Reduction of proteolysis during ensilage of perennial ryegrass by protease inhibitors

Two experiments were carried out to assess the effectiveness of protease inhibitors in reducing proteolysis during ensilage. Perennial ryegrass (Lolium perenne) (279 g dry matter (DM) kg^?1, experiment 1 and 170 gDM kg^?1 experiment 2) was ensiled in laboratory silos for 82 and 50 days, respectively. With the exception of the application of formic acid (1.5 g kg^?1) plus formalin (3 g kg^?1) in experiment 1, all silages had pH values of less than 4.0 and lactic acid concentrations of greater than 100 g kg^?1 DM. Application of the cysteine endopeptidase inhibitor E-64 (1-trans-epoxysuccinyl-leucylamido(4-guanidino) butane, 22.5 mg kg^?1 reduced proteolysis during ensilage as measured by a reduction in the quantities of soluble non-protein N in silage to 0.76 and 0.91 of control values (528 and 643 g kg^?1 total N) in experiments 1 and 2, respectively. In experiment 2 increasing the application rate of E-64 from 22.5 to 45 mg kg^?1 further reduced the extent of proteolysis from 0.91 to 0.75 of control soluble non-protein N concentrations. Proteolysis was also reduced in experiment 2 by two other cysteine endopeptidase inhibitors, antipain (32 mg kg^?1, 0.81 of control) and cystain (1.2 mg kg^?1; 0.89 of control). Pepstatin A (300 mg kg^?1), an inhibitor of aspartic acid endopeptidases, did not reduce soluble non-protein N concentrations in experiment 1 but did do so in experiment 2 (0.81 of control). Treatment of grass at ensiling with Lactobacillus plantarum (10⁶ g^?1) reduced silage non-protein N concentrations to 0.83 of the control. The effects of E-64 and pepstatin A and of E-64 and L plantarum in experiment 2 were addive. Cysteine endopeptidases therefore play an important role in protein breakdown during ensilage.     

Network support for IP traceback

This paper describes a technique for tracing anonymous packet flooding attacks in the Internet back toward their source. This work is motivated by the increased frequency and sophistication of denial-of-service attacks and by the difficulty in tracing packets with incorrect, or “spoofed,” source addresses. We describe a general purpose traceback mechanism based on probabilistic packet marking in the network. Our approach allows a victim to identify the network path(s) traversed by attack traffic without requiring interactive operational support from Internet service providers (ISPs). Moreover, this traceback can be performed “post mortem”-after an attack has completed. We present an implementation of this technology that is incrementally deployable, (mostly) backward compatible, and can be efficiently implemented using conventional technology     

Measuring ISP topologies with Rocketfuel

To date, realistic ISP topologies have not been accessible to the research community, leaving work that depends on topology on an uncertain footing. In this paper, we present new Internet mapping techniques that have enabled us to measure router-level ISP topologies. Our techniques reduce the number of required traces compared to a brute-force, all-to-all approach by three orders of magnitude without a significant loss in accuracy. They include the use of BGP routing tables to focus the measurements, the elimination of redundant measurements by exploiting properties of IP routing, better alias resolution, and the use of DNS to divide each map into POPs and backbone. We collect maps from ten diverse ISPs using our techniques, and find that our maps are substantially more complete than those of earlier Internet mapping efforts. We also report on properties of these maps, including the size of POPs, distribution of router outdegree, and the interdomain peering structure. As part of this work, we release our maps to the community.     

A Neutron and X‐Ray Diffraction Study of Bioglass® with Reverse Monte Carlo Modelling

A class of melt‐quenched silicate glasses, containing calcium, phosphorus and alkali metals, and having the ability to promote bone regeneration and to fuse to living bone, creating strong implants with less danger of interfacial instability than previous materials, is produced commercially as Bioglass^® and sold under the brand names of PerioGlas^®, NovaBone^® and NovaBone‐C/M^®. We have collected the first high energy X‐ray and neutron diffraction data, on this important material in the hope of providing more direct experimental insight into the glass structure. Similarly, the first solid state MAS (magic angle spinning) ²⁹Si, ³¹P, and ²³Na NMR data on the material is presented. The diffraction data has been modeled using the reverse Monte Carlo (RMC) method to allow the identification of the atomic‐scale structural features present; the solid state NMR data is used explicitly within the model‐building process as a constraint on the connectivity of the network. The ²⁹Si NMR suggests that the host silica network primarily consists of chains and rings of Q² SiO₄ tetrahedra, with some degree of cross linking as represented by the presence of Q³ units. The diffraction‐based RMC model suggests a Na–O distance of 2.35 Å and a corresponding coordination of ～ 6; the coordination number is supported by the ²³Na NMR data presented here which reveals that the likely sodium environment is six‐coordinate in pseudo‐octahedral arrangement. The RMC model provides evidence for the non‐uniform distribution of Ca, which is in line with previous molecular dynamics simulation results, and the data is also suggestive of CaO as the associated structural motif within the high calcium content regions of the glass.     

