A comparison of size and age of red snapper (Lutjanus campechanus) with the age of artificial reefs in the northern Gulf of Mexico

Despite extensive study, it still is not clear whether artificial reefs produce new fish biomass or whether they only attract various species and make them more vulnerable to fishing mortality. To further evaluate this question, the size and age of red snapper (Lutjanus campechanus) were sampled from April to November 2010 at artificial reefs south of Mobile Bay off the coast of Alabama and compared with the age of the artificial reef at the site of capture. Red snapper were collected with hook and line and a fish trap and visually counted during scuba-diver surveys. In the laboratory, all captured red snapper were weighed and measured, and the otoliths were removed for aging. The mean age of red snapper differed significantly across reefs of different ages, with older reefs having older fish. The mean age of red snapper at a particular reef was not related to reef depth or distance to other reefs. The positive correlation between the mean age of red snapper and the age of the reef where they were found supports the contention that artificial reefs in the northern Gulf of Mexico enhance production of red snapper. The presence of fish older than the reef indicates that red snapper are also attracted to artificial reefs.

Multiscale analysis of factors that affect the distribution of sharks throughout the northern Gulf of Mexico

Identification of the spatial scale at which marine communities are organized is critical to proper management, yet this is particularly difficult to determine for highly migratory species like sharks. We used shark catch data collected during 2006–09 from fishery-independent bottom-longline surveys, as well as biotic and abiotic explanatory data to identify the factors that affect the distribution of coastal sharks at 2 spatial scales in the northern Gulf of Mexico. Centered principal component analyses (PCAs) were used to visualize the patterns that characterize shark distributions at small (Alabama and Mississippi coast) and large (northern Gulf of Mexico) spatial scales. Environmental data on temperature, salinity, dissolved oxygen (DO), depth, fish and crustacean biomass, and chlorophyll-a (chl-a) concentration were analyzed with normed PCAs at both spatial scales. The relationships between values of shark catch per unit of effort (CPUE) and environmental factors were then analyzed at each scale with co-inertia analysis (COIA). Results from COIA indicated that the degree of agreement between the structure of the environmental and shark data sets was relatively higher at the small spatial scale than at the large one. CPUE of Blacktip Shark (Carcharhinus limbatus) was related positively with crustacean biomass at both spatial scales. Similarly, CPUE of Atlantic Sharpnose Shark (Rhizoprionodon terraenovae) was related positively with chl-a concentration and negatively with DO at both spatial scales. Conversely, distribution of Blacknose Shark (C. acronotus) displayed a contrasting relationship with depth at the 2 scales considered. Our results indicate that the factors influencing the distribution of sharks in the northern Gulf of Mexico are species specific but generally transcend the spatial boundaries used in our analyses.

Gulf of Mexico tidal creeks serve as sentinel habitats for assessing the impact of coastal development on ecosystem health

