2,438 research outputs found
Spin Sum Rules at Low
Recent precision spin-structure data from Jefferson Lab have significantly
advanced our knowledge of nucleon structure at low . Results on the
neutron spin sum rules and polarizabilities in the low to intermediate
region are presented. The Burkhardt-Cuttingham Sum Rule was verified within
experimental uncertainties. When comparing with theoretical calculations,
results on spin polarizability show surprising disagreements with Chiral
Perturbation Theory predictions. Preliminary results on first moments at very
low are also presented.Comment: 4 pages, to be published in the Proceedings of the 10th Conference on
Intersections of Nuclear and Particle Physics (CIPANP
Phase transition in site-diluted Josephson junction arrays: A numerical study
We numerically investigate the intriguing effects produced by random
percolative disorder in two-dimensional Josephson-junction arrays. By dynamic
scaling analysis, we evaluate critical temperatures and critical exponents with
high accuracy. It is observed that, with the introduction of site-diluted
disorder, the Kosterlitz-Thouless phase transition is eliminated and evolves
into a continuous transition with power-law divergent correlation length.
Moreover, genuine depinning transition and creep motion are studied, evidence
for distinct creep motion types is provided. Our results not only are in good
agreement with the recent experimental findings, but also shed some light on
the relevant phase transitions.Comment: 7 pages, 8 figures, Phys. Rev. B (in press
Study on the collision-mechanical properties of tomatoes gripped by harvesting robot fingers
The data of collision-mechanical property of tomatoes gripped by robot fingers are important for the gripping control of tomato harvesting robot. In the study, tests of controlling the fingers to grip tomatoes were conducted to ascertain the effects of input current, motor speed and impact positions on the impact force of fingers and maximum deformation of tomatoes. The input current of the motor ranged from 1200 to 2100 mA, the motor speed from 25 to 3000 rpm and the three impact positions as follows, 1 (radial arm), 2 (sloping at an angle of 22.5° to the radial arm) and 3 (sloping at an angle of 45° to the radial arm). The results shown that under the condition of the same motor speed and inputcurrent, the peak impact force on the radial arm, compared with other impact positions, was maximum, the deformation of tomato was the smallest and the degree of mechanical damage was the lowest too.Under different speed and input current conditions, when the fingers grip the tomato on the radial arm, the peak force of fingers and the maximum deformation of tomatoes were highly influenced by the motor speed and input current, especially the input current. The peak impact force and the maximum deformation of the tomato increased respectively with increase in the motor speed and input current and these followed cubic polynomial regression equations
Atomic Scale Sliding and Rolling of Carbon Nanotubes
A carbon nanotube is an ideal object for understanding the atomic scale
aspects of interface interaction and friction. Using molecular statics and
dynamics methods different types of motion of nanotubes on a graphite surface
are investigated. We found that each nanotube has unique equilibrium
orientations with sharp potential energy minima. This leads to atomic scale
locking of the nanotube.
The effective contact area and the total interaction energy scale with the
square root of the radius. Sliding and rolling of nanotubes have different
characters. The potential energy barriers for sliding nanotubes are higher than
that for perfect rolling. When the nanotube is pushed, we observe a combination
of atomic scale spinning and sliding motion. The result is rolling with the
friction force comparable to sliding.Comment: 4 pages (two column) 6 figures - one ep
Counting Rule for Hadronic Light-Cone Wave Functions
We introduce a systematic way to write down the Fock components of a hadronic
light-cone wave function with partons and orbital angular momentum
projection . We show that the wave function amplitude
has a leading behavior
when all parton transverse
momenta are uniformly large, where and are the number of partons
and orbital angular momentum projection, respectively, of an amplitude that
mixes under renormalization. The result can be used as a constraint in modeling
the hadronic light-cone wave functions. We also derive a generalized counting
rule for hard exclusive processes involving parton orbital angular momentum and
hadron helicity flip.Comment: 7 pages, no figur
Antibacterial Mechanism of the Ehyl Acetate Extracts From Naked Oat Again Bacillus Subtilis
