1,971 research outputs found
STATS - A Point Access Method for Multidimensional Clusters.
The ubiquity of high-dimensional data in machine learning and data mining applications makes its efficient indexing and retrieval from main memory crucial. Frequently, these machine learning algorithms need to query specific characteristics of single multidimensional points. For example, given a clustered dataset, the cluster membership (CM) query retrieves the cluster to which an object belongs. To efficiently answer this type of query we have developed STATS, a novel main-memory index which scales to answer CM queries on increasingly big datasets. Current indexing methods are oblivious to the structure of clusters in the data, and we thus, develop STATS around the key insight that exploiting the cluster information when indexing and preserving it in the index will accelerate look up. We show experimentally that STATS outperforms known methods in regards to retrieval time and scales well with dataset size for any number of dimensions
Detecting brute-force attacks on cryptocurrency wallets
Blockchain is a distributed ledger, which is protected against malicious
modifications by means of cryptographic tools, e.g. digital signatures and hash
functions. One of the most prominent applications of blockchains is
cryptocurrencies, such as Bitcoin. In this work, we consider a particular
attack on wallets for collecting assets in a cryptocurrency network based on
brute-force search attacks. Using Bitcoin as an example, we demonstrate that if
the attack is implemented successfully, a legitimate user is able to prove that
fact of this attack with a high probability. We also consider two options for
modification of existing cryptocurrency protocols for dealing with this type of
attacks. First, we discuss a modification that requires introducing changes in
the Bitcoin protocol and allows diminishing the motivation to attack wallets.
Second, an alternative option is the construction of special smart-contracts,
which reward the users for providing evidence of the brute-force attack. The
execution of this smart-contract can work as an automatic alarm that the
employed cryptographic mechanisms, and (particularly) hash functions, have an
evident vulnerability.Comment: 10 pages, 2 figures; published versio
A New Approach to Measuring Distances in Dense Graphs
The problem of computing distances and shortest paths between vertices in graphs is one of the fundamental issues in graph theory. It is of great importance in many different applications, for example, transportation, and social network analysis. However, efficient shortest distance algorithms are still desired in many disciplines. Basically, the majority of dense graphs have ties between the shortest distances. Therefore, we consider a different approach and introduce a new measure to solve all-pairs shortest paths for undirected and unweighted graphs. This measures the shortest distance between any two vertices by considering the length and the number of all possible paths between them. The main aim of this new approach is to break the ties between equal shortest paths SP, which can be obtained by the Breadth-first search algorithm (BFS), and distinguish meaningfully between these equal distances. Moreover, using the new measure in clustering produces higher quality results compared with SP. In our study, we apply two different clustering techniques: hierarchical clustering and K-means clustering, with four different graph models, and for a various number of clusters. We compare the results using a modularity function to check the quality of our clustering results
Genetic diversity and population structure of Fusarium fujikuroi causing Bakanae, an emerging disease of rice in India
45-52Bakanae caused by Fusarium fujikuroi (Nirenberg), is emerging as a serious threat for rice (Oryza sativa. L.) cultivation in India. In this study, 63 isolates of Fusarium fujikuroi isolated from symptomatic diseased plants were characterized for their morphology, pathogenicity and molecular variability using universal rice primers (URP). Of the 12 URPs used in the study, 6 primers could produce polymorphic fragments in all the isolates. The URP 17R primer was highly polymorphic (100%), whereas, the URP 1F primer produced 75% polymorphic fragments. A dendrogram obtained from the combined analysis of 6 URP primers categorized the isolates into four clusters, where most of the isolates from Punjab and Haryana were clustered separately. Mating type of the population was identified based on MAT-1 and MAT-2 region universal primers for Gibberella fujikuroi. Among the 63 isolates, 18 (28.57%) were identified as