Aissa Aissa - Academia.edu (original) (raw)

Papers by Aissa Aissa

Composites Science and Technology, 2002

Multi-walled carbon nanotube/epoxy resin composites have been fabricated. By choosing an over-age... more Multi-walled carbon nanotube/epoxy resin composites have been fabricated. By choosing an over-aged hardener, relatively soft and ductile matrix, a rubbery epoxy resin, has been obtained. This made possible to evaluate the effect of nanotube addition on the whole stress-strain curve up to high strain level. The mechanical and electrical properties of the composite with different weight percentages of nanotubes have been investigated. The Young's modulus and the yield strength have been doubled and quadrupled for composites with respectively 1 and 4 wt.% nanotubes, compared to the pure resin matrix samples. Conductivity measurements on the composite samples showed that the insulator-to-conductor transition took place for nanotube concentration between 0.5% and 1 wt.%. #

Background. Adiponectin, a newly discovered collagen-like protein of the collectin family exclusi... more Background. Adiponectin, a newly discovered collagen-like protein of the collectin family exclusively produced by adipocytes, possesses anti-inflammatory properties. Plasma adiponectin is associated with a decreased cardiovascular risk in non-renal patients, and is reduced in obesity and insulin-resistant states. Although reports show an increase in the adiponectin level in maintenance haemodialysis, peritoneal dialysis and end-stage renal disease, there is no documentation of adiponectin levels and regulation in the early stages of chronic kidney disease (CKD). Methods. We prospectively measured glomerular filtration rate (GFR) in 48 patients with CKD using inulin clearance. Fasting blood was drawn to determine insulin, leptin, adiponectin and C-reactive protein (CRP) levels. Body fat mass was calculated using skinfold thickness measurements. Results. The patients' mean GFR was 53.5±24.9 (SD) ml/min/1.73 m 2 . Adiponectin was in the normal range in men (9.8±2.9 mg/l) and women (16.6±5.0 mg/l) with CKD, being significantly higher in women than men (P<0.001). Serum leptin was above normal (10.4±10.7 mg/l), whereas serum insulin and CRP were within their normal ranges (3.5±3.3 mU/ml and 2.6±5.0 mg/l, respectively). In linear regression analysis, adiponectin was negatively correlated with GFR (P ¼ 0.02), fat mass (P ¼ 0.03) and body mass index (P ¼ 0.002), and strongly positively correlated with serum leptin (P ¼ 0.003). A positive relationship was also found between plasma adiponectin and the urinary albumin/creatinine ratio (P ¼ 0.007). No relationship was found between adiponectin and insulin or adiponectin and CRP. In multiple regression analysis, adiponectin was significantly positively correlated with leptin (P<0.0001), negatively with body mass index (P<0.0001) and only weakly with GFR (P ¼ 0.04).

Intensive Care Medicine, 1992

CPAP can be delivered by two methods: Demand valve (DV) and continuous flow (CF). It has been sho... more CPAP can be delivered by two methods: Demand valve (DV) and continuous flow (CF). It has been shown that the work of breathing (WOB) is greater with DV systems. The objective of this study was to determine the effects on WOB and lung mechanics of DV -CPAP and CPAP flow-by (FB) which is a CF system, in patients weaning from mechanical ventilation. We studied 14 intubated patients through 3 CPAP mode, applied in random order: 1) DV -CPAP, 2) FB using base flow of 10 L/min. (FB10) and 3) FB using base flow of 20L/min (FB20). The ventilator used was the Puritan-Bennett 7200a. Sensitivity of the FB was set at 1L/min., and during DV-CPAP sensitivity of DV was set at 0.5 cmH2O. The level of PEEP set on the ventilator was unchanged. Signals of airflow, airway, esophageal and gastric pressures were adquired and digitized via an A/D converter and were processed by an IBM 55SX computer in order to calculate inspiratory WOB (from Campbell's diagrams), Pdi (Pga-Peso), PEEP and autoPEEP, dynamic lung compliance (Cdyn) and breathing pattern. Differences between CPAP systems were analyzed by a two-way analysis of variance. Results (mean values + SEM) were as follows:

Kidney International, 2000

Fibrosis contributes to the progression of renal damcollagen III deposition in rat remnant kidney.

