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Pots
Kinds of Pots Terms modified by Pots Selected AbstractsBootstrap simulations for evaluating the uncertainty associated with peaks-over-threshold estimates of extreme wind velocityENVIRONMETRICS, Issue 1 2003M. D. Pandey Abstract In the peaks-over-threshold (POT) method of extreme quantile estimation, the selection of a suitable threshold is critical to estimation accuracy. In practical applications, however, the threshold selection is not so obvious due to erratic variation of quantile estimates with minor changes in threshold. To address this issue, the article investigates the variation of quantile uncertainty (bias and variance) as a function of threshold using a semi-parametric bootstrap algorithm. Furthermore, the article compares the performance of L-moment and de Haan methods that are used for fitting the Pareto distribution to peak data. The analysis of simulated and actual U.S. wind speed data illustrates that the L-moment method can lead to almost unbiased quantile estimates for certain thresholds. A threshold corresponding to minimum standard error appears to provide reasonable estimates of wind speed extremes. It is concluded that the quantification of uncertainty associated with a quantile estimate is necessary for selecting a suitable threshold and estimating the design wind speed. For this purpose, semi-parametric bootstrap method has proved to be a simple, practical and effective tool. Copyright © 2003 John Wiley & Sons, Ltd. [source] Synthesis and characterization of novel poly(o -toluidine) montmorillonite nanocomposites: Effect of surfactant on intercalationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2007Rahul Singhal Abstract The investigation of clay based polymer nanocomposites has opened the door for the development of novel, ecofriendly advanced nano materials that can be safely recycled. Because of their nanometer size dispersion, these nanocomposites often have superior physical and mechanical properties. In this study, novel nanocomposites of poly(o -toluidine) (POT) and organically modified montmorillonite (MMT) were synthesized using camphor sulfonic acid (CSA), cetyl pyridinum chloride (CPCl), and N -cetyl- N,N,N -trimethyl ammonium bromide (CTAB) to study the role of surfactant modification on the intercalation. The in situ intercalative polymerization of POT within the organically modified MMT layers was analyzed by FTIR, UV,visible, XRD, SEM as well as TEM studies. The average particle size of the nanocomposites was found to be in the range 80,100 nm. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [source] Peer observation of teaching in the online environment: an action research approachJOURNAL OF COMPUTER ASSISTED LEARNING, Issue 5 2008D. Swinglehurst Abstract This paper describes a collaborative action research approach used to explore peer observation of teaching (POT) within the online environment. Although POT has become familiar in face-to-face teaching contexts, little is understood of its potential role in online settings. We conducted ,virtual' focus groups to explore the experience and views of 28 teachers and subjected our data to a thematic analysis. This informed the implementation of an innovative programme of POT, ,Peer-to-peer Reflection on Pedagogical Practice' (PROPP) among tutors of a Web-based MSc in International Primary Health Care at University College London. Modeled on an action learning set, the programme encourages collaborative reflection on teaching practices, based on participants' specific examples of online teaching. The PROPP model is consistent with Quality Enhancement, which we distinguish from Quality Assurance. Here, we describe the implementation of the PROPP programme within an action research framework and identify the factors that we consider critical to the success of peer observation within online courses. We highlight examples of aspects of teaching that have been discussed within the PROPP programme and offer suggestions of the kinds of evidence that could be incorporated into a portfolio to demonstrate the effectiveness of such an initiative. [source] WORKINGS OF THE MELTING POT: SOCIAL NETWORKS AND THE EVOLUTION OF POPULATION ATTRIBUTES,JOURNAL OF REGIONAL SCIENCE, Issue 2 2007Jan K. Brueckner ABSTRACT This paper links the two nascent economic literatures on social networks and cultural assimilation by investigating the evolution of population attributes in a simple model where agents are influenced by their acquaintances. The main conclusion of the analysis is that attributes converge to a melting-pot equilibrium, where everyone is identical, provided the social network exhibits a sufficient degree of interconnectedness. When the model is extended to allow an expanding acquaintance set, convergence is guaranteed provided a weaker interconnectedness condition is satisfied, and convergence is rapid. If the intensity of interactions with acquaintances becomes endogenous, convergence (when it occurs) is slowed when agents prefer to interact with people like themselves and hastened when interaction with dissimilar agents is preferred. [source] Primary orthostatic tremor is an exaggeration of a physiological