Sinking properties of some phytoplankton shapes and the relation of form resistance to morphological diversity of plankton – an experimental study

Form resistance (Phi) is a dimensionless number expressing how much slower or faster a particle of any form sinks in a fluid medium than the sphere of equivalent volume. Form resistance factors of PVC models of phytoplankton sinking in glycerin were measured in a large aquarium (0.6 x 0.6 x 0.95 m). For cylindrical forms, a positive relationship was found between Phi and length/ width ratio. Coiling decreased Phi in filamentous forms. Form resistance of Asterionella colonies increased from single cells up to 6-celled colonies than remained nearly constant. For Fragilaria crotonensis chains, no such upper limit to Phi was observed in chains of up to 20 cells ( longer ones were not measured). The effect of symmetry on Phi was tested in 1 - 6-celled Asterionella colonies, having variable angles between the cells, and in Tetrastrum staurogeniaeforme coenobia, having different spine arrangements. In all cases, symmetric forms had considerably higher form resistance than asymmetric ones. However, for Pediastrum coenobia with symmetric/asymmetric fenestration, no difference was observed with respect to symmetry. Increasing number and length of spines on Tetrastrum coenobia substantially increased Phi. For a series of Staurastrum forms, a significant positive correlation was found between arm-length/cell-width ratio and Phi: protuberances increased form resistance. Flagellates (Rhodomonas, Gymnodinium) had a Phi 1. The highest value ( Phi = 8.1) was established for a 20-celled Fragilaria crotonensis chain. Possible origin of the so-called 'vital component' ( a factor that shows how much slower viable populations sink than morphologically similar senescent or dead ones) is discussed, as is the role of form resistance in evolution of high diversity of plankton morphologies

Scaling down the bioimaging of metals by laser microdissection inductively coupled plasma mass spectrometry (LMD-ICP-MS)

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has been established as a powerful quantitative elemental imaging technique in routine mode for biological tissue with a spatial resolution of 12-160 mu m. Several applications necessitate an improved spatial resolution of LA-ICP-MS at the low micrometre scale and below. To achieve the improvement of spatial resolution of LA-ICP-MS we created a new experimental arrangement by coupling a laser microdissection system (LMD) used for laser ablation of tissue with a sensitive quadrupole-based inductively coupled plasma mass spectrometer for the subsequent analysis of ablated material. A flat laser ablation chamber made of glass was inserted into the LMD, fitted to the microscope slide with the specimen. The biological tissue fixed on the glass slide was ablated using the focused solid-state Nd:YAG laser of the LMD. The laser ablated material was transported by argon as carrier gas into the inductively coupled plasma of the mass spectrometer and analysed according to the mass-to-charge ratio. Using this novel LMD-ICP-MS arrangement, in initial experiments ion signals of 63Cu* and 65Cte were measured from a 30-p.m-thick cryosection impregnated with a droplet of a Cu solution. A spatial resolution of about 3 pm was obtained using the modified LMD system coupled to the ICP-MS. Laser-induced mass spectrometric measurements of metal distributions can be performed together with simultaneous inspection of the tissue section via the microscope of the LMD and be combined with other modalities of the LMD system. In future, a more powerful laser in the LMD apparatus will allow ablation down to the sub-micrometre scale to study the elemental distribution in small tissue sections. (C) 2010 Elsevier By. All rights reserved

A partial-wave analysis of the (K+^{+}K−^{-}pi−^{-}) system produced in pi−^{-}p --> K+^{+}K−^{-}pi−^{-}p at 16 GeV/c

The reaction\pi^{-}p to K^{+}K^{-}\pi^{-}p at 16 GeV/c was studied in the CERN OMEGA spectrometer and a partial-wave analysis (PWA) of the low-mass (K^{+}K^{-}\pi^{-}) system (1.3-2.0 Ge V) was performed. Only states in the unnatural spin-parity series produced by natural parity exchange are important and they approximately conserve t-channel helicity. The 1^{+}S K*K wave dominates the low-mass (K^{+}K^{-}\pi^{-}) region. The authors observe an enhancement in the 2^{-}P K*K wave at a mass of 1.7 GeV, consistent with the decay of the A/sub 3/ resonance

A high statistics search for the pˉpπ−\bar{p}p\pi^{-} mass enhancement at 2.95 GeV

An experiment has been undertaken at the CERN SPS, using the Omega spectrometer, aimed at confirming the enhancement observed in a pp pi /sup -/ mass spectrum at 2.95 GeV. With statistics of twelve times the original experiment no signal is seen. In the reaction pi /sup -/p to pp pi /sup -/p, the upper limit (four standard deviations) for the production of a resonance in the pp pi /sup -/system at 2.95 GeV, with a width <or=30 MeV, is 50 nb. (3 refs)