Mechanism Design with Limited Information: The Case of Nonlinear Pricing

We analyze the canonical nonlinear pricing model with limited information. A seller offers a menu with a finite number of choices to a continuum of buyers with a continuum of possible valuations. By revealing an underlying connection to quantization theory, we derive the optimal finite menu for the socially efficient and the revenue-maximizing mechanism. In both cases, we provide an estimate of the loss resulting from the usage of a finite n-class menu. We show that the losses converge to zero at a rate proportional to 1/n^2 as n becomes large.Mechanism design, Limited information, Nonlinear pricing, Quantization, Lloyd-max optimality

Visualisation tool to study malaria transmission using network modelling

Malaria has been described as one of the major killer diseases. There were about 219 million cases of malaria in 2010 and an estimated 660,000 deaths. This deserves urgent scientific investigations and studies on malaria transmission. Since malaria is a vector borne disease, this project aims to produce a visualisation tool to model the disease transmission through formulating a heterogeneous bipartite contact network of two node types (public places and human beings). In addition, the Hypertext Induced Topical Search (HITS) web search algorithm was adapted to implement a search engine, which uses the bipartite contact network as the input. Java was used to implement the visualisation tool. The output from this visualisation tool shows predicted hotspots which harbour the infected malaria vectors. This output was validated with UCINET 6.0 as the benchmark system. A similar dominant node ranking output was obtained when the output from the benchmark system is compared with that of the modelling tool. The resulting information is believed helpful to tackle the issue of malaria transmission from the perspective of vectors detection

Epidemiological Assessment of Risk Factors Associated with Bovine Ephemeral Fever Virus Exposure among Sheep and Goats in South Korea

Background: Bovine ephemeral fever virus (BEFV) is an arthropod-borne virus classified as a type species of the genus Ephemerovirus, family Rhabdoviridae. BEFV is the causative agent of bovine ephemeral fever (BEF), a non-contagious disease of acute febrile clinical signs in cattle and water buffalo. Some species might act as reservoir hosts, and antibodies to BEFV have also been found in asymptomatic sheep, goats, pigs, and many wild animals. This study aimed to conduct a retrospective cross-sectional serological screening in South Korea to address BEFV seroprevalence and identify risk factors for becoming seropositive for the virus in sheep and goats. Materials, Methods & Results: The apparent prevalence rates were considered to be the animal-level prevalence, defined as the proportion of serum neutralization test (SNT)-positive animals out of the total number of animals tested in the study area, and flock prevalence was defined as the proportion of SNT-positive flocks out of the total number of tested flocks in the area. A flock was classified as positive if at least one animal was SNT-positive. At the national level in 2011, 28 of 177 flocks (15.8%; 95% CI, 11.2−21.9%) and 71 of 498 heads (14.3%, 95% CI: 11.5-17.6%) that were analyzed showed serum neutralizing antibodies against BEFV. Our results revealed that age class, vector control, and geographic location affected seroprevalence to differing extents. In the univariate analysis, older age was a significant risk factor (OR, 2.327; 95% CI, 1.147-4.721; P = 0.017 in adults). The management risk factor attributes showed that preventive measures, such as routine application of insecticides in farms, decreased the odds of seropositivity for BEFV (OR, 0.514; 95% CI, 0.267-0.991; P = 0.044). Vector control was a significant protective factor, while animal species, flock size, and flock structure were not significantly associated. Differences in seroprevalence between variations in the presence of ruminant farms, lakes, or rice paddies within a 1-km radius or type of land use were not statistically significant (P > 0.05). We observed a significant difference in the individual likelihood of being positive in the southern provinces with respect to that in the northern provinces (OR, 2.166; 95% CI, 1.228-3.824; P = 0.007). Differences in seroprevalence between variations in the eastern and western regions were not statistically significant (P > 0.05). The retrospective study results showed that the virus was widely distributed in sheep and goats in South Korea, with seropositive rates ranging from 7.8% to 19.7% between 2003 and 2008.Discussion: This is the first report of circulating antibodies against BEFV in sheep and goats in South Korea. The serological prevalence of BEFV infection in sheep and goats was significantly different between different age cohorts, vector control, and geographical locations: it was higher in the older group and the southern and western regions of South Korea. Determination of seropositivity rates often leads to an understanding of virus circulation dynamics and is useful in the formulation of disease control measures. Our results demonstrated that vector control was a significant protective factor; therefore, the summer control of vectors could be better implemented in provinces with elevated seropositivity rates. The results of this seroprevalence study may serve as a basis for future epidemiological studies on BEFV infection in South Korea

Mechanism Design with Limited Information: The Case of Nonlinear Pricing

We analyze the canonical nonlinear pricing model with limited information. A seller offers a menu with a finite number of choices to a continuum of buyers with a continuum of possible valuations. By revealing an underlying connection to quantization theory, we derive the optimal finite menu for the socially efficient and the revenue-maximizing mechanism. In both cases, we provide an estimate of the loss resulting from the usage of a finite n-class menu. We show that the losses converge to zero at a rate proportional to 1/n2 asn becomes large

