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.     

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.     

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.     

The repeatability of automated and clinician refraction

The development of new generation vaccines has focused on the use of natural immunologic adjuvants that are capable of enhancing a protective immune response. The use of cytokines as immunomodulators in livestock animals, particularly poultry, is becoming more feasible with the recent cloning of several cytokine genes and the progression of new delivery technologies, such as live vectors and DNA delivery. Given that chickens are reared under intensive conditions that are conducive to infection by opportunistic pathogens, the primary mechanism for disease control in poultry is early and effective vaccination. However, many poultry vaccines offer only short-term protection or give nonuniform responses within flocks. We have developed a model system with which to measure the adjuvant potential of cytokines in chickens. This involves measuring antibody levels following coadministration of chicken interferon-gamma (Ch-IFN-gamma) with sheep red blood cells (SRBC). Groups of SPF and commercial broiler birds were injected with two different doses of SRBC with and without coadministration of Ch-IFN-y. Three weeks later, all birds were boosted with SRBC alone. Sera were collected weekly and anti-SRBC antibody titers (total Ig and IgG) were determined by hemagglutination. Priming Ch-IFN-gamma resulted in enhanced primary and secondary (IgG) antibody responses that persisted at higher levels when compared with birds that received SRBC alone. Second, coadministration of Ch-IFN-y allowed a 10-fold lower dose of antigen to be as effective as a high dose of antigen that was given without Ch-IFN-gamma. Third, treatment with Ch-IFN-y resulted in an increase in the proportion of birds responding to antigen challenge. These results suggest the potential use for Ch-IFN-gamma as a vaccine adjuvant.     

Some Observations of Diatoms Under Turbulence

The effect of turbulence on several freshwater diatom taxa was investigated and our findings are described herein. We have compared diatom morphology in shallow natural systems that experience turbulence due to wind and in river/waterfall systems where turbulence is due to high flow rates. We have also introduced turbulence into diatom laboratory cultures by mechanical shaking and by forcing air into the media. In particular, we have studied diatoms in five independent environments or cultures: the freshwater diatoms Tabellaria and Eunotia in equatorial lakes experiencing extreme seasonal variability in depth; two freshwater diatom monocultures of Aulacoseira granulata var angustissima and Melosira varians in the laboratory; and a freshwater diatom community possessing equal amounts (by number) of elongated and non-elongated diatoms (mostly Nitzschia and mostly Cyclotella, respectively) in the laboratory. We have demonstrated the effect of turbulence on freshwater diatom frustule morphologies and, perhaps more importantly, the effect of turbulence on freshwater diatom species population after controlled perturbation of the organisms’ environment. It has been widely reported that symmetry is often preferred in biological evolution, however here we have observed a preference towards asymmetry for the survival of diatoms in the presence of environmental stress (in particular, turbulence). We also note that to date there have been no systematic attempts to manipulate diatom frustules using external stimuli. We therefore present a proof-of-concept study in order to demonstrate: (i) that diatom morphologies can be manipulated by controlled simple external triggers (chemical and physical) (ii) that population balance (i.e. natural selection) can be controlled via simple external triggers (chemical and physical). This approach could open up an entire new field of future studies wherein controlled environmental perturbations are used to manipulate the structure, form, growth and reproduction of biological species.     

Mechanisms of graphite fluoride [(CFx)n] lubrication

Friction, wear and wear life results were compared with optical microscope observations as a function of sliding distance for graphite fluoride rubbed films applied to three surface finishes — polished, sanded and sandblasted. The lubricating process consisted of the plastic flow of thin films of graphite fluoride between flat areas on the rider and on the metallic substrate. If the substrate was rough, flat areas were created during run-in, and the [(CF_x)_n] flowed across them. Wear life was enhanced by restricting radial (or transverse) flow of the graphite fluoride from the contact region by increasing surface roughness. Valleys in the roughened substrate surface served as a reservoir for graphite fluoride and as a deposit site for wear debris. Failure resulted from the gradual depletion of graphite fluoride from the contact region with the subsequent formation of powdery metallic debris that covered both rider and disk surfaces.