The dynamics of nano- and microplankton in the St. Lucia estuarine lake system, KwaZulu-Natal.

Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2013.St. Lucia estuarine lake system has a history of episodic droughts and floods leading to a high variability in physico-chemical characteristics which may influence the community structure of nano- and microplankton that are the main primary energy synthesisers in aquatic systems. Originally, the St. Lucia estuary and the Mfolozi River shared the same mouth with the Mfolozi River acting as the main source of fresh water to the system and as stabiliser of the common inlet. Due to prolonged mouth closure from 2001-2012 and high evaporation rates, severe extended droughts and high salinities were experienced in 2001-2012.This project aimed to characterise community composition and biomass of nano-and microplankton (autotrophic and heterotrophic) under the varying and extreme physico-chemical conditions in order to characterize the energy basis of the planktonic food web in St. Lucia. Its main objectives were to compare and add onto Johnson’s (1977) list of phytoplankton taxa in the system, to estimate the biomass (carbon) of nano- and microplankton from cell counts and biovolume measurements, and lastly to understand and establish trends in the change in community structure of these organisms with the varying physico-chemical characteristics. Nano- and microplankton samples were collected monthly from October 2010 to September 2011 at three different sites: Lister’s Point, Charters Creek and the mouth representing the lakes and estuary Channel. Chlorophyll a and physico-chemical parameters were also measured in situ during collection. In the lab, samples were settled using the Utermöhl method and species were identified to at least genus level, counted and cell measurements taken under an inverted microscope for biovolume calculations and biomass thereof. Abundance in cells per liter and biomass (carbon) in pg/L was then analyzed from the counts. The nano-and microplankton groups recorded in the system were cyanobacteria, chlorophytes, cryptophytes, dinoflagellates, ciliates and diatoms. Seventy eight phytoplankton taxa were identified composed of 56 diatoms, eight green algae, one cryptophyte, seven cyanobacteria and six dinoflagellate taxa. Nineteen ciliate taxa were also found. Only 12 of the diatom taxa identified in this study were listed by Johnson (1977), none of the taxa in the other phytoplankton groups was listed by Johnson (1977). The Johnson (1977) study conducted in the system from 1975-1977 listed the phytoplankton taxa occurring at that time. There was no significant difference in the community composition, biovolume and biomass between seasons hence no seasonal trend however, there were significant differences in the nano- and microplankton community composition, biovolume and biomass at the three different sites of the system. Cyanobacteria were the main taxa in the northern embayments dominating in abundance, biovolume and biomass (biological variables), green algae and cryptophytes dominated in abundance, biovolume and biomass in the Channels while in South Lake, green algae dominated in abundance but diatoms dominated in biovolume and biomass. Ciliate biological variables were higher in the northern regions than in the other parts of the estuary. The absence or limited grazing pressure of ciliate predators in the northern region due to their inability to cope with the extreme salinities compared to the other parts of the system explains why the northern embayments had the highest abundance, biovolume and biomass of ciliates. Ciliates and heterotrophic dinoflagellates were the heterotrophs in this study. Autotrophic:heterotrophic biomass ratio was lowest in the northern regions as heterotrophs had a higher biomass there. This ratio was higher in the South Lake and the Channel. The lack of stratification and generally high turbidity in the system made the system unfavourable for dinoflagellate growth. The higher presence of ciliate predators in the South Lake and Channel probably accounts for the low heterotrophic biomass hence high autotrophic:heterotrophic biomass ratio in South Lake and the Channel. Nutrients were not limiting during this study and salinity was the main physico-chemical characteristic accounting for the differences in nano- and microplankton biological variables. The Cyanothece bloom in the northern region was primarily due to high salinities (>150) which also indicated unfavourable conditions for other plankton types. The high diatom biomass in the southern lake was due to low salinities (<28) which favoured their growth, whereas chlorophytes and cryptophytes dominated in the Channel mainly due to low turbidity (median of 11.4NTU) and fresh water input from the Mfolozi lowering salinities (<5). The South Lake and Channel thus had the highest available energy for higher trophic level organism since 1) diatoms and green algae are the most favoured food source for phytoplankton grazers while the cyanobacteria though most abundant are the least favoured food source leaving the northern lake with smaller energy source for higher trophic level organisms and 2) The low autotrophic:heterotrophic biomass ratio in the northern region leaves the region with a lower net carbon biomass than the other parts of the system with a higher autotrophic: heterotrophic biomass

Remineralization of a Dystric Ferralsol Using Basalt and Tephra Dusts, Effective Microorganisms Manure and NPK 20-10-10 for Radish (Raphanus sativus) Production in Bamougoum (Cameroon Western Highlands)