response to instabilityMOVEMENT DISORDERS, Issue 2 2003Andrew Sharott BSc Abstract Primary orthostatic tremor (POT) is a rare disorder characterised by an intense sense of unsteadiness upon standing and a 16-Hz tremor in which the timing between tremor bursts in different muscles (unilateral and bilateral) remains constant. Hitherto, similar EMG activity has not been described in healthy subjects and it has been postulated that the oscillations seen in POT are primarily pathological. In this study, EMG was recorded from tibialis anterior in healthy subjects who were made unsteady through vestibular galvanic stimulation or leaning backwards. Under these conditions, a peak at approximately 16 Hz was seen in the coherence between the left and right tibialis anterior. This bilateral coherence was absent when the subjects activated the same muscles when not unsteady. These data indicate the existence of a physiological system involved in organising postural responses under circumstances of imbalance and characterised by a highly synchronised output at approximately 16 Hz. In addition, the results suggest that the core abnormality in POT may be an exaggerated sense of unsteadiness when standing still, which then elicits activity from a 16-Hz oscillator normally engaged in postural responses. © 2002 Movement Disorder Society [source] A comparative study on camphorsulphonic acid modified montmorillonite clay based conducting polymer nanocompositesPOLYMER COMPOSITES, Issue 5 2010Ufana Riaz Nanotechnology has emerged as a subject of immense academic interest and excitement in the past few decades. The immediate goal of this science aims at the production of high performance nanomaterials. The present study reports comparative investigations on the in situ polymerization of polyaniline (PANI), and its derivatives poly(1-naphthylamine) (PNA) and poly(o -toluidine) (POT) within the camphor sulphonic acid (CSA) modified montmorillonite (MMT) layers. The polymerization as well as intercalation of the conducting polymers was confirmed by FT-IR, UV-visible spectroscopies, and XRD studies, whereas the morphology of the nanocomposites was analyzed by TEM studies. It was found that the PANI derivatives (PNA and POT) revealed higher intercalation as compared with PANI. The morphology of nanocomposites was found to be governed by the type of conducting polymer intercalated. A large variation in the morphology as well as particle size was observed between the nanocomposites of PANI and its derivatives. The conductivity was found to be in the range of 10,3,10,2 S·cm,1. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers [source] Nonlinear optical properties of poly-ortho-toluidine films implantated by N+ ions with different energyPOLYMER COMPOSITES, Issue 10 2009Yan Shaolin This article reports experimental work on the effect of N+ ion implantation on third-order nonlinear optical properties of POT films. Using K2Cr2O7 as oxidizing agent, poly- ortho -toluidine (POT) was synthesized in 1 M hydrochloric. The POT films were prepared by spin-coating method and then implantated by N+ ions (15,30 KeV) at a dose 1.9 × 1016 ions/cm2. The films were characterized by FT-IR spectroscopy, visible spectroscopy and SEM, their third-order nonlinear optical susceptibility (,(3)) were also examined by a degenerate four-wave mixing (DFWM) system at 532nm. Compared to pristine POT films, the optical band gap obtained from visible spectra decreased from 3.58 to 3.48 eV when the energy was 30 KeV. Also, The ,(3) value of implantated POT films increased from 3.31 × 10,10 esu to 4.04 × 10,9 esu when the implantated energy was 25 KeV. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source] Comparative studies of solid-state synthesized poly(o -methoxyaniline) and poly (o -toluidine)POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 11 2008Ruxangul Jamal Abstract Poly(o -methoxyaniline) (POMA) and poly(o -toluidine) (POT) salts doped with different acids (methanesulphonic acid (MeSA), trifluoroacetic acid (TFA), and hydrochloric acid (HCl)) were synthesized by using solid-state polymerization method. The polymers were characterized by Fourier transform infrared (FTIR) spectra, ultraviolet,visible (UV,Vis) spectrometry, X-ray diffraction (XRD), cyclic voltammetry (CV), and conductivity measurements. Transmission electron microscopy (TEM) was done to study the morphologies of POMA and POT salts. The FTIR and UV-Vis absorption spectra revealed that the reduced phase was predominant in POMA salts, and the pernigraniline phase was predominant in POT salts. It was found that POMA salts displayed higher doping level and conductivity. In contrast, POT salts were lower at doping levels and conductivity. In accordance with these results, the electrochemical activity was also found to be lower in POT salts. The XRD patterns showed that the POMA salts displayed higher crystallinity than POT salts. The results from TEM revealed that the morphologies of POMA salts were different from those of POT salts. Copyright © 2008 John Wiley & Sons, Ltd. [source] Glucose oxidase electrodes of polyaniline, poly(o -toluidine) and their copolymer as a biosensor: a comparative studyPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 