domains such as nonlinearity in photonic crystal fiber, broad band parametric amplifier, and in-vivo imaging techniques. We also discuss the distinction between research front and intellectual base in optics.     

Tracking modularity in citation networks

Citation network analysis is an effective tool to analyze the structure of scientific research. Clustering is often used to visualize scientific domain and to detect emerging research front there. While we often set arbitrarily clustering threshold, there is few guide to set appropriate threshold. This study analyzed basic process how clustering of citation network proceeds by tracking size and modularity change during clustering. We found that there are three stages in clustering of citation networks and it is universal across our case studies. In the first stage, core clusters in the domain are formed. In the second stage, peripheral clusters are formed, while core clusters continue to grow. In the third stage, core clusters grow again. We found the minimum corpus size around one hundred assuring the clustering. When the corpus size is less than one hundred, clustered network structure tends to be more random. In addition even for the corpus whose size is larger than it, the clustering quality for some clusters formed in the later stage is low. These results give a fundamental guidance to the user of citation network analysis.     

Gene expression property of high-density three-dimensional tissue of HepG2 cells formed in radial-flow bioreactor

In our previous study, we examined three-dimensional culture using 5-ml radial-flow bioreactor (RFB) and showed that genes encoding cell cycle related proteins were suppressed in a stable phase. In this study, we analyzed the gene expression profiles of RFB-cultivated HepG2 cells and found that vascular endothelial growth factor (VEGF) production was strongly induced in the stable phase compared with the growth phase or static two-dimensional culture. When human umbilical vein endothelial cells (HUVECs) were grown under the conditioned medium of the stable phase, it was found that the formation of new blood vessels was induced in the angiogenesis model. DNA microarray analysis showed that the expression levels of both genes related to cell cycle arrest and which are known as tumor markers have increased in the stable phase. This result suggests that HepG2 cells in the stable phase maintain an active tumor phenotype. In addition, the expression of genes induced in the hypoxic condition was also induced in the stable phase. When the culture was carried out under a higher dissolved oxygen (DO) concentration, VEGF production did not decrease significantly and the new blood-vessel-forming ability of the conditioned medium was not suppressed. This suggests that the induction of VEGF production in a stable phase is not affected by DO during the tested level. These results suggest that the RFB cell culture system may be used to assess tumor progression mechanism under three-dimensional condition in vitro.     

Synthesis and Photocatalytic Activity of Titania Pillared Clays

TiO₂-pillared clays such as montmorillonite, saponite and mica were prepared with an intercalation of polynuclear titanium complex formed by the reaction of Ti(i-C₃H₇O)₄ and acetic acid. Characterization of the products was performed by XRD, XPS, IR, UV-V spectra, the measurement of surface area and pore size distribution. The photocatalytic decomposition of carboxylic acids has been studied on TiO₂-pillared montmorillonite, saponite and mica. TiO₂-pillared mica showed higher catalytic activity than TiO₂ for the photocatalytic decomposition of acetic acid and adipic acid. On the contrarily, TiO₂ was the most active catalyst and TiO₂-pillared mica showed low activity for the photocatalytic decomposition of capric acid. The results show that the molecular size of carboxylic acid contributes to the catalytic activity of TiO₂-pillared clays.     

Robust Digital Control of a Broadband PWM Power Amplifier

Lately, it is required that the bandwidth of PWM （pulse width modulation） power amplifier is extended. For example, it is in application of the testing power supply of a low frequency immunity examination, or a class-D amplifier. In this paper, the authors show that the bandwidth of PWM power amplifier can be controller. This controller is implemented on a DSP （digital can be made wider with this controller. extended by using an approximate 2DOF （2-degree-of-freedom） digital signal processor）. It is demonstrated from experiments that the bandwidth     

Heat immunotherapy using magnetic nanoparticles and dendritic cells for T-lymphoma

Dendritic cells (DCs) are potent antigen-presenting cells that play important roles in regulating immune responses in cancer. Immunotherapy using these immunocytes has become an accepted therapeutic modality. We previously reported that hyperthermia using magnetic nanoparticles induces antitumor immunity, which could be activated by adjuvant including cytokines. In the present study, we investigated the therapeutic effects of hyperthermia combined with DC immunotherapy on mouse EL4 T-lymphoma. Magnetite cationic liposomes (MCLs) have a positive surface charge and generate heat in an alternating magnetic field (AMF) due to hysteresis loss. MCLs were injected into an EL4 nodule in C57BL/6 mice, which were subjected to AMF for 30 min. The temperature at the surface of the tumor reached 45 degrees C and was maintained by controlling the magnetic field intensity. Hyperthermia treatment was repeated twice with 24 h intervals. After hyperthermia, immature DCs were directly injected into the EL4 nodule. As a result, complete regression of tumors in 75% (6/8) of the mice was observed, while the percentage of complete regression of tumors was 12.5% (1/8) in the case of mice treated by hyperthermia alone. This novel cancer therapy, which we have termed "heat immunotherapy", may be applicable to patients with advanced malignancies.     

