Combinatorial Bounds and Characterizations of Splitting Authentication Codes

We present several generalizations of results for splitting authentication codes by studying the aspect of multi-fold security. As the two primary results, we prove a combinatorial lower bound on the number of encoding rules and a combinatorial characterization of optimal splitting authentication codes that are multi-fold secure against spoofing attacks. The characterization is based on a new type of combinatorial designs, which we introduce and for which basic necessary conditions are given regarding their existence.Comment: 13 pages; to appear in "Cryptography and Communications

Conflict, collusion and corruption in small-scale gold mining: Chinese miners and the state in Ghana

With the hike in gold prices from 2008 onwards, tens of thousands of foreign miners, especially from China, entered into the small-scale mining sector in Ghana, despite it being ‘reserved for Ghanaian citizens’ by law. An astonishing free-for-all ensued in which Ghanaian and Chinese miners engaged in both contestation and collaboration over access to gold, a situation described as ‘out of control’ and ‘a culture of impunity’. Where was the state? This paper addresses the question of how and why this phenomenon of pervasive and illicit foreign involvement in small-scale gold mining was able to occur without earlier intervention from the state. Findings indicate that the state was not in fact absent. Foreign miners were able to operate with impunity precisely because they were protected by those in authority, i.e. public officials, politicians and chiefs, in return for private payments. Attempting to explain why various state institutions failed in their responsibilities leads to reflection about the nature of the contemporary state in Ghana. It is concluded that the informality and corruption characteristic of neopatrimonialism remains predominant over legal-rational structures, albeit in a form that has adapted to neoliberal restructuring by an increased orientation towards accessing private sector resources and individual wealth accumulation. Public office remains a means of private enrichment rather than public service. Such findings cast a shadow over the state and government in Ghana, and tarnish its celebration as a model of democratic governance for Africa

Security and Privacy Issues in Wireless Mesh Networks: A Survey

This book chapter identifies various security threats in wireless mesh network (WMN). Keeping in mind the critical requirement of security and user privacy in WMNs, this chapter provides a comprehensive overview of various possible attacks on different layers of the communication protocol stack for WMNs and their corresponding defense mechanisms. First, it identifies the security vulnerabilities in the physical, link, network, transport, application layers. Furthermore, various possible attacks on the key management protocols, user authentication and access control protocols, and user privacy preservation protocols are presented. After enumerating various possible attacks, the chapter provides a detailed discussion on various existing security mechanisms and protocols to defend against and wherever possible prevent the possible attacks. Comparative analyses are also presented on the security schemes with regards to the cryptographic schemes used, key management strategies deployed, use of any trusted third party, computation and communication overhead involved etc. The chapter then presents a brief discussion on various trust management approaches for WMNs since trust and reputation-based schemes are increasingly becoming popular for enforcing security in wireless networks. A number of open problems in security and privacy issues for WMNs are subsequently discussed before the chapter is finally concluded.Comment: 62 pages, 12 figures, 6 tables. This chapter is an extension of the author's previous submission in arXiv submission: arXiv:1102.1226. There are some text overlaps with the previous submissio

Mind the gap? Civil society policy engagement and the pursuit of gender justice: critical discourse analysis of the implementation of the Beijing Declaration and Platform for Action in Africa 2003–2015

This article presents critical discourse analysis of state and civil society organisations’ efforts to implement the gender mainstreaming goals set out in the United Nations’ Beijing Declaration. It is argued that the latter represents a generational opportunity to apply a Feminist Political Economic Framework to development in Africa. However, the research findings show how current practice falls short of the sought-after participative democratic model of mainstreaming. Instead, analysis reveals significant differences in state and civil society organisations’ policy framing, issues over conceptual clarity and a disjuncture in state and civil society prioritisation of key gendered issues such as poverty, economic inequality and conflict resolution. This matters because it indicates that the capacity of the civil sphere to act as a political arena from which NGOs may challenge the traditionally male-dominated power structures is being undermined by a ‘disconnect’ between state and civil society as they pursue contrasting agendas

Immune microenvironment dynamics in breast cancer during pregnancy: impact of gestational age on tumor-infiltrating lymphocytes and prognosis

