scholarly journals Biogeochemical Feedbacks to Ocean Acidification in a Cohesive Photosynthetic Sediment

2021 ◽  
Author(s):  
Kay Vopel ◽  
Alexis Marshall ◽  
Shelly Brandt ◽  
Adam Hartland ◽  
Charles K Lee ◽  
...  
Keyword(s):  
Ocean Acidification ◽  
Coastal Waters ◽  
Metabolic Response ◽  
Sediment Cores ◽  
Ambient Seawater ◽  
Dark Light ◽  
Sand Control ◽  
Negative Effect ◽  
And Control ◽  
Do So

Abstract Ecosystem feedbacks in response to ocean acidification can amplify or diminish the diel pH oscillations that characterize productive coastal waters. We report that benthic microalgae generate such oscillations in the porewater of cohesive sediment and ask how carbonation (acidification) of the overlying seawater alters these in the absence and presence of biogenic calcite. To do so, we placed a 1-mm layer of ground oyster shells (Treatment) or sand (Control) onto intact sediment cores free of large dwelling fauna, and then gradually increased the pCO2 in the seawater above half of the Treatment and Control cores from 472 to 1216 μatm (pH 8.0 to 7.6, CO2:HCO3- from 4.8 to 9.6 x 10-4). Vertical porewater [O2] and [H+] microprofiles measured 16 d later showed that this carbonation had decreased O2 penetration in all cores, indicating a metabolic response. In carbonated seawater: (1) sediment biogeochemical processes added and removed more H+ to and from the porewater in darkness and light, respectively, than in ambient seawater increasing the amplitude of the dark–light porewater [H+] oscillations, and (2) the dissolution of calcite decreased the porewater [H+] below that in overlying seawater, reversing the dark sediment–seawater H+ flux and decreasing the amplitude of diel [H+] oscillations. This dissolution did not, however, counter the negative effect of carbonation on sediment O2 penetration. We hypothesise that the latter effect and the observed enhanced acidification of the sediment porewater were caused by an ecosystem feedback: a CO2-induced increase in the microbial reoxidation of reduced solutes with O2.

scholarly journals Biogeochemical feedbacks to ocean acidification in a cohesive photosynthetic sediment

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Kay Vopel ◽  
Alexis Marshall ◽  
Shelly Brandt ◽  
Adam Hartland ◽  
Charles K. Lee ◽  
...  
Keyword(s):  
Ocean Acidification ◽  
Coastal Waters ◽  
Metabolic Response ◽  
Sediment Cores ◽  
Biogeochemical Processes ◽  
Ambient Seawater ◽  
Calcite Dissolution ◽  
Sand Control ◽  
Negative Effect ◽  
And Control

AbstractEcosystem feedbacks in response to ocean acidification can amplify or diminish diel pH oscillations in productive coastal waters. Benthic microalgae generate such oscillations in sediment porewater and here we ask how CO2 enrichment (acidification) of the overlying seawater alters these in the absence and presence of biogenic calcite. We placed a 1-mm layer of ground oyster shells, mimicking the arrival of dead calcifying biota (+Calcite), or sand (Control) onto intact silt sediment cores, and then gradually increased the pCO2 in the seawater above half of +Calcite and Control cores from 472 to 1216 μatm (pH 8.0 to 7.6, CO2:HCO3− from 4.8 to 9.6 × 10−4). Porewater [O2] and [H+] microprofiles measured 16 d later showed that this enrichment had decreased the O2 penetration depth (O2-pd) in +Calcite and Control, indicating a metabolic response. In CO2-enriched seawater: (1) sediment biogeochemical processes respectively added and removed more H+ to and from the sediment porewater in darkness and light, than in ambient seawater increasing the amplitude of the diel porewater [H+] oscillations, and (2) in darkness, calcite dissolution in +Calcite sediment decreased the porewater [H+] below that in overlying seawater, reversing the sediment–seawater H+ flux and decreasing the amplitude of diel [H+] oscillations. This dissolution did not, however, counter the negative effect of CO2 enrichment on O2-pd. We now hypothesise that feedback to CO2 enrichment—an increase in the microbial reoxidation of reduced solutes with O2—decreased the sediment O2-pd and contributed to the enhanced porewater acidification.

Electron Microscopy of a Herpesvirus Isolated from Marek's Disease in Duck and Chicken Embryo Fibroblast Cultures

1968 ◽  
Vol 26 ◽  
pp. 222-223 ◽  
Author(s):  
Keyvan Nazerian
Keyword(s):  
Inclusion Bodies ◽  
Chicken Embryo Fibroblast ◽  
Marek's Disease ◽  
Marek’S Disease ◽  
Duck Embryo Fibroblast ◽  
Multinucleated Cells ◽  
Viral Particles ◽  
Infected Cells ◽  
And Control ◽  
Do So