MAT-1 and 45 (71.42%) as MAT-2. The effective population number for mating type was 89% of the total population. Since the distribution frequencies of both mating types were not equal in the Indian population of F. fujikuroi, it could conclude that majority of the multiplication of isolates under field conditions was through asexual reproduction. However, the presence of both mating types in F. fujikuroi indicates that the population is also capable of sexual reproduction. Therefore, it is important to develop cultivars with inbuilt resistance to bakanae disease, taking into consideration the factors such as environmental conditions and variability of the pathogen in the area of intended cultivation
Virtual Reality Simulator for Medical Auscultation Training
© Springer Nature Switzerland AG 2019. According to the Oxford English dictionary, auscultation is âthe action of listening to sounds from the heart, lungs, or other organs, typically with a stethoscope, as a part of medical diagnosis.â In this work, we describe a medical simulator that includes audio, visual, pseudo-haptic, and spatial elements for training medical students in auscultation. In our training simulator, the user is fully immersed in a virtual reality (VR) environment. A typical hospital bedside scenario was recreated, and the users can see their own body and the patient increase immersion. External tracking devices are used to acquire the userâs movements and map them into the VR environment. The main idea behind this work is for the user to associate the heart and lung sounds, as heard through the stethoscope with the corresponding health-related problems. Several sound parameters including the volume, give information about the type and severity of the disease. Our simulator can reproduce sounds belonging to the heart and lungs. Through the proposed VR-based training, the medical student ideally will learn to relate sounds to illnesses in a realistic setting, accelerating the learning process
Using an Indoor Localization System for Activity Recognition
Recognizing the activity performed by users is importantin many application domains, from e-health to home automation. Thispaper explores the use of a fine-grained indoor localization system, basedon ultra-wideband, for activity recognition. The user is supposed to weara number of active tags. The position of active tags is first determinedwith respect to the space where the user is moving, then some position-independent metrics are estimated and given as input to a previouslytrained system. Experimental results show that accuracy values as highasâŒ95% can be obtained when using a personalized model
Durability of Mortar Incorporating Ferronickel Slag Aggregate and Supplementary Cementitious Materials Subjected to WetâDry Cycles
This paper presents the strength and durability of cement mortars using 0â100% ferronickel slag (FNS) as replacement of natural sand and 30% fly ash or ground granulated blast furnace slag (GGBFS) as cement replacement. The maximum mortar compressive strength was achieved with 50% sand replacement by FNS. Durability was evaluated by the changes in compressive strength and mass of mortar specimens after 28 cycles of alternate wetting at 23 °C and drying at 110 °C. Strength loss increased by the increase of FNS content with marginal increases in the mass loss. Though a maximum strength loss of up to 26% was observed, the values were only 3â9% for 25â100% FNS contents in the mixtures containing 30% fly ash. The XRD data showed that the pozzolanic reaction of fly ash helped to reduce the strength loss caused by wetâdry cycles. Overall, the volume of permeable voids (VPV) and performance in wetâdry cycles for 50% FNS and 30% fly ash were better than those for 100% OPC and natural sand
Integer Reconstruction Public-Key Encryption
In [AJPS17], Aggarwal, Joux, Prakash & Santha described
an elegant public-key cryptosystem (AJPS-1) mimicking NTRU over the
integers. This algorithm relies on the properties of Mersenne primes
instead of polynomial rings.
A later ePrint [BCGN17] by Beunardeau et al. revised AJPS-1âs initial
security estimates. While lower than initially thought, the best known
attack on AJPS-1 still seems to leave the defender with an exponential
advantage over the attacker [dBDJdW17]. However, this lower exponential
advantage implies enlarging AJPS-1âs parameters. This, plus the fact that
AJPS-1 encodes only a single plaintext bit per ciphertext, made AJPS-1
impractical. In a recent update, Aggarwal et al. overcame this limitation
by extending AJPS-1âs bandwidth. This variant (AJPS-ECC) modifies the
definition of the public-key and relies on error-correcting codes.
