Robocasting of advanced ceramics: ink optimization and protocol to predict the printing parameters - A review

Direct-Ink-Writing (or robocasting) is a subset of extrusion-based additive manufacturing techniques that has grown significantly in recent years to design simple to complex ceramic structures. Robocasting, relies on the use of high-concentration powder pastes, also known as inks. A successful optimization of ink rheology and formulation constitutes the major key factor to ensure printability for the fabrication of self-supporting ceramic structures with a very precise dimensional resolution. However, to date achieving a real balance between a comprehensive optimization of ink rheology and the determination of a relevant protocol to predict the printing parameters for a given ink is still relatively scarce and has been not yet standardized in the literature. The current review reports, in its first part, a detailed survey of recent studies on how ink constituents and composition affect the direct-ink-writing of ceramic parts, taking into account innovative ceramic-based-inks formulations and processing techniques. Precisely, the review elaborates the major factors influencing on ink rheology and printability, specifically binder type, particle physical features (size, morphology and density) and ceramic feedstock content. In the second part, this review suggests a standardized guideline to effectively adapt a suitable setting of the printing parameters, such as printing speed and pressure, printing substrate, strut spacing, layer height, nozzle diameter in function of ink intrinsic rheology

New insights on the relative sea level change during Holocene along the coasts of Tunisia and western Libya from archaeological and geomorphological markers

New data of sea level changes for the Mediterranean region along the coasts of northern Africa are presented. Data are inferred from archaeological sites of Punic-Roman age located along the coast of Tunisia, between Tunis and Jerba island and along the western coast of Libya, between Sabratha and Leptis Magna. Data are based on precise measures of presently submerged archaeological markers that are good indicators of past sea-level elevation. Nineteen selected archaeological sites were studied in Tunisia and four in Libya, all aged between w2.0 and w1.5 ka BP. The functional elevations of significant archaeological markers were measured with respect to the sea level at the time of measurements, applying corrections for tide and atmospheric pressure values. The functional elevations of specific architectural parts of the sites were interpreted, related to sea level at the time of their construction providing data on the relative changes between land and sea. Observations were compared against sea level change predictions derived from the glacio-hydro-isostatic model associated with the Last Glacial cycle. The results indicate that local relative sea level change along the coast of Tunisia and Libya, has increased 0.2 O 0.5 m since the last w2 ka. Besides minor vertical tectonic movements of the land, the observed changes are produced by eustatic and glacio-hydro-isostatic variations acting in the Mediterranean basin since the end of the last glacial maximum

Organisation et fonctionnement d’un écosystème côtier du Maroc : la lagune de Khnifiss