A study was conducted, in association with the Alabama and Mississippi National Estuarine Research Reserves (NERRs) in the Gulf of Mexico (GoM) as well as the Georgia, South Carolina, and North Carolina NERRs in the Southeast (SE), to evaluate the impacts of coastal development on tidal creek sentinel habitats, including potential impacts to human health and well-being. Uplands associated with Southeast and Gulf of Mexico tidal creeks, and the salt marshes they drain, are popular locations for building homes, resorts, and recreational facilities because of the high quality of life and mild climate associated with these environments. Tidal creeks form part of the estuarine ecosystem characterized by high biological productivity, great ecological value, complex environmental gradients, and numerous interconnected processes. This research combined a watershed-level study integrating ecological, public health and human dimension attributes with watershed-level land cover data. The approach used for this research was based upon a comparative watershed and ecosystem approach that sampled tidal creek networks draining developed watersheds (e.g., suburban, urban, and industrial) as well as undeveloped sites (Holland et al. 2004, Sanger et al. 2008). The primary objective of this work was to define the relationships between coastal development with its concomitant land cover changes, and non-point source pollution loading and the ecological and human health and wellbeing status of tidal creek ecosystems. Nineteen tidal creek systems, located along the Southeastern United States coast from southern North Carolina to southern Georgia, and five Gulf of Mexico systems from Alabama and Mississippi were sampled during summer (June-August) 2005, 2006 (SE) and 2008 (GoM). Within each system, creeks were divided into two primary segments based upon tidal zoning: intertidal (i.e., shallow, narrow headwater sections) and subtidal (i.e., deeper and wider sections), and watersheds were delineated for each segment. In total, we report findings on 29 intertidal and 24 subtidal creeks. Indicators sampled throughout each creek included water quality (e.g., dissolved oxygen, salinity, nutrients, chlorophyll-a levels), sediment quality (e.g., characteristics, contaminant levels including emerging contaminants), pathogen and viral indicators (e.g., fecal coliform, enterococci, F+ coliphages, F- coliphages), and abundance and tissue contamination of biological resources (e.g., macrobenthic and nektonic communities, shellfish tissue contaminants). Tidal creeks have been identified as a sentinel habitat to assess the impacts of coastal development on estuarine areas in the southeastern US. A conceptual model for tidal creeks in the southeastern US identifies that human alterations (stressors) of upland in a watershed such as increased impervious cover will lead to changes in the physical and chemical environment such as microbial and nutrient pollution (exposures), of a receiving water body which then lead to changes in the living resources (responses). The overall objective of this study is to evaluate the applicability of the current tidal creek classification framework and conceptual model linking tidal creek ecological condition to potential impacts of development and urban growth on ecosystem value and function in the Gulf of Mexico US in collaboration with Gulf of Mexico NERR sites. The conceptual model was validated for the Gulf of Mexico US tidal creeks. The tidal creek classification system developed for the southeastern US could be applied to the Gulf of Mexico tidal creeks; however, some differences were found that warrant further examination. In particular, pollutants appeared to translate further downstream in the Gulf of Mexico US compared to the southeastern US. These differences are likely the result of the morphological and oceanographic differences between the two regions. Tidal creeks appear to serve as sentinel habitats to provide an early warning of the ensuing harm to the larger ecosystem in both the Southeastern and Gulf of Mexico US tidal creeks.

Red snapper (Lutjanus campechanus) demographic structure in the northern Gulf of Mexico based on spatial patterns in growth rates and morphometrics

Red snapper (Lutjanus campechanus) in the United States waters of the Gulf of Mexico (GOM) has been considered a single unit stock since management of the species began in 1991. The validity of this assumption is essential to management decisions because measures of growth can differ for nonmixing populations. We examined growth rates, size-at-age, and length and weight information of red snapper collected from the recreational harvests of Alabama (n=2010), Louisiana (n=1905), and Texas (n =1277) from 1999 to 2001. Ages were obtained from 5035 otolith sections and ranged from one to 45 years. Fork length, total weight, and age-frequency distributions differed significantly among all states; Texas, however, had a much higher proportion of smaller, younger fish. All red snapper showed rapid growth until about age 10 years, after which growth slowed considerably. Von Bertalanffy growth models of both mean fork length and mean total weight-at-age predicted significantly smaller fish at age from Texas, whereas no differences were found between Alabama and Louisiana models. Texas red snapper were also shown to differ significantly from both Alabama and Louisiana red snapper in regressions of mean weight at age. Demographic variation in growth rates may indicate the existence of separate management units of red snapper in the GOM. Our data indicate that the red snapper inhabiting the waters off Texas are reaching smaller maximum sizes at a faster rate and have a consistently smaller total weight at age than those collected from Louisiana and Alabama waters. Whether these differences are environmentally induced or are the result of genetic divergence remains to be determined, but they should be considered for future management regulations.

