10 research outputs found
Observation of ultrafast amorphization dynamics in GeCu2Te3 thin films using echelon-based single-shot transient absorbance spectroscopy
Get PDFThe compound GeCu2Te3 (GCT) has attracted considerable attention because of its several advantages for next-generation nonvolatile memories, including its higher thermal stability and lower volume change, with large optical contrast between the crystalline and amorphous phases. In this study, we demonstrate the ultrafast amorphization dynamics that occur in GCT by utilizing echelon-based single-shot transient absorbance spectroscopy and coherent phonon spectroscopy. We find that the timescale of the absorbance change accompanying amorphization is ∼2 ps, which is close to the dephasing time of the A1 optical phonons. Based on the observed results and the robust structural network of crystalline GCT, we discuss the amorphization dynamics in GCT by comparing it with that in the typical phase-change material Ge2Sb2Te5.journal articl
Nanoscale phase change on Ge2Sb2Te5 thin films induced by optical near fields with photoassisted scanning tunneling microscope
Get PDFA scanning probe microscope coupled with either femtosecond laser pulses or terahertz pulses holds great promise not only for observing ultrafast phenomena but also for fabricating desirable structures at the nanoscale. In this study, we demonstrate that a few-nanometer-scale phase change can be non-thermally stored on the Ge2Sb2Te5 surface by a laser-driven scanning tunneling microscope (STM). An atomically flat Ge2Sb2Te5 surface was irradiated with the optical near-field generated by introducing femtosecond laser pulses to the STM tip-sample junction. The STM topographic images showed that few-nanometer-scale mounds appeared after irradiation. In addition, tunneling conductance spectra showed that the bandgap increased by 0.2 eV in the area of 5 × 5 nm2. These indicate that the nanoscale crystal-to-amorphous phase change was induced by the STM-tip-induced near field. Our approach presented here offers an unprecedented increase in the recording density of optical storage devices and is, therefore, expected to facilitate the development of next-generation information technology.journal articl
Thermal Stress Disrupts Brain Development.
No full text<p>(A) Frontal 7 µm paraffin sections of MB calyces at their broadest point, viewed with a fluorescence photo microscope. MBs are smaller in HS flies than in the CT group. (B) Heat stress induced a significant 31% reduction in MB calyx volume (<i>F</i><sub>[1,97]</sub> = 188.39, <i>P</i><0.0001), estimated from planimetric measurements of serial sections of HS and CT flies shown in (A). (C) MB pedunculus cross-section area (the means of measurements from three serial caudal sections) was reduced by 29% in HS flies (<i>F</i><sub>[1,97]</sub> = 123.43, <i>P</i><0.0001). (D) AL volume [derived as in (B)] was reduced by 15% in HS flies (<i>F</i><sub>[1,51]</sub> = 26.04, <i>P</i><0.0001). (E) Optic lobe volume [medulla+lobula, derived as in (B)] was not significantly influenced by heat stress (<i>F</i><sub>[1,40]</sub> = 1.59, <i>P</i> = 0.22). (F) Central complex volume [fan shaped body+ellipsoid body, derived as in (B)] was reduced by 9% in HS male flies only (<i>F</i><sub>[1,51[</sub> = 10.78, <i>P</i> = 0.002). (G) Wing area was reduced by 6% in HS female flies only (<i>F</i><sub>[1,60]</sub> = 7.04, <i>P</i> = 0.01). (H) Forelimb length was not significantly affected in HS flies (<i>F</i><sub>[1,60]</sub> = 1.21, <i>P</i> = 0.28). (B–H) Bars are mean±standard error (SE); <i>n</i> indicated on each bar. Different letters designate significant differences (SNK, <i>P</i>≤0.05).</p
Associative Odor Learning is Impaired by Thermal Stress.
No full text<p>(A) Olfactory learning and memory. The mean performance index calculated for HS flies was lower than CT flies at all time intervals. A two-way ANOVA detected significant effects of treatment (<i>F</i><sub>[1,56]</sub> = 101.25, <i>P</i><0.0001) and time (<i>F</i><sub>[2,56]</sub> = 41.93, <i>P</i><0.0001), while the interaction component was not significant; <i>F</i><sub>[2,56]</sub> = 2.00, <i>P</i> = 0.15). (B) Shock reactivity. HS flies showed normal avoidance of 80 V dc electric shock used in (A) and a slight reduction in avoidance at 120 V (<i>F</i><sub>[1,36]</sub> = 6.23, <i>P</i> = 0.017). (C) MCH odor avoidance. HS flies demonstrated a normal avoidance of MCH at the 1×10<sup>−2</sup> dilution used in (A) and a slight reduction in avoidance at the 5×10<sup>−3</sup> dilution (<i>F</i><sub>[1,37]</sub> = 14.72, <i>P</i> = 0.0005). (D) OCT odor avoidance. HS flies demonstrated normal avoidance responses to OCT at both dilutions. (A–D) Symbols or bars are mean±SE; <i>n</i> indicated above each symbol or on each bar. Different letters designate significant differences (SNK, <i>P</i>≤0.05).</p
Thermal Stress Disrupts MB Development by Reducing KC Numbers.
No full text<p>(A) Cytoplasm-targeted GFP expression patterns driven by different <i>GAL4</i>-expressing elements in whole mount brains of CT (top) and HS (bottom) flies viewed with a laser scanning confocal microscope. All MB structural elements represented in each of three CT <i>P[GAL4]/T10</i> genotypes were present (labeled) but clearly diminished in HS flies. We noted that cytoplasm-targeted GFP revealed low-level enhancer activity (labeled in blue) that is often not observed when targeting GFP expression to membranes (see references 50 and 52 for examples). (B) Nuclear-targeted GFP expression patterns driven by different <i>GAL4</i>-expressing elements in whole mount brains of CT (top) and HS (bottom) flies viewed with a laser scanning confocal microscope. We observed fewer KCs in the three HS <i>P[GAL4]/nls14</i> genotypes compared with CT flies. (C) KCs counted in the brains of flies represented in (B). A two-way ANOVA found highly significant effects of genotype (<i>F</i><sub>[2,104]</sub> = 42.36, <i>P</i><0.0001) and treatment (<i>F</i><sub>[1,104]</sub> = 143.00, <i>P</i><0.0001), while the interaction component was not significant (<i>F</i><sub>[1,104]</sub> = 2.69, <i>P</i> = 0.07). KC numbers were reduced by 29% in <i>247/nls14</i>, 36% in <i>201Y/nls14</i> and 57% in <i>c739/nls14</i>. Bars are mean±SE; <i>n</i> indicated on each bar. Different letters designate significant differences (SNK, <i>P</i>≤0.05).</p
All Classes of Intrinsic MB Neurons Are Sensitive to Thermal Stress.
No full text<p>(A) Schematic illustration of heat stress treatment administered 35 min/day throughout larval and pupal development, or restricted to specific developmental stages that correspond with the birth of MB neurons projecting to γ, α′β′, or αβ-lobes. (B) MB calyx volume measurements (derived as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0001125#pone-0001125-g001" target="_blank">figure 1B</a>). All three classes of MB neurons are sensitive to heat stress (<i>F</i><sub>[4,138]</sub> = 17.92, <i>P</i><0.0001). Calyx volume in flies receiving daily episodes of heat stress treatment throughout development reflected additive reductions of each of the three neuron classes exposed to heat stress as shown in (A). Bars are mean±SE; <i>n</i> indicated on each bar. Different letters designate significant differences (SNK, <i>P</i>≤0.05).</p
