Neutral Hydrogen Associated with NGC 7129

Observations of the environment of the star-forming region NGC 7129 obtained with an angular resolution of 1' in the 21 cm line of H I are described. Two features of the image are extensively discussed: (1) a ring of H I emission about 30' in extent and (2) a relatively dense concentration of H I with unusually wide line profiles positionally coincident with the B star BD +65°1638. The H I ring is consistent with photodissociation of H2 by the interstellar UV radiation field at the surface of an extended molecular cloud in which both BD +65°1638 and NGC 7129 are situated. We further show that BD +65°1638 appears to be an unusual example of a "dissociating star" surrounded by an extensive region of photodissociated H2 and accompanied by a small H II region. The derived spectral type (B2.5) and the absolute magnitude for BD +65°1638 further suggest that the latter is very close to the birthline. The very young stellar age implied by the parameters of the H I region, considerably less than 104 yr, is discussed, and the properties of the H I region are compared with those of the prototype for this rare class of objects. We discuss both aspects within the context of star formation in NGC 7129

The \u3cem\u3eChlamydomonas\u3c/em\u3e Genome Reveals the Evolution of Key Animal and Plant Functions

Chlamydomonas reinhardtii is a unicellular green alga whose lineage diverged from land plants over 1 billion years ago. It is a model system for studying chloroplast-based photosynthesis, as well as the structure, assembly, and function of eukaryotic flagella (cilia), which were inherited from the common ancestor of plants and animals, but lost in land plants. We sequenced the ∼120-megabase nuclear genome of Chlamydomonas and performed comparative phylogenomic analyses, identifying genes encoding uncharacterized proteins that are likely associated with the function and biogenesis of chloroplasts or eukaryotic flagella. Analyses of the Chlamydomonas genome advance our understanding of the ancestral eukaryotic cell, reveal previously unknown genes associated with photosynthetic and flagellar functions, and establish links between ciliopathy and the composition and function of flagella

Politics and war in the sixteenth century state

A note on terminology.Throughout, the term 'Holland' is used to apply only to the province of that name. Similarly, where 'Flanders' appears in the text it applies only to that province, although commonly used by contemporaries to designate the Netherlands as a whole. 'Dutch' is employed as a convenient shorthand for the inhabitants of the rebel provinces, but 'Belgian' has been avoided for the southern provinces because it implies a predetermined racial/ national division in the Netherlands. 'Spanish' is used generally to describe the government and the armed forces operating against the United Provinces even though, in the armed forces, Spaniards were themselves a small minority. This is justified by the commanding position held by the servants of Madrid during this period. Rather than adopt a slavish consistency with place names, we have employed forms familiar to English speakers, such as The Hague (Den Haag), Antwerp (Antwerpen), Flushing (Vlissingen). Elsewhere, the form familiar to the inhabitants has been employed (Mechlin for Malines, Liege for Luik). Dates are given according to the 'New Style' except where otherwise stated, or where it is unclear which style is being used.</p

Will changes in climate and land use affect soil organic matter composition? Evidence from an ecotonal climosequence

As the largest actively cycling pool of terrestrial C, the response of soil organic matter (SOM) to climate change may greatly affect global C cycling and climate change feedbacks. Despite the influence of SOM chemistry—here defined as soil organic C (SOC) and soil organic N (SON) functional groups and compounds—on decomposition, uncertainty exists regarding the response of SOM chemistry to climate change and associated land use shifts. Here, we adopt a climosequence approach, using latitude along a uniform glacial till deposit at the grassland–forest ecotone in central Canada as a surrogate for the effects of climate change on SOM chemistry. Additionally, we evaluate differences in SOM chemistry from paired native grassland, native trembling aspen (Populus tremuloides) forest, and arable soil profiles to investigate the effects of likely climate-induced land use alterations. The combination of C and N K-edge X-ray absorption near edge structure (XANES) with pyrolysis-field ionization mass spectrometry (Py-FIMS) techniques was used to examine SOM chemistry at atomic and molecular scales, respectively. These techniques revealed only modest differences in surface SOM chemistry related to land use and latitude. Greater variation was apparent in the vertical stratification of SOM constituents from soil depth profiles. These findings indicate that pedon-scale processes have greater control over SOM chemistry than do processes operating on landscape (e.g. land use) and regional (e.g. climate) scales. Additionally they imply that SOM chemistry is largely unresponsive to climatic change on the magnitude of the mean annual temperature (MAT) gradient under study (~ 0.7 °C), despite its location at the grassland–forest boundary highlighting its sensitivity, and is similarly unresponsive to associated land use shifts