ANTS: network services without the red tape

How well distributed computing systems perform depends a great deal on the network services used to move information among their machines. Yet despite this close correspondence, network services have evolved much more slowly than any other part of the distributed system environment. It is not that the networking community lacks innovative ideas: Internet Protocol version 6, Mobile IP, IP Multicast, and Integrated/Differentiated Services aim to support multimedia applications more effectively and to accommodate more hosts, many of them mobile. Unfortunately, progress in implementing these solutions lags far behind the identified need. The main problem is the way network protocols must change. First, network protocols are the main vehicle for achieving interoperability, so any candidate internetworking protocol has to become a standard. This means possibly years between the time someone identifies a need and the time everyone agrees on how to address it. Once the new protocol has been accepted, more delays occur because it has to be deployed manually and in a way that is compatible with the existing protocols. The paper discusses ANTS, a new approach to deploying network services, which bases interoperability on a programmable network model, not on individual networking protocols. The promise is automatic protocol upgrades, which can hasten progress toward a more responsive Internet     

Introducing new Internet services: why and how

Active networks permit applications to inject programs into the nodes of local and, more important, wide area networks. This supports faster service innovation by making it easier to deploy new network services. In this article, we discuss both the potential impact of active network services on applications and how such services can be built and deployed. We explore the impact by suggesting sample uses and arguing how such uses would improve application performance. We explore the design of active networks by presenting a novel architecture, ANTS (active network transport system), that adds extensibility at the network layer and allows for incremental deployment of active nodes within the Internet. In doing so, ANTS tackles the challenges of ensuring that the flexibility offered by active networks does not adversely impact performance or security. Finally, we demonstrate how a new network service may be expressed in ANTS     

Sol–gel preparation and high-energy XRD study of (CaO)<Subscript>x</Subscript>(TiO<Subscript>2</Subscript>)<Subscript>0.5−x</Subscript>(P<Subscript>2</Subscript>O<Subscript>5</Subscript>)<Subscript>0.5</Subscript> glasses (x = 0 and 0.25)

Glasses from the CaO–TiO₂–P₂O₅ system have potential use in biomedical applications. Here a method for the sol–gel synthesis of the ternary glass (CaO)_0.25(TiO₂)_0.25(P₂O₅)_0.5 has been developed. The structures of the dried gel and heat-treated glass were studied using high-energy X-ray diffraction. The structure of the binary (TiO₂)_0.5(P₂O₅)_0.5 sol–gel was studied for comparison. The results reveal that the heat-treated (CaO)_0.25(TiO₂)_0.25(P₂O₅)_0.5 glass has a structure based on chains and rings of PO₄ tetrahedra, held together by a combination of electrostatic interaction with Ca²⁺ ions and by corner-sharing oxygen atoms with TiO₆ octahedra. In contrast, the (TiO₂)_0.5(P₂O₅)_0.5 glass has a structure based on isolated P₂O₇ units linked together by corner-sharing with TiO₆ groups. The results suggest that both the dried gels possess open porous structures. For the (CaO)_0.25(TiO₂)_0.25(P₂O₅)_0.5 sample there is a significant increase in Ca–O coordination number with heat treatment.     

A survey of active network research

Active networks are a novel approach to network architecture in which the switches (or routers) of the network perform customized computations on the messages flowing through them. This approach is motivated by both lead user applications, which perform user-driven computation at nodes within the network today, and the emergence of mobile code technologies that make dynamic network service innovation attainable. The authors discuss two approaches to the realization of active networks and provide a snapshot of the current research issues and activities. They illustrate how the routers of an IP network could be augmented to perform such customized processing on the datagrams flowing through them. These active routers could also interoperate with legacy routers, which transparently forward datagrams in the traditional manner     

ViewStation applications: implications for network traffic

This paper describes applications built on the ViewStation, a distributed multimedia system based on Unix workstations and a gigabit per second local area network. A key tenet of the ViewStation project is the delivery of media data not just to the desktop but all the way to the application program. As processing power continues to improve, our approach enables applications that perform intensive processing of audio and video data. We hypothesize that as media data are shaped by this software-based processing, the resultant network traffic patterns will be dominated more by software behavior than by so-called real-time issues. We have written applications that directly process live video to provide more responsive human-computer interaction. We have also developed applications to explore the potential of media processing to support content-based retrieval of prerecorded television broadcasts. These applications perform intelligent processing on video, as well as straightforward presentation. They demonstrate the utility of network-based multimedia systems that deliver audio and video data all the way to the application. The network requirements of the applications are modeled as a combination of bursty transfers and periodic packet-trains     

Ti K-edge XANES study of the local environment of titanium in bioresorbable TiO2–CaO–Na2O–P2O5 glasses

Ti K-edge XANES (X-ray absorption near edge structure) spectroscopy has been used to study the local coordination of titanium in biocompatible and bioresorbable TiO₂–CaO–Na₂O–P₂O₅ glasses. Both conventional melt-quenched glasses of composition (TiO₂) _x (CaO)_0.30(Na₂O)_(0.20−x)(P₂O₅)_0.50, where x = 0.01, 0.03 and 0.05, and sol–gel derived (TiO₂)_0.25(CaO)_0.25(P₂O₅)_0.50 glass have been studied. The results show that in all the materials studied, titanium is surrounded by an octahedron of oxygen atoms. Further analysis reveals that the TiO₆ site in the amorphous samples is not heavily distorted relative to that in rutile, anatase or CaSiTiO₅. The spectra from the (TiO₂)_0.25(CaO)_0.25(P₂O₅)_0.50 sol–gel samples reveal greater distortion in the TiO₆ site in the dried gel compared to the heat-treated sol–gel glass. The XANES spectra from melt-quenched glass samples soaked in distilled water for various times do not shown any evidence of degradation of the titanium site over periods of up to 14 days.