Examination of homogeneity of selected Irish pooling groups

Flood frequency analysis is a necessary and important part of flood risk assessment and management studies. Regional flood frequency methods, in which flood data from groups of catchments are pooled together in order to enhance the precision of flood estimates at project locations, is an accepted part of such studies. This enhancement of precision is based on the assumption that catchments so pooled together are homogeneous in their flood producing properties. If homogeneity is assured then a homogeneous pooling group of sites lead to a reduction in the error of quantile estimates, relative to estimators based on single at-site data series alone. Homogeneous pooling groups are selected by using a previously nominated rule and this paper examines how effective one such rule is in selecting homogeneous groups. In this paper a study, based on annual maximum series obtained from 85 Irish gauging stations, examines how successful a common method of identifying pooling group membership is in selecting groups that actually are homogeneous. Each station has its own unique pooling group selected by use of a Euclidean distance measure in catchment descriptor space, commonly denoted <i>d</i><i><sub>ij</sub></i> and with a minimum of 500 station years of data in the pooling group. It was found that <i>d</i><i><sub>ij</sub></i> could be effectively defined in terms of catchment area, mean rainfall and baseflow index. The study then investigated how effective this selected method is in selecting groups of catchments that are actually homogenous as indicated by their L-Cv values. The sampling distribution of L-CV (<i>t</i><sub>2</sub>) in each pooling group and the 95% confidence limits about the pooled estimate of <i>t</i><sub>2</sub> are obtained by simulation. The <i>t</i><sub>2</sub> values of the selected group members are compared with these confidence limits both graphically and numerically. Of the 85 stations, only 1 station's pooling group members have all their <i>t</i><sub>2</sub> values within the confidence limits, while 7, 33 and 44 of them have 1, 2 or 3 or more, <i>t</i><sub>2</sub> values outside the confidence limits. The outcomes are also compared with the heterogeneity measures H1 and H2. The H1 values show an upward trend with the ranges of <i>t</i><sub>2</sub> values in the pooling group whereas the H2 values do not show any such dependency. A selection of 27 pooling groups, found to be heterogeneous, were further examined with the help of box-plots of catchment descriptor values and one particular case is considered in detail. Overall the results show that even with a carefully considered selection procedure, it is not certain that perfectly homogeneous pooling groups are identified

Fish and human brain evolution

Carlson and Kingston ([2007]: Am J Hum Biol 19:132–141) propose that preformed dietary docosahexaenoic acid (an omega-3 fatty acid in fish) did not have a significant role in hominin encephalization. Their position hinges on claiming that humans are able to make sufficient docosahexaenoic acid from the plant-based \parent" omega-3 fatty acid—alinolenic acid. They also suggest that hominin fish consumption occurred too late to have materially influenced encephalization. The authors quantify here a summary of the published data showing that humans cannot make sufficient docosahexaenoic acid to maintain normal infant brain development. The authors also provide evidence that the fossil record shows that some of the earliest hominins were regularly consuming fish. Hence, we reject Carlson and Kingston’s position and reiterate support for the concept that access to shore-based diets containing docosahexaenoic acid was necessary for hominin encephalization beyond the level seen in the great apes. Am. J. Hum. Biol. 19:578–581, 2007

Extremely limited synthesis of long chain polyunsaturates in adults: implications for their dietary essentiality and use as supplements