6 2004D. D. Borole Abstract A simple technique is described for constructing a glucose sensor by the entrapment of glucose oxidase (GOD) in a polyaniline (PA), poly(o -toluidine) (POT) and their copolymer poly(aniline-co- o -toluidine) (PA-co-POT) thin films, which were electrochemically deposited on a platinum plate in phosphate and acetate buffer. The maximum current response was observed for PA, POT, and PA-co-POT GOD electrodes at pH 5.5 and potential 0.60,V (v. Ag/AgCl). The phosphate buffer gives fast response as compared to acetate buffer in amperometric measurements. PA GOD electrode shows the fastest response followed by PA-co-POT and POT GOD electrodes. Copyright © 2004 John Wiley & Sons, Ltd. [source] POTS, HOUSES AND METAL: TECHNOLOGICAL RELATIONS AT THE BRONZE AGE TELL AT SZÁZHALOMBATTA, HUNGARYOXFORD JOURNAL OF ARCHAEOLOGY, Issue 2 2006JOANNA SOFAER Summary. At the Bronze Age tell of Százhalombatta, Hungary, techniques used for making pottery echo those used in other media. Pottery and architecture have a close relationship. Not only were both made of clay, but methods of making pots echo those used for building. Similarly, pottery and metalwork share common themes and technologies for working with clay and bronze. Since choices made by potters are not solely confined to the environment, raw materials and tools, but are also socially and culturally defined, by implication the transfer of know-how must be situated within social networks between people. This paper considers how the identification of technical relationships between different media at Százhalombatta can be used to explore social relations in Bronze Age society, thereby suggesting relationships that work on both technical and social levels. [source] POTS AND PITS: DRINKING AND DEPOSITION IN LATE IRON AGE SOUTH-EAST BRITAINOXFORD JOURNAL OF ARCHAEOLOGY, Issue 2 2005MARTIN PITTS Summary. This paper considers the role of pottery in the Late Iron Age to Roman transition in south-east Britain. Traditional concern with the significance of Continental imports is rejected in favour of a more holistic and bottom-up approach giving equal emphasis to locally made forms and imports in complete assemblages. Several stages of inter-site correspondence analysis are conducted on a range of sites and assemblages in the region. Patterning pertaining to the use and deposition of both imported and local pottery vessels can be seen to contradict simplistic models for ,Romanization before conquest'. The main conclusions include evidence for the selective disposal of drinking vessels and table wares in pits, the likely widespread consumption of beer as opposed to wine, and the implied importance of indigenous social practices such as feasting and communal drinking. [source] Treatment of Inappropriate Sinus Tachycardia with Ivabradine in a Patient with Postural Orthostatic Tachycardia Syndrome and a Dual Chamber PacemakerPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 1 2009SITARA KHAN M.R.C.P. We present the case of a 44-year-old woman with postural orthostatic tachycardia syndrome (POTS) and a dual chamber pacemaker. The patient suffered from inappropriate sinus tachycardia that had been resistant to treatment with traditional rate-slowing medications. Ivabradine,the specific sinus node If current inhibitor,was used to successfully lower the heart rate. The patient had no evidence of POTS on repeat autonomic function testing, and there was a corresponding symptomatic benefit. We propose that this class of drugs, the use of which is established as antianginals, should be considered in patients with resistant inappropriate sinus tachycardia. [source] Surgical Management of Jugular Foramen Meningiomas: A Series of 13 Cases and Review of the Literature,THE LARYNGOSCOPE, Issue 10 2007Mario Sanna MD Abstract Objective: Primary meningiomas occurring within the jugular foramen are exceedingly rare lesions presumed to originate from arachnoid-lining cells situated within the jugular foramen. The objective of this study is to analyze the management and outcome in a series of 13 primary jugular foramen meningiomas collected at a single center. Study Design: Retrospective study. Setting: Quaternary referral otology and skull base private center. Methods: Charts belonging to 13 consecutive patients with pathologically confirmed jugular foramen meningioma surgically treated between September 1991 and May 2005 were examined retrospectively. The follow-up of the series ranged from 12 to 120 (mean, 42.8 ± 27.5) months. Results: Four (28.5%) patients underwent single-stage tumor removal through the petro-occipital transigmoid (POTS) approach. In two patients with preoperative unserviceable hearing, a combined POTS-translabyrinthine approach was adopted. Two patients underwent a combined POTS-transotic approach because of massive erosion of the carotid canal. A modified transcochlear approach type D with posterior rerouting of the facial nerve and transection of the sigmoid sinus and jugular bulb was performed in two patients with a huge cerebellopontine angle tumor component with extension to the prepontine cistern together with massive involvement of the petrous bone and middle ear and encasement of the