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  • Author: António Pacheco x
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Abstract

The detection of upward shifts in a process parameter using a CUSUM scheme can be improved by using an upper one-sided combined CUSUM–Shewhart scheme. Considerable advantage is to be gained since combined schemes take advantage of two well known facts: the Shewhart schemes behave well in case of a large shift, while CUSUM schemes allow a fast detection of small and moderate shifts. Having this in mind, upper one-sided combined CUSUM–Shewhart schemes for binomial data are discussed in detail in this paper. Numerical comparisons between upper one-sided combined CUSUM–Shewhart schemes and upper onesided CUSUM schemes with a 50% head start are also carried out, leading to – what we believe – surprising results.

Abstract

Ten years ago, a 73 year-old patient presented at our unit with a right nephritic colic and elevated serum creatinine (2.1 mg/dl). This was the first time that the patient had consulted for a urology workup. An abdominal X-ray was performed in which we observed a severe bilateral nephrocalcinosis with right ureteral lithiasis. One of the causes of nephrocalcinosis is distal renal tubular acidosis (dRTA), in that sense the patient presented metabolic acidosis (pH 7.25) together with normopotassaemia (4.4 meq/L) and normochlorine (105 mEq/L). A 24-hour urine test detected citrate (55 mg/dl), calcium (12 mg/dl) and pH of 6.5. A diuretic renogram showed the right relative renal function as 91.2% and left relative renal function as 8.8%. A test with bicarbonate and acetazolamide was performed, confirming a diagnosis of dRTA because the urinary CO2 pressure was 32 mmHg (normal, greater than 70 mmHg). Treatment with potassium citrate and increased intake of liquids was prescribed. Consequently, the patient’s serum creatinine normalized, her blood pH rose to 7.35 and urinary citrate increased to 154 mg/dl. After 10 years of treatment with potassium citrate the patient remains stable. We believe that in these patients it is crucial to carry out an alkalizing treatment: patients with dRTA cannot acidify the urine because a defect in the permeability of the tubule membrane prevents secretion of H+. It is important to administer potassium citrate continuously to improve blood pH, increase urinary citrate and reduce the risk of calcium phosphate crystallization.

Abstract

This study determined the effect of irradiance, temperature and photoperiod on the release of zygotospores and spermatia in Porphyra perforata from the Pacific coast of Baja California, Mexico. Reproductive blades were placed under controlled conditions of irradiance (5, 75, 150 and 300 μmol photons m−2 s−1), photoperiod [8:16; 12:12 and 16:8 light:dark (L:D)] and temperature (15, 18, 21 and 25°C). Peak zygotospore release occurred at 15–18°C and photoperiod of 16:8 L:D. Reproductive tissue released between 60% and 90% of zygotospores and spermatia during the first 10 days of incubation at 50 μmol photons m−2 s−1, 18°C and photoperiod of 16:8 L:D. Maximum zygotospore and spermatium release occurred in tissue collected between June and November. The number of zygotospores released was approximately 40% greater than that of spermatia (2.7×106 vs. 1.6×106 g FW−1 d−1). The reproductive foliar phase was observed throughout the year, but only thalli collected from April to January released zygotospores and spermatia. Collectively, the results suggest that low temperature, as observed in upwelling events, may induce high zygotospore and spermatium release during summer months.

Abstract

Kraft pulp is currently bleached largely by the elemental chlorine free (ECF) technology with oxygen, chlorine dioxide, and hydrogen as active agents. This technology brought about significant environmental improvements in relation to standard processes based on chlorine gas and hypochlorite, but there is still need for further improvements. This study presents a novel environmentally friendly bleaching stage – the so-called ‘hydrogen peroxide in supercritical carbon dioxide’, P(SC-CO2) – that can be adapted to current ECF bleaching processes, with preference in cases where hydrogen peroxide is already used. In this study, the P(SC-CO2) stage was evaluated as a replacement to the last peroxide stage of the D(EP)DP bleaching sequence and to the first peroxide stage of the D(EP)DP sequence, for an oxygen delignified eucalypt kraft-O2 pulp. The P(SC-CO2) stage was run with 0.5% hydrogen peroxide, at 15% consistency, 70°C, and 73 bar. The reaction time was 30 min. The performances of regular P stages and the new P(SC-CO2) stage were compared. Promising results were observed with the DEP(SC-CO2)DP sequence; the P(SC-CO2) decreased kappa number from 2.7 to 2.1, and the hexenuronic acid groups from 17.0 to 12.4 mmol kg-1. The P(SC-CO2) stage showed poor performance when applied in the D(EP)DP(SC-CO2) sequence. It is concluded that the process presents potential but requires further optimization to improve selectivity and efficiency.