This paper studies the effect of basalt and tephra dusts, as alternatives to chemical fertilizers, on soil fertility and Radish (Raphanus sativus) production. The experiment was conducted in the field and in the laboratory in the years 2017 and 2018 on two separate plots so as to annul residual effects of fertilizers). The experimental design in the field was a randomized complete block design (56 m2 ), including five treatments and three replications: control (T0), basalt dust (T1), tephra dust (T2), effective micro-organism (EM) fertilizer (T3) and NPK 20-10-10 (T4). The main results show the following decreasing trend based on yield: T1>T3>T0>T4>T2. The best yields appear in T1 and T3 probably because they supplied the highest levels of soil nutrients to match the needs of the crops. Although T2 plants performed poorly, soil properties like pH.H2O (6.14 to 6.49), sum of exchangeable bases, base saturation, available phosphorus and cation balance were improved after tephra treatment. T2 plants might have performed poorly due to intrinsic properties of the tephra dust like low availability of trace elements compared to T1 and T3. T4 plants show the highest number of leaves, leaf area index and plant height. The Fe, Mn, Cu and Zn levels in bulbs and leaves will not pose danger of toxicity to human upon consumption and could serve as nutrient supplement for children and expectant mothers. The most profitable treatment is T1 permitting to recommend the popularization of basalt dust for radish cultivation as an alternative to chemical fertilizers

Functional analysis and transcriptional output of the Göttingen minipig genome

In the past decade the Göttingen minipig has gained increasing recognition as animal model in pharmaceutical and safety research because it recapitulates many aspects of human physiology and metabolism. Genome-based comparison of drug targets together with quantitative tissue expression analysis allows rational prediction of pharmacology and cross-reactivity of human drugs in animal models thereby improving drug attrition which is an important challenge in the process of drug development.; Here we present a new chromosome level based version of the Göttingen minipig genome together with a comparative transcriptional analysis of tissues with pharmaceutical relevance as basis for translational research. We relied on mapping and assembly of WGS (whole-genome-shotgun sequencing) derived reads to the reference genome of the Duroc pig and predict 19,228 human orthologous protein-coding genes. Genome-based prediction of the sequence of human drug targets enables the prediction of drug cross-reactivity based on conservation of binding sites. We further support the finding that the genome of Sus scrofa contains about ten-times less pseudogenized genes compared to other vertebrates. Among the functional human orthologs of these minipig pseudogenes we found HEPN1, a putative tumor suppressor gene. The genomes of Sus scrofa, the Tibetan boar, the African Bushpig, and the Warthog show sequence conservation of all inactivating HEPN1 mutations suggesting disruption before the evolutionary split of these pig species. We identify 133 Sus scrofa specific, conserved long non-coding RNAs (lncRNAs) in the minipig genome and show that these transcripts are highly conserved in the African pigs and the Tibetan boar suggesting functional significance. Using a new minipig specific microarray we show high conservation of gene expression signatures in 13 tissues with biomedical relevance between humans and adult minipigs. We underline this relationship for minipig and human liver where we could demonstrate similar expression levels for most phase I drug-metabolizing enzymes. Higher expression levels and metabolic activities were found for FMO1, AKR/CRs and for phase II drug metabolizing enzymes in minipig as compared to human. The variability of gene expression in equivalent human and minipig tissues is considerably higher in minipig organs, which is important for study design in case a human target belongs to this variable category in the minipig. The first analysis of gene expression in multiple tissues during development from young to adult shows that the majority of transcriptional programs are concluded four weeks after birth. This finding is in line with the advanced state of human postnatal organ development at comparative age categories and further supports the minipig as model for pediatric drug safety studies.; Genome based assessment of sequence conservation combined with gene expression data in several tissues improves the translational value of the minipig for human drug development. The genome and gene expression data presented here are important resources for researchers using the minipig as model for biomedical research or commercial breeding. Potential impact of our data for comparative genomics, translational research, and experimental medicine are discussed

Lanthanoid Implantation for Effective Work Function Control in NMOS High‐κ∕Metal Gate Stacks

Effective work function instability of high‐κ∕metal gate MOS stacks after high temperature treatment results in device threshold voltage shifts and is one of the problems associated with the gate‐first integration of high‐κ dielectrics in the CMOS process flow. The exact reason for this instability is subject of intense debate. In this paper it is shown that a positive threshold voltage shift due to thermal treatment can be compensated by implanting the lanthanoids lanthanum or dysprosium into the high‐κ stack

