Inequivalence of the two tyrosine ligands in the N-lobe of human serum transferrin

Human serum transferrin N-lobe (hTF/2N) has four iron-binding ligands, including one histidine, one aspartate, and two tyrosines. The present report elucidates the inequivalence of the two tyrosine ligands (Tyr 95 and Tyr 188) on the metal-binding properties of hTF/2N by means of site-directed mutagenesis, metal release kinetics, and absorption and electron paramagnetic resonance (EPR) spectroscopies. When the liganding tyrosines were mutated individually to phenylalanine, the resulting mutant Y95F showed a weak binding affinity for iron and no affinity for copper, whereas, mutant Y188F completely lost the ability to bind iron but formed a stable complex with copper. Since other studies have demonstrated that mutations of the other two ligands, histidine and aspartate, did not completely abolish iron binding, the present findings suggest that the tyrosine ligand at position 188 is essential for binding of iron to occur. Replacement of Tyr 188 with phenylalanine created a favorable chemical environment for copper coordination but a fatal situation for iron binding. The positions of the two liganding tyrosines in the metal-binding cleft suggest a reason for the inequivalence.     

Reflex sympathetic function in cortisol-induced hypertension in humans

Nine healthy male subjects underwent measurement of reflex sympathetic function, pressor responsiveness and baroreflex sensitivity to phenylephrine (PE) and glyceryltrinitrate (GTN) before (C1) and following six days of treatment (E6) with cortisol (F), 200 mg/day. Seven subjects had washout studies (W) performed at least two weeks following the end of treatment. The BP responses to head tilt, isometric exercise and mental arithmetic were unaltered by F, however, there was a significant diminution of the diastolic BP response to cold pressor stimulus (delta DBP: 19 +/- 3 vs 25 +/- 5 vs 27 +/- 5 mmHg; E6 vs C1 vs W, p < 0.05 C1 vs E6 and W). Baroreflex sensitivity to PE was increased (28 +/- 3 vs 19 +/- 2 ms/mmHg, E6 vs C1, p = 0.03). These data demonstrate that increased BP during F treatment is not attributable to increased SNS activity, and suggest that SNS activity may be decreased by F.     

Full-Scale Tests of Seismic Cable Restrainer Retrofits for Simply Supported Bridges

Many parts of the central and southeastern United States have recently begun initiating seismic retrofit programs for bridges on major interstate highways. One of the most common retrofit strategies is to provide cable restrainers at the intermediate hinges and abutments in order to reduce the likelihood of collapse due to unseating. To evaluate the force-displacement behavior of the cable restrainer retrofits, a full-scale bridge setup was constructed based on an existing multispan, simply supported steel girder bridge in Tennessee, that has been considered for seismic retrofit using cable restrainers. Seismic cable restrainers were connected to the bridge pier using steel bent plates, angles, and undercut anchors embedded in the concrete as specified by typical bridge retrofit plans. The full-scale bridge model was subjected to monotonic loading to test the capacity of the cable restrainer system and to determine the modes of failure. The results showed that the primary modes of failure are in the connection elements of the pier and girders, and they occur at force levels much lower than the strength of the cable. Modifications to the connection elements were designed and tested. The new connections resulted in a higher strength and deformation capacity of the cable restrainer assembly.     

Pre-treatment of kraft pulp bleach plant effluent by selected ultrafiltration membranes

Three ultrafiltration membranes in series with molar mass cutoffs of 130,000, 15,000, and 5,000 Da, respectively were used to pretreat Kraft pulp bleach plant effluent prior to biological treatment. The TOC (total organic carbon), COD (chemical oxygen demand) and AOX (adsorbable organic halogen) reductions for the permeate were 65, 70 and 85%, respectively with no significant change of toxicity. Treatment of the ultrafiltration permeate using tighter ultrafiltration (UF) and nanofiltration (NF) membranes with molar mass cutoffs less than 1,500 Da, yielded TOC and AOX reductions of 90 and 99%, respectively with a permeate Microtox EC₅₀ level of 100%.     

