Integer point sets minimizing average pairwise L1 distance: What is the optimal shape of a town?
Erik D. Demaine
Sándor P. Fekete
- An n-town, n[is an element of]N , is a group of n buildings, each occupying a distinct position on a 2-dimensional integer grid. If we measure the distance between two buildings along the axis-parallel street grid, then an n-town has optimal shape if the sum of all pairwise Manhattan distances is minimized. This problem has been studied for cities, i.e., the limiting case of very large n. For cities, it is known that the optimal shape can be described by a differential equation, for which no closed-form solution is known. We show that optimal n-towns can be computed in O(n[superscript 7.5]) time. This is also practically useful, as it allows us to compute optimal solutions up to n=80.
YIVO news = Jedīʿōt fun JIWO : No. 206 Spring 2010
High functional diversity is related to high nitrogen availability in a deciduous forest - evidence from a functional trait approach
Valério de Patta Pillar
- The current study tested the assumption that floristic and functional diversity patterns are negatively related to soil nitrogen content. We analyzed 20 plots with soil N-contents ranging from 0.63% to 1.06% in a deciduous forest near Munich (Germany). To describe species adaptation strategies to different nitrogen availabilities, we used a plant functional type (PFT) approach. Each identified PFT represents one realized adaptation strategy to the current environment. These were correlated, next to plant species richness and evenness, to soil nitrogen contents. We found that N-efficient species were typical for low soil nitrogen contents, while N-requiring species occur at high N-contents. In contrast to our initial hypotheses, floristic and functional diversity measures (number of PFTs) were positively related to nitrogen content in the soil. Every functional group has its own adaptation to the prevailing environmental conditions; in consequence, these functional groups can co-exist but do not out-compete one another. The increased number of functional groups at high N-contents leads to increased species richness. Hence, for explaining diversity patterns we need to consider species groups representing different adaptations to the current environmental conditions. Such co-existing ecological strategies may even overcome the importance of competition in their effect on biodiversity.
RAF kinase activity regulates neuroepithelial cell proliferation and neuronal progenitor cell differentiation during early inner ear development
Maria Rodriguez Aburto
Ulf Rüdiger Rapp
- Background: Early inner ear development requires the strict regulation of cell proliferation, survival, migration and differentiation, coordinated by the concerted action of extrinsic and intrinsic factors. Deregulation of these processes is associated with embryonic malformations and deafness. We have shown that insulin-like growth factor I (IGF-I) plays a key role in embryonic and postnatal otic development by triggering the activation of intracellular lipid and protein kinases. RAF kinases are serine/threonine kinases that regulate the highly conserved RAS-RAF-MEK-ERK signaling cascade involved in transducing the signals from extracellular growth factors to the nucleus. However, the regulation of RAF kinase activity by growth factors during development is complex and still not fully understood.
Methodology/Principal Findings: By using a combination of qRT-PCR, Western blotting, immunohistochemistry and in situ hybridization, we show that C-RAF and B-RAF are expressed during the early development of the chicken inner ear in specific spatiotemporal patterns. Moreover, later in development B-RAF expression is associated to hair cells in the sensory patches. Experiments in ex vivo cultures of otic vesicle explants demonstrate that the influence of IGF-I on proliferation but not survival depends on RAF kinase activating the MEK-ERK phosphorylation cascade. With the specific RAF inhibitor Sorafenib, we show that blocking RAF activity in organotypic cultures increases apoptosis and diminishes the rate of cell proliferation in the otic epithelia, as well as severely impairing neurogenesis of the acoustic-vestibular ganglion (AVG) and neuron maturation.
Conclusions/Significance: We conclude that RAF kinase activity is essential to establish the balance between cell proliferation and death in neuroepithelial otic precursors, and for otic neuron differentiation and axonal growth at the AVG.
Transfer entropy - a model-free measure of effective connectivity for the neurosciences
- Understanding causal relationships, or effective connectivity, between parts of the brain is of utmost importance because a large part of the brain’s activity is thought to be internally generated and, hence, quantifying stimulus response relationships alone does not fully describe brain dynamics. Past efforts to determine effective connectivity mostly relied on model based approaches such as Granger causality or dynamic causal modeling. Transfer entropy (TE) is an alternative measure of effective connectivity based on information theory. TE does not require a model of the interaction and is inherently non-linear. We investigated the applicability of TE as a metric in a test for effective connectivity to electrophysiological data based on simulations and magnetoencephalography (MEG) recordings in a simple motor task. In particular, we demonstrate that TE improved the detectability of effective connectivity for non-linear interactions, and for sensor level MEG signals where linear methods are hampered by signal-cross-talk due to volume conduction.
