Effect of surfactant concentration, pH, and shear rate on the rheological properties of aqueous systems of a hydrophobically modifed chitosan and its unmodified analogue

Oscillatory shear, shear relaxation and viscosity experiments have been carried out on semidilute solutions of chitosan and on a hydrophobically modified analogue (HM-chitosan) in 1% acetic acid. This was done in the presence of various amounts of cetyltrimethylammonium bromide (CTAB) and at different pH values. All the rheological measurements on the HM-chitosan solutions revealed significant polymer-surfactant interaction and pH effects. The observed rheological effects were least pronounced at pH ≈ 4, while a strong viscoelastic response was found at pH values of 1 and 5 in HM-chitosan solutions of low surfactant concentration. At these conditions, significant shear-thinning effects were observed. In semidilute solutions of unmodified chitosan, the influence of pH, surfactant concentration and shear rate on the rheological properties was moderate or insignificant. Received: 25 September 1996/Revised version: 30 October 1996/Accepted: 4 November 1996     

Reduction of the blood alcohol concentration limit in Norway—Effects on knowledge,behavior and accidents

From January 1, 2001, the legal blood alcohol concentration (BAC) limit in Norway was reduced from 0.5 to 0.2 g/l. A before-and-after telephone survey concerning the effects of the reduced BAC limit was carried out. 3001 driver's license holders were interviewed before and after the amendment. The percentage of drivers claiming that they will drink no alcohol before driving has increased from 82 to 91 percent, thus the distinction between driving a motor vehicle and drinking alcohol has become clearer. Drivers influenced by alcohol and involved in accidents have on the average much higher BACs than 0.5 g/l. Statistics on alcohol-related accidents are not available for the years before and after the legal amendment, but single-vehicle night-time and weekend personal-injury and fatal crashes are used as surrogate measures. There are no significant decreases in these proxies from the six years before to the six years after the reductions of the legal limit.     

Study of the factors determining the mobility of ions in the polypyrrole films doped with aromatic sulfonate anions

The electrochemical redox behavior of the polypyrrole (PPy) films doped with benzenesulfonate (BS), p-toluenesulfonate (pTS) and naphtalene-1,5-disulfonate (NDS) was investigated by cyclic voltammetry, the chemical composition of the films was determined by XDS, the surface morphology was characterized by AFM, and the interactions between pyrrole oligomers and the anions were modeled with quantum chemical methods. It is the first detailed comparative study of the properties of these interesting systems with two complementing interactions (electrostatic and aromatic stacking). It was shown than these relatively similar aromatic sulfonate anions have rather different behavior in PPy films. The results showed that the redoxactivity of polypyrrole films doped with sulfonate ions increases in the sequence pTS < BS < NDS. The comparison of voltammograms measured in the presence of different anions with PPy films synthesized in the same solution show that the PPy/pTS films have the most densely packed and the PPy/NDS films the least densely packed structure of the three. The mobility of ions in these films is mainly determined by the packing of the films, which in turn partly depends on the interactions between the dopant-anion and polymer chains.     

Safety Performance Indicator for alcohol in road accidents—International comparison, validity and data quality

Safety Performance Indicators, SPIs, are developed for various areas within road safety such as speed, car occupant protection, alcohol and drugs, vehicle safety, etc. SPIs can be used to indicate the road safety situation and to compare road safety performance between countries and over time and to understand the process leading to accidents, helping to select the measures to reduce them. This article describes an alcohol SPI defined as the percentage of fatalities resulting from accidents involving at least one driver impaired by alcohol. The calculation of the alcohol SPI for 26 European countries shows that the SPI varies from 4.4% in Bulgaria to 72.2% in Italy. These results raise the question if the results reflect the real situation or if there is a methodological explanation. To answer this question three different studies were carried out: comparison with other alcohol SPIs, in-depth studies of data quality in seven selected countries, and a study of correlations between the SPI and influencing factors.These studies indicate clearly that there is a need to improve quality of the data used for the alcohol SPI. Most importantly, the total number of drivers involved in fatal accidents, the number tested for alcohol and the number not tested, should be reported, in addition to the number of alcohol positive and negative drivers among those tested. Until these improvements are made, the validity of this SPI seems poor and comparison of the alcohol SPI results across countries should be made with caution.     

