Densest Subgraph in Dynamic Graph Streams

In this paper, we consider the problem of approximating the densest subgraph in the dynamic graph stream model. In this model of computation, the input graph is defined by an arbitrary sequence of edge insertions and deletions and the goal is to analyze properties of the resulting graph given memory that is sub-linear in the size of the stream. We present a single-pass algorithm that returns a $(1+\epsilon)$ approximation of the maximum density with high probability; the algorithm uses O(\epsilon^{-2} n \polylog n) space, processes each stream update in \polylog (n) time, and uses \poly(n) post-processing time where $n$ is the number of nodes. The space used by our algorithm matches the lower bound of Bahmani et al.~(PVLDB 2012) up to a poly-logarithmic factor for constant $\epsilon$. The best existing results for this problem were established recently by Bhattacharya et al.~(STOC 2015). They presented a $(2+\epsilon)$ approximation algorithm using similar space and another algorithm that both processed each update and maintained a $(4+\epsilon)$ approximation of the current maximum density in \polylog (n) time per-update.Comment: To appear in MFCS 201

Histological study of different layers of oocyte in stellate sturgeon (Acipenser stellatus)

The present study was conducted on a large number of oocytes collected from 36 female Acipenser stellatus brood fish caught from fishing grounds in the Guilan province and transferred to the Shahid Behesti Sturgeon Breeding Center during 1997-1998. Physiological assessments were carried out on the microscopic sections prepared from these oocytes. Under normal conditions, 9 distinguishable layers were observed in the sections prepared from A. stellatus oocytes that included the follicle, the outer most layer, followed by a jelly coat, an external zona radiata, internal zona radiata, fat layer, pigments, cytoplasm, nucleus and nucleoli. The presence of erythrocytes and micropyle canal in the oocytes indicate normal embryognesis among them

A tight lower bound instance for k-means++ in constant dimension

The k-means++ seeding algorithm is one of the most popular algorithms that is used for finding the initial $k$ centers when using the k-means heuristic. The algorithm is a simple sampling procedure and can be described as follows: Pick the first center randomly from the given points. For $i > 1$, pick a point to be the $i^{th}$ center with probability proportional to the square of the Euclidean distance of this point to the closest previously $(i-1)$ chosen centers. The k-means++ seeding algorithm is not only simple and fast but also gives an $O(\log{k})$ approximation in expectation as shown by Arthur and Vassilvitskii. There are datasets on which this seeding algorithm gives an approximation factor of $\Omega(\log{k})$ in expectation. However, it is not clear from these results if the algorithm achieves good approximation factor with reasonably high probability (say $1/poly(k)$). Brunsch and R\"{o}glin gave a dataset where the k-means++ seeding algorithm achieves an $O(\log{k})$ approximation ratio with probability that is exponentially small in $k$. However, this and all other known lower-bound examples are high dimensional. So, an open problem was to understand the behavior of the algorithm on low dimensional datasets. In this work, we give a simple two dimensional dataset on which the seeding algorithm achieves an $O(\log{k})$ approximation ratio with probability exponentially small in $k$. This solves open problems posed by Mahajan et al. and by Brunsch and R\"{o}glin.Comment: To appear in TAMC 2014. arXiv admin note: text overlap with arXiv:1306.420

Short communication: Seasonal changes of blood serum ions in Beluga (Huso huso) cultured in brackish water

Living sturgeons (Acipenseridae) are representatives of the ancient group Chondrostei, which had a common origin with Palaeonisci, known from the Devonian period. In spite of their freshwater origin, in their history, they occupied different salinities and at present, they can live in both fresh and seawater mediums. Study of osmotic and ionic regulation in acipenserids, that connect to marine conditions in different extents (freshwater, diadromous brackish water, diadromous seawater), make it possible to establish the dependence of functional level of osmotic and ionic homeostatic mechanisms from medium salinity in some acipenserids. It was ascertained that in higher salinities, the functional level of these mechanisms increases. So investigation of osmo-ion regulation is one of the most important problems in the culture of sturgeon in new mediums

Phytotherapy for Bacillus cereus: A review of the most important medicinal plants of Iran effective on B. cereus

Infectious diseases are spreading day-to-day with excessive health care costs. Bacillus cereus is a known causative agent of foodborne diseases. Because of emergence of antibiotic resistance, it is necessary to develop nature- and plant-based antibiotics. Many of the medicinal plants are highly able to fight bacterial and fungal pathogens in humans. Scientists are interested in using these plants to treat infections because these plants cause much fewer side effects than chemical drugs. This review article reported the native medicinal plants effective on B. cereus. The findings indicate that Eucalyptus camaldulensis Dehnh, Zataria multiflora, Mentha pulegium, Artemisia persica, Cuminum cyminum, Cordia myxa L, Scrophularia striata, Mentha longifolia, Rosmarinus officinalis, and Lavandula sp. are effective on B. cereus. Because these plants have antimicrobial effects according to traditional medicine, their anti-B. cereus effects have been confirmed in scientific investigations, and their compounds have already been identified in phytochemical investigations, their effective compounds can be used to produce naturebased, anti-B. cereus antibiotics