The performance of beamforming in dual-hop cooperative networks with fixed-gain relays is investi... more The performance of beamforming in dual-hop cooperative networks with fixed-gain relays is investigated. These kinds of relays offer low complexity and ease of deployment when compared with variable-gain relays. In our analysis, the source and destination nodes are equipped with multiple antennas, whereas the relay is assumed to be a single-antenna device. Closed-form expressions for the outage probability (OP), probability density function (PDF), moment generating function (MGF), and generalized moments of the end-to-end signal-to- noise ratio (SNR) are obtained. It is shown that when the same antenna configurations are considered at the source and destination sides, the power imbalance between the hops may be either beneficial or detrimental for the overall system performance. In addition, depending on whether the average SNR of the second hop is equal, lower, or higher than that of the first hop, an increase of the number of antennas may not necessarily result in a substantial improvement in performance.

IEEE Transactions on Wireless Communications, 2009

... IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS, VOL. 8, NO. 8, AUGUST 2009 End-to-End Performan... more ... IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS, VOL. 8, NO. 8, AUGUST 2009 End-to-End Performance of Dual-Hop Semi-Blind Relaying Systems with Partial Relay Selection Daniel Benevides da Costa, Member, IEEE, and Sonia Aıssa, Senior Member, IEEE ...

Comparative Biochemistry and Physiology C-toxicology & Pharmacology, 2001

The variations of acetylcholinesterase activity, considered to be a biochemical biomarker of orga... more The variations of acetylcholinesterase activity, considered to be a biochemical biomarker of organophosphorus and Ž . Ž carbamate compounds, was followed in Mediterranean clams Ruditapes decussatus and mussels Mytilus gallopro¨in-. Ž . cialis as a function of season and sampling sites in the lagoon of Bizerta Tunisia . Results show that acetylcholinesterase activity in clams collected from station A was the lowest and was so throughout the year. This low activity may be due to the input of non-treated waste waters in the lagoon. Heavy metal contamination has been reported in the sediments of this area, suggesting that acetylcholinesterase activity in clams may be inhibited by this type of pollution. Clams harvested from station F, a site adjacent to an agricultural area, were characterized by a decrease in acetylcholinesterase activity, especially after rain periods. Clams from station J presented the highest activity throughout the greater part of the year. This phenomenon may imply that this location is less affected by pollutants inhibiting AChE activity than the others. In the mussels from station C, located in the channel from the lagoon to the Ž . Mediterranean and submitted to pollutants urban wastes from Bizerta and hydrocarbons from the maritime traffic , acetylcholinesterase activities were lower than in those from station J. In conclusion, the variations in acetylcholinesterase activity observed between stations in both species may be the result of pollution and of the environmental conditions. ᮊ M. Romeo .

Intensive Care Medicine, 1992

IEEE Transactions on Communications, 2005

... For nonergodic fading channels, on the other hand, there is a nonzero proba-bility, named out... more ... For nonergodic fading channels, on the other hand, there is a nonzero proba-bility, named outage probability, that a desired transmission rate ... Accordingly, the outageprobability for TB is therefore given by (13) Page 3. 1094 ...

IEEE Transactions on Wireless Communications, 2009

In this paper, we investigate the end-to-end performance of dual-hop relaying systems with beamfo... more In this paper, we investigate the end-to-end performance of dual-hop relaying systems with beamforming over Nakagami-m fading channels. Our analysis considers semiblind (fixed-gain) relays with single antennas, and source and destination nodes equipped with multiple antennas. Closed-form expressions for the outage probability (OP), moment generating function (MGF), and generalized moments of the end-to-end signal-to-noise ratio (SNR) are derived. The proposed expressions apply to general operating scenarios with distinct Nakagamim fading parameters and average SNRs between the hops. The influence of the power imbalance, fading parameters, and antenna configurations on the overall system performance are analyzed and discussed through representative numerical examples. Furthermore, the exactness of our formulations is validated by means of Monte Carlo simulations.

Environmental Toxicology and Pharmacology, 2005

The aim of this study was to characterise biomarker responses in three-spined sticklebacks expose... more The aim of this study was to characterise biomarker responses in three-spined sticklebacks exposed to copper. For this purpose, adult sticklebacks were exposed for 3 weeks to copper sulphate at 0, 25, 100 and 200μgL(-1) as Cu. At days 4, 8, 12 and 21, several parameters were measured including liver, gonad and spleen somatic indexes, hepatic biomarkers (catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione (GSH), glutathione-S-transferase (GST) and 7-ethoxyresorufin-O-deethylase (EROD)) and hepatic copper and zinc concentrations. Copper induced a rapid and transient increase of antioxidant enzymes and a depletion of glutathione content during the first 8 days of exposure. Significant copper and zinc accumulation in fish liver were observed for the two higher exposure concentrations after 8 and 12 days, respectively. This study showed that copper induced an oxidative stress in fish liver before significant metal accumulation in the liver could be detected, suggesting the involvement of differential mechanisms in copper uptake and metabolism. Three-spined stickleback appears to be a sensitive model to study oxidative stress induced by metals.

