Unbalanced reduction of nutrient loads has created an offshore gradient from phosphorus to nitrogen limitation in the North Sea

Measures to reduce eutrophication have often led to a more effective decline of phosphorus (P) than nitrogen(N) concentrations. The resultant changes in riverine nutrient loads can cause an increase in the N : Pratios of coastal waters. During four research cruises along a 450 km transect, we investigated how reductionsin nutrient inputs during the past 25 yr have affected nutrient limitation patterns in the North Sea. Thisrevealed a strong offshore gradient of dissolved inorganic N : P ratios in spring, from 375 : 1 nearshoretoward 1 : 1 in the central North Sea. This gradient was reflected in high nearshore N : P and C : P ratios ofparticulate organic matter (mainly phytoplankton), indicative of severe P deficiency of coastal phytoplankton,which may negatively affect higher trophic levels in the food web. Nutrient enrichment bioassays performedon-board showed P and Si limitation of phytoplankton growth nearshore, co-limitation of N and P ina transitional region, and N limitation in the outer-shore waters, confirming the existence of an offshore gradientfrom P to N limitation. Different species were limited by different nutrients, indicating that furtherreductions of P loads without concomitant reductions of N loads will suppress colonial Phaeocystis blooms,but will be less effective in diminishing harmful algal blooms by dino- and nanoflagellates. Hence, our resultsprovide evidence that de-eutrophication efforts in northwestern Europe have led to a large imbalance in theN : P stoichiometry of coastal waters of the North Sea, with major consequences for the growth, species composition,and nutritional quality of marine phytoplankton communities

Predicting Shine–Dalgarno Sequence Locations Exposes Genome Annotation Errors

In prokaryotes, Shine–Dalgarno (SD) sequences, nucleotides upstream from start codons on messenger RNAs (mRNAs) that are complementary to ribosomal RNA (rRNA), facilitate the initiation of protein synthesis. The location of SD sequences relative to start codons and the stability of the hybridization between the mRNA and the rRNA correlate with the rate of synthesis. Thus, accurate characterization of SD sequences enhances our understanding of how an organism's transcriptome relates to its cellular proteome. We implemented the Individual Nearest Neighbor Hydrogen Bond model for oligo–oligo hybridization and created a new metric, relative spacing (RS), to identify both the location and the hybridization potential of SD sequences by simulating the binding between mRNAs and single-stranded 16S rRNA 3′ tails. In 18 prokaryote genomes, we identified 2,420 genes out of 58,550 where the strongest binding in the translation initiation region included the start codon, deviating from the expected location for the SD sequence of five to ten bases upstream. We designated these as RS+1 genes. Additional analysis uncovered an unusual bias of the start codon in that the majority of the RS+1 genes used GUG, not AUG. Furthermore, of the 624 RS+1 genes whose SD sequence was associated with a free energy release of less than −8.4 kcal/mol (strong RS+1 genes), 384 were within 12 nucleotides upstream of in-frame initiation codons. The most likely explanation for the unexpected location of the SD sequence for these 384 genes is mis-annotation of the start codon. In this way, the new RS metric provides an improved method for gene sequence annotation. The remaining strong RS+1 genes appear to have their SD sequences in an unexpected location that includes the start codon. Thus, our RS metric provides a new way to explore the role of rRNA–mRNA nucleotide hybridization in translation initiation

Extending the theory of Owicki and Gries with a logic of progress

This paper describes a logic of progress for concurrent programs. The logic is based on that of UNITY, molded to fit a sequential programming model. Integration of the two is achieved by using auxiliary variables in a systematic way that incorporates program counters into the program text. The rules for progress in UNITY are then modified to suit this new system. This modification is however subtle enough to allow the theory of Owicki and Gries to be used without change

Strong coupling between single-electron tunneling and nano-mechanical motion

Nanoscale resonators that oscillate at high frequencies are useful in many measurement applications. We studied a high-quality mechanical resonator made from a suspended carbon nanotube driven into motion by applying a periodic radio frequency potential using a nearby antenna. Single-electron charge fluctuations created periodic modulations of the mechanical resonance frequency. A quality factor exceeding 10^5 allows the detection of a shift in resonance frequency caused by the addition of a single-electron charge on the nanotube. Additional evidence for the strong coupling of mechanical motion and electron tunneling is provided by an energy transfer to the electrons causing mechanical damping and unusual nonlinear behavior. We also discovered that a direct current through the nanotube spontaneously drives the mechanical resonator, exerting a force that is coherent with the high-frequency resonant mechanical motion.Comment: Main text 12 pages, 4 Figures, Supplement 13 pages, 6 Figure

Comparison of anthropometric body features of highclass volleyball players

One of the factors determining skills of athletes in certain sport is body build features. Sport result depends a lot on morphologic features of the sportsman, that is one of the selective factors determining the sportsman's perspective. Purpose of research is studying of peculiarities anthropomentric and somatometric indices of super league, premier league and first league teams

Cost and color of photosynthesis

The question of why plants are green has been revisited in several articles recently. A common theme in the discussions is to explain why photosynthesis appears to absorb less of the available green sunlight than expected. The expectation is incorrect, however, because it fails to take the energy cost of the photosynthetic apparatus into account. Depending on that cost, the red absorption band of the chlorophylls may be closely optimized to provide maximum growth power. The optimization predicts a strong influence of Fraunhofer lines in the solar irradiance on the spectral shape of the optimized absorption band, which appears to be correct. It does not predict any absorption at other wavelengths