Prevalence of dosing errors in elderly patients with impaired renal function: a survey in ambulatory patients
- Meeting Abstract : Gesellschaft für Arzneimittelanwendungsforschung und Arzneimittelepidemiologie e.V. (GAA). 17. Jahrestagung der Gesellschaft für Arzneimittelanwendungsforschung und Arzneimittelepidemiologie. Osnabrück, 25.-26.11.2010.
ntroduction: Several drugs require dose adjustment in patients with impaired renal function, which however, often goes undetected. Serum creatinine may be normal in patients while renal function is already reduced. The estimated GFR (eGFR) allows a more precise evaluation of the renal function. This study was carried out in a group practice for family medicine, in Frankfurt/ Main, Germany. The exploration aimed at investigating if patients with renal insufficiency were recognised and if their prescriptions were appropriate in terms of dose adjustment or contra-indications.
Methods: In patients (>65yrs) with renal insufficiency (creatinine clearance <60 ml/min), their prescribed medication was retrospectively explored (Observation period 1.1.2008 to 1.4.2009). The Cockroft-Gault formula was used as estimate for the eGFR, using a creatinine value from the patient’s charts. In 90 patients, a second eGFR could be estimated from a second creatinine value obtained within 3-6 months. The recommended dose of each prescription in the SmPC (Fachinformation“) was compared to the dose that had been actually prescribed.
Results: Out of 232 consecutively patients >65 yrs, 102 had an eGFR <60 ml/min, 16 of these had an eGFR <30 ml/min. The eGFR was closely correlated (r2=0.81) with an independent second eGFR. Out of these 102 patients, 48 had a serum creatinine level within the normal range. Renal adjustment was required in 263 of a total of 613 prescriptions. 72 prescriptions in a total of 45 patients were not appropriately adjusted (32) or prescribed despite a contraindication (40). For chronic prescriptions, metformin, ramipril, enalapril, HCTZ, and spironolactone accounted for 70% of inappropriate dosing; the magnitude of misdosing was 1.5 to 4 fold (median 2). 9 temporary prescriptions (of a total of 60 prescriptions) in 8 patients were not adjusted (cefuroxim, cefpodoxim, levofloxacin). We could not prove that patients with normal serum creatinine had a higher rate of inappropriate dosing than those with already elevated creatinine.
Discussion and conclusion: In this GP practice, we have demonstrated a considerable prevalence of inappropriate dosing in patients with impaired renal function. It remains to be elucidated whether surveillance of appropriate dosing in renal impairment can be optimized e.g. with CPOE.
Recent ecological observations on growth rates and seed production in Isopogon prostratus (Proteaceae), a little-known prostrate shrub from south-eastern NSW and Victoria
Lotte von Richter
- Observations on the longevity and ecology of Isopogon prostratus McGill. (Proteaceae) based on 1985 and 2009 field measures on Newnes Plateau, near Lithgow, and a seed germination trial are provided. Its survival strategy appears to be that of a stress-tolerator with long-term persistence at (relatively few) suitable sites, and it remains a relatively rare plant. It is conjectured that it is likely to have been a species of greater abundance in the drier, colder and generally treeless conditions of the Newnes Plateau 15–20 000 years ago, but, as conditions became warmer and wetter it has become reduced to isolated populations as taller shrubs outcompeted it for light.
Whipcord plants: a comparison of south-eastern Australia with New Zealand
Robert F. Parsons
- Whipcord plant is a term used for some dicot angiosperms with small, scale-like leaves closely appressed to the stem. So far, the term has mostly been used in this sense for plants from New Zealand. Here, I summarize the incidence and habitat relations of New Zealand whipcord plants and then use the literature to show that whipcord plants also occur in south-eastern Australia. New Zealand whipcord plants comprise nine species of Hebe, four of Leonohebe and six of Helichrysum, while in south-eastern Australia there are six species of Ozothamnus and one of Leucophyta. In both areas, some species are alpine to subalpine, while some are from lowland habitats with significant summer water deficits.
