Characterizing the Conductivity and Enhancing the Piezoresistivity of Carbon Nanotube-Polymeric Thin Films.

The concept of lightweight design is widely employed for designing and constructing aerospace structures that can sustain extreme loads while also being fuel-efficient. Popular lightweight materials such as aluminum alloy and fiber-reinforced polymers (FRPs) possess outstanding mechanical properties, but their structural integrity requires constant assessment to ensure structural safety. Next-generation structural health monitoring systems for aerospace structures should be lightweight and integrated with the structure itself. In this study, a multi-walled carbon nanotube (MWCNT)-based polymer paint was developed to detect distributed damage in lightweight structures. The thin film's electromechanical properties were characterized via cyclic loading tests. Moreover, the thin film's bulk conductivity was characterized by finite element modeling

Phytoplankton productivity in newly dug fish ponds within Lake Victoria wetlands (Uganda)

The declining Lake Victoria fisheries resource led to a growing recognition of aquaculture as a source of livelihood to riparian communities. Finger ponds speculated to naturally stock fish during flooding and retain them during dry seasons were introduced within the lake’s wetlands. In order to develop a better understanding of these ponds’ dynamics, algal primary productivity was studied in eight newly dug wetland fishponds (8 x 24 m) located in two villages along the northern shores of Lake Victoria (Uganda) before stocking them with fish. Gross primary productivity was low for both sites ranging between 0.00 and 2.63 mg O2 L-1 h-1. The net areal primary productivity of Gaba ponds ranged from -0.34 to 4.66 mg O2 m-2 d-1 while that of Walukuba ponds ranged from 1.16 to 6.25 mg O2 m-2 d-1. Chlorophyll a mean values were 23.46 ± 12.50 ìg L-1 and 75.56 ± 44.35 ìg L-1 and mean turbidity ranges were 132.1 –242.25 and 432.54 - 158.49 NTU for Gaba and Walukuba ponds respectively. Reduced light supply due to the high inorganic turbidity may have been the main limitation for photoautotrophic primary productivity and ponds potential fish yield of 10 - 24 kg ha-1 fish per year

Polyploidy and aneuploidy phenomenon by conjugates - a study focused on genus Spirogyra

Knowledge of nuclear cytology in algae remains to be much improved, compared to that in higher plants and animals. Especially, The Euglenophyceae, the Cryptophyceae, the Dinophyceae and the Zygnematophyceae contain many species with ectremely high chromosome numbers of over one hundred (Sarma 1982). Since Strasburger’s (1875) first report for the process of cell division in Spirogyra orthospira, studies on the nuclear cytology (Godward 1954, 1961; Godward and Newnham 1965) and the cytototaxonomy of Spirogyra were carried out (Tatuno and Iiyama 1971, Vedajanani and Sarma, 1978, Abhayavardhani and Sarma, 1983). However, chromosome numbers of this genus were determined for only forty-four identified species (Chaudhary and Agrawal 1996, Kim et al. 2009). Chromosome numbers in Spirogyra ranged from n = 2 in three Japanese species (Tatuno and Iiyama, 1971) to n = 94 in S. nitida (Abhayavardhani and Sarma, 1983). Polyploidization (endomitosis) is a major evolutionary process in plants where hybridization and chromosome doubling induce enormous genomic stress and can generate genetic and epigenetic modifications (Stebbins, 1971), in which it promotes rapid speciation (Levin, 1983). In contrast, ploidal changes in algae have been studied, i.e. Nichols (1980) reported that polyploidization is known in most major algal taxa, especially in the green algae (chlorophyta). In this study was used culture collections from various habitats. These cultures provided ecological preferences of single taxa and ploidal variants. Cell morphology was obtained from both field material and cultures. In this context, the traditional characters was compared with cellular DNA-contents and chromosome numbers. We supposed that additional species complexes will be delimited and that polyploidy is widespread among Spirogyra. Special attention was paid to the different karyological methods

First limnological records of highly threatened tropical high-mountain crater lakes in Ethiopia

