Influence of ohmic heating on rheological and electrical properties of reconstituted whey solutions

Reconstituted whey solutions (in the range of 8–24% w/v solute concentrations) were heated from 20 °C to prescribed temperatures (30, 40, 50, 60, 70 or 80 °C) ohmically by applying voltage gradients of 20, 30 or 40 V/cm, and conventionally at water bath. Electrical conductivity changes with increasing temperature were linear during ohmic heating. Whey solutions have non-Newtonian characteristics since Herschel–Bulkley model satisfactorily fitted the experimental shear stress–shear rate data. “n” values were in the range of 0.520–1.503. The whey solution having 24% concentration had a yield stress of 0.006–0.024 Pa at low temperatures. Although temperature and concentration were critical factors for the consistency and the electrical conductivity changes during heating (p < 0.01), the voltage gradient was not effective statistically. The high correlation (between ?0.910 and ?0.991) was obtained between changes of electrical conductivity and consistency coefficient values during ohmic heating. Since activation energies for ohmic heating (26.34–45.79 kJ/mol) depending on solute concentration were lower than conventional heating (26.70–50.04 kJ/mol), reconstituted whey solutions were less sensible to temperature changes during ohmic heating. It was recommended that ohmic heating could be applied as a faster alternative heating method in the whey processing.     

Congenital erythropoietic porphyria successfully treated by allogeneic bone marrow transplantation

The long-term biochemical and clinical effectiveness of allogenic bone marrow transplantation (BMT) was shown in a severely affected, transfusion-dependent 18-month-old female with congenital erythropoietic porphyria (CEP), an autosomal recessive inborn error of heme biosynthesis resulting from mutations in the uroporphyrinogen III synthase (URO-synthase) gene. Three years post-BMT, the recipient had normal hemoglobin, markedly reduced urinary porphyrin excretion, and no cutaneous lesions with unlimited exposure to sunlight. The patient was homoallelic for a novel URO-synthase missense mutation, G188R, that expressed less than 5% of mean normal activity in Escherichia coli, consistent with her transfusion dependency. Because the clinical severity of CEP is highly variable, ranging from nonimmune hydrops fetalis to milder, later onset forms with only cutaneous lesions, the importance of genotyping newly diagnosed infants to select severely affected patients for BMT is emphasized. In addition, the long-term effectiveness of BMT in this patient provides the rationale for future hematopoietic stem cell gene therapy in severely affected patients with CEP.     

Amitriptyline: a potent inhibitor of butyrylcholinesterase from human serum

We used a new vasodilator, TTC-909 (a prostaglandin I2 analog incorporated in lipid microspheres), which produced marked reduction in the pulmonary arterial pressure and resistance in an infant with primary pulmonary hypertension.     

Gain–bandwidth limitations of microwave transistor

This work enables one to obtain the potential gain (G_T) characteristics with the associated source (Z_S) and load (Z_L) termination functions, depending upon the input mismatching (V_i), noise (F), and the device operation parameters, which are the configuration type (CT), bias conditions (V_DS, I_DS), and operation frequency (f). All these functions can straightforwardly provide the following main properties of the device for use in the design of microwave amplifiers with optimum performance: the extremum gain functions (G_{T max}, G_{T min}) and their associated Z_S, Z_L terminations for the V_i and F couple and the CT, V_DS, I_DS, and f operation parameters of the device point by point; all the compatible performance (F, voltage–standing wave ratio V_i, G_T) triplets within the physical limits of the device, which are F ≥ F_min, V_i ≥ 1, G_{T min} ≤ G_T ≤ G_{T max}, together with their Z_S, Z_L termination functions; and the potential operation frequency bandwidth for a selected performance (F, V_i, G_T) triplet. The selected performance triplet and termination functions can be realized together with their potential operation bandwidth using the novel amplifier design techniques. Many examples are presented for the potential gain characteristics of the chosen low‐noise or ordinary types of transistor. © 2002 Wiley Periodicals, Inc. Int J RF and Microwave CAE 12, 483–495, 2002. Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mmce.10049     

Self-excitation of induction motors compensated by permanently connected capacitors and recommendations for IEEE std 141-1993

