Program restructing in segmented virtual memory

Program restructuring in a segmented virtual memory system is examined on the base of empirical data. The measure of connectivity is based on the decrease of the space-time integral caused by combining the two segments. A heuristic clustering algorithm, based on the use of effectively reduced memory reference strings, is presented. It turns out that performance problems in a segmented system are created by the large number of small segments. Restructuring is able to improve the performance of the system essentially; the optimal performance is reached with values of the memory control parameter which are one magnitude smaller than those applicable to original programs. The clusters formed do not correspond to program phases, but to smaller units of program execution; thus the clustering result supports a hierarchical model of program locality. The restructuring process is reasonably insensitive both to the memory control parameters and to the input data used.     

Image reconstruction in optical tomography in the presence of coupling errors

Image reconstruction in optical tomography is a nonlinear and generally ill- posed inverse problem. Noise in the measured surface data can give rise to substantial artifacts in the recovered volume images of optical coefficients. Apart from random shot noise caused by the limited number of photons detected at the measurement site, another class of systematic noise is associated with losses specific to individual source and detector locations. A common cause for such losses in data acquisition systems based on fiber-optic light delivery is the imperfect coupling between the fiber tips and the skin of the patient because of air gaps or surface moisture. Thus the term coupling errors was coined for this type of data noise. However, source and detector specific errors can also occur in noncontact measurement systems not using fiber-optic delivery, for example, owing to local skin pigmentation, hair and hair follicles, or instrumentation calibration errors. Often it is not possible to quantify coupling effects in a way that allows us to remove them from the data or incorporate them into the light transport model. We present an alternative method of eliminating coupling errors by regarding the complex-valued coupling factors for each source and detector as unknowns in the reconstruction process and recovering them simultaneously with the images of absorption and scattering. Our method takes into account the possibility that coupling effects have an influence on both the amplitude and the phase shift of the measurements. Reconstructions from simulated and experimental phantom data are presented, which show that including the coupling coefficients in the reconstruction greatly improves the recovery of absorption and scattering images.     

Effects of supplementation with n-3 polyunsaturated fatty acids on cognitive performance and cardiometabolic risk markers in healthy 51 to 72 years old subjects: a randomized controlled cross-over study

Background

One of the major challenges associated with our ageing population is the increasing incidence of age-associated cognitive decline, which has significant implications for an individual's ability to lead a productive and fulfilling life. In pure economic terms the costs of ageing reflects decreased productivity and engagement with the workforce. The maintenance of brain health underpinning intact cognition is a key factor to maintaining a positive, engaged, and productive lifestyle. In light of this, the role of diet, including supplementation with nutritional and even pharmacological interventions capable of ameliorating the neurocognitive changes that occur with age constitute vital areas of research.

Methods

In order to reduce cognitive ageing, the ARC longevity intervention (ARCLI) was developed to examine the effects of two promising natural pharmacologically active supplements on cognitive performance. ARCLI is a randomized, placebo-controlled, double-blind, 3-arm clinical trial in which 465 participants will be randomized to receive an extract of Bacopa monnieri (CDRI08 300 mg/day), Pycnogenol (150 mg/day), or placebo daily for 12 months. Participants will be tested at baseline and then at 3, 6 and 12 months post-randomization on a wide battery of cognitive, neuropsychological and mood measures, cardiovascular (brachial and aortic systolic and diastolic blood pressures as well as arterial stiffness), biochemical (assays to measure inflammation, oxidative stress and safety) as well as genetic assessments (telomere length and several Single Nucleotide Polymorphisms). The primary aim is to investigate the effects of these supplements on cognitive performance. The secondary aims are to explore the time-course of cognitive enhancement as well as potential cardiovascular and biochemical mechanisms underpinning cognitive enhancement over the 12 months of administration. ARCLI will represent one of the largest and most comprehensive experimental clinical trials in which supplements are administered to elderly participants. Results from ARCLI may help develop novel preventative health practices and nutritional/pharmacological targets in the elderly for cognitive and brain health.

Trial registration

Australia and New Zealand Clinical Trials Register (ANZCTR): ACTRN12611000487910     

Controlled partial neutralization of amphoteric ion exchange resin for improved metals separation

Controlled partial neutralization of an amphoteric aminomethylphosphonium functional ion exchange resin (Lewatit TP-260) was investigated. The particular goal of controlled neutralization was to replace H⁺ in the acidic phosphonium groups with Na⁺ ions but leave the basic amino groups protonated. In this manner, metals’ sorption is enhanced and undesired pH changes during the metal separation process are avoided. The conjugate bases of organic weak acids (sodium formiate, sodium acetate and sodium citrate), sodium phosphate and NaOH were studied as neutralizing agents. The organic acid salts and sodium phosphate were all found to be suitable. Lengthening the neutralization cycle and using more concentrated neutralization agents were found to yield higher extents of neutralization and more uniform profiles along a resin bed. Concentrated NaOH also neutralized the amine group from the resin. With dilute NaOH, desired extent of neutralization was not achieved within a reasonable time. The effect of partial neutralization on metal sorption was tested with dynamic single column experiments. 5.5 BV of Ag–NaCl solution could be purified from Ca, Mg, Pb and Zn when the resin was partially neutralized with 2.0 M NaAc. With the acid form resin, the impurity metals broke through at 1.0 BV.