ALBERT

Description: Author(s): J. R. Calvey, W. Hartung, J. Makita, and M. Venturini The buildup of low energy electrons in an accelerator, known as electron cloud, can be severely detrimental to machine performance. Under certain beam conditions, the beam can become resonant with the cloud dynamics, accelerating the buildup of electrons. This paper will examine two such effects: mu… [Phys. Rev. Accel. Beams 19, 074401] Published Tue Jul 12, 2016

Description: In this work we present and discuss some results of latitudinal dependence in the cosmic noise absorption (CNA) as observed by the South American Riometer Network (SARINET) operated in the South American Magnetic Anomaly (SAMA) region, during a moderate intensity geomagnetic storm that occurred on 3 September 2008. In our analysis, we used the data acquired by the imaging riometers installed at São Martinho da Serra (SSO - geographic coordinate: 29.4°S, 53.1°W), Concepcion (CON - geographic coordinate: 36.5°S, 73.0°W) and Punta Arenas (PAC - geographic coordinate: 53.0°S, 70.5°W) and by the single beam riometer installed at Trelew (TRW - geographic coordinate: 43.1°S, 65.2°W). A comparison among the selected riometer data showed that the mean CNA was more pronounced at SSO, which is the site located nearest to the center of the SAMA, but the second highest value was found at the farther station. Also, a second-order polynomial curve fitting was performed in order to establish an empirical relationship between the mean CNA and the total intensity of the geomagnetic field at the riometer stations.

Description: We examined the effects of Asian monsoon rainfall on CH 4 absorption of water-unsaturated forest soil. We conducted a 1-year continuous measurement of soil CH 4 and CO 2 fluxes with automated chamber systems in three plots with different soil characteristics and water content to investigate how temporal variations in CH 4 fluxes vary with the soil environment. CH 4 absorption was reduced by the ‘Baiu’ summer rainfall event and peaked during the subsequent hot, dry period. Although CH 4 absorption and CO 2 emission typically increased as soil temperature increased, the temperature dependence of CH 4 varied more than that of CO 2 , possibly due to the changing balance of activities between methanotrophs and methanogens occurring over a wide temperature range, which was strongly affected by soil water content. In short time intervals (30 min), the responses of CH 4 and CO 2 fluxes to rainfall were different for each plot. In a dry soil plot with a thick humus layer, both fluxes decreased abruptly at the peak of rainfall intensity. After rainfall, CO 2 emission increased quickly, while CH 4 absorption increased gradually. Release of accumulated CO 2 underground and restriction and recovery of CH 4 and CO 2 exchange between soil and air determined flux responses to rainfall. In a wet soil plot and a dry soil plot with a thinner humus layer, abrupt decreases in CH 4 fluxes were not observed. Consequently, the Asian monsoon rainfall strongly influenced temporal variations in CH 4 fluxes, and the differences in flux responses to environmental factors among plots caused large variability in annual budgets of CH 4 fluxes.

Description: Author(s): G. Nersisyan, M. Makita, K. McKeever, T. Dzelzainis, S. White, E. Nedanovska, B. Kettle, R. Nicholl, G. Williams, D. Riley, and C. L. S. Lewis We present data on emission of K -shell radiation from Ti foils irradiated with subpicosecond pulses of second harmonic radiation (527 nm) from the TARANIS laser system at intensities of up to 10 18  W cm −2 . The data are used to demonstrate that a resonance absorption type mechanism is responsible for ... [Phys. Rev. E 85, 056415] Published Tue May 29, 2012

Description: Author(s): A. Lafuente-Sampietro, H. Utsumi, M. Sunaga, K. Makita, H. Boukari, S. Kuroda, and L. Besombes A detailed analysis of the photoluminescence (PL) intensity distribution in singly Cr-doped CdTe/ZnTe quantum dots (QDs) is performed. First of all, we demonstrate that hole-Cr flip-flops induced by an interplay of the hole-Cr exchange interaction and the coupling with acoustic phonons are the main ... [Phys. Rev. B 97, 155301] Published Mon Apr 02, 2018

Description: Author(s): J. R. Calvey, G. Dugan, W. Hartung, J. A. Livezey, J. Makita, and M. A. Palmer As part of the CesrTA program at Cornell, diagnostic devices to measure and quantify the electron cloud effect have been installed throughout the CESR ring. One such device is the retarding field analyzer, which provides information on the local electron cloud density and energy distribution. In a m... [Phys. Rev. ST Accel. Beams 17, 061001] Published Thu Jun 05, 2014