The antibacterial mechanism of the ethyl acetate extracts from naked oat against Bacillus subtilis were studied in this paper based on assays such as cell wall alkaline phosphatase (AKP), permeability and integrity of cell membrane as well as electron microscopy observations. The results showed that the ethyl acetate extracts had significant effects on AKP, permeability and integrity of cell membrane. We concluded that the mechanism of action of the ethyl acetate extracts against B. subtilis might be described as:Acting on cell wall and membrane, resulting in disruption, cell lysis, and the leakage of intracellular constituents according to the results of AKP, the leakage of electrolytes, the losses of contents (proteins, reducing sugars and 260 nm absorbing materials) assays and electron microscopy observations. Overall, the results clearly indicated that the ethyl acetate extracts from naked oat was potential to control the contamination of foods caused by bacterial disease
An experimental observation of geometric phases for mixed states using NMR interferometry
Examples of geometric phases abound in many areas of physics. They offer both
fundamental insights into many physical phenomena and lead to interesting
practical implementations. One of them, as indicated recently, might be an
inherently fault-tolerant quantum computation. This, however, requires to deal
with geometric phases in the presence of noise and interactions between
different physical subsystems. Despite the wealth of literature on the subject
of geometric phases very little is known about this very important case. Here
we report the first experimental study of geometric phases for mixed quantum
states. We show how different they are from the well understood, noiseless,
pure-state case.Comment: 4 pages, 3 figure
A novel quantum key distribution scheme with orthogonal product states
The general conditions for the orthogonal product states of the multi-state
systems to be used in quantum key distribution (QKD) are proposed, and a novel
QKD scheme with orthogonal product states in the 3x3 Hilbert space is
presented. We show that this protocol has many distinct features such as great
capacity, high efficiency. The generalization to nxn systems is also discussed
and a fancy limitation for the eavesdropper's success probability is reached.Comment: 4 Pages, 3 Figure
Apparent source levels and active communication space of whistles of free-ranging Indo-Pacific humpback dolphins (Sousa chinensis) in the Pearl River Estuary and Beibu Gulf, China
Grants for this study was provided by the National Natural Science Foundation (NNSF) of China (Grant No.31070347), the Ministry of Science and Technology of China (Grant No. 2011BAG07B05-3), the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. KSCX2-EW-Z-4) and the Special Fund for Agro-scientific Research in the Public Interest of the Ministry of Agriculture of China (Grant No. 201203086) to DW, the State Oceanic Administration of China (Grant No. 201105011-3) and NNSF of China (Grant No. 31170501) to KXW and the China Scholarship Council (Grant No. (2014)3026) to ZTW.Background . Knowledge of species-specific vocalization characteristics and their associated active communication space, the effective range over which a communication signal can be detected by a conspecific, is critical for understanding the impacts of underwater acoustic pollution, as well as other threats. Methods. We used a two-dimensional cross-shaped hydrophone array system to record the whistles of free-ranging Indo-Pacific humpback dolphins (Sousa chinensis) in shallow-water environments of the Pearl River Estuary (PRE) and Beibu Gulf (BG), China. Using hyperbolic position fixing, which exploits time differences of arrival of a signal between pairs of hydrophone receivers, we obtained source location estimates for whistles with good signal-to-noise ratio (SNR ≥ 10 dB) and not polluted by other sounds and back-calculated their apparent source levels (ASL). Combining with the masking levels (including simultaneous noise levels, masking tonal threshold, and the Sousa auditory threshold) and the custom made site-specific sound propagation models, we further estimated their active communication space (ACS). Results. Humpback dolphins produced whistles with average root-mean-square ASL of 138.5 ± 6.8 (mean ± standard deviation) and 137.2 ± 7.0 dB re 1 µPa in PRE (N = 33) and BG (N = 209), respectively. We found statistically significant differences in ASLs among different whistle contour types. The mean and maximum ACS of whistles were estimated to be 14.7 ± 2.6 (median ± quartile deviation) and 17.1 ± 3.5 m in PRE, and 34.2 ± 9.5 and 43.5 ±12.2 m in BG. Using just the auditory threshold as the masking level produced the mean and maximum ACSat of 24.3 ± 4.8 and 35.7 ± 4.6 m for PRE, and 60.7 ± 18.1 and 74.3 ± 25.3 m for BG. The small ACSs were due to the high ambient noise level. Significant differences in ACSs were also observed among different whistle contour types. Discussion. Besides shedding some light for evaluating appropriate noise exposure levels and information for the regulation of underwater acoustic pollution, these baseline data can also be used for aiding the passive acoustic monitoring of dolphin populations, defining the boundaries of separate groups in a more biologically meaningful way during field surveys, and guiding the appropriate approach distance for local dolphin-watching boats and research boat during focal group following.Publisher PDFPeer reviewe
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