A rhetorical approach to IT diffusion: reconceptualizing the ideology-framing relationship in computerization movements

In this paper we propose rhetoric as a valuable yet underdeveloped alternative paradigm for examining IT diffusion. Building on recent developments of computerization movements theory, our rhetorical approach proposes that two central elements of the theory, framing and ideology, rather than being treated as separate can be usefully integrated. We suggest that IT diffusion can be usefully explored through examining the interrelationship of the deep structures underlying ideology and the type and sequence of rhetorical claims underpinning actors’ framing strategies. Our theoretical developments also allow us to better understand competing discourses influencing the diffusion process. These discourses reflect the ideologies and shape the framing strategies of actors in the broader field context. We illuminate our theoretical approach by drawing on the history of the diffusion of free and open source software.

Spatio-temporal clustering of probabilistic region trajectories

We propose a novel model for the spatio-temporal clustering of trajectories based on motion, which applies to challenging street-view video sequences of pedestrians captured by a mobile camera. A key contribution of our work is the introduction of novel probabilistic region trajectories, motivated by the non-repeatability of segmentation of frames in a video sequence. Hierarchical image segments are obtained by using a state-of-the-art hierarchical segmentation algorithm, and connected from adjacent frames in a directed acyclic graph. The region trajectories and measures of confidence are extracted from this graph using a dynamic programming-based optimisation. Our second main contribution is a Bayesian framework with a twofold goal: to learn the optimal, in a maximum likelihood sense, Random Forests classifier of motion patterns based on video features, and construct a unique graph from region trajectories of different frames, lengths and hierarchical levels. Finally, we demonstrate the use of Isomap for effective spatio-temporal clustering of the region trajectories of pedestrians. We support our claims with experimental results on new and existing challenging video sequences. © 2011 IEEE.

Physical consequences of a nonparametric uncertainty model in structural dynamics

One of the main claims of the nonparametric model of random uncertainty introduced by Soize (2000) [3] is its ability to account for model uncertainty. The present paper investigates this claim by examining the statistics of natural frequencies, total energy and underlying dispersion equation yielded by the nonparametric approach for two simple systems: a thin plate in bending and a one-dimensional finite periodic massspring chain. Results for the plate show that the average modal density and the underlying dispersion equation of the structure are gradually and systematically altered with increasing uncertainty. The findings for the massspring chain corroborate the findings for the plate and show that the remote coupling of nonadjacent degrees of freedom induced by the approach suppresses the phenomenon of mode localization. This remote coupling also leads to an instantaneous response of all points in the chain when one mass is excited. In the light of these results, it is argued that the nonparametric approach can deal with a certain type of model uncertainty, in this case the presence of unknown terms of higher or lower order in the governing differential equation, but that certain expectations about the system such as the average modal density may conflict with these results. © 2012 Elsevier Ltd.

"Plateau"-related summary statistics are uninformative for comparing working memory models.

Performance on visual working memory tasks decreases as more items need to be remembered. Over the past decade, a debate has unfolded between proponents of slot models and slotless models of this phenomenon (Ma, Husain, Bays (Nature Neuroscience 17, 347-356, 2014). Zhang and Luck (Nature 453, (7192), 233-235, 2008) and Anderson, Vogel, and Awh (Attention, Perception, Psychophys 74, (5), 891-910, 2011) noticed that as more items need to be remembered, "memory noise" seems to first increase and then reach a "stable plateau." They argued that three summary statistics characterizing this plateau are consistent with slot models, but not with slotless models. Here, we assess the validity of their methods. We generated synthetic data both from a leading slot model and from a recent slotless model and quantified model evidence using log Bayes factors. We found that the summary statistics provided at most 0.15 % of the expected model evidence in the raw data. In a model recovery analysis, a total of more than a million trials were required to achieve 99 % correct recovery when models were compared on the basis of summary statistics, whereas fewer than 1,000 trials were sufficient when raw data were used. Therefore, at realistic numbers of trials, plateau-related summary statistics are highly unreliable for model comparison. Applying the same analyses to subject data from Anderson et al. (Attention, Perception, Psychophys 74, (5), 891-910, 2011), we found that the evidence in the summary statistics was at most 0.12 % of the evidence in the raw data and far too weak to warrant any conclusions. The evidence in the raw data, in fact, strongly favored the slotless model. These findings call into question claims about working memory that are based on summary statistics.