Archives of Environmental Contamination and Toxicology, 2001

Three biomarkers (glutathione S-transferase [GST] activity, catalase [CAT] activity, and malonedi... more Three biomarkers (glutathione S-transferase [GST] activity, catalase [CAT] activity, and malonedialdehyde [MDA] levels) were measured in specimens of the mussel Mytilus galloprovincialis collected from two different stations (BC and MJ) in the lagoon of Bizerta (Tunisia). Animals were allowed to acclimate in the laboratory for some days. They were then exposed for 48 h to two concentrations of pp′DDE and two doses of mercury chloride. The acclimation period increased CAT activities and MDA levels in control mussels from both sites. GST activities were not modified during the acclimation period, whereas the sampling site of mussels appeared to exert a significant influence (higher values in control mussels from MJ than in those from BC). The treatment with both contaminants also increased GST activities of mussels from BC and not from MJ. It is hypothesized that animals from this last location are more exposed to the urban waste waster disposal, their biochemical response (GST activity) to pollutant exposure will be less marked. The treatment with pp′DDE or mercury did not show significant trend in CAT activities or MDA levels due to the variation of controls, and comparison of sites for mussels exposed to either pollutant therefore seems difficult. The acclimation period in the laboratory and the origin of mussels must be taken into consideration when studying the biochemical responses of mussels experimentally exposed to chemical pollutants.

IEEE Transactions on Wireless Communications, 2007

Abstract In this paper, we consider the scheduling problem in multiple-input multiple-output (MIM... more Abstract In this paper, we consider the scheduling problem in multiple-input multiple-output (MIMO) wireless networks. The main important characteristic of an optimal scheduler is to maximize throughput while servicing users in a fair manner. Herein, we formulate MIMO ...

Environmental Health Perspectives, 2004

Kidney International, 2002

Renal transplantation (Tx) is the treatment of choice pediatric compared to adult kidney donors.

Composites Science and Technology, 2002

Multi-walled carbon nanotube/epoxy resin composites have been fabricated. By choosing an over-age... more Multi-walled carbon nanotube/epoxy resin composites have been fabricated. By choosing an over-aged hardener, relatively soft and ductile matrix, a rubbery epoxy resin, has been obtained. This made possible to evaluate the effect of nanotube addition on the whole stress-strain curve up to high strain level. The mechanical and electrical properties of the composite with different weight percentages of nanotubes have been investigated. The Young's modulus and the yield strength have been doubled and quadrupled for composites with respectively 1 and 4 wt.% nanotubes, compared to the pure resin matrix samples. Conductivity measurements on the composite samples showed that the insulator-to-conductor transition took place for nanotube concentration between 0.5% and 1 wt.%. #

Background. Adiponectin, a newly discovered collagen-like protein of the collectin family exclusi... more Background. Adiponectin, a newly discovered collagen-like protein of the collectin family exclusively produced by adipocytes, possesses anti-inflammatory properties. Plasma adiponectin is associated with a decreased cardiovascular risk in non-renal patients, and is reduced in obesity and insulin-resistant states. Although reports show an increase in the adiponectin level in maintenance haemodialysis, peritoneal dialysis and end-stage renal disease, there is no documentation of adiponectin levels and regulation in the early stages of chronic kidney disease (CKD). Methods. We prospectively measured glomerular filtration rate (GFR) in 48 patients with CKD using inulin clearance. Fasting blood was drawn to determine insulin, leptin, adiponectin and C-reactive protein (CRP) levels. Body fat mass was calculated using skinfold thickness measurements. Results. The patients' mean GFR was 53.5±24.9 (SD) ml/min/1.73 m 2 . Adiponectin was in the normal range in men (9.8±2.9 mg/l) and women (16.6±5.0 mg/l) with CKD, being significantly higher in women than men (P<0.001). Serum leptin was above normal (10.4±10.7 mg/l), whereas serum insulin and CRP were within their normal ranges (3.5±3.3 mU/ml and 2.6±5.0 mg/l, respectively). In linear regression analysis, adiponectin was negatively correlated with GFR (P ¼ 0.02), fat mass (P ¼ 0.03) and body mass index (P ¼ 0.002), and strongly positively correlated with serum leptin (P ¼ 0.003). A positive relationship was also found between plasma adiponectin and the urinary albumin/creatinine ratio (P ¼ 0.007). No relationship was found between adiponectin and insulin or adiponectin and CRP. In multiple regression analysis, adiponectin was significantly positively correlated with leptin (P<0.0001), negatively with body mass index (P<0.0001) and only weakly with GFR (P ¼ 0.04).

