LDPC Code Design for the BPSK-constrained Gaussian Wiretap Channel

A coding scheme based on irregular low-density parity-check (LDPC) codes is proposed to send secret messages from a source over the Gaussian wiretap channel to a destination in the presence of a wiretapper, with the restriction that the source can send only binary phase-shift keyed (BPSK) symbols. The secrecy performance of the proposed coding scheme is measured by the secret message rate through the wiretap channel as well as the equivocation rate about the message at the wiretapper. A code search procedure is suggested to obtain irregular LDPC codes that achieve good secrecy performance in such context.Comment: submitted to IEEE GLOBECOM 2011 - Communication Theory Symposiu

Irreducible representations of the symmetric groups from slash homologies of p-complexes

In the 40s, Mayer introduced a construction of (simplicial) $p$-complex by using the unsigned boundary map and taking coefficients of chains modulo $p$. We look at such a $p$-complex associated to an $(n-1)$-simplex; in which case, this is also a $p$-complex of representations of the symmetric group of rank $n$ - specifically, of permutation modules associated to two-row compositions. In this article, we calculate the so-called slash homology - a homology theory introduced by Khovanov and Qi - of such a $p$-complex. We show that every non-trivial slash homology group appears as an irreducible representation associated to two-row partitions, and how this calculation leads to a basis of these irreducible representations given by the so-called $p$-standard tableaux.Comment: 16 pages, 2 figures. Rewritten the proof of first theorem. Substantial rearrangement of materials in other sections. Comments welcome

Efficient recursion termination for function-free horn logic

We present an efficient scheme to terminate infinite recursion in function-free Horn logic. In [BW84], Brough and Walker show that a preorder linear resolution with a goal termination strategy is incomplete, i.e. it must miss some answers. Their theory is true if left-recursion is allowed. The crucial assumption underlying Brough and Walker's theory is that the order of literals in a clause should not be altered. This assumption, however, is not necessary in programs that do not contain any extra-logical features such as the 'cut' symbol of Prolog. This is because the order of literals does not affect the correctness of such programs, only their efficiency. In this paper, we show that left-recursion can always be eliminated. The idea is to transform loops of the input set into safe loops, that are left-recursion free. Consequently, the goal termination strategy guarantees to always terminate properly with all possible answers; thus, it is complete in the domain of safe loops. We further show that all rules in a safe loop can be transformed into rules that begin with a base literal. This permits the implementation of a simple scheme to carry out the goal termination strategy more efficiently. The basic idea of this scheme is to distribute the history containing all executed goals over assertions, rather than maintaining it as a centralized data structure. This reduces the amount of work performed during execution

Relationship between age and peripapillary retinal nerve fibre layer thickness: An optical coherence tomography study

Objective: To evaluate the relationship between age and peripapillary retinal nerve fibre layer thickness in healthy Chinese subjects. Design: Cross-sectional study. Setting: Regional hospital, Hong Kong. Participants: Healthy volunteers (n=218) of Chinese ethnicity with spherical equivalent of -6 to +4 dioptres were recruited for study from October 2001 to March 2003. Ocular examination was carried out and measurements of peripapillary retinal nerve fibre layer thickness were performed using optical coherence tomography (Carl Zeiss Humphrey OCT 2 machine), in a circular pattern of 3.4 mm diameter, centred on the optic disc. Main outcome measures: Mean retinal nerve fibre layer thickness and age. Results: The mean age was 40 (standard deviation, 17; range, 11-69) years. The mean peripapillary retinal nerve fibre layer thickness was 111.6 (standard deviation, 18.5; range, 52.0-155.0) μm. Age correlated significantly with peripapillary retinal nerve fibre layer thickness (r= -0.28, P<0.0001). Conclusion: Mean peripapillary retinal nerve fibre layer thickness (based on optical coherence tomography) correlates negatively with age, which can interfere with the assessment and monitoring of glaucoma patients. An age-adjusted normogram may be necessary to interpret results.published_or_final_versio

Drug wastage among the elderly living in old aged homes in Hong Kong

The extend of drug wastage among elderly living in old aged homes was never investigated. Upon the completion of the previous study on pharmaceutical services provided to elderly living in old aged homes, the amount of drugs wasted from 3,020 residents in one of the delegated pharmacies over a 4-month period were counted and their costs were calculated. The total cost of wasted drugs amounted to be HKD$96,924, with drugs acting on the central nervous system contributed to the highest cost of HKD$26,872 (27.7%), followed by respiratory drugs of HKD$23,875 (24.6$22,965 (23.7%). The results showed that for health institutes dispensing prescriptions of long duration to the elderly could lead to considerable amount of drug wastage and this issue should be addressed.link_to_subscribed_fulltex

Performance analysis of a message-oriented knowledge-base

First-order Horn logic is a useful formalism to design knowledge-based systems. When implemented on a sequential von Neumann computer, the main limitation of such systems is performance. We present a message-driven model for function-free Horn logic, where the knowledge base is represented as a network of logical processing elements communicating with one another exclusively through messages. The lack of centralized control and centralized memory makes this model suitable to implementation on a highly-parallel asynchronous computer architecture.The primary contribution of this paper is a performance analysis of this message-driven system and a comparison with a sequential resolution scheme using backtracking. For both approaches, closed form expressions for the performance results are derived and compared

Prospect and Markowitz Stochastic Dominance

Levy and Levy (2002, 2004) develop the Prospect and Markowitz stochastic dominance theory with S-shaped and reverse S-shaped utility functions for investors. In this paper, we extend Levy and Levy's Prospect Stochastic Dominance theory (PSD) and Markowitz Stochastic Dominance theory (MSD) to the first three orders and link the corresponding S-shaped and reverse S-shaped utility functions to the first three orders. We also provide experiments to illustrate each case of the MSD and PSD to the first three orders and demonstrate that the higher order MSD and PSD cannot be replaced by the lower order MSD and PSD. Prospect theory has been regarded as a challenge to the expected utility paradigm. Levy and Levy (2002) prove that the second order PSD and MSD satisfy the expected utility paradigm. In our paper we take Levy and Levy's results one step further by showing that both PSD and MSD of any order are consistent with the expected utility paradigm. Furthermore, we formulate some other properties for the PSD and MSD including the hierarchy that exists in both PSD and MSD relationships; arbitrage opportunities that exist in the first orders of both PSD and MSD; and that for any two prospects under certain conditions, their third order MSD preference will be ???the opposite??? of or ???the same??? as their counterpart third order PSD preference. By extending Levy and Levy's work, we provide investors with more tools for empirical analysis, with which they can identify the first order PSD and MSD prospects and discern arbitrage opportunities that could increase his/her utility as well as wealth and set up a zero dollar portfolio to make huge profit. Our tools also enable investors to identify the third order PSD and MSD prospects and make better choices.Prospect stochastic dominance, Markowitz stochastic dominance, risk seeking, risk averse, S-shaped utility function, reverse S-shaped utility function

The pharmaceutical services to the elderly in the old aged homes in Hong Kong: a scope exercise

Various models of pharmaceutical services have been provided by pharmacists to old aged home residents, however, these models have never been summarised and compared. The aim of this scoping exercise is to identify different kinds of pharmaceutical services currently available to the old aged home residents, by means of systemic literature review, qualitative in-depth interviews with service providers in order to understand their models and qualitative semi-structured interviews with non-pharmaceutical service users in an attempt to investigate reasons why some homes do not subscribe to these services. The results showed that none of the pharmaceutical services currently available can uproot the causes of medication errors, and there is a need to elaborate the roles of pharmacists in a primary care setting.link_to_subscribed_fulltex