vertical and horizontal segments of the intrapetrous carotid artery. In one patient with evidence of a dominant sinus on the site of the tumor, a subtotal tumor removal via an enlarged translabyrinthine approach (ETLA) was planned to resect the intradural component of the tumor. Two patients in our series underwent a planned staged procedure on account of a huge tumor component in the neck. One of these patients underwent a first-stage infratemporal fossa approach type A to remove the tumor component in the neck; the second-stage intradural removal of the tumor was accomplished via an ETLA. The last patient underwent a first-stage modified transcochlear type D approach to remove the intradural tumor component followed by a second-stage transcervical procedure for removal of the extracranial component. Gross total tumor removal (Simpson grade I,II) was achieved in 11 (84.6%) cases. Subtotal removal of the tumor was accomplished in two patients. Good facial nerve function (grades I and II) was achieved in 46.1% of cases, whereas acceptable function (grade III) was achieved in the remaining cases 1 year after tumor removal. Hearing was preserved at the preoperative level in all four patients who underwent surgery via the POTS approach. After surgery, no patient recovered function of the preoperatively paralyzed lower cranial nerves. A new deficit of one or more of the lower cranial nerves was recorded in 61.5% of cases. Conclusions: Surgical resection is the treatment of choice for jugular foramen meningiomas. Among the various surgical techniques proposed for dealing with these lesions, we prefer the POTS approach alone or combined with the translabyrinthine or transotic approaches. Despite the advances in skull base surgery, new postoperative lower cranial nerve deficits still represent a challenge. [source] Structure and evolution of the horizontal septum in vertebratesJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 5 2003S. Gemballa Abstract Although the horizontal septum (HS) has been identified as playing a role in fish biomechanics and in path finding of cells during zebrafish development, its morphology is poorly known. However, it is generally regarded as an evolutionarily conserved structure. To test this idea, we applied a novel combination of techniques to analyse the HS of 35 species from all major gnathostome clades in which is visualized its collagen fibre architecture. Results show that the HS is a conserved trait only with respect to the presence of caudolateral [= epicentral] and craniolateral [= posterior oblique] collagen fibre tracts, but differs remarkably with respect to the specifications of these tracts. Our data revealed several evolutionary changes within vertebrates. In the gnathostome ancestor, the two tracts are represented by evenly distributed epicentral fibres (ECFs) and posterior oblique fibres (POFs). ECFs are condensed to distinct epicentral tendons (ECTs) in the actinopteran ancestor. POFs independently evolved to distinct posterior oblique tendons (POTs) at least two times within teleosts. Within basal teleostomes, POFs as well as ECFs or ECTs were lost two times independently. POTs were lost at least three times independently within teleosts. This view of a homoplastic HS remains stable regardless of the competing phylogenies used for analysis. Our data make problematic any generalization of biomechanical models on fish swimming that include the HS. They indicate that the pathfinding role of the HS in zebrafish may be extended to gnathostome fishes, but not to agnathans, sarcopterygian fishes and tetrapods. [source] Relative frequency of peripheral odontogenic tumors: a study of 45 new cases and comparison with studies from the literatureJOURNAL OF ORAL PATHOLOGY & MEDICINE, Issue 7 2006Amos Buchner Background:, Peripheral (extraosseous) odontogenic tumors are rare, and reports in the literature have mainly been single case reports or a small series of cases. The aim of this study was to determine the relative frequency of peripheral (extraosseous) odontogenic tumors relative to one another and relative to their central (intraosseous) counterparts in an oral pathology biopsy service and to compare these data with information available in the literature. Methods:, The files of the Pacific Oral and Maxillofacial Pathology Laboratory of the University of the Pacific, San Francisco, CA, USA, served as the source of material for this study. Files were systematically searched for all cases of peripheral odontogenic tumors (POTs) during a 20-year-period. Results:, There were 91 178 cases accessed in which central and POTs were identified in 1133 (1.24%), central tumors in 1088 (1.2%), and peripheral tumors in 45 (0.05%). Peripheral tumors accounted for 4% of all 1133 central and POTs. Peripheral odontogenic fibroma (PODF) was the most common of the 45 POTs accounting for 51.1% (23 cases) followed by peripheral ameloblastoma (PA) 28.9% (13 cases) and peripheral calcifying cystic odontogenic tumor (PCCOT) 13.3% (six cases). Peripheral calcifying epithelial odontogenic tumor, peripheral ameloblastic fibroma, and peripheral ameloblastic carcinoma were also identified , each comprised 2.2% (one case each). PODF was more common