Ingress Point Research Articles

Comment on dreaded complications of mistaken identity: Hygroma versus effusion following decompressive craniotomy.

Sir, We read with interest the article “Dreaded complications of mistaken identity - hygroma versus effusion following decompressive craniotomy” by Rambarki and Rajesh[1] and commend the authors on highlighting the complication of residual collection causing mass effect on the brain after cranioplasty. However having encountered such cases ourselves, we disagree with the contention that it was the nature of the fluid within that predisposed to this complication and hold that it the encysted collection that was not freely in communication with the cerebrospinal fluid (CSF) that led to this occurrence. Subdural hygromas are relatively common following decompressive craniotomy (21-50%)[2] and it is arachnoid breach that is the cause of these collections. The fate of these collections is one of the following: In the vast majority of patients, the hygroma resolves with time and the scalp flap tends to sink in prior to cranioplasty. The time frame for the process of subdural hygroma formation has been described by Aarabi et al.[3] as peaking in the 3rd to 4th week and disappearing by 14-17 weeks after surgery Some patients have small residual collections that disappear following cranioplasty. This is because cranioplasty tends to restore the dicrotic wave form of CSF pulsations that are lost following decompressive craniotomy.[4] Restoration of this waveform aids in the absorption of CSF though arachnoid granulations (opening of which is pressure dependent) In a small minority, an in the case illustrated, an encysted collection is formed. These collections expand with ingress of CSF through a one-way valve till the time intracystic pressure reaches a level high enough to prevent further inflow of CSF. The skin is invariable stretched as is seen in the computed tomography (CT) image of this case. Any attempt to tap this fluid percutaneoulsy invariably results in a recollection. Moreover even an intraoperative lumbar puncture as was done in this case, to make the flap lax and allow proper seating of the bone flap merely drains ventricular and cisternal CSF and does not address the root issue of the encysted collection. This is borne out by the fact that if the collection in this case had been in free communication with the CSF space, xanthochromic fluid would have come out through the lumbar puncture too. The authors noted xanthochromic fluid at second surgery and regretted their inability to have identified this preoperatively as an effusion rather than a hygroma furthermore stating it resulted in the “dreaded complication.” However, the preoperative CT scan was innocuous, and it is obviously not feasible to get a magnetic resonance imaging study done in every case. Moreover, bleeding within subdural hygromas is a well-known entity that has been described previously.[3,5,6] In order to prevent this complication, we must have an appreciation of the fact that large, tense and longstanding collections are not “routine hygromas.” In addition, we must appreciate that these collections will recur following cranioplasty irrespective of their content unless certain actions are taken, such as closing the point of ingress of fluid or opening the cyst widely to allow communication with surrounding spaces. The inner layer of the cyst is adherent to the pia and often the opening through which CSF leaks cannot be found. We do not recommend a routine hunt for the site of the leak. If the point of the leak is seen, however, coagulation with bipolar at a low setting or application of fibrin glue and piece of muscle or artificial dura may help. Alternatively, thick sections of the outer layer (as the authors encountered in their case), may be excised, fluid let out, and the bone flap replaced. This is akin to incising the dura and treating a chronic subdural hematoma. There will be some subgaleal collection in the postoperative period as the fluid comes out through the craniotomy margins, but this invariably gets absorbed over time. We fail to see the benefit of repeating a duraplasty since the outer layer of the collection is not involved in the pathogenesis of this collection. Subsequent recollections may also be treated by the burr hole aspiration or a subduro-peritoneal shunt rather than going through the process of reopening the bone flap.

Asymptotic behavior of solutions of systems of dynamic equations on time scales in a set whose boundary is a combination of strict egress and strict ingress points

In this paper we study the asymptotic behavior of solutions of nonlinear dynamic systems on time scales of the formyΔ(t)=f(t,y(t)),where f:T×Rn→Rn and T is a time scale. For a given set Ω⊂T×Rn, we formulate the conditions for function f, which guarantee that at least one solution y of the above system stays in Ω. The dimension of the space of initial data generating such solutions is discussed and perturbed linear systems are considered as well. A linear system with singularity at infinity is considered as an example.

