Biosorption of Cr(VI) by free and immobilized Pediastrum boryanum biomass: equilibrium, kinetic, and thermodynamic studies

15th International Symposium on Toxicity Assessment (ISTA) -- JUL 03-08, 2011 -- City Univ Hong Kong, Hong Kong, PEOPLES R CHINAWOS: 000306790200053PubMed ID: 22374187The biosorption of Cr(VI) from aqueous solution has been studied using free and immobilized Pediastrum boryanum cells in a batch system. The algal cells were immobilized in alginate and alginate-gelatin beads via entrapment, and their algal cell free counterparts were used as control systems during biosorption studies of Cr(VI). The changes in the functional groups of the biosorbents formulations were confirmed by Fourier transform infrared spectra. The effect of pH, equilibrium time, initial concentration of metal ions, and temperature on the biosorption of Cr(VI) ion was investigated. The maximum Cr(VI) biosorption capacities were found to be 17.3, 6.73, 14.0, 23.8, and 29.6 mg/g for the free algal cells, and alginate, alginate-gelatin, alginate-cells, and alginate-gelatin-cells at pH 2.0, which are corresponding to an initial Cr(VI) concentration of 400 mg/L. The biosorption of Cr(VI) on all the tested biosorbents (P. boryanum cells, alginate, alginate-gelatin, and alginate-cells, alginate-gelatin-cells) followed Langmuir adsorption isotherm model. The thermodynamic studies indicated that the biosorption process was spontaneous and endothermic in nature under studied conditions. For all the tested biosorbents, biosorption kinetic was best described by the pseudo-second-order model.PROCORE-France/Hong Kong Joint Res Scheme, Croucher Fdn, KC Wong Educ Fd

Morphological evaluation and clinical significance of the supracondylar process and supratrochlear foramen: an anatomic and radiological study

Background: In our literature review, we did not encounter any study examining the supracondylar process (SP) and the supratrochlear foramen (STF) with a three-dimensional (3D) reconstruction method. The present study aimed to evaluate SP and STF morphologically by employing the 3D reconstruction method and emphasize their clinical significance. Materials and methods: The research was carried out on dried human humeri of unknown sex and without pathological alterations. A total of 81 humeri (42 right, 39 left) were obtained from the Departments of Anatomy of Gazi University Faculty of Medicine and Lokman Hekim University Faculty of Medicine. The morphometric measurements of SP and STF were made with a digital vernier caliper. The computed tomography (CT) images acquired for radiological evaluation were analyzed with the 3D reconstruction method. Results: The narrower distal medullary canal widths of humeri with STF were found to be statistically significant. No statistically significant difference was found between the transverse diameters (TD), vertical diameters (VD), the distance of the medial edge to the medial epicondyle (ME), and the distance of the lateral edge to the lateral epicondyle (LE) of the supratrochlear foramen of the right and left humeri. Conclusions: The supracondylar process is often evaluated by mistake as a pathological condition of the bone, not as a normal anatomical variation. Knowing different shapes and dimensions, e.g., the TD and VD distance in which STF emerges, can assist in avoiding the misinterpretation of radiographs

Spatial rigid-multi-body systems with lubricated spherical clearance joints : modeling and simulation

The dynamic modeling and simulation of spatial rigid-multi-body systems with lubricated spherical joints is the main purpose of the present work. This issue is of paramount importance in the analysis and design of realistic multibody mechanical systems undergoing spatial motion. When the spherical clearance joint is modeled as dry contact; i.e., when there is no lubricant between the mechanical elements which constitute the joint, a body-to-body (typically metal-to-metal) contact takes place. The joint reaction forces in this case are evaluated through a Hertzian-based contact law. A hysteretic damping factor is included in the dry contact force model to account for the energy dissipation during the contact process. The presence of a fluid lubricant avoids the direct metal-to-metal contact. In this situation, the squeeze film action, due to the relative approaching motion between the mechanical joint elements, is considered utilizing the lubrication theory associated with the spherical bearings. In both cases, the intra-joint reaction forces are evaluated as functions of the geometrical, kinematical and physical characteristics of the spherical joint. These forces are then incorporated into a standard formulation of the system’s governing equations of motion as generalized external forces. A spatial four bar mechanism that includes a spherical clearance joint is considered here as example. The computational simulations are carried out with and without the fluid lubricant, and the results are compared with those obtained when the system is modeled with perfect joints only. From the general results it is observed that the system’s performance with lubricant effect presents fewer peaks in the kinematic and dynamic outputs, when compared with those from the dry contact joint model.Fundação para a Ciência e a Tecnologia (FCT