Background: Breast cancer during pregnancy (PrBC) is a rare condition known for its aggressive clinical behavior. The presence of tumor-infiltrating lymphocytes (TILs) has been shown to have a significant impact on the prognosis of these patients. Despite some biological characteristics of the tumor that may differ depending on the gestational age, little is known about the dynamics of the immune landscape within the tumor microenvironment (TME) in PrBC. Therefore, in this study, our objective was to gain comprehensive insights into the relationship between gestational age at breast cancer diagnosis and the composition of the TME. Methods: n = 108 PrBC were selected from our institutional registry and categorized based on the gestational age by trimester. For all cases, TILs were profiled according to the International TILs Working Group recommendations, and subtyped by CD4, CD8, and forkhead box P3 (FOXP3) immunohistochemistry. PD-L1 was tested according to the combined positive score (CPS) using the IHC 22C3 pharmDx assay, with a cutoff value of ≥10 for positivity. The statistical approach encompassed Fisher’s and Chi-squared tests, with appropriate adjustments for multiple comparisons, logistic regression models, and survival analyses based on the Kaplan–Meier method. Results: The proportion of patients with poorly differentiated (G3) neoplasms increased as the gestational age advanced (first trimester, n = 25, 56.8%; second trimester, n = 27, 69.2%; third trimester, n = 21, 87.5%; p = 0.03). The histologic subtypes as well as the hormone receptor (HR) and HER2 status did not show significant changes across different pregnancy trimesters. In the HR+/HER2– subtype, there was a higher proportion of tumors with high/moderate TILs in the early phases of pregnancy, similar to FOXP3 expression (TILs: first trimester, n = 10, 35.7%; second trimester, n = 2, 10.5%; third trimester, n = 0; p = 0.02; FOXP3: first trimester, n = 10, 40%; second trimester, n = 3, 15.8%; third trimester, n = 0; p = 0.03). The median follow-up for our cohort was 81 months. Patients who relapsed after a breast cancer diagnosis during the first trimester were more frequently PD-L1-negative, unlike those with no disease recurrence (n = 9, 100% vs. n = 9, 56.3%; p = 0.03; hormone therapy and n = 9, 100% vs. n = 7, 53.9%; p = 0.02; chemotherapy). No statistically significant differences were seen among the three trimesters in terms of survival outcome. Conclusion: The TME dynamics of HR+/HER2− PrBC vary based on gestational age, suggesting that immune tolerance expression during later gestational age could explain the increased aggressiveness of tumors diagnosed at that stage

Gap Opening in Double-Sided Highly Hydrogenated Free-Standing Graphene

Conversion of free-standing graphene into pure graphane-where each C atom is sp3bound to a hydrogen atom-has not been achieved so far, in spite of numerous experimental attempts. Here, we obtain an unprecedented level of hydrogenation (≈90% of sp3bonds) by exposing fully free-standing nanoporous samples-constituted by a single to a few veils of smoothly rippled graphene-to atomic hydrogen in ultrahigh vacuum. Such a controlled hydrogenation of high-quality and high-specific-area samples converts the original conductive graphene into a wide gap semiconductor, with the valence band maximum (VBM) ∼3.5 eV below the Fermi level, as monitored by photoemission spectromicroscopy and confirmed by theoretical predictions. In fact, the calculated band structure unequivocally identifies the achievement of a stable, double-sided fully hydrogenated configuration, with gap opening and no trace of πstates, in excellent agreement with the experimental results

Retained PTEN Expression Preferentially Identifies Mismatch Repair-Proficient Breast Cancers

Introduction/ Background Loss of phosphatase and tensin homolog (PTEN) expression and alterations in mismatch repair (MMR) genes are regarded as early oncogenic events in breast cancer. It has recently been hypothesized that the polyadenosine tract in PTEN might be a target for mutation in MMR-deficient endometrial tumors. However, the frequency and significance of MMR alterations in breast cancer is debated, and their relationship with PTEN status has not been investigated in the breast. Aims In this study, we sought to explore the relationships between PTEN expression and MMR alterations and to define whether PTEN immunohistochemistry is a predictor of MMR status in breast cancer. Methods 309 cases, including 261 invasive ductal carcinomas, no special type, 32 invasive lobular carcinomas, and 16 invasive ductal carcinomas, mixed types, carefully characterized from clinical and pathological standpoints, were reviewed and used to construct 11 tissue microarrays (TMAs). For each case, a mean of 4.5 tumor tissue cores (range 3 to 6 cores) was sampled, incorporating distinct topographic areas of the tumor, as well as matched non-neoplastic breast tissue, and, when present, associated in situ carcinoma. Taken together, 1381 spots were generated. Each TMA was subjected to immunohistochemical analysis of PTEN and the DNA MMR proteins MLH1, MSH2, MSH6 and PMS2. In order to allow a quick navigation within each TMA, and to minimize human-related biases, each stained slide was digitalized and blindly analyzed by two pathologists using a dedicated software able to segment TMA cores. The pattern of expression was therefore annotated manually on a digital database using a specific add-on module. Results According to clinicopathologic surrogate definition of intrinsic subtypes, PTEN protein loss was more frequent in luminal A-like and triple negative groups compared to luminal B-like carcinomas, as recently observed in other studies. MMR status in Luminal B-like tumors did not differ significantly between PTEN-retained and PTEN-loss groups, regardless HER2 amplification. In particular, retained PTEN expression was a predictor of MMR proficiency in approximately 35% of cases for this group. However, in luminal A-like and triple negative breast cancer groups, retained positive expression of MMR proteins was observed in 100% of cases showing PTEN wild-type immunohistochemical expression. Discussion: The present study is the first to investigate PTEN protein loss in a large set of breast carcinomas based on DNA MMR status by immunohistochemistry. Our findings broaden the understanding of the biology underpinning breast cancer, suggesting that MMR alterations are likely to be independent of PTEN status in the majority of luminal B-like breast cancers and that, in a way akin to endometrial carcinoma, MMR deficiency could play a part in the development of PTEN alterations in luminal A-like and triple negative breast cancers. The integration of traditional pathology with cutting-edge digital tools allowed a rapid quantification of immunohistochemistry and effective data organization in this wide cohort multi-variable study. Conclusion: PTEN immunohistochemistry is a useful adjunct in the clinical evaluation of breast cancer patients, being able to capture all MMR-proficient luminal A-like and triple negative tumors