Description: Information related to the growth of fine roots is important for understanding C allocation in trees and the mechanisms of C cycling in ecosystems. Observations using a camera or scanner embedded in the soil enabled us to obtain continuous images of fine-root-growth dynamics. However, these methods are still labor-intensive because the image analysis has to be conducted manually. We developed an automated method for tracking movement or elongation of fine roots using a sequence of scanner images. We also show how data obtained with these methods can be used for calculating fine-root behavior. Two A4-size scanners were buried in a mixed forest in Japan and images were taken continuously from within the soil. We preprocessed these images by extracting the fine-root area from the images and developed an automated calculation plug-in we named A-root for tracking growth movement of the tips of fine roots. A-root and manual-tracking results were compared using the same images. The results show the A-root and manual-tracking methods yielded similar levels of accuracy. The average growth rate of 17 fine roots tracked using the program was 0.16 mm h –1 . The observation of the direction of growth in fine roots showed the direction may be influenced by the original root's growth where the fine roots branched, distribution of soil particles, other roots, and the force of gravity. The A-root analysis also suggested there may be an interaction between speed of growth and changes in direction of growing fine roots.

Description: To determine how colonization by different ectomycorrhizal (ECM)-fungal species affects the physiology and morphology of Quercus serrata seedlings, we assessed the net photosynthetic rate, the respiration rate of the lateral roots, leaf and root nitrogen (N) concentrations, specific leaf area, and specific root length in 9-month-old Q. serrata seedlings inoculated with Pisolithus tinctorius, Scleroderma citrinum, Laccaria amethystea , and Astraeus hygrometricus. While uninoculated control plants showed no colonization, the percentage of ECM colonization of root tips attained 35% with P. tinctorius and about 86% with the other three ECM species. Similar to ECM root colonization, the photosynthetic as well as the root-respiration rates were higher in seedlings with S. citrinum, L. amethystea , and A. hygrometricus than that in the control and those with P. tinctorius. Both the photosynthetic and root-respiration rates were positively correlated with ECM-fungal colonization. Similar trends were observed for the N concentration, specific leaf area, and specific root length, which differed significantly among ECM-fungal species and were related with ECM-fungal colonization. The results suggest that both physiological and morphological traits are specific to ECM-fungal species. As Q. serrata seedlings with high colonization can exhibit better resource-acquisition ability, the identification of strongly colonizing ECM-fungal species is essential. Comparisons with high- and low-colonizing ECM-fungal species improve our understanding of source–sink relationships in carbon allocation of forest tree species.

Description: Despite the advantage of plant clonality in patchy environments, studies focusing on genet demography in relation to spatially heterogeneous environments remain scarce. Regeneration of bamboos in forest understoreys after synchronous die-off provides an opportunity for assessing how they come to proliferate across heterogeneous light environments. In a Japanese forest, we examined genet demography of a population of Sasa kurilensis over a 7-year period starting 10 years after die-off, shortly after which some genets began spreading horizontally by rhizomes. The aboveground biomass was estimated, and genets were discriminated in 9-m 2 plots placed under both canopy gaps and closed canopies. Overall, the results suggest that the survival and spread of more productive genets and the spatial expansion of genets into closed canopies underlie the proliferation of S. kurilensis . Compared to canopy gaps, the recovery rate of biomass was much slower under closed canopies for the first 10 years after the die-off, but became accelerated during the next 7 years. Genet survival was greater for more productive genets (with greater initial number of culms), and the spaces occupied by genets that died were often colonized afterward by clonal growth of surviving genets. The number of genets decreased under canopy gaps due to greater mortality, but increased under closed canopies where greater number of genets colonized clonally from outside the plots than genets died. The colonizing genets were more productive (having larger culms) than those originally germinated within the plots, and the contribution of colonizing genets to the biomass was greater under closed canopies. Our study emphasizes the importance of investigating genet dynamics over relevant spatiotemporal scales to reveal processes underlying the success of clonal plants in heterogeneous habitats. Despite the advantage of plant clonality in patchy environments, studies focusing on genet demography in relation to spatially heterogeneous environments remain scarce. Regeneration of bamboos in forest understoreys after synchronous die-off provides an opportunity for assessing how they come to proliferate across heterogeneous light environments. We studied the long-term genet demography of a dwarf bamboo, Sasa kurilensis , after synchronous flowering and die-off, and found that the survival and spread of more productive genets and the clonal expansion of genets into closed canopies likely underlie the proliferation of S. kurilensis .