Manufacturing excellent engineers: Skill development in a Masters programme

An MPhil programme, delivered by the Engineering Department at the University of Cambridge, claims to be excellent at preparing graduates for manufacturing industry careers. The course uses a combination of different educational experiences, including industry-based assignments, industrial visits and practical exercises. This research explores how problem solving skills are developed during the first module, Induction, which is designed to enable students to undertake their first industrial assignment. From the literature, four conditions necessary for skill development were identified: Provision of a skill description, making explicit key components A number of different experiences with a range of contextual variables A teaching process which includes regular feedback and student reflection Students motivated to learn. These were used to construct a skill development framework (SDF). Using a case study research design, multiple types of evidence were collected to test for the above conditions using both classroom observation and questionnaire methods. The results confirmed the presence of the SDF conditions at different levels, with reflection aspects considered the weakest. Conflicting results were obtained regarding the students' self-awareness of skill levels. A plausible explanation is a change in the students' frame of reference. This initial study set out to develop a better understanding of the process of skill development. Whilst the SDF appears reasonable, there is a need for further work in three broad areas of defining skills, assessing skills and developing reflection skills.

Systematic study on alpha decay half-lives of superheavy nuclei

The a-decay half-lives of a set of superheavy nuclear isotope chain from Z = 105 to 120 have been analyzed systematically within the WKB method, and some nuclear structure features are found. The decay barriers have been determined in the quasi-molecular shape path within the Generalized Liquid Drop Model (GLDM) including the proximity effects between nucleons in a neck and the mass and charge asymmetry. The results are in reasonable agreement with the published experimental data for the alpha decay half-lives of isotopes of charge 112, 114, and 116, of the element 294118 and of some decay products. A comparison of present calculations with the results by the DDM3Y effective interaction and by the Viola-Seaborg Sobiczewski (VSS) formulae is also made. The experimental a decay half lives all stand in between the GLDM calculations and VSS formula results. This demonstrates the possibility of these models to provide reasonable estimates for the half-lives of nuclear decays by a emissions for the domain of SHN. The half-lives of these new nuclei are thus well tested from the reasonable consistence of the macroscopic, the microscopic, the empirical formulae and the experimental data. This also shows that the present data of SHN themselves are consistent. It could suggest that the present experimental claims on the existence of new elements Z = 110 similar to 118 are reliable. It is expected that greater deviations of a few SHN between the data and the model may be eliminated by further improvements on the precision of the measurements.