Nonlinear Pricing with Finite Information

We analyze nonlinear pricing with finite information. A seller offers a menu to a continuum of buyers with a continuum of possible valuations. The menu is limited to offering a finite number of choices representing a finite communication capacity between buyer and seller. We identify necessary conditions that the optimal finite menu must satisfy, either for the socially efficient or for the revenue-maximizing mechanism. These conditions require that information be bundled, or “quantized” optimally. We show that the loss resulting from using the n -item menu converges to zero at a rate proportional to 1 = n 2 . We extend our model to a multi-product environment where each buyer has preferences over a d dimensional variety of goods. The seller is limited to offering a finite number n of d -dimensional choices. By using repeated scalar quantization, we show that the losses resulting from using the d -dimensional n -class menu converge to zero at a rate proportional to d = n 2 / d . We introduce vector quantization and establish that the losses due to finite menus are significantly reduced by offering optimally chosen bundles

Histone deacetylase 2 is required for chromatin condensation and subsequent enucleation of cultured mouse fetal erythroblasts

Background: During the final stages of differentiation of mammalian erythroid cells, the chromatin is condensed and enucleated. We previously reported that Rac GTPases and their downstream target, mammalian homolog of Drosophila diaphanous 2 (mDia2), are required for enucleation of in vitro cultured mouse fetal liver erythroblasts. However, it is not clear how chromatin condensation is achieved and whether it is required for enucleation. Design and Methods: Mouse fetal liver erythroblasts were purified from embryonic day 14.5 pregnant mice and cultured in erythropoietin-containing medium. Enucleation was determined by flow-cytometry based analysis after treatment with histone deacetylase inhibitors or infection with lentiviral short harirpin RNA. Results: We showed that histone deacetylases play critical roles in chromatin condensation and enucleation in cultured mouse fetal liver erythroblasts. Enzymatic inhibition of histone deacetylases by trichostatin A or valproic acid prior to the start of enucleation blocked chromatin condensation, contractile actin ring formation and enucleation. We further demonstrated that histone deacetylases 1, 2, 3 and 5 are highly expressed in mouse fetal erythroblasts. Short hairpin RNA down-regulation of histone deacetylase 2, but not of the other histone deacetylases, phenotypically mimicked the effect of trichostatin A or valproic acid treatment, causing significant inhibition of chromatin condensation and enucleation. Importantly, knock-down of histone deacetylase 2 did not affect erythroblast proliferation, differentiation, or apoptosis. Conclusions: These results identify histone deacetylase 2 as an important regulator, mediating chromatin condensation and enucleation in the final stages of mammalian erythropoiesis.National Institutes of Health (U.S.) (NIH grant P01 HL 32262)Amgen, Inc.National Institutes of Health (U.S.) (Pathway to Independence Award)Leukemia & Lymphoma Society of AmericaTemasek Life Sciences Laborator

On the Fundamental Mass-Period Functions of Extrasolar Planets

Employing a catalog of 175 extrasolar planets (exoplanets) detected by the Doppler-shift method, we constructed the independent and coupled mass-period functions. It is the first time in this field that the selection effect is considered in the coupled mass-period functions. Our results are consistent with those in Tabachnik and Tremaine (2002) with the major differences that we obtain a flatter mass function but a steeper period function. Moreover, our coupled mass-period functions show that about 2.5 percent of stars would have a planet with mass between Earth Mass and Neptune Mass, and about 3 percent of stars would have a planet with mass between Neptune Mass and Jupiter Mass.Comment: Accepted by ApJ Supplement Series in Nov. 2009, Acknowledgment added in Dec. 2009, a Reference-Based Catalog of Exoplanets can be obtained electronically from Appendix A of the latex file or from the authors for further studies

The Magneto-Resistive Magnetometer of BCU on the Tatiana-2 Satellite

The magneto-resistive magnetometer (MRM) of the Block of Central University (BCU) payload onboard the Tatiana-2 satellite is made of anisotropic magneto-resistive (AMR) sensor chips, which have appealing features of small size (10 × 15 × 7 mm3), light weight (2 grams) and low power consumption (100 mW). The small MRM is packaged together with other instrument/subsystems of the BCU into a 1.6 kg payload box for convenient installation. In this report, we present the design, calibration, and flight data analysis of the MRM. In particular, the detailed methods of pre-flight calibrations are described. The calibrated data revealed typical patterns of the global geo-magnetic field structure and of field-aligned current (FAC) distribution in the high latitude ionosphere, though the MRM of BCU only has a resolution of 24 nT and a sampling rate of 2.22 Hz. Moreover, the current density derived from our magnetic field measurements are about 2 and 3 μA m-2, respectively, for downward and upward FAC, which are comparable to those typically observed at auroral latitudes during a quiet geomagnetic condition