than its central counterpart by a 1.4:1 ratio. This was the only peripheral tumor that was more common than its central counterpart. PA accounted for 9.3% of all ameloblastomas and PCCOT for 26% of all calcifying cystic odontogenic tumors. Conclusion:, There is only scarce information in the literature on the relative frequency of POTs. Additional studies should be conducted to determine the true relative frequency. To ensure accuracy, pathologists with experience in the field of odontogenic tumors should conduct these studies. Intraosseous tumors that perforate through the bone to the gingival tissue, clinically presenting as ,peripheral tumors' should be excluded. [source] Expression of human ,-defensins-1 and -2 peptides in unresolved chronic periodontitisJOURNAL OF PERIODONTAL RESEARCH, Issue 4 2004Qian Lu Background:, Human ,-defensins (hBDs) are antimicrobial peptides which contribute to host innate immunity by disrupting the membrane integrity of a broad spectrum of microorganisms. Objectives:, This study aimed to determine the expression profiles of hBD-1 and -2 peptides in gingiva and to assess the possible relations of these antimicrobial peptides with periodontal health and disease. Methods:, Seven periodontally healthy subjects and 22 patients with unresolved chronic periodontitis were recruited and the gingival biopsies collected consisted of healthy tissues from the healthy subjects (HT-C); periodontal pocket tissues (PoT) and inflamed connective tissues (ICT) from the base of pocket, i.e. granulation tissues, as well as clinically healthy tissues (HT-P) from the adjacent clinically healthy sites from the patients. The expression of hBD-1 and -2 peptides was detected by immunohistochemistry and quantitatively analyzed with a computerized image processing system. Results:, Both hBD-1 and -2 peptides were detected in all periodontally healthy subjects, while hBD-1 was detected in all patients and hBD-2 was found in most of the patients. Their expression was mainly confined to the granular and spinous layers of gingival epithelium, in which hBD-1 was detected in both intercellular spaces and cytoplasm, whereas hBD-2 was mainly observed in the cytoplasm. HT-C expressed significantly higher levels of hBD-2 than HT-P (p < 0.05). Within the patients, both defensins were up-regulated significantly in PoT as compared with the adjacent HT-P (p < 0.05). Conclusions:, The present study showed that hBD-1 and -2 were frequently expressed in the granular and spinous layers of gingival epithelia and their expression may be associated with periodontal health and disease. [source] Stereoselective Synthesis of 2-Deoxyglycosides from Sulfanyl Alkenes by Consecutive "One Pot" Cyclization and Glycosylation ReactionsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 15 2007Miguel A. Rodríguez Abstract 2-Deoxy-2-iodopyranosides 3, and 9,12 were synthesized from sulfanyl alkenes using a "one pot" consecutive cyclization,glycosylation process. Compared with the stepwise procedure, the "one pot" process gave significantly improved yields with similar or slightly lower selectivities. The "onepot" procedure was applied to the synthesis of 2,6-dideoxy-2-iodoglycoside 22, which was successfully deiodinated to afford the 2,6-dideoxyglycoside 23. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Tandem Enzyme/Gold-Catalysis: From Racemic ,-Allenic Acetates to Enantiomerically Enriched 2,5-Dihydrofurans in One PotADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 14-15 2009Martta Asikainen Abstract We report the first example of a tandem kinetic resolution/cycloisomerization of racemic allenic acetates in the presence of Burkholderia cepacia lipase (PS Amano SD) and catalytic amounts of chloroauric acid (HAuCl4) which affords 2,5-dihydrofurans, as well as unreacted starting material, in one pot with high enantiomeric excess and moderate to good yield. [source] Added nitrogen interaction as affected by soil nitrogen pool size and fertilization , significance of displacement of fixed ammoniumJOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 2 2004Shan Lin Abstract Displacement of NH4+ fixed in clay minerals by fertilizer 15NH4+ is seen as one mechanism of apparent added nitrogen interactions (ANI), which may cause errors in 15N tracer studies. Pot and incubation experiments were carried out for a study of displacement of fixed NH4+ by 15N-labeled fertilizer (ammonium sulfate and urea). A typical ANI was observed when 15N-labeled urea was applied to wheat grown on soils with different N reserves that resulted from their long-term fertilization history: Plants took up more soil N when receiving fertilizer. Furthermore, an increased uptake of 15N-labeled fertilizer, induced by increasing unlabeled soil nitrogen supply, was found. This ANI-like effect was in the same order of magnitude as the observed ANI. All causes of apparent or real ANI can be excluded as explanation for this effect. Plant N uptake-related processes beyond current concepts of ANI may be responsible. NH4+ fixation of fertilizer 15NH4+ in sterilized or non-sterile, moist soil was immediate and strongly dependent on the rate of fertilizer added. But for the tested range of 20 to 160 mg 15NH4+ -N