BACKGROUND/AIMS Deturgescence of the corneal stroma is controlled by the pumping action of the endothelial layer and can be monitored by measurement of central corneal thickness (pachymetry). Loss or ...damage of endothelial cells leads to an increase in corneal thickness, which may ultimately induce corneal decompensation and loss of vision. Little is known about the effect of moderate reductions in endothelial cell number on the thickness of the corneal stroma. This study aimed to investigate this matter further using patients who had incurred moderate decreases in their endothelial cell counts as a result of cataract surgery. METHODS Central corneal thickness was measured 1 day before surgery, 1 day after surgery, and again at 3 months or 1 year. Endothelial cell counts were also performed 1 day before surgery and thereafter at 3 months or 1 year after surgery. The relationship between these two parameters was assessed statistically. Precise measurements of central corneal thickness were made by optical low coherence reflectometry. For comparative purposes, this parameter was also determined by ultrasonic pachymetry. Central corneal endothelial cell numerical density was estimated on photomicrographs taken with a specular microscope. RESULTS All patients had significant postoperative corneal swelling on the day after surgery; preoperative values were restored by 3 and 12 months, even though significant endothelial cell losses had occurred. No correlation existed between central corneal thickness and central corneal endothelial cell numerical density. Measurements estimated by ultrasonic pachymetry were more variable and significantly higher than those determined by optical low coherence reflectometry. CONCLUSION As long as the numerical density of the corneal endothelial cells does not fall below the physiological threshold, a moderate decrease in this parameter does not compromise the pumping activity of the layer as a whole.
•This article provides an inventory model for a serial supply chain with multiple suppliers and time varying demand.•The model minimizes the total cost of purchasing, production, inventory setup and ...holding, and transportation.•Considering lead times, necessary feasibility conditions regarding the demand at the last stage are established.•Actual transportation costs are modeled by exact piecewise linear functions.•Our results show that inventory setup and holding costs can affect supplier selection and order lot sizing decisions.
Considering the inherent connection between supplier selection and inventory management in supply chain networks, this article presents a multi-period inventory lot-sizing model for a single product in a serial supply chain, where raw materials are purchased from multiple suppliers at the first stage and external demand occurs at the last stage. The demand is known and may change from period to period. The stages of this production–distribution serial structure correspond to inventory locations. The first two stages stand for storage areas for raw materials and finished products in a manufacturing facility, and the remaining stages symbolize distribution centers or warehouses that take the product closer to customers. The problem is modeled as a time-expanded transshipment network, which is defined by the nodes and arcs that can be reached by feasible material flows. A mixed integer nonlinear programming model is developed to determine an optimal inventory policy that coordinates the transfer of materials between consecutive stages of the supply chain from period to period while properly placing purchasing orders to selected suppliers and satisfying customer demand on time. The proposed model minimizes the total variable cost, including purchasing, production, inventory, and transportation costs. The model can be linearized for certain types of cost structures. In addition, two continuous and concave approximations of the transportation cost function are provided to simplify the model and reduce its computational time.
This article considers the continuous version of the refueling station location problem on a tree network, which is a common structure in numerous toll roads worldwide, so as to locate a single ...alternative-fuel refueling station to maximize the traffic flow covered in round trips/day. Two reduction properties regarding the problem size and some optimality conditions are derived. Based on these conditions, an exact polynomial algorithm is developed to determine the set of optimal locations for the refueling station. A small tree network example is solved to illustrate the algorithm.
•We consider the continuous version of the refueling station location problem on a tree network to maximize the traffic flow covered in round-trips/day.•Two reduction properties regarding the problem size and some optimality conditions are derived.•A polynomial algorithm is developed to determine the set of optimal locations for the refueling station.•A small tree network example is solved to illustrate the algorithm.
