299 research outputs found
Incurred environmental risks and potential contamination sources in an abandoned mine site
The mineralogical characterization of Fedj Lahdoum mine wastes measured by X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) showed the presence of the following sulfide minerals: galena (PbS), sphalerite (ZnS), pyrite (FeS2), cerussite (PbCO3) and smithsonite (ZnCO3). The wastes were stored in tailing ponds. The results showed that the concentration of metals from tailings were up to 10 460 mg.kg-1 for total Zn, 2 100 mg.kg-1 for total Pb and 62.08 mg.kg-1 for total Cd. The tailings have presented a fine unconsolidated texture that accelerated the dispersion of the particles rich in heavy metals. Geochemical analysis of soil has revealed high total contents of Pb, Zn and Cd, respectively: 3 646, 3 236 and 17 mg.kg-1. Chemical analysis of cultivated and wild plants species inside the district contain high grades in heavy metals: 708.56 mg Zn. kg-1; 16.24 mg Pb.kg-1 (Thymus vulgaris (L)); 500.44 mg Zn. kg-1, 12.44 mg Pb. kg-1 (Laurus nobilis (L)); 128.33 mg Zn. kg-1 and 22.53 mg Pb.kg-1 (Ficus (L)) and 106.73 mgZn.kg-1 (pimento). The high levels detected in soil and plants have exceeded the Tunisian and Canadian standards. These results showed that the abandoned site was contaminated by the presence of tailing dumps which were exposed to significant water and/or wind erosion. To solve this problem, we proposed an environmental desulphurization by froth flotation.Keywords: Heavy metals, mine tailings, abandoned mining-district, plant contamination
Structure of relative genus fields of cubic Kummer extensions
Let , where is a cube free positive
integer, be the cyclotomic field containing a primitive
cube root of unity , the conductor of the abelian extension ,
and be the relative genus field of the Kummer extension with
Galois group . The aim of the present work is to
find out all positive integers and conductors such that
.
This allows us to give rise, in our next paper [2], to new phenomena concerning
the chain of \textit{lattice minima} in
the underlying pure cubic subfield of .Comment: 17 pages, 3 figures, 3 table
Bilateral redundancy gain and callosal integrity in a man with callosal lipoma: a diffusion-tensor imaging study
We investigated whether abnormalities in the structural organisation of the corpus callosum in the presence of curvilinear lipoma are associated with increased facilitation of response time to bilateral stimuli, an effect known as the redundancy gain. A patient (A.J.) with a curvilinear lipoma of the corpus callosum, his genetically-identical twin, and age-matched control participants made speeded responses to luminant stimuli. Structural organisation of callosal regions was assessed with diffusion-tensor imaging. A.J. was found to have reduced structural integrity in the splenium of the corpus callosum and produced a large redundancy gain suggestive of neural summation
The role of the dominant versus the non-dominant hemisphere: an fMRI study of Aphasia recovery following stroke
Background: Speech production is one of the most frequently affected cognitive functions following stroke; however, the neural mechanisms underlying the recovery of speech function are still incompletely understood.
Aims: The current study aims to address the differential contributions of the dominant and non-dominant hemispheres in recovery from aphasia following stroke by comparing data from four stroke patients and 12 control participants to assess the patterns of activation during speech production tasks during functional magnetic resonance imaging (fMRI) scanning.
Methods & Procedures: Four chronic stroke patients (three left-hemisphere lesion and one right-hemisphere lesion) diagnosed with Broca’s aphasia at the acute phase, but now recovered to near normal speech ability, were tested on speech production tasks (phonemic fluency, categorical fluency and picture naming) whilst undergoing fMRI. These patients were compared with 12 healthy controls undergoing the same procedure.
Outcomes & Results: Individual subject analysis showed activation peaks in perilesional areas in three out of four patients. This included one patient with right-hemisphere lesion, who also showed predominant perilesional activation. Group analysis of control participants showed predominately left-hemisphere activation, but not exclusively so. Laterality indexes were calculated and showed predominant left-hemisphere lateralisation in the control group (LI = 0.4). Three out of the four patients showed speech lateralised to the same hemisphere as their lesion and the fourth patient showed speech lateralised to the opposite hemisphere to their lesion. Different speech production tasks resulted in varying lateralisation indices (LIs) within participants.
Conclusions: The data suggest that perilesional areas support recovery of speech in the chronic phase post-stroke regardless of the site of the lesion. The study has implications for the understanding of functional recovery as well as for the paradigms used in fMRI to localise speech production areas. Specifically, a variety of speech tasks are required to elicit activation that is representative of the range of cortical involvement in speech in healthy adults and that also allows for accurate reporting of the extent of recovery experienced in patients
Bilateral redundancy gain and callosal integrity in a man with callosal lipoma: a diffusion-tensor imaging study
We investigated whether abnormalities in the structural organisation of the corpus callosum in the presence of curvilinear lipoma are associated with increased facilitation of response time to bilateral stimuli, an effect known as the redundancy gain. A patient (A.J.) with a curvilinear lipoma of the corpus callosum, his genetically-identical twin, and age-matched control participants made speeded responses to luminant stimuli. Structural organisation of callosal regions was assessed with diffusion-tensor imaging. A.J. was found to have reduced structural integrity in the splenium of the corpus callosum and produced a large redundancy gain suggestive of neural summation
Analyticity of The Ground State Energy For Massless Nelson Models
We show that the ground state energy of the translationally invariant Nelson
model, describing a particle coupled to a relativistic field of massless
bosons, is an analytic function of the coupling constant and the total
momentum. We derive an explicit expression for the ground state energy which is
used to determine the effective mass.Comment: 33 pages, 1 figure, added a section on the calculation of the
effective mas
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