Exact Distance Oracles for Planar Graphs with Failing Vertices

We consider exact distance oracles for directed weighted planar graphs in the presence of failing vertices. Given a source vertex $u$, a target vertex $v$ and a set $X$ of $k$ failed vertices, such an oracle returns the length of a shortest $u$-to-$v$ path that avoids all vertices in $X$. We propose oracles that can handle any number $k$ of failures. More specifically, for a directed weighted planar graph with $n$ vertices, any constant $k$, and for any $q \in [1,\sqrt n]$, we propose an oracle of size $\tilde{\mathcal{O}}(\frac{n^{k+3/2}}{q^{2k+1}})$ that answers queries in $\tilde{\mathcal{O}}(q)$ time. In particular, we show an $\tilde{\mathcal{O}}(n)$-size, $\tilde{\mathcal{O}}(\sqrt{n})$-query-time oracle for any constant $k$. This matches, up to polylogarithmic factors, the fastest failure-free distance oracles with nearly linear space. For single vertex failures ($k=1$), our $\tilde{\mathcal{O}}(\frac{n^{5/2}}{q^3})$-size, $\tilde{\mathcal{O}}(q)$-query-time oracle improves over the previously best known tradeoff of Baswana et al. [SODA 2012] by polynomial factors for $q = \Omega(n^t)$, $t \in (1/4,1/2]$. For multiple failures, no planarity exploiting results were previously known

Encapsulation of Bifidobacterium longum in alginate-dairy matrices and survival in simulated gastrointestinal conditions, refrigeration, cow milk and goat milk

The aim of this study was to microencapsulate Bifidobacterium longum subsp. infantis CCUG 52486 using the extrusion method in a variety of matrices, namely sodium alginate (SA), sodium alginate-cow milk (SACM), sodium alginate-goat milk (SAGM) and sodium alginate-casein hydrolysate (SACH), and to evaluate the survival of free and encapsulated bacterial cells under different conditions. The encapsulation yield, size and surface morphology of the microcapsules were evaluated. The survival of microencapsulated bacterial cells and free bacterial cells were evaluated under simulated gastrointestinal conditions as well as in refrigeration, cow milk and goat milk during storage at 4 oC for 28 days. The average size of SACM capsules and SAGM capsules was 2.8±0.3 mm and 3.1±0.2 mm respectively. Goat milk and cow milk based matrices resulted in dense microcapsules which led to better performances in simulated gastrointestinal conditions than SA and SACH microcapsules. The bacterial cells encapsulated in SAGM showed the highest survival rate in cow milk (7.61 log cfu g-1) and goat milk (8.10 log cfu g-1) after the storage of 28 d. The cells encapsulated in SA and SACH and the free cells performed poorly under the simulated gastrointestinal conditions and in all different storage conditions. This study showed that SACM and SAGM are suitable to encapsulate B. longum subsp. infantis CCUG 52486 using the extrusion technique and more specifically, SAGM has a potential to be used as a new encapsulation material for encapsulating probiotic bacteria, resulting milk and goat milk-based products with higher probiotic cell concentrations during refrigerated storage

Repetition Detection in a Dynamic String

A string UU for a non-empty string U is called a square. Squares have been well-studied both from a combinatorial and an algorithmic perspective. In this paper, we are the first to consider the problem of maintaining a representation of the squares in a dynamic string S of length at most n. We present an algorithm that updates this representation in n^o(1) time. This representation allows us to report a longest square-substring of S in O(1) time and all square-substrings of S in O(output) time. We achieve this by introducing a novel tool - maintaining prefix-suffix matches of two dynamic strings. We extend the above result to address the problem of maintaining a representation of all runs (maximal repetitions) of the string. Runs are known to capture the periodic structure of a string, and, as an application, we show that our representation of runs allows us to efficiently answer periodicity queries for substrings of a dynamic string. These queries have proven useful in static pattern matching problems and our techniques have the potential of offering solutions to these problems in a dynamic text setting

Optimised production and extraction of astaxanthin from the yeast Xanthophyllomyces dendrorhous

Currently, astaxanthin demand is fulfilled by chemical synthesis using petroleum-based feedstocks. As such, alternative pathways of natural astaxanthin production attracts much research interest. This study aimed at optimising bioreactor operation parameters for astaxanthin production and evaluated strategies for its subsequent extraction. The effect of pH and agitation were evident as significant reduction in both biomass and astaxanthin production was observed when the culture pH was not controlled, and low agitation speed was applied. At controlled pH condition and high agitation speed, significant increase in biomass (16.4 g/l) and astaxanthin production (3.6 mg/l) were obtained. Enzymatic yeast cell lysis using two commercial enzymes (Accellerase 1500 and Glucanex) was optimised using central composite design of experiment (DoE). Accellerase 1500 led to mild cell disruption and only 9% (w/w) of astaxanthin extraction. However, glucanex treatment resulted in complete astaxanthin extractability, compared to standard extraction method (DMSO/acetone). When supercritical CO2 was employed as an extraction solvent in accellerace pre-treated Xanthophyllomyces dendrorhous cells, astaxanthin extraction increased 2.5-fold. Overall, the study showed that extraction conditions can be tailored towards targeted pigments present in complex mixtures, such as in microbial cells

Mapping the urban green area influence local climate under windless and light wind conditions : the case of western part of Athens, Greece

Investigations concentrated on the influence of the urban green areas on the local climate. Nocturnal mobile measurements were carried out under windless and light wind conditions, over the thermally polluted western part of Athens, Greece. For this purpose three green areas with different size and characteristics were selected. The collected data were analysed using geographical information system software. The spatial patterns of air temperature and the calculation of Discomfort Index indicated a beneficial influence of green areas and non built-up areas

Climate Change: a Multiplier for Terrorist Activity

Over the past ten years, both understanding and awareness of the links between climate change and security have increased. However, those links are not simple and clear. The growing impacts of climate change do not automatically lead to more violence and conflict. Rather, climate change acts as a threat multiplier. The study addresses the question of how the impacts of climate change are a contributing factor in the rise and growth of terrorism and political violence in African regions. To explain the complexity of the problem, a system dynamics model structure is presented in the form of casual loop diagrams. The dynamic behavior in livelihood arises from negative impacts of climate change on livelihoods in many countries and regions through, e.g. water and land scarcity, food insecurity and migration. The affected population groups are becoming more vulnerable not only to negative climate developments but also to recruitments by violent groups such as Al-Qaeda, Islamic State, Al-Shabaab or other militia. These terrorist groups can offer alternative livelihoods, economic motivations, and responses to possible political and economic dissatisfactions. This does not imply that there is a direct link between climate change and terrorists-related violence and conflict. However, environmental impacts and climatic change contributes to creating conditions in which these groups can thrive and facilitate the pursuit of their strategies. Further, violent groups are using natural resources as a weapon of war. In fragile environments, these groups can use water resources as a weapon or reduce access to natural resources. This development creates a dynamic for these groups, considering the fact that the scarcer resources become, the more power is given to those who controls them. Climate change will increasingly challenge the states’ abilities to provide services and stability. In particular, extreme climate events can threaten the relationship between governments and populations. In such a case, a poor and slow government response could contribute to further instability, fragility, violence and strengthening of violent groups