Austrittsarbeitskontrolle für Metall/Hoch-E MOS Stapel

Continuous scaling down of semiconductor device dimensions has been key to the semiconductor industry being able to deliver better performing electronics at reduced costs. At the time of writing, CMOS manufacturing technology is at the 32 nm node, which requires an SiO2 gate insulation thickness of less than 1 nm. At such thicknesses, the direct tunneling gate leakage current is extremely high, leading to high power consumption. To overcome this problem, industry consensus has been to replace SiO2 by high permittivity (high-k) dielectrics. Hafnium-based high-k dielectrics are favored for this substitution. The conventional polysilicon gate has also been replaced by a metal gate in order to eliminate the parasitic effect of charge depletion at the polysilicon/high-k interface. This novel gate stack is, however, not stable to high temperature (1000°C) anneals used in semiconductor processing. A major difficulty is the change in the transistor threshold voltage after source/drain anneals, which implies a shift of the effective work function (EWF) of the gate electrode. The threshold voltage increases both for NMOS and PMOS devices. In this work, it is shown that by doping metal/high-k transistor gate stacks by ion implantation the EWF can be controlled. This allows the use of a single metal for both PMOS and NMOS devices in a gate-first integration scheme. A fluorine-doped TiN/HfSiOx or TiN/HfO2 gate stack achieves an EWF of about 5.1 eV for PMOS devices. For NMOS devices, lanthanum-doped TiN/HfSiOx gate stacks achieve an EWF of about 4.0 eV.Der Erfolg der Halbleiterindustrie beruht darauf, durch stetige Skalierung des MOS Transistors immer leistungsfähigere Elektronik bei stetig sinkender Preise anbieten zu können. Zurzeit befindet sich die CMOS-Fertigung bei der 32-nm-Technologie, die eine SiO2Gate-Oxiddicke von ungefähr 1 nm für MOS Transitoren verlangt. Bei solchen Oxiddicken führen steigenden Gate-Leckströme zu hohem Energieverbrauch. Solch ein dünnes Oxid ist schlecht isolierend, was zu höhe Leckströme und Energieverbrauch des Transistors führt. Mit abnehmender Oxiddicke steigen Gate-Leckströme und Energieverbrauch der Transistoren an. Der Lösungsansatz der Industrie besteht darin SiO2 durch ein Dielektrikum mit höherer Dielektrizitätskonstante zu ersetzen. Auf Hafnium basierte Dielektrika sind hierfür favorisiert. Dadurch ist ein dickeres Gateoxid und niedriger Leckstrom möglich. Die konventionelle Polysilicium-Gate-Elektrode wird durch Metall ersetzt, um den Verarmungseffekt von Polysilicium an der Grenzfläche Polysilicium/High-K zu vermeiden. Die Einsatzspannung von Metall/High-K Transistoren verändert sich nach dem S/D-Ausheilschritt während der Herstellung: es kommt zu einer Verschiebung der effektiven Austrittsarbeit (EWF-Effective Work Function) des Gate-Metalls. Die Einsatzspannung erhöht sich um 0.2 V für NMOS und -0.6 V für PMOS Bauelemente. In dieser Arbeit wird gezeigt wie sich die effektive Austrittsarbeit des Metall/High-K Stapels mit einem einzigen Metall bei einem Gate-first Herstellungsverfahren, mittels Ionenimplantation einstellen lässt. So lässt sich eine EWF von ungefähr 4,0 eV für NMOS Transistoren mit einem Lanthan-dotierten TiN/HfSiOx (TiN/HfO2) Gate-Stapel einstellen. Für PMOS-Bauelemente, kann die benötigte EWF von 5,1 eV mit einer Fluor-Dotierung erreicht werden

Alterations of cellular electrophysiology and Ca2+-handling in patients with different forms of atrial fibrillation

