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Search Results: 1 - 10 of 297500 matches for " J. Harlay "
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Individual and interacting effects of pCO2 and temperature on Emiliania huxleyi calcification: study of the calcite production, the coccolith morphology and the coccosphere size
C. De Bodt,N. Van Oostende,J. Harlay,K. Sabbe
Biogeosciences Discussions , 2009,
Abstract: The impact of ocean acidification and increased water temperature on marine ecosystems, in particular those involving calcifying organisms, has been gradually recognised. We examined the individual and combined effects of increased pCO2 (180 ppm V CO2, 380 ppm V CO2 and 750 ppm V CO2 corresponding to past, present and future CO2 conditions, respectively) and temperature (13°C and 18°C) during the calcification phase of the coccolithophore E. huxleyi using batch culture experiments. We showed that the cell abundance-normalized particulate organic carbon concentration (POC) increased from the present to the future CO2 treatments. A significant effect of pCO2 and of temperature on calcification was found, manifesting itself in a lower cell abundance-normalized particulate inorganic carbon (PIC) content as well as a lower PIC:POC ratio at future CO2 levels and at 18°C. Coccosphere-sized particles showed a size reduction trend with both increasing temperature and CO2 concentration. The influence of the different treatments on coccolith morphology was studied by categorizing SEM coccolith micrographs. The number of well-formed coccoliths decreased with increasing pCO2 while temperature did not have a significant impact on coccolith morphology. No interacting effect of pCO2 and temperature was observed on calcite production, coccolith morphology or on coccosphere size. Finally, our results suggest that ocean acidification might have a larger adverse impact on coccolithophorid calcification than surface water warming.
Individual and interacting effects of pCO2 and temperature on Emiliania huxleyi calcification: study of the calcite production, the coccolith morphology and the coccosphere size
C. De Bodt, N. Van Oostende, J. Harlay, K. Sabbe,L. Chou
Biogeosciences (BG) & Discussions (BGD) , 2010,
Abstract: The impact of ocean acidification and increased water temperature on marine ecosystems, in particular those involving calcifying organisms, has been gradually recognised. We examined the individual and combined effects of increased pCO2 (180 ppmV CO2, 380 ppmV CO2 and 750 ppmV CO2 corresponding to past, present and future CO2 conditions, respectively) and temperature (13 °C and 18 °C) during the exponential growth phase of the coccolithophore E. huxleyi using batch culture experiments. We showed that cellular production rate of Particulate Organic Carbon (POC) increased from the present to the future CO2 treatments at 13 °C. A significant effect of pCO2 and of temperature on calcification was found, manifesting itself in a lower cellular production rate of Particulate Inorganic Carbon (PIC) as well as a lower PIC:POC ratio at future CO2 levels and at 18 °C. Coccosphere-sized particles showed a size reduction with both increasing temperature and CO2 concentration. The influence of the different treatments on coccolith morphology was studied by categorizing SEM coccolith micrographs. The number of well-formed coccoliths decreased with increasing pCO2 while temperature did not have a significant impact on coccolith morphology. No interacting effects of pCO2 and temperature were observed on calcite production, coccolith morphology or on coccosphere size. Finally, our results suggest that ocean acidification might have a larger adverse impact on coccolithophorid calcification than surface water warming.
A Survey on Optimistic Fair Digital Signature Exchange Protocols
Alfin Abraham,Vinodh Ewards,Harlay Maria Mathew
International Journal on Computer Science and Engineering , 2011,
Abstract: Security services become crucial to many applications such as e-commerce payment protocols, electronic contract signing, and certified e-mail delivery, with the phenomenal growth of the Internet and open networks. For these applications fair exchange must be assured. A fair protocol allows two parties to exchange digital signatures over the Internet in a fair way, so that either each party gets the other’s signature, or neither party does. This paper, gives a survey on the most important fair and optimistic digital signature exchange protocols. Optimistic, means the third trusted party (TTP) is involved only in the situations where one party is cheating or the communication channel is interrupted, i.e., TTP is offline. As more business is conducted over the Internet, the fair-exchange problem is gaining greater importance. This paper also provides an analysis of basic features, security, and efficiency of digital signature exchange protocols.
New components of the mercury’s perihelion precession  [PDF]
J. J. Smulsky
Natural Science (NS) , 2011, DOI: 10.4236/ns.2011.34034
Abstract: The velocity of perihelion rotation of Mercury's orbit relatively motionless space is computed. It is prove that it coincides with that calculated by the Newtonian interaction of the planets and of the compound model of the Sun’s rotation.
Simple General Purpose Ion Beam Deceleration System Using a Single Electrode Lens  [PDF]
J. Lopes, J. Rocha
World Journal of Engineering and Technology (WJET) , 2015, DOI: 10.4236/wjet.2015.33014
Abstract: Ion beam deceleration properties of a newly developed low-energy ion beam implantation system were studied. The objective of this system was to produce general purpose low-energy (5 to 15 keV) implantations with high current beam of hundreds of μA level, providing the most wide implantation area possible and allowing continuously magnetic scanning of the beam over the sample(s). This paper describes the developed system installed in the high-current ion implanter at the Laboratory of Accelerators and Radiation Technologies of the Nuclear and Technological Cam-pus, Sacavém, Portugal (CTN).