A herpes-like virus has been isolated from duck embryo fibroblast (DEF) cultures inoculated with blood from Marek's disease (MD) infected birds. Cultures which contained this virus produced MD in susceptible chickens while virus negative cultures and control cultures failed to do so. This and other circumstantial evidence including similarities in properties of the virus and the MD agent implicate this virus in the etiology of MD.Histochemical studies demonstrated the presence of DNA-staining intranuclear inclusion bodies in polykarocytes in infected cultures. Distinct nucleo-plasmic aggregates were also seen in sections of similar multinucleated cells examined with the electron microscope. These aggregates are probably the same as the inclusion bodies seen with the light microscope. Naked viral particles were observed in the nucleus of infected cells within or on the edges of the nucleoplasmic aggregates. These particles measured 95-100mμ, in diameter and rarely escaped into the cytoplasm or nuclear vesicles by budding through the nuclear membrane (Fig. 1). The enveloped particles (Fig. 2) formed in this manner measured 150-170mμ in diameter and always had a densely stained nucleoid. The virus in supernatant fluids consisted of naked capsids with 162 hollow, cylindrical capsomeres (Fig. 3). Enveloped particles were not seen in such preparations.

Potential of Islamic finance: A survey of Tunisian Northwest companies

2017 ◽  
Vol 5 (2) ◽  
pp. 28
Author(s):  
Rym Ammar Ayachi ◽  
Dhafer Saidane ◽  
Fayçal Mansouric
Keyword(s):  
Financial Institution ◽  
Islamic Finance ◽  
Islamic Banking ◽  
Islamic Banks ◽  
Finance Development ◽  
Negative Effect ◽  
Survey Results ◽  
Potential Demand ◽  
Northwest Region ◽  
Do So

The present paper aims to assess the Islamic products potential demand for entrepreneurs in the Tunisian Northwest region. In order to do so, we developed a questionnaire which was sent to these entrepreneurs. The survey results show that the latter perceive Islamic Finance as a seductive phenomenon. However, its development appears to be difficult. Indeed, according to the survey results, the lack of knowledge may impede the expansion of Islamic banking in Tunisia. Moreover, the following factors: cost, religious conviction, proximity, flexibility and satisfaction of the needs, may affect the entrepreneurs' choice to deal with Islamic financial institution. In addition, the lack of entrepreneurs' confidence with regard to the compliance of Islamic banking with the Shariah principles has a negative effect on Islamic finance development in the Tunisian Northwest region. For this reason, Tunisian Islamic banks should put more effort to reinforce their competitiveness.

scholarly journals Remix’s retreat? Content moderation, copyright law and mashup music

2021 ◽  
pp. 146144482110260
Author(s):  
Ragnhild Brøvig-Hanssen ◽  
Ellis Jones
Keyword(s):  
Online Survey ◽  
Copyright Infringement ◽  
Copyright Law ◽  
Online Media ◽  
Economic Power ◽  
Grey Zone ◽  
Negative Effect ◽  
State Of Affairs ◽  
Political Economic ◽  
And Control

Many online media platforms currently utilise algorithmically driven content moderation to prevent copyright infringement. This article explores content moderation’s effect on mashup music – a form of remix which relies primarily on the unauthorised combining of pre-existing, recognisable recordings. Drawing on interviews ( n = 30) and an online survey ( n = 92) with mashup producers, we show that content moderation affects producers’ creative decisions and distribution strategies, and has a strong negative effect on their overall motivation to create mashups. The objections that producers hold to this state of affairs often strongly resonate with current copyright exceptions. However, we argue that these exceptions, which form a legal ‘grey zone’, are currently unsatisfactorily accommodated for by platforms. Platforms’ political-economic power allows them, in effect, to ‘occupy’ and control this zone. Consequently, the practical efficacy of copyright law’s exceptions in this setting is significantly reduced.

After the Ivory Tower: Gender, Commodification and the ‘Academic’

1997 ◽  
Vol 55 (1) ◽  
pp. 130-142 ◽  
Author(s):  
Joanna de Groot
Keyword(s):  
Job Insecurity ◽  
Historical Context ◽  
Ivory Tower ◽  
Academic Identities ◽  
Loss Of Autonomy ◽  
External Power ◽  
Key Features ◽  
And Control ◽  
Radical Transformation ◽  
Do So

This piece uses a feminist approach to explore various aspects of ‘commodification’ in the lives and work of those teaching and researching in UK universities, and in particular its gender dimensions. After setting a historical context for the radical transformation of UK universities during the 1980s, it considers how this transformation was experienced by academics in terms of alienation, anxiety and accountability. Key features of that experience are loss of autonomy and control to the external power of competition and managerialism, insecurity and casualization in employment, and exposure to increasing judgemental scrutiny. For women academics job insecurity and discrimination continue to be disproportionately important, although some of the challenges to old established academic convention and practice have opened up real possibilities to progress more pro-women agendas. In the future they will confront quite depressing developments in the reconstruction of academic identities and labour, but have the legacy of the gains/insights of feminist analysis and politics over the last twenty years with which to do so.

