Makespan minimization for parallel machines scheduling with multiple availability constraints

The problem of makespan minimization for parallel machines scheduling with multiple planned nonavailability periods in the case of resumable jobs is considered. In the current state of the literature, there is a limited number of models and algorithms dealing with this problem and only for very small problem size, and nonavailability limited to some machines. The problem is first formulated as a mixed integer linear programming model and optimally solved using CPLEX for small to moderately large size problems with multiple availability constraints on all machines. An implicit enumeration algorithm using the lexicographic order is then designed to solve large-scale problems. Numerical results are obtained for several experiments and they show the validity and performance improvements procured by both the MILP model and the new enumeration algorithm.     

\hbox {Ph}_{3}\hbox {P/CCl}_{4} as a highly efficient reagent for one-pot N-alkylation of sulfonamides from alcohols: a rapid route to N-alkyl sulfonamides synthesis

A mild, efficient, and selective protocol for the one-pot $N$ -alkylation of sulfonamides with alcohols using triphenylphosphine and carbon tetrachloride is described. In this method, treatment of alcohols with a mixture of triphenylphosphine, carbon tetrachloride, and potassium sulfonylamide salts in refluxing anhydrous DMF furnishes the corresponding $N$ -alkyl sulfonamides in good to excellent yields. This protocol is highly efficient for various structurally diverse alcohols and potassium sulfonylamide salts. In this paper the influence of solvents and various reagents as sources for electrophilic-halogen instead of carbon tetrachloride in combination with triphenylphosphine have been examined. This protocol demonstrates the selectivity between primary and secondary alcohols. A plausible mechanism for this protocol has been described.     

UV-prepared salep-based nanoporous hydrogel for controlled release of tetracycline hydrochloride in colon

A highly swelling nanoporous hydrogel (NPH) was synthesized via UV-irradiation graft copolymerization of acrylic acid (AA) onto salep backbone and its application as a carrier matrix for colonic delivery of tetracycline hydrochloride (TH) was investigated. Optimized synthesis of the hydrogel was performed by the classic method. The swelling behavior of optimum hydrogel was measured in different media. The hydrogel formation was confirmed by Fourier transform infrared spectroscopy (FTIR) and thermo-gravimetric analysis (TGA/DTG/DTA). The study of the surface morphology of hydrogels using SEM showed a nanoporous (average pore size: about 350nm) structure for the sample obtained under optimized conditions. The drug delivery results demonstrated that this NPH could successfully deliver a drug to the colon without losing the drug in the stomach, and could be a good candidate as an orally administrated drug delivery system.     

A novel primary amine-based anion exchange membrane adsorber

A novel anion exchange membrane adsorber is presented which shows excellent impurity removal under different buffer conductivities ranging from 2 to 2 7mS/cm. The membrane utilizes a primary amine ligand (polyallylamine) and was designed specifically to bind impurities at high salt concentrations. Studies with DNA, endotoxin, and virus spiked into buffer at varying salt conditions were done, resulting in clearance of >3, 4, and 4 LRV, respectively, with negligible change on increasing salt up to 27 mS/cm conductivities. Verification of virus removal in mAb feedstocks is also shown. The data are compared with other membrane adsorbers and a conventional resin which utilize traditional chemistries to demonstrate improved purification performance with the primary amine ligand. Additional data on scale-up of the membrane adsorber device is discussed. A stacked flat-sheet design was implemented to ensure linear scale-up of performance using bovine serum albumin (BSA) as a model. The linearly scalable device, coupled with the highly effective membrane for virus, DNA, and endotoxin removal, represents a step forward in polishing technology for the purification of monoclonal antibodies and recombinant proteins.     

Should the AOAC use-dilution method be continued for regulatory purposes?

Despite its very poor reproducibility, AOAC INTERNATIONAL's use-dilution method (UDM) for bactericidal activity (AOAC Methods 964.02, 955.14, and 955.15) has been required by the U.S. Environmental Protection Agency (EPA) since 1953 for regulatory purposes, while methods with better reproducibility have been adopted in Canada and Australia. This study reviews UDM from a statistical perspective. Additionally, the test's expected results were compared to those obtained from actual evaluation of several formulations. Significant gaps have been identified in the reproducibility of the test data as predicted by statistical analysis and those presented to the EPA for product registration. UDM's poor reproducibility, along with its qualitative nature, requires the concentration of the active ingredient to be high enough to ensure all or most carriers to be free of any viable organisms. This is not in accord with the current trends towards sustainability, human safety, and environmental protection. It is recommended that the use of the method for regulatory purposes be phased out as soon as possible, and methods with better design and reproducibility be adopted instead.     