Pump-induced thermal effects in Er-Yb fiber grating DBR lasers

Large absorption of 980-nm pumping in Er-Yb doped fibers causes significant temperature differentials along small length of the fibers. When pumped with 40 mW of power, unequal Bragg wavelength shifts of 0.25 and 0.16 mm were measured in the respective 6- and 10-mm-long Bragg reflectors constructed around the Er-Yb core of a 2.5-cm-long DBR laser. This causes large fluctuation in the laser's output power. Stable operation resumed with increased pump power. At 68 mW of pump power, 0.32-nm shift in lasing wavelength (corresponding to a temperature rise of 38°C) was measured in the distributed Bragg reflector fiber laser     

Achievable-SIR-based predictive closed-loop power control in a CDMAmobile system

A power control algorithm with two prediction models based on an achievable signal-to-interference power ratio (SIR) has been proposed under a multipath Rayleigh fading environment in a code-division multiple-access (CDMA) mobile system. An achievable SIR is defined as the maximum-minimum SIR among all users at a particular time step. The corresponding mobile transmission powers are denoted as the "optimum transmission powers." In the individual power predictor (IPP) model, a linear transversal filter is assigned to each user. The output of the IPP, which is a linear combination of the optimum transmission powers of the mobile during the current and previous power measurement periods, predicts the optimum transmission power of the mobile in the next time step. In the global power predictor (GPP) model, a single predictor, constructed by a linear neural network, is used to predict the optimum transmission powers of all mobiles in the next time step. In both predictor models, the weights of the predictors are updated by using the recursive least squares algorithm. To further improve the performance, a reduced power-measurement period has been studied. Simulation results show that the proposed power control algorithm can achieve a lower outage probability and a smaller dynamic range of transmission power compared with a conventional power control scheme     

Generalized correlation-delay-shift-keying scheme for noncoherent chaos-based communication systems

In this paper, we propose a generalized correlation-delay-shift-keying (GCDSK) scheme for noncoherent chaos-based communications. In the proposed scheme, several delayed versions of a chaotic signal are first produced. Some of them will be modulated by the binary data to be transmitted. The delayed signals will then be added to the original chaotic signal and transmitted. At the receiver, a simple correlator-type detector is employed to decode the binary symbols. The approximate bit error rate (BER) of the GCDSK scheme is derived analytically based on Gaussian approximation. Simulations are performed and compared with the noncoherent correlation-delay-shift-keying (CDSK) and differential chaos-shift-keying (DCSK) modulation schemes. The effects of the spreading factor, length of delay, and the number of delay units on the BER are fully studied. It is found that GCDSK can achieve better BER performance than DCSK under reasonable bit-energy-to-noise-power-spectral-density ratios.     

Nonlinear Models for Predicting Hoisting Times of Tower Cranes

Accuracy in estimating activity duration is one of the key prerequisites for successful construction planning. Efficient material transportation plays an important role in reducing costs and time. Time measurement and work-study techniques can provide good estimation of activity duration, but forming the databank for various conditions is expensive. The use of empirical models has been developed as an alternative to overcome the deficiency while maintaining a reasonable accuracy. In this research traditional linear regression models and nonlinear neural network models have been developed for predicting hoisting times of a tower crane. It is found that nonlinear neural network models can achieve higher accuracy. However, planners may find that the regression models, which describe the relationship between the variables in more simplistic terms, could allow them to shorten the hoisting times by manipulating the input variables. The results and the merits of the models are discussed.     

Different Directions of Switching of Chromium Oxide Thin Films

We have investigated the switching behavior of as-deposited CrO _x and post-annealed CrO _y films by use of a variety of electrodes (top electrode Ag, Ti; bottom electrode Pt, fluorine tin oxide (FTO)). Resistance switching is highly dependent on electrode material and post-annealing treatment. Among Pt devices, I–V hysteresis was observed for the Ag/CrO _x /Pt device only; no resistance switching was observed for Ag/CrO _y /Pt, Ti/CrO _x /Pt, and Ti/CrO _y /Pt devices. Among FTO devices, I–V hysteresis was observed for the Ag/CrO _x /FTO device whereas I–V hysteresis with the opposite switching direction was observed for Ag/CrO _y /FTO, Ti/CrO _x /FTO, and Ti/CrO _y /FTO devices. The direction of switching depends not only on electrode material but also on post-annealing treatment, which affects the density of grain boundaries. Thus, the density of grain boundaries determines the type of charge carrier involved in the switching process. For as-deposited CrO _x films with a high density of grain boundaries Ag filament paths mediated by electrochemical redox reaction were observed, irrespective of bottom electrode material (Pt or FTO). Post-annealed CrO _y films with a low density of grain boundaries suppressed electrochemical redox reaction in the Ag/CrO _y /Pt device but promoted short-range movement of O^2? ions through the bottom interface, resulting in resistance switching in the Ag/CrO _y /FTO device. Electrochemical redox reaction-controlled resistance switching occurred solely in oxides with a high density of grain boundaries or dislocations.