A Survey of Presence and Related Concepts Skarbez, Richard; Brooks, Jr, Frederick P.; Whitton, Mary C.
ACM computing surveys,
11/2018, Letnik:
50, Številka:
6
Journal Article
Recenzirano
The presence construct, most commonly defined as the sense of “being there,” has driven research and development of virtual environments (VEs) for decades. Despite that, there is not widespread ...agreement on how to define or operationalize this construct. The literature contains many different definitions of presence and many proposed measures for it. This article reviews many of the definitions, measures, and models of presence from the literature. We also review several related constructs, including social presence, copresence, immersion, agency, transportation, reality judgment, and embodiment. In addition, we present a meta-analysis of existing presence models and propose a model of presence informed by Slater’s Place Illusion and Plausibility Illusion constructs.
Dislocation is one of the most common causes of patient and surgeon dissatisfaction following hip replacement and to treat it, the causes must first be understood. Patient factors include age greater ...than 70 years, medical comorbidities, female gender, ligamentous laxity, revision surgery, issues with the abductors, and patient education. Surgeon factors include the annual quantity of procedures and experience, the surgical approach, adequate restoration of femoral offset and leg length, component position, and soft-tissue or bony impingement. Implant factors include the design of the head and neck region, and so-called skirts on longer neck lengths. There should be offset choices available in order to restore soft-tissue tension. Lipped liners aid in gaining stability, yet if improperly placed may result in impingement and dislocation. Late dislocation may result from polyethylene wear, soft-tissue destruction, trochanteric or abductor disruption and weakness, or infection. Understanding the causes of hip dislocation facilitates prevention in a majority of instances. Proper pre-operative planning includes the identification of patients with a high offset in whom inadequate restoration of offset will reduce soft-tissue tension and abductor efficiency. Component position must be accurate to achieve stability without impingement. Finally, patient education cannot be over-emphasised, as most dislocations occur early, and are preventable with proper instructions.
Earth System Models (ESMs) are essential tools for understanding and predicting global change, but they cannot explicitly resolve hillslope‐scale terrain structures that fundamentally organize water, ...energy, and biogeochemical stores and fluxes at subgrid scales. Here we bring together hydrologists, Critical Zone scientists, and ESM developers, to explore how hillslope structures may modulate ESM grid‐level water, energy, and biogeochemical fluxes. In contrast to the one‐dimensional (1‐D), 2‐ to 3‐m deep, and free‐draining soil hydrology in most ESM land models, we hypothesize that 3‐D, lateral ridge‐to‐valley flow through shallow and deep paths and insolation contrasts between sunny and shady slopes are the top two globally quantifiable organizers of water and energy (and vegetation) within an ESM grid cell. We hypothesize that these two processes are likely to impact ESM predictions where (and when) water and/or energy are limiting. We further hypothesize that, if implemented in ESM land models, these processes will increase simulated continental water storage and residence time, buffering terrestrial ecosystems against seasonal and interannual droughts. We explore efficient ways to capture these mechanisms in ESMs and identify critical knowledge gaps preventing us from scaling up hillslope to global processes. One such gap is our extremely limited knowledge of the subsurface, where water is stored (supporting vegetation) and released to stream baseflow (supporting aquatic ecosystems). We conclude with a set of organizing hypotheses and a call for global syntheses activities and model experiments to assess the impact of hillslope hydrology on global change predictions.
Plain Language Summary
Hillslopes are key landscape features that organize water availability on land. Valley bottoms are wetter than hilltops, and sun‐facing slopes are warmer and drier than shaded ones. This hydrologic organization leads to systematic differences in soil and vegetation between valleys and hilltops, and between sunny and shady slopes. Although these patterns are fundamental to understanding the structures and functions of water and terrestrial ecosystems, they are too fine grained to be represented in global‐scale Earth System Models. Here we bring together Critical Zone scientists who study the interplay of vegetation, the porous upper layer of the continental crust from vegetation to bedrock, and moisture dynamics deep into the weathered bedrock underlying hillslopes and Earth System Model scientists who develop global models, to ask: Do hillslope‐scale processes matter to predicting global change? The answers will help scientists understand where and why hillslopes matter, and to better predict how terrestrial ecosystems, including societies, may affect and be affected by our rapidly changing planet.
Key Points
Lateral flow from ridges to valleys, and contrasts between sunny and shady slopes organize water, energy and vegetation across landscapes
These processes may affect Earth System Model predictions of terrestrial water storage and fluxes, as well as ecosystem resilience to stress
The greatest knowledge gap is the subsurface structure; Critical Zone science can offer new insights into terrestrial water storage/fluxes
The Epidemiology of low back pain Hoy, D; Brooks, P; Blyth, F ...