A parametric study on the dynamic response of planar multibody systems with multiple clearance joints

A general methodology for dynamic modeling and analysis of multibody systems with multiple clearance joints is presented and discussed in this paper. The joint components that constitute a real joint are modeled as colliding bodies, being their behavior influenced by geometric and physical properties of the contacting surfaces. A continuous contact force model, based on the elastic Hertz theory together with a dissipative term, is used to evaluate the intra-joint contact forces. Furthermore, the incorporation of the friction phenomenon, based on the classical Coulomb’s friction law, is also discussed. The suitable contact-impact force models are embedded into the dynamics of multibody systems methodologies. An elementary mechanical system is used to demonstrate the accuracy and efficiency of the presented approach, and to discuss the main assumptions and procedures adopted. Different test scenarios are considered with the purpose of performing a parametric study for quantifying the influence of the clearance size, input crank speed and number of clearance joints on the dynamic response of multibody systems with multiple clearance joints. Additionally, the total computation time consumed in each simulation is evaluated in order to test the computational accuracy and efficiency of the presented approach. From the main results obtained in this study, it can be drawn that clearance size and the operating conditions play a crucial role in predicting accurately the dynamic responses of multibody systems.Fundação para a Ciência e a Tecnologia (FCT

On the contact detection for contact-impact analysis in multibody systems

One of the most important and complex parts of the simulation of multibody systems with contact-impact involves the detection of the precise instant of impact. In general, the periods of contact are very small and, therefore, the selection of the time step for the integration of the time derivatives of the state variables plays a crucial role in the dynamics of multibody systems. The conservative approach is to use very small time steps throughout the analysis. However, this solution is not efficient from the computational view point. When variable time step integration algorithms are used and the pre-impact dynamics does not involve high-frequencies the integration algorithms may use larger time steps and the contact between two surfaces may start with initial penetrations that are artificially high. This fact leads either to a stall of the integration algorithm or to contact forces that are physically impossible which, in turn, lead to post-impact dynamics that is unrelated to the physical problem. The main purpose of this work is to present a general and comprehensive approach to automatically adjust the time step, in variable time step integration algorithms, in the vicinity of contact of multibody systems. The proposed methodology ensures that for any impact in a multibody system the time step of the integration is such that any initial penetration is below any prescribed threshold. In the case of the start of contact, and after a time step is complete, the numerical error control of the selected integration algorithm is forced to handle the physical criteria to accept/reject time steps in equal terms with the numerical error control that it normally uses. The main features of this approach are the simplicity of its computational implementation, its good computational efficiency and its ability to deal with the transitions between non contact and contact situations in multibody dynamics. A demonstration case provides the results that support the discussion and show the validity of the proposed methodology.Fundação para a Ciência e a Tecnologia (FCT

Effect of photosonication treatment on inactivation of total and coliform bacteria in milk

The combined effect of simultaneously applied acoustic energy and ultraviolet irradiation (UV-C), named photosonication, on the population reduction of total and coliform bacteria in raw milk was investigated. Photosonication was carried out at 100% (120 ?m; 240 W) amplitude of ultrasound accompanied by UV light of 13.2 W cm-2 while sonication was carried out at 100% amplitude without UV light. An ultrasonic processor (400 W and 24 kHz with a 22 mm diameter probe) and 3 ultraviolet lamps (4400 ?W cm-2 per lamp) were used. The exposure time was 15 min for all treatment, and samples were taken after 0, 3, 6, 9, 12 and 15 min. Thermal treatment (at 65 °C for 30 min) achieved a 3.29 log and 5.31 log-reduction for total and coliform bacteria, respectively. However, the reduction achieved was 4.79 log cfu mL-1 and 5.31 log cfu mL-1 for total and coliform bacteria, respectively, in photosonication while 1.31 log cfu mL-1 and 4.01 log cfu mL-1 for total and coliform bacteria, respectively in sonication. During photosonication, UV light contributed to an increase of lethality. © 2011 Elsevier Ltd

