Multicast Routing Algorithms and Failure Analyses for Low Earth Orbit Satellite Communication Networks

In the rapidly changing environment of mobile communications, the importance of the mobile satellite (e,g,, low earth orbit satellites (LEOsats)) networks will increase due to their global visibility and connection. Multicasting is an effective communication method in terms of frequency spectrum usage for a LEO network. It is devised to provide lower network traffic (i,e,, one-to-many transmissions). This research examines the system performance of two dissimilar terrestrially-based multicasting protocols: the Distance Vector Multicast Routing Protocol (DVMRP) and the On Demand Multicast Routing Protocol (ODMRP). These two protocols are simulated in large group membership density and in the presence of satellite failures. Two different algorithms are developed and used to select critical satellites for degrading a LEO network constellation. The simulation results show that the ODMRP protocol successfully reconfigured routes in large group membership density areas and in satellite failure conditions. Results also show that the ODMRP provided reliable packet delivery. However, ODMRP showed an enormous end-to-end delay in severe satellite failure conditions. This result is attributable to the delayed route refreshing procedure of ODMRP. In contrast, the DVMRP suffered from broken routes and complexity in the large group membership density and in satellite failure conditions. It had a smaller packet delivery ratio than the ODMRP (approximately 85,5% versus 98,9% for the 80 user case). The DVMRP showed scalable and stable end-to-end delay under multiple failed satellite conditions. The large group membership density and the multiple satellite failure conditions provide a more complete assessment for these two protocols

The Nature of be in the Interlanguage Representation of L1 Chinese Learners of L2 English

The interlanguage (IL) representations of be in second language acquisition (SLA) research have received different treatments. To some linguists, be in morphological tense forms is considered to be the easiest morpheme to acquire because it is in a local head-complement relation, taking it as a local-relation marker. Researchers have also strived to explain why be in periphrastic tense constructions is usually used by L2 learners to passivize unaccusative verbs, treating it as a pseudo-passive marker. They assume that it is probably due to incomplete acquisition of lexical properties of unaccusative verbs that makes L2 learners explicitly mark the logical object in the formal subject position with non-native auxiliary be. This study refutes the above claims by adopting Ouhalla’s analysis to give an alternative treatment to the nature of IL representations of be. Within the Principles and Parameters framework, Ouhalla (1991) postulates that be is an expletive in both morphological and periphrastic tense constructions, which has no argument structure and functions to formally hold the place of the empty Inflection node. Therefore, the study proposes that the nature of IL representations of be is an I-supporter to help instantiate I, which is stranded in non-verbal predicates, and in situations where the categorial nature of the verb becomes nominal after being joined with a nominal functional head. Therefore, be in a periphrastic tense form, which is the [be+V] complex, is hypothesized to be used to non-natively mark perfective aspectual contexts. By refuting that be is a local-relation marker, the study assumes that L2 learners could never easily acquire be-support of the Modal phrase, which is also in a local head-complement relation as with copula be and auxiliary be. In order to rebut be as a pseudo-passive marker which is mostly associated with unaccusatives, the study assumes that L2 learners will still accept the IL [be+V] complex even when the formal subject position is occupied by a logical subject, the thematic verb is either transitive or unergative in categorical nature, and the bound morpheme attached to the verb is either one of the bound morphemes –s, -ed, –en or ∅. A hundred and thirty-four subjects, who are undergraduates of B. A. (Mandarin) at Universiti Putra Malaysia, participated in an Acceptability Judgement Test and fifteen of them in an Elicited Translation Task. The findings show that although the L1 Chinese learners of L2 English have acquired be in non-verbal predicates, they have difficulty in acquiring be-support of Modal phrases. Furthermore, the subjects accepted and produced the IL [be+V] complex even when the formal subject of the sentence is a logical subject, the thematic verb is either transitive or unergative in categorical nature, and they attached one of the bound morphemes –s, -ed, –en, or ∅ to the verb in the complex. In sum, the findings of the study suggest that the claims that be in morphological tense forms is a local-relation marker, and be in periphrastic tense forms is a pseudo-passive marker can be refuted. It is argued that the subjects are able to reset the [±overt] feature specification of I instantiation from [-overt] in Chinese to [+overt] in English. Furthermore, they have no problem mapping the [+overt] feature to the morphological form of I-supporter be in morphological tense constructions. However, when there is an added layer of Aspect categorial feature, the subjects encounter difficulties realizing the [+V] feature specification of perfective aspect element, and mapping it onto the morphological form have. Rather, they take the Asp element to be nominal, and unconsciously realizing that I is stranded, they instantiate I with the I-supporter be. In conclusion, the nature of be in IL representations of L1 Chinese learners of L2 English is an I-supporter which helps instantiate stranded I in both morphological and periphrastic tense constructions as postulated by Ouhalla (1991)