Evaluating the benefit of the core-edge separation on intradomain traffic engineering under uncertain traffic demand

To address the routing scalability as well as security problems in current Internet, core-edge separation is introduced into many proposals for the architecture of future Internet. Locator/Identifier Separation Protocol (LISP) is used in this paper to evaluate the benefits of such separation on traffic engineering. The main idea of LISP is to split the single namespace for current IP addresses into two subsets, edge network address called Endpoint Identifier (EID) and core network address called routing locator (RLOC), in which a mapping system is required to support the EID-to-RLOC mapping services. Although many researchers have pointed out that EID-to-RLOC mapping assignment (ERMA) could provide enhanced traffic engineering capabilities, little research has been done on the concrete ERMA method. In this paper, we derive an optimizing ERMA (ERMAO) framework and make quantitative analysis of improvement of traffic engineering for multi-homed edge network, where ERMA could be tuned to specify the ingress points of inbound traffic. The framework incorporates two component, traffic demand and link weights, to represent real network. Accordingly, on the condition that traffic demand is uncertain but lies in a defined region, ERMA-only optimization problem in the network with given link weights and joint optimization problem of ERMA and link weights are proposed, respectively. To make the joint optimization problem of ERMA and link weights tractable, one local search algorithm, Optimized Stepsize Algorithm, is presented. Experimental results demonstrate the accuracy of these theoretic models, and the maximum link utilization is decreased by tuning ERMA.

Preliminary reactor physics assessment of the HTR module with 14% enriched UCO fuel

Preliminary reactor physics assessment of the HTR module with 14% enriched UCO fuel

Public Faith and the Politics of Faith: A Review Essay

A symposium entitled In the Presence of Faith: An Interdisciplinary Symposium on Southern African Studies of Religion was held in Johannesburg from 24 to 26 February 2010.1 This review essay outlines our rationale for the symposium, highlights its most pressing debates, and introduces the papers included in this special edition of the journal for the Study of Religion, an edition entitled Public and the Politics of Faith.The SymposiumThere were a number of reasons to call together a symposium of this nature. As organisers and in our own work we have been struck by the very limited extent of inter-disciplinary reading, discussion or collaboration about Our first wish was to create a place where scholars from different disciplines who have an interest in religion could converse together and be exposed to a diversity of questions, methods and literatures. In doing this, we hoped to open a debate about how religion has been studied in Southern Africa, what is missing and where the field should be moving. Drawing on the experience of Wiser' s 2007 Reasons of event, the organisers made efforts to invite the participation of historians, sociologists and anthropologists as well as those working from religious studies departments.Our second wish was to invite and stimulate more empirical attention to religion, particularly by social science and humanities scholars. We also hoped to raise a discussion on topics not normally encountered under the purview of religion in the social sciences. We were interested in the relationship between religion and the state, both in how religious communities attempt to influence the state, but also how the state structures its relationship with religious communities. The relationship of African nationalism to religion, both Christianity (independent and mainstream) as well as traditional, was also something we felt would lead to productive discussion. We were also interested in topics we felt had been neglected in the regional scholarship, such as personal conceptions and appreciations of faith; the public role of Christians who attend mainstream churches in Southern Africa; and the need to engage between traditional, independent and mainstream forms of religion in our theory and research. And we sought to pay attention to some of the growing religious phenomena of the last two decades, not least of which is the increasing Pentecostal involvement in public life. There is a great deal of work yet to be done on this.As part of our planning we carefully weighed up the use of our words. In choosing our symposium title, we opted for the more polysemie word faith, instead of the more normative religion. The former, we felt, offered a point of ingress into the symposium of a wider set of views on spiritual practice; it also offered a way to move beyond more dogmatic understandings of Faith also seemed to offer a way for comparative discussions between some of the major world religions practised in the region, allowing for a symposium in which scholars of Islam, Judaism, African spirituality and Christianity could speak alongside one another.A third rationale for the symposium lay in the great need for scholars working in South Africa and other Southern African countries to engage in dialogue on One reason is that there is an increasingly dense network of religious and labour migration across our respective borders. A regional perspective on such migration and the study of transnational religious communities is increasingly imperative.The call for papers elicited an enthusiastic response. Not surprisingly, perhaps, the majority of abstracts were theological in orientation. The planning group decided to exclude them. Many reflected a narrow focus on Biblical scholarship, or were poorly-researched from a social scientific perspective. As such, they did not meet the requirements of our call for papers. The high volume of scholarly theological and Biblical publishing in South Africa does not evidence much attention to most of the issues referred to above. …

Free-space input and output coupling to an embedded fiber optic strain sensor: dual-ended interrogation via transmission

In this paper, we report a novel method of free-space passive optical coupling to completely embedded, transmission-based fiber Bragg grating (FBG) sensors. Fiber optic sensors (FOS's) have attracted intense research and commercial interest. A major challenge in implementing embedded FOS's, however, is improving upon the cumbersome and fragile ingress/egress techniques commonly used for bringing the sensing light into and out of the structures. In this paper, we successfully couple free-space light into and out of an embedded FBG sensor, without the use of physical connectorization. This coupling is enabled by splicing a multimode fiber (MMF) to a single mode fiber Bragg grating (SMFBG), and using hand polishing to integrate 45° mirrors onto the ingress and egress points of the MMF and SMFBG, respectively. We determine the total loss of the system to be 23 dB, which is considerably better than previous studies that did not use this hand polishing technique. We also demonstrate the application of this free-space coupling technique to strain measurement with a maximum strain of about 2000 µV. With this approach, no pigtailing of optical fibers is needed, and the FBG sensors can be completely embedded inside the structures, greatly increasing system simplicity and robustness.

