Performance calculations of residential cooling systems for simplified energy analysis

The seasonal performance of space cooling systems generally depends on indoor and outdoor temperatures and humidities and on the ratio between actual cooling loads and cooling equipment size. In principle, any given weather condition and desired indoor dry-bulb temperature calls for an interactive application of psychrometrics and equipment performance curves until satisfactory indoor conditions are derived for which both sensible and latent cooling loads equal sensible and latent heat removal rates. This paper presents a simplified approach that derives the indoor wet-bulb temperature in close form for both cases when the cooling system condenses water from the space and when it does not. This approach relies on a local linearization of the psychrometric chart in the region of interest for indoor comfort conditions. Performance curves for total and sensible capacity and for the electric power input were derived for several different residential air-to-air reciprocating compressive cooling systems. The performance curves are empirical fits to manufacturer's data or to laboratory results. The predictions of the simplified method were compared with DOE-2 when calculating space cooling consumption for a residence in both a hot arid and in a hot humid climate. The comparison showed excellent agreement both for hour-by-hour calculations and for monthly calculation of this method are sufficiently simple to be applicable to micro-computers and pocket calculators.     

A dynamic reanalysis technique for general structural modifications under deterministic or stochastic input

A procedure for the dynamic reanalysis of linear systems subjected to deterministic or stochastic loads is presented. The procedure allows to evaluate the dynamic response of the modified structural system starting from the knowledge of the transition matrix and the eigenvectors of the original system. The case in which topological modifications are introduced can be successfully treated. The method relays on an unconditionally stable step-by-step procedure based on the “dynamic modification method”. As shown in the numerical applications, the technique is computationally effective and leads to accurate results for a broad class of structural modifications.     

Distinct Expression Patterns of Cxcl12 in Mesenchymal Stem Cell Niches of Intact and Injured Rodent Teeth

Specific stem cell populations within dental mesenchymal tissues guarantee tooth homeostasis and regeneration throughout life. The decision between renewal and differentiation of stem cells is greatly influenced by interactions with stromal cells and extracellular matrix molecules that form the tissue specific stem cell niches. The Cxcl12 chemokine is a general marker of stromal cells and plays fundamental roles in the maintenance, mobilization and migration of stem cells. The aim of this study was to exploit Cxcl12-GFP transgenic mice to study the expression patterns of Cxcl12 in putative dental niches of intact and injured teeth. We showed that endothelial and stromal cells expressed Cxcl12 in the dental pulp tissue of both intact molars and incisors. Isolated non-endothelial Cxcl12⁺ dental pulp cells cultured in different conditions in vitro exhibited expression of both adipogenic and osteogenic markers, thus suggesting that these cells possess multipotent fates. Taken together, our results show that Cxcl12 is widely expressed in intact and injured teeth and highlight its importance as a key component of the various dental mesenchymal stem cell niches.     

Excretion of benzoic acid derivatives in urine of sheep given intraruminal infusions of 3-phenylpropionic and cyclohexanecarboxylic acids

The quantitative relationship between the urinary excretion of benzoic acid (BA) and the uptake of 3-phenylpropionic (PPA) and cyclohexanecarboxylic (CHCA) acids was assessed. PPA and CHCA are produced in the rumen by microbial fermentation of lignocellulosic feeds and metabolized, after absorption, to BA which is excreted in the urine mainly as its glycine conjugate hippuric acid (HA). Four sheep nourished by intragastric infusions of all nutrients were given continuous ruminal infusions of PPA (8, 16 or 24 mmol/d) either alone or with CHCA (8 or 16 mmol/d) in a factorial experiment. The treatments were allocated to ten consecutive 6 d periods, with a control being repeated at periods 1, 5 and 10. PPA and CHCA ruminal absorption rates, estimated using the liquid-phase marker Cr-EDTA, were 0.78 (SD 0.29)/h and 0.88 (SD 0.28)/h respectively. For the control, HA excretion was only 0.22 (SD 0.33) mmol/d and free BA was absent. For the other treatments, both HA and free BA were present and HA accounted for 0.85 (SD 0.05) of total BA: The urinary excretion of total BA showed a significant linear correlation (r = 0.997, P < 0.001) with the amounts of PPA and CHCA infused. The urinary recovery of infused PPA and CHCA as total BA was 0.79 (SE 0.01). Faecal excretion of BA and its precursors was negligible. Results of this study show that urinary total BA is a potential estimator of the absorption of PPA + CHCA produced in the rumen.     

A probabilistic model for interactive decision-making

A probabilistic reasoning model is defined where the decision maker (d.m.) is engaged in a sequential information-gathering process facing the trade-off between the reliability of the achieved solution and the associated observation cost. The d.m. is directly involved in the proposed flexible control strategy, which is based on information-theoretic principles. The devised strategy works on a Bayesian belief network that allows the efficient representation and manipulation of the knowledge base relevant to the problem domain. It is shown that this strategy guarantees a constant factor approximate solution with respect to the optimum of the decision problem. Some application examples are also discussed.     

Protection and composition of crossmedia content in collaborative environments

Multimedia Tools and Applications - A large range of new applications are appearing nowadays on the Web in which content and data produced by single users or groups are going to be adapted,...