kg,1, the NH4+ fixation rate was low, accounting for only up to 1.3,% of fertilizer N added. For sterilized soil, no re-mobilization of fixed 15NH4+ was observed, while in non-sterile, biologically active soil, 50,% of the initially fixed 15NH4+ was released up to day 35. Re-mobilization of 15NH4+ from the pool of fixed NH4+ started after complete nitrification of all extractable NH4+. Our results indicate that in most cases, experimental error from apparent ANI caused by displacement of fixed NH4+ in clay is unlikely. In addition to the low percentage of only 1.3,% of applied 15N, present in the pool of fixed NH4+ after 35 days, there were no indications for a real exchange (displacement) of fixed NH4+ by 15N. Einfluss der Düngung und des N-Bodenvorrats auf Added Nitrogen Interactions , Bedeutung des Ersatzaustauschs mit in Tonmineralen fixiertem Ammonium Ersatzaustausch (displacement) von in Tonmineralen fixiertem NH4+ durch Dünger- 15NH4+ gilt als eine Ursache für scheinbare (apparente) Added Nitrogen Interactions (ANI). Diese werden als Fehlerursache in 15N-Tracerstudien diskutiert. Durch Einsatz von 15N-markiertem Ammoniumsulfat und Harnstoff wurde in Inkubations- und Gefäßversuchen geprüft, welche Bedeutung der Ersatzaustausch von gedüngtem 15NH4+ mit in Tonmineralen fixiertem Ammonium hat. Mit zwei Böden, die sich nur in ihrer Düngungsgeschichte unterschieden, zeigte sich nach Düngung mit 15N-markiertem Harnstoff zu Weizen eine typische ANI: Nach Düngung nahmen die Pflanzen nicht nur Dünger-N, sondern auch mehr Boden-N auf. Zusätzlich zeigte sich, dass die Pflanzen bei gleicher Düngung mehr Dünger-N aufnahmen, wenn sie auf Boden mit größerem N-Vorrat wuchsen. Beide Effekte hatten die gleiche Größenordnung. Dieser Befund kann mit den bisher beschriebenen Ursachen für ANI nicht erklärt werden. Wahrscheinlicher scheint eine Beeinflussung der aktiven, pflanzlichen N-Aufnahme. Die Fixierung von Dünger- 15NH4+ in sterilisiertem oder nicht sterilisiertem, frischem Boden erfolgte unmittelbar und hing von der gedüngten N-Menge ab. Innerhalb des untersuchten Bereichs von 20 bis 160 mg 15NH4+ -N kg,1 wurden nur 1,3,% des gedüngten NH4+ in Tonmineralen fixiert. Dieses fixierte NH4+ wurde bei zuvor sterilisiertem Boden nicht wieder freigesetzt. Hingegen wurden aus den Tonmineralen des biologisch aktiven, nicht sterilisierten Bodens innerhalb des 35-tägigen Versuchszeitraums 50,% des fixierten NH4+ wieder freigesetzt. Diese Freisetzung setzte in dem Moment ein, als der Vorrat des leicht verfügbaren, 2 M KCl-extrahierbaren NH4+ durch Nitrifikation vollständig erschöpft war. Unsere Ergebnisse zeigen, dass Versuchsfehler durch Ersatzaustausch mit Tonmineral-fixiertem Ammonium als Ursache für die scheinbare ANI in den meisten Fällen auszuschließen sein dürften. Innerhalb von 35 Tagen traten maximal 1,3,% des gedüngten 15N-markierten Dünger-N in die Fraktion des fixierten Ammoniums über. Hinweise für einen echten Ersatzaustausch des in Tonmineralen fixierten Ammoniums durch Dünger-N konnten nicht gefunden werden. [source] ChemInform Abstract: A "One Pot" Synthesis of 2-Aryl-4H-1-benzopyran-4-ones under Coupled Microwave Phase Transfer Catalysis (PTC) and Ultrasonic Irradiation PTC.CHEMINFORM, Issue 29 2008Vijai N. Pathak Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Microwave-Assisted "Green" Synthesis of 2-Alkyl/Arylbenzothiazoles in One Pot: A Facile Approach to Antitumor Drugs.CHEMINFORM, Issue 12 2007Sukanta Kamila Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Rare-Earth Silylamide-Catalyzed Selective Dimerization of Terminal Alkynes and Subsequent Hydrophosphination in One Pot.CHEMINFORM, Issue 1 2006Kimihiro Komeyama Abstract For Abstract see ChemInform Abstract in Full Text. [source] Lipid biomarker and carbon isotopic signatures for stromatolite-forming, microbial mat communities and Phormidium cultures from Yellowstone National ParkGEOBIOLOGY, Issue 1 2004Linda L. Jahnke ABSTRACT The molecular and isotopic compositions of lipid biomarkers from cultured filamentous cyanobacteria (Phormidium, also known as Leptolyngbya) have been used to investigate the community and trophic structure of photosynthetic mats from alkaline hot springs of the Lower Geyser Basin at Yellowstone National Park. We studied a shallow-water coniform mat from Octopus Spring (OS) and a submerged, tufted mat from Fountain Paint Pots (FPP) and found that 2-methylhopanepolyols and mid-chain branched methylalkanes were diagnostic for cyanobacteria, whereas abundant wax esters were representative of the green non-sulphur bacterial population. The biomarker composition of cultured Phormidium -isolates varied, but was generally representative of the bulk mat composition. The carbon isotopic fractionation for biomass relative to dissolved inorganic carbon (DIC; ,CO2) for cultures grown with 1% CO2 ranged from 21.4 to 26.1 and was attenuated by diffusion limitation associated with filament aggregation (i.e. cell clumping). Isotopic differences between biomass and lipid biomarkers, and between lipid classes, depended on the cyanobacterial strain, but was positively correlated with overall fractionation. Acetogenic lipids (alkanes and fatty acids) were generally more depleted than isoprenoids (phytol and hopanoids). The ,13CTOC for OS and FPP mats were somewhat heavier than for cultures (,16.9 and ,23.6, respectively), which presumably reflects the lower availability of DIC in the natural environment. The isotopic dispersions among cyanobacterial biomarkers, biomass and DIC reflected those established for culture experiments. The 7-methyl- and 7,11-dimethylheptadecanes were from 9 to 11 depleted relative to the bulk organic carbon, whereas 2-methylhopanols derived from the oxidation-reduction of bacteriohopanepolyol were enriched relative to branched alkanes by approximately 5,7. These isotopic relationships survived with depth and indicated that the relatively heavy isotopic composition of the OS mat resulted from diffusion limitation. This study supports the suggestion that culture studies can establish valid isotopic relationships for interpretation of trophic structure in modern and ancient microbial ecosystems. [source] Evaluation of the capacity of three halophytes to desalinize their rhizosphere as grown on saline soils under nonleaching conditionsAFRICAN JOURNAL OF ECOLOGY, Issue 4 2009Mokded Rabhi Abstract In the sabkha of Soliman (N-E Tunisia), soil samples of the upper 20 cm were taken during the driest period of the year (July,August) from inside and outside tufts of two perennial halophytes: Arthrocnemum indicum (Willd.) Moq. and Suaeda fruticosa Forssk., both from family Chenopodiaceae. Samples were analysed for electrical conductivity of the saturation paste extract (ECe) and soluble sodium (Na+) content. Then, tufts were divided into three size categories and their shoot biomass production and Na+ content were determined. Our results showed a considerable contribution of shoot Na+ accumulation to rhizosphere desalination. The capacity of the two native halophytes A. indicum. and S. fruticosa to desalinize saline soils was compared with that of an introduced halophyte, Sesuvium portulacastrum L. (Aizoaceae). Seedlings were grown under greenhouse conditions in pots containing 8 kg of saline soil each. Pots were irrigated with tap water during 170 days without leaching. Our results confirmed the contribution of shoot Na+ accumulation to soil desalination. They showed also that among the three studied species, Sesuvium portulacastrum L. seems to be the most convenient to be used for this purpose in arid and semi-arid regions where precipitation is too low to leach salts from rhizosphere. Résumé Dans la sebkha de Soliman (N-E de la Tunisie), des échantillons de sol ont été prélevés dans les 20 cm supérieurs pendant la période la plus sèche de l'année (juillet-août) à l'intérieur et à l'extérieur des touffes de deux halophytes pérennes, Arthrocnemum indicum (Willd) Moq. et Suaeda fructicosa Forsk., appartenant tous deux à la famille des Chenopodiaceae. L'analyse des échantillons s'est basée sur la conductivitéélectrique de la pâte saturée (ECe) et le contenu en sodium (Na+) soluble. Par ailleurs, les touffes d'halophytes ont été réparties en trois catégories selon leur taille, puis des touffes représentatives de chaque catégorie ont été récoltées pour la détermination de la biomasse et la charge en Na+ de leurs parties aériennes. Nos résultats ont montré que l'accumulation de ces ions au niveau des organes aériens contribue considérablement au dessalement de la rhizosphère. La capacité des deux halophytes locales A. indicum et S. fructicosa de dessaler des sols salins a été comparée à celle d'un halophyte introduite, Sesuvium portulacastrum L. (Aizoaceae). De jeunes plantules ont été cultivées sous serre dans des pots contenant chacun huit kilos de sol salin. Les pots ont été irrigués à l'eau de ville pendant 170 jours sans lessivage. Nos résultats ont confirmé la contribution de l'accumulation de Na+ par les organes photosynthétiques au dessalement du sol. Ils ont montré, également, que, parmi les trois espèces étudiées, S. portulacastrum semble être la plus prometteuse pour un tel programme dans les régions arides et semi-arides où les précipitations sont assez faibles pour lessiver les sels de la rhizosphère. [source] Pots and Plays: Interactions between Tragedy and Greek Vase-Painting of the Fourth Century B.C , By Oliver TaplinRELIGIOUS STUDIES REVIEW, Issue 2 2010Anna Stelow No abstract is available for this article. [source] The relative importance of latitude matching and propagule pressure in the colonization success of an invasive forbECOGRAPHY, Issue 6 2006John L. Maron Factors that influence the early stages of invasion can be critical to invasion success, yet are seldom studied. In particular, broad pre-adaptation to recipient climate may importantly influence early colonization success, yet few studies have explicitly examined this. I performed an experiment to determine how similarity between seed source and transplant site latitude, as a general indicator of pre-adaptation to climate, interacts with propagule pressure (100, 200 and 400 seeds/pot) to influence early colonization success of the widespread North American weed, St. John's wort Hypericum perforatum. Seeds originating from seven native European source populations were sown in pots buried in the ground in a field in western Montana. Seed source populations were