1,014 research outputs found
Fire and edge effects in a fragmented tropical forest landscape in the southwestern Amazon.
The Amazon holds the largest tropical rain forest formation in the world but this natural ecosystem has been altered by both anthropogenic and natural disturbances since the 1970s (Davidson et al., 2012). The Brazilian Amazon experienced the highest annual tropical deforestation rates until the mid-2000s when rates began to decline dramatically due to the government?s environmental law enforcement. Conversely, other forest disturbances, such as understory fire, selective logging, and fragmentation (Aragao et al., 2014; Arima et al., 2014) have gained more importance in terms of their impacts on remnant forests. The degree of forest degradation varies as functions of disturbance type, the intensity and frequency of disturbance events, and the time since occurrence (Cochrane and Schulze, 1999; Barlow and Peres, 2004; Brando et al., 2014). Additionally, the impacts of these disturbances may vary across the region due to different gradients of physical conditions including rainfall, edaphic and geological properties (Hoorn et al., 2010; Malhi et al., 2004)
Usefulness of Real-Time 4D Ultrasonography during Radiofrequency Ablation in a Case of Hepatocellular Carcinoma
We report a case of hepatocellular carcinoma (HCC) with chronic hepatitis C virus infection successfully treated with percutaneous radiofrequency ablation (RFA) under live four-dimensional (4D) echo guidance. A 65-year-old Japanese man had a HCC nodule in the liver S5 region 2.0 cm in diameter. We performed real-time 4D ultrasonography during RFA therapy with a LeVeen needle electrode. The echo guidance facilitated an accurate approach for the needle puncture. The guidance was also useful for confirming whether an adequate safety margin for the nodule had been obtained. Thus real-time 4D ultrasonography echo technique appears to provide safe guidance of RFA needles via accurate targeting of HCC nodules, thereby allowing real-time visualization when combined with echo contrast. Furthermore the position of the needle in a still image was confirmed in every area using a multiview procedure
Satellite-based characterization of climatic conditions before large-scale general flowering events in Peninsular Malaysia
General flowering (GF) is a unique phenomenon wherein, at irregular intervals, taxonomically diverse trees in Southeast Asian dipterocarp forests synchronize their reproduction at the community level. Triggers of GF, including drought and low minimum temperatures a few months previously has been limitedly observed across large regional scales due to lack of meteorological stations. Here, we aim to identify the climatic conditions that trigger large-scale GF in Peninsular Malaysia using satellite sensors, Tropical Rainfall Measuring Mission (TRMM) and Moderate Resolution Imaging Spectroradiometer (MODIS), to evaluate the climatic conditions of focal forests. We observed antecedent drought, low temperature and high photosynthetic radiation conditions before large-scale GF events, suggesting that large-scale GF events could be triggered by these factors. In contrast, we found higher-magnitude GF in forests where lower precipitation preceded large-scale GF events. GF magnitude was also negatively influenced by land surface temperature (LST) for a large-scale GF event. Therefore, we suggest that spatial extent of drought may be related to that of GF forests, and that the spatial pattern of LST may be related to that of GF occurrence. With significant new findings and other results that were consistent with previous research we clarified complicated environmental correlates with the GF phenomenon
Gyrokinetic simulations of the tearing instability
Linear gyrokinetic simulations covering the collisional -- collisionless
transitional regime of the tearing instability are performed. It is shown that
the growth rate scaling with collisionality agrees well with that predicted by
a two-fluid theory for a low plasma beta case in which ion kinetic dynamics are
negligible. Electron wave-particle interactions (Landau damping), finite Larmor
radius, and other kinetic effects invalidate the fluid theory in the
collisionless regime, in which a general non-polytropic equation of state for
pressure (temperature) perturbations should be considered. We also vary the
ratio of the background ion to electron temperatures, and show that the
scalings expected from existing calculations can be recovered, but only in the
limit of very low beta.Comment: 7 pages, 10 figures, submitted to Po
Chlorine Isotopes: As a Possible Tracer of Fluid/Bio-Activities on Mars and a Progress Report on Chlorine Isotope Analysis by TIMs
Significantly large mass fractionations between chlorine isotopes (Cl-35, Cl-37) have been reported for terrestrial materials including both geological samples and laboratory materials. Also, the chlorine isotopic composition can be used as a tracer for early solar system processes. Moreover, chlorine is ubiquitous on the Martian surface. Typical chlorine abundances in Gusev soils are approx.0.5 %. The global surface average chlorine abundance also is approx.0.5 %. Striking variations among outcrop rocks at Meridiani were reported with some chlorine abundances as high as approx.2%. Characterizing conditions under which chlorine isotopic fractionation may occur is clearly of interest to planetary science. Thus, we have initiated development of a chlorine isotopic analysis technique using TIMS at NASA-JSC. We present here a progress report on the current status of development at JSC and discuss the possible application of chlorine isotopic analysis to Martian meteorites in a search for fluid- and possibly biological activity on Mars
Upscaling remote estimation on relative abundance of chengal trees in tropical rainforest using modified canopy fractional cover (mCFC) approach
Forest degradation and deforestation is crucial to be monitored. Thus, aggressive sustainable forest management is needed. Tree species composition estimations at large spatial scale is crucial to achieve sustainable forest management and monitor forest degradation and deforestation occurrences. Thus, monitoring by using remotely sensed data would be helpful to cover large spatial extend of tropical rainforest. However, due to coarse spatial resolution the estimation of tree species composition nearly impossible due to mixing pixel problem. Nonetheless, utilizing modified Canopy Fractional Cover (mCFC) would help to overcome mixing pixels in coarse spatial resolution satellite data. Accuracy of the results suggest that mCFC is suitable to be utilized for estimating relative abundance of Chengal at large extend area
Very high quality factor measured in annealed fused silica
We present the results of quality factor measurements for rod samples made of
fused silica. To decrease the dissipation we annealed our samples. The highest
quality factor that we observed was for a mode at
384 Hz. This is the highest published value of in fused silica measured to
date.Comment: 8 pages, 2 figure
A high stability semiconductor laser system for a Sr-based optical lattice clock
We describe a frequency stabilized diode laser at 698 nm used for high
resolution spectroscopy of the 1S0-3P0 strontium clock transition. For the
laser stabilization we use state-of-the-art symmetrically suspended optical
cavities optimized for very low thermal noise at room temperature. Two-stage
frequency stabilization to high finesse optical cavities results in measured
laser frequency noise about a factor of three above the cavity thermal noise
between 2 Hz and 11 Hz. With this system, we demonstrate high resolution remote
spectroscopy on the 88Sr clock transition by transferring the laser output over
a phase-noise-compensated 200 m-long fiber link between two separated
laboratories. Our dedicated fiber link ensures a transfer of the optical
carrier with frequency stability of 7 \cdot 10^{-18} after 100 s integration
time, which could enable the observation of the strontium clock transition with
an atomic Q of 10^{14}. Furthermore, with an eye towards the development of
transportable optical clocks, we investigate how the complete laser system
(laser+optics+cavity) can be influenced by environmental disturbances in terms
of both short- and long-term frequency stability.Comment: 9 pages, 9 figures, submitted to Appl. Phys.
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