La lagune de Khnifiss, située au sud du Maroc, est une réserve biologique d’intérêt mondial pour l’avifaune. Des études pluridisciplinaires portant sur la physico-chimie des eaux, la biologie, la sédimentologie et les courants ont été réalisées par l’INRH dans la lagune en septembre 1998 et février 2001. Les résultats du courant obtenus montrent que la circulation des eaux à l’intérieur de la lagune est gérée par un courant alternatif et bidirectionnel : les courants du jusant sont plus importants que ceux du flot et varient également en fonction du rythme de la marée vive-eau/morte-eau. Ce mode de circulation des eaux attribue à la lagune une richesse en éléments azotés et phosphatés, surtout en période de vive-eau. La biomasse chlorophyllienne, assez importante dans la lagune, est causée par la richesse du milieu en éléments nutritifs et le phénomène d’upwelling qui se manifeste en été et au printemps dans la zone sud du Maroc. Ces études ont montré que la lagune de Khnifiss est un milieu propice à la conchyliculture. Néanmoins, l’installation de tout projet aquacole dans le site devra tenir compte de sa capacité trophique et de son équilibre écologique.The Moroccan coastal marine area has several zones that are targets for exploitation but must simultaneously be protected. Lagoons are considered to be among the most productive natural systems in the world, but they are also vulnerable systems due to natural and human constraints. Lagoons can also be a target of economic expansion. This is why an understanding about the state of these ecosystems is important in order to proceed with rational use of the resource. The Khnifiss lagoon, situated on the South Atlantic coast of Morocco, is a potential site for aquaculture and tourism if planned with an ecological awareness. The large surface area and high biological production for the avifauna qualify it to be among the four protected sites by the RAMSAR convention for humid zone conservation (lagoons of Khnifiss and Moulay Bousselham, lakes of Sidi Boughaba and Afennourir). The objective of this work was to complete previous studies and to estimate the nutritive richness of the Khnifiss lagoon. To understand the spatio-temporal variability in the water currents, and the physico-chemical and biological and characteristics of this lagoon, two surveys were organized in September 1998 and February 2001.The Khnifiss lagoon (20 km long and 65 km2 surface area) is situated between Tantan and Tarfaya (28°02'54'' N, 12°13'66'' W). It opens up into the Atlantic ocean by a narrow inlet called ''Foum Agouitir'', about 100 m wide. The lagoon continues upstream beyond a salt marsh, called "Sebkha Tazra". Physical, chemical and biological variables were monitored: temperature and salinity; dissolved oxygen, nitrates and phosphates; chlorophyll a. The current (direction and intensity) and the sediment were also studied. Samples were collected four times from the surface and bottom waters during spring tide (ST), neap tide (NT), low tide (LT) and high tide (HT) during two seasons (September 1998 and February 2001). Seven hydrological stations were sampled, representing the lagoon system and one reference station in a neighbouring zone (Hréf), which represents the marine zone of the lagoon. Temperature and salinity were measured with a multi-sensor probe. The chemical analyses were carried out according to methods suggested by AMINOT & CHAUSSEPIED (1983). Thirty (30) sediment samples were also collected. Currents were measured at two fixed points by two current-meters.Based on the hydrological characteristics of the lagoon, especially temperature, salinity, water circulation and the nature of sediment, three zones were identified :1. Zone I (downstream from the lagoon) was dominated by the ocean’s influence and included the Hréf, H1 and H2 stations. Maximum depths varied from 2.5 to 6.6 m, depending on the tide and location. The concentrations of the different hydrological parameters were controlled by the plug effect of the oceanic environment. The most important current in the lagoon was recorded in this zone in the spring tide (ST: 110 cm.s-1). The sediment was coarse and important water - sediment exchange was caused by the strong current recorded in this zone.2. Zone II (middle of the lagoon) was a transition zone with an intermediate oceanic influence. It was situated between the H3 and H5 stations. The size of the inlet and the important exchanges governed by currents caused by strong tides resulted in concentrations of the various parameters being similar to those in Zone I. Depths varied from 2.64 to 8.7 m. Waters were more saline during the LT and NT periods (36-41 practical salinity unit, or psu). The current decreased relative to that is zone I (56 cm.s-1 in September 1998 and 78 cm.s-1 in February 2001). In this zone the current moved preferentially towards the right strand at high tide and toward the left strand at low tide.3. Zone III (upstream in the lagoon) covered a different biotope compared to the first two zones. The waters were less deep (2.64 to 5.3 m) and included the stations H6, H7 and the upper part of the lagoon. This zone was characterized by a very low oceanic influence. Water temperature and salinity were higher, 24-26°C and 41-44 psu respectively, during the LT and NT periods.On the basis of the hydrological zonation, the conjunction of the climate descriptors (moderate wind, rare precipitation, absence of storms, moderate air temperature) of the lagoon and the strong hydrodynamic influence in the lagoon suggest that the Knifiss lagoon is a relatively unconfined ecosystem. The hydrodynamics of this lagoon permit a fast water renewal rate and insure a good environmental quality. In addition, studies carried out on the healthiness of this lagoon demonstrated not only a healthy environment, but also healthy shellfish. This diagnosis seemed to be related to the geographical location and important rates of water exchange. However, the absence of continental freshwater sources leads to an important increase in salinity and temperature at the level of the upstream zone (zone III). Zone III therefore cannot be considered for shellfish breeding.On the basis of the biological zones: With respect to the bathymetry of the lagoon (depths varied from 2.5 to 8.7 m), shellfish, in contrast to fish, require less water depth. Therefore, it is sufficient to search for a less turbulent zone, which offers sufficient planktonic food for the shellfish growth. In the Khnifiss lagoon, the taxonomy of the phytoplankton has not been yet studied. However, BENNOUNA (1999) demonstrated that the phytoplankton community was dominated by dinoflagellates and diatoms in the Oualidia and Sidi Moussa lagoons. RHARBI (2000) found that picophytoplankton were the principal breeding food source of oysters and clams in Oualidia lagoon. The source of shellfish for breeding is located in the neighbouring upwelling marine waters. Development projects planned for the lagoon must include an awareness programme for fishermen about the role that moderate and responsible shellfish breeding programs can play in the preservation and reconstitution of the marine resource as well as in the improvement of their incomes