Lakes Dendi, Wonchi and Ziqualla are among the few remnants of undisturbed crater lakes in the central highlands of Ethiopia, and have never been investigated reliably owing to seclusion and inaccessibility. As the lakes offer a pristine environment in a beautiful landscape and are located in the vicinity of the capital city Addis Ababa, they are highly threatened by unsustainable tourism, shoreline and crater rim modifications, water abstraction and land grabbing. We provide a first limnological description to establish baseline data against which future environmental and biological changes can be monitored. The lakes are located above 2,800 m elevation with no surface outflow and generally show low concentrations of ions, displaying an equal distribution of readily soluble components like Na or K throughout the water column, but distinct oxygen depletion in greater depths linked to rising concentrations of Fe and Mn, which indicates subterranean springs. Based on nutrients, chlorophyll a, and water transparency, lakes Dendi and Wonchi are classified as oligotrophic and Ziqualla as oligo-mesotrophic. The phytoplankton community is dominated by coccal green algae, desmids and dinoflagellates in lakes Dendi and Wonchi, typical for unpolluted dilute waterbodies; whereas chlorococcales, in particular Botryococcus braunii and benthic diatoms, prevail in Ziqualla. The zooplankton fauna is depauperate, comprising a total of 11 rotifer taxa and 13 crustaceans. Copepods were the most abundant group and contributed over 60% to the total zooplankton abundance in all three lakes, followed by rotifers and cladocerans. The conservation significance of these lakes lies predominantly in their representation of dilute, nutrient–poor highland lake systems that support diverse biota assemblages like desmids and daphnids, which are highly sensitive to eutrophication

The motion of whips and chains

We study the motion of an inextensible string (a whip) fixed at one point in the absence of gravity, satisfying the equations $$\eta_{tt} = \partial_s(\sigma \eta_s), \qquad \sigma_{ss}-\lvert \eta_{ss}\rvert^2 = -\lvert \eta_{st}\rvert^2, \qquad \lvert \eta_s\rvert^2 \equiv 1$$ with boundary conditions $\eta(t,1)=0$ and $\sigma(t,0)=0$. We prove local existence and uniqueness in the space defined by the weighted Sobolev energy $$\sum_{\ell=0}^m \int_0^1 s^{\ell} \lvert \partial_s^{\ell}\eta_t\rvert^2 \, ds + \int_0^1 s^{\ell+1} \lvert \partial_s^{\ell+1}\eta\rvert^2 \, ds,$$ when $m\ge 3$. In addition we show persistence of smooth solutions as long as the energy for $m=3$ remains bounded. We do this via the method of lines, approximating with a discrete system of coupled pendula (a chain) for which the same estimates hold.Comment: 47 pages, 8 figure