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Should young age be a contra-indication to breast conservation treatment in Chinese women? Twelve-year experience from a public cancer centre in Hong Kong

Objective: It has been proposed that young women should not be treated by breast conservation treatment because of a higher risk of local recurrences and worse survival. We therefore examined whether breast conservation treatment in young Chinese women yielded inferior clinical outcomes compared to modified radical mastectomy. Design: Retrospective study. Setting: Clinical oncology department in a public hospital in Hong Kong. Patients: A total of 258 Chinese women with invasive breast cancer, aged below 40 years, and referred between January 1994 and July 2006. Results: A total of 124 (48%) and 134 (52%) patients were treated by breast conservation treatment and modified radical mastectomy, respectively. Mastectomy patients tended to have larger primary tumours (P<0.001) and more nodal involvement (P<0.001). At a median follow-up of 6.5 years, there was no significant difference in the local failure-free survival rate (92% vs 93%, P=0.324) and loco-regional failure-free survival rate (89% vs 88%, P=0.721) in patients having breast conservation treatment and mastectomy. Probably due to their earlier presentation with disease, the former actually had better 6-year distant failure-free survival (88% vs 71%, P=0.002) and overall survival (92% vs 81%, P=0.173) rates. Multivariate analyses showed that both the resection margin status (hazard ratio=2.77, P=0.050) and the presence of peritumoural vascular invasion (hazard ratio=3.01, P=0.038) were independent predictors of local recurrence; the nodal status (hazard ratio=3.91, P<0.001) was the only predictive factor for overall survival. The choice of breast conservation treatment (vs modified radical mastectomy) had no apparent adverse impact on all the clinical outcome parameters analysed. Conclusion: Breast conservation treatment is a reasonable option for many suitably selected young Chinese women.published_or_final_versio

Enhanced magnetic response of fluids using self-assembled petal-like iron oxide particles

Using self-assembled iron oxide (SAIO) particles with petal-like morphology, aqueous fluids containing magnetic particles were prepared and the effect of hierarchical particle surface on the viscoelasticity under magnetic was investigated. The fluids consisting of self-assembled iron oxide particles exhibit highly tunable viscoelasticity which is controlled by applying external magnetic field. A difference between SAIO particles and spherical particles is explained by the fact that surface features of the self-assembled particles increased the network strength between particles in the fluids. © 2010 American Institute of Physics

HER2 overexpression of breast cancers in Hong Kong: Prevalence and concordance between immunohistochemistry and in-situ hybridisation assays

