Putting geography into phycology: recent advances

In the last decade, ecological and biogeographical studies (mainly terrestrial) have greatly benefited from recent developments in geographical techniques, and numerous test cases have been published. However, very few phycological studies emphasizing ecology and biogeography have incorporated these techniques, using traditional, nonspatially explicit descriptive and multivariate statistics instead. Here, we show a satellitebased seasonal mapping study of macroalgal communities in the Arabian Sea, and a global species’ distribution modelling effort of a cryptic green algal complex forming worldwide blooms on physically damaged coral reefs. We demonstrate how spatially explicit information contributes to more efficient work and new insights in marine ecology and biogeography, and comment on why previous studies did not include geographical techniques. Lastly, we briefly discuss future perspectives of spatially explicit phycological studies

Subjective experience of episodic memory and metacognition: a neurodevelopmental approach.

Episodic retrieval is characterized by the subjective experience of remembering. This experience enables the co-ordination of memory retrieval processes and can be acted on metacognitively. In successful retrieval, the feeling of remembering may be accompanied by recall of important contextual information. On the other hand, when people fail (or struggle) to retrieve information, other feelings, thoughts, and information may come to mind. In this review, we examine the subjective and metacognitive basis of episodic memory function from a neurodevelopmental perspective, looking at recollection paradigms (such as source memory, and the report of recollective experience) and metacognitive paradigms such as the feeling of knowing). We start by considering healthy development, and provide a brief review of the development of episodic memory, with a particular focus on the ability of children to report first-person experiences of remembering. We then consider neurodevelopmental disorders (NDDs) such as amnesia acquired in infancy, autism, Williams syndrome, Down syndrome, or 22q11.2 deletion syndrome. This review shows that different episodic processes develop at different rates, and that across a broad set of different NDDs there are various types of episodic memory impairment, each with possibly a different character. This literature is in agreement with the idea that episodic memory is a multifaceted process

XTH acts at the microfibril-matrix interface during cell elongation

Sulphorhodamine-labelled oligosaccharides of xyloglucan are incorporated into the cell wall of Arabidopsis and tobacco roots, and of cultured Nicotiana tabacum cells by the transglucosylase (XET) action of XTHs. In the cell wall of diffusely growing cells, the subcellular pattern of XET action revealed a 'fibrillar' pattern, different from the xyloglucan localization. The fibrillar fluorescence pattern had no net orientation in spherical cultured cells. It changed to transverse to the long axis when the cells started to elongate, a feature mirroring the rearrangements of cortical microtubules and the accompanying cellulose deposition. Interference with the polymerization of microtubules and with cellulose deposition inhibited this strong and 'fibrillar'-organized XET-action, whereas interference with actin-polymerization only decreased the intensity of enzyme action. Epidermal cells of a mutant with reduced cellulose synthesis also had low XET action. Root hairs (tip-growing cells) exhibited high XET-action over all their length, but lacked the specific parallel pattern. In both diffuse- and tip-growing cell types extraction of the incorporated fluorescent xyloglucans by a xyloglucan-specific endoglucanase reduced the fluorescence, but the 'fibrillar' appearance in diffuse growing cells was not eliminated. These results show that XTHs act on the xyloglucans attached to cellulose microfibrils. After incorporation of the fluorescent oligosaccharides, the xyloglucans decorate the cellulose microfibrils and become inaccessible to hydrolytic enzymes

Ab initio study of charge transport through single oxygen molecules in atomic aluminum contacts

We present ab initio calculations of transport properties of atomic-sized aluminum contacts in the presence of oxygen. The experimental situation is modeled by considering a single oxygen atom (O) or one of the molecules O2 and O3 bridging the gap between electrodes forming ideal, atomically sharp pyramids. The transport characteristics are computed for these geometries with increasing distances between the leads, simulating the opening of a break junction. To facilitate comparison with experiments further, the vibrational modes of the oxygen connected to the electrodes are studied. It is found that in the contact regime the change of transport properties due to the presence of oxygen is strong and should be detectable in experiments. All three types of oxygen exhibit a comparable behavior in their vibrational frequencies and conductances, which are well below the conductance of pure aluminum atomic contacts. The conductance decreases for an increasing number of oxygen atoms. In the tunneling regime the conductance decays exponentially with distance and the decay length depends on whether or not oxygen is present in the junction. This fact may provide a way to identify the presence of a gas molecule in metallic atomic contacts.Comment: 8 pages, 9 figures; added appendi

Fractionating controlled memory processes and recall of context in recognition memory: a case report.

Recollection has been described as both a recognition memory judgment requiring cognitive control and the ability to retrieve contextual information about a prior occurrence. At the core of this article is the question whether or not these two subcomponents of recollection are dissociable in amnesia. In three experiments, we explored the influence of exclusion task instructions on performance in a single case (CJ), with the view to understand the relative contributions of control and source memory to recognition memory decisions. First, contrasting findings were obtained between tasks requiring strategic control or source reports. Second, even though CJ displayed some residual source memory relative to the ability to strategically control this information, his source memory capacity was time-limited. Our findings resonate with the novel proposal that recollection draws heavily upon working memory resources, and provide an example of how amnesic patients might utilize residual working memory capacity to solve episodic memory tasks

Molecular dynamics study of the thermopower of Ag, Au, and Pt nanocontacts

Using molecular dynamics simulations of many junction stretching processes we analyze the thermopower of silver (Ag), gold (Au), and platinum (Pt) atomic contacts. In all cases we observe that the thermopower vanishes on average within the standard deviation and that its fluctuations increase for decreasing minimum cross-section of the junctions. However, we find a suppression of the fluctuations of the thermopower for the s-valent metals Ag and Au, when the conductance originates from a single, perfectly transmitting channel. Essential features of the experimental results for Au, Ag, and copper (Cu) of Ludoph and van Ruitenbeek [Phys. Rev. B 59, 12290 (1999)], as yet unaddressed by atomistic studies, can hence be explained by considering the atomic and electronic structure at the disordered narrowest constriction of the contacts. For the multivalent metal Pt our calculations predict the fluctuations of the thermopower to be larger by one order of magnitude as compared to Ag and Au, and suppressions of the fluctuations as a function of the conductance are absent.Comment: 13 pages, 10 figure

Length-dependent conductance and thermopower in single-molecule junctions of dithiolated oligophenylene derivatives

We study theoretically the length dependence of both conductance and thermopower in metal-molecule-metal junctions made up of dithiolated oligophenylenes contacted to gold electrodes. We find that while the conductance decays exponentially with increasing molecular length, the thermopower increases linearly as suggested by recent experiments. We also analyze how these transport properties can be tuned with methyl side groups. Our results can be explained by considering the level shifts due to their electron-donating character as well as the tilt-angle dependence of conductance and thermopower. Qualitative features of the substituent effects in our density-functional calculations are explained using a tight-binding model. In addition, we observe symmetry-related even-odd transmission channel degeneracies as a function of molecular length.Comment: 7 pages, 9 figures; submitted to Phys. Rev.