Parametric t-Distributed Stochastic Exemplar-centered Embedding

Parametric embedding methods such as parametric t-SNE (pt-SNE) have been widely adopted for data visualization and out-of-sample data embedding without further computationally expensive optimization or approximation. However, the performance of pt-SNE is highly sensitive to the hyper-parameter batch size due to conflicting optimization goals, and often produces dramatically different embeddings with different choices of user-defined perplexities. To effectively solve these issues, we present parametric t-distributed stochastic exemplar-centered embedding methods. Our strategy learns embedding parameters by comparing given data only with precomputed exemplars, resulting in a cost function with linear computational and memory complexity, which is further reduced by noise contrastive samples. Moreover, we propose a shallow embedding network with high-order feature interactions for data visualization, which is much easier to tune but produces comparable performance in contrast to a deep neural network employed by pt-SNE. We empirically demonstrate, using several benchmark datasets, that our proposed methods significantly outperform pt-SNE in terms of robustness, visual effects, and quantitative evaluations.Comment: fixed typo

In vitro pollen germination, pollen tube growth and longevity in some genotypes of loquat (Eriobotria japonica Lindl.)

Loquat (Eriobotrya japonica Lindl.) is one of the most perspective trees with tasty fruits suitable for commercial production in Iran. However, self-incompatibility of most loquat cultivars makes it necessary to select good pollinizers in breeding and orchard establishment programs. Therefore, studies on pollen viability traits of cultivars and genotypes have been one of the main issues for loquat growers and breeders which are investigated in this study. The experiment was conducted in in vitro conditions for the identification of the pollen germination and longevity in some loquat genotypes for recognition of the best pollinizers. Pollens of twenty (20) genotypes were gathered and after three weeks storage in 0°C, their pollen germination, pollen tube growth rate and pollen longevity were tested in the in vitro medium. The experiment was carried out based on completely randomized design (CRD) and data were analyzed with SAS software. Significant differences were observed among the genotypes in pollen germination, pollen tube growth rate and pollen longevity. Finally, the best genotypes were selected for using in loquat orchard establishment and breeding programs in Iran.Key words: Loquat, in vitro, pollen germination, pollen tube growth, pollen longevity, breeding programs

Effects of dietary isoflavone-genistein on hematological and immunological parameters in pre-brood stock beluga, Huso huso

This study was carried out with the aim of detecting the dietary effects of isoflavone-genistein on hematological and immunological parameters in beluga, Huso huso in a 12-week feeding period. Five isonitrogenous (45% crude protein) and isoenergetic (19.5 MJ kg^-1) diets were formulated to contain four graded levels of isoflavone-genistein, namely 0, 0.2, 0.4, 0.8 and 1.6 g kg^-1 diet. Fish (initial average weight: 26.1 ± 1.8 kg) were stocked in ponds in groups of 3 and fed the experimental diets in triplicate. At the end of experiment, physiological indicators, including hematological and immunological parameters, such as red blood cell (RBC), white blood cell count (WBC), hematocrit (Ht), hemoglobin (Hb), lymphocyte, neutrophil, eosinophil, monocyte, haematological indices, lysozyme, total immunoglobulin (IgM) and complementary activities were determined. Results suggested that mean corpuscular hemoglobin concentration (MCHC) and values of neutrophil had significant differences between treatments. The activities of serum lysozyme, IgM, C3 and C4 were significantly influenced by the dietary genistein concentrations. Results indicated that genistein had significant effects on some hematological and immunological parameters in beluga

Blood serum osmotic and ionic regulation of wild adults and reared juvenile Persian sturgeon, Acipenser persicus

The osmoregulatory system was studied in wild adult and reared juvenile Persian sturgeon, Acipenser persicus. The mean osmolarity in blood serum of specimens from the Caspian Sea, estuary, the Kouraneski pools and the rearing tanks were 305.3±14.3, 308.7±25.8, 265.0±19.1 and 259.3±8.8 mosmol/L, respectively; the mean concentrations of Na+ were 151.2±6.3, 152.2±8.4, 142.5±5.9 and 131.4±4.1 meq/L whereas mean concentrations of K+ were 2.7±0.9, 3.6±0.9, 3.1±0.5 and 2.6±0.5meq/L, respectively. The concentrations for Mg++ ion in fish of the same four origins were 1.5±0.2; 1.5±0.3, 0.8±0.2 and 0.7±0.2 meq/L, and those of Ca++ were 2.31±0.51, 2.61±0.51, 1.85±0.58 and 1.46±0.43, respectively. The Pearson's correlation coefficient and regression equation indicated that Mg++(r =0.38) and Na+ (r=0.41) were effective ions for determination of blood serum osmotic pressure in A. persicus in brackish water and freshwater. This study also showed that blood serum osmotic pressure was independent of sex

Determination of sex and sexual maturation stages in cultured Acipenser nudiventris using biopsy method

Sturgeon fish take long time to mature sexually and determination of sex and sexual maturity stages is important in artificial rearing of the fish. Sex determination by macroscopic method has thus far been impossible for the fish at juvenile stages. Gonad biopsy and its histological examination is one way for detecting male and female sturgeon fishes. To do so, we collected gonad samples from 13 five year old and 17 six year old specimens of the cultured Acipenser nudiventris. Samples were studied by light microscope after fixing and histological practices. Of the 13 five years old specimens, only 3 (23.1%) were male and 10 (76.9 %) were females. From 17 six years old fish, 10 (58.8%) were males and 7 (41.2%) were females. Histological studies showed that all male fish were at stage IV, but 5.8 % of all females were at stage I, 41.2 % were at stage II and 53 % were at stage II-III of sexual maturation. We also showed that in the studies sample, males reached maturity sooner than females