Long-term storage of a number of microorganism species using different cryoprotectants

This study aims to generate a microalgae culture collection, and ensure the long-term survival of this collection by prolonging the period when the isolated microalgae and other microorganism cultures can be preserved. The microalgae cultures included four microalgae species (Chlorella vulgaris Beyerinck [Beijerinck], Klebsormidium subtile (Kützing) Mikhailyuk, Glaser, Holzinger & Karsten, Microcoleus autumnalis (Gomont) Strunecky, Komárek & J.R. Johansen and Synechococcus bigranulatus Skuja), two bacteria species (Staphylococcus aureus and Escherichia coli) and two fungi species (Aspergillus Niger and Pénicillium sp.). The study applied a cryopreservation protocol at -80°C directly to each of the species. The cryoprotective agents used in the study were dimethyl sulfoxide (DMSO), glycerol and skimmed milk at a final concentration of 5% for the microalgae in addition to an application without any cryoprotectant at all. The cryoprotectant agents used for this procedure were 15% final glycerol concentration for the bacteria and 10% skimmed milk for the fungi. After six months, the strains of C. vulgaris (93%), S. bigranulatus (83%) and M autumnalis (80%) showed higher viability rates in glycerol, while the strain of K. subtile (93%) showed higher viability rates in skimmed milk. The recovery ratio of E. coli, S. aureus, A. Niger and Pénicillium sp. were found to be 5.10, 3.23, 1.98 and 2.67 log CFU/ml, respectively. © by PSP

Modeling and simulation of joint clearance effects on mechanisms having rigid and flexible links

In this study, kinematic and dynamic characteristics of a planar four-bar mechanism having joint clearance and link flexibility are investigated. Assuming that joint clearance as a virtual massless link, artificial clearances are developed at crank-coupler and coupler-follower joints. Contact model in joints with clearance is established using the nonlinear spring-damper model and the friction effect is considered using the Coulomb friction model. Then the simulation is implemented and the kinematic and dynamic characteristics of model mechanism are investigated. The computational methodology can predict the effects of clearance on planar mechanism having rigid and flexible links. The results are evaluated for the case of stationary phase, and naturally show that extreme values occur in output of the mechanism with clearances. Due primarily to the suspension effect of the flexible link, values of these peaks in the flexible mechanism decrease relative to that of the rigid mechanism. In addition, the flexibility has a significant effect on the vibration response of the mechanism with joint clearance

Uterine tumors resembling ovarian sex cord tumors: A case report and literature review

Uterine tumors with ovarian sex cord-like elements are a rarely observed type of uterine body tumor with unknown etiology, and are divided into two groups: Endometrial stromal tumors with sex cord-like elements (ESTSCLEs) and uterine tumors resembling ovarian sex cord tumors (UTROSCTs). While ESTSCLEs are commonly associated with metastasis and recurrence, there is limited data in the relevant literature concerning the behavior of UTROSCTs. However, UTROSCTs are typically benign in nature. Although case numbers are limited, extra-uterine or lymph node metastasis has been reported. Surgical approaches may be altered according to the patient's age and desire for future fertility. Hysterectomies with bilateral salpingo-oopherectomy or hysteroscopic tumor resection are reported to be safe surgical treatment options. However, in the current report, a case of UTROSCT initially misdiagnosed as adenosarcoma following hysteroscopic tumor resection is presented. Staging surgery revealed the precise diagnosis of the tumor using appropriate immunohistochemical evaluations, and led to the discovery of a secondary tumor focus in the myometrium, adjacent to the location of the previously excised tumor. Thus, hysteroscopic resection is questionable as a definitive surgical treatment in patients exhibiting UTROSCT. If hysteroscopic resection is the selected treatment, close follow-up with diagnostic imaging is recommended