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Abstract—Virtual Network Functions (VNFs) are software implementation of middleboxes (MBs) (e.g., firewalls and proxy servers) that provide performance and security guarantees for virtual machine (VM) cloud applications. In this paper, we study a new VM flow migration problem for dynamic VNF-enabled cloud data centers (VDCs). The goal is to migrate the VM flows in the dynamic VDCs to minimize the total network traffic while load-balancing VNFs with limited processing capabilities. We refer to the problem as FMDV: flow migration in dynamic VDCs. We propose an optimal and efficient minimum cost flow-based flow migration algorithm and two benefit-based efficient heuristic algorithms to solve the FMDV. Via extensive simulations, we show that our algorithms are effective in mitigating dynamic cloud traffic while achieving load balance among VNFs. In particular, all our algorithms reduce dynamic network traffic in all cases and our optimal algorithm always achieves the best traffic-mitigation effect, reducing the network traffic by up to 28% compared to the case without flow migration. 

Scientific argumentation and modeling are both core practices in learning and doing science. However, they are challenging for students. Although there is considerable literature about scientific argumentation or modeling practice in K-12 science, there are limited studies on how engaging students in modeling and scientific argumentation might be mutually supportive. This study aims to explore how 5th graders can be supported by our designed mediators as they engage in argumentation and modeling, in particular, model revision. We implemented a virtual afterschool science club to examine how our modeling tool – MEME (Model and Evidence Mapping Environment), provided evidence, peer comments, and other mediators influenced students in learning about aquatic ecosystems through developing a model. While both groups that we examined constructed strong arguments and developed good models, we show how the mediators played different roles in helping them be successful. 

Abstract We present the second and final release of optical spectroscopy of Type Ia supernovae (SNe Ia) obtained during the first and second phases of the Carnegie Supernova Project (CSP-I and CSP-II). The newly released data consist of 148 spectra of 30 SNe Ia observed in the course of CSP-I and 234 spectra of 127 SNe Ia obtained during CSP-II. We also present 216 optical spectra of 46 historical SNe Ia, including 53 spectra of 30 SNe Ia observed by the Calán/Tololo Supernova Survey. We combine these observations with previously published CSP data and publicly available spectra to compile a large sample of measurements of spectroscopic parameters at maximum light, consisting of pseudo-equivalent widths and expansion velocities of selected features for 232 CSP and historical SNe Ia (including more than 1000 spectra). Finally, we review some of the strongest correlations between spectroscopic and photometric properties of SNe Ia. Specifically, we define two samples: one consisting of SNe Ia discovered by targeted searches (most of them CSP-I objects) and the other composed of SNe Ia discovered by untargeted searches, which includes most of the CSP-II objects. The analyzed correlations are similar for both samples. We find a larger incidence of SNe Ia belonging to the cool and broad-line Branch subtypes among the events discovered by targeted searches, shallow-silicon SNe Ia are present with similar frequencies in both samples, while core normal SNe Ia are more frequent in untargeted searches. 

Hagfishes are an ancient group of benthic marine craniates that are found in deep or cold waters around the world. Among the 83 valid species, four are described from the Galapagos Islands: Eptatretus bobwisneri, E. grouseri, E. mccoskeri and Rubicundus lakeside. During a recent expedition to the archipelago, six species of hagfishes were collected, including four undescribed species of the genera Eptatretus (Eptatretus goslinei sp. nov.) and Myxine (Myxine greggi sp. nov., M. martinii sp. nov. and M. phantasma sp. nov.). In this paper, we provide a review of the eight species of hagfishes from the Galapagos Islands, including new diagnoses and an identification key for all species. Myxine phantasma is remarkable in that it is the only species of Myxine known to completely lack melaninbased pigments. Our species delineations were based on both morphological and molecular analyses. A phylogenetic hypothesis based on molecular data suggests that Galapagos hagfishes arose from multiple independent colonisations of the islands from as many as five different ancestral lineages. The large number of endemic hagfishes in the geologically young Galapagos Islands suggests that there is much global hagfish diversity yet to be discovered. 

Hagfishes are an ancient group of benthic marine craniates that are found in deep or cold waters around the world. Among the 83 valid species, four are described from the Galapagos Islands: Eptatretus bobwisneri, E. grouseri, E. mccoskeri and Rubicundus lakeside. During a recent expedition to the archipelago, six species of hagfishes were collected, including four undescribed species of the genera Eptatretus (Eptatretus goslinei sp. nov.) and Myxine (Myxine greggi sp. nov., M. martinii sp. nov. and M. phantasma sp. nov.). In this paper, we provide a review of the eight species of hagfishes from the Galapagos Islands, including new diagnoses and an identification key for all species. Myxine phantasma is remarkable in that it is the only species of Myxine known to completely lack melanin-based pigments. Our species delineations were based on both morphological and molecular analyses. A phylogenetic hypothesis based on molecular data suggests that Galapagos hagfishes arose from multiple independent colonisations of the islands from as many as five different ancestral lineages. The large number of endemic hagfishes in the geologically young Galapagos Islands suggests that there is much global hagfish diversity yet to be discovered.