Puff Characteristics Research Articles

Equations of a new puff model for idealized urban canopy

During a leakage of hazardous materials, emergency services need to predict the evolution of the accident. In such situations, fast models are used. Such models can produce reasonable results for long-term leakages, but short-term leakage results can be underestimated by as much as a full order of magnitude (shown in the COST ES1006 project). Hence, the main aim of this paper is to present equations for recalculating the continuous source results to achieve results valid for the short-term source. The model would consist of a sub-model utilized for the continuous source in combination with the equations introduced in the paper. The outputs obtained are the probability density functions of the puff characteristics: dosage, maximum concentration, and 99th and 95th percentiles of concentrations. These functions can help to estimate the situation not only for the mean case, but also for the extreme cases.

Sensitivity of puff characteristics to maximum-concentration-based definition of departure time

During a hazardous situation, its dangerousness has to be estimated. An important category of such situations is the one in which hazardous gas clouds are released into the atmosphere. The gas clouds are described by their characteristics at exposed locations. But their values are usually dependent on the parameters utilized in their definitions. Hence, the aim of this paper is to examine how the choice of parameter value in a definition of departure time can affect its value. Moreover, it evaluates how this change influences other characteristics which utilize the departure time in their definitions. To study these situations, wind-tunnel experiments of short-duration gas releases were conducted. The ground-level releases of ethane were performed on a model of an idealised urban canopy. The model was composed of houses with pitched roofs organised into closed courtyards. Concentrations were measured by a fast flame ionisation detector. The experiments were repeated about 400 times at each measurement position to get statistically representative datasets. In the analysis, two departure time definitions, based on a detected maximum concentration with various parameters, were utilized. Moreover, other derived puff characteristics were computed. The results showed that when a suitable range of parameters is used, the differences in mean departure times are significant. In contrast, some other characteristics which use puff departure times in their definitions (e.g. mean dosage) are usually not significantly different.

The Influence of Puff Characteristics, Nicotine Dependence, and Rate of Nicotine Metabolism on Daily Nicotine Exposure in African American Smokers.

African American (AA) smokers experience greater tobacco-related disease burden than Whites, despite smoking fewer cigarettes per day (CPD). Understanding factors that influence daily nicotine intake in AA smokers is an important step toward decreasing tobacco-related health disparities. One factor of interest is smoking topography, or the study of puffing behavior. (i) to create a model using puff characteristics, nicotine dependence, and nicotine metabolism to predict daily nicotine exposure, and (ii) to compare puff characteristics and nicotine intake from two cigarettes smoked at different times to ensure the reliability of the puff characteristics included in our model. Sixty AA smokers smoked their preferred brand of cigarette at two time points through a topography device. Plasma nicotine, expired CO, and changes in subjective measures were measured before and after each cigarette. Total nicotine equivalents (TNE) was measured from 24-hour urine collected during ad libitum smoking. In a model predicting daily nicotine exposure, total puff volume, CPD, sex, and menthol status were significant predictors (R(2) = 0.44, P < 0.001). Total puff volume was significantly greater and inter-puff intervals were significantly shorter after ad lib smoking compared with the first cigarette of the day, but puffing behaviors for both cigarettes were highly correlated (r range = 0.69-0.89, P < 0.001) within-subjects. This is the first study, to our knowledge, to show that puff characteristics of individual cigarettes are predictive of daily nicotine intake. These findings enhance our understanding of the relationship between smoking behavior and nicotine intake in AA smokers. Cancer Epidemiol Biomarkers Prev; 25(6); 936-43. ©2016 AACR.

Short-term gas dispersion in idealised urban canopy in street parallel with flow direction

Chemical attacks (e.g. Syria 2014-15 chlorine, 2013 sarine or Iraq 2006-7 chlorine) as well as chemical plant disasters (e.g. Spain 2015 nitric oxide, ferric chloride; Texas 2014 methyl mercaptan) threaten mankind. In these crisis situations, gas clouds are released. Dispersion of gas clouds is the issue of interest investigated in this paper. The paper describes wind tunnel experiments of dispersion from ground level point gas source. The source is situated in a model of an idealised urban canopy. The short duration releases of passive contaminant ethane are created by an electromagnetic valve. The gas cloud concentrations are measured in individual places at the height of the human breathing zone within a street parallel with flow direction by Fast-response Ionisation Detector. The simulations of the gas release for each measurement position are repeated many times under the same experimental set up to obtain representative datasets. These datasets are analysed to compute puff characteristics (arrival, leaving time and duration). The results indicate that the mean value of the dimensionless arrival time can be described as a growing linear function of the dimensionless coordinate in the street parallel with flow direction where the gas source is situated. The same might be stated about the dimensionless leaving time as well as the dimensionless duration, however these fits are worse. Utilising a linear function, we might also estimate some other statistical characteristics from datasets than the datasets means (medians, trimeans). The datasets of the dimensionless arrival time, the dimensionless leaving time and the dimensionless duration can be fitted by the generalized extreme value distribution (GEV) in all sampling positions except one.