Asymptotic Poisson distribution for the number of system failures of a monotone system

It is well known that for highly available monotone systems, the time to the first system failure is approximately exponentially distributed. Various normalising factors can be used as the parameter of the exponential distribution to ensure the asymptotic exponentiality. More generally, it can be shown that the number of system failures is asymptotic Poisson distributed. In this paper we study the performance of some of the normalising factors by using Monte Carlo simulation. The results show that the exponential/Poisson distribution gives in general very good approximations for highly available components. The asymptotic failure rate of the system gives best results when the process is in steady state, whereas other normalising factors seem preferable when the process is not in steady state. From a computational point of view the asymptotic system failure rate is most attractive.     

Relationship between proteolysis and angiotensin-I-converting enzyme inhibition in different cheeses

The inhibition of angiotensin-I-converting enzyme (ACE) by the ethanol (70%)-soluble fraction (ESF) from different cheeses was analysed with an extract from rabbit lung acetone powder as enzyme source and 2-furanacryloyl-1-phenylalanylglycylglycine (FAPGG) as substrate. Proteolysis was assessed by a spectroscopic o-phthaldialdehyde (OPA) assay of the pH 4.6-soluble fraction and ESF. Peptides in the ESF were separated by reverse phase-HPLC. The traditional Norwegian cheese Gamalost had per unit cheese weight higher ACE inhibition potential than Brie, Roquefort and Gouda-type cheese, likely due to the combination of highest protein content and most extensive proteolysis providing a high content of ACE inhibitory peptides. However, ACE-inhibition expressed as IC₅₀ per unit peptide concentration from ESF assessed by the OPA-assay was highest for Kesam, a Quark-type cheese with a low degree of proteolysis.     

Some considerations on the treatment of uncertainties in risk assessment for practical decision making

This paper discusses the challenges involved in the representation and treatment of uncertainties in risk assessment, taking the point of view of its use in support to decision making. Two main issues are addressed: (1) how to faithfully represent and express the knowledge available to best support the decision making and (2) how to best inform the decision maker. A general risk-uncertainty framework is presented which provides definitions and interpretations of the key concepts introduced. The framework covers probability theory as well as alternative representations of uncertainty, including interval probability, possibility and evidence theory.     

Transrectal ultrasonography to assess local extent of prostatic cancer before radical prostatectomy

BACKGROUND: The safety and efficacy of operations for gastrointestinal diseases in very elderly patients has been a matter of debate in recent years. STUDY DESIGN: One hundred seventy-seven instances of carcinoma of the colon and rectum in patients more than 80 years of age who wee surgically treated between 1961 and 1987 were reviewed. They were compared with 623 similar instances in patients younger than 80 years of age who were treated during the same time period. RESULTS: Octogenarians and nonagenarians significantly more often displayed obstruction or perforation, elevated preoperative carcinoembryonic antigen, right-sided lesions, and solitary hepatic metastases, when present. Patients more than 80 years of age received adjuvant chemotherapy or radiotherapy less often. Carcinoma recurrence in very elderly patients implied a very poor prognosis, with only a 4 percent salvage rate. The actuarial five year survival rate was 32 percent for the older patients and 48 percent in the younger group (p < 0.05). There was no significant difference in operative mortality between the two groups. CONCLUSIONS: In general, age alone should not alter treatment strategy in patients with carcinoma of the colon and rectum.     

TTT-based tests for trend in repairable systems data

A major aspect of analysis of failure data for repairable systems is the testing for a possible trend in interfailure times. This paper reviews some important and popular graphical methods and tests for the nonhomogeneous Poisson process model. In particular, the total time on test (TTT) plot is considered, and trend tests based on the TTT-statistic are motivated and derived. In particular, a test based on the Anderson-Darling statistic is suggested. The tests are evaluated and compared in a simulation study, both with respect to the achievement of correct significance level and rejection power. The considered alternatives to ‘no trend’ are the log-linear, power law and a class of bathtub-shaped intensity functions. The simulation study involves single systems, as well as the case where several independent systems of the same kind are observed.     

Optimal inspection when the system is repaired upon detection of failure

In Barlow and Proschan (Mathematical Theory of Reliability, 1965, Section 3.2) a cost model is presented for a system subject to random failure and whose state is known only by inspection. Upon detection of failure repair (or replacement) is performed and the system is then as good as new. A method of determining the inspection schedule which minimizes the long run average (expected) cost per unit time is proposed. In this present paper we look closer into the problem of finding an optimal inspection schedule for this model. Some new results, which are useful in connection with the computation of the optimal inspection schedule, are given.