Formulation of blended cement: Effect of process variables on clay pozzolanic activity

Chemical, physical and mineralogical properties of crude and calcined local kaolinitic clay were studied in detail in order to use it as an artificial pozzolan. The aim of this study was to investigate and optimize the properties of mortars in which calcined clay is employed as a pozzolan.A three variable (calcination time: X1, calcination temperature: X2 and % of calcined clay in the blended cement: X3) rotatable orthogonal composite design was set up. It was concluded that the compressive strengths were governed by the calcination temperature and the percentage of the calcined clay in the blended cement. It was proven that the strengths could be improved by increasing simultaneously the percentage of incorporation and the calcination temperature of the clay. It was also demonstrated that at temperatures lower than 700 °C, the increase of the calcination time, improved the compressive strength, while above 700 °C, the opposite effect was observed. Finally, a blended cement composition has been formulated and optimized using the desirability functions. The optimized blended cement contains 25% of calcined clay, heated for 3 h at a temperature of 750 °C.     

Determinants of salivary cotinine levels among current smokers in Mexico.

The present study describes salivary cotinine levels and their relationship to cigarettes smoked per day in Mexican smokers. Using a sampling strategy based on the number of cigarettes per day, we recruited 1,222 smokers from Mexico City and the state of Morelos in Mexico during 1999. Smoking behaviors and other factors known to affect nicotine intake and cotinine level were identified in an interview using a standardized questionnaire. Salivary cotinine was measured by capillary gas chromatography with nitrogen-phosphorus detection. We used generalized additive models to describe the relationship between salivary cotinine levels and variables of interest. The mean age of the population was 39.7 years (SD=15.6 years), with a mean cotinine level of 194.7 ng/ml (SD=134.8; range=10.1-767). Participants smoked a mean of 15.5 cigarettes per day (SD=11.3). Salivary cotinine and cigarettes smoked per day were positively related, although the association was not linear, flattening above 20 cigarettes per day. After adjusting for cigarettes per day, we found that significant predictors of cotinine levels included age, body mass index, cigarette producer, and smoking behavior variables. These results may have implications for dosing with nicotine medications to aid smoking cessation in Mexican smokers and suggest that whether the cigarette is labeled light or regular has no relationship to nicotine dose from smoking cigarettes.     

Burkitt's lymphoma mimicking an acute dentoalveolar abscess

Burkitt's lymphoma is a monoclonal proliferation of B lymphocytes classified histologically as a poorly differentiated lymphocytic lymphoma. The jaw and retroperitoneal structures are the most commonly involved sites. Prognosis is highly dependent on the stage of the disease. In some cases, the first manifestation of Burkitt's lymphoma is in the jaws, and symptoms may be misdiagnosed as infection. Dental radiographs can play an important role in the diagnosis. A case of a peculiar Burkitt's lymphoma involving the mandible that was misdiagnosed as an acute dentoalveolar abscess is presented.     

Fault‐tolerant procedures for redundant computer systems

Real‐time computer systems deployed in life‐critical control applications must be designed to meet stringent reliability specifications. The minimum acceptable degree of reliability for systems of this type is ‘7 nines’, which is not generally achieved. This paper aims at contributing to the achievement of that degree of reliability. To this end, this paper proposes a classification scheme of the fault‐tolerant procedures for redundant computer systems (RCSs). The proposed classification scheme is developed on the basis of the number of counteracted fault types. Table I is created to relate the characteristics of the RCSs to the characteristics of the fault‐tolerant procedures. A selection algorithm is proposed, which allows designers to select the optimal type of fault‐tolerant procedures according to the system characteristics and capabilities. The fault‐tolerant procedure, which is selected by this algorithm, provides the required degree of reliability for a given RCS. According to the proposed graphical model only a part of the fault‐tolerant procedure is executed depending on the absence or presence (type and sort) of faults. The proposed methods allow designers to counteract Byzantine and non‐Byzantine fault types during degradation of RCSs from N to 3, and only the non‐Byzantine fault type during degradation from 3 to 1 with optimal checkpoint time period. Copyright © 2008 John Wiley & Sons, Ltd.     

Building and Querying a P2P Virtual World

Peer-to-Peer (P2P) systems are known to provide excellent scalability in a networked environment. One peer is introduced to the system by each participant. However current P2P applications can only provide file sharing and other forms of relatively simple data communications, and, in this paper, we demonstrate how this limitation can be bridged by indexing and querying a 3D virtual-world on a dynamic distributed network. We present an algorithm for 3D range queries as well as an algorithm for nearest neighbor queries. We also show how to build such a complex application from the ground level of a P2P routing algorithm.     

Assessment of ecologic regression in the study of lung cancer and indoor radon

Ecologic regression studies conducted to assess the cancer risk of indoor radon to the general population are subject to methodological limitations, and they have given seemingly contradictory results. The authors use simulations to examine the effects of two major methodological problems that affect these studies: measurement error and misspecification of the risk model. In a simulation study of the effect of measurement error caused by the sampling process used to estimate radon exposure for a geographic unit, both the effect of radon and the standard error of the effect estimate were underestimated, with greater bias for smaller sample sizes. In another simulation study, which addressed the consequences of uncontrolled confounding by cigarette smoking, even small negative correlations between county geometric mean annual radon exposure and the proportion of smokers resulted in negative average estimates of the radon effect. A third study considered consequences of using simple linear ecologic models when the true underlying model relation between lung cancer and radon exposure is nonlinear. These examples quantify potential biases and demonstrate the limitations of estimating risks from ecologic studies of lung cancer and indoor radon.     

Formation of polycyclic aromatic hydrocarbons in beef and lamb kokorec: Effects of different animal fats

Traditional kokorec, which is one of the products of offal (edible by-products) and consumed enthusiastically in Turkey, is produced from fresh and washed lamb and calf small intestines. Some health risks can occur unless hygiene and sanitation rules are followed and proper cooking procedures are applied during the production process of kokorec. One of the most important among these risks is the microbial origin hazard and another is the formation of polycyclic aromatic hydrocarbons. In this study, the aim was to determine the concentrations of eight polycyclic aromatic hydrocarbons formed during the cooking of kokorec produced from beef and lamb small intestines by adding various animal fats. Polycyclic aromatic hydrocarbonformation was specified in ready-to-consume kokorec samples in which eight polycyclic aromatic hydrocarbon concentrations varied between 3.07 and 40.11 µg/kg. The consumption of lamb kokorec could be recommended to consumers because its average total eight polycyclic aromatic hydrocarbon concentration was lower than that of beef kokorec.