Polyurethane foam based packing media for biofilters removing volatile organic compounds from contaminated air

In recent years, biofiltration technology has gained acceptance worldwide as an economical and reliable air pollution control technology for treating gases contaminated by low concentrations of biodegradable volatile organic compounds (VOCs). Important applications include control of odors generated by wastewater treatment plants and control of VOC emissions from industrial sources. Although there have been many successful applications, several operational problems have been reported in the literature. These include difficulty in control over bed moisture content, high head loss caused by excessive biomass production, and inability to maintain removal efficiency during transient periods of high concentration loading. Use of a superior packing medium may be able to mitigate these difficulties. The research described herein was directed toward development and evaluation of novel biofilter packing media for use in aerobic biodegradation of VOCs present in contaminated air. Several types of media comprised of polyurethane foam and powdered activate (PAC) were manufactured and tested for suitability as biofilter packing media. Experiments were conducted to determine the media’s porosity, head loss, chemical resistance, and sorption capacity for several VOCs commonly present in industrial waste gases. Compounds tested included toluene, p-xylene, methyl ethyl ketone (MEK), and 4-methyl-2-pentanone (MIBK). These compounds are commonly used solvents that are found in the off-gases of many industrial processes including painting operations. Batch sorption experiments were conducted for equilibrium conditions (serum bottle studies), and fixed-bed studies were conducted for dynamic loading conditions (column studies). Appropriate mathematical models were applied to describe adsorption and desorption behavior of polyurethane foam for the VOCs tested. Bed depth service time analysis was used to predict the performance of the reactor under different experimental conditions. Results reported herein indicate that polyurethane foam containing activated carbon contains the properties desirable for biofilter packing media. Such media are promising candidates for use in biofilters that are operated using sequencing batch operation

Constraints on the braneworld from compact stars

According to the braneworld idea, ordinary matter is confined on a 3-dimensional space (brane) that is embedded in a higher-dimensional space-time where gravity propagates. In this work, after reviewing the limits coming from general relativity, finiteness of pressure and causality on the brane, we derive observational constraints on the braneworld parameters from the existence of stable compact stars. The analysis is carried out by solving numerically the brane-modified Tolman-Oppenheimer-Volkoff equations, using different representative equations of state to describe matter in the star interior. The cases of normal dense matter, pure quark matter and hybrid matter are considered.Comment: 13 pages, 11 figures, 2 tables; new EoS considered, references and comments adde

The Future of Retail Operations

Retailing consists of all the activities associated with the selling of goods to the final consumer. In this article, we review the research on retail operations published in Manufacturing & Service Operations Research (M&SOM) since 1999. We then discuss the current retail landscape and the new research directions it offers, in which M&SOM can play a prominent role

Magnetized strange quark matter and magnetized strange quark stars

Strange quark matter could be found in the core of neutron stars or forming strange quark stars. As is well known, these astrophysical objects are endowed with strong magnetic fields which affect the microscopic properties of matter and modify the macroscopic properties of the system. In this paper we study the role of a strong magnetic field in the thermodynamical properties of a magnetized degenerate strange quark gas, taking into account beta-equilibrium and charge neutrality. Quarks and electrons interact with the magnetic field via their electric charges and anomalous magnetic moments. In contrast to the magnetic field value of 10^19 G, obtained when anomalous magnetic moments are not taken into account, we find the upper bound B < 8.6 x 10^17 G, for the stability of the system. A phase transition could be hidden for fields greater than this value.Comment: 9 pages, 9 figure

Benchmarking International Food Safety Performance in the Fresh Produce Sector

The objective of this paper is to assess food systems performance in Mediterranean countries to deliver safe food (fresh produce), and to demonstrate the capacity to the satisfaction of private customers and public regulators. To that end, an international benchmarking exercise was developed to assess the quality performance gap in food standards across countries and food systems. The study was carried out in three Mediterranean countries: Spain, Morocco and Turkey and involved an audit of the citrus and tomatoes supply chains, and a comparison with existing "best practice" in infrastructure and management practices at both firm and industry level. The aim was to identify the gaps between fresh produce exporters and a best practice company. To that end, the Spanish fresh produce supply chain was used as the benchmark since in many areas it is more advanced than elsewhere.benchmarking, performance, quality and safety, fresh produce, Mediterranean countries, Food Consumption/Nutrition/Food Safety,