This paper presents a different high-bandwidth construction. By opposition
to AJPS-ECC, we do not modify the public-key, avoid using errorcorrecting
codes and use backtracking to decrypt. The new algorithm
is orthogonal to AJPS-ECC as both mechanisms may be concurrently
used in the same ciphertext and cumulate their bandwidth improvement
effects. Alternatively, we can increase AJPS-ECCâs information rate by a
factor of 26 for the parameters recommended in [AJPS17].
The obtained bandwidth improvement and the fact that encryption and
decryption are reasonably efficient, make our scheme an interesting postquantum
candidate
Heterologous production of curcuminoids
Curcuminoids, components of the rhizome of turmeric, show several beneficial biological activities, including anticarcinogenic, antioxidant, anti-inflammatory, and antitumor activities. Despite their numerous pharmaceutically important properties, the low natural abundance of curcuminoids represents a major drawback for their use as therapeutic agents. Therefore, they represent attractive targets for heterologous production and metabolic engineering. The understanding of biosynthesis of curcuminoids in turmeric made remarkable advances in the last decade, and as a result, several efforts to produce them in heterologous organisms have been reported. The artificial biosynthetic pathway (e.g., in Escherichia coli) can start with the supplementation of the amino acid tyrosine or phenylalanine or of carboxylic acids and lead to the production of several natural curcuminoids. Unnatural carboxylic acids can also be supplemented as precursors and lead to the production of unnatural compounds with possibly novel therapeutic properties. In this paper, we review the natural conversion of curcuminoids in turmeric and their production by E. coli using an artificial biosynthetic pathway. We also explore the potential of other enzymes discovered recently or already used in other similar biosynthetic pathways, such as flavonoids and stilbenoids, to increase curcuminoid yield and activity.We acknowledge financial support from the Strategic Project PEst-OE/EQB/LA0023/2013, project reference RECI/BBB-EBI/0179/2012 (project number FCOMP-01-0124-FEDER-027462), project SYNBIOBACTHER (PTDC/EBB-BIO/102863/2008), and a doctoral grant (SFRH/BD/51187/ 2010) to J. L. Rodrigues, funded by Fundacao para a Ciencia e a Tecnologia. We thank the MIT-Portugal Program for support given to J. L. Rodrigues
Protective CD8+ T lymphocytes in Primates Immunized with Malaria Sporozoites
Live attenuated malaria vaccines are more potent than the recombinant protein, bacterial or viral platform vaccines that have been tested, and an attenuated sporozoite vaccine against falciparum malaria is being developed for humans. In mice, attenuated malaria sporozoite vaccines induce CD8+ T cells that kill parasites developing in the liver. We were curious to know if CD8+ T cells were also important in protecting primates against malaria. We immunized 9 rhesus monkeys with radiation attenuated Plasmodium knowlesi sporozoites, and found that 5 did not develop blood stage infections after challenge with live sporozoites. We then injected 4 of these protected monkeys with cM-T807, a monoclonal antibody to the CD8 molecule which depletes T cells. The fifth monkey received equivalent doses of normal IgG. In 3 of the 4 monkeys receiving cM-T807 circulating CD8+ T cells were profoundly depleted. When re-challenged with live sporozoites all 3 of these depleted animals developed blood stage malaria. The fourth monkey receiving cM-T807 retained many circulating CD8+ T cells. This monkey, and the vaccinated monkey receiving normal IgG, did not develop blood stage malaria at re-challenge with live sporozoites. Animals were treated with antimalarial drugs and rested for 4 months. During this interval CD8+ T cells re-appeared in the circulation of the depleted monkeys. When all vaccinated animals received a third challenge with live sporozoites, all 5 monkeys were once again protected and did not develop blood stage malaria infections. These data indicate that CD8+ T cells are important effector cells protecting monkeys against malaria sporozoite infection. We believe that malaria vaccines which induce effector CD8+ T cells in humans will have the best chance of protecting against malaria
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