ipom.fm

Abstract --Proliferation of IEEE 802.11 WLANs (Wireless Local Area Networks) is occurring at an unprecedented rate. To realize the benefits of localized yet unlicensed and high-bandwidth WLANs along with highly available but low bit-rate overlay WWANs, the MHs (Mobile Hosts) such as laptops and PDAs are being equipped with multiple wireless NICs (Network Interface Cards). Also growing strongly, as a consequence, is the desire to develop a capability to trouble-shoot and manage these devices over-the-air, even when the user is in-transit, so that user's perception of quality of service and reliance on these multi-mode devices could be improved. However, a key requirement for an MH management system for such multi-mode overlay environments is the ability to handle handoffs between WLANs and WWANs, also known as vertical handoffs. So far the issue of vertical handoffs has been addressed mostly under the context of TCP (Transmission Control Protocol) based applications. A number of proposals have been made in literature which aim at maintaining TCP connections during vertical handoffs. This is achieved by either deploying mobile-IP or proxy servers, or making alterations to the protocol stack structure. For an MH management service, that may not use TCP as its underlying transport mechanism, such overheads may be deemed unnecessary and expensive. An efficient MH management system is thus needed that could, not only undertake conventional device management tasks, but also maintain access to the MH during vertical handoffs, without imposing unnecessary network or protocol stack overheads. A novel MH management scheme is proposed herein that addresses the aforementioned requirements in simple yet elegant fashion. The proposed scheme uses SNMP (Simple Network Management Protocol) for managing MHs. An SNMP agent is installed on each MH along with an appropriate MIB (Management Information Base). The mobiles are then managed by a centralized SNMP manager. The handoffs within the WWAN (horizontal handoffs) are left to the native mobility management procedures whereas vertical handoffs i.e. handoffs between WWAN and WLANs are facilitated through SNMP itself. The proposed scheme does not involve mobile IP, external proxies or alterations to the protocol stacks. Index Terms --SNMP, mobility management, MH management, vertical handoffs, Mobile IP, GPRS

Data from: Extensive horizontal gene transfer, duplication, and loss of chlorophyll synthesis genes in the algae

Background: Two non-homologous, isofunctional enzymes catalyze the penultimate step of chlorophyll a synthesis in oxygenic photosynthetic organisms such as cyanobacteria, eukaryotic algae and land plants: the light-independent (LIPOR) and light-dependent (POR) protochlorophyllide oxidoreductases. Whereas the distribution of these enzymes in cyanobacteria and land plants is well understood, the presence, loss, duplication, and replacement of these genes have not been surveyed in the polyphyletic and remarkably diverse eukaryotic algal lineages. Results: A phylogenetic reconstruction of the history of the POR enzyme (encoded by the por gene in nuclei) in eukaryotic algae reveals replacement and supplementation of ancestral por genes in several taxa with horizontally transferred por genes from other eukaryotic algae. For example, stramenopiles and haptophytes share por gene duplicates of prasinophytic origin, although their plastid ancestry predicts a rhodophytic por signal. Phylogenetically, stramenopile pors appear ancestral to those found in haptophytes, suggesting transfer from stramenopiles to haptophytes by either horizontal or endosymbiotic gene transfer. In dinoflagellates whose plastids have been replaced by those of a haptophyte or diatom, the ancestral por genes seem to have been lost whereas those of the new symbiotic partner are present. Furthermore, many chlorarachniophytes and peridinin-containing dinoflagellates possess por gene duplicates.In contrast to the retention, gain, and frequent duplication of algal por genes, the LIPOR gene complement (chloroplast-encoded chlL, chlN, and chlB genes) is often absent. LIPOR genes have been lost from haptophytes and potentially from the euglenid and chlorarachniophyte lineages. Within the chlorophytes, rhodophytes, cryptophytes, heterokonts, and chromerids, some taxa possess both POR and LIPOR genes while others lack LIPOR. The gradual process of LIPOR gene loss is evidenced in taxa possessing pseudogenes or partial LIPOR gene compliments. No horizontal gene transfer of LIPOR genes was detected.ConclusionsWe document a pattern of por gene acquisition and expansion as well as loss of LIPOR genes from many algal taxa, paralleling the presence of multiple por genes and lack of LIPOR genes in the angiosperms. These studies present an opportunity to compare the regulation and function of por gene families that have been acquired and expanded in patterns unique to each of various algal taxa

AdditionalFile5_PrimerTable

Table of degenerate and species-specific primers used to amplify por gene sequences from stramenopile algae

AdditionalFile3_MaximumLikelihoodTree_NewickFormat

Maximum-likelihood POR phylogeny in Newick format

AdditionalFile1_Alignment_NexusFormat

Nexus formatted alignment of all protein sequences used for POR phylogeny inference

AdditionalFile2_BayesianTree_NexusFormat4FigTree

Bayesian POR phylogeny in Nexus format, readable in the program FigTree

AdditionalFile4_PorSpeciesTable

Excel spreadsheet of identifying information (e.g., accessions) for all sequences used in the POR phylogeny