The Complexity of Computing Minimal Unidirectional Covering Sets

Given a binary dominance relation on a set of alternatives, a common thread in the social sciences is to identify subsets of alternatives that satisfy certain notions of stability. Examples can be found in areas as diverse as voting theory, game theory, and argumentation theory. Brandt and Fischer [BF08] proved that it is NP-hard to decide whether an alternative is contained in some inclusion-minimal upward or downward covering set. For both problems, we raise this lower bound to the Theta_{2}^{p} level of the polynomial hierarchy and provide a Sigma_{2}^{p} upper bound. Relatedly, we show that a variety of other natural problems regarding minimal or minimum-size covering sets are hard or complete for either of NP, coNP, and Theta_{2}^{p}. An important consequence of our results is that neither minimal upward nor minimal downward covering sets (even when guaranteed to exist) can be computed in polynomial time unless P=NP. This sharply contrasts with Brandt and Fischer's result that minimal bidirectional covering sets (i.e., sets that are both minimal upward and minimal downward covering sets) are polynomial-time computable.Comment: 27 pages, 7 figure

Stereological Analysis of Neuron, Glial and Endothelial Cell Numbers in the Human Amygdaloid Complex

Cell number alterations in the amygdaloid complex (AC) might coincide with neurological and psychiatric pathologies with anxiety imbalances as well as with changes in brain functionality during aging. This stereological study focused on estimating, in samples from 7 control individuals aged 20 to 75 years old, the number and density of neurons, glia and endothelial cells in the entire AC and in its 5 nuclear groups (including the basolateral (BL), corticomedial and central groups), 5 nuclei and 13 nuclear subdivisions. The volume and total cell number in these territories were determined on Nissl-stained sections with the Cavalieri principle and the optical fractionator. The AC mean volume was 956 mm3 and mean cell numbers (x106) were: 15.3 neurons, 60 glial cells and 16.8 endothelial cells. The numbers of endothelial cells and neurons were similar in each AC region and were one fourth the number of glial cells. Analysis of the influence of the individuals’ age at death on volume, cell number and density in each of these 24 AC regions suggested that aging does not affect regional size or the amount of glial cells, but that neuron and endothelial cell numbers respectively tended to decrease and increase in territories such as AC or BL. These accurate stereological measures of volume and total cell numbers and densities in the AC of control individuals could serve as appropriate reference values to evaluate subtle alterations in this structure in pathological conditions

Malaria and Fetal Growth Alterations in the 3(rd) Trimester of Pregnancy: A Longitudinal Ultrasound Study.

Pregnancy associated malaria is associated with decreased birth weight, but in-utero evaluation of fetal growth alterations is rarely performed. The objective of this study was to investigate malaria induced changes in fetal growth during the 3(rd) trimester using trans-abdominal ultrasound. An observational study of 876 pregnant women (398 primi- and secundigravidae and 478 multigravidae) was conducted in Tanzania. Fetal growth was monitored with ultrasound and screening for malaria was performed regularly. Birth weight and fetal weight were converted to z-scores, and fetal growth evaluated as fetal weight gain from the 26th week of pregnancy. Malaria infection only affected birth weight and fetal growth among primi- and secundigravid women. Forty-eight of the 398 primi- and secundigravid women had malaria during pregnancy causing a reduction in the newborns z-score of -0.50 (95% CI: -0.86, -0.13, P = 0.008, multiple linear regression). Fifty-eight percent (28/48) of the primi- and secundigravidae had malaria in the first half of pregnancy, but an effect on fetal growth was observed in the 3(rd) trimester with an OR of 4.89 for the fetal growth rate belonging to the lowest 25% in the population (95%CI: 2.03-11.79, P<0.001, multiple logistic regression). At an individual level, among the primi- and secundigravidae, 27% experienced alterations of fetal growth immediately after exposure but only for a short interval, 27% only late in pregnancy, 16.2% persistently from exposure until the end of pregnancy, and 29.7% had no alterations of fetal growth. The effect of malaria infections was observed during the 3(rd) trimester, despite infections occurring much earlier in pregnancy, and different mechanisms might operate leading to different patterns of growth alterations. This study highlights the need for protection against malaria throughout pregnancy and the recognition that observed changes in fetal growth might be a consequence of an infection much earlier in pregnancy.\u

Is Overweight in Stunted Preschool Children in Cameroon Related to Reductions in Fat Oxidation, Resting Energy Expenditure and Physical Activity?

