4,704 research outputs found
Coordinated Multicasting with Opportunistic User Selection in Multicell Wireless Systems
Physical layer multicasting with opportunistic user selection (OUS) is
examined for multicell multi-antenna wireless systems. By adopting a two-layer
encoding scheme, a rate-adaptive channel code is applied in each fading block
to enable successful decoding by a chosen subset of users (which varies over
different blocks) and an application layer erasure code is employed across
multiple blocks to ensure that every user is able to recover the message after
decoding successfully in a sufficient number of blocks. The transmit signal and
code-rate in each block determine opportunistically the subset of users that
are able to successfully decode and can be chosen to maximize the long-term
multicast efficiency. The employment of OUS not only helps avoid
rate-limitations caused by the user with the worst channel, but also helps
coordinate interference among different cells and multicast groups. In this
work, efficient algorithms are proposed for the design of the transmit
covariance matrices, the physical layer code-rates, and the target user subsets
in each block. In the single group scenario, the system parameters are
determined by maximizing the group-rate, defined as the physical layer
code-rate times the fraction of users that can successfully decode in each
block. In the multi-group scenario, the system parameters are determined by
considering a group-rate balancing optimization problem, which is solved by a
successive convex approximation (SCA) approach. To further reduce the feedback
overhead, we also consider the case where only part of the users feed back
their channel vectors in each block and propose a design based on the balancing
of the expected group-rates. In addition to SCA, a sample average approximation
technique is also introduced to handle the probabilistic terms arising in this
problem. The effectiveness of the proposed schemes is demonstrated by computer
simulations.Comment: Accepted by IEEE Transactions on Signal Processin
Size-dependent endocytosis of gold nanoparticles studied by three-dimensional mapping of plasmonic scattering images
<p>Abstract</p> <p>Background</p> <p>Understanding the endocytosis process of gold nanoparticles (AuNPs) is important for the drug delivery and photodynamic therapy applications. The endocytosis in living cells is usually studied by fluorescent microscopy. The fluorescent labeling suffers from photobleaching. Besides, quantitative estimation of the cellular uptake is not easy. In this paper, the size-dependent endocytosis of AuNPs was investigated by using plasmonic scattering images without any labeling.</p> <p>Results</p> <p>The scattering images of AuNPs and the vesicles were mapped by using an optical sectioning microscopy with dark-field illumination. AuNPs have large optical scatterings at 550-600 nm wavelengths due to localized surface plasmon resonances. Using an enhanced contrast between yellow and blue CCD images, AuNPs can be well distinguished from cellular organelles. The tracking of AuNPs coated with aptamers for surface mucin glycoprotein shows that AuNPs attached to extracellular matrix and moved towards center of the cell. Most 75-nm-AuNPs moved to the top of cells, while many 45-nm-AuNPs entered cells through endocytosis and accumulated in endocytic vesicles. The amounts of cellular uptake decreased with the increase of particle size.</p> <p>Conclusions</p> <p>We quantitatively studied the endocytosis of AuNPs with different sizes in various cancer cells. The plasmonic scattering images confirm the size-dependent endocytosis of AuNPs. The 45-nm-AuNP is better for drug delivery due to its higher uptake rate. On the other hand, large AuNPs are immobilized on the cell membrane. They can be used to reconstruct the cell morphology.</p
THE STRATEGY OF MUSCULAR PRE-TENSION DURING INITIAL BLOCK PHASE IN SWIMMING GRAB START
The purpose of this study was to examine the effects of muscular pre-tension on swimming grab start performance. Eight well-trained subjects participated in this study. They were instructed to perform three strategies (stretch-shortening cycle, purely concentric with and with no muscular pre-tension) in grab start. Two Peak-Performance high-speed video cameras operating at 120 Hz and one Kistler force plate (600 Hz) mounted on the starting block were synchronized to collect the data. The results showed that the block time was significantly shorter and horizontal velocity of taking off was larger in muscular pre-tension than in stretch-shortening cycle strategy. Based on the results of the present study, it has been suggested that using muscular pre-tension strategy during initial block phase in grab start could add some benefits of decreasing time
Regulation of Skp2 Expression and Activity and Its Role in Cancer Progression
The regulation of cell cycle entry is critical for cell proliferation and tumorigenesis. One of the key players regulating cell cycle progression is the F-box protein Skp2. Skp2 forms a SCF complex with Skp1, Cul-1, and Rbx1 to constitute E3 ligase through its F-box domain. Skp2 protein levels are regulated during the cell cycle, and recent studies reveal that Skp2 stability, subcellular localization, and activity are regulated by its phosphorylation. Overexpression of Skp2 is associated with a variety of human cancers, indicating that Skp2 may contribute to the development of human cancers. The notion is supported by various genetic mouse models that demonstrate an oncogenic activity of Skp2 and its requirement in cancer progression, suggesting that Skp2 may be a novel and attractive therapeutic target for cancers
One-Fe versus Two-Fe Brillouin Zone of Fe-Based Superconductors: Creation of the Electron Pockets via Translational Symmetry Breaking
We investigate the physical effects of translational symmetry breaking in
Fe-based high-temperature superconductors due to alternating anion positions.