Overview of Traceback Mechanisms and Their Applicability

As an increasing number of businesses and services depend on the Internet, protecting them against DDoS (Distributed Denial of Service) attacks becomes a critical issue. A traceback is used to discover technical information concerning the ingress points, paths, partial paths or sources of a packet or packets causing a problematic network event. The traceback mechanism is a useful tool to identify the attack source of the (DDoS) attack, which ultimately leads to preventing against the DDoS attack. There are numerous traceback mechanisms that have been proposed by many researchers. In this paper, we analyze the existing traceback mechanisms, describe the common security capabilities of traceback mechanisms, and evaluate them in terms of the various criteria. In addition, we identify typical application of traceback mechanisms.

Correlation-Based Traffic Analysis Attacks on Anonymity Networks

In this paper, we address attacks that exploit the timing behavior of TCP and other protocols and applications in low-latency anonymity networks. Mixes have been used in many anonymous communication systems and are supposed to provide countermeasures to defeat traffic analysis attacks. In this paper, we focus on a particular class of traffic analysis attacks, flow-correlation attacks, by which an adversary attempts to analyze the network traffic and correlate the traffic of a flow over an input link with that over an output link. Two classes of correlation methods are considered, namely time-domain methods and frequency-domain methods. Based on our threat model and known strategies in existing mix networks, we perform extensive experiments to analyze the performance of mixes. We find that all but a few batching strategies fail against flow-correlation attacks, allowing the adversary to either identify ingress and egress points of a flow or to reconstruct the path used by the flow. Counterintuitively, some batching strategies are actually detrimental against attacks. The empirical results provided in this paper give an indication to designers of Mix networks about appropriate configurations and mechanisms to be used to counter flow-correlation attacks.

AS-level source routing for multi-provider connection-oriented services

In this paper, we study the inter-domain Autonomous System (AS)-level routing problem within an alliance of ASs. We first describe the framework of our work, based on the introduction of a service plane for automatic multi-domain service provisioning. We adopt an abstract representation of domain relationships by means of directional metrics which are applied to a triplet (ingress point, transit AS, egress point) where the ingress and egress points can be ASs or routers. Then, we focus on the point-to-point and multipoint AS-level routing problems that arise in such an architecture. We propose an original approach that reaches near optimal solutions with tractable computation times. A further contribution of this paper is that a heavy step in the proposed heuristic can be precomputed, independently of the service demands. Moreover, we describe how in this context AS-level path diversity can be considered, and present the related extension of our heuristic. By extensive tests on AS graphs derived from the Internet, we show that our heuristic is often equal or a few percent close to the optimal, and that, in the case of precomputation, its time consumption can be much lower than with other well-known algorithms.

Multi-stage response to contaminant ingress into water distribution systems and probability quantification

A multi-stage response procedure for identifying possible ingress nodes (PINs) and quantifying the likelihood that a PIN in a given water distribution system is the actual point of ingress is described. The procedure uses data mining to successively decrease the number of PINs based on a pre-constructed database. In each stage, query sentences are executed to locate the PINs and a Euclidean distance is proposed to estimate the probability, to allow the identification of locations with the highest probabilities of being the true ingress location. As demonstrated in a case study, the ranges of PINs are reduced in the 1st, 2nd, and 3rd stages; except the first sensor alarm, the Euclidean distance metric can identify the true ingress node with the program run-time of less than 2 min; the multi-stage procedure saves roughly 3 h in identifying the true ingress node after the second sensor alarm, instead of waiting for a third sensor alarm to provide the location information. The multi-stage response procedure is shown to be an effective and efficient way for identification and probability quantification of PINs.

