Time-dependent cross ratio estimation for bivariate failure times

In the analysis of bivariate correlated failure time data, it is important to measure the strength of association among the correlated failure times. One commonly used measure is the cross ratio. Motivated by Cox's partial likelihood idea, we propose a novel parametric cross ratio estimator that is a flexible continuous function of both components of the bivariate survival times. We show that the proposed estimator is consistent and asymptotically normal. Its finite sample performance is examined using simulation studies, and it is applied to the Australian twin data.     

Wolbachia in field populations of Forcipomyia taiwana (Diptera: Ceratopogonidae) in Taiwan

Wolbachia pipientis is an endosymbiotic alpha-proteobacterium that is found in numerous insects and arthropods. Only a few studies have been made on Wolbachia in blood-sucking midges. In this study, we identified and determined the molecular characteristics of Wolbachia strains in Forcipomyia taiwana (Shiraki), a blood-sucking midge found in Taiwan and southern China. Our results indicate that all F. taiwana individuals captured in Nantou County, Taiwan were infected with Wolbachia strains closely related to the A-supergroup wAlbA. Moreover, 2 individuals captured at low-abundance locations were also infected with a B-supergroup Wolbachia strain. We observed that 63% F. taiwana individuals captured at the low-abundance locations harbored the wAlbA-like strain which has a particular substitution pattern (D51G, T84A, and A85V) in the Wolbachia surface protein. Taken together, our results indicate that distinct Wolbachia strains exist in F. taiwana populations in the field.     

Invasion of the African sharp-tooth catfish <Emphasis Type=Italic>Clarias gariepinus</Emphasis> (Burchell, 1822) in South China

We record here the invasion of the African sharp-tooth catfish Clarias gariepinus in the South China biodiversity hotspot, an area rich in endemic and endangered fish fauna. C. gariepinus was introduced into the natural systems as escapees from aquaculture ponds. These catfishes are very large, top predators, and thus have the potential to cause serious threats to the native fish fauna. The impact of C. gariepinus needs more investigation with emphasis on developing techniques for controlling its dispersal.     

A modified cornish pasty method for ex ovo culture of the chick embryo development

Chick embryos grown in ex ovo culture by the modified Cornish pasty method reported in Nagai, Lin and Sheng in this issue.     

Can an acoustic observatory contribute to the conservation of threatened species?

Observatories are designed to collect data for a range of uses. The Australian Acoustic Observatory (A2O) was established to collect environmental sound, including audible species calls, from 344 recorders at 86 sites around Australia. We examine the potential of the A2O to monitor near threatened, threatened, endangered and critically endangered species, based on their vocal behaviour, geographic distributions in relation to the sites of the A2O and on some knowledge of habitat use. Using IUCN and EPBC lists of threatened and endangered species, we extracted species that vocalized in the audible range, and using conservative estimates of their geographic ranges, determined whether there was a possibility of hearing them at these sites. We found that it may be possible to detect up to 171 threatened species at sites established for the A2O, and that individual sites have the potential to detect up to 40 threatened species. All 86 sites occurred in locations where threatened species could possibly be detected, and the list of detectable species included birds, amphibians, and mammals. We have incidentally detected one mammal and four bird species in the data during other work. Threatening processes to which potentially detectable species were exposed included all but two IUCN threat categories. We concluded that with applications of technology to search the audio data from the A2O, it could serve as an important tool for monitoring threatened species.     

Efficiency Boost in All-Small-Molecule Organic Solar Cells: Insights from the Re-Ordering Kinetics

Achieving high-performance in all-small-molecule organic solar cells (ASM-OSCs) significantly relies on precise nanoscale phase separation through domain size manipulation in the active layer. Nonetheless, for ASM-OSC systems, forging a clear connection between the tuning of domain size and the intricacies of phase separation proves to be a formidable challenge. This study investigates the intricate interplay between domain size adjustment and the creation of optimal phase separation morphology, crucial for ASM-OSCs’ performance. It is demonstrated that exceptional phase separation in ASM-OSCs’ active layer is achieved by meticulously controlling the continuity and uniformity of domains via re-packing process. A series of halogen-substituted solvents (Fluorobenzene, Chlorobenzene, Bromobenzene, and Iodobenzene) is adopted to tune the re-packing kinetics, the ASM-OSCs treated with CB exhibited an impressive 16.2% power conversion efficiency (PCE). The PCE enhancement can be attributed to the gradual crystallization process, promoting a smoothly interconnected and uniformly distributed domain size. This, in turn, leads to a favorable phase separation morphology, enhanced charge transfer, extended carrier lifetime, and consequently, reduced recombination of free charges. The findings emphasize the pivotal role of re-packing kinetics in achieving optimal phase separation in ASM-OSCs, offering valuable insights for designing high-performance ASM-OSCs fabrication strategies.     

A New Statistic to Evaluate Imputation Reliability

Background

As the amount of data from genome wide association studies grows dramatically, many interesting scientific questions require imputation to combine or expand datasets. However, there are two situations for which imputation has been problematic: (1) polymorphisms with low minor allele frequency (MAF), and (2) datasets where subjects are genotyped on different platforms. Traditional measures of imputation cannot effectively address these problems.

Methodology/Principal Findings

We introduce a new statistic, the imputation quality score (IQS). In order to differentiate between well-imputed and poorly-imputed single nucleotide polymorphisms (SNPs), IQS adjusts the concordance between imputed and genotyped SNPs for chance. We first evaluated IQS in relation to minor allele frequency. Using a sample of subjects genotyped on the Illumina 1 M array, we extracted those SNPs that were also on the Illumina 550 K array and imputed them to the full set of the 1 M SNPs. As expected, the average IQS value drops dramatically with a decrease in minor allele frequency, indicating that IQS appropriately adjusts for minor allele frequency. We then evaluated whether IQS can filter poorly-imputed SNPs in situations where cases and controls are genotyped on different platforms. Randomly dividing the data into “cases” and “controls”, we extracted the Illumina 550 K SNPs from the cases and imputed the remaining Illumina 1 M SNPs. The initial Q-Q plot for the test of association between cases and controls was grossly distorted (λ = 1.15) and had 4016 false positives, reflecting imputation error. After filtering out SNPs with IQS<0.9, the Q-Q plot was acceptable and there were no longer false positives. We then evaluated the robustness of IQS computed independently on the two halves of the data. In both European Americans and African Americans the correlation was >0.99 demonstrating that a database of IQS values from common imputations could be used as an effective filter to combine data genotyped on different platforms.

Conclusions/Significance

IQS effectively differentiates well-imputed and poorly-imputed SNPs. It is particularly useful for SNPs with low minor allele frequency and when datasets are genotyped on different platforms.     

Production of cellulolytic enzymes from theXylaria andHypoxylon species of xylariaceae

Eighteen strains of xylariaceous fungi have been screened for higher activities of cellulolytic enzymes,Trichoderma reesei QM 9414 was also examined for comparison. Strains ofXylaria anisopleura andX. regalis had higher endocellulase (CMCase) and exocellulase (Avicelase) activities after 2 weeks' incubation.Hypoxylon stygium produced the highest activity of -glucosidase 3 days after inoculation. The optimum pH for these cellulolytic enzymes was approx. 5.0 and the optimum temperatures ranged from 37 to 50°C. A mixed culture process usingT. reesei QM 9414 andH. stygium was developed to obtain enhanced synthesis of cellulase. -Glucosidase activities in the mixed culture increased within 48h whenH. stygium was introduced after 24h.