419 research outputs found
Heterogeneous condensation of the Lennard-Jones vapor onto a nanoscale seed particle
The heterogeneous condensation of a Lennard-Jones vapor onto a nanoscale seed
particle is studied using molecular dynamics simulations. Measuring the
nucleation rate and the height of the free energy barrier using the mean first
passage time method shows that the presence of a weakly interacting seed has
little effect on the work of forming very small cluster embryos but accelerates
the rate by lowering the barrier for larger clusters. We suggest that this
results from a competition between the energetic and entropic features of
cluster formation in the bulk and at the heterogeneity. As the interaction is
increased, the free energy of formation is reduced for all cluster sizes. We
also develop a simple phenomenological model of film formation on a small seed
that captures the general features of the nucleation process for small
heterogeneities. A comparison of our simulation results with the model shows
that heterogeneous classical nucleation theory provides a good estimate of the
critical size of the film but significantly over-estimates the size of the
barrier.Comment: 9 pages, 10 figures, In Print J. Chem. Phy
Desiccation and Cracking Behavior of Three Compacted Landfill Liner Soils
Tests were conducted to investigate desiccation cracking of three compacted liner soils obtained from local landfills in southeast Michigan. The soils had low plasticity with varying fines content. Large-scale samples of the soils were subjected to wetting and drying cycles. Surficial dimensions of cracks and suction in the soils were monitored. Surficial dimensions of cracks were quantified using the crack intensity factor (CIF), which is the ratio of the surface area of cracks to the total surface area of a soil. All of the soils were subjected to a compaction–dry cycle (i.e. soils were allowed to dry after compaction) and a subsequent wet–dry cycle. An additional sample of one of the soils was subjected to a compaction–dry cycle and three wet–dry cycles. The maximum CIF obtained in the tests was 7% and suctions exceeding 6000 kPa were recorded. It was observed that cracking was affected by the fines content of the soils. In general, high suctions, rapid increases in suctions, and high amount of cracking were observed in soils with high fines content, with less cracking observed in soil with low fines content. In addition, it was observed that cracking increased significantly due to addition of moisture to the soils. The CIF for wet–dry cycles were significantly greater than the CIF for compaction–dry cycles. Subsequent to moisture addition to the soils, critical suctions that caused a significant change in CIF during the drying cycles were wet–dry cycles, the amount of cracking did not change significantly after the second cycle
Pattern and Outcome of Chest Injuries at Bugando Medical Centre in Northwestern Tanzania.
Chest injuries constitute a continuing challenge to the trauma or general surgeon practicing in developing countries. This study was conducted to outline the etiological spectrum, injury patterns and short term outcome of these injuries in our setting. This was a prospective study involving chest injury patients admitted to Bugando Medical Centre over a six-month period from November 2009 to April 2010 inclusive. A total of 150 chest injury patients were studied. Males outnumbered females by a ratio of 3.8:1. Their ages ranged from 1 to 80 years (mean = 32.17 years). The majority of patients (72.7%) sustained blunt injuries. Road traffic crush was the most common cause of injuries affecting 50.7% of patients. Chest wall wounds, hemothorax and rib fractures were the most common type of injuries accounting for 30.0%, 21.3% and 20.7% respectively. Associated injuries were noted in 56.0% of patients and head/neck (33.3%) and musculoskeletal regions (26.7%) were commonly affected. The majority of patients (55.3%) were treated successfully with non-operative approach. Underwater seal drainage was performed in 39 patients (19.3%). One patient (0.7%) underwent thoracotomy due to hemopericardium. Thirty nine patients (26.0%) had complications of which wound sepsis (14.7%) and complications of long bone fractures (12.0%) were the most common complications. The mean LOS was 13.17 days and mortality rate was 3.3%. Using multivariate logistic regression analysis, associated injuries, the type of injury, trauma scores (ISS, RTS and PTS) were found to be significant predictors of the LOS (P < 0.001), whereas mortality was significantly associated with pre-morbid illness, associated injuries, trauma scores (ISS, RTS and PTS), the need for ICU admission and the presence of complications (P < 0.001). Chest injuries resulting from RTCs remain a major public health problem in this part of Tanzania. Urgent preventive measures targeting at reducing the occurrence of RTCs is necessary to reduce the incidence of chest injuries in this region
Parking as a loss leader at shopping malls
This paper investigates the pricing of malls in an environment where shoppers choose between a car and public transportation in getting to a suburban mall. The mall implicitly engages in mixed bundling; it sells goods bundled with parking to shoppers who come by car, and only goods to shoppers who come by public transportation. There are external costs of discomfort in public transportation due to crowdedness. Thus, shoppers using public transportation deter each other. The mall internalizes these external costs, much like a policy maker. To do so, it raises the sales price of the good and sets a parking fee less than parking's marginal cost. Hence, parking is always a loss leader. Surprisingly, this pricing scheme is not necessarily distortionary. © 2016 Elsevier Ltd
Investigation of cytotoxic effect of black mulberry (Morus nigra L.) fruit
54-58The aim of this study was to determine the cytotoxic effect of black mulberry fruit extract (Morus nigra L.) on human breast cancer (MDA-MB-231) and prostate cancer (PC3) cell lines. The extract prepared from mulberry (M. nigra) fresh fruit was applied to cancer cell lines in 5 different v/v concentrations (10%, 4%, 2%, 1.33% and 1%) for 72 h. At the end of the incubation period, cell viability was determined by MTT [3- (4,5-dimethylthiazol-2-yl) -2,5-diphenyltetrazolium bromide] assay. Results were compared with negative and positive control groups. The effect of mulberry (M. nigra) fruit extract on cell viability was determined depending on the concentration applied; extract showed a significant cytotoxic effect on PC3 cell line at the 10% concentration compared to the control group, but not detected any effect at 4%, 2%, 1.33% and 1% concentrations. In the MDA-MB-231 cell line, there was a high cytotoxic effect at a concentration of 10% compared to the control group, while a lower effect was observed at 4%, 2%, 1.33% and 1% concentrations. The data obtained from the study showed that extract prepared from black mulberry fruit has cytotoxic effect especially against breast cancer cells
Use of polyethylene glycol coatings for optical fibre humidity sensing
Humidity induced change in the refractive index and thickness of the polyethylene glycol (PEG) coatings are in situ investigated for a range from 10 to 95%, using an optical waveguide spectroscopic technique. It is experimentally demonstrated that, upon humidity change, the optical and swelling characteristics of the PEG coatings can be employed to build a plastic fibre optic humidity sensor. The sensing mechanism is based on the humidity induced change in the refractive index of the PEG film, which is directly coated onto a polished segment of a plastic optical fibre with dip-coating method. It is observed that PEG, which is a highly hydrophilic material, shows no monotonic linear response to humidity but gives different characteristics for various ranges of humidity levels both in index of refraction and in thickness. It undergoes a physical phase change from a semi-crystal line structure to a gel one at around 80% relative humidity. At this phase change point, a drastic decrease occurs in the index of refraction as well as a drastic increase in the swelling of the PEG film. In addition, PEG coatings are hydrogenated in a vacuum chamber. It is observed that the hydrogen has a preventing effect on the humidity induced phase change in PEG coatings. Finally, the possibility of using PEG coatings in construction of a real plastic fibre optic humidity sensor is discussed. (C) 2008 The Optical Society of Japan
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