La communauté scientifique accorde beaucoup d’intérêt à plusieurs acides gras polyinsaturés (PUFA) et à leur atténuation potentielle du taux de mortalité et de morbidité causée par les maladies dégénératives du système cardiovasculaire et du cerveau. Il n’en demeure pas moins que la confusion demeure au sujet du taux de conversion chez l’humain des PUFA en amont – acide linoléique ou α-linolénique (ALA) – en des substances respectives à plus longue chaîne. On ne connaît toujours pas les bienfaits potentiels de l’ALA en amont de l’acide eicosapentaénoïque (EPA) ou de l’acide docosahexaénoïque (DHA). La confusion est en partie née du fait que les mammifères disposent des enzymes nécessaires pour synthétiser les PUFA à chaîne longue à partir des PUFA en amont alors que les études in vivo chez l’humain révèlent que ≈5 % de l’ALA est converti en EPA et moins de 0,5 % de l’ALA est converti en DHA. Du fait de la très faible capacité de cette voie de synthèse chez des humains en bonne santé non végétariens, même un grand apport alimentaire d’ALA a un effet négligeable sur la concentration plasmatique de DHA ; on observe le même phénomène chez les PUFA oméga-6 : l’apport alimentaire d’acide linoléique a peu d’effet sur la concentration plasmatique de l’acide arachidonique. Nonobstant cette conversion à faible rendement, l’ALA et l’EPA ont potentiellement un rôle à jouer au plan de la santé chez l’humain qui n’a rien à voir avec la conversion en DHA dans la voie de désaturation-élongation des acides gras.Abstract: There is considerable interest in the potential impact of several polyunsaturated fatty acids (PUFAs) in mitigating the significant morbidity and mortality caused by degenerative diseases of the cardiovascular system and brain. Despite this interest, confusion surrounds the extent of conversion in humans of the parent PUFA, linoleic acid or alpha-linolenic acid (ALA), to their respective long-chain PUFA products. As a result, there is uncertainty about the potential benefits of ALA versus eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA). Some of the confusion arises because although mammals have the necessary enzymes to make the long-chain PUFA from the parent PUFA, in vivo studies in humans show that asymptotically equal to 5% of ALA is converted to EPA and <0.5% of ALA is converted to DHA. Because the capacity of this pathway is very low in healthy, nonvegetarian humans, even large amounts of dietary ALA have a negligible effect on plasma DHA, an effect paralleled in the omega6 PUFA by a negligible effect of dietary linoleic acid on plasma arachidonic acid. Despite this inefficient conversion, there are potential roles in human health for ALA and EPA that could be independent of their metabolism to DHA through the desaturation - chain elongation pathway

Plasma Ketone and Medium Chain Fatty Acid Response in Humans Consuming Different Medium Chain Triglycerides During a Metabolic Study Day

Background: Medium chain triglycerides (MCT) are ketogenic but the relationship between the change in plasma ketones and the change plasma medium chain fatty acids (MCFA)—octanoate, decanoate, or dodecanoate—after an oral dose of MCT is not well-known. An 8 h metabolic study day is a suitable model to assess the acute effects on plasma ketones and MCFA after a dose of tricaprylin (C8), tricaprin (C10), trilaurin (C12) or mixed MCT (C8C10).Objective: To assess in healthy humans the relationship between the change in plasma ketones, and octanoate, decanoate and dodecanoate in plasma total lipids during an 8 h metabolic study day in which a first 20 ml dose of the homogenized test oil is taken with breakfast and a second 20 ml dose is taken 4 h later without an accompanying meal.Results: The change in plasma acetoacetate, β-hydroxybutyrate and total ketones was highest after C8 (0.5 to 3 h post-dose) and was lower during tests in which octanoate was absent or was diluted by C10 in the test oil. The plasma ketone response was also about 2 fold higher without an accompanying meal (P = 0.012). However, except during the pure C10 test, the response of octanoate, decanoate or dodecanoate in plasma total lipids to the test oils was not affected by consuming an accompanying meal. Except with C12, the 4 h area-under-the-curve of plasma β-hydroxybutyrate/acetoacetate was 2–3 fold higher when no meal was consumed (P &lt; 0.04).Conclusion: C8 was about three times more ketogenic than C10 and about six times more ketogenic than C12 under these acute metabolic test conditions, an effect related to the post-dose increase in octanoate in plasma total lipids

Survival of the fattest: fat babies were the key to evolution of the large human brain.

Abstract In the past 2 million years, the hominid lineage leading to modern humans evolved significantly larger and more sophisticated brains than other primates. We propose that the modern human brain was a product of having first evolved fat babies. Hence, the fattest (infants) became, mentally, the fittest adults. Human babies have brains and body fat each contributing to 11-14% of body weight, a situation which appears to be unique amongst terrestrial animals. Body fat in human babies provides three forms of insurance for brain development that are not available to other land-based species: (1) a large fuel store in the form of fatty acids in triglycerides; (2) the fatty acid precursors to ketone bodies which are key substrates for brain lipid synthesis; and (3) a store of long chain polyunsaturated fatty acids, particularly docosahexaenoic acid, needed for normal brain development. The triple combination of high fuel demands, inability to import cholesterol or saturated fatty acids, and dependence on docosahexaenoic acid puts the mammalian brain in a uniquely difficult situation compared with other organs and makes its expansion in early humans all the more remarkable. We believe that fresh-and salt-water shorelines provided a uniquely rich, abundant and accessible food supply, and the only viable environment for evolving both body fat and larger brains in human infants.