This paper considers a joint order acceptance and scheduling problem under a general scenario. A manufacturer receives multiple orders with a given revenue, processing time, release date, due date, ...deadline, and earliness and tardiness penalties. The manufacturer can be seen as a single-machine system. Due to limited capacity, the manufacturer cannot process every order and needs to determine the optimal set of accepted orders and corresponding production schedule such that the total profit is maximized. The manufacturer can extend its capacity with overtime by paying an additional cost. A time-indexed formulation is presented to model the problem. Two exact algorithms are proposed. The first algorithm, denoted by DPIA-GR, is a dynamic programming (DP)-based algorithm that starts by solving a relaxed version of the original model and successively recovers the relaxed constraint until an optimal solution to the original problem is achieved. The second algorithm, denoted by DPIA-LRGR, improves DPIA-GR by incorporating Lagrangian relaxation (LR). The subgradient method is employed to find the optimal Lagrangian multipliers. The relaxed model in DPIA-GR and the LR model in DPIA-LRGR can be represented using a weighted di-graph. Both algorithms are equivalent to finding the longest path in the graph and applying a graph reduction strategy to prevent unnecessary computational time and memory usage. A genetic algorithm (GA) is also proposed to solve large-scale versions of the problem. Numerical experiments show that both DPIA-GR and DPIA-LRGR solve the problem efficiently and outperform CPLEX and GA, but DPIA-LRGR offers better performance.
Surface-enhanced Raman spectroscopy (SERS) is a promising and emerging technique to analyze the cellular environment. We developed an alternative, rapid and label-free SERS-based method to get ...information about the cellular environment by analyzing cells lysates, thus avoiding the need to incorporate nanoparticles into cells. Upon sonicating and filtrating cells, we obtained lysates which, mixed with Au or Ag nanoparticles, yield stable and repeatable SERS spectra, whose overall profile depends on the metal used as substrate, but not on the buffer used for the lysis process. Bands appearing in these spectra were shown to arise mostly from the cytosol and were assigned to adenine, guanine, adenosine and reduced glutathione (GSH). Spectral differences among various cell types also demonstrated that this approach is suitable for cell type identification.
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•A rapid and label-free SERS method to analyze cellular environment is proposed.•A directly probe of cytosol without nanoparticles internalization into cells is presented.•The method allows to obtain repeatable SERS spectra of cell lysates.
The rarefied gas flow phenomenon of thermophoresis is studied experimentally on a macroscopic spherical particle with a diameter of 5.1 cm for pressures ranging from 0.01 to 10 Pa (Knudsen numbers
...$Kn$
from 10 to 0.01, respectively). Size scaling with matching Knudsen numbers makes the results applicable to microscale particles such as aerosol droplets at atmospheric pressure. Two sets of measurements are presented. The first set, complemented by numerical modelling based on the solution of the ellipsoidal statistical Bhatnagar–Gross–Krook kinetic equation, is focused on a spherical particle of high thermal conductivity in close proximity to a heated wall. The second set is conducted for the same particle placed in a linear thermal gradient established between two parallel walls. Results show the first reproducible measurements of negative thermophoretic force acting on a spherical particle in the direction from cold to hot, with values of the order of 5 % of the maximum hot to cold force production.
The severe deforestation of Brazil’s Atlantic Forest and the increasing effects of climate change underscore the need to understand how tree species respond to climate and edaphic factors. To ...identify the most important environmental drivers of coastal Atlantic Forest diversity and functional composition, we studied 42 plots of coastal Atlantic Forest (restinga), which has a high diversity of plant communities and spans strong environmental gradients. We examined how forest physiognomy and functional composition respond to changes in the environment, hydraulic, and soil properties. We tested different hypotheses relating the roles of nutrients and soil water availability in driving shifts in tropical forest diversity and functioning. We collected wood samples and leaves from ˜85% of the plant species identified in the forest inventory and estimated the community‐weighted tree height, aboveground biomass, basal area of individual plants, specific leaf area, wood density, and the total tree biomass per community by the sum of all trees’ aboveground biomass per plot. We measured water table depth and 24 physicochemical soil parameters. Hypotheses relating to these factors were formalized via both generalized additive models and piecewise structural equation models and null models of community assembly. Increasing drought, as reflected by increasing water table depth, coarse sand, and soil concentration of aluminum (>6 cmol/kg), was found to be a primary driver of shifts in all measured functional traits. Water table depth was found to be the main environmental driver of restinga species diversity, but shifts in species richness were largely decoupled from functional richness and functional dispersion. Our results suggest that decreases in soil water availability are a central driver of local phenotype–environment matching and that increasing water limitation increases the role of environmental filtering on multiple traits. Our results show that drought leads to a strong convergence (standardized effect size < −1.95) in forest function and leads to shifts to smaller statured forest in particular. These findings reveal important differences in the drivers of forest structure and functioning, suggesting that changes in local spatial variation in soil and moisture variables will be a central issue in restinga management and conservation.
