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Search Results: 1 - 10 of 470312 matches for " A. Stüken "
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When Naked Became Armored: An Eight-Gene Phylogeny Reveals Monophyletic Origin of Theca in Dinoflagellates
Russell J. S. Orr, Shauna A. Murray, Anke Stüken, Lesley Rhodes, Kjetill S. Jakobsen
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0050004
Abstract: The dinoflagellates are a diverse lineage of microbial eukaryotes. Dinoflagellate monophyly and their position within the group Alveolata are well established. However, phylogenetic relationships between dinoflagellate orders remain unresolved. To date, only a limited number of dinoflagellate studies have used a broad taxon sample with more than two concatenated markers. This lack of resolution makes it difficult to determine the evolution of major phenotypic characters such as morphological features or toxin production e.g. saxitoxin. Here we present an improved dinoflagellate phylogeny, based on eight genes, with the broadest taxon sampling to date. Fifty-five sequences for eight phylogenetic markers from nuclear and mitochondrial regions were amplified from 13 species, four orders, and concatenated phylogenetic inferences were conducted with orthologous sequences. Phylogenetic resolution is increased with addition of support for the deepest branches, though can be improved yet further. We show for the first time that the characteristic dinoflagellate thecal plates, cellulosic material that is present within the sub-cuticular alveoli, appears to have had a single origin. In addition, the monophyly of most dinoflagellate orders is confirmed: the Dinophysiales, the Gonyaulacales, the Prorocentrales, the Suessiales, and the Syndiniales. Our improved phylogeny, along with results of PCR to detect the sxtA gene in various lineages, allows us to suggest that this gene was probably acquired separately in Gymnodinium and the common ancestor of Alexandrium and Pyrodinium and subsequently lost in some descendent species of Alexandrium.
Evolution and Distribution of Saxitoxin Biosynthesis in Dinoflagellates
Russell J. S. Orr,Anke Stüken,Shauna A. Murray,Kjetill S. Jakobsen
Marine Drugs , 2013, DOI: 10.3390/md11082814
Abstract: Numerous species of marine dinoflagellates synthesize the potent environmental neurotoxic alkaloid, saxitoxin, the agent of the human illness, paralytic shellfish poisoning. In addition, certain freshwater species of cyanobacteria also synthesize the same toxic compound, with the biosynthetic pathway and genes responsible being recently reported. Three theories have been postulated to explain the origin of saxitoxin in dinoflagellates: The production of saxitoxin by co-cultured bacteria rather than the dinoflagellates themselves, convergent evolution within both dinoflagellates and bacteria and horizontal gene transfer between dinoflagellates and bacteria. The discovery of cyanobacterial saxitoxin homologs in dinoflagellates has enabled us for the first time to evaluate these theories. Here, we review the distribution of saxitoxin within the dinoflagellates and our knowledge of its genetic basis to determine the likely evolutionary origins of this potent neurotoxin.
The Effect of Weight Loss on Pediatric Nonalcoholic Fatty Liver Disease
David E. St-Jules,Corilee A. Watters,Ken Nagamori,Jeremy King
ISRN Gastroenterology , 2013, DOI: 10.1155/2013/398297
Abstract: This study evaluated the effect of weight loss on pediatric nonalcoholic fatty liver disease (NAFLD). Subjects included 81 overweight NAFLD patients referred to two pediatric gastroenterologists from 2000 to 2010. Data on subjects were obtained from review of medical charts. The effect of weight loss was assessed at 1–4?months, 5–8?months, 9–12?months, and beyond one year as the change in weight, BMI -score (for age-and-sex), and alanine aminotransferase and the relationship between the change in body weight and BMI -score, and the change in alanine aminotransferase. Subjects were mostly obese (99%), male (86%), and Asian (63%) and had median age of 14.1 (11.2–16.2)?years and alanine aminotransferase of 105 (78–153) U/L at referral. Alanine aminotransferase decreased 32?±?66 ( ), 30?±?65 ( ), 37?±?75 ( ), and 45?±?69 ( ) for subjects with follow-up data at 1–4?months ( ), 5–8?months ( ), 9–12 months ( ), and beyond one year ( ), respectively. During these time periods, neither was body weight (?0.2 to +7.1?kg) or BMI -score (?0.12 to ?0.05) significantly reduced, nor were changes in these variables associated with the change in alanine aminotransferase. These findings suggest that weight and BMI -score may not be sufficient indicators of treatment response in pediatric NAFLD patients. 