either similar or divergent in latitude to the recipient transplant site. Across seed density treatments, the match between seed source and recipient latitude did not affect the proportion of pots colonized or the number of individual colonists per pot. In contrast, propagule pressure had a significant and positive effect on colonization. These results suggest that propagules from many climatically divergent source populations can be viable invaders. [source] Synthesis and Anion-Binding Properties of Novel Redox-Active Calixarene ReceptorsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 25 2008Estelle Métay Abstract A novel synthetic approach towards redox-active calixarene-based receptors is described in which ferrocene fragments were introduced at the lower rim through anion-binding urea or amide connections. These derivatives were prepared in one pot by treating an amine-containing calixarene with ferrocenecarboxylic acid in the presence of diphenylphosphoryl azide and diisopropylethylamine. This method allows a convergent approach to these receptors and is readily adaptable to the introduction of other urea substituents. The anion-binding properties of these artificial receptors have been revealed by NMR spectroscopy and thoroughly investigated by electrochemical methods. We have assessed the importance of the urea,phosphate bonds in the observed electrochemical response by studying receptors in which the ferrocene reporters and binding fragments are closely associated or fully disconnected through a long alkyl chain. The experimental results clearly show the utmost importance of ion-pairing effects in the electrochemical recognition process, which account for most of the transduction signal in organic apolar media. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Glycosylations Directed by the Armed-Disarmed Effect with Acceptors Containing a Single Ester GroupEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 23 2007Thomas H. Schmidt Abstract A selective glycosylation reaction controlled by the armed-disarmed effect is described by the use of phenyl thioglycosides. The donor thioglycoside is fully protected with benzyl ethers while the acceptor thioglycoside contains benzyl ethers at position 2 and 3 and a strongly electron-withdrawing pentafluorobenzoate ester group at position 6. The coupling can be performed with galactose, glucose, mannose, and phthalimide-protected glucosamine to afford the corresponding 1,4-linked disaccharides in good yield. These disaccharides can act as glycosyl donors for an additional coupling reaction in the same pot if another acceptor and more promoter are added. In this way, two consecutiveglycosylations can be achieved to afford trisaccharides in one operation. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Stereoselective Synthesis of 2-Deoxyglycosides from Sulfanyl Alkenes by Consecutive "One Pot" Cyclization and Glycosylation ReactionsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 15 2007Miguel A. Rodríguez Abstract 2-Deoxy-2-iodopyranosides 3, and 9,12 were synthesized from sulfanyl alkenes using a "one pot" consecutive cyclization,glycosylation process. Compared with the stepwise procedure, the "one pot" process gave significantly improved yields with similar or slightly lower selectivities. The "onepot" procedure was applied to the synthesis of 2,6-dideoxy-2-iodoglycoside 22, which was successfully deiodinated to afford the 2,6-dideoxyglycoside 23. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Genome analysis of microorganisms living in amoebae reveals a melting pot of evolutionFEMS MICROBIOLOGY REVIEWS, Issue 3 2010Claire Moliner Abstract Amoebae-resistant microorganisms exhibit a specific lifestyle. Unlike allopatric specialized intracellular pathogens, they have not specialized because they infect the amoebae via amoebal attack and present a sympatric lifestyle with species from different phyla. In this review, we compare the genomes from bacteria (Legionella pneumophila, Legionella drancourtii, Candidatus,Protochlamydia amoebophila,'Rickettsia bellii, Candidatus,Amoebophilus asiaticus') and a virus (mimivirus) that multiply naturally in amoebae. The objective is to highlight the genomic traits characterizing these microorganisms and their niche by comparison with other specialized pathogens. The genome of intra-amoebal microorganisms is significantly larger than that of their relatives, contradicting the genome reduction theory mostly accepted for intracellular pathogens. This is probably due to the fact that they are not specialized and therefore maintain their genome size. Moreover, the presence of many horizontally transferred genes and mobilomes in their genomes suggests that these microorganisms acquired genetic material from their neighbors and amoebal host, thus increasing their genome size. Important features involved in gene transfer and pathogenicity were thus acquired. These characteristics suggest that amoebae constitute a gene melting pot, allowing diverse microorganisms to evolve by the same pathway characterized by gene acquisition, and then either adapt to the intra-amoebal lifestyle or create new pathogens. [source] | ||||||||||||||||||||||||||||||||||||||||||||||