Vacuum Drying of Common Date Pulp Cubes

Drying ability of date (Phoenix dactylifera L.) pulp cubes from three Algerian common varieties (Mech-Degla, Degla-Beida, and Frezza) were investigated. Drying process was carried out under partial vacuum (200 mbar) at 60, 80, and 100°C. Compared to the Newton model, the Henderson and Pabis model better described drying kinetic of Mech-Degla and Frezza pulps at 60 and 80°C with a mean relative error (MRE) not higher than 6.07%. The same model fits experimental data at 60°C for Degla-Beida (R ² = 0.988; MRE = 6.07) as well as at 100°C for only Mech-Degla (R ² > 0.98, MRE = 8.61%).     

Structure/rheological properties relations of crosslinked potato starch suspensions

Some rheological properties of aqueous suspensions of crosslinked hydroxypropylated potato starches were investigated. The crosslinking was performed at a temperature above the gelatinization temperature and the degree of crosslinking varied between 0.05 and 0.75% wt. The samples were characterized by the swelling power Q and the average particle size D and observed by light microscopy and low‐temperature SEM. The swelling power decreases with the extent of crosslinking, whereas the average particle size increases. From these observations, the starch samples can be described as suspensions of deformable particles suspended in a continuous suspending medium constituted of polymer chains plus water. The rheological properties allow us to define different concentration regimes depending on the close packing of swollen particles at a concentration C*, which is close to 1/Q. In dilute conditions, that is, for C < C*, the viscosity is little influenced by the degree of crosslinking and, hence, by the particle size. Two domains can be defined: a “true dilute” one for C < 0.6C* and a semidilute one for C > 0.6C*, in which the viscosity rapidly increases with the concentration. Moreover, an apparent yield stress and elastic properties are observed in the concentrated regime, for C > C*. Two domains can be also defined: a first one for C < 2C*, in which the rheological characteristics sharply increase with the concentration, and a second one, a quasi‐plateau domain, for C > 2C*. The variations of these rheological properties suggest that the rigidity of the swollen particles can be considered, contrary to the viscosity in the true dilute regime. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2480–2489, 2001     

Acrylic three‐dimensional networks. II. Behavior of different acrylic ion exchangers in the retention and elution processes of some metal cations

The retention process of the Cu(II) and Ni(II) cations from CuSO₄ and NiSO₄ aqueous solutions by eight acrylic ion exchangers was studied. Also, the elution process of these cations with 0.5 mol · L⁻¹ HCl solution was analyzed. The quantitative retention and elution as well as the development aspects of the two processes were observed by the column method. Seven ion exchangers contained weak base, weak acid, and amphoteric functional groups, these being known as chelating agents. Also, an ion exchanger with carboxylic groups, as a model, was taken in this study. The experiments show that the ion exchangers can be divided in three types as follows: (a) bad chelating agents; (b) chelating ion exchangers with the limited efficiency; (c) ion exchangers with good chelating properties and a high application efficiency; especially, the ion exchanger with hydroxamic functional groups is considered in this class. Also, the experimental data prove that, both for Cu(II) and Ni(II) cations, the volume of the purified effluent is higher than the HCl volume needs for their complete elution. This fact means concentration of the metal cations in the liquid phase. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1387–1394, 1999     

Neoadjuvant chemotherapy response evaluation in breast cancer based on mammogram registration and tumor segmentation

The standard approach for assessing the response of breast tumors to neoadjuvant chemotherapy is to monitor gross changes in tumor size as measured by physical exam and/or conventional imaging such as mammography. However, the deformable nature of the breast and variation in the imaging procedure, make it difficult to match the shape of breasts between serials of temporal mammograms, particularly when the tumor is shrinking due to the treatment. In this paper we propose a method for assessing residual tumor size following neoadjuvant chemotherapy by analyzing changes between pre-treatment and post-treatment mammograms. Our method consists of three steps: (1) pre-treatment and post-treatment mammograms were first registered in order to circumvent the problem of patient repositioning and breast deformation. (2) Tumors at corresponding locations were segmented using region growing segmentation, (3) and based on changes in tumor sizes the response rate is quantified. The proposed method has been tested on 6 breast cancer patients undergoing neoadjuvant chemotherapy, and the experimental results demonstrate that our approach may improve the ability of mammography to evaluate breast tumor response.     