Short communication: Amino acids antagonistic to the amino acids inhibitory for growth rate of mixed ruminal bacteria

Antagonism of some amino acids (AA) to the inhibitory effects of other AA (Ile, Phe, and Thr) on the growth rate of mixed ruminal bacteria was investigated. In vitro growth rate of the mixed ruminal bacteria was inhibited when the 3 inhibitory AA (1 mM each) were each added to individual control treatments in which an ammonium salt was included as a sole N source. The inhibitory effect caused by Ile was relieved by addition of Leu or Val (equimolar to Ile), and no significant inhibition was shown when both Leu and Val were added together with Ile. The growth inhibition caused by Phe was also alleviated by supplementing with Trp, and was completely negated by adding Tyr. The inhibitory effect of Thr, on the other hand, was not affected by addition of Lys or Met (which are synthesized using a common pathway with Thr), but was mitigated by supplementation with Glu, Ser, Val, Ala, or Gln. Among the antagonistic AA, Leu, Val, Trp, Tyr, and Glu were indispensable for the maximum growth rate of the ruminal bacteria under the experimental condition of supplementation of amino-N, the removal of which from a mixture of 20 protein AA caused the growth rate to decline. Removals of Ile along with Leu or Val or both, of Phe along with Trp or Tyr, and of Thr along with Glu recovered the promotion of bacterial growth rate. It was concluded that inhibitions of the bacterial growth rate caused by Ile, Phe, or Thr could be antagonized by some other AA (Leu, Val, Tyr, Trp, or Glu), and the role of these latter AA as relievers of the inhibitory effects could explain why they are indispensable for maximum growth rate of ruminal bacteria.     

Protection against preterm delivery in mice by urinary trypsin inhibitor

OBJECTIVE: To investigate the precise mechanism by which urinary trypsin inhibitor suppresses cytokine production in the prevention of preterm delivery. METHODS: In vivo and in vitro studies were performed using ascites and peritoneal macrophages obtained on day 15 of pregnancy from female C3H/HeN mice that had been impregnated by B6D2F1 male mice. Lipopolysaccharide receptor, the intracellular signal transduction system, and nuclear factor-kappaB level were examined. RESULTS: In the in vivo study, we found that urinary trypsin inhibitor ameliorated the deterioration of intraperitoneal conditions induced by lipopolysaccharide (ie, increases in ascitic volume, peritoneal cell count, and tumor necrosis factor-alpha level) and caused a decrease in the binding of lipopolysaccharide to mouse macrophages. In the in vitro studies, urinary trypsin inhibitor decreased the binding capacity of lipopolysaccharide for its receptor, blocked the intracellular signal transduction induced by lipopolysaccharide, and decreased the nuclear factor-kappaB level. Increases were induced in the binding capacity of the macrophages for urinary trypsin inhibitor and its incorporation into them in the presence of lipopolysaccharide. CONCLUSION: We postulate that urinary trypsin inhibitor may suppress the production of inflammatory cytokines induced by lipopolysaccharide in mouse peritoneal macrophages through suppression of the lipopolysaccharide receptor, inhibition of the intracellular signal transduction system, and decrease in the nuclear factor-kappaB level.     

LO-RAY-LIGH@ Diffraction Gratings in UV-VIS Spectroscopy

It has been more than half a century since the release of the first Shimadzu UV-VIS （UV-visible） spectrophotometer QB-50 in 1952, and during this time more than 160,000 UV-VIS spectrometers have been produced and installed in a wide variety of different applications. A lot of technical innovations have been implemented to improve the performance and significantly reduce the stray light levels. The latest innovation during development of sophisticated spectrophotometers is based on a new holographic exposure method and optimized etching process which has made it possible to produce both high-efficient and exceptionally low stray light gratings. These LO-RAY-LIGH~ gratings have guaranteed values of stray light at the intermediate position between zero-order and first-order lights. The values are measured by Shimadzu＇s laser stray-light-measuring system. The latest development in the series of UV-VIS spectrophotometers is the UV-2700 which is a true double beam double monochromator system in a compact design for high-precision spectral analysis of a wide range of samples including organic and inorganic compounds, biological samples, optical materials and photovoltaics. The high performance optical system is designed with ＂LO-RAY-LIGH＂ diffraction gratings, featuring highest efficiency and exceptionally low stray light. The spectrophotometer operates in the wavelength range from 185 nm to 900 nm and allows highly sophisticated applications such as direct measurement of high density samples up to 8 absorbance units without dilution.