Aluminium induced changes in the morphology of the quiescent centre, proximal meristem and growth region of the root of Zea mays

Treatment of the primary root with 8 mg dm-3 Al altered the pattern of cell growth so that with 48–h treatment, the root apex was no longer an organized, cytologically heterogeneous complex. An increase in mean cell volume was first observed with 2–h treatment, primarily in the cells of the quiescent centre where cell enlargement was associated with the removal of the constraint to quiescence by Al and in the mid-cortex 1–2 mm from the root tip where growth stimulation was associated with a departure from osmotic equilibrium. An initial increase in the osmotic potential of the root cell sap arising from Al treatment (1 h) was not maintained and subsequent decreases in the osmotic potential coincided with changes in the cell growth direction. Stress patterns arising from the anisotropic growth response of cortical cells with 20–h root exposure to Al were associated with the collapse of the conducting tissue of the stele and disintegration of the outer cells of the root. Advanced vacuolation of the cells of the root apex, first observed with 5–h treatment, was a feature of Al-stressed roots. Alteration to the nuclear structure in cells of the proximal meristem involving the degree of chromatin condensation and structure of the nucleolus was considered indicative of senescence. S. Afr. J. Bot. 1985, 51: 355–362Behandeling van die primêre wortel met 8 mg dm−3 Al het die patroon van selgroei verander, sodat die wortelpunt na blootstelling van 48 h nie meer ‘n sitologies-georganiseerde geheel was nie. ‘n Toename in die gemiddelde selvolume is na blootstelling van 2 h waargeneem, hoofsaaklik in die selle van die rustende gebied, waar die vergroting van selle geassosieer is met die opheffing van die rustoestand, en in die sentrale korteks, 1–2 mm vanaf die wortelpunt, waar die aanvangsgroei gestimuleer is deur ‘n afwyking vanaf osmotiese ewewig. Die aanvanklike verhoging in die osmotiese potensiaal van die selsap, as gevolg van die Al-behandeling (1 h), is nie volgehou nie; die verlaging in osmotiese potensiaal het ooreengestem met veranderings in die rigting van selgroei. Spanningspatrone wat voortspruit uit die anisotropiese groeireaksie van die korteksselle na 20 h se blootstelling van die wortel aan Al, is geassosieer met die ineenstorting van die geleidingsweefsel van die stele en die disintegrasie van die wortels se epidermis. Gevorderde vakuolering van die wortelpuntselle wat vir die eerste keer opgemerk is met die 5 h-blootstelling is ‘n kenmerk van wortels wat aan Al blootgestel is. Veranderings in die kernstruktuur van die selle van die proksimale meristeem ten opsigte van die graad van chromatienkondensering in die struktuur van die nukleolus is beskou as aanduidings van veroudering. S.-Afr. Tydskr. Plantk. 1985, 51: 355–36

High-precision determination of transition amplitudes of principal transitions in Cs from van der Waals coefficient C_6

A method for determination of atomic dipole matrix elements of principal transitions from the value of dispersion coefficient C_6 of molecular potentials correlating to two ground-state atoms is proposed. The method is illustrated on atomic Cs using C_6 deduced from high-resolution Feshbach spectroscopy. The following reduced matrix elements are determined < 6S_{1/2} || D || 6P_{1/2} > =4.5028(60) |e| a0 and =6.3373(84) |e| a0 (a0= 0.529177 \times 10^{-8} cm.) These matrix elements are consistent with the results of the most accurate direct lifetime measurements and have a similar uncertainty. It is argued that the uncertainty can be considerably reduced as the coefficient C_6 is constrained further.Comment: 4 pages; 3 fig

Strict selection alone of patients undergoing liver transplantation for hilar cholangiocarcinoma is associated with improved survival

Liver transplantation for hilar cholangiocarcinoma (hCCA) has regained attention since the Mayo Clinic reported their favorable results with the use of a neo-adjuvant chemoradiation protocol. However, debate remains whether the success of the protocol should be attributed to the neo-adjuvant therapy or to the strict selection criteria that are being applied. The aim of this study was to investigate the value of patient selection alone on the outcome of liver transplantation for hCCA. In this retrospective study, patients that were transplanted for hCCA between1990 and 2010 in Europe were identified using the European Liver Transplant Registry (ELTR). Twenty-one centers reported 173 patients (69%) of a total of 249 patients in the ELTR. Twenty-six patients were wrongly coded, resulting in a study group of 147 patients. We identified 28 patients (19%) who met the strict selection criteria of the Mayo Clinic protocol, but had not undergone neo-adjuvant chemoradiation therapy. Five-year survival in this subgroup was 59%, which is comparable to patients with pretreatment pathological confirmed hCCA that were transplanted after completion of the chemoradiation protocol at the Mayo Clinic. In conclusion, although the results should be cautiously interpreted, this study suggests that with strict selection alone, improved survival after transplantation can be achieved, approaching the Mayo Clinic experience

Towards a self-deploying and gliding robot

Strategies for hybrid locomotion such as jumping and gliding are used in nature by many different animals for traveling over rough terrain. This combination of locomotion modes also allows small robots to overcome relatively large obstacles at a minimal energetic cost compared to wheeled or flying robots. In this chapter we describe the development of a novel palm sized robot of 10\,g that is able to autonomously deploy itself from ground or walls, open its wings, recover in midair and subsequently perform goal- directed gliding. In particular, we focus on the subsystems that will in the future be integrated such as a 1.5\,g microglider that can perform phototaxis; a 4.5\,g, bat-inspired, wing folding mechanism that can unfold in only 50\,ms; and a locust-inspired, 7\,g robot that can jump more than 27 times its own height. We also review the relevance of jumping and gliding for living and robotic systems and we highlight future directions for the realization of a fully integrated robot

Prospects for e+e- physics at Frascati between the phi and the psi

We present a detailed study, done in the framework of the INFN 2006 Roadmap, of the prospects for e+e- physics at the Frascati National Laboratories. The physics case for an e+e- collider running at high luminosity at the phi resonance energy and also reaching a maximum center of mass energy of 2.5 GeV is discussed, together with the specific aspects of a very high luminosity tau-charm factory. Subjects connected to Kaon decay physics are not discussed here, being part of another INFN Roadmap working group. The significance of the project and the impact on INFN are also discussed. All the documentation related to the activities of the working group can be found in http://www.roma1.infn.it/people/bini/roadmap.html.Comment: INFN Roadmap Report: 86 pages, 25 figures, 9 table

Beitraege zur Finanz- und Steuerpolitik 1986/87

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