Transition and the Pitfalls of Nondemocratic Institutions: A review of Constitutionality in Ethiopia

2021 ◽  
Vol 2021 (1) ◽  
pp. 67-87
Author(s):  
Tadesse Melaku
Keyword(s):  
Case Analysis ◽  
Democratic Governance ◽  
Institutional Reforms ◽  
Constitutional Review ◽  
The Past ◽  
Government Power ◽  
Review Mechanism ◽  
And Control ◽  
Regional Elections ◽  
Do So

Ethiopia has undertaken important political reforms after the fall of authoritarianism in 2018. This article examines the performance of Ethiopia’s constitutional review mechanism amid the ongoing political and institutional reforms in the country. The study focuses on the process and merit of the constitutional ruling to delay the 2020 national and regional elections because of the coronavirus pandemic, thereby extending the government’s tenure. It further unravels the challenges posed by nondemocratic institutions of the past regime in navigating the transition. In doing so, this study draws on legal, documentary and case analysis, and a literature review. While the mandate extension comes as no surprise, the reasoning of the decision to do so was disappointing for many, dashing the hope and sense of a constitutional moment that accompanied the highly publicised constitutional hearing process in June 2020. The judgment reveals an endemic deficiency of the institutional system. Thus, it is imperative for Ethiopia to establish an independent constitutional umpire to check and control the exercise of government power and support the transition to multiparty democratic governance in the country.

Caligids-potential pathogens for marine finfish aquaculture in Mexico?

2017 ◽  
Vol 44 (3) ◽  
pp. 433-441
Author(s):  
Francisco Neptalí Morales-Serna ◽  
Juan Manuel Martínez-Brown ◽  
Rosa Maria Medina-Guerrero ◽  
Emma Josefina Fajer-Ávila
Keyword(s):  
Coastal Waters ◽  
Host Location ◽  
Current Knowledge ◽  
Control Strategies ◽  
Sea Lice ◽  
Ecological Studies ◽  
Parasitic Copepods ◽  
The Family ◽  
And Control ◽  
Finfish Aquaculture

Parasitic copepods of the family Caligidae, the so-called sea lice, may be deleterious to marine or brackish finfish aquaculture. To date, biological and ecological studies of sea lice have been mostly restricted to species from cold or temperate regions. In Mexico there are some records of sea lice species on marine fishes; however, the research regarding their biology and ecology has been scarce. It is possible that a high biodiversity of sea lice is distributed in coastal waters of Mexico; therefore, their significance as pathogenic parasites should increase. The purpose of this review is to outline the current knowledge of the life cycle, host location, ecology, effect on fish health, and control strategies of sea lice in order to establish supportive basis for natural resource management and control of parasites and diseases of marine fish cultured in Mexico.

scholarly journals Automatic Promotion and Student Dropout: Evidence from Uganda, Using Propensity Score in Difference in Differences Model

2018 ◽  
Vol 7 (2) ◽  
pp. 191 ◽  
Author(s):  
Jeje Moses Okurut
Keyword(s):  
Propensity Score ◽  
Dropping Out ◽  
Probit Regression ◽  
Difference In Differences ◽  
Student Dropout ◽  
Analysis Technique ◽  
Analysis Strategy ◽  
Negative Effect ◽  
And Control ◽  
The Impact

The impact of automatic promotion practice on students dropping out of Uganda’s primary education was assessed using propensity score in difference in differences analysis technique. The analysis strategy was instrumental in addressing the selection bias problem, as well as biases arising from common trends over time, and permanent latent differences between the treated and control groups. Probit regression results indicate a negative effect on the probability of students dropping out, but only at P3. There seems to be no policy effect at P6. Decomposing the effect incidence along school location shows the policy as having had an effect only on P3 students studying in urban schools; otherwise, there is no effect among students at P3 rural, P6 rural or P6 Urban. In terms of the gender component, automatic promotion appears to have had an effect on P3 male and female students and no effect on either sex at P6.

scholarly journals Analysis and control of flow at suction connection in high-speed centrifugal pump

2017 ◽  
Vol 9 (1) ◽  
pp. 168781401668529 ◽  
Author(s):  
Wen-wu Song ◽  
Li-chao Wei ◽  
Jie Fu ◽  
Jian-wei Shi ◽  
Xiu-xin Yang ◽  
...  
Keyword(s):  
Flow Field ◽  
Centrifugal Pump ◽  
High Speed ◽  
Internal Flow ◽  
Orifice Plate ◽  
Centrifugal Pumps ◽  
Pressure Area ◽  
Negative Effect ◽  
And Control ◽  
Experimental Data Analysis

The backflow vortexes at the suction connection in high-speed centrifugal pumps have negative effect on the flow field. Setting an orifice plate in front of the inducer is able to decrease the negative effect caused by backflow vortexes. The traditional plate is able to partially control the backflow vortexes, but a small part of the vortex is still in the inlet and the inducer. Four new types of orifice plates were created, and the control effects on backflow vortexes were analyzed. The ANSYS-CFX software was used to numerically simulate a high-speed centrifugal pump. The variations of streamline and velocity vectors at the suction connection were analyzed. Meanwhile, the effects of these plates on the impeller pressure and the internal flow field of the inducer were analyzed. Numerically, simulation and experimental data analysis methods were used to compare the head and efficiency of the high-speed pumps. The results show that the C-type orifice plate can improve the backflow vortex, reduce the low-pressure area, and improve the hydraulic performance of the high-speed pump.

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