Discontinuation or "dropout" from contact lens (CL) wear continues to afflict the CL industry. This study was conducted to determine whether the advent of new CL materials and designs has impacted ...the dropout rate and the reasons for discontinuation.
Current and lapsed CL wearers residing in Canada were recruited using Facebook to take part in an on line survey investigating CL wearing experiences during 2008 to 2010 and to establish the percentage of participants who temporarily and permanently discontinued CL wear during the period surveyed.
Four thousand two hundred seven eligible surveys were received (64% female; median age 27 years). Forty percent had lapsed from lens wear for at least 4 months; however, 62% of the lapsed wearers (LWs) resumed wear. There were no differences between LWs and nonlapsed wearers (NLWs) with respect to gender; however, LWs were older, started lens wear when older, and had not worn lenses for as long as NLWs (all P<0.001). More NLWs than LWs wore silicone hydrogel CLs (49% vs. 38%, P<0.001) and more LWs than NLWs wore daily disposable lenses and hydrogel CLs (24% vs. 19% and 22% vs. 18%, respectively, P≤0.001). Primary reasons for discontinuation were discomfort (24%), dryness (20%), red eyes (7%), and expense (7%). Compliance with lens replacement was no different between LWs and NLWs (48% vs. 45%).
About 23% of those surveyed had discontinued CL wear permanently. The primary reasons for dropping out continue to be discomfort and dryness. Dropout rates were lower in silicone hydrogel wearers.
AMP-activated protein kinase (AMPK) is the downstream component of a protein kinase cascade that plays a major role in maintaining energy homoeostasis. Within individual cells, AMPK is activated by a ...rise in the AMP/ATP ratio that occurs following a fall in ATP levels. AMPK is also regulated by the adipokines, adiponectin and leptin, hormones that are secreted from adipocytes. AMPK regulates a wide range of metabolic pathways, including fatty acid oxidation, fatty acid synthesis, glycolysis and gluconeogenesis. In peripheral tissues, activation of AMPK leads to responses that are beneficial in counteracting the deleterious effects that arise in the metabolic syndrome. Recent studies have demonstrated that modulation of AMPK activity in the hypothalamus plays a role in feeding. A decrease in hypothalamic AMPK activity is associated with decreased feeding, whereas activation of AMPK leads to increased food intake. Furthermore, signalling pathways occurring in the hypothalamus lead to changes in AMPK activity in peripheral tissues, such as skeletal muscle, via the sympathetic nervous system. AMPK, therefore, provides a mechanism for monitoring changes in energy metabolism within individual cells and at the level of the whole body. Activation of AMPK requires phosphorylation of threonine 172 (Thr-172) within the catalytic subunit. Recent studies have shown that both LKB1 and Ca2+/calmodulin-dependent protein kinase kinase- (CaMKK) play important roles in phosphorylating and activating AMPK. In addition, there is evidence that AMPK can be activated by other upstream kinases, although the physiological significance of this is not clear at present. This review focuses on the role of LKB1 and CaMKK in the regulation of AMPK.
Biguanides such as metformin have previously been shown to antagonize hepatic glucagon-stimulated cyclic AMP (cAMP) signalling independently of AMP-activated protein kinase (AMPK) via direct ...inhibition of adenylate cyclase by AMP. Here we show that incubation of hepatocytes with the small-molecule AMPK activator 991 decreases glucagon-stimulated cAMP accumulation, cAMP-dependent protein kinase (PKA) activity and downstream PKA target phosphorylation. Moreover, incubation of hepatocytes with 991 increases the Vmax of cyclic nucleotide phosphodiesterase 4B (PDE4B) without affecting intracellular adenine nucleotide concentrations. The effects of 991 to decrease glucagon-stimulated cAMP concentrations and activate PDE4B are lost in hepatocytes deleted for both catalytic subunits of AMPK. PDE4B is phosphorylated by AMPK at three sites, and by site-directed mutagenesis, Ser304 phosphorylation is important for activation. In conclusion, we provide a new mechanism by which AMPK antagonizes hepatic glucagon signalling via phosphorylation-induced PDE4B activation.