In the representative parent compounds, including the newly discovered
Fe-vacancy-ordered , an unusual change of orbital
character is found across the one-Fe Brillouin zone upon unfolding the
first-principles band structure and Fermi surfaces, suggesting that covering a
larger one-Fe Brillouin zone is necessary in experiments. Most significantly,
the electron pockets (critical to the magnetism and superconductivity) are
found only created with the broken symmetry, advocating strongly its full
inclusion in future studies, particularly on the debated nodal structures of
the superconducting order parameter.Comment: Accepted by Physical Review Letters. Updated in Figure 2 and
supplementary informatio
Adaptive circular enclosure colour distribution geometrical model utilizing point-in-polygon for segregation between lips and skin pixels
This paper is inspired from various boundary determination techniques which are used for segregating colours between background, skin and lips. Basic concept for this technique is based on colour segmentation with CIELAB colourspace
utilized for justifiable reasons. Using LAB colour-space, lips colours were compiled into a colour-map and processed
accordingly to our proposed algorithm of adaptive circular
enclosure. Algorithm output was determined as a series of
coordinates symbolizing boundary values surrounding colourmap. Separation of colours is based on these boundaries by creating a freeform polygon that defines if colour-value either belongs within colour-boundary polygon or not. This technique is famously known as the point in-polygon technique. Proposed technique evaluation uses XM2VTS database based on false positive and false-negative to compute segmentation error. Simulation shows proposed algorithm yields segmented error of 5.55% with accuracy of 94.45%
Effect on Spasticity After Performance of Dynamic-Repeated-Passive Ankle Joint Motion Exercise in Chronic Stroke Patients
Spasticity associated with abnormal muscle tone is a common motor disorder following stroke, and the spastic ankle may affect ambulatory function. The purpose of this study was to investigate the short-term effect of dynamic-repeated-passive ankle movements with weight loading on ambulatory function and spastic hypertonia of chronic stroke patients. In this study, 12 chronic stroke patients with ankle spasticity and inefficient ambulatory ability were enrolled. Stretching of the plantar-flexors of the ankle in the standing position for 15 minutes was performed passively by a constant-speed and electrically powered device. The following evaluations were done before and immediately after the dynamic-repeated-passive ankle movements. Spastic hypertonia was assessed by the Modified Ashworth Scale (MAS; range, 0–4), Achilles tendon reflexes test (DTR; range, 0–4), and ankle clonus (range, 0–5). Improvement in ambulatory ability was determined by the timed up-and-go test (TUG), the 10-minute walking test, and cadence (steps/minute). In addition, subjective experience of the influence of ankle spasticity on ambulation was scored by visual analog scale (VAS). Subjective satisfaction with the therapeutic effect of spasticity reduction was evaluated by a five-point questionnaire (1 = very poor, 2 = poor, 3 = acceptable, 4 = good, 5 = very good). By comparison of the results before and after intervention, these 12 chronic stroke patients presented significant reduction in MAS and VAS for ankle spasticity, the time for TUG and 10-minute walking speed (p < 0.01). The cadence also increased significantly (p < 0.05). In addition, subjective satisfaction with the short-term therapeutic effect was mainly good (ranging from acceptable to very good). In conclusion, 15 minutes of dynamic-repeated-passive ankle joint motion exercise with weight loading in the standing position by this simple constant-speed machine is effective in reducing ankle spasticity and improving ambulatory ability
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