Native vegetation of southeast NSW: a revised classification and map for the coast and eastern tablelands
M. G. Tozer
D. A. Keith
- Native vegetation of the NSW south coast, escarpment and southeast tablelands was classified into 191 floristic assemblages at a level of detail appropriate for the discrimination of Threatened Ecological Communities and other vegetation units referred to in government legislation. Assemblages were derived by a numerical analysis of 10832 field sample quadrats including 8523 compiled from 63 previous vegetation surveys. Past bias in the distribution of field data towards land under public tenure was corrected by extensive surveys carried out on private land. The classification revises and integrates the units described in recent vegetation studies of Eden, Cumberland Plain and Sydney-south coast into a single, consistent classification. Relationships between floristic assemblages and climate, terrain, substrate and vegetation structure were used to map the distribution of communities prior to clearing at 1:100 000 scale. The extent of clearing was mapped using interpretations of remote imagery (1991–2001) from previous work, standardised and merged into a single coverage and supplemented with additional work. Profiles for each assemblage, which we term ‘communities’ or ‘map units’, describe their species composition, vegetation structure, environmental habitat, the extent of clearing and conservation status. Lists of diagnostic species were defined using a statistical fidelity measure and a procedure for using these for community identification is described. Approximately 66% of the study area retains a cover of native vegetation, primarily in areas with low fertility soils and dissected topography. Communities subject to over-clearing (>70%) are concentrated in a few large areas characterised by clay/loam soils and flat to undulating terrain. These include the Sydney metropolis, Wingecarribee Plateau, Illawarra Plain, Shoalhaven floodplain, Araluen Valley and Bega Valley, and various smaller river valleys. Forty-one percent of remaining native vegetation is protected within conservation reserves while 31% occurs on private land, 20% in State Forests and 8% on other Crown lands. Forty-five Threatened Ecological Communities (TECs) were recorded in the study area. The majority of TECs are represented by a single map unit, although in some cases a TEC is included within a broader map unit. Twelve TECs are represented by combinations of two or more map units.
Coastal Sandplain Vegetation at Brisbane Water and Broken Bay – reconstructing the past to plan for the future
- The vegetation and floristics of the coastal sandplains on the Umina-Woy Woy Peninsula on the northern foreshores of Broken Bay (lat 33° 30’ S, long 151° 15’ E), 40 km north of Sydney, are described from historical records, sampling of remnants and analysis of regional scale vegetation. Of the seven vegetation communities described, Umina Coastal Sandplain Woodland (UCSW) was originally the most extensive type of vegetation over the Umina-Woy Woy sandplain and on the seaward side of the Pearl Beach sandplain, and possibly on the sandplains at Patonga and Little Patonga. Characteristic tree species are Angophora floribunda and Eucalyptus botryoides; the latter appears to be more common at foreshore sites. Close to the sea and in swales at the base of hillslopes, littoral rainforest elements can be present. Patonga may have had significant inclusions of this vegetation. As a result of clearing for suburban development and its reduction to small remnants, UCSW and Freshwater Wetlands have been listed as an Endangered Ecological Communities under the NSW Threatened Species Conservation Act. A form of the closely-related Sydney Red Gum (SRG) complex occurs on a different SLU on the south-west side of Pearl Beach. A characteristic tree is Angophora costata. Site environmental differences between UCSW and the Sydney Red Gum Complex include their occurrence on iron podsols and humus podsols respectively. Regional vegetation classification and analysis shows that these vegetation units are distinctly different from each other. This is supported by historical evidence from surveyor notation on Crown Survey and land subdivision plans. Originally the Bangalay – Rough-barked Apple Woodland vegetation component of the Umina Woy Woy sandplain was defined by the NSW Scientific Committee for Umina Coastal Sandplain Woodland. Regional analysis now reveals the Red Gum-Red Bloodwood (RGBW) component now merges with this former community. The Pearl Beach vegetation remains separate. A re-definition of UCSW is now required. Management, particularly of UCSW, currently involves revegetation and regeneration works in the vicinity of existing reserves. However, because the depletion has been so extensive there is further opportunity to decrease the loss by utilising the wide riparian reserves and laneways where mature trees still exist. A major conservation concern is the modification and loss of the sandplain vegetation, particularly the wetlands. The historical Crown Survey plans highlight the extent of wetlands as an important ecological feature of the original sandplain landscape. The current study estimated that 83% of wetlands and 79% of riparian vegetation has been lost on the Umina-Woy Woy sandplain since European settlement.