Hillslope threshold response to storm rainfall is poorly understood. Basic questions regarding the type, location, and flow dynamics of lateral, subsurface flow remain unanswered, even at our most ...intensively studied field sites. Here we apply a forensic approach where we combined irrigation and excavation experiments at the well studied Maimai hillslope to determine the typology and morphology of the primary lateral subsurface flowpaths, and the control of bedrock permeability and topography on these flowpaths. The experiments showed that downslope flow is concentrated at the soil bedrock interface, with flowpath locations controlled by small features in the bedrock topography. Lateral subsurface flow is characterized by high velocities, several orders of magnitude greater than predicted by Darcy’s Law using measured hydraulic conductivities at the site. We found the bedrock to be moderately permeable, and showed that vertical percolation of water into the bedrock is a potentially large component of the hillslope water balance. Our results suggest that it is the properties of the bedrock (topography and permeability) that control subsurface flow at Maimai, and the soil profile plays a less significant role than previously thought. A companion paper incorporates these findings into a conceptual model of hydrological processes at the site to explore the generalities of whole-hillslope threshold response to storm rainfall.
Climate change and forest diseases Sturrock, R. N.; Frankel, S. J.; Brown, A. V. ...
Plant pathology,
February 2011, Letnik:
60, Številka:
1
Journal Article
Recenzirano
Odprti dostop
As climate changes, the effects of forest diseases on forest ecosystems will change. We review knowledge of relationships between climate variables and several forest diseases, as well as current ...evidence of how climate, host and pathogen interactions are responding or might respond to climate change. Many forests can be managed to both adapt to climate change and minimize the undesirable effects of expected increases in tree mortality. We discuss four types of forest and disease management tactics – monitoring, forecasting, planning and mitigation – and provide case studies of yellow‐cedar decline and sudden aspen decline to illustrate how forest diseases might be managed in the face of climate change. The uncertainties inherent to climate change effects can be diminished by conducting research, assessing risks, and linking results to forest policy, planning and decision making.
Analyses of trends in observed floods often focus on relatively frequent events, whereas changes in rare floods are only studied for a small number of locations that have exceptionally long ...observational records. Understanding changes in rare floods is especially relevant as these events are often most damaging and influence the design of major structures. Here, we provide an assessment of changes in the largest flood events (~0.033 annual exceedance probability) observed during the period 1980−2009 for 1744 catchments located in Australia, Brazil, Europe and the United States. The occurrence of rare floods in spatial aggregate shows strong temporal variability and peaked around 1995. During the 30 year period, there are overall increases in both the frequency and magnitude of extreme floods. These increases are strongest in Europe and the United States, and weakest in Brazil and Australia. Physical causes of the reported short-term variability and longer-term changes in extreme floods currently remain elusive, because the key drivers vary between catchments. Nonetheless, this approach provides the basis for a more spatially representative assessment of changes in extreme flood occurrence.
Within the context of the conservation of resources model, when a resource is deployed, it is depleted – albeit temporarily. However, when a ‘key’, stable resource, such as Conscientiousness, is ...activated (e.g., using a self‐control strategy, such as resisting an email interruption), we predicted that (1) another, more volatile resource (affective well‐being) would be impacted and that (2) this strategy would be deployed as a trade‐off, allowing one to satisfy task goals, at the expense of well‐being goals. We conducted an experience‐sampling field study with 52 email‐users dealing with their normal email as it interrupted them over the course of a half‐day period. This amounted to a total of 376 email reported across the sample. Results were analysed using random coefficient hierarchical linear modelling and included cross‐level interactions for Conscientiousness with strategy and well‐being. Our first prediction was supported – deploying the stable, key resource of Conscientiousness depletes the volatile, fluctuating resource of affective well‐being. However, our second prediction was not fully realized. Although resisting or avoiding an email interruption was perceived to hinder well‐being goal achievement by Conscientious people, it had neither a positive nor negative impact on task goal achievement. Implications for theory and practice are discussed.