1. Introduction Nonalcoholic fatty liver disease (NAFLD) is a common complication of pediatric obesity characterized by the inappropriate accumulation of fat in hepatocytes in the absence of other known causes of steatosis [1–3]. Hepatic steatosis is closely related to metabolic syndrome and may contribute to the pathogenesis of other obesity-related conditions [4–7]. Prior investigation of children diagnosed with metabolic syndrome in Hawai’i found that approximately two-thirds had elevated serum alanine aminotransferase (ALT) values suggestive of NAFLD [8]. The majority of children with NAFLD suffer from psychological, physical, and pain-related symptoms, which contribute to a lower physical and psychosocial health, and reduced quality of life [9]. When compared to obese controls, pediatric NAFLD patients were found to have greater depression and influence of body weight on self-esteem [10]. Moreover, hepatic steatosis may be accompanied by inflammation and/or fibrosis, which can progress to liver cirrhosis requiring transplantation [1, 11–13]. Along with this, children with NAFLD were found to have reduced age- and sex-standardized survival free of liver transplantation [13]. Similar to other obesity-related conditions, weight loss is the primary treatment strategy for
Discovery of Nuclear-Encoded Genes for the Neurotoxin Saxitoxin in Dinoflagellates
Anke Stüken,Russell J. S. Orr,Ralf Kellmann,Shauna A. Murray,Brett A. Neilan,Kjetill S. Jakobsen
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0020096
Abstract: Saxitoxin is a potent neurotoxin that occurs in aquatic environments worldwide. Ingestion of vector species can lead to paralytic shellfish poisoning, a severe human illness that may lead to paralysis and death. In freshwaters, the toxin is produced by prokaryotic cyanobacteria; in marine waters, it is associated with eukaryotic dinoflagellates. However, several studies suggest that saxitoxin is not produced by dinoflagellates themselves, but by co-cultured bacteria. Here, we show that genes required for saxitoxin synthesis are encoded in the nuclear genomes of dinoflagellates. We sequenced >1.2×106 mRNA transcripts from the two saxitoxin-producing dinoflagellate strains Alexandrium fundyense CCMP1719 and A. minutum CCMP113 using high-throughput sequencing technology. In addition, we used in silico transcriptome analyses, RACE, qPCR and conventional PCR coupled with Sanger sequencing. These approaches successfully identified genes required for saxitoxin-synthesis in the two transcriptomes. We focused on sxtA, the unique starting gene of saxitoxin synthesis, and show that the dinoflagellate transcripts of sxtA have the same domain structure as the cyanobacterial sxtA genes. But, in contrast to the bacterial homologs, the dinoflagellate transcripts are monocistronic, have a higher GC content, occur in multiple copies, contain typical dinoflagellate spliced-leader sequences and eukaryotic polyA-tails. Further, we investigated 28 saxitoxin-producing and non-producing dinoflagellate strains from six different genera for the presence of genomic sxtA homologs. Our results show very good agreement between the presence of sxtA and saxitoxin-synthesis, except in three strains of A. tamarense, for which we amplified sxtA, but did not detect the toxin. Our work opens for possibilities to develop molecular tools to detect saxitoxin-producing dinoflagellates in the environment.
The Trigger and Timing System of the Double Chooz Experiment
F. Beissel,A. Cabrera,A. Cucuanes,J. V. Dawson,D. Kryn,C. Kuhnt,S. Lucht,B. Reinhold,M. Rosenthal,S. Roth,A. Stahl,A. Stüken,C. Wiebusch
Physics , 2012, DOI: 10.1088/1748-0221/8/01/T01003
Abstract: Modern precision neutrino experiments like Double Chooz require a highly efficient trigger system in order to reduce systematic uncertainties. The trigger and timing system of the Double Chooz experiment was designed according to this goal. The Double Chooz trigger system is driven by the basic idea of triggering on multiple thresholds according to the total visible energy and additionally triggering on the number of active photomultiplier tubes (PMTs) in the detector. To do so, the trigger system continuously monitors the analogue signals from all PMTs in the detector. The amplitudes of these PMT-signals are summed for groups of certain PMTs (group signals) and for all PMTs (sum signal), respectively. The group signals are discriminated by two thresholds for each input channel and four thresholds for the sum signal. The resulting signals are processed by the trigger logic unit which is implemented in a FPGA. In addition to the proper trigger, the trigger system provides a common clock signal for all subsequent data acquisition systems to guarantee a synchronous readout of the Double Chooz detectors. The present design of the system provides a high flexibility for the applied logic and settings, making it useful for experiments other than Double Chooz. The Double Chooz trigger and timing system was installed and commissioned in 2011. This article describes the hardware of the trigger and timing system. Furthermore the setup, implemented trigger logic and performance of the trigger and timing system for the Double Chooz experiment is presented.