The development of machine learning (ML) algorithms to address a variety of issues faced in clinical practice has increased rapidly. However, questions have arisen regarding biases in their ...development that can affect their applicability in specific populations. We sought to evaluate whether studies developing ML models from electronic health record (EHR) data report sufficient demographic data on the study populations to demonstrate representativeness and reproducibility.
We searched PubMed for articles applying ML models to improve clinical decision-making using EHR data. We limited our search to papers published between 2015 and 2019.
Across the 164 studies reviewed, demographic variables were inconsistently reported and/or included as model inputs. Race/ethnicity was not reported in 64%; gender and age were not reported in 24% and 21% of studies, respectively. Socioeconomic status of the population was not reported in 92% of studies. Studies that mentioned these variables often did not report if they were included as model inputs. Few models (12%) were validated using external populations. Few studies (17%) open-sourced their code. Populations in the ML studies include higher proportions of White and Black yet fewer Hispanic subjects compared to the general US population.
The demographic characteristics of study populations are poorly reported in the ML literature based on EHR data. Demographic representativeness in training data and model transparency is necessary to ensure that ML models are deployed in an equitable and reproducible manner. Wider adoption of reporting guidelines is warranted to improve representativeness and reproducibility.
Deterioration of footpad and hock condition and increased stress are important welfare concerns in high-density broiler production. It has been argued that environmental enrichment may help address ...these issues. We hypothesized that increasing environmental complexity by providing access to barrier perches across a range of densities should improve footpad and hock health, reduce leg fluctuating asymmetry (FA), and mitigate fear in broilers without compromising bird performance. In this study, 2,088 one-day-old broiler chicks were randomly assigned to one of the following barrier and density treatment combinations over 4 replications: simple barrier, complex barrier, or no barrier (control) and low (8 birds/m²), moderate (13 birds/m²), or high (18 birds/m²) density. In wk 7, data were collected on average tibia width and length, FA of tibia width and tibia length, footpad and hock lesions, tonic immobility, feed conversion, final BW, and mortalities. Broilers at higher densities had more severe footpad (P < 0.0001) and hock lesions (P < 0.0001). Their tibias were also longer (P < 0.0001) and less symmetric in length (P < 0.05). The tibias of birds in complex barrier pens were more symmetric in length compared with controls (P < 0.05). Barrier treatment had no effect on hock lesions, although there was a trend for simple barriers to reduce the severity of footpad lesions compared with the control treatment (P = 0.089). Birds kept in simple barrier pens were more susceptible to tonic immobility induction (P < 0.05). Final BW, feed conversion, and mortalities were neither affected by stocking density nor by barrier inclusion. In conclusion, this study shows a negative effect of high density on broiler footpad health and FA. Although barrier perches did not appear to reduce fearfulness, the improvement in footpad health suggests that simple barriers may provide key welfare benefits to broiler chickens.
This article extends a previous Economic Order Quantity (EOQ) model with two modes of transportation, namely truckload (TL) and less than truckload (LTL) carriers, by introducing all-units and ...incremental quantity discount structures into the analysis. Exact algorithms are developed for each quantity discount structure to compute optimal policies for single-stage models over an infinite planning horizon.
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