scholarly journals Scaling laws for step bunching on vicinal surfaces: Role of the dynamical and chemical effects

2021 ◽  
Vol 104 (3) ◽  
Author(s):  
L. Benoit–Maréchal ◽  
M. E. Jabbour ◽  
N. Triantafyllidis
Keyword(s):  
Scaling Laws ◽  
Vicinal Surfaces ◽  
Step Bunching ◽  
Chemical Effects

DC-HEATING-INDUCED ANTIBAND FORMATION AND SUBSEQUENT STEP WANDERING ON Si(111) STUDIED BY IN-SITU REM

1999 ◽  
Vol 06 (06) ◽  
pp. 977-984 ◽  
Author(s):  
MASASHI DEGAWA ◽  
HIROKI MINODA ◽  
YASUMASA TANISHIRO ◽  
KATSUMICHI YAGI
Keyword(s):  
Electron Microscopy ◽  
Present Report ◽  
Current Direction ◽  
Vicinal Surfaces ◽  
Step Bunching ◽  
Subsequent Step ◽  
Step Down ◽  
Scanning Electron

Direct current fed through a Si crystal with (111) vicinal surfaces induces step bunching and wandering which depend on the temperature and the current direction. In the present report in-situ reflection electron microscope studies of antiband formation and the growth of step wandering are presented together with supplemental observations by scanning electron microscopy and optical microscopy. Observations were for the temperature range (about 1000–1180°C) where the step-down current induces step wandering and the step-up current induces step bunching and antiband formation and subsequent step wandering. An important role of antiband formation for step wandering in the step-up current regions is presented.

scholarly journals Sulfur-centered hemi-bond radicals as active intermediates in S-DNA phosphorothioate oxidation

2019 ◽  
Author(s):  
Jialong Jie ◽  
Ye Xia ◽  
Chun-Hua Huang ◽  
Hongmei Zhao ◽  
Chunfan Yang ◽  
...  
Keyword(s):  
Bacterial Genome ◽  
Protective Role ◽  
Hole Transfer ◽  
Time Resolved ◽  
Dna Lesion ◽  
Chemical Effects ◽  
Redox Active ◽  
Underlying Mechanisms ◽  
Active Intermediates

Abstract Phosphorothioate (PS) modifications naturally appear in bacteria and archaea genome and are widely used as antisense strategy in gene therapy. But the chemical effects of PS introduction as a redox active site into DNA (S-DNA) is still poorly understood. Herein, we perform time-resolved spectroscopy to examine the underlying mechanisms and dynamics of the PS oxidation by potent radicals in free model, in dinucleotide, and in S-oligomer. The crucial sulphur-centered hemi-bonded intermediates -P–S∴S–P- were observed and found to play critical roles leading to the stable adducts of -P–S–S–P-, which are backbone DNA lesion products. Moreover, the oxidation of the PS moiety in dinucleotides d[GPSG], d[APSA], d[GPSA], d[APSG] and in S-oligomers was monitored in real-time, showing that PS oxidation can compete with adenine but not with guanine. Significantly, hole transfer process from A+• to PS and concomitant -P–S∴S–P- formation was observed, demonstrating the base-to-backbone hole transfer unique to S-DNA, which is different from the normally adopted backbone-to-base hole transfer in native DNA. These findings reveal the distinct backbone lesion pathway brought by the PS modification and also imply an alternative -P–S∴S–P-/-P–S–S–P- pathway accounting for the interesting protective role of PS as an oxidation sacrifice in bacterial genome.

scholarly journals Unification of step bunching phenomena on vicinal surfaces

2007 ◽  
Vol 76 (3) ◽  
Author(s):  
Pak-Wing Fok ◽  
Rodolfo R. Rosales ◽  
Dionisios Margetis
Keyword(s):  
Vicinal Surfaces ◽  
Step Bunching

The role of step collisions on diffraction from vicinal surfaces

1992 ◽  
Vol 276 (1-3) ◽  
pp. 308-324 ◽  
Author(s):  
N.C. Bartelt ◽  
T.L. Einstein ◽  
Ellen D. Williams
Keyword(s):  
Vicinal Surfaces

scholarly journals Step-bunching transitions on vicinal surfaces with attractive step interactions

2000 ◽  
Vol 467 (1-3) ◽  
pp. 58-84 ◽  
Author(s):  
V.B. Shenoy ◽  
Shiwei Zhang ◽  
W.F. Saam
Keyword(s):  
Vicinal Surfaces ◽  
Step Bunching

scholarly journals Speech can produce jet-like transport relevant to asymptomatic spreading of virus