Practitioner points
It may be necessary for highly Conscientious people to turn off their email interruption alerts at work, in order to avoid the strain that results from an activation‐resistance mechanism afforded by the arrival of a new email.
Deploying key resources means that volatile resources may be differentially spent, depending on one's natural tendencies and how these interact with the work task and context. This suggests that the relationship between demands and resources is not always direct and predictable.
Practitioners may wish to appraise the strategies they use to deal with demands such as email at work, to identify if these strategies are assisting with task or well‐being goal achievement, or whether they have become defunct through automation.
When selecting the physical form of an active pharmaceutical substance, there is often a question of when a molecule's pKa renders it too low for salt formation and formulation into a product that ...will be sufficiently physically stable to provide adequate shelf life. In the paper, a graph is provided that tabulates pKa values of active pharmaceuticals versus the salt or free base form that was chosen to be developed as an orally administered drug product. Tabulation of the data provides insight into where, if any, practical cutoff exists, under which salt formation should not be considered. Specific examples of disproportionation reactions are reviewed and are described in light of the concepts of pH maximum, pH microenvironment, and Gibbs free energy to gain further insight into when such reactions become favorable. The driving force for disproportionation reactions is substantially greater than that for polymorphic form conversion, and as a consequence, its probability of occurring in the solid-state is much greater when formulated in favorable microenvironments. Factors that influence the reaction rate are examined. It is concluded that each salt should be evaluated on the merit of its physical properties and often the most soluble salt will not be one's best choice. Unfortunately, compounds that stand to benefit the most from salt formation due to their exceptionally low intrinsic solubility are the ones that will be most likely to disproportionate if their pKa is relatively low.
We formulate and solve an analytical model of seasonal snowpack dynamics, by assuming a simple temperature index model for the snowpack, driven by purely seasonal climate forcing. Three dimensionless ...variables control the modeled system: one to indicate the temperature regime, one for the seasonality of both temperature and precipitation, and one for the mean precipitation rate relative to a characteristic melt rate. The purpose of the model is to provide insight into the relative roles of the mean and seasonality of temperature, the mean and seasonality of precipitation, and the melt factor, in controlling snow climatology.
The model can be used to make broad-scale predictions of the climatology of seasonal snow water storage, and its sensitivity to climate. Particular variables of interest include the maximum seasonal snow storage, the start and end of the snow accumulation period, and the time of year at which the snowpack is completely melted. The model makes useful uncalibrated predictions at six widely separated sites in the western USA which have a continuous seasonal snowpack.
The connections between the model and a widely-used snow classification of Sturm et al. are briefly explored. Limitations of the model are discussed, extensions to the model are foreshadowed, and an example is given of a global application. If further testing demonstrates that the model gives adequate estimates of seasonal snowpack response for a wider range of locations, we might envisage applications of this approach to (i) definition of hydrological similarity indices in snow-dominated regions (ii) interpretation of output from complex simulation models covering a wide range of environments (iii) screening-level analyses of sensitivity to climate variations (iv) low-dimensional modeling where there are limited data or computation resources or technical expertise.
In this study, we examined the associations of personality traits of the Big Five model with work engagement, and tested a theoretical model in which these associations are mediated by the positive ...state of psychological meaningfulness (perceptions that work is valuable and meaningful). In a sample of 238 UK working adults, we found that the personality facets assertiveness and industriousness were the strongest predictors of work engagement, and that both exhibited direct and indirect effects, mediated by psychological meaningfulness. Neuroticism demonstrated a marginal indirect association with engagement, again mediated by psychological meaningfulness. Our findings offered good support for our model, explaining a pathway from personality traits to engagement. Practical implications for management are discussed.
PDF
