On some properties of the bathtub failure rate family of life distributions

In this paper, some of the basic issues concerning the bathtub failure rate (BFR) life distributions, thus far unresolved, have been investigated. Specifically, exponential bounds have been obtained for the survival function as well as the moments of a BFR distribution. Closure properties of the BFR family under the formation of coherent systems, convolutions and mixtures have been dealt with. Closure of the BFR class under the formation of limits in distribution and the equivalence of weak convergence and convergence of moment sequences have been established.     

Site-specific frame-shift mutagenesis by the 1-nitropyrene-DNA adduct N-(deoxyguanosin-8-y1)-1-aminopyrene located in the (CG)3 sequence: effects of SOS, proofreading, and mismatch repair

1-Nitropyrene (1-NP), the predominant nitropolycyclic hydrocarbon found in diesel exhaust, is a mutagen and tumorigen. Nitroreduction is a major pathway by which 1-NP is metabolized. Reductively activated 1-NP forms a major DNA adduct, N-(deoxyguanosin-8-yl)-1-aminopyrene (dGAP), both in vitro and in vivo. In Salmonella typhimurium 1-NP induces a CpG deletion in a CGCGCGCG sequence. In Escherichia coli, however, mostly -1 and +1 frame-shifts are observed, which occur predominantly in 5'-CG, 5'-GC, and 5'-GG sequences. In order to determine the mechanism of mutagenesis by dGAP in a CpG repetitive sequence, we constructed a single-stranded M13 genome containing the adduct at the underscored deoxyguanosine of an inserted CGCGCG sequence. In E. coli strains with normal repair capability the adduct induced approximately 2% CpG deletions, which was 20-fold that of the control. With SOS, the frequency of frame-shift mutations increased to 2.6%, even though the frequency of CpG deletion accompanied 50% reduction. The enhancement in mutagenesis was due to a +1 frame-shift that occurred at a high frequency. In strains with a defect in methyl-directed mismatch repair, 50-70% increase in mutation frequency was observed. When these strains were SOS induced, frame-shift mutagenesis increased by approximately 100%. When transfections were carried out in dnaQ strains that are impaired in 3'-->5'exonuclease activity of DNA polymerase III, frame-shift mutagenesis increased 5-7-fold. dGAP-induced frame-shifts in the (CG)3 sequence, therefore, varied from 2% to 17% depending on the state of repair of the host cells. We conclude that dGAP induces both -2 and +1 frame-shifts in a CpG repetitive sequence and that these two mutagenic events are competing pathways. The CpG deletion does not require SOS functions, whereas the +1 frame-shifts are SOS-dependent. On the basis of the data in repair-deficient strains, it appears that both types of frame-shifts occurred as a result of misalignment, which are corrected primarily by the proofreading exonuclease of the DNA polymerase. Misaligned structures that escape the exonuclease are repaired by the methyl-directed mismatch repair, albeit with limited efficiency.     

Simulating convective die heating for forgings and pressure casting

A comparison is made of die temperature uniformity for two heating configurations: electric air heating and flame heating. The temperature uniformity with electric air heating is noted to be substantially superior to flame heating of large dies. The simulation results are compared with experimentally obtained numbers and found to be in agreement.     

Preparation of glycol derivatives of partially hydrogenated soybean oil fatty acids and their potential as lubricants

The online version of the original article can be found at     

Assimilation of altimeter significant wave height into a third-generation global spectral wave model

Data from three different altimeters (Topex/Poseidon, Jason-1, and European Remote Sensing Satellite 2) have been assimilated in a third-generation global spectral wave model forced by winds observed by scatterometer onboard QuikSCAT. Two different approaches of assimilation have been discussed. In the first approach, a simple scaling has been used to generate wave spectrum from altimeter-derived significant wave heights for assimilation in the model. In the second approach, the influence of altimeter observation has been spread to nearby grid points. Assimilation has been carried out every 6 h for five days. After the expiry of the assimilation phase, the model has been run in pure hindcast mode. Assimilation experiments have been carried out for the months of September and December 2002. Impact of assimilation has been found to be quite high in the Indian Ocean. It has been also found that the model is able to retain the memory of assimilation for a period of two and a half days as far as global ocean is concerned. This memory is more for the Indian Ocean. The wave spectrum generated by the model in the hindcast mode has been validated against the buoy-observed wave spectrum in the high sea conditions. The more significant impact has been seen in the case of altimeter track in the vicinity of the buoy.     

Low temperature heat capacity measurements on HoBa2Cu3O7−δ

Specific heats were measured on two samples of HoBa₂Cu₃O_7−δ in the temperature range 1·7 K to 10 K. In addition to the known Schottky behaviour, a peak in the specific heat curve was observed near 7·9 K in both the samples. This peak is probably due to impurity contribution and the specific heat measurements were undertaken in holmium oxide (Ho₂O₃), which was the suspected impurity. However, no peak was observed in the specific heat curve of holmium oxide     

Merox and Related Metal Phthalocyanine Catalyzed Oxidation Processes

Alkyl and aromatic mercaptans are among important organic sulfur compounds distributed in petroleum products. The mercaptans cause foul odor and are corrosive toward metals. In addition, mercaptans may cause oxidative deterioration as well as inhibit the performance of various additives (TEL, antioxidants) in finished products. Therefore, it is necessary to remove them, either by extractive processes or by converting them into innocuous disulfides. Such processes are usually referred to as “sweetening.”     

Numerical and experimental analysis of nonradiative dielectric guide modulator and mixer at Ka band

This letter describes the numerical analysis of an on/off modulator and a single-ended mixer in nonradiative dielectric (NRD) guide configuration at Ka band. Currently, only experimental results are available for such structures. A shunt mounted diode switch in NRD guide configuration is analyzed using the finite element method (FEM) in conjunction with linear circuit simulation. A novel mixer is similarly analyzed using FEM and harmonic balance analysis. The results obtained from numerical analysis are compared with measured results. It is demonstrated that some counter-intuitive experimental results can be explained through numerical analysis.