2020 ◽  
Vol 117 (41) ◽  
pp. 25237-25245 ◽  
Author(s):  
Manouk Abkarian ◽  
Simon Mendez ◽  
Nan Xue ◽  
Fan Yang ◽  
Howard A. Stone
Keyword(s):  
Social Interactions ◽  
Disease Transmission ◽  
Laboratory Experiments ◽  
Scaling Laws ◽  
Mitigation Strategies ◽  
Directed Transport ◽  
Transport Distance ◽  
Long Time ◽  
Phonetic Features

Many scientific reports document that asymptomatic and presymptomatic individuals contribute to the spread of COVID-19, probably during conversations in social interactions. Droplet emission occurs during speech, yet few studies document the flow to provide the transport mechanism. This lack of understanding prevents informed public health guidance for risk reduction and mitigation strategies, e.g., the “6-foot rule.” Here we analyze flows during breathing and speaking, including phonetic features, using orders-of-magnitude estimates, numerical simulations, and laboratory experiments. We document the spatiotemporal structure of the expelled airflow. Phonetic characteristics of plosive sounds like “P” lead to enhanced directed transport, including jet-like flows that entrain the surrounding air. We highlight three distinct temporal scaling laws for the transport distance of exhaled material including 1) transport over a short distance (<0.5 m) in a fraction of a second, with large angular variations due to the complexity of speech; 2) a longer distance, ∼1 m, where directed transport is driven by individual vortical puffs corresponding to plosive sounds; and 3) a distance out to about 2 m, or even farther, where sequential plosives in a sentence, corresponding effectively to a train of puffs, create conical, jet-like flows. The latter dictates the long-time transport in a conversation. We believe that this work will inform thinking about the role of ventilation, aerosol transport in disease transmission for humans and other animals, and yield a better understanding of linguistic aerodynamics, i.e., aerophonetics.

Charge distributions and chemical effects. XL. Chemical bonds in benzenoid hydrocarbons

1986 ◽  
Vol 64 (2) ◽  
pp. 404-412 ◽  
Author(s):  
S. Fliszár ◽  
G. Cardinal ◽  
N. A. Baykara
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Atomic Charges ◽  
Chemical Bonds ◽  
Benzenoid Hydrocarbons ◽  
Average Deviation ◽  
Chemical Effects ◽  
Local Charge ◽  
Theoretical Results

Benzenoid hydrocarbons were examined using a bond energy scheme featuring the role of atomic charges. The latter were conveniently deduced from appropriate correlations between theoretical results and 13C nuclear magnetic resonance shifts. Atomization energies calculated in this manner agree with their experimental counterparts to within 0.36 kcal mol-1 (average deviation). It appears that benzenoid hydrocarbons can be efficiently described in terms of local charge density properties. In the absence of any distinctive specific feature characterizing benzenoids, this particular description of chemical bonds ultimately results in a unifying genealogy smoothly relating to one another the various possible types of CC and CH bonds which are formed by sp2 and sp3 carbons.

scholarly journals Topographic changes due to the 2004 Chuetsu thrusting earthquake in low mountain region

2019 ◽  
Author(s):  
Zhikun Ren ◽  
Takashi Oguchi ◽  
Peizhen Zhang ◽  
Shoichiro Uchiyama
Keyword(s):  
Scaling Laws ◽  
Catchment Scale ◽  
Volume Estimate ◽  
Epicentral Area ◽  
Quantitative Studies ◽  
Landslide Volume ◽  
Seismically Induced Landslides ◽  
Seismic Landslide ◽  
Topographic Evolution

Abstract. The co-seismic landslide volume information is critical to understanding the role of strong earthquake in topographic evolution. However, the co-seismic landslide volumes are mainly obtained using statistical scaling laws, which are not accurate enough for quantitative studies of the spatial pattern of co-seismically induced erosion and the topographic changes caused by the earthquakes. The availability of both pre- and post- earthquake high-resolution DEMs provide us the opportunity to try new approach to get robust landslide volume information. Here, we propose a new method in landslide volume estimate and tested it in Chuetsu region, where a Mw 6.6 earthquake occurred in 2004. Firstly, we align the DEMs by reconstructing the horizontal difference, then we quantitatively obtained the landslide volume in the epicentral area by differencing the pre- and post-earthquake DEMs. We convert the landslide volume into the distribution of average catchment-scale seismically induced denudation. Our results indicate the preserved topography is not only due to the uplifting caused by fault-related folding on the hangwall of Muikamachi fault, but also undergone erosion caused by the seismically induced landslides. Our findings reveal that Chuetsu earthquake mainly roughens the topography in the Chuetsu region of low elevation. This study also reveal that the differential DEM method is a valuable approach in analyzing landslide volume, as well as quantitative geomorphic analysis.

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