Kyste neurentérique intra dural extra médullaire: à propos d’un cas

Le kyste neurentérique (KNE) est une malformation congénitale rare du système nerveux central (SNC) entrant dans le cadre des notochordodysraphies. Nous rapportons un nouveau cas de KNE de localisation intra durale extra médullaire chez un patient de 16 ans, admis dans un tableau de compression médullaire cervicale haut évoluant depuis 4 mois. L’imagerie a objectivé une lésion kystique pré médullaire en regardde C1-C2-C3. Le patient a bénéficié d’une évacuation kystique et l’histologie avait conclu à un kyste neurentérique. L’évolution était marquée par le décès du patient par des complications neurovégétatives graves. Malgré sa bénignité histologique, le kyste neurentérique de localisation cervicale haute peut se compliquer de troubles neurovégétatifs parfois imprévisibles pouvant aboutir à une évolution dramatique

Low-temperature rate constants for rotational excitation and de-excitation of C3 (X 1∑g +) by collisions with He (1S)

The low-temperature rotational (de-) excitation of C3 (X 1∑g 1) by collisions with He (1S) is studied using an ab initio potential energy surface (PES). This PES has been calculated using the single- and double-excitation coupled-cluster approach with noniterative perturbational treatment of triple excitations [CCSD(T)] and the augmented correlation-consistent triple-ζ basis set (aug-cc-pVTZ) with bond functions. This PES is then incorporated in full close-coupling quantum scattering calculations for collision energies between 0.1 and 50 cm -1 in order to deduce the rate constants for rotational levels of C3 up to j = 10, covering the temperature range 5-15 K. © 2008. The American Astronomical Society. All rights reserved.The Agencia Española de Cooperación Internacional (project A/8083/07, CSIC-Université Tunis El Manar) and the Spanish Ministerio de Educación y Ciencia (project AYA 2005-00702) are thanked for financial supportPeer Reviewe

Cytokine and immunoglobulin production by PWM-stimulated peripheral and tumor-infiltrating lymphocytes of undifferentiated nasopharyngeal carcinoma (NPC) patients

BACKGROUND: Undifferentiated Nasopharyngeal Carcinoma (NPC) patients show a characteristic pattern of antibody responses to the Epstein-Barr virus (EBV) which is regularly associated with this tumor. However, no EBV-specific cytotoxic activity is detectable by the standard chromium-release assay at both peripheral and intratumoral levels. The mechanisms underlying this discrepancy between the humoral and cellular immune responses in NPC are still unknown, but might be related to an imbalance in immunoregulatory interleukin production. In this report, we investigated the ability of peripheral (PBL) and tumor- infiltrating (TIL) lymphocytes of undifferentiated NPC patients to produce in vitro three interleukins (IL-2, IL-6, IL-10) and three immunoglobulin isotypes (IgM, IgG, IgA). METHODS: Lymphocytes from 17 patients and 17 controls were cultured in the presence of Pokeweed mitogen (PWM) for 12 days and their culture supernatants were tested for interleukins and immunoglobulins by specific enzyme-linked immunosorbent assays (ELISA). Data were analysed using Student's t-test and probability values below 5% were considered significant. RESULTS: The data obtained indicated that TIL of NPC patients produced significantly more IL-2 (p = 0,0002), IL-10 (p = 0,020), IgM (p= 0,0003) and IgG (p < 0,0001) than their PBL. On the other hand, patients PBL produced significantly higher levels of IL-2 (p = 0,022), IL-10 (p = 0,016) and IgM (p = 0,004) than those of controls. No significant differences for IL-6 and IgA were observed. CONCLUSION: Taken together, our data reinforce the possibility of an imbalance in immunoregulatory interleukin production in NPC patients. An increased ability to produce cytokines such as IL-10 may underlie the discrepancy between humoral and cellular immune responses characteristic of NPC

Visceral leishmaniasis in 26 HIV-negative adults

<p>Abstract</p> <p>Background</p> <p>Visceral leishmaniasis is a notifiable parasitic disease that had increased in incidence in our region on the past few years. It is common in children. In adults, it occurs more on a background of immunodeficiency, and frequently with incomplete clinical manifestations, making the diagnosis complicated.</p> <p>Findings</p> <p>The aim of our study is to reveal different features of visceral leishmaniasis in adults, through the analysis of its epidemiological, clinical and biological parameters, in a group of 26 patients. No one was infected with HIV or under immunosuppressive therapy Clinical presentation was generally conservative, but there was few differences in adults compared to children, concerning both the clinical symptoms and the laboratory parameters. Diagnosis was provided by direct examination of bone marrow smears in 24 cases (sensitivity 92%), and anti-leishmanial serology in the others.</p> <p>Conclusion</p> <p>We should think to the diagnosis of VL even if the patient is not known immunocompromised, and even if the clinical is incomplete, to avoid a delay of care which can lead to serious complications.</p