Effect of monomer composition on proton dissociation of weak polyacids

The study of the proton dissociation process of weak polyacids (eg α carboxylic poly(monoprotic)acid) is based on the knowledge of the change in electrostatic free energy, G(el), as a function of the variation of the number of charges on the polymer chain. The original treatment proposed by Manning can be used to describe the proton dissociation process of weak poly(monoprotic)acids, in the absence of pH-induced conformational transitions. In order to describe the alpha dependence of pKa of weak co-poly(monoprotic)acids containing two different acidic groups in different amounts along the polymer chain, a simple modification of the model is proposed. Abbreviations used: Due to the difficulty of using non-ASCI characters in the main text, we have used the following abbreviations: G(el) Gel 10-pH 10-pH pKa pKa alpha α alphan αn dG(el)/dalpha δGel/δα KA and KB KA and KB CA and CB CA and CB βA and βB βA and βB δpK δpK §max ξmax This revised version was published online in November 2006 with corrections to the Cover Date.     

Altered Orcadian Rhythms of Blood Pressure and Heart Rate in Non-Hemodialysis Chronic Renal Failure

The extended use of ambulatory monitoring has permitted the identification of many conditions in which the circadian rhythm of blood pressure is altered. The common denominator seems to be an impairment of the autonomic nervous system function. We examined whether the circadian blood pressure rhythm is altered in chronic renal failure (where autonomic dysfunction is usually present) by using a standardized chronobiological inferential statistical method in hospitalized subjects. For this purpose, a group of 30 non-hemodialysis hypertensive patients with chronic renal failure was compared with a second group of 30 patients affected by uncomplicated mild-to-moderate essential hypertension. The two groups were matched by age, sex and circadian mesors of blood pressure. Diet, meal times, sleep and activity logs were standardized. Blood pressure and heart rate recordings were obtained by using an automatic oscillometric recorder and subsequently analyzed according to the cosinor method. A mean circadian rhythm of blood pressure was documented in both groups, but while the mean acrophases occurred between 2 and 3 p.m. in essential hypertension, in renal failure they were between 11 p.m. and midnight for blood pressure and around 7 p.m. for heart rate. In addition, the mean circadian amplitudes were significantly lower in renal failure, while the mean circadian mesor of heart rate was significantly higher. Our data demonstrate that the circadian rhythms of blood pressure and heart rate are altered also in hypertension due to chronic renal failure.     

Afghanische Pflanzengesellschaften

Zusammenfassung Es werden die Standortsfaktoren der afghanischen Pflanzengesellschaften geschildert und sodann soziologische Aufnahmen der xerophilen Pflanzengesellschaften gebracht, die in diesem Gebiet, in dem sommerliche Niederschläge mit Ausnahme des äußersten Ostens in der Regel fehlen, die Hauptrolle spielen. Infolge der großen Artenzahl, des Fehlens der biotischen Auslese und infolge wenig differenzierter Standortsverhältnisse kommt es nicht zu typischen Assoziationen mit charakteristischen Artenkombinationen. Es werden allerdings ähnliche Aufnahmen unter Assoziationsnamen zusammengefaßt, wobei aber betont wird, daß sie nich so gut charakterisiert sind wie europäische Assoziationen. Mit dieser Einschränkung werden im untersuchten Teil Afghanistans die Assoziationen unterschieden: Lactucetum orientalis, Veronicetum campylopodae, Festucetum karatavicae, Caricetum stenophyllae, Tamaricetum karakalensis, Arthrophytetum Griffithii, Parietarietum lusitanicae, Callipeltetum cucullaris, Melicetum Cupani, Stipetum Szowitsianae, Cousinietum polyneurae und einige kleinere Assoziationen mit beschränkter Verbreitung. Alle diese Assoziationen können unter dem Namen Poetalia bulbosae zusammengefaßt werden.

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Summary The environmental conditions of the Afghanian plant-communities are described and followed by sociological lists of the xerophytic plant-communities which play a major part in this area where precipitations are absent in summer as a rule with the exception of the extreme East. In consequence to the great number of species, the absence of a biotic selection and to the slightly differentiated environmental conditions no typical associations with characteristic combination of species occur. In spite of this similar groupments are united under the names of associations, but the fact is pointed out that they are less well characterised than are European associations. With this limitation in mind the following associations are acknowledged in the part of Afghanistan under consideration: Lactucetum orientalis, Veronicetum campylopodae, Festucetum karatavicae, Caricetum stenophyllae, Tamaricetum karakalensis, Arthrophytetum Griffithii, Parietarietum lusitanicae, Callipeltetum cucullaris, Melicetum Cupani, Stipetum Szowitsianae, Cousinietum polyneurae and several smaller associations inhabiting a more restricted area. All these associations may be united under the name Poetalia bulbosae.

     

A socio‐ecological model for predicting impacts of land‐use and climate change on regional plant diversity in the Austrian Alps

Climate and land‐use change jointly affect the future of biodiversity. Yet, biodiversity scenarios have so far concentrated on climatic effects because forecasts of land use are rarely available at appropriate spatial and thematic scales. Agent‐based models (ABMs) represent a potentially powerful but little explored tool for establishing thematically and spatially fine‐grained land‐use scenarios. Here, we use an ABM parameterized for 1,329 agents, mostly farmers, in a Central European model region, and simulate the changes to land‐use patterns resulting from their response to three scenarios of changing socio‐economic conditions and three scenarios of climate change until the mid of the century. Subsequently, we use species distribution models to, first, analyse relationships between the realized niches of 832 plant species and climatic gradients or land‐use types, respectively, and, second, to project consequent changes in potential regional ranges of these species as triggered by changes in both the altered land‐use patterns and the changing climate. We find that both drivers determine the realized niches of the studied plants, with land use having a stronger effect than any single climatic variable in the model. Nevertheless, the plants' future distributions appear much more responsive to climate than to land‐use changes because alternative future socio‐economic backgrounds have only modest impact on land‐use decisions in the model region. However, relative effects of climate and land‐use changes on biodiversity may differ drastically in other regions, especially where landscapes are still dominated by natural or semi‐natural habitat. We conclude that agent‐based modelling of land use is able to provide scenarios at scales relevant to individual species distribution and suggest that coupling ABMs with models of species' range change should be intensified to provide more realistic biodiversity forecasts.     

Die Gattungsumgrenzung vonGypsophila undAcanthophyllum

Zusammenfassung In einer Monographie der GattungGypsophila vonBarkoudah wird die Gattungsumgrenzung vonGypsophila undAcanthophyllum geändert, indem die Sektionen Pseudacanthophyllum und Jordania vonGypsophila zuAcanthophyllum gestellt werden. Es werden vorwiegend andere Merkmale als bisher zur Trennung der beiden Gattungen herangezogen. Der Verfasser bezieht hiezu kritisch Stellung.     

pH-Stat titration method for dihydrofolate reductase activity measurements: application to determination of substrate Michaelis constant and antifolate inhibition constant

A pH-Stat titration method was developed for measuring dihydrofolate reductase (DHFR) activity; this method permits detection of very low DHFR activities corresponding to 100 pmol of substrate reduced per minute. This value is about ten times lower than those observed using the classical spectrophotometric method. This sensitivity makes it possible to measure the DHFR in crude tissue extracts. With beef liver DHFR, Michaelis constants for the cofactor NADPH and the natural substrate determined by this method were 1.9 +/- 0.3 X 10(-5) and 8.5 +/- 0.5 X 10(-7) M, respectively. The inhibition constant of methotrexate, a competitive inhibitor of dihydrofolate, was 3.4 +/- 1.3 X 10(-11) M.