Incentive pricing in multiclass systems

In modern communication networks which offer multiple classes of services, an appropriate assignment of service classes to users (or applications) will have a key influence on the performance profile. Differentiated pricing is an important tool for guiding the user's choice. We consider a basic model for a multiclass system that offers multiclass services to multiple types of traffic, and propose a pricing framework which is based on the concept of nominal traffic assignment. Users (or their associated traffic) are categorized into a finite number of traffic types, which are distinct in their performance utilities at the different service classes. The system administrator specifies a required traffic assignment, which associates with each traffic type a nominal service class. Users, on the other hand, choose service classes so as to optimize their own performance. Optimal prices should provide incentives for the users to assign each traffic type to its nominal service class. Our goal is to implement a simple pricing scheme that provides such incentives. We establish necessary and sufficient conditions for the existence of optimal prices and provide an algorithm for their computation. We indicate that optimal prices can tolerate fluctuations in the various parameters. Next, we propose a distributed algorithm, which can be used by the system to compute optimal prices even when it does not have sufficient knowledge of traffic characteristics. We then generalize our analysis to an extended model, which explicitly includes congestion effects. This revised version was published online in June 2006 with corrections to the Cover Date.     

Functional Free‐Standing Graphene Honeycomb Films

Fabricating free‐standing, three‐dimensional (3D) ordered porous graphene structure can service a wide range of functional materials such as environmentally friendly materials for antibacterial medical applications and efficient solar harvesting devices. A scalable solution processable strategy is developed to create such free‐standing hierarchical porous structures composed of functionalized graphene sheets via an “on water spreading” method. The free‐standing film shows a large area uniform honeycomb structure and can be transferred onto any substrate of interest. The graphene‐based free‐standing honeycomb films exhibit superior broad spectrum antibacterial activity as confirmed using green fluorescent protein labeled Pseudomonas aeruginosa PAO1 and Escherichia coli as model pathogens. Functional nanoparticles such as titanium dioxide (TiO₂) nanoparticles can be easily introduced into conductive graphene‐based scaffolds by premixing. The formed composite honeycomb film electrode shows a fast, stable, and completely reversible photocurrent response accompanying each switch‐on and switch‐off event. The graphene‐based honeycomb scaffold enhances the light‐harvesting efficiency and improves the photoelectric conversion behavior; the photocurrent of the composite film is about two times as high as that of the pure TiO₂ film electrode. Such composite porous films combining remarkably good electrochemical performance of graphene, a large electrode/electrolyte contact area, and excellent stability during the photo‐conversion process hold promise for further applications in water treatment and solar energy conversion.     

Cranial Base Synchondrosis Lacks PTHrP-Expressing Column-Forming Chondrocytes

The cranial base contains a special type of growth plate termed the synchondrosis, which functions as the growth center of the skull. The synchondrosis is composed of bidirectional opposite-facing layers of resting, proliferating, and hypertrophic chondrocytes, and lacks the secondary ossification center. In long bones, the resting zone of the epiphyseal growth plate houses a population of parathyroid hormone-related protein (PTHrP)-expressing chondrocytes that contribute to the formation of columnar chondrocytes. Whether PTHrP⁺ chondrocytes in the synchondrosis possess similar functions remains undefined. Using Pthrp-mCherry knock-in mice, we found that PTHrP⁺ chondrocytes predominantly occupied the lateral wedge-shaped area of the synchondrosis, unlike those in the femoral growth plate that reside in the resting zone within the epiphysis. In vivo cell-lineage analyses using a tamoxifen-inducible Pthrp-creER line revealed that PTHrP⁺ chondrocytes failed to establish columnar chondrocytes in the synchondrosis. Therefore, PTHrP⁺ chondrocytes in the synchondrosis do not possess column-forming capabilities, unlike those in the resting zone of the long bone growth plate. These findings support the importance of the secondary ossification center within the long bone epiphysis in establishing the stem cell niche for PTHrP⁺ chondrocytes, the absence of which may explain the lack of column-forming capabilities of PTHrP⁺ chondrocytes in the cranial base synchondrosis.     

Twenty‐five years of the Information Systems Journal: A bibliometric and ontological overview

The Information Systems Journal (ISJ) published its first issue in 1991, and in 2015, the journal celebrated its 25th anniversary. This study presents an overview of the leading research trends in the papers that the journal has published during its first quarter of a century via a bibliometric and ontological analysis. From a bibliometric perspective, the analysis considers the publication and citation structure of the journal. The study then develops a graphical analysis of the bibliographic material by using visualization of similarities software that employs bibliographic coupling and cocitation analysis. The work produces an ontological framework of impact and analyses the journal papers to assess qualitatively ISJ's impact. The results indicate that the journal has grown significantly over time and is now recognized as one of the leading journals in information systems. Yet challenges remain if the journal is to meet its aims in impacting and setting the agenda for the development of the Information Systems field.     