Recent studies suggest that early modifications in metabolic pathways and behaviour, leading to energy conservation and reduced linear growth, could represent adaptations to nutritional constraints during foetal life and infancy. Impaired fat oxidation, low resting energy expenditure and reduced physical activity, resulting from these adaptations, could facilitate fat storage and development of overweight in growth-retarded children that consume more energy-dense food. This study aims at assessing whether: (1) dual-burden preschool children (simultaneously stunted and overweight) of Yaounde (Cameroon) have low birth-weight (indicator of foetal undernutrition) and reductions in fat oxidation, resting energy expenditure (REE) and physical activity, (2) fat oxidation, REE and physical activity are associated with foetal growth.162 children (24-72 months) were considered: 22 stunted-overweight (SO), 40 stunted (S), 41 overweight (O), and 59 non stunted-non overweight (NSNO). Nutritional status and body composition were assessed using anthropometry and multifrequency bioimpedance analysis. Fasting respiratory quotient (RQ) and REE were measured by indirect calorimetry. Physical activity was determined using accelerometers, food questionnaires were used for diet assessment and birth-weight was noted. Mean RQs and REE (weight adjusted) did not differ between stunted children (SO and S) and non-stunted children (O and NSNO). SO and S children spent more time in sedentary activities than O children (p = 0.01 and p = 0.02, respectively) and less time in moderate-to-vigorous activities than NSNO children (p = 0.05 and p = 0.04, respectively). SO children's diet was less diverse (p = 0.01) with less animal products (p = 0.006). Multiple linear regressions model revealed that birth-weight is predictive of RQ (β = 0.237, p<0.01, R(2) = 0.08).This study showed that growth retardation in stunted-overweight children could be associated with postnatal nutritional deficiencies. Overweight in stunted children could be associated with reduced physical activity in the context of nutrition transition. High birth-weight was a predictor of reduced lipid oxidation, a risk factor of fat deposition

Missense mutation of Brain Derived Neurotrophic Factor (BDNF) alters neurocognitive performance in patients with mild traumatic brain injury: a longitudinal study

The predictability of neurocognitive outcomes in patients with traumatic brain injury is not straightforward. The extent and nature of recovery in patients with mild traumatic brain injury (mTBI) are usually heterogeneous and not substantially explained by the commonly known demographic and injury-related prognostic factors despite having sustained similar injuries or injury severity. Hence, this study evaluated the effects and association of the Brain Derived Neurotrophic Factor (BDNF) missense mutations in relation to neurocognitive performance among patients with mTBI. 48 patients with mTBI were prospectively recruited and MRI scans of the brain were performed within an average 10.1 (SD 4.2) hours post trauma with assessment of their neuropsychological performance post full Glasgow Coma Scale (GCS) recovery. Neurocognitive assessments were repeated again at 6 months follow-up. The paired t-test, Cohen’s d effect size and repeated measure ANOVA were performed to delineate statistically significant differences between the groups [wildtype G allele (Val homozygotes) vs. minor A allele (Met carriers)] and their neuropsychological performance across the time point (T1 = baseline/ admission vs. T2 = 6th month follow-up). Minor A allele carriers in this study generally performed more poorly on neuropsychological testing in comparison wildtype G allele group at both time points. Significant mean differences were observed among the wildtype group in the domains of memory (M = -11.44, SD = 10.0, p = .01, d = 1.22), executive function (M = -11.56, SD = 11.7, p = .02, d = 1.05) and overall performance (M = -6.89 SD = 5.3, p = .00, d = 1.39), while the minor A allele carriers showed significant mean differences in the domains of attention (M = -11.0, SD = 13.1, p = .00, d = .86) and overall cognitive performance (M = -5.25, SD = 8.1, p = .01, d = .66).The minor A allele carriers in comparison to the wildtype G allele group, showed considerably lower scores at admission and remained impaired in most domains across the timepoints, although delayed signs of recovery were noted to be significant in the domains attention and overall cognition. In conclusion, the current study has demonstrated the role of the BDNF rs6265 Val66Met polymorphism in influencing specific neurocognitive outcomes in patients with mTBI. Findings were more detrimentally profound among Met allele carriers

