Induction of Cytokinin-Independent Tobacco Tissues by Substituted Fluorenes

Two morphactins and three aminofluorenes initiated the formation of compact tissue nodules in hormone-dependent tobacco callus cultures. These nodules, upon subculture, behaved like partially transformed plant tumors. They grew on cytokinin-free media, while control callus and nonnodule tissue still required an exogenous cytokinin source. The data indicate that substituted fluorenes, including carcinogenic aminofluorenes, can cause a neoplastic growth response in cultured tobacco tissues. Of particular interest in this study is the finding that a directed and heritable cellular change is induced in tobacco tissue in which a specific (the endogenous cytokinin) biosynthetic system is regularly and persistently activated

How does the chromatin fiber deal with topological constraints?

In the nuclei of eukaryotic cells, DNA is packaged through several levels of compaction in an orderly retrievable way that enables the correct regulation of gene expression. The functional dynamics of this assembly involves the unwinding of the so-called 30 nm chromatin fiber and accordingly imposes strong topological constraints. We present a general method for computing both the twist and the writhe of any winding pattern. An explicit derivation is implemented for the chromatin fiber which provides the linking number of DNA in eukaryotic chromosomes. We show that there exists one and only one unwinding path which satisfies both topological and mechanical constraints that DNA has to deal with during condensation/decondensation processes.Comment: Presented in Nature "News and views in brief" Vol. 429 (13 May 2004). Movies available at http://www.lptl.jussieu.fr/recherche/operationE_fichiers/Page_figurePRL.htm

Using LabVIEW to Synchronize an Infrared Diode Laser Spectrometer with a Pulsed Supersonic Jet Expansion

We describe software developed with LabVIEW to provide operational control for an in-house infrared diode laser spectrometer that has been combined with a pulsed supersonic jet expansion sample source. Data were collected with this instrument using a modified version of the rapid-scanning method. A prerequisite in employing the rapid-scan detection scheme is that the modulation used to scan the laser be synchronized in time with the electrical signal used to trigger the pulsed gas valve. Software performance was evaluated by examining a series of rotation vibration (ro-vibrational) spectra for the carbon monoxide molecule in the five micron region of the infrared

The two-angle model and the phase diagram for Chromatin

We have studied the phase diagram for chromatin within the framework of the two-angle model. Rather than improving existing models with finer details our main focus of the work is getting mathematically rigorous results on the structure, especially on the excluded volume effects and the effects on the energy due to the long-range forces and their screening. Thus we present a phase diagram for the allowed conformations and the Coulomb energies

The influence of the cylindrical shape of the nucleosomes and H1 defects on properties of chromatin

We present a model improving the two-angle model for interphase chromatin (E2A model). This model takes into account the cylindrical shape of the histone octamers, the H1 histones in front of the nucleosomes and the vertical distance $d$ between the in and outgoing DNA strands. Factoring these chromatin features in, one gets essential changes in the chromatin phase diagram: Not only the shape of the excluded-volume borderline changes but also the vertical distance $d$ has a dramatic influence on the forbidden area. Furthermore, we examined the influence of H1 defects on the properties of the chromatin fiber. Thus we present two possible strategies for chromatin compaction: The use of very dense states in the phase diagram in the gaps in the excluded volume borderline or missing H1 histones which can lead to very compact fibers. The chromatin fiber might use both of these mechanisms to compact itself at least locally. Line densities computed within the model coincident with the experimental values

Consistent economic cross-sectoral climate change impact scenario analysis: Method and application to Austria

AbstractClimate change triggers manifold impacts at the national to local level, which in turn have various economy-wide implications (e.g. on welfare, employment, or tax revenues). In its response, society needs to prioritize which of these impacts to address and what share of resources to spend on each respective adaptation. A prerequisite to achieving that end is an economic impact analysis that is consistent across sectors and acknowledges intersectoral and economy-wide feedback effects. Traditional Integrated Assessment Models (IAMs) are usually operating at a level too aggregated for this end, while bottom-up impact models most often are not fully comprehensive, focusing on only a subset of climate sensitive sectors and/or a subset of climate change impact chains. Thus, we develop here an approach which applies climate and socioeconomic scenario analysis, harmonized economic costing, and sector explicit bandwidth analysis in a coupled framework of eleven (bio)physical impact assessment models and a uniform multi-sectoral computable general equilibrium model. In applying this approach to the alpine country of Austria, we find that macroeconomic feedbacks can magnify sectoral climate damages up to fourfold, or that by mid-century costs of climate change clearly outweigh benefits, with net costs rising two- to fourfold above current damage cost levels. The resulting specific impact information – differentiated by climate and economic drivers – can support sector-specific adaptation as well as adaptive capacity building

Infrared Diode Laser Spectrometer for the Study of Jet Cooled Gases

We have constructed a tunable, high resolution, infrared diode laser spectrometer and combined it with a pulsed supersonic jet expansion. A modified version of the Perry multipass cell has been incorporated into the spectrometer to increase the effective absorption path length. Performance capabilities of the spectrometer are evaluated by examining ro-vibrational spectra for the carbon monoxide molecule in the five micron region of the infrared. From these measurements, an instrumental absorption sensitivity is determined. Finally, since one of our immediate goals is the infrared study of jet cooled transition metal carbonyls, we present high resolution data obtained by entraining the vapor above a solid metal carbonyl and injecting it into the pulsed jet expansion

Loitering with intent: dealing with human-intensive systems

This paper discusses the professional roles of information systems analysts and users, focusing on a perspective of human intensive, rather than software intensive information systems. The concept of ‘meaningful use’ is discussed in re-lation to measures of success/failure in IS development. The authors consider how a number of different aspects of reductionism may distort analyses, so that processes of inquiry cannot support organizational actors to explore and shape their requirements in relation to meaningful use. Approaches which attempt to simplify complex problem spaces, to render them more susceptible to ‘solution’ are problematized. Alternative perspectives which attempt a systematic, holistic complexification, by supporting contextual dependencies to emerge, are advocated as a way forward

Enhancement of Magneto-Optic Effects via Large Atomic Coherence

We utilize the generation of large atomic coherence to enhance the resonant nonlinear magneto-optic effect by several orders of magnitude, thereby eliminating power broadening and improving the fundamental signal-to-noise ratio. A proof-of-principle experiment is carried out in a dense vapor of Rb atoms. Detailed numerical calculations are in good agreement with the experimental results. Applications such as optical magnetometry or the search for violations of parity and time reversal symmetry are feasible