Mixed Micellization Properties of Nonionic Fluorocarbon/Cationic Hydrocarbon Surfactants

The physico-chemical properties of mixed surfactant aqueous solutions at various proportions of dodecyltrimethyl ammonium bromide DTAB and undecafluoro n-pentyl decaoxyethylene ether C5F11EO10 have been investigated at 25 °C using surface tension and conductivity measurements. The critical micelle concentration and superficial minimum tension have been experimentally estimated for different DTAB molar fractions. The micellar composition and mutual interaction parameters have been deduced on the basis the theoretical treatments proposed by Clint, Rubingh, and Motomura. The results show a significant synergism effect at about equimolarity of DTAB/C5F11EO10 system probably due to the efficient electrostatic self-repulsion reduction between DTAB cationic head groups related to the presence of the nonionic surfactant in the mixed micelles.     

Chymotrypsin from the hepatopancreas of cuttlefish (Sepia officinalis) with high activity in the hydrolysis of long chain peptide substrates: Purification and biochemical characterisation

Chymotrypsin from the hepatopancreas of cuttlefish (Sepia officinalis) was purified to homogeneity, with a 120-fold increase in specific activity and 23% recovery. The molecular weight of the purified chymotrypsin was estimated to be 28 kDa by sodium dodecyl sulphate–polyacrylamide gel electrophoresis. The optimum pH and temperature for the chymotrypsin activity were pH 8.5 and 55 °C, respectively, using succinyl-l-ala-ala-pro-l-phenylalanine-p-nitroanilide (SAAPFpNA) as a substrate. The enzyme was extremely stable in the pH range of 7.0–10.0 and highly stable up to 50 °C after 1 h incubation. This proteinase was strongly inhibited by chymostatin, soybean trypsin inhibitor, diisopropylfluorophosphate and phenylmethylsulfonyl fluoride, but was not inhibited by tosyl-l-phenylalanine chloromethyl ketone, N-carbobenzoxy-phenylalanine chloromethyl ketone or N_α-tosyl-l-lysine chloromethyl ketone. The enzyme hydrolysed long chymotrypsin peptide substrates SAAPFpNA, SAAPLpNA and ZAALpNA and did not hydrolyse short chymotrypsin substrates. Kinetic parameters of the enzymatic reaction demonstrated that the best substrate was SAAPFpNA, with k_cat 18 s^?1 and K_m 22 μM. However, the enzyme had a lower K_m for SAAPLpNA, 54 μM.The N-terminal amino acid sequence of the first 20 amino acids of the purified chymotrypsin was IVGGQEATIGEYPWQAALQV.     

Visual navigation of wheeled mobile robots using direct feedback of a geometric constraint

Many applications of wheeled mobile robots demand a good solution for the autonomous mobility problem, i.e., the navigation with large displacement. A promising approach to solve this problem is the following of a visual path extracted from a visual memory. In this paper, we propose an image-based control scheme for driving wheeled mobile robots along visual paths. Our approach is based on the feedback of information given by geometric constraints: the epipolar geometry or the trifocal tensor. The proposed control law only requires one measurement easily computed from the image data through the geometric constraint. The proposed approach has two main advantages: explicit pose parameters decomposition is not required and the rotational velocity is smooth or eventually piece-wise constant avoiding discontinuities that generally appear in previous works when the target image changes. The translational velocity is adapted as demanded for the path and the resultant motion is independent of this velocity. Furthermore, our approach is valid for all cameras with approximated central projection, including conventional, catadioptric and some fisheye cameras. Simulations and real-world experiments illustrate the validity of the proposal.     

Compatibility of Fibreglass Woven Roving and Commercially Available Phenolic Resins

Three commercially available phenolic resins are assessed for compatibility with a fibreglass wovenroving reinforcement. Compatibility assessment is based on laminate physical properties f flexuralstrength and modulus in three and four point bending, interlaminar shear strength, and tensilestrength and modulus. The physical properties are also used for assessment of hand laminatedglass/phenolic systems