Does aging change docosahexaenoic acid homeostasis? Implications for the challenge to cognitive health in the elderly

Epidemiological studies fairly convincingly suggest that higher intake of fish and omega-3 fatty acids present in fish is associated with reduced risk for age-related cognitive decline (ARCD). Normally, docosahexaenoic acid (DHA) in plasma is positively associated with DHA intake. However, despite being associated with lower fish and DHA intake, unexpectedly, ARCD is not consistently associated with lower plasma DHA. Furthermore, DHA is often slightly but significantly higher in plasma and erythrocytes in the elderly without ARCD compared to young adults. Higher plasma DHA in the elderly may be a sign that their fish or DHA intake is higher but we show here that various aspects of DHA homeostasis also change with age. Our supplementation and tracer studies show that DHA metabolism, e.g. transit through the plasma and apparent retroconversion but not beta-oxidation, is different in healthy elderly compared to healthy young adults. Apolipoprotein E4 increases the risk of ARCD, possibly in part because it changes DHA homeostasis. Therefore, independent of differences in fish intake, changing DHA homeostasis may contribute to making the elderly more susceptible to cognitive decline despite them having similar or sometimes higher plasma DHA than in younger adults. Key words: aging, cognitive decline, dietary, docosahexaenoic acid, omega-3 fatty aci

A millimeter-wave kinetic inductance detector camera for long-range imaging through optical obscurants

Millimeter-wave imaging provides a promising option for long-range target detection through optical obscurants such as fog, which often occur in marine environments. Given this motivation, we are currently developing a 150 GHz polarization-sensitive imager using a relatively new type of superconducting pair-breaking detector, the kinetic inductance detector (KID). This imager will be paired with a 1.5 m telescope to obtain an angular resolution of 0.09° over a 3.5° field of view using 3,840 KIDs. We have fully characterized a prototype KID array, which shows excellent performance with noise strongly limited by the irreducible fluctuations from the ambient temperature background. Full-scale KID arrays are now being fabricated and characterized for a planned demonstration in a maritime environment later this year

Plasma n-3 fatty acid response to an n-3 fatty acid supplement is modulated by apoE ɛ4 but not by the common PPAR-α L162V polymorphism in men

The risk of Alzheimer's disease is increased for carriers of apoE4 (E4) or the PPAR-α L162V polymorphism (L162V), but it is decreased in fish and seafood consumers. The link between high fish intake and reduced risk of cognitive decline in the elderly appears not to hold in carriers of E4, possibly because better cognition is linked to EPA+DHA in the blood, but only in non-carriers of E4. As yet, no such studies exist in carriers of L162V. Our objective was to determine whether the plasma fatty acid response to a dietary supplement of EPA+DHA was altered in carriers of L162V and/or E4. This was an add-on project; in the original study, men were selected based on whether or not they were carriers of L162V (n 14 per group). E4 status was determined afterwards. All subjects received an EPA+DHA supplement for 6 weeks. L162V polymorphism did not interact with the supplement in a way to alter EPA and DHA incorporation into plasma lipids. However, when the groups were separated based on the presence of E4, baseline EPA and DHA in plasma TAG were 67 and 60 % higher, respectively, in E4 carriers. After the supplementation, there were significant gene × diet interactions in which only non-carriers had increased EPA and DHA in plasma NEFA and TAG, respectively

Can nutrition support healthy cognitive ageing and reduce dementia risk?

● Global prevalence of dementia is predicted to almost triple by 2050 ● There are currently no effective drugs to prevent or treat dementia ● Improved eating behaviour holds significant potential to reduce the risk and population prevalence ● Owing to its multifactorial aetiology, multiple dietary components which target several physiological pathways and risk factors simultaneously are needed. Therefore dietary patterns and foods (rather than single dietary components), hold the most promise to meaningfully improve cognition in the medium term ● Randomised controlled trials with robust validated cognitive outcomes or, ideally, change in dementia or mild cognitive impairment incidence are needed in order to support the prospective cohort evidence, establish efficacy and effect size, and inform public health polic