Friedrich Ritter von Wiesner

Das Thema dieser Arbeit ist Friedrich Ritter von Wiesner, seine Tätigkeit in der Österreichisch-Ungarischen Monarchie, seine Aktivitäten nach dem ersten Weltkrieg und seine Verfolgung durch die Nationalsozialisten. Diese Arbeit hat neben Akten aus Washington und aus verschiedenen Wiener Archiven hauptsächlich Beuteakten aus dem Moskauer Sonderarchiv als Grundlage, die zum großen Teil zurück nach Wien überstellt werden konnten und hier im Staatsarchiv im Archiv der Republik (AdR) eingeordnet sind. Von diesen war hauptsächlich der Nachlass Friedrichs Ritters von Wiesner, des Diplomaten und Legitimisten, Gegenstand der Untersuchung. Sein Tagebuch von 1898 und 1906, Aufzeichnungen zu Besprechungen im k.u.k. Ministerium des Äußern aus dem Juli 1914, Berichte vom Armeeoberkommando in Neu Sandez und Teschen während des Ersten Weltkrieges, Briefe an ihn vom ehemaligen Außenminister Czernin und vom Staatskanzler Renner, sowie Besprechungsprotokolle von Unterredungen mit diesem wegen der Übernahme der Leitung des Staatssekretariates für Äußeres stammen aus diesem Bestand. Zur Untersuchung der Legitimistischen Bewegung dienten Dokumente hauptsächlich aus dem Bestand des Reichsbundes der Österreicher, in dem Wiesner führend tätig war. Friedrich Wiesner, geboren 1871, Sohn des berühmten jüdischen Biologieprofessors Richard Ritter von Wiesner, der für seine Leistungen geadelt wurde, absolvierte das Gymnasium in Kremsmünster, studierte Jus an der Universität Wien und wurde Richter in Baden. Stets gewissenhaft bemüht, alles genau und wahrheitsgemäß zu erledigen, strebte er nach Selbsterkenntnis, wie er in seinem Tagebuch von 1898 festhielt. Dieses gewissenhafte Streben und sein Glaube an die Wahrheit brachte ihn einerseits weiter – 1911 trat er ins k.u.k. Ministerium des Äußern ein – und machte ihn zu einem angesehenen Mann, andererseits holte ihn stets die politisch-historische Realität ein, die seine Bemühungen ad absurdum führte. Sei es als Leiter der Untersuchungskommission des Thronfolgermordes in Sarajevo 1914, als der er einen gewissenhaften umfangreichen Bericht abgab, der erstens zu spät kam, zweitens zu kompliziert für die Öffentlichkeit und auch für die ausländischen Diplomaten, als dass er auf den Lauf der Dinge und den Kriegsausbruch Einfluss gehabt hätte. Sei es, als Karl Renner mit ihm in Verhandlungen trat, um ihm nach dem Rücktritt Otto Bauers die Leitung des Staatsamtes für Äußeres anzubieten. Da waren Wiesners Überlegungen zur Neuorganisation des Staatsamtes für Äußeres nach seinem besten Wissen und Gewissen, aber nicht von realpolitischen Überlegungen geprägt. Sei es auch in der legitimistischen Bewegung, die als solches zuerst vom Austrofaschismus und dann vom Nationalsozialismus überrollt wurde. Niemals gab Friedrich Wiesner seine Überzeugungen preis, an die er ehrlich glaubte und für die er sich einsetzte, um etwa politische Kompromisse zu schließen und pragmatisch gemäß der historischen Realität Vorteile zu gewinnen. So ist es eine logische Konsequenz der Geschichte, dass er in ein KZ inhaftiert wurde. Das Bemühen seiner Gattin Julia um seine Freilassung wird aus den Gauakten Wiesner sichtbar, worin auch ein Brief Julias enthalten ist, der zeigt, wie die alte Dame den schnellen Wandel von Wertigkeiten nach dem Anschluss nicht versteht, wenn sie, die in ihrem ganzen Leben eine monarchistische Einstellung als lobenswert erlebte, dem nationalsozialistischen Generalstaatsanwalt dieses ihr monarchistisches Bemühen als Argument ihrer Rechtschaffenheit darbietet. Die beiden alten Leute waren nach 1945 zu sehr mit sich selbst beschäftigt, als dass sie noch öffentlich tätig gewesen wären. Julia starb 1949 und Friedrich 1951. Sie sind im Familiengrab am Grinzinger Friedhof in Wien begraben. So werden anhand einer Lebensgeschichte die verschiedenen Epochen österreichischer Geschichte sichtbar und manifestiert sich das allgemeine historische Geschehen in dem einen Leben eines Mannes, der nicht in führender Position die Geschicke des Landes bestimmte aber auch nicht zur Masse des Volkes zu zählen ist, sondern in steten Bemühen immer versuchte, den Gang der Geschichte des Landes zu beeinflussen.The issue of this thesis is the person of Friedrich Ritter von Wiesner and his activities: first during the Austrian-Hungarian Monarchy, then after the end of this regime and finally his prosecution during the Nazi regime. This dissertation is based on records from various archives in Washington and Vienna, but mainly on records from the Moscow Special Archives. Many of these records used for this research in Moscow have been transferred back to Vienna and have been filed in the Austrian State Archives in the Archives of the Republic (AdR). For this research was the most important archival material the „fond“ „Friedrich Ritter von Wiesner, diplomat and legitimist“. (A certain collection is called „fond“ in the Archives in Moscow.) There we can find his diary from 1898 and 1906, also notes of meetings in 1914 at the k.u.k. Ministry of Foreign Affairs, and reports from the Field Army Command (AOK) in Nowy Sacz and Teschen during the World War I, further letters addressed to Wiesner written by Ottokar Graf von Czernin, the former Minister of Foreign Affairs, and those written by Karl Renner, the State Chancellor of the Republic. We also can find meeting minutes written by Wiesner after his conversation with Renner, who wanted to install him as State Secretary of Foreign Affairs. The „fond“ „Reichsbund der Österreicher“ (RBÖ) gives information about the monarchistic organization of RBÖ, in which Wiesner had a dominant position. Friedrich Wiesner, born in 1871, was the son of the famous Jewish biology professor Richard Ritter von Wiesner, who was honored with the title „Ritter“ due to his excellent work. Friedrich Wiesner graduated at the high school in Kremsmünster, studied law at the University of Vienna and became judge in Baden. He worked always conscientiously and tried to do everything exactly and truthfully. As he wrote in his diary of 1898 self-knowledge was important for him. On one hand his wish to find the truth and his manner to do things correctly was good for his career – in 1911 he got a job in the k.u.k. Ministry of Foreign Affairs, on the other hand the political and historical reality often made his efforts ineffective. I would like to illustrate this with some arguments. To allege an example we can consider the following fact: In Sarajevo in 1914 he investigated as head of the commission, whether Serbia was responsible for the assassination of the successor of the throne and his wife. At that time he conscientiously collected material for a comprehensive report, which was finished too late and was also too complicated for the public and for foreign diplomats, too, as it could have had any influence on the outbreak of war. A second example could be: After Otto Bauer has announced his resignation, Karl Renner offered to Wiesner the position of the head of the State Secretary of Foreign Affairs. In this situation Wiesner thought about, how to reorganize the State Secretary of Foreign Affairs according to his convictions, but his ideas failed to meet the requirements of real political situation in Austria and in the world. In the same way Wiesner being involved in the legitimistic movement was not sucessful, because this organization was less important than the Vaterländische Front and in 1938 the legitimists were persecuted by the Nazis. Friedrich Wiesner remained true to his principles and convictions, in which he believed honestly. Therefore he made no compromises due to which he could have gained personal advantages in a particular historical situation. According to this attitude it was a logical consequence of history that he was put into a concentration camp. The efforts of his wife Julia for his release are documented by the archival records of the “Gauakte Wiesner“, which are filed in the Austrian State Archives. There a letter written by Julia to the Nazi Generalstaatsanwalt is included showing us how she as an old lady did not understand the quick change of political system in 1938: She still emphasized her loyality to the former political system stressing her monarchistic connections in order to show her correct political attitude. After World War II Julia and Friedrich Wiesner were old, sick and occupied with themselves and therefore too weak to make policy. Julia died 1949 and Friedrich 1951. They are buried in the family grave in Grinzing cementary in Vienna. Thus studying the biography of this man we can understand the various epochs of Austrian history a bit more. Historical events are reviewed looking at the life of one man, who did not take up a really dominant position and could not really change the history of Austria, but who was not one of the common people, too