Self-excitation of induction motors compensated by permanently connected capacitors is investigated in this paper. Theoretical analyses of self-excitation phenomenon are carried out by using some simplified equivalent circuits, and a hybrid mathematical model in ABC/dq axes, respectively, in steady state and transient state. An unusual operating condition about water pumping stations is reported, in which water within the pipeline may drive the motor in the reverse direction at speeds higher than synchronous, when a supply interruption coincides with a check-valve failure. In order to prevent the motor from dangerous overvoltages due to self-excitation, it is recommended to connect a simple static protection circuit consisting of a resistor in series with a thyristor switch between any two lines of the motor. Critical resistance boundaries, which will lead to loss of excitation, and demagnetization of the rotor core are determined separately as a function of operating speed. A suitable resistance value chosen in the safe design area constitutes a reliable protection mechanism against self-excitation.     

Optimizing cutting parameters in process planning of prismatic parts by using genetic algorithms

The determination of optimal cutting parameters, such as the number of passes, depth of cut for each pass, cutting speed and feed, which are applicable for assigned cutting tools, is one of the vital modules in process planning of metal parts, since the economy of machining operations plays an important role in increasing productivity and competitiveness. The present paper introduces a 'system software' developed to optimize the cutting parameters for prismatic parts. The system is mainly based on a powerful artificial intelligence (AI) tool, called genetic algorithms (GAs). It is implemented using C programming language and on a PC. It can be used as standalone system or as the integrated module of a process planning system called OPPS-PRI (Optimized Process Planning System for PRIsmatic parts) that was also developed for prismatic parts and implemented on a vertical machining centre (VMC). With the use of GAs, the impact and power of AI techniques have been reflected on the performance of the optimization system. The methodology of the developed optimization system is illustrated with practical examples throughout the paper.     

Mechanical spectra and calorimetric evaluation of gelatin–xanthan gum systems with high levels of co-solutes in the glassy state

Mechanical properties of gelatin–xanthan gum (XG) mixtures with high levels of co-solutes were examined by dynamic mechanical analysis (DMA). The mechanical spectra of the samples were modeled according to the Williams–Landel–Ferry (WLF) equation/free-volume theory, which requires an entropic lightly cross-linked network. For the α dispersion, E′ and E′′ superposed with the horizontal shift factor a_T, which was temperature-dependent according to the WLF equation; no other secondary dispersion mechanism was detected. The addition of XG to gelatin networks with high levels of co-solutes changed the glass transition temperature (T_g) and kinetics of glass transition and glassy states. In the glassy state, the WLF equation was unable to follow progress in the mechanical properties, which were better described by the Andrade equation. The calorimetric measurements of the gelatin–XG systems were made using a modulated temperature differential scanning calorimetry (MTDSC) to improve the determination of T_g. The samples were exposed to two cooling and heating cycles to provide a controlled recent thermal history in the temperature range of 40 °C to −70 °C. The T_g values of the samples were determined from the second heating cycle in the reversing heat signal. The calorimetric T_g values increased with increasing glucose syrup:sucrose ratio due to increased crosslinking, whereas mechanical T_g decreased with increased XG content due to network formation.     

Rheological evaluation of gelatin–xanthan gum system with high levels of co-solutes in the rubber-to-glass transition region

Effects of moisture content, xanthan gum (XG) addition, and glucose syrup (GS):sucrose ratio on the gelation of gelatin-XG systems with high levels of co-solutes were investigated in the rubbery and the glass transition regions. Frequency sweep tests were performed between 0.1 and 100 rad and the storage (G′) and loss (G″) moduli of the system were measured in the temperature range of 60 to −15 °C. The onset of glass transition region increased with decreasing moisture content. The time–temperature superposition yielded master curves of G′ and G″ as a function of timescale of measurement. G″ and G″ were superimposed with the horizontal shift factor a_T, which was temperature dependent according to the Williams–Landel–Ferry (WLF) equation. Glass transition temperature (T_g) of the samples were determined by dynamic mechanical analysis (DMA) from the peak of tan δ. T_g decreased with XG addition. The energy of vitrification of samples with XG increased compared to samples containing only gelatin. Relaxation spectra of the samples were calculated from rheological measurements using the first and second approximations. The Rouse theory was more closely followed with the second approximation.