A General Upper Bound on the Size of Constant-Weight Conflict-Avoiding Codes

Conflict-avoiding codes are used in the multiple-access collision channel without feedback. The number of codewords in a conflict-avoiding code is the number of potential users that can be supported in the system. In this paper, a new upper bound on the size of conflict-avoiding codes is proved. This upper bound is general in the sense that it is applicable to all code lengths and all Hamming weights. Several existing constructions for conflict-avoiding codes, which are known to be optimal for Hamming weights equal to four and five, are shown to be optimal for all Hamming weights in general.Comment: 10 pages, 1 figur

Resource Sharing in the Most Regular Scheduling: Deterministic Performance and Guarantee

International audienceProviding performance guarantee is one of the most important issues in a heterogeneous network for a large number of concurrent sessions. A common question in the network control and resource scheduling is how to provide end-to-end delay bounds and offer service guarantees in a relatively distributed manner. In this paper, we will narrow down the question and address specifically on the MRBS multiple access. It supports each user a flexible rate-matched time sharing with efficient resource scheduling. A generalized system modeling and analytical framework is developed based on the techniques of network calculus. The result extends from single-node scheduling to multiple layered scenarios with deterministic performance guarantees. Potential applications are discussed at last

The opportunity recognition framework in the Hong Kong SMEs context

This paper presents a preliminary framework of opportunity recognition in the Hong Kong small and medium enterprises (SMEs) context. Guanxi and four trait variables, namely self-monitoring, extroversion, selfefficacy and creativity are the independent variables while the number of opportunity recognized by entrepreneurs is the dependent variable in the framework. The model indicates a mediation effect of guanxi between self-monitoring and the number of opportunities recognized, and between extroversion and the number of opportunities recognized. Meanwhile, SMEs marketing characteristics are determined by personalities and behaviour of the entrepreneurs as they do not conform to the traditional marketing theories (Gilmore et al., 2001). This paper provides new research directions to the field of SMEs marketing

Fostering equitable access to higher education in Hong Kong : a study of the tertiary financial assistance scheme

published_or_final_versionPolitics and Public AdministrationMasterMaster of Public Administratio

The design and analysis of protocol sequences for robust wireless accessing

International audienceIn this paper, a family of linear congruence sequences with interesting cross-correlation properties is investigated for potential applications in defining new multiple access protocols for distributed wireless systems. One can show that for any finite subset of the sequences with rate sum not exceeding a certain level, there cannot have enough collisions to completely block any particular user no matter how they are shifted with respect to one another. The user un-suppressibility and service guarantee can be exploited in many applications such as wireless sensor or impulse radio systems. To enhance the system's allowable rate sum while possessing the non-blocking property, new protocol sequences are designed. Besides, the throughput shift-invariant property is obtained

Acupuncture for frozen-thawed embryo transfer cycles: A double-blind randomized controlled trial

The role of acupuncture on the pregnancy rate has not been evaluated in frozen-thawed embryo transfer (FET) cycles. This randomized double-blind study aimed to determine whether acupuncture performed on the day of FET improves clinical outcomes. On the day of FET, 226 patients were randomly allocated to either real or placebo acupuncture according to a computergenerated randomization list in sealed opaque envelopes. They received a session of real or placebo acupuncture for 25 min on site immediately after FET. The anxiety level and serum cortisol concentration were evaluated before and after real and placebo acupuncture. There were no significant differences in rates of overall pregnancy, clinical pregnancy, ongoing pregnancy, live birth and implantation in the placebo acupuncture group, when compared with the real acupuncture group. The anxiety level and serum cortisol concentration were similar for both groups. Only the placebo acupuncture group had significantly higher ongoing pregnancy (P = 0.022) and implantation rates (P = 0.038) than those who declined to join the study and received no acupuncture. In conclusion, comparable pregnancy and live birth rates of FET treatment were found in patients who had one session of real or placebo acupuncture after FET. © 2010, Reproductive Healthcare Ltd. Published by Elsevier Ltd. All rights reserved.postprin

Constructions of Robust Protocol Sequences for Wireless Sensor and Ad hoc Networks

International audienceIn this paper, a class of periodic unipolar binary sequences are investigated for their potential applications in defining new protocols for distributed wireless multiple access. Based on linear congruence sequences, one can show that for any finite subset of these sequences with total proportional rate not exceeding a specific threshold, there cannot be enough collisions to completely block any particular sequence, no matter how they are shifted with respect to one another. This property can be exploited in certain applications such as wireless sensor and ad hoc networks. A further investigation on how to enhance the allowable rate sum is carried out. New protocol sequences with interesting and useful properties are designed accordingly

Constant Delivery Delay Protocol Sequences for the Collision Channel Without Feedback

International audienceWe consider a collision channel model without feedback based on a time-slotted communication channel shared by K users. In this model, packets transmitted in the same time slot collide with each other and are unrecoverable. Each user accesses the channel according to an internal periodical pattern called protocol sequence. Due to the lack of feedback, users cannot synchronize their protocol sequences, leading to unavoidable collisions and varying throughput. Protocol sequences that provide constant throughput regardless of delay offsets between users are called shift-invariant (SI), they have been studied and characterized in previous work. We propose a new class of SI sequences: Constant Individual Delivery Delay (CIDD) sequences which ensure that the delay between two successfully delivered packets is constant for each user. We present a characterization of CIDD sequences. We also prove that CIDD sequences can achieve the lower bound of SI sequences period but not the optimal throughput

Baicalein antagonizes rotenone-induced apoptosis in dopaminergic SH-SY5Y cells related to Parkinsonism

<p>Abstract</p> <p>Background</p> <p>Two active compounds, baicalein and its glycoside baicalin were found in the dried root of <it>Scutellaria baicalensis </it>Georgi, and reported to be neuroprotective <it>in vitro </it>and <it>in vivo</it>. This study aims to evaluate the protective effects of baicalein on the rotenone-induced apoptosis in dopaminergic SH-SY5Y cells related to parkinsonism.</p> <p>Methods</p> <p>Cell viability and cytotoxicity were determined by MTT assay. The degree of nuclear apoptosis was evaluated with a fluorescent DNA-binding probe Hoechst 33258. The production of reactive oxidative species (ROS) and loss of mitochondrial membrane potential (ΔΨm) were determined by fluorescent staining with DCFH-DA and Rhodanmine 123, respectively. The expression of Bax, Bcl-2, cleaved caspase-3 and phosphorylated ERK1/2 was determined by the Western blots.</p> <p>Results</p> <p>Baicalein significantly increased viability and decreased rotenone-induced death of SH-SY5Y cells in a dose-dependent manner. Pre- and subsequent co-treatment with baicalein preserved the cell morphology and attenuated the nuclear apoptotic characteristics triggered by rotenone. Baicalein antagonized rotenone-induced overproduction of ROS, loss of ΔΨm, the increased expression of Bax, cleaved caspase-3 and phosphorylated ERK1/2 and the decreased expression of Bcl-2.</p> <p>Conclusion</p> <p>The antioxidative effect, mitochondrial protection and modulation of anti-and pro-apoptotic proteins are related to the neuroprotective effects of baicalein against rotenone induced cell death in SH-SY5Y cells.</p