An appraisal of select insect taxa in Sri Lanka

© Springer Science+Business Media Singapore 2016.The chapter provides information on diversity of selected insect taxa, namely, Isoptera, Aphididae, Thysanoptera, Formicidae, and Apidae, and of the rice fields in Sri Lanka. Isoptera of the island comprises 76 species in 29 genera and 4 families, with 33 species restricted to the island. Fauna is rich in wood-feeding foragers and fungus-growing wood feeders and poor in humus and soil feeders. Seventy-four species of aphids in 40 genera and 8 subfamilies have been documented with the exception of subfamily Anoeciinae. Host plant specificity is not so pronounced among aphids except for a few restricted to endemic plants and specific weeds. Thysanoptera are represented by 113 species in 63 genera. Among them are many cosmopolitan pests and several potential viral vector species with vegetables, ornamentals, and cut flowers harboring a large majority of thrips. Ants comprise 181 species in 61 genera and 12 subfamilies. Of special interest is the endemic SF Aneuretinae, solely represented by the relict ant, Aneuretus simony, now known to be widely distributed and abundant. Bees comprise 144 species of pollen bees and 4 species of honeybees in 38 genera and 4 families. Pollen bees are best known for their nesting habits as ground, hollow stem (leaf-cutter bees), and wood (carpenter bees) nesters. Among them are several specialist bees. Rice fields are rich in insects, due to their habitat heterogeneity, harbored 317 species, belonging to 19 orders and 104 families, during the two cultivation cycles, Yala and Maha

Species richness, abundance and feeding habits of termites in three montane forest types in the Knuckles Region

The Knuckle Forest Region has been subjected to heavy logging and land clearing resulting in several fragmented natural forests in montane and lowland regions. Termites are an integral part of tropical forests as decomposers of plant matter into useful humus. Forest termites of Sri Lanka have not been well documented despite their importance in forests. Field studies were conducted in three montane forest types in the Knuckles region to document the species richness and abundance of the termite fauna and to deduce their feeding habitsTermites were sampled in seven belt transects (each 100 x 2 m) laid in seven different forest sites representing three different forest types, namely upper montane (UMF) - 3 sites, dry lower montane (LMF) - 2 sites and wet LMF – 2 sites. Area within a transect was carefully examined for termites by searching all the known microhabitats of termites. Termite abundance was expressed as encounters (hits) with a species at each collection point in a transect. Sampling was supplemented with casual collections in the UMF. Termites were identified using descriptions and keys for the region and feeding groups were deduced from generic identity as well as from molar plate ridges in the right mandible of worker termites using keys and slide mounted mandibles of representative specimensOverall, a species richness of 26 species in three families and 10 genera were recorded, of which 25 species were documented from transects in the wet and dry LMF and none from UMF transects. A single species, Postelectrotermes militaris was recorded through casual collections in the UMF, from a branch of a thunder struck live tree. Fifteen species were documented from the 2-wet LMF transects and 22 from the 2-dry LMF transects. Termite abundance in the wet LMF transects was 86 and in the dry LMF transects 75, totally 161 hits. Documented termites comprised of fungus growing wood feeders (11 spp.), non-fungus growing wood feeders (7 spp.), soil-wood interface feeders (6 spp.), a single soil feeder, Ceylonitermellus hantanae and a single live wood feeder, P. militaris. Wet LMF transects had a higher relative abundance (78%) but low species richness (40%) of soil and soil wood interface feeders. In dry LMF transects both species richness (82%) and abundance (88%) of fungus growing wood feeders were higher.Overall, a species richness of 26 species in three families and 10 genera were recorded, of which 25 species were documented from transects in the wet and dry LMF and none from UMF transects. A single species, Postelectrotermes militaris was recorded through casual collections in the UMF, from a branch of a thunder struck live tree. Fifteen species were documented from the 2-wet LMF transects and 22 from the 2-dry LMF transects. Termite abundance in the wet LMF transects was 86 and in the dry LMF transects 75, totally 161 hits. Documented termites comprised of fungus growing wood feeders (11 spp.), non-fungus growing wood feeders (7 spp.), soil-wood interface feeders (6 spp.), a single soil feeder, Ceylonitermellus hantanae and a single live wood feeder, P. militaris. Wet LMF transects had a higher relative abundance (78%) but low species richness (40%) of soil and soil wood interface feeders. In dry LMF transects both species richness (82%) and abundance (88%) of fungus growing wood feeders were higher