Constraints on velocity anisotropy of spherical systems with separable augmented densities
J. An
Physics , 2011, DOI: 10.1088/0004-637X/736/2/151
Abstract: If the augmented density of a spherical anisotropic system is assumed to be multiplicatively separable to functions of the potential and the radius, the radial function, which can be completely specified by the behavior of the anisotropy parameter alone, also fixes the anisotropic ratios of every higher-order velocity moment. It is inferred from this that the non-negativity of the distribution function necessarily limits the allowed behaviors of the radial function. This restriction is translated into the constraints on the behavior of the anisotropy parameter. We find that not all radial variations of the anisotropy parameter satisfy these constraints and thus that there exist anisotropy profiles that cannot be consistent with any separable augmented density.
On the augmented density of a spherical anisotropic dynamic system
J. An
Physics , 2010, DOI: 10.1111/j.1365-2966.2011.18324.x
Abstract: This paper presents a set of new conditions on the augmented density of a spherical anisotropic system that is necessary for the underlying two-integral phase-space distribution function to be non-negative. In particular, it is shown that the partial derivatives of the Abel transformations of the augmented density must be non-negative. Applied for the separable augmented densities, this recovers the result of van Hese et al. (2011).
Fractional calculus, completely monotonic functions, a generalized Mittag-Leffler function and phase-space consistency of separable augmented densities
J. An
Physics , 2012,
Abstract: Under the separability assumption on the augmented density, a distribution function can be always constructed for a spherical population with the specified density and anisotropy profile. Then, a question arises, under what conditions the distribution constructed as such is non-negative everywhere in the entire accessible subvolume of the phase-space. We rediscover necessary conditions on the augmented density expressed with fractional calculus. The condition on the radius part R(r^2) -- whose logarithmic derivative is the anisotropy parameter -- is equivalent to R(1/w)/w being a completely monotonic function whereas the condition on the potential part is stated as its derivative up to the order not greater than 3/2-b being non-negative (where b is the central limiting value for the anisotropy parameter). We also derive the set of sufficient conditions on the separable augmented density for the non-negativity of the distribution, which generalizes the condition derived for the generalized Cuddeford system by Ciotti & Morganti to arbitrary separable systems. This is applied for the case when the anisotropy is parameterized by a monotonic function of the radius of Baes & Van Hese. The resulting criteria are found based on the complete monotonicity of generalized Mittag-Leffler functions.
When is an axisymmetric potential separable?
J. An
Physics , 2013, DOI: 10.1093/mnras/stt1498
Abstract: An axially symmetric potential psi(R,z)=psi(r,theta) is completely separable if the ratio s:k is constant. Here r*s=d^2(r^2*psi)/dr/d(theta) and k=d^2(psi)/dR/dz. If beta=s/k, then the potential admits an integral of the form of I=(L^2+beta*v_z^2)/2+xi where xi is some function of positions determined by the potential psi. More generally, an axially symmetric potential respects the third axisymmetric integral of motion -- in addition to the classical integrals of the Hamiltonian and the axial component of the angular momentum -- if there exist three real constants a,b,c (not all simultaneously zero, a^2+b^2+c^2>0) such that a*s+b*h+c*k=0 where r*h=d^2(r*psi)/d(sigma)/d(tau) and (sigma,tau) is the parabolic coordinate in the meridional plane such that sigma^2=r+z and tau^2=r-z.
Flaws, Fallacies and Facts: Reviewing the Early History of the Lipid and Diet/Heart Hypotheses  [PDF]
J. Elliott
Food and Nutrition Sciences (FNS) , 2014, DOI: 10.4236/fns.2014.519201
Abstract: The lipid hypothesis of coronary heart disease proposes that a high total cholesterol level has a causative role in coronary heart disease (CHD), specifically in the development of atherosclerosis. It forms the basis for formulating target levels of serum cholesterol and hence the widespread use of statins for lowering cholesterol. An extension of the lipid hypothesis is the diet/heart hypothesis of coronary heart disease. This theory combines two ideas—that saturated fat raises cholesterol levels, and that a reduced saturated fat intake will lower cholesterol levels, thereby inhibiting the development of atherosclerosis and manifestations of CHD. Those who make diet recommendations or prescribe medication to reduce cholesterol may be unaware of the underpinning science. The original research behind these recommendations has given us “healthy heart” guidelines and preventive measures we assume to be true. While the lipid and diet/heart hypotheses are often presented as fact, they remain inadequately proven theories that have little agreement from experts. Historical perspectives can help us understand the basis of current-day beliefs. In the lipid hypothesis case, research from the 1950s and 60s was instrumental in its formation. This early work should not be considered irrelevant, outdated or obsolete because current recommendations from national heart associations in many countries continue to be shaped by these studies. This paper examines evidence used to formulate the lipid hypothesis and, subsequently, the diet/ heart hypothesis. By critically evaluating steps in the formation of the theory, inconsistencies, mistakes and alternate explanations become apparent and cast doubt on its validity.
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