Intensive Care Medicine, 1992

CPAP can be delivered by two methods: Demand valve (DV) and continuous flow (CF). It has been sho... more CPAP can be delivered by two methods: Demand valve (DV) and continuous flow (CF). It has been shown that the work of breathing (WOB) is greater with DV systems. The objective of this study was to determine the effects on WOB and lung mechanics of DV -CPAP and CPAP flow-by (FB) which is a CF system, in patients weaning from mechanical ventilation. We studied 14 intubated patients through 3 CPAP mode, applied in random order: 1) DV -CPAP, 2) FB using base flow of 10 L/min. (FB10) and 3) FB using base flow of 20L/min (FB20). The ventilator used was the Puritan-Bennett 7200a. Sensitivity of the FB was set at 1L/min., and during DV-CPAP sensitivity of DV was set at 0.5 cmH2O. The level of PEEP set on the ventilator was unchanged. Signals of airflow, airway, esophageal and gastric pressures were adquired and digitized via an A/D converter and were processed by an IBM 55SX computer in order to calculate inspiratory WOB (from Campbell's diagrams), Pdi (Pga-Peso), PEEP and autoPEEP, dynamic lung compliance (Cdyn) and breathing pattern. Differences between CPAP systems were analyzed by a two-way analysis of variance. Results (mean values + SEM) were as follows:

Kidney International, 2000

Fibrosis contributes to the progression of renal damcollagen III deposition in rat remnant kidney.

The performance of beamforming in dual-hop cooperative networks with fixed-gain relays is investi... more The performance of beamforming in dual-hop cooperative networks with fixed-gain relays is investigated. These kinds of relays offer low complexity and ease of deployment when compared with variable-gain relays. In our analysis, the source and destination nodes are equipped with multiple antennas, whereas the relay is assumed to be a single-antenna device. Closed-form expressions for the outage probability (OP), probability density function (PDF), moment generating function (MGF), and generalized moments of the end-to-end signal-to- noise ratio (SNR) are obtained. It is shown that when the same antenna configurations are considered at the source and destination sides, the power imbalance between the hops may be either beneficial or detrimental for the overall system performance. In addition, depending on whether the average SNR of the second hop is equal, lower, or higher than that of the first hop, an increase of the number of antennas may not necessarily result in a substantial improvement in performance.

IEEE Transactions on Wireless Communications, 2009

... IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS, VOL. 8, NO. 8, AUGUST 2009 End-to-End Performan... more ... IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS, VOL. 8, NO. 8, AUGUST 2009 End-to-End Performance of Dual-Hop Semi-Blind Relaying Systems with Partial Relay Selection Daniel Benevides da Costa, Member, IEEE, and Sonia Aıssa, Senior Member, IEEE ...

Comparative Biochemistry and Physiology C-toxicology & Pharmacology, 2001

The variations of acetylcholinesterase activity, considered to be a biochemical biomarker of orga... more The variations of acetylcholinesterase activity, considered to be a biochemical biomarker of organophosphorus and Ž . Ž carbamate compounds, was followed in Mediterranean clams Ruditapes decussatus and mussels Mytilus gallopro¨in-. Ž . cialis as a function of season and sampling sites in the lagoon of Bizerta Tunisia . Results show that acetylcholinesterase activity in clams collected from station A was the lowest and was so throughout the year. This low activity may be due to the input of non-treated waste waters in the lagoon. Heavy metal contamination has been reported in the sediments of this area, suggesting that acetylcholinesterase activity in clams may be inhibited by this type of pollution. Clams harvested from station F, a site adjacent to an agricultural area, were characterized by a decrease in acetylcholinesterase activity, especially after rain periods. Clams from station J presented the highest activity throughout the greater part of the year. This phenomenon may imply that this location is less affected by pollutants inhibiting AChE activity than the others. In the mussels from station C, located in the channel from the lagoon to the Ž . Mediterranean and submitted to pollutants urban wastes from Bizerta and hydrocarbons from the maritime traffic , acetylcholinesterase activities were lower than in those from station J. In conclusion, the variations in acetylcholinesterase activity observed between stations in both species may be the result of pollution and of the environmental conditions. ᮊ M. Romeo .