Atrial Fibrillation (AF) is the most common clinical arrhythmia. When AF occurs after (cardiac) surgery it is referred to as postoperative AF (poAF). Though usually self-limiting, uncontrolled poAF can cause debilitating strokes and prolong hospital stay. A multifactorial pathophysiology involving triggered activity has been hypothesized, but the cellular and molecular mechanisms underlying poAF remain unknown and were the subject of the first part of this study. The second part of this study focused on inward-rectifier K+ currents like IK1, which stabilize the resting membrane potential. It has been suggested to contribute to the shorter action potentials that promote reentry in chronic AF (cAF). However, the exact magnitude of IK1 in cAF is unknown and was investigated. Membrane currents (whole-cell voltage clamp) and [Ca2+]i (Fluo-3) epifluorescence were measured in right-atrial cardiomyocytes from patients with sinus-rhythm (Ctl, n=58), poAF (n=46) or cAF (n=6). Protein expression was quantified by immunoblot. Amplitude of L-type Ca2+ current was unchanged, whereas the L-type Ca2+ current-triggered [Ca2+]i transient amplitude was reduced by 35% in poAF vs Ctl, likely contributing to the ~44% reduction in fractional cell shortening. Sarcoplasmic reticulum (SR) Ca2+ content, calculated by integrating Na+-Ca2+ exchange current during caffeine (10 mM)-induced SR Ca2+ release, was unchanged, consistent with the unaltered protein expression of the SR Ca2+ ATPase type-2a and its regulator phospholamban. When challenged with interleukin-1 as a postoperative trigger the frequency of potentially proarrhythmic spontaneous SR Ca2+ release events was increased, likely due to hyperphosphorylation of ryanodine receptor channels at Ser2014 (34%), whereas protein expression of the ryanodine receptor channel regulators triadin, junctin, junctophilin-2 and calsequestrin was unaltered. In cAF, basal inward-rectifier K+ current was increased, whereas the major effector of vagal nerve stimulation, the acetylcholine-activated K+ current IK,ACh, was reduced compared to Ctl patients. Application of the selective IK1-inbititor PA-6 (200 nM) to basal inward-rectifier K+ current unmasked a larger “pure” IK1 in cAF compared to Ctl patients. In summary, we discovered that poAF is associated with Ca2+-handling abnormalities that predispose patients to cellular triggered activity underlying poAF. We could demonstrate using PA-6; a novel inhibitor of IK1, that “pure” IK1 is larger in cAF. Our data improve our understanding of atrial cellular arrhythmogenic mechanisms in AF in general and in poAF in particular, potentially facilitating the development of improved therapeutic anti-AF strategies.Vorhofflimmern (VHF) ist die häufigste klinische Arrhythmie. Wenn es nach herzchirurgischen Eingriffen auftritt, wird es als postoperatives VHF (poVHF) bezeichnet. Wenngleich normalerweise selbstlimitierend, kann unkontrolliertes poVHF Schlaganfälle und einen verlängerten Krankenhausaufenthalt verursachen. PoVHF liegt vermutlich eine multifaktorielle Pathophysiologie zugrunde, wobei der „getriggerten“ Aktivität eine zentrale Rolle zukommen könnte. Die genauen zellulären Mechanismen des poVHF sind unbekannt und waren Gegenstand des ersten Teils dieser Arbeit. Der zweite Teil der Arbeit befasste sich mit einwärtsgleichrichtenden K+-Strömen wie dem IK1, die das negative Ruhemembranpotential aufrechterhalten. Es wird vermutet, dass diese zur Verkürzung der Aktionspotentiale beitragen und die Entstehung kreisender Erregungen („Reentry“) bei chronischem VHF (cVHF) begünstigen, wobei die genaue Größe des IK1 bei cVHF bisher unbekannt war. Membranströme („whole-cell voltage clamp“) und [Ca2+]i (Fluo-3) Epifluoreszenz wurden in rechtsatrialen Kardiomyozyten von Patienten mit Sinusrhythmus (Ktr, n=58), mit poVHF (n=46) oder mit cVHF (n=6) registriert. Die Proteinexpression wurde mittels Immunoblot quantifiziert. Die Amplitude des L-Typ Ca2+-Stromes war unverändert, während die L-Typ Ca2+-Strom ausgelöste [Ca2+]i-Transientamplitude beim poVHF um 35% reduziert war. Entsprechend war die relative Zellverkürzung um ~44% vermindert. Der Ca2+-Gehalt im sarkoplasmatischen Retikulum (SR), der durch Integration des Na+-Ca2+--Austauschstroms während der Koffein (10 mM)-ausgelösten Ca2+-Freisetzung aus dem SR berechnet wurde, war unverändert. Dies stimmte mit der unveränderten Proteinexpression der SR Ca2+-ATPase Typ-2a und dessen Regulator Phospholamban überein. Der Einsatz von Interleukin-1 als postoperativer Trigger steigerte die Frequenz spontaner proarrhythmischer Ca2+-Freisetzungen aus dem SR, möglicherweise aufgrund der Zunahme der Ser2014-Hyperphosphorylierung der Ryanodin-Rezeptorkanäle (~34%). Die Proteinexpression der Ryanodin-Rezeptorkanal-Regulatoren Triadin, Junctin, Junctophilin-2 und Calsequestrin blieb dagegen unverändert. Beim cVHF war der basale einwärtsgleichrichtende K+-Strom erhöht, während der Haupteffektor einer Stimulation von Nervus vagus, der Acetylcholin-aktivierte K+-Strom IK,ACh, reduziert war. Die Applikation des selektiven IK1-Inhibitors PA-6 (200 nM) beim cVHF konnte einen größeren "reinen" IK1 aufdecken. Zusammenfassend konnten wir nachweisen, dass poVHF mit Störungen der Ca2+-Homöostase assoziiert ist. Letzteres könnte das Auftreten von „getriggerter“ Aktivität als Auslöser von poVHF begünstigen. Wir konnten außerdem zeigen, dass PA-6; ein neuartiger Inhibitor von IK1, einen erhöhten IK1 beim cVHF demaskierte. Unsere Daten verbessern unser Verständnis der zellulären Mechanismen von III VHF, insbesondere von poVHF, und könnten zur Entwicklung von neuen therapeutischen Strategien für VHF führen