Study of the Ghrelin/LEAP-2 Ratio in Humans and Rats during Different Phases of Pregnancy

The Liver-Expressed Antimicrobial Peptide 2 (LEAP-2) has emerged as an endogenous GHS-R antagonist and blunts the orexigenic action of ghrelin. This study aimed to determine the Ghrelin/LEAP-2 ratio in humans and rats during pregnancy. In humans, we conducted a nested case-control study within an observational prospective cohort. Healthy and mild preeclamptic pregnant women were studied at each trimester of gestation and three months postpartum. In addition, a group of non-pregnant women was studied into the follicular and luteal phases of the menstrual cycle. Furthermore, Ghrelin/LEAP-2 ratio was investigated in non-pregnant rats and at different periods of rat pregnancy. Human and rat serum ghrelin and LEAP-2 levels were determined using the commercially available ELISA kits. The Ghrelin/LEAP-2 ratio peak around the second trimester of gestation in healthy pregnant women (p < 0.05). Additionally, there were no statistically significant differences in Ghrelin/LEAP-2 ratio between healthy and preeclamptic pregnant women at each trimester of gestation (p > 0.05). The Ghrelin/LEAP-2 ratio in pregnant rat reached the peak around mid-gestation with a similar pattern to the human pregnancy. LEAP-2 was visualized by immunohistochemistry in human term placenta and rat placentas on days 12, 16 and 21 of pregnancy. In conclusion, this study provides the first evidence of a Ghrelin/LEAP-2 ratio peak around the half-way point of pregnancy onwards during human and rat pregnancy, and it might be associated with increased rates of weight gain during pregnancy. Thus, this study suggests that LEAP-2 and Ghrelin/LEAP-2 ratio might play an important role in maternal physiology adaptation of weight gain during pregnancy.     

Evolutionary History of Bioessential Elements Can Guide the Search for Life in the Universe

Our understanding of life in the universe comes from one sample, life on Earth. Current and next-generation space missions will target exoplanets as well as planets and moons in our own solar system with the primary goal of detecting, interpreting and characterizing indications of possible biological activity. Thus, understanding life's fundamental characteristics is increasingly critical for detecting and interpreting potential biological signatures elsewhere in the universe. Astrobiologists have outlined the essential roles of carbon and water for life, but we have yet to decipher the rules governing the evolution of how living organisms use bioessential elements. Does the suite of life's essential chemical elements on Earth constitute only one possible evolutionary outcome? Are some elements so essential for biological functions that evolution will select for them despite low availability? How would this play out on other worlds that have different relative element abundances? When we look for life in the universe, or the conditions that could give rise to life, we must learn how to recognize it in extremely different chemical and environmental conditions from those on Earth. We argue that by exposing self-organizing biotic chemistries to different combinations of abiotic materials, and by mapping the evolutionary history of metalloenzyme biochemistry onto geological availabilities of metals, alternative element choices that are very different from life's present-day molecular structure might result. A greater understanding of the paleomolecular evolutionary history of life on Earth will create a predictive capacity for detecting and assessing life's existence on worlds where alternate evolutionary paths might have been taken.     

Supporting users in finding successful matches in reciprocal recommender systems

User Modeling and User-Adapted Interaction - Online platforms which assist users in finding a suitable match, such as online-dating and job recruiting environments, have become increasingly popular...     

Catalyst design using artificial intelligence: SO2 to SO3 case study

Catalyst design is key to the improvement of chemical process efficiency. The required work for the development of new catalysts can be supported through the proper application of artificial intelligence to identify optimal compositions. A generic methodology for the application of machine learning to catalysis research is therefore outlined in this work. The catalytic oxidation of SO₂ was used to exemplify the first iteration of this methodology. 1784 data points from 31 published papers were compiled into a databank. The inlet SO₂ concentration ranged from 0 to 66 mol%. An artificial neural network (ANN) was trained on the databank in order to predict SO₂ conversion based on the catalyst composition and the reactor operating conditions (temperature, pressure, catalyst mass: volumetric flowrate ratio (w/v), and feed composition). The model achieved a root-mean-square error of 6.6%. A preliminary screening step identified 3:1 V-Mg/SiO₂ catalysts as exhibiting high conversion at 648 K. A multi-objective optimization was then performed on a single catalyst to identify solutions exhibiting high conversion and high productivity at 648 K while minimizing the catalyst cost. The optimal solution was predicted to be a 2.9 wt% V/0.2 wt% Mg/SiO₂ catalyst operating at a w/v of 7.49 kg-cat · s/m³ STP, achieving 100% SO₂ conversion with a material cost among the bottom third of cost values. Artificial intelligence can then be employed to extract useful knowledge from published catalytic data and orient future search for novel catalyst development.     

Modelling of thermal cracking effects in a two-phase concrete-like solid — a parametric investigation

Incompatibility of the physical properties of concrete constituents — the aggregate and the cement paste — gives rise to microcracking when the material is cooled to very low temperatures. The phenomenon is complex and affected by a large number of factors. An analytical model of the cracking process could be instrumental in identifying parameters for experimental investigation. A preliminary study is presented, which models concrete as a two-phase medium consisting of the coarse aggregate as inclusions in the mortar matrix. A simplified finite element procedure is employed to evaluate the effects of four parameters on crack initiating temperature and on crack volume. The parameters include two physical properties — thermal expansion coefficient and elastic modulus — and two mix factors — inclusion/matrix volume fraction and inclusion particle size. Thermal coefficient and inclusion volume fraction emerge as the major parameters affecting the fracture process, but the relationship of the two mix factors is complex.     

Mental health care benefits and perceptions of health insurance agents.

Many professionals play a role in evaluating and defining health service coverage in the current marketplace. It is useful to professional psychologists to understand how their perceptions of the current coverage of mental health services are similar to or different from those of other professionals. The authors examined the views of health insurance agents. Both psychologists and insurance agents agreed that, mental health benefits were adequate to effectively treat mild mental health problems, coverage was inadequate to treat major mental illness. Psychologists and insurance agents differed in their perceptions of whether patients and therapists used benefits unnecessarily. (PsycINFO Database Record (c) 2010 APA, all rights reserved)