Objectives: To evaluate the prevalence of human epidermal growth factor receptor 2 (HER2) gene overexpression in breast cancer patients encountered in Hong Kong and the concordance of HER2 findings from primary immunohistochemistry assays and confirmatory in-situ hybridisation assays. Design: Retrospective study. Setting: Department of Clinical Oncology in a public hospital in Hong Kong. Patients: All patient referrals between July 2006 and June 2007 with newly diagnosed invasive breast cancer (for prevalence evaluation), and all patients treated at our unit with confirmatory in-situ hybridisation tests performed within the study period (for concordance evaluation). Results: There were 272 consecutive breast cancer patients eligible for prevalence evaluation. The distribution for immunohistochemistry staining in 249 cases for scores 0, 1+, 2+, and 3+ were 99 (40%), 40 (16%), 58 (23%), and 52 (21%) respectively. In the remaining 23 patients, four and 19 breast cancers were unscored and reported by immunohistochemistry to be HER2-positive and -negative, respectively. The overall HER2 overexpression rate (3+ or reported as positive) was 21%. HER2 overexpression was associated with grade 3 histology (P<0.001) and negative hormonal receptor status (P<0.001). However, it was not associated with age (P=0.525), T-classification (P=0.740), N-classification (P=0.691), nor group stages (P=0.433). Of the 37 patients with confirmatory in-situ hybridisation tests performed, 10 (71%) of 14 with immunohistochemistry staining of 3+ and 1 (4%) of 23 with immunohistochemistry staining of 2+ were found to have HER2 gene amplification. Conclusions: More than 25% of HER2 overexpression identified by immunohistochemistry assays in this Hong Kong cohort could not be verified by confirmatory in-situ hybridisation assays. Compliance with the latest guidelines for HER2 testing should improve the future accuracy and concordance.published_or_final_versio

The Specific Characteristics in Children with Obstructive Sleep Apnea and Cor Pulmonale

Background. The prevalence of obstructive sleep apnea (OSA) in the pediatric population is currently estimated at 1-2% of all children. The purpose of this study was to investigate the clinical and hemodynamic characteristics in pediatric patients with cor pulmonale and OSA. Methods. Thirty children with the diagnosis of OSA were included. These patients consisted of 26 male and 4 female children with a mean age of 7 ± 4 years old. Five of those children were found to be associated with cor pulmonale, and 25 had OSA but without cor pulmonale. Results. The arousal index was much higher in children with OSA and cor pulmonale. The children with OSA and cor pulmonale had much lower mean and minimal oxygen saturation and a higher incidence of bradycardia events. All 5 patients with OSA and cor pulmonale underwent an adenotonsillectomy, and the pulmonary arterial pressure dropped significantly after the surgery. Conclusion. This study demonstrated that the OSA pediatric patients with cor pulmonale had the different clinical manifestations and hemodynamic characteristics from those without cor pulmonale. The adenotonsillectomy had excellent results in both the OSA pediatric patients with and without cor pulmonale

The Effect of Pravastatin on Intima Media Thickness of the Carotid Artery in Patients with Normal Cholesterol

AbstractObjectiveCarotid intima media thickness (IMT) is a good indicator of the severity of atherosclerotic disease. Statins have been found to reduce carotid IMT in patients with hypercholesterolaemia. The aim of this study was to investigate if pravastatin is effective in reducing IMT in normocholesterolaemic patients with carotid artery disease.MethodsPatients with carotid artery stenosis and normal cholesterol levels who were not on a statin, were recruited. Patients were randomised to receive pravastatin or placebo daily. Serum concentration of cholesterol and IMT of common carotid arteries were measured before randomisation and at 3 monthly intervals thereafter, for 9 months. IMT was analysed to give the mean of a standardised 2cm of the common carotid artery (CCA). Results are expressed as median (IQR) and comparison made using the Wilcoxon signed ranks test.ResultsFifty-four patients were examined. Twenty-eight patients were randomised to active treatment. There was no difference in demographic details and co-morbid states between the two groups. A significant reduction in cholesterol concentration was observed from 3 months in patients randomised to the pravastatin group [5.14(4.72–5.88) vs. 4.11(3.44–5.33), p<0.05], while there was also a significant decrease in combined IMT form 6 months [1.53(1.36–1.87) vs. 1.41 (1.33–1.78), p<0.05].ConclusionsThe results demonstrate that pravastatin reduces intima media thickness of the common carotid artery in normocholesterolaemic patients with moderate carotid stenosis