On the polynomial equations for the MIMO LQ stochastic regulator

The role played by three polynomial equations in the LQ stochastic regulation problem is discussed. The emphasis is on establishing conditions under which the LQ regulator can be obtained via the solution of a single uncoupled Diophantine equation. Nevertheless, the authors do not claim that there is any advantage in solving a single uncoupled equation in place of two coupled Diophantine equations     

Investigation of microelement content of bulk milk from different regions of Italy

Samples of bulk milk were analyzed for their lead, cadmium, zinc, chromium and copper contents in relationship to the production zone and at various periods of the year. The results obtained showed that the milk samples examined would be considered free from peaks of metal contamination. The metal contents of milk analysed were not related to the different degrees of pollution in the various zones or the type of the animals' diet, but mainly to chance.     

NO2 and N2 sorption in MFI films with varying Si/Al and Na/Al ratios

MFI crystals or films with controlled thicknesses and different Si/Al ratios were grown on seeded cordierite monoliths using a clear synthesis mixture with template or a template-free gel. The materials were analyzed by scanning electron microscopy, X-ray diffraction, inductively coupled plasma-atomic emission spectrometry, X-ray photoelectron spectroscopy, thermogravimetric analysis and sorption experiments using N₂ or NO₂ adsorbates. The films were uniformly distributed over the support surface. As expected, the specific monolayer N₂ adsorption capacity (mol/g_zeolite) was constant and independent of film thickness. The specific molar NO₂ adsorption capacity was significantly lower than the specific molar monolayer N₂ adsorption capacity, indicating that NO₂ is adsorbed at specific sites rather than evenly distributed in a monolayer. A number of NO₂ adsorption sites with varying strengths were observed by TPD experiments. At 30 °C, the amount of adsorbed NO₂ in the MFI films increased with increasing Al and Na content as opposed to the N₂ adsorption capacity, which was independent of these parameters. At 200 °C, the adsorbed amount of NO₂ was lower than at 30 °C and apparently independent on Al concentration in the Na-MFI films. These results indicate that different mechanisms are involved in NO₂ adsorption. NO₂ may adsorb weakly on Na⁺ cations and also react with silanol groups and residual water in the zeolite, the latter two results in more strongly bound species. Upon NO₂ adsorption, formation of NO was observed. This work represents the first systematic study of the effects of Al and Na content on NO₂ adsorption in MFI films.     

Synchronous primary carcinoma of the colon. Diagnostic and therapeutic problems

Seven hundred and twenty-three patients with colorectal carcinoma were treated consecutively from November 1973 to April 1997. Seven patients (0.96%) were found to have two colorectal carcinomas (synchronous carcinoma), located in separated colonic areas. Clinical histories were analyzed with reference to sex, age, symptoms, physical findings, disease localization, pathologic classification, and survival data. Preoperative diagnosis of synchronous lesions is difficult, being achieved in only 2 cases, but it is important for the proper treatment of patients. It is concluded that full examination of the colon in all patients presenting with primary colorectal cancer is mandatory and that colonoscopy should be used to effectively screen patients for synchronous cancers.     

Leisure and occupational physical activity and risk of colorectal adenomatous polyps

Multiple studies have shown a protective effect for physical activity on the incidence of colorectal cancer, but few have addressed its association with incident adenomas and none have investigated its association with metachronous adenomas. We interviewed 2,001 patients undergoing colonoscopy in 3 New York City practices between 1986-1988. Of these, 298 had a first diagnosis of adenomas, 506 had normal colonoscopies, 197 had metachronous adenomas and 345 had normal colonoscopies with a past history of adenomas. Subjects were queried regarding use of moderate amounts of recreational exercise (swimming, jogging, biking, racket sports and other sports) on a regular basis, and were also asked to estimate their level of physical activity. Occupational physical activity was assessed through a blinded coding of occupational titles. After adjusting for age, years of education, body mass index, total caloric intake, dietary fiber intake, dietary fat intake and years of cigarette smoking, protective effects of borderline significance were observed among males for leisure physical activity for metachronous and incident cases. Occupational physical activity was found to be significantly protective in male incident cases. Men with increased levels of either occupational or leisure activity showed a reduction for incident and metachronous cases. No effects were observed for females. Thus, in this study, both leisure and occupational physical activity were associated with a reduced risk of incident and metachronous adenomas among men but not women.     

Exact and inexact LQG model matching problems

The design of discrete-time LQG (linear-quadratic-Gaussian) controllers that yield closed-loop systems that match a provided model is addressed. The solution is in the form of a two-degree-of-freedom controller having feedback and feedforward paths that independently provide the optimal actions for disturbance rejection and model matching. Exact and approximate model matching cases are discussed in a unified fashion     

Evaluation of an automatic HPLC analyser for thalassemia and haemoglobin variants screening

In this paper the authors report the evolution of a new automatic HPLC analyser for screening haemoglobinopathies. HbA₂ and F determinations are accurate and reproducible. The analysis time is short (6.5 min) and there is a good separation between the HbA₂ values of β-thalassemia carriers from normals and α-thalassemia carriers, with no overlap between these groups. In addition, the system is also able to detect and quantitate most of the haemoglobin variants, particularly those (HbS, HbC, HbE and Hb Lepore) able to interact with β-thalassemia and could make haemoglobin electrophoresis unnecessary in all samples. The ease of operation and the limited technical work make this system especially suitable for laboratories with a high workload and allow the cost of screening to be reduced.