Neutral hydrogen associated with NGC 7129

NRC publication: Ye

Modification of electron transfer from the quinone electron carrier, A(1), of Photosystem 1 in a site directed mutant D576 double right arrow L within the Fe-S(x) binding site of PsaA and in second site suppressors of the mutation in Chlamydomonas reinhardtii

A site directed mutant of the Photosystem I reaction center of Chlamydomonas reinhardtii has been described previously. [Hallahan et al. (1995) Photosynth Res 46: 257–264]. The mutation, PsaA: D576L, changes the conserved aspartate residue adjacent to one of the cysteine ligands binding the Fe-SX center to PsaA. The mutation, which prevents photosynthetic growth, was observed to change the EPR spectrum of the Fe-SA/B centers bound to the PsaC subunit. We suggested that changes in binding of PsaC to the PsaA/PsaB reaction center prevented efficient electron transfer. Second site suppressors of the mutation have now been isolated which have recovered the ability to grow photosynthetically. DNA analysis of four suppressor strains showed the original D576L mutation is intact, and that no mutations are present elsewhere within the Fe-SX binding region of either PsaA or PsaB, nor within PsaC or PsaJ. Subsequent genetic analysis has indicated that the suppressor mutation(s) is nuclear encoded. The suppressors retain the altered binding of PsaC, indicating that this change is not the cause of failure to grow photosynthetically. Further analysis showed that the rate of electron transfer from the quinone electron carrier A1 to Fe-SX is slowed in the mutant (by a factor of approximately two) and restored to wild type rates in the suppressors. ENDOR spectra of A1·– in wild-type and mutant preparations are identical, indicating that the electronic structure of the phyllosemiquinone is not changed. The results suggest that the quinone to Fe-SX center electron transfer is sensitive to the structure of the iron-sulfur center, and may be a critical step in the energy conversion process. They also indicate that the structure of the reaction center may be modified as a result of changes in proteins outside the core of the reaction center

The sites of interaction of triphenyltetrazolium chloride with mitochondrial respiratory chains

The inability of cells and microorganisms to reduce the colourless electron acceptor triphenyltetrazolium chloride (TTC) to a red formazan precipitate is commonly used as a means of screening for cells that have a dysfunctional respiratory chain. The site of reduction of TTC is often stated to be at the level of cytochrome c oxidase where it is assumed to compete with oxygen for reducing equivalents. However, we show here that TTC is reduced not by cytochrome c oxidase but instead by dehydrogenases, particularly complex I, probably by accepting electrons directly from low potential cofactors. The reduction rate is fastest in coupled membranes because of accumulation in the matrix of the positively charged TTC+ cation. However, the initial product of TTC reduction is rapidly reoxidised by molecular oxygen, so that generation of the stable red formazan product from this intermediate occurs only under strictly anaerobic conditions. Colonies of mutants defective in cytochrome oxidase do not generate sufficiently anaerobic conditions to allow the intermediate to form the stable red formazan. This revision of the mode of interaction of TTC with respiratory chains has implications for the types of respiratory-defective mutants that might be detected by TTC screening.Rich, Peter R. ; Mischis, Lidia A. ; Purton, Saul ; Wiskich, Joseph T