Intensive Care Medicine, 1992

IEEE Transactions on Communications, 2005

... For nonergodic fading channels, on the other hand, there is a nonzero proba-bility, named out... more ... For nonergodic fading channels, on the other hand, there is a nonzero proba-bility, named outage probability, that a desired transmission rate ... Accordingly, the outageprobability for TB is therefore given by (13) Page 3. 1094 ...

IEEE Transactions on Wireless Communications, 2009

In this paper, we investigate the end-to-end performance of dual-hop relaying systems with beamfo... more In this paper, we investigate the end-to-end performance of dual-hop relaying systems with beamforming over Nakagami-m fading channels. Our analysis considers semiblind (fixed-gain) relays with single antennas, and source and destination nodes equipped with multiple antennas. Closed-form expressions for the outage probability (OP), moment generating function (MGF), and generalized moments of the end-to-end signal-to-noise ratio (SNR) are derived. The proposed expressions apply to general operating scenarios with distinct Nakagamim fading parameters and average SNRs between the hops. The influence of the power imbalance, fading parameters, and antenna configurations on the overall system performance are analyzed and discussed through representative numerical examples. Furthermore, the exactness of our formulations is validated by means of Monte Carlo simulations.

Environmental Toxicology and Pharmacology, 2005

The aim of this study was to characterise biomarker responses in three-spined sticklebacks expose... more The aim of this study was to characterise biomarker responses in three-spined sticklebacks exposed to copper. For this purpose, adult sticklebacks were exposed for 3 weeks to copper sulphate at 0, 25, 100 and 200μgL(-1) as Cu. At days 4, 8, 12 and 21, several parameters were measured including liver, gonad and spleen somatic indexes, hepatic biomarkers (catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione (GSH), glutathione-S-transferase (GST) and 7-ethoxyresorufin-O-deethylase (EROD)) and hepatic copper and zinc concentrations. Copper induced a rapid and transient increase of antioxidant enzymes and a depletion of glutathione content during the first 8 days of exposure. Significant copper and zinc accumulation in fish liver were observed for the two higher exposure concentrations after 8 and 12 days, respectively. This study showed that copper induced an oxidative stress in fish liver before significant metal accumulation in the liver could be detected, suggesting the involvement of differential mechanisms in copper uptake and metabolism. Three-spined stickleback appears to be a sensitive model to study oxidative stress induced by metals.

Archives of Environmental Contamination and Toxicology, 2001

Three biomarkers (glutathione S-transferase [GST] activity, catalase [CAT] activity, and malonedi... more Three biomarkers (glutathione S-transferase [GST] activity, catalase [CAT] activity, and malonedialdehyde [MDA] levels) were measured in specimens of the mussel Mytilus galloprovincialis collected from two different stations (BC and MJ) in the lagoon of Bizerta (Tunisia). Animals were allowed to acclimate in the laboratory for some days. They were then exposed for 48 h to two concentrations of pp′DDE and two doses of mercury chloride. The acclimation period increased CAT activities and MDA levels in control mussels from both sites. GST activities were not modified during the acclimation period, whereas the sampling site of mussels appeared to exert a significant influence (higher values in control mussels from MJ than in those from BC). The treatment with both contaminants also increased GST activities of mussels from BC and not from MJ. It is hypothesized that animals from this last location are more exposed to the urban waste waster disposal, their biochemical response (GST activity) to pollutant exposure will be less marked. The treatment with pp′DDE or mercury did not show significant trend in CAT activities or MDA levels due to the variation of controls, and comparison of sites for mussels exposed to either pollutant therefore seems difficult. The acclimation period in the laboratory and the origin of mussels must be taken into consideration when studying the biochemical responses of mussels experimentally exposed to chemical pollutants.

IEEE Transactions on Wireless Communications, 2007

Abstract In this paper, we consider the scheduling problem in multiple-input multiple-output (MIM... more Abstract In this paper, we consider the scheduling problem in multiple-input multiple-output (MIMO) wireless networks. The main important characteristic of an optimal scheduler is to maximize throughput while servicing users in a fair manner. Herein, we formulate MIMO ...

Environmental Health Perspectives, 2004

Kidney International, 2002

Renal transplantation (Tx) is the treatment of choice pediatric compared to adult kidney donors.