Qualification Tests of 474 Photomultiplier Tubes for the Inner Detector of the Double Chooz Experiment
C. Bauer,E. Borger,R. Hofacker,K. J?nner,F. Kaether,C. Langbrandtner,M. Lindner,S. Lucht,M. Reissfelder,S. Sch?nert,A. Stüken,C. Wiebusch
Physics , 2011, DOI: 10.1088/1748-0221/6/06/P06008
Abstract: The hemispherical 10" photomultiplier tube (PMT) R7081 from Hamamatsu Photonics K.K. (HPK) is used in various experiments in particle and astroparticle physics. We describe the test and calibration of 474 PMTs for the reactor antineutrino experiment Double Chooz. The unique test setup at Max-Planck-Institut f\"ur Kernphysik Heidelberg (MPIK) allows one to calibrate 30 PMTs simultaneously and to characterize the single photo electron response, transit time spread, linear behaviour and saturation effects, photon detection efficiency and high voltage calibration.
Detailed Analysis of Micro-Grid Stability during Islanding Mode under Different Load Conditions  [PDF]
Rashad M. Kamel, A. Chaouachi, Ken Nagasaka
Engineering (ENG) , 2011, DOI: 10.4236/eng.2011.35059
Abstract: Today, several types of DGs are connected together and formed a small power system called micro-grid (MG). MG is connected to the primary distribution network and usually operates in normal connecting mode. When a severe fault occurs in the primary distribution network, then the MG will transfer to islanding mode. In this paper a complete model is developed to simulate the dynamic performance of the MG during and subsequent to islanding process. The model contains of a solid oxide fuel cell (SOFC), a single shaft micro turbine, a flywheel, two photovoltaic panels and a wind generator system. All these micro sources are con-nected to the MG through inverters except the wind generation system. The inverters are modeled with two control strategies. The first strategy is PQ control which the inverter will inject a certain active and reactive powers. This type of inverter is used to interface micro turbine, fuel cell and photovoltaic panels to the MG. The second strategy is Vf control. This model is used to interface flywheel will act as the reference bus (slack bus) for the MG when islanding occurs. Two cases are studied: the first case discusses the effect of islanding process on frequency, voltage and active power of all micro sources when the MG imports active and reactive power from the primary distribution network. The second studied case, also, shows the effect of islanding on the previous quantities particularly when the MG exports active and reactive power to the pri-mary distribution network. Results showed that the existence of storage device (flywheel) with appropriate control of its inverter can keep the frequency of the MG and the voltages of all buses within their limited levels. The developed model is built in Matlab® Simulink® environment.
The Association of Gene Polymorphisms of the Angiotensin- Converting Enzyme and Angiotensin II Receptor Type 1 with Ischemic Stroke in Turkish Subjects of Trakya Region
Tammam S?PAH?,Babürhan GüLD?KEN,Sibel GüLD?KEN,Sedat üSTüNDA?
Trakya Universitesi Tip Fakultesi Dergisi , 2009,
Abstract: Objectives: The aim of this study was to investigate the frequency of ACE insertion/deletion (I/D) and AT1R (A1166C) gene polymorphisms in ischemic stroke patients in Trakya region and the relation between these gene polymorphisms and stroke subtypes and vascular risk factors.Patients and Methods: The study involved 162 patients with ischemic stroke and 146 control subjects. Ischemic stroke patients were divided into large and small vessel disease subgroups according to ORG 10172 in Acute Stroke Treatment TOAST criteria. The ACE I/D polymorphism was investigated using polymerase chain reaction (PCR), and the AT1R (A1166C) polymorphism was identified using PCR and restriction fragment length polymorphism (RFLP) assay.Results: The ACE I/D genotype distribution in patients (DD=34.0%, ID=50.0%, II=16.0%) did not differ from those in controls (DD=34.3%, ID=49.7%, II=16.1%). The AT1R A1166C genotype distribution in patients (AA=58.0%, CA=34.6%, CC=7.4%) did not significantly differ from those in controls (AA=60.1%, CA=35.7%, CC=4.2%). There was also no difference among the stroke subgroups regarding the distribution of ACE I/D and AT1R (A1166C) polymorphisms.Conclusion: Our results show that ACE I/D and AT1R (A1166C) gene polymorphisms were not genetic risk factors for ischemic stroke in subjects in Trakya region.
The Apollonian metric: limits of the comparison and bilipschitz properties
Peter A. H st
Abstract and Applied Analysis , 2003, DOI: 10.1155/s1085337503309042
Abstract: The Apollonian metric is a generalization of the hyperbolic metric. It is defined in arbitrary domains in ℝn. In this paper, we derive optimal comparison results between this metric and the jG metric in a large class of domains. These results allow us to prove that Euclidean bilipschitz mappings have small Apollonian bilipschitz constants in a domain G if and only if G is a ball or half-space.
Informed Consent and a Sample Study
a?atay üSTüN
Türkiye Fiziksel Tip ve Rehabilitasyon Dergisi , 2008,
Abstract: Informed consent is a patient's right to be presented with sufficient information, by either the physician or their representative, to allow the patient to make an informed decision regarding whether or not to consent to a treatment or procedure. In this letter, we’ll give a sample study from Ege University Hospital, Hospital Ethics Committee. Turk J Phys Med Rehab 2008;54:39-40.
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