An investigation on the mechanics of homogeneous expansion in gas-fluidized beds

The Richardson and Zaki (1954, Sedimentation and fluidization. Trans. Inst. Chem. Eng. 32, pp. 35–53.) equation has been used extensively to investigate the expansion profiles of homogeneous gas-fluidized beds. The experimental value of the parameter n appearing in the equation indicates how significantly interparticle forces affect the expansion of these beds, revealing the relative importance of these forces with respect to the fluid dynamic ones. In this work, we modeled the stable expansion of gas-fluidized beds of different diameter, accounting for enduring contacts among particles and wall effects. We solved the model numerically to obtain the bed expansion profiles, back-calculating from them the values of the parameter n. For all the cases considered, we observed that the values of n are higher than those obtained by purely fluid dynamic correlations, such as those advanced by Richardson and Zaki, and Rowe (1987, A convenient empirical equation for estimation of the Richardson and Zaki exponent. Chem. Eng. Sci. 42, pp. 2795.). This effect was more pronounced in beds of smaller diameter. To validate our model, we carried out fluidization and defluidization experiments, analyzing the results by means of the Richardson and Zaki equation. We obtained a reasonable agreement between numerical and experimental findings; this suggests that enduring contacts among particles, which are manifestations of cohesiveness, affect homogeneous bed expansion. This effect is amplified by wall friction

Nutrients and biological production in lakes

This paper is a review of studies on effects of nutrients on biological productivity and efforts made so far at restoration of nutrients in lakes. It is to provide an understanding of the basis scientific process accruing in lakes, therefore of prime importance in maintaining water quality standards for propagation of effective lake managemen

Democracy and Governance in Nigeria’s Fourth Republic

The symbiotic relationship between democracy and good governance is globally acclaimed. This is borne out of the belief that democracy premisedon the principle of the rule of law and constitutionalism is capable of ushering in good governance and societal development. It is equally believed that democracy conforms to the principle of justice, equity and fair-play as a democratic state is based on consent and popular participation. However, since the inception of the Fourth Republic in 1999, it is observed that the prolonged adventure of the military into Nigerian government and politics is such that has permeated the body politics to the effect that observance of basic democratic tenets seems difficult for those saddled with the political power and responsibilities. Thus the political class continues to dispose and demonstrate known military attributes and values in issues that are characteristically civil and democratic. Authoritarianism tendencies continue to shape the character of politics as reflective in limited regard for the constitution and the illiberal dispositions of the political elite and the civil society. Rather than producing good governance and developed the state, the above scenario has resulted in bad governance and has further pauperized the citizenry

Millennium Development Goals {MDGs} and the Yar'adua's Seven Point Agenda in Nigeria: Prospects and Challenges

One global identity today is glaring poverty. The intercontinental epidemichas its worse effects on the developing nations of the world, Africa andNigeria in particular. Indicators of this glaring poverty span through allhuman socio-political economic lives of the citizenry, from health toeducation, gender inequality and to environmental degradation. The United Nations woke up to this startling reality in September 8, 2000 in New York to adopt a millennium declaration to address this problem. This has hither to been adopted in Nigeria by the democratic government of Presidents Obasanjo and Yar'Adua. Yar'Adua in the wake of his administration declared a 7-point agenda to combact poverty and its attendant indicators head-long. This paper therefore observes that, though MDGs and its incorporated 7-points agenda of Yar'Adua seem to have the prospect and capability to address the problem of poverty in Nigeria, yet it lacks the in-built capacity toaddress poverty especially in this era of global economic meltdown. To this end the paper contends that some policies in the past failed to address similar problems due to lack of strong political will and corruption. Therefore, the paper examines some challenges confronting the attainment of MDGs and the Yar’Adua’s 7-point agenda in Nigeria. Finally, the paper identifies some policy suggestions towards realising the MDGs and the 7-point agenda. Content analysis is relied upon in the course of the research

Optical and infrared spectrophotometry of 18 Markarian galaxies

Slit spectra, spectrophotometric scans and infrared broad band observations are presented. Eight of the program galaxies can be classified as Seyfert galaxies. Arguments are given that thermal, nonthermal and stellar radiation components were present. One group of Seyfert galaxies was characterized both by the presence of a high density region of gas and by a continuum dominated by nonthermal radiation. The continua of the remaining program Seyferts, which did not have a high density region of gas, were dominated by thermal radiation from dust and a stellar continuum. Ten of the galaxies, which are not Seyfert galaxies, are shown to be examples of extragalactic H 2 regions

A Definitive Optical Detection of a Supercluster at z = 0.91

We present the results from a multi-band optical imaging program which has definitively confirmed the existence of a supercluster at z = 0.91. Two massive clusters of galaxies, CL1604+4304 at z = 0.897 and CL1604+4321 at z = 0.924, were originally observed in the high-redshift cluster survey of Oke, Postman & Lubin (1998). They are separated by 4300 km/s in radial velocity and 17 arcminutes on the plane of the sky. Their physical and redshift proximity suggested a promising supercluster candidate. Deep BRi imaging of the region between the two clusters indicates a large population of red galaxies. This population forms a tight, red sequence in the color--magnitude diagram at (R-i) = 1.4. The characteristic color is identical to that of the spectroscopically-confirmed early-type galaxies in the two member clusters. The red galaxies are spread throughout the 5 Mpc region between CL1604+4304 and CL1604+4321. Their spatial distribution delineates the entire large scale structure with high concentrations at the cluster centers. In addition, we detect a significant overdensity of red galaxies directly between CL1604+4304 and CL1604+4321 which is the signature of a third, rich cluster associated with this system. The strong sequence of red galaxies and their spatial distribution clearly indicate that we have discovered a supercluster at z = 0.91.Comment: Accepted for publication in Astrophysical Journal Letters. 13 pages, including 5 figure

The role of cellular stress in intrauterine growth restriction and postnatal dysmetabolism

Disruption of the in utero environment can have dire consequences on fetal growth and development. Intrauterine growth restriction (IUGR) is a pathological condition by which the fetus deviates from its expected growth trajectory, resulting in low birth weight and impaired organ function. The developmental origins of health and disease (DOHaD) postulates that IUGR has lifelong consequences on offspring well-being, as human studies have established an inverse relationship between birth weight and long-term metabolic health. While these trends are apparent in epidemiological data, animal studies have been essential in defining the molecular mechanisms that contribute to this relationship. One such mechanism is cellular stress, a prominent underlying cause of the metabolic syndrome. As such, this review considers the role of oxidative stress, mitochondrial dysfunction, endoplasmic reticulum (ER) stress, and inflammation in the pathogenesis of metabolic disease in IUGR offspring. In addition, we summarize how uncontrolled cellular stress can lead to programmed cell death within the metabolic organs of IUGR offspring