33 research outputs found
Electronic data safes as an infrastructure for transformational government? A case study
This article introduces and explores the potential of an active electronic data safe (AEDS) serving as an infrastructure to achieve transformational government. An AEDS connects individuals and organizations from the private and the public sector to exchange information items related to business processes following the user-managed access paradigm. To realize the transformational government’s vision of user-centricity, fundamental changes in the service provision and collaboration of public and private sector organizations are needed. Findings of a user study with a prototype of an AEDS are used to identify four barriers for the adoption of an AEDS in the light of transformational government: (1.) offering citizens unfamiliar services having the character of experience-goods; (2.) failing to fulfill common service expectations of the customers; (3.) failing to establish contextual integrity for data sharing, and, (4.) failing to establish and run an AEDS as a multi-sided platform providing an attractive business model
Electrogenic sodium-bicarbonate cotransport in human ciliary muscle cells
We investigated membrane voltage and intracellular pH (pHi) in cultured human ciliary muscle cells using a cell line (H7CM) and primary-cultured human ciliary muscle cells. 1) Resting potential was 58.9 +/- 1.0 mV in H7CM cells and 61.9 +/- 1.4 mV in primary cultures. The following data are from H7CM cells, but results from primary cultures were basically similar. 2) In HCO3(-)-CO2-buffered solution, removal of extracellular sodium resulted in a depolarization [change in membrane resistance (delta V) = 31.3 +/- 2.8 mV] that was less marked in the absence of HCO3(-)-CO2 (delta V = 0.5 +/- 2.6 mV) and reduced by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) (delta V = 19.3 +/- 1.9 mV). 3) Removal of extracellular HCO3(-)-CO2 led to a depolarization (delta V = 13.2 +/- 0.8 mV) that was abolished in the absence of extracellular sodium and inhibited by DIDS. 4) Intracellular alkalinization led to a depolarization (delta V = 24.7 +/- 2.3 mV), and intracellular acidification resulted in a hyperpolarization (delta V = 9.4 +/- 1.1 mV) that was inhibited by DIDS and dependent on extracellular HCO3(-)-CO2 and sodium. 5) pHi backregulation after an acid load occurred in both the presence and absence of extracellular bicarbonate but not in the absence of extracellular sodium. Our data are consistent with an electrogenic Na(+)-HCO3- cotransport in human ciliary muscle cells, which is activated by intracellular acidification
Localization of the glnD gene on a revised map of the 200- kilobase region of the Escherichia coli chromosome
Localization of the glnD gene on a revised map of the 200-kilobase region of the Escherichia coli chromosome.
In the course of our studies on the glutamine synthetase regulatory cascade, we have characterized the physical location of the glnD gene, encoding the uridylyl-transferase which is thought to be the primary sensor of cellular nitrogen status (13). This gene is linked to dapD, and we therefore analyzed two lambda phages from the Kohara library (9, 9a), 9H2 and 21C8, mapping in the dapD region (3.8 min, 190 kb) (12). To identify the physical location ofginD, we made use of a glnD::TnlO insertion in strain RB9040 (3). Southern blotting of PstI-, EcoRI-, and EcoRI-SalI-digested genomic DNAs of RB9040 and its wild-type parent RB9010, using 21C8 phage DNA as a probe, showed that the physical map of the hybridizing region of the chromosome corresponds to the physical map of 21C8, indicating the absence of rear-rangement in phage 21C8. This experiment also located th
Predicting The Post-fire Establishment And Persistence Of An Invasive Tree Species Across A Complex Landscape
The reintroduction of pre-European fire regimes has allowed the entry of many invasive plant species into fire-dependant ecosystems of North America. However, the environmental factors that favor the post-fire establishment of these species across complex landscapes are not well understood and the initial establishment of invasive species does not necessarily result in long-term persistence. To evaluate the post-fire establishment and persistence of disturbance-dependent invasive plants, we studied the invasion of Paulownia tomentosa (princess tree, an early-successional species introduced from Asia) across three burns in the southern Appalachian Mountains. Based upon classification tree analysis, the presence/absence of P. tomentosa 2 years after burning was most strongly related to the cover of residual vegetation, topographic shading, and moisture availability. Spatial application of classification tree models to repeated survey data showed that P. tomentosa established across a wide range of microsites 2 years after burning. However, predicted habitat for P. tomentosa decreased by 63% 4 years after fire and by 73% 6 years after fire. Following its initial widespread establishment, P. tomentosa only persisted on xeric and exposed topographic positions that experienced high intensity burning. However, the sites where it persisted include rare community types that contain two endangered plant species that depend upon fire for successful reproduction. The control of P. tomentosa on these ecologically important sites may require special attention from land managers
A major isoform of the maize plasma membrane H(+)-ATPase: characterization and induction by auxin in coleoptiles.
The plasma membrane (PM) H(+)-ATPase has been proposed to play important transport and regulatory roles in plant physiology, including its participation in auxin-induced acidification in coleoptile segments. This enzyme is encoded by a family of genes differing in tissue distribution, regulation, and expression level. A major expressed isoform of the maize PM H(+)-ATPase (MHA2) has been characterized. RNA gel blot analysis indicated that MHA2 is expressed in all maize organs, with highest levels being in the roots. In situ hybridization of sections from maize seedlings indicated enriched expression of MHA2 in stomatal guard cells, phloem cells, and root epidermal cells. MHA2 mRNA was induced threefold when nonvascular parts of the coleoptile segments were treated with auxin. This induction correlates with auxin-triggered proton extrusion by the same part of the segments. The PM H(+)-ATPase in the vascular bundies does not contribute significantly to auxin-induced acidification, is not regulated by auxin, and masks the auxin effect in extracts of whole coleoptile segments. We conclude that auxin-induced acidification in coleoptile segments most often occurs in the nonvascular tissue and is mediated, at least in part, by increased levels of MHA2