Abstract

In the ground state, the p-methoxyphenyl-substituted pyranoflavylium cation I, prepared by the reaction of the 5,7-dihydroxy-4-methylflavylium cation with p-methoxybenzaldehyde, is a weak acid (pKa=3.7±0.1). In its lowest excited singlet state, I is a moderate photoacid (pKa*=0.67) in 30% methanol-water acidified with trifluoroacetic acid (TFA). In comparison to anthocyanins and 7-hydroxyflavylium cations, the photoacidity of I is much less pronounced and the rate of proton loss from the excited acid form of I much slower (by a factor of up to 100). In 50% ethanol:0.10 mol dm−3 HClO4, the excited state of the acid form of I undergoes fast (12 ps) initial relaxation (potentially in the direction of an intramolecular charge transfer state), followed by much slower (340 ps) adiabatic deprotonation to form the excited base. The excited base in turn exhibits a moderately fast relaxation (70 ps), consistent with solvent hydrogen-bond reorganization times, followed by slower but efficient decay (1240 ps) back to the ground state. As in uncomplexed anthocyanins and 7-hydroxyflavylium cations, the photophysical behavior of I points to excited state proton transfer as the dominant excited state deactivation pathway of pyranoanthocyanins, consistent with relatively good photostability of natural pyranoanthocyanins.

Abstract

We report the postnatal diagnosis of Van der Woude syndrome (VWS) in a foetus found to have an isolated right cleft lip and palate by ultrasound examination. After prenatal genetic counselling, the parents declined further evaluation by amniocentesis. At delivery, the infant was also found to have labial pits in the lower lip in addition to the cleft lip and palate identified by ultrasound consistent with VWS. Although VWS is rare, its autosomal dominant inheritance and variable penetrance should prompt additional modalities to more thoroughly evaluate the extent of other organ system and more extensive craniofacial anomalies.

Abstract

This paper describes the application of simple quality control charts to monitor the traffic intensity of single server queues, a still uncommon use of what is arguably the most successful statistical process control tool. These charts play a vital role in the detection of increases in the traffic intensity of single server queueing systems such as the M/G/1, GI/M/1 and GI/G/1 queues. The corresponding control statistics refer solely to a customer-arrival/departure epoch as opposed to several such epochs, thus they are termed short-memory charts. We compare the RL performance of those charts under three out-of-control scenarios referring to increases in the traffic intensity due to: a decrease in the service rate while the arrival rate remains unchanged; an increase in the arrival rate while the service rate is constant; an increase in the arrival rate accompanied by a proportional decrease in the service rate. These comparisons refer to a broad set of interarrival and service time distributions, namely exponential, Erlang, hyper-exponential, and hypo-exponential. Extensive results and striking illustrations are provided to give the quality control practitioner an idea of how these charts perform in practice.

Abstract

The traffic intensity (ρ) is a vital parameter of queueing systems because it is a measure of the average occupancy of a server. Consequently, it influences their operational performance, namely queue lengths and waiting times. Moreover, since many computer, production and transportation systems are frequently modelled as queueing systems, it is crucial to use control charts to detect changes in ρ. In this paper, we pay particular attention to control charts meant to detect increases in the traffic intensity, namely: a short-memory chart based on the waiting time of the n-th arriving customer; two long-memory charts with more sophisticated control statistics, and the two cumulative sum (CUSUM) charts proposed by Chen and Zhou (2015). We confront the performances of these charts in terms of some run length related performance metrics and under different out-of-control scenarios. Extensive results are provided to give the quality control practitioner a concrete idea about the performance of these charts.

Abstract

In this work, the absorption of pure carbon dioxide by aqueous triethanolamine solutions (TEA) was studied in terms of the kinetic process. The process was made in a stirred tank reactor with a flat and known interfacial area, the operating variables being temperature (288 to 313 K) and concentration in the range 0.1-2.0 M. From the results, it was deduced that the absorption of pure carbon dioxide by aqueous triethanolamine takes place under isothermal conditions in which there is an instantaneous reaction regime at low concentrations, while at higher concentrations it takes place in a moderately fast reaction regime, following a first-order kinetic with respect to alkanolamine. In these conditions of concentrations and temperatures essayed, an expression for the constant kinetic was deduced.