Best practice & research. Clinical rheumatology,
12/2010, Letnik:
24, Številka:
6
Journal Article
Recenzirano
Low back pain is an extremely common problem that most people experience at some point in their life. While substantial heterogeneity exists among low back pain epidemiological studies limiting the ...ability to compare and pool data, estimates of the 1 year incidence of a first-ever episode of low back pain range between 6.3% and 15.4%, while estimates of the 1 year incidence of any episode of low back pain range between 1.5% and 36%. In health facility- or clinic-based studies, episode remission at 1 year ranges from 54% to 90%; however, most studies do not indicate whether the episode was continuous between the baseline and follow-up time point(s). Most people who experience activity-limiting low back pain go on to have recurrent episodes. Estimates of recurrence at 1 year range from 24% to 80%. Given the variation in definitions of remission and recurrence, further population-based research is needed to assess the daily patterns of low back pain episodes over 1 year and longer. There is substantial information on low back pain prevalence and estimates of the point prevalence range from 1.0% to 58.1% (mean: 18.1%; median: 15.0%), and 1 year prevalence from 0.8% to 82.5% (mean: 38.1%; median: 37.4%). Due to the heterogeneity of the data, mean estimates need to be interpreted with caution. Many environmental and personal factors influence the onset and course of low back pain. Studies have found the incidence of low back pain is highest in the third decade, and overall prevalence increases with age until the 60–65 year age group and then gradually declines. Other commonly reported risk factors include low educational status, stress, anxiety, depression, job dissatisfaction, low levels of social support in the workplace and whole-body vibration. Low back pain has an enormous impact on individuals, families, communities, governments and businesses throughout the world. The Global Burden of Disease 2005 Study (GBD 2005) is currently making estimates of the global burden of low back pain in relation to impairment and activity limitation. Results will be available in 2011. Further research is needed to help us understand more about the broader outcomes and impacts from low back pain.
Human brown adipose tissue (BAT) can be activated to increase glucose uptake and energy expenditure, making it a potential target for treating obesity and metabolic disease. Data on the functional ...and anatomic characteristics of BAT are limited, however. In 20 healthy young men 12 lean, mean body mass index (BMI) 23.2 ± 1.9 kg/m²; 8 obese, BMI 34.8 ± 3.3 kg/m² after 5 h of tolerable cold exposure, we measured BAT volume and activity by 18F-labeled fluorodeoxyglucose positron emission tomography/computerized tomography (PET/CT). Obese men had less activated BAT than lean men (mean, 130 vs. 334 mL) but more fat in BAT-containing depots (mean, 1,646 vs. 855 mL) with a wide range (0.1–71%) in the ratio of activated BAT to inactive fat between individuals. Six anatomic regions had activated BAT—cervical, supraclavicular, axillary, mediastinal, paraspinal, and abdominal—with 67 ± 20% of all activated BAT concentrated in a continuous fascial layer comprising the first three depots in the upper torso. These nonsubcutaneous fat depots amounted to 1.5% of total body mass (4.3% of total fat mass), and up to 90% of each depot could be activated BAT. The amount and activity of BAT was significantly influenced by region of interest selection methods, PET threshold criteria, and PET resolutions. The present study suggests that active BAT can be found in specific adipose depots in adult humans, but less than one-half of the fat in these depots is stimulated by acute cold exposure, demonstrating a previously underappreciated thermogenic potential.
Determining associations between intestinal bacteria and continuously measured physiological outcomes is important for understanding the bacteria-host relationship but is not straightforward since ...abundance data (compositional data) are not normally distributed. To address this issue, we developed a fully Bayesian linear regression model (BRACoD;
B
ayesian
R
egression
A
nalysis of
Co
mpositional
D
ata) with physiological measurements (continuous data) as a function of a matrix of relative bacterial abundances. Bacteria can be classified as operational taxonomic units or by taxonomy (genus, family, etc.). Bacteria associated with the physiological measurement were identified using a Bayesian variable selection method: Stochastic Search Variable Selection. The output is a list of inclusion probabilities (
p
^
) and coefficients that indicate the strength of the association (
β
^
i
n
c
l
u
d
e
d
) for each bacterial taxa. Tests with simulated communities showed that adopting a cut point value of
p
^
≥ 0.3 for identifying included bacteria optimized the true positive rate (TPR) while maintaining a false positive rate (FPR) of ≤ 5%. At this point, the chances of identifying non-contributing bacteria were low and all well-established contributors were included. Comparison with other methods showed that BRACoD (at
p
^
≥ 0.3) had higher precision and a higher TPR than a commonly used center log transformed LASSO procedure (clr-LASSO) as well as higher TPR than an off-the-shelf Spike and Slab method after center log transformation (clr-SS). BRACoD was also less likely to include non-contributing bacteria that merely correlate with contributing bacteria. Analysis of a rat microbiome experiment identified 47 operational taxonomic units that contributed to fecal butyrate levels. Of these, 31 were positively and 16 negatively associated with butyrate. Consistent with their known role in butyrate metabolism, most of these fell within the Lachnospiraceae and Ruminococcaceae. We conclude that BRACoD provides a more precise and accurate method for determining bacteria associated with a continuous physiological outcome compared to clr-LASSO. It is more sensitive than a generalized clr-SS algorithm, although it has a higher FPR. Its ability to distinguish genuine contributors from correlated bacteria makes it better suited to discriminating bacteria that directly contribute to an outcome. The algorithm corrects for the distortions arising from compositional data making it appropriate for analysis of microbiome data.