Inositol (1,4,5)-Trisphosphate Receptor Microarchitecture Shapes Ca 2+ Puff Kinetics

Inositol (1,4,5)-trisphosphate receptors (IP 3Rs) release intracellular Ca 2+ as localized Ca 2+ signals (Ca 2+ puffs) that represent the activity of small numbers of clustered IP 3Rs spaced throughout the endoplasmic reticulum. Although much emphasis has been placed on estimating the number of active Ca 2+ release channels supporting Ca 2+ puffs, less attention has been placed on understanding the role of cluster microarchitecture. This is important as recent data underscores the dynamic nature of IP 3R transitions between heterogeneous cellular architectures and the differential behavior of IP 3Rs socialized into clusters. Here, we applied a high-resolution model incorporating stochastically gating IP 3Rs within a three-dimensional cytoplasmic space to demonstrate: 1), Ca 2+ puffs are supported by a broad range of clustered IP 3R microarchitectures; 2), cluster ultrastructure shapes Ca 2+ puff characteristics; and 3), loosely corralled IP 3R clusters (>200 nm interchannel separation) fail to coordinate Ca 2+ puffs, owing to inefficient triggering and impaired coupling due to reduced Ca 2+-induced Ca 2+ release microwave velocity (<10 nm/s) throughout the channel array. Dynamic microarchitectural considerations may therefore influence Ca 2+ puff occurrence/properties in intact cells, contrasting with a more minimal role for channel number over the same simulated conditions in shaping local Ca 2+ dynamics.

Deriving Cellular Ca(2+) Dynamics from Puff Characteristics - A New Approach in Mathematical Modeling

It has recently been shown that Ca(2+) spikes are stochastic and that the Ca(2+) concentration is subject to huge intracellular gradients. These findings underline the need for stochastic models taking single molecule state transitions into account (Master Equations are impossible due to the high number of states). We developed such a modeling concept based on the fact that for cellular concentration dynamics, it is only relevant whether channels are open or closed, but not in which open or closed state they are. That requires a non-Markovian formulation of the theory which we will present. This formulation permits direct integration of measurable quantities into the model, whereas detailed knowledge of physiologic parameters is not necessary. Therefore, input and output can be directly compared with experiments, if we consider observables like the probability that no spike happens or the average spike length. The model covers experimentally observed modes of system behavior like bursting, spiking or local events. Statistic properties of interspike intervals are in good accordance with experimental data. Since we have developed an analytic description as well as an efficient simulation algorithm, we are in a position to analyze a broad range of possible system configurations based on a solid theoretical background. In particular, we find that the spiking pattern can be predicted merely from two parameters, the cluster coupling and the average channel open time. The latter is probably constant and the former can be regulated by second messengers or by the number of active clusters, e. g. This implies that local dynamics emerges to a single control parameter determining global dynamics. Since we expect similar mechanisms to work in various fields of biology (e.g. cAMP dynamics and DNA replication), our theory should be widely applicable.

SENSORY AND PHYSICAL PROPERTIES OF EXTRUDED POTATO PUFFS1

ABSTRACTAlthough extrusion is widely used for snack foods, there are few descriptive sensory analysis studies of extrudates. This study investigated the effects of potato granule type (flour or flakes), feed moisture content (16%, 18% and 20%) and addition of oil (0%, 2% and 4%) on sensory attributes of extrudates. Generalized Procrustes analysis (GPA) and Principal Component analysis (PCA) were used to describe the relationship among the sensory attributes. Additionally, GPA described the relationship between selected sensory and physical variables. Feed moisture content, as a primary factor, and added oil, as the secondary, affected the puff characteristics. High feed moisture puffs were high in hardness and chewiness, whereas low moisture ones were high in brownness, burnt flavor and fracturability. Added oil changed sensory expansion with relation to low feed moisture. Using GPA, physical properties related to appearance, color and texture were matched with corresponding sensory attributes.

Turbulent Line Momentum Puffs

The time evolution of a line puff—a turbulent element with momentum—is studied by numerical simulation of the flow and mixing using a two-equation turbulence model, and by experimental measurements of the scalar concentration field in an advected line puff. The numerical solution reveals a distinct double-vortex flow with a loss of initial impulse due to pressure interaction, and mixing at the front of the puff. The added mass coefficient associated with the loss of impulse is found to be approximately 1. The computed flow and puff characteristics support the concept of self-similarity beyond a dimensionless time of 25–30. The predicted puff flow features and mixing rates are well-supported by experimental observations.

Flame Length Measurements of Burning Fuel Puffs

Abstract An experimental study of burning of natural gas puffs generated by a fully modulated jet, has been conducted. The present study concentrated on the effects of duty-cycle and puff volume, or equivalently the injection time, on the flame length. It is observed that when individual puffs are well-separated, considerably shorter flame lengths, by as much as a factor of four, are obtained compared to a steady jet flame. Furthermore, the flame length of individual puffs scales with the initial volume of puff, in agreement with the previous studies of buoyant puffs in aqueous media. For a given puff volume, as the duty-cycle is increased beyond a given value, the flame length tends to rise rapidly due to the interaction among neighboring puffs. A dimensionless parameter is found which indicates the transition of puff characteristics.

Human smoking patterns and smoke deliveries.

This study, based on a sample (N = 517) of adult medical patients at a southeastern medical center who were current users of cigarettes, reports the interrelationships among the puff characteristics of cigarette smoking behavior and smoke deliveries of tar and nicotine. Average puff duration, average puff volume, and the number of puffs were found to be significantly positively correlated with daily tar and nicotine intake. Intervals between puffs and total time smoking were not correlated with nicotine and tar intake. It was concluded that "how" a person smokes affects "how much" this person is exposed to tar and nicotine.

An Infrared Method for the Determination of Carbon Monoxide and Carbon Dioxide Levels in Cigarette Smoke

AbstractA method for the simultaneous determination of the CO and CO2 concentrations in each puff of a cigarette was developed. Puff characteristics of single and multiport smoking machines were controlled by selection of critical flow orifices. The CO and CO2 were rapidly measured by nondispersive infra-red analysers, which required no wave length scanning and were free from interference by other smoke components. Precision was increased by a six-port head compared to a single port but was not improved by a 12-port head. The procedure has been applied in studies of various commercial and experimental cigarettes