Kimitsugu Nakamura

Development of a high-sensitivity UV photocathode using GaN film that works in transmission mode

We developed a high-sensitivity GaN photocathode that works in transmission mode. It has 40.9 % quantum efficiency at 310 nm wavelength. Conventional GaN photocathodes, both transmission mode and reflection mode, are made on a sapphire substrate using metal-organic vapor phase epitaxy (MOVPE). In reflection mode, a GaN photocathode has very high quantum efficiency (QE) of over 50 %. However, in transmission mode, the quantum efficiency of a GaN photocathode was about 25 % at 240 nm with this technique. Therefore, we developed a new GaN photocathode using a glass-bonding technique, where a GaN thin film was bonded to a glass face plate. We found out that constituting an Al- GaN layer on the light incidence side of the photocathode surface provided higher QE than a sole GaN layer type for transmission mode. We focused on the band bending of the photocathode, and analyzed QE for both transmission mode and reflection mode. We then verified the effectiveness of the AlGaN layer using the results from the analysis. The high-sensitivity UV photocathode will be used for flame detection, corona discharge observation, and other UV imaging.

Development of a saliva collection device for use in the field

BACKGROUND For monitoring biomarkers, saliva has several distinct advantages over other biological fluids. Saliva sampling is relatively non-invasive and enables the collection from either adults or infants under many different circumstances. However, there is no collection device that can be speedily used for analysis in the field. The aim of the present study was to evaluate the suitability of a new device, termed Muddler, compared with commercially available collection devices. METHODS Saliva was collected from healthy volunteers. The collection devices such as Muddler, eye sponge, Salivette® Cotton (SC) and Salivette® Synthetic (SS) were evaluated in terms of the volume and/or composition of the collected saliva. The amounts of immunoglobulin A (IgA) and lactofferin in saliva were assessed by the enzyme-linked immunosorbent assays with the corresponding antibodies. Amylase activity was measured using a commercially available kit, and high molecular weight complexes including mucin were assessed by SDS-PAGE staining. RESULTS A newly developed Muddler, which was made of plastic plate, was the best device for collecting a constant volume of saliva among all the devices examined in the present study. Furthermore, Muddler can collect without change in composition of salivary proteins such as IgA, lactoferrin, amylase, and mucin complex, whereas the levels of the salivary proteins obtained with all the commercial devices used were clearly different from those in original saliva. CONCLUSIONS The newly developed Muddler was the best collection device in terms of the accuracy of collection and the reliability of measurements among all the devices examined in the present study.

Recent Progress of Photocathodes for PMTs

The quantum efficiency (QE), the conversion efficiency of a photon to an electron, is one of the most important performance of photon sensors. In general, the QE of opto-semiconductor devices is superior to that of photocathodes for PMTs. As a result of our continuous efforts to improve them, an ultra bialkali photocathode (UBA) released a few years ago shows QE higher than 40% at 380nm, GaAsP does 50% in 550nm, and GaAs 30% in 750nm. In the case of UBA, however, linearity is a problem, when it is cooled down to liquid xenon temperature (-108 degree centigrade) for dark matter experiments. For these experiments, a high linearity photocathode at low temperature has been developed. This photocathode shows a little less QE than UBA, but much lower dark current than UBA even at room temperature, thus its a good compromise in S/N ratio. Including these topics, recent progresses of photocathode is described.

Psychological stress secrets peroxidase and thiocyanate in oral cavity quickly

Cancer syndromes are associated with brain-mediated sickness symptoms including anorexia and cachexia, as well as fatigue and behavioral depression. Expression of the activation marker c-Fos has been reported in forebrain regions implicated in ingestive behavior (Konsman and Blomqvist, 2005) in cachexic tumor-bearing animals. The distribution of activated neurons in the forebrain was similar to that seen following experimental immune challenges. Because the nucleus of the solitary tract (nTS) is reliably responds to peripheral immune challenge, we questioned whether peripheral tumors might also activate neurons in the nTS. Ten female Sprague–Dawley female rats with idiopathic mammary tumors (mean BW = 303.4 g; mean tumor weight 5.5 g), and eleven age matched controls, were transcardially perfused with paraformaldehyde in preparation for immunohistochemical assessment of c-Fos protein induction in the brainstem. The number of c-Fos positive neuronal nuclei was significantly increased in the nTS [F (1,19) = 40.11, (p < .0001)] in tumor-bearing rats compared to controls. These findings suggest that the pattern of brain responses to peripheral tumors may be similar to those following peripheral immune challenge. The nTS serves as an interface by which visceral sensory and neuroendocrine signals can influence brain neurocircuitry influencing autonomic functions, as well as mood and arousal states, thus these findings provide an anatomical substrate by which cancer could influence widespread brain functions.

Possibility of using salivary ultra-weak chemiluminescence as a biomarker for feelings of anxiety in hospital settings.

The aim of this study was to assess whether a particular value of noninvasive salivary ultra-weak chemiluminescence (UCL) could be used as a biomarker of psychological stress. Our study covered two groups. Group 1 comprised six healthy volunteers who stayed in a hospital for one night and group 2 comprised 15 patients with lung cancer and 24 patients with respiratory diseases other than lung cancer who were in hospital for an extended stay. First, we evaluated the UCL of saliva from six healthy volunteers before and after one night in hospital. Immunoglobulin A (IgA) concentrations were also measured. The integrated intensity value of UCL was correlated with the IgA concentration (correlation coefficient 0.90). Second, in the case of a long hospital stay, we found that the maximum salivary UCL intensities were higher in patients with lung cancer than in those with respiratory diseases other than lung cancer or in 28 healthy controls. Copyright

The relationship between secretory IgA and ultra-weak chemiluminescence in saliva exposed to performance anxiety

The relationship between secretory IgA and ultra-weak chemiluminescence in saliva exposed to performance anxiety Hirohito Tsuboi , Nobuhiro Goi , Naohide Kinae , Hitoshi Harada , Mitsuo Hiramatsu , Kimitsugu Nakamura , Kuniaki Takagi b a Department of Epidemiology and Public Health, School of Health Promotional Sciences, University of Hamamatsu, Hamamatsu, Japan b Department of Environmental Biochemistry, School of Pharmaceutical Science, University of Shizuoka, Japan c Graduate School of Food and Nutritional Sciences, University of Shizuoka, Shizuoka, Japan d Hamamatsu Photonics, K.K. Central Research Laboratory, Hirakuchi, Hamakita, Japan e Hamamatsu Photonics, K.K. Electron Tube Division, Toyooka, Japan