A Study of Snippet Length and Informativeness: Behaviour, Performance and User Experience

The design and presentation of a Search Engine Results Page (SERP) has been subject to much research. With many contemporary aspects of the SERP now under scrutiny, work still remains in investigating more traditional SERP components, such as the result summary. Prior studies have examined a variety of different aspects of result summaries, but in this paper we investigate the influence of result summary length on search behaviour, performance and user experience. To this end, we designed and conducted a within-subjects experiment using the TREC AQUAINT news collection with 53 participants. Using Kullback-Leibler distance as a measure of information gain, we examined result summaries of different lengths and selected four conditions where the change in information gain was the greatest: (i) title only; (ii) title plus one snippet; (iii) title plus two snippets; and (iv) title plus four snippets. Findings show that participants broadly preferred longer result summaries, as they were perceived to be more informative. However, their performance in terms of correctly identifying relevant documents was similar across all four conditions. Furthermore, while the participants felt that longer summaries were more informative, empirical observations suggest otherwise; while participants were more likely to click on relevant items given longer summaries, they also were more likely to click on non-relevant items. This shows that longer is not necessarily better, though participants perceived that to be the case - and second, they reveal a positive relationship between the length and informativeness of summaries and their attractiveness (i.e. clickthrough rates). These findings show that there are tensions between perception and performance when designing result summaries that need to be taken into account

Type-specific radioimmunoassays for the gp70s of mink cell focus-inducing murine leukemia viruses: expression of a cross-reacting antigen in cells infected with the friend strain of the spleen focus-forming virus

We have isolated the gp70 of a helper-independent strain of a Friend mink cell focus-inducing (MCF) virus, Fr-MCF-1. This recombinant virus, like the previously described AKR-MCF viruses, has been shown by both biological and biochemical means to be an envelope gene recombinant between Friend murine leukemia virus (F-MuLV) and a mouse xenotropic virus. Utilizing (125)I- labeled Fr-MCF-1 gp70 and antiserum prepared against an MCF strain of Moloney type-C virus (Mol-MCF(83)), we have developed a radioimmunoassay which detects immunological determinant (s)contained in the gp70s of MCF viruses derived from F-MuLV, Mol-MuLV, and AKR-MuLV. This MCF determinant(s) is not detected in the ecotropic parents of each of these MCF viruses, nor in helper-independent murine xenotropic viruses derived from Swiss or BALB/c mice. A protein partially cross-reactive with the MCF gp70 determinant(s) is detected in a replicating xenotropic virus derived from NZB mice. Utilizing this MCF gp70 specific immunoassay, we can detect a cross-reacting gene product coded for by the Friend strain of the spleen focus-forming virus (SFFV) in rat fibroblasts nonproductively infected with SFFV. The results support earlier molecular hybridization studies which indicated that the genome of SFFV contains genetic information derived from both F-MuLV and xenotropic virus, and that the xenotropic-related sequences in SFFV are highly related to those found in MCF murine type-C viruses

HOME RANGES OF THE NILGAI ANTELOPE (\u3ci\u3eBOSELAPHUS TRAGOCAMELUS\u3c/i\u3e) IN TEXAS

Information related to home ranges of the nilgai antelope (Boselaphus tragocamelus) was needed to estimate spread of cattle-fever ticks (Riphicephalus microplus and R. annulatus) and to develop management protocols. We captured, placed telemetry collars on, and monitored 10 male and 12 female nilgai antelopes during February 2006–May 2008. We detected no difference between size of home ranges of males and females and determined maximum axes of home ranges of 16.3 and 13.8 km, respectively. The combination of large home ranges and large axes of home range indicates that if cattle-fever ticks are being maintained on nilgai antelopes, then the area in which these antelopes may spread ticks is great

HOME RANGES OF THE NILGAI ANTELOPE (\u3ci\u3eBOSELAPHUS TRAGOCAMELUS\u3c/i\u3e) IN TEXAS

Information related to home ranges of the nilgai antelope (Boselaphus tragocamelus) was needed to estimate spread of cattle-fever ticks (Riphicephalus microplus and R. annulatus) and to develop management protocols. We captured, placed telemetry collars on, and monitored 10 male and 12 female nilgai antelopes during February 2006–May 2008. We detected no difference between size of home ranges of males and females and determined maximum axes of home ranges of 16.3 and 13.8 km, respectively. The combination of large home ranges and large axes of home range indicates that if cattle-fever ticks are being maintained on nilgai antelopes, then the area in which these antelopes may spread ticks is great

Fossil evidence for low gas exchange capacities for Early Cretaceous angiosperm leaves

The photosynthetic gas exchange capacities of early angiosperms remain enigmatic. Nevertheless, many hypotheses about the causes of early angiosperm success and how angiosperms influenced Mesozoic ecosystem function hinge on understanding the maximum capacity for early angiosperm metabolism. We applied structure-functional analyses of leaf veins and stomatal pore geometry to determine the hydraulic and diffusive gas exchange capacities of Early Cretaceous fossil leaves. All of the late Aptian-early Albian angiosperms measured possessed low vein density and low maximal stomatal pore area, indicating low leaf gas exchange capacities in comparison to modern ecologically dominant angiosperms. Gas exchange capacities for Early Cretaceous angiosperms were equivalent or lower than ferns and gymnosperms. Fossil leaf taxa from Aptian to Paleocene sediments previously identified as putative stem-lineages to Austrobaileyales and Chloranthales had the same gas exchange capacities and possibly leaf water relations of their living relatives. Our results provide fossil evidence for the hypothesis that high leaf gas exchange capacity is a derived feature of later angiosperm evolution. In addition, the leaf gas exchange functions of austrobaileyoid and chloranthoid fossils support the hypothesis that comparative research on the biology of living basal angiosperm lineages reveals genuine signals of Early Cretaceous angiosperm ecophysiology

Fossil evidence for Cretaceous escalation in angiosperm leaf vein evolution

The flowering plants that dominate modern vegetation possess leaf gas exchange potentials that far exceed those of all other living or extinct plants. The great divide in maximal ability to exchange CO 2 for water between leaves of nonangiosperms and angiosperms forms the mechanistic foundation for speculation about how angiosperms drove sweeping ecological and biogeochemical change during the Cretaceous. However, there is no empirical evidence that angiosperms evolved highly photosynthetically active leaves during the Cretaceous. Using vein density (D V ) measurements of fossil angiosperm leaves, we show that the leaf hydraulic capacities of angiosperms escalated severalfold during the Cretaceous. During the first 30 million years of angiosperm leaf evolution, angiosperm leaves exhibited uniformly low vein D V that overlapped the D V range of dominant Early Cretaceous ferns and gymnosperms. Fossil angiosperm vein densities reveal a subsequent biphasic increase in D V . During the first mid-Cretaceous surge, angiosperm D V first surpassed the upper bound of D V limits for nonangiosperms. However, the upper limits of D V typical of modern megathermal rainforest trees first appear during a second wave of increased D V during the Cretaceous-Tertiary transition. Thus, our findings provide fossil evidence for the hypothesis that significant ecosystem change brought about by angiosperms lagged behind the Early Cretaceous taxonomic diversification of angiosperms.Facultad de Ciencias Naturales y Muse