Optical parametric oscillator pumped by relaxation oscillation pulses of a mechanically Q-switched Nd:YAG laser

We report the generation of mid-infrared pulsed radiation between 2.2 and 3 μm range using a singly-resonant optical parametric oscillator (SR-OPO) based on a 40-mm-long crystal of periodically-poled LiNbO₃ (PPLN) pumped by mechanically Q-switched pulses from a Nd:YAG laser, obtained by chopping the beam inside the laser resonator over a 1–10 kHz duty cycle. An appreciable reduction in pulse width as well as the number of relaxation oscillation pulses of the Nd:YAG pump laser is observed when the frequency of the Q-switch chopper is increased up to 10 kHz. Sub-nanosecond relaxation oscillation pulses of about 170–210 ns duration are generated under the width of the idler envelope varying from 4.6 to 8.55 μs. The same behavior is observed for the signal wave. A maximum extraction efficiency of 22 % is obtained for the idler, corresponding to 785 mW of output power at 10 kHz. The tuning of the signal and idler beams were performed by temperature variation of the PPLN crystal within 100–200 °C range.     

Spectrum sensing and power/rate control in CDMA cognitive radio networks

In this paper, a two‐phase algorithm for the spectrum sensing and power/rate control of a secondary user (S‐user) or cognitive radio is proposed. In the first phase, the primary base station (P‐BS), which is conscious of both the number and the data rate of primary active users (P‐user), broadcasts theitusage capacity percentage (UCP) of its cell. Since knowing only the UCP is not enough to guarantee that the total load (of P‐users and S‐users) is less than a maximum permissible load, the S‐user must measure the total interference received from both the P‐users and other S‐users. In this direction, using both the UCP and measurement of the interference received from the P‐users and the S‐users by the S‐user or secondary base station (S‐BS), we mathematically derive an equation for issuing data transmission permission, which if it is held then the second phase of the algorithm: the transmit power/rate control starts. In this phase, the S‐user and the S‐BS look for feasible values for the transmit power level and transmission rate. If there are feasible values, it starts its transmission at these feasible transmit power and rate. Since both the location of the S‐user and the channel condition vary in time, the whole algorithm is iterated periodically with a period faster than the coherence time of the channel. Furthermore, we consider the down link of the above system with cooperation among neighboring S‐users to overcome fading channels and we investigate the amount of improvement in the reliability of the issuing data transmission permission. As well, we consider the uplink of the system with multiple antennas in the S‐BS to investigate the improvement in the same parameter over spatially correlated and independent fading channels. Theoretical analysis is validated using computer simulations. Both theoretical analysis and computer simulations show that the proposed cooperative spectrum sensing algorithm performs properly at SNR = ?5dB in flat Nakagami‐m fading channels with m = 1 even in correlated fading channels. We also address the improvement of the reliability of the issuing data transmission permission in the uplink in case of using multiple antennas only in the S‐BS. Copyright © 2011 John Wiley & Sons, Ltd.     

Setting staffing requirements for time dependent queueing networks: The case of accident and emergency departments

An incentive scheme aimed at reducing patients’ waiting times in accident and emergency departments was introduced by the UK government in 2000. It requires 98% of patients to be discharged, transferred, or admitted to inpatient care within 4 hours of arrival. Setting the minimal hour by hour medical staffing levels for achieving the government target, in the presence of complexities like time-varying demand, multiple types of patients, and resource sharing, is the subject of this paper. Building on extensive body of research on time dependent queues, we propose an iterative scheme which uses infinite server networks, the square root staffing law, and simulation to come up with a good solution. The implementation of this algorithm in a typical A&E department suggests that significant improvement on the target can be gained, even without increase in total staff hours.     

Differential pulse voltammetric simultaneous determination of noradrenalin and acetaminophen using a hematoxylin biosensor

A highly efficient noradrenalin (NA) biosensor was fabricated on the basis of hematoxylin electrodeposited on a glassy carbon electrode, GCE. The cyclic voltammetric responses of the hematoxylin biosensor at various scan rates, which were obtained in a 0.25 mmol L⁻¹ NA solution, showed the characteristic shape typical of an EC_cat process. The kinetic parameters such as electron transfer coefficient, α, the catalytic electron transfer rate constant, k′, and the standard catalytic electron transfer rate constant, k⁰, for oxidation of NA at the hematoxylin biosensor surface were estimated using cyclic and RDE voltammetry. The peaks of differential pulse voltammetric (DPV) for NA and acetaminophen (AC) oxidation at the hematoxylin biosensor surface were clearly separated from each other when they co-exited in the physiological pH (pH 7.0). It was, therefore, possible to simultaneously determine NA and AC in the samples at a hematoxylin biosensor. Linear calibration curves were obtained for 5.0 × 10⁻¹ to 65.40 μmol L⁻¹ and 65.40-274.20 μmol L⁻¹ of NA, and for 12.00-59.10 μmol L⁻¹ and 59.10-261.70 μmol L⁻¹ of AC. The sensitivities of the biosensor to NA in the absence and presence of AC were found virtually the same, which indicates the fact that the electrocatalytic oxidation processes of NA are independent of AC and, therefore, simultaneous or independent measurements of the two analytes (NA and AC) are possible without any interference. The results of 16 successive measurements show an average voltammetric peak current of 1.13 ± 0.03 μA for an electrolyte solution containing 5.00 μmol L⁻¹ NA. The hematoxylin biosensor has been satisfactorily used for the determination of NA and AC in pharmaceutical formulations. The results obtained, using the biosensor, are in very good agreement with those declared in the label of pharmaceutical inhalation products.