Nutrition and food limitation of deposit-feeders. II. Differential effects of Hydrobia totteni and Ilyanassa obsoleta on the microbial community

We examined the effects of the mud snails Hydrobia totteni and Ilyanassa obsoleta on microbial communities of sediments in microcosms. Varying density of Hydrobia, and the presence of Ilyanassa, exerted no effect on steady state bacterial standing stock. This is probably related to the rapid recovery rate of bacteria, despite efficient grazing...

Nutrition and food limitation of deposit-feeders. I. The role of microbes in the growth of mod snails (Hydrobiidae)

A series of laboratory microcosm experiments demonstrate that somatic growth of the deposit-feeding gastropod, Hydrobia totteni, is related strongly to microalgal standing stock. Microalgal standing stock is, in turn, determined by the relative rates of grazing and recovery...

The importance of microalgae, bacteria and particulate organic matter in the somatic growth of Hydrobia totteni

Laboratory microcosm experiments reveal that benthic microalgae (filamentous blue-green and diatoms) probably constitute the bulk of nutrition in the somatic growth of the deposit feeding mud snail Hydrobia totteni. Despite an apparent excess of nitrogen in the particulate fraction of the sediment, H. totteni grows only about 42% as much in the dark as in the light. Growth in the dark is probably explained by the utilization of filamentous blue greens and, to a lesser extent, bacteria. The additional growth in the light is probably explained by benthic diatoms, as shown in previous studies. Standing-stocks of micro-organisms (bacteria and microalgae) and snail densities (0.5 cm–2, 2.0 cm–2) in laboratory treatments lie within the range of field conditions. A comparison of snail growth in oxidized and nonoxidized sediments, shows that particulate organic matter typically found in salt marsh sediments does not contribute substantially to somatic growth in H. totteni. Added rations of the seaweed Ulva rotundata also did not affect snail growth. Much of the available nitrogen may have been mineralized into the water column because Ulva is readily decomposed

Brain Age from the Electroencephalogram of Sleep

The human electroencephalogram (EEG) of sleep undergoes profound changes with age. These changes can be conceptualized as "brain age", which can be compared to an age norm to reflect the deviation from normal aging process. Here, we develop an interpretable machine learning model to predict brain age based on two large sleep EEG datasets: the Massachusetts General Hospital sleep lab dataset (MGH, N = 2,621) covering age 18 to 80; and the Sleep Hearth Health Study (SHHS, N = 3,520) covering age 40 to 80. The model obtains a mean absolute deviation of 8.1 years between brain age and chronological age in the healthy participants in the MGH dataset. As validation, we analyze a subset of SHHS containing longitudinal EEGs 5 years apart, which shows a 5.5 years difference in brain age. Participants with neurological and psychiatric diseases, as well as diabetes and hypertension medications show an older brain age compared to chronological age. The findings raise the prospect of using sleep EEG as a biomarker for healthy brain aging

The abelian cosets of the Heisenberg group

In this paper we study the abelian cosets of the H(4) WZW model. They coincide or are related to several interesting three-dimensional backgrounds such as the Melvin model, the conical point-particle space-times and the null orbifold. We perform a detailed CFT analysis of all the models and compute the coset characters as well as some typical three-point couplings of coset primaries.Comment: 26 pages; v2: minor typos corrected, also added section 3.3 and 4.3 with a few comments on a third class of geometries that have not been discussed in v

Variability in the Bulk Composition and Abundance of Dissolved Organic Matter In the Lower Mississippi and Pearl Rivers

[1] In this study, we examined the temporal and spatial variability of dissolved organic matter (DOM) abundance and composition in the lower Mississippi and Pearl rivers and effects of human and natural influences. In particular, we looked at bulk C/N ratio, stable isotopes (delta N-15 and delta C-13) and C-13 nuclear magnetic resonance (NMR) spectrometry of high molecular weight (HMW; 0.2 mu m to 1 kDa) DOM. Monthly water samples were collected at one station in each river from August 2001 to 2003. Surveys of spatial variability of total dissolved organic carbon (DOC) and nitrogen ( DON) were also conducted in June 2003, from 390 km downstream in the Mississippi River and from Jackson to Stennis Space Center in the Pearl River. Higher DOC ( 336 - 1170 mu M), C/N ratio,% aromaticity, and more depleted delta N-15 (0.76 - 2.1 parts per thousand) were observed in the Pearl than in the lower Mississippi River (223 - 380 mu M, 4.7 - 11.5 parts per thousand, respectively). DOC, C/N ratio, delta C-13, delta N-15, and % aromaticity of Pearl River HMW DOM were correlated with water discharge, which indicated a coupling between local soil inputs and regional precipitation events. Conversely, seasonal variability in the lower Mississippi River was more controlled by spatial variability of a larger integrative signal from the watershed as well as in situ DOM processing. Spatially, very little change occurred in total DOC in the downstream survey of the lower Mississippi River, compared to a decrease of 24% in the Pearl River. Differences in DOM between these two rivers were reflective of the Mississippi River having more extensive river processing of terrestrial DOM, more phytoplankton inputs, and greater anthropogenic perturbation than the Pearl River

Mersenne Primes, Polygonal Anomalies and String Theory Classification

It is pointed out that the Mersenne primes $M_p=(2^p-1)$ and associated perfect numbers ${\cal M}_p=2^{p-1}M_p$ play a significant role in string theory; this observation may suggest a classification of consistent string theories.Comment: 10 pages LaTe