Performance of liquid convective diodes

A three year study has been conducted concerned with the operation of convective heat diodes—passive solar heating devices which absorb and accumulate solar energy and then transport heat preferentially to the inside of a building. The study has been carried out in Gliwice, Poland (latitude 50° north, longitude 19° east), in a strongly industrialized region with a considerable level of air pollution.A module was built that consisted of four overlapping thermal diodes made of plastics. It has been found that the diodes, which constitute only 6% of the test cell surface area, lead to energy savings as high as 37% compared with the reference cells. This corresponds to some 700 MJ of energy per 1 m² of the diode per year. Based on the experimental results, the parameters have been estimated which appear in the energy balance equations for the diodes. It has been concluded that it is the thermal resistance of the insulation between the accumulator of one diode and the collector of another which has a crucial effect upon the efficiency of the diode, and appropriate improvements to present-day diode designs have been suggested.     

The Composition of the Cuticular and Internal Free Fatty Acids and Alcohols from <Emphasis Type="Italic">Lucilia sericata</Emphasis> Males and Females

GC, GC-MS, and HPLC-LLSD analyses were used to identify and quantify cuticular and internal lipids in males and females of the blow-fly (Lucilia sericata). Sixteen free fatty acids, seven alcohols and cholesterol were identified and quantitatively determined in the cuticular lipids of L. sericata. Cuticular fatty acids ranged from C(6) to C(20) and included unsaturated entities such as 16:1n-9, 18:1n-9, 20:4n-3 and 20:5n-3. Cuticular alcohols (only saturated and even-numbered) ranged from C(12) to C(20) in males and C(10) to C(22) in females. Only one sterol was found in the cuticular lipids of both males and females. 23 free fatty acids, five alcohols and cholesterol were identified in the internal lipids. Internal fatty acids were present in large amounts-7.4 mg/g (female) and 10.1 mg/g (male). Only traces of internal alcohols (from C(14) to C(26) in males, from C(14) to C(22) in females) were found in L. sericata. Large amounts of internal cholesterol were identified in L. sericata males and females (0.49 and 0.97 mg/g of the insect body, respectively).     

A branch-and-bound parallel algorithm for single-machine total weighted tardiness problem

This paper presents the branch-and-bound algorithm for the single-machine total weighted tardiness problem. Among exact solution approaches, the branch-and-bound algorithm from Potts and Van Wassenhove solves problems of up to 40 jobs and the algorithm from Babu et al. for 50 jobs (not for all instances). We have taken advantage of the properties of permutation broken into blocks. These properties are much stronger than elimination criteria (Potts CN, Van Wassenhove LN, 1991. IIE Trans 23:346–354; Rinnoy Kan AGH, Lageweg BJ, Lenstra JK 1975 Minimizing total cost one-machine scheduling. Oper Res 26:908–972) applied so far and they allow us to eliminate many branches of the solution tree. Parallel implementation of the algorithm enables us to reduce computational time significantly and to solve larger problems. We have tested the algorithms on randomly generated instances (of up to 80 jobs) and benchmark instances taken from the OR-Library [4]. The solutions obtained have been compared with the results yielded by the best algorithms discussed in the literature. The results show that the proposed algorithm solves the problem instances with high accuracy in a very short time.     

Double Bond Stereochemistry Influences the Susceptibility of Short-Chain Isoprenoids and Polyprenols to Decomposition by Thermo-Oxidation

Isoprenoid alcohols are common constituents of living cells. They are usually assigned a role in the adaptation of the cell to environmental stimuli, and this process might give rise to their oxidation by reactive oxygen species. Moreover, cellular isoprenoids may also undergo various chemical modifications resulting from the physico‐chemical treatment of the tissues, e.g., heating during food processing. Susceptibility of isoprenoid alcohols to heat treatment has not been studied in detail so far. In this study, isoprenoid alcohols differing in the number of isoprene units and geometry of the double bonds, β‐citronellol, geraniol, nerol, farnesol, solanesol and Pren‐9, were subjected to thermo‐oxidation at 80 °C. Thermo‐oxidation resulted in the decomposition of the tested short‐chain isoprenoids as well as medium‐chain polyprenols with simultaneous formation of oxidized derivatives, such as hydroperoxides, monoepoxides, diepoxides and aldehydes, and possible formation of oligomeric derivatives. Oxidation products were monitored by GC‐FID, GC‐MS, ESI‐MS and spectrophotometric methods. Interestingly, nerol, a short‐chain isoprenoid with a double bond in the cis (Z) configuration, was more oxidatively stable than its trans (E) isomer, geraniol. However, the opposite effect was observed for medium‐chain polyprenols, since Pren‐9 (di‐trans‐poly‐cis‐prenol) was more susceptible to thermo‐oxidation than its all‐trans isomer, solanesol. Taken together, these results experimentally confirm that both short‐ and long‐chain polyisoprenoid alcohols are prone to thermo‐oxidation.     

Decomposition of methane in the presence of ethanol over activated carbon catalyst

The interest in hydrogen as a potential fuel of the future has stimulated development of new technologies of its production. The main method of hydrogen production is based on the process of steam reforming of methane, but recently increasing attention has been paid to the catalytic decomposition of methane (CDM) whose advantage is its pro-ecological character. This reaction, besides hydrogen, produces also catalytically low-active carbonaceous deposit which settles on the surface of the catalyst and leads to its deactivation. The study reported is an attempt at suppressing the catalyst deactivation by developing a method leading to formation of carbonaceous deposit potentially active in CDM process. For this purpose, it was proposed that the reaction system would contain methane and ethanol. Simultaneous decomposition of these two substances was performed in parallel at three temperatures of 750, 850 or 950 °C. The catalyst was activated carbon obtained from the hazelnut shells. The addition of ethanol was found to have a positive effect on the course of CDM, leading to an increase in the amount of hydrogen produced and to stabilisation of the catalyst activity at a high level.