Micronutrient Composition of Soils and Supported Solanum scabrum in Bafut Sub-division (North-West Cameroon)

Soil-plant metal interaction is vital in plant metabolism and on effects related to deficiency and toxicity, yet has received very little attention in terms of research in developing countries. The aim of the present study was to investigate the composition of Zn, Cu, Mn and Fe in soils and grown huckleberry (Solanum scabrum) in Bafut Sub-division (North-West Cameroon). Soils and huckleberry samples were collected in North and South Bafut in the rainy and dry seasons. The micronutrient levels in&nbsp;Solanum scabrum&nbsp;and soils were measured by Atomic Absorption Spectrometry. The results revealed that the metal levels of the soils were within the permissible range for agricultural soils. In the vegetables, only Fe and Mn, the most represented metals, were within the adequate and normal levels for optimum plant growth and human consumption, while Cu and Zn contents suggested a dietary intake deficiency for the inhabitants of the study area. The soil-metal transfer factors were globally less than 1 (0.03 to 0.95), lowest for Cu and highest for Fe. Between sites, Fe contents were fairly higher in South Bafut soils, while Zn, Mn and Cu were higher in North Bafut soils. These differences could be explained by the variation in the nature of parent rock in both localities and the slightly acidic soil pH which influences the solubility, mobility and bioavailability of soil nutrients. Between seasons, there was no significant difference (P&lt;.05) between metal concentrations of soils and&nbsp;Solanum scabrum, except for Cu in the dry season vegetables. The present work suggests that&nbsp;S. scabrumcould serve as a cheaper source of micronutrients especially Fe and Mn for the local inhabitants of Bafut and beyond. &nbsp

Genesis and classification of soils developed on gabbro in the high reliefs of Maroua region, North Cameroon

The purpose of this work was to examine the genesis, properties and classification of soils resulting from the weathering of gabbro rock in the high reliefs of Maroua in the Far North Region of Cameroon. The studied soils were ~ 2 m thick, made of four horizons which consisted of coarse saprolite, fine saprolite, loose loamy clayey horizon and humiferous horizon. From petrographical view point, at the bottom of the soil profile, the preservation of the bedrock structure was marked by numerous remnants of altered plagioclases shapes. The groundmass was characterized by a double spaced fine, ranging to equal, enaulic c/f related distribution pattern. It was yellowish, characterized by weakly separated granular microstructure in the fine saprolite and had a speckled and cloudy limpidity in the loose loamy clayey horizon. Secondary minerals consisted of montmorilonite, kaolinite, goethite, quartz, gibbsite, lepidocrocite, sepiolite, feldspar and calcite. Globally, Si/Al ratio ranged between 2.85 and 3.24. The chemical index of alteration ranged from 50.95 to 55.27 % while the mineralogical index of alteration values were between 1.90 and 10.54 %. Physicochemically, soil pH varied from slightly acidic to slightly above neutral. Soil organic carbon contents were low to very low. Exchangeable bases contents were high, mostly represented by Ca2+ and Mg2+. The CEC of soils and the CEC of clay were also high, ranging respectively between 53.68 and 82.88 cmol(+).kg-1, and 116.80 and 181.38 cmol(+).kg-1. The studied soils were classified as dystric haplustepts clayey isohyperthermic. They were developed in situ by the collapse of primary mineral structures from the bottom of the coarse saprolite, due to leaching as a result of bisiallitisation and monosiallitisation. This is accompanied by a progressive ferruginization of materials, confirmed by the densification under the microscope of goethitic brown veil from the base to the loamy clay horizon and the increase in iron contents from the bedrock to the humiferous surface horizon