Obesity induced by high fat (HF) diet is associated with inflammation which contributes to development of insulin resistance. Most prior studies have focused on adipose tissue as the source of ...obesity-associated inflammation. Increasing evidence links intestinal bacteria to development of diet-induced obesity (DIO). This study tested the hypothesis that HF western diet and gut bacteria interact to promote intestinal inflammation, which contributes to the progression of obesity and insulin resistance.
Conventionally raised specific-pathogen free (CONV) and germ-free (GF) mice were given HF or low fat (LF) diet for 2-16 weeks. Body weight and adiposity were measured. Intestinal inflammation was assessed by evaluation of TNF-alpha mRNA and activation of a NF-kappaB(EGFP) reporter gene. In CONV but not GF mice, HF diet induced increases in body weight and adiposity. HF diet induced ileal TNF-alpha mRNA in CONV but not GF mice and this increase preceded obesity and strongly and significantly correlated with diet induced weight gain, adiposity, plasma insulin and glucose. In CONV mice HF diet also resulted in activation of NF-kappaB(EGFP) in epithelial cells, immune cells and endothelial cells of small intestine. Further experiments demonstrated that fecal slurries from CONV mice fed HF diet are sufficient to activate NF-kappaB(EGFP) in GF NF-kappaB(EGFP) mice.
Bacteria and HF diet interact to promote proinflammatory changes in the small intestine, which precede weight gain and obesity and show strong and significant associations with progression of obesity and development of insulin resistance. To our knowledge, this is the first evidence that intestinal inflammation is an early consequence of HF diet which may contribute to obesity and associated insulin resistance. Interventions which limit intestinal inflammation induced by HF diet and bacteria may protect against obesity and insulin resistance.
Cockayne syndrome (CS) is a devastating neurodevelopmental disorder, with growth abnormalities, progeriod features, and sun sensitivity. CS is typically considered to be a DNA repair disorder, since ...cells from CS patients have a defect in transcription-coupled nucleotide excision repair (TC-NER). However, cells from UV-sensitive syndrome patients also lack TC-NER, but these patients do not suffer from the neurologic and other abnormalities that CS patients do. Also, the neurologic abnormalities that affect CS patients (CS neurologic disease) are qualitatively different from those seen in NER-deficient XP patients. Therefore, the TC-NER defect explains the sun sensitive phenotype common to both CS and UVsS, but cannot explain CS neurologic disease. However, as CS neurologic disease is of much greater clinical significance than the sun sensitivity, there is a pressing need to understand its molecular basis. While there is evidence for defective repair of oxidative DNA damage and mitochondrial abnormalities in CS cells, here I propose that the defects in transcription by both RNA polymerases I and II that have been documented in CS cells provide a better explanation for many of the severe growth and neurodevelopmental defects in CS patients than defective DNA repair. The implications of these ideas for interpreting results from mouse models of CS, and for the development of treatments and therapies for CS patients are discussed.
Deleterious genetic mutations allow developmental biologists to understand how genes control development. However, not all loss of function genetic mutants develop phenotypic changes. Many ...deleterious mutations only produce a phenotype in a subset of mutant individuals, a phenomenon known as incomplete penetrance. Incomplete penetrance can confound analyses of gene function and our understanding of this widespread phenomenon remains inadequate. To better understand what controls penetrance, we capitalized on the zebrafish mef2ca mutant which produces craniofacial phenotypes with variable penetrance. Starting with a characterized mef2ca loss of function mutant allele, we used classical selective breeding methods to generate zebrafish strains in which mutant-associated phenotypes consistently appear with low or high penetrance. Strikingly, our selective breeding for low penetrance converted the mef2ca mutant allele behavior from homozygous lethal to homozygous viable. Meanwhile, selective breeding for high penetrance converted the mef2ca mutant allele from fully recessive to partially dominant. Comparing the selectively-bred low- and high-penetrance strains revealed that the strains initially respond similarly to the mutation, but then gene expression differences between strains emerge during development. Thus, altered temporal genetic circuitry can manifest through selective pressure to modify mutant penetrance. Specifically, we demonstrate differences in Notch signaling between strains, and further show that experimental manipulation of the Notch pathway phenocopies penetrance changes occurring through selective breeding. This study provides evidence that penetrance is inherited as a liability-threshold trait. Our finding that vertebrate animals can overcome a deleterious mutation by tuning genetic circuitry complements other reported mechanisms of overcoming deleterious mutations such as transcriptional adaptation of compensatory genes, alternative mRNA splicing, and maternal deposition of wild-type transcripts, which are not observed in our system. The selective breeding approach and the resultant genetic circuitry change we uncovered advances and expands our current understanding of genetic and developmental resilience.
The characterization of mouse models of human disease is essential for understanding the underlying pathophysiology and developing new therapeutics. Many diseases are often associated with more than ...one model, and so there is a need to determine which model most closely represents the disease state or is most suited to the therapeutic approach under investigation. In the case of neurological disease, motor tests provide a good read-out of neurological function. This overview of available motor tasks aims to aid researchers in making the correct choice of test when attempting to tease out a transgenic phenotype or when assessing the recovery of motor function following therapeutic intervention.
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