Sudden flamingo deaths in Kenyan rift valley lakes.

The East African Rift Valley Lakes Bogoria and Nakuru sometimes host around 75% of the world population of lesser flamingos Phoeniconaias minor. In this area, mysterious flamingo die-offs have occupied researchers for four decades. Recently, cyanobacterial toxins came into the fore as a possible explanation for mass mortalities because the main food source of lesser flamingos is the cyanobacterium Arthrospira fusiformis. We took weekly samples from July 2008 to November 2009 from Lakes Nakuru and Bogoria and analyzed them by high performance liquid chromatography for microcystins. Monthly, samples were cross-checked using protein phosphatase inhibition assays with lower detection limits and additionally screened for polar toxins. During our study period, three flamingo die-offs occurred at L. Bogoria and we were able to analyze tissues of 20 carcasses collected at the shoreline. No cyanotoxins were detected either in plankton samples or in flamingo tissues. Accordingly, other reasons such as food composition or bird diseases played a key role in the observed flamingo die-offs

The effect of ply folds as manufacturing defect on the fatigue life of CFRP materials

Manufacturing defects are inherent to any manufacturing process. However, in composite materials they might be unavoidable, e.g. ply waviness or even folds of plies are present in complex shaped parts during high pressure resin transfer molding of carbon fiber reinforced polymers. In this work, the effect of the ply folds on the fatigue life of the composite material is investigated. Folds along fiber direction (as they commonly appear during manufacturing) were artificially introduced in unidirectional non crimp fabric plies. The target of this study is the prediction of damage initiation due to this particular type of manufacturing defect. The folds locally increase the fiber volume fraction and also introduce resin rich areas. Fatigue tests in fiber direction and transverse to fiber direction are performed at different load ratios under constant amplitude loading. The influence of the defect geometry on damage initiation and progression is investigated at different scales by non-destructive methods before testing, continuous strain measurement and monitoring the damage progression during testing and fractography analysis after final failure. Most of the time, the first damage was observed at the location of the introduced fold for all considered load cases. However, it was also found, that the folds lead to no significant reduction in fatigue life.&nbsp