松辽徐家围子断陷层序地层充填模式及含油气性特征

Based on the principle and method of sequence, the author describes the sequence-filling model of the rifting basin of Xujiaweizi and its gas exploration potential. The object of this paper belongs to the area around Shengping-Wangjiatun anticline. Its srtatigraphy includes Huoshiling Formation (neutral and basic volcanic rocks), Shahezi Formation (coal bedding and mud and some sandstone) and Yingcheng Formation from bottom to top. These stratigraphy units are defined by author as mesosequences respectively. The author emphasizes that the main control factors of sequence change with the types of basin and stage of basin. So the sequence is researched according to the types of basin. This viewpoint is very new, and it is consistent with the principle of sequence. Volcanic action is very frequent and acute, topography difference is obvious. Between the volcanic events, Shahezi Formation is formed, which mainly consists-of sedimentary rocks. Based on the datum from seismic section and drilling core and well-logging, the author analyzes the single unit and unit set and system tract and sedimentary fancies, then, according to the accommodation space change and marking of sequence boundary, Shahezi Formation is divided into two Third-scale sequences. The sedimentary fancies and depth distribution are described. The author also pointed out that the volcanic rocks consume the accommodation space, so volcanic rocks can influence the development of sequence. Based on the concept of accommodation space, the author put volcanic rocks into sequence frame, which normally consists of sedimentary rocks. The topography of volcanic is controlled by lithology of volcanic rocks, the pattern of volcanic eruption and the topography before volcanic eruption. The topography of volcanic can influence sedimentation and the filling pattern of sedimentary rocks. The author describes the composition and lithology fancies and depth distribution of volcanic rocks. The volcanic rocks and Volcanic building, volcanic structure is recognized on seismic section. The author paid a special attention to the relationship between sedimentation and volcanism. Finally, the author analyses the combination of source-reservoir-cover unit in sequence frame. The mudstone of Shahezi Formation has a great depth, the Kerogene in it belongs to type II and III, which tends to produce gas. The Yingcheng Formation lies between Shahezi Formation and Denglouku Formation, belonging to good reservoir. The volcanic rocks of Huoshiling Formation often formed high building, which can capture the gas produced from Shahezi Formation. The stratigraphy of rifting basin of Xujiaweizi has the great potential of gas exploration. This paper claims the following creative points: 1. The author applied the principle and method of sequence to rifting basin, greatly extending its research area and topic issues. 2. The author pointed out that basin of different type and of different stage has a different type of sequence. This is caused by the different main control factors of sequence. 3. Put volcanic rocks into the sequence frame, discussing the probability of regarding the volcanic rocks as the component of sequence, dealing with the relationship between sedimentation and volcanism and its influence to the source-reservoir-cover system. 4. The author pointed out that the filling pattern of rifting basin are determined by the filling pattern of megasequence, whose filling pattern is determined by the filling pattern of system tract and the change of accommodation space.

Garbage Collection is Fast, But a Stack is Faster

Prompted by claims that garbage collection can outperform stack allocation when sufficient physical memory is available, we present a careful analysis and set of cross-architecture measurements comparing these two approaches for the implementation of continuation (procedure call) frames. When the frames are allocated on a heap they require additional space, increase the amount of data transferred between memory and registers, and, on current architectures, require more instructions. We find that stack allocation of continuation frames outperforms heap allocation in some cases by almost a factor of three. Thus, stacks remain an important implementation technique for procedure calls, even in the presence of an efficient, compacting garbage collector and large amounts of memory.

Breaking the Rules: writing reflectively for yourself.

The rules which epitomise good writing may on occasions be broken, deliberately and with what the writers judge to be good purpose. This can well occur when students or staff set out to engage effectively with their personal and professional development, through personal reflection on and in experiences. They may do this in what has been called “stream of consciousness” writing, which is deliberately compiled in a manner at variance with the general rules for best practice. The rationale for such an unusual decision, namely to engage in what is frankly disorderly writing, is set out briefly in this chapter. Its characteristics are summarised, in implicit contrast with more conventional styles of writing. Examples are included of claims for the effectiveness of this style when used for developmental purposes by students and staff; and reference is made to the publications of some of those who have endorsed this approach.

The Lord of the Rings and ?Identification?: A Critical Encounter

Barker, M. (2005) 'The Lord of the Rings and 'identification': a critical encounter', European Journal of Communication, 20, 3, 353-378 Sponsorship: This research was made possible by a grant from the Economic and Social Research Council (ESRC Grant No. 000-22-0323)

Ethics and Foreign Policy: The Antinomies of New Labour's 'Third Way' in Sub-Saharan Africa

Abrahamsen, Rita, Williams, Paul, 'Ethics and Foreign Policy: The Antinomies of New Labour's 'Third Way' in Sub-Saharan Africa', Political Studies (2002) 49(2) pp.249-264 RAE2008