The development and characteristics of periderm and rhytidome in Eucalyptus marginata

To understand the pathway used by Phytophthora cinnamomi Rands to penetrate the bark of jarrah, the present study describes unwounded periderm and rhytidome development. Periderm formation is described from its initiation in 4-week-old seedlings to the formation of rhytidome in saplings. Periderm in young seedlings consists of a single type of phellem, namely thin-walled suberised cells. In older seedlings where multiple layers of periderm have formed, layers of thick-walled lignified phellem cells in compacted bands alternate with thin-walled suberised cells. Rhytidome formation in older lignotuberous seedlings and in sapling jarrah occurs through the isolation of secondary phloem by periderm. The rhytidome consists of expanded and partially disintegrated secondary phloem tissue sandwiched between layers of phellem cells. Localised periderm formation beneath stomata results in the formation of lenticels, which are ephemeral features. Superficial periderms occur at sites of leaf and shoot abscission, and of lateral shoot emergence. Concealed axillary shoots lack cuticle on emergence. As the trees age, the internal production of lignified and suberised periderm and rhytidome results in an impenetrable barrier to invasion by P. cinnamomi. However, external sites including lenticels and leaf and shoot abscission and emergence areas, all provide points of ingress in unwounded stems.

Analysis of point-to-point packet delay in an operational network

In this paper we perform a detailed analysis of point-to-point packet delay in an operational tier-1 network. The point-to-point delay is the time between a packet entering a router in one PoP (an ingress point) and its leaving a router in another PoP (an egress point). It measures the one-way delay experienced by packets from an ingress point to an egress point across an ISP's network and provides the most basic information regarding the delay performance of the ISP's network. Using packet traces captured in the operational network, we obtain precise point-to-point packet delay measurements and analyze the various factors affecting them. Through a simple, step-by-step, systematic methodology and careful data analysis, we identify the major network factors that contribute to point-to-point packet delay and characterize their effect on the network delay performance. Our findings are: 1) delay distributions vary greatly in shape, depending on the path and link utilization; 2) after constant factors dependent only on the path and packet size are removed, the 99th percentile variable delay remains under 1 ms over several hops and under link utilization below 90% on a bottleneck; 3) a very small number of packets experience very large delay in short bursts

Temporal moisture content variability beneath and external to a building and the potential effects on vapor intrusion risk assessment

Migration of vapors from organic chemicals residing in the subsurface into overlying buildings is known as vapor intrusion. Because of the difficulty in evaluating vapor intrusion by indoor air sampling, models are often employed to determine if a potential indoor inhalation exposure pathway exists and, if such a pathway is complete, whether long-term exposure increases the occupants' risk for cancer or other toxic effects to an unacceptable level. For site-specific vapor intrusion assessments, moisture content is, at times, determined from soil cores taken in open spaces between buildings. However, there is little published information on how moisture content measured outside a building structure compares with the moisture content directly beneath the building - where the values are most critical for vapor intrusion assessments. This research begins to address these issues by investigating the movement of soil moisture next to and beneath a building at a contaminated field site and determining the effect on vapor intrusion risk assessment. A two-dimensional, variably-saturated water flow model, HYDRUS-2D, is used with 2 years of hourly, local rainfall data to simulate subsurface moisture content in the vicinity of a hypothetical 10 x 10-m building slab at a contaminated field site. These moisture content values are used in vapor intrusion risk assessment simulations using the Johnson and Ettinger model with instantaneous and averaged moisture contents. Results show that vapor intrusion risk assessments based on moisture content determined from soil cores taken external to a building structure may moderately-to-severely underestimate the vapor intrusion risk from beneath the structure. Soil under the edges of a slab may be influenced by rainfall events and may show reduced vapor intrusion risk as a consequence. Data from a building instrumented with subslab moisture probes showed results similar to the modeling, but with a smaller difference between the subslab and outside average moisture contents. These results indicate that, depending upon the point of vapor ingress into the structure and soil type, risk-based cleanup concentrations based on outside-of-slab or default moisture content values may not be predictive of exposure to organic vapors from below a building.

Dynamic Class Mapping Scheme for Prioritized Video Transmission in Differentiated Services Network

This paper introduces a network-aware video delivery framework where the quality-of-service (QoS) interaction between prioritized packet video and relative differentiated service (DiffServ) network is taken into account. With this framework, we propose a dynamic class mapping (DCM) scheme to allow video applications to cope with service degradation and class-based resource constraint in a time-varying network environment. In the proposed scheme, an explicit congestion notification (ECN)-based feedback mechanism is utilized to notify the status of network classes and the received service quality assessment to the end-host applications urgently. Based on the feedback information, DCM agent at ingress point can dynamically re-map each packet onto a network class in order to satisfy the desired QoS requirement. Simulation results verify the enhanced QoS performance of the streaming video application by comparing the static class-mapping and the class re-mapping based on loss-driven feedback.

Guest editor's foreword

In recent years, large scale network inference has attracted significant interest within the research community. On one front, considerable progress has been made on traffic matrix estimation. Solutions have been proposed to estimate the amount of traffic flowing between any pair of ingress and egress points within an IP network simply based on the total amount of traffic recorded over IP links. On another front, efforts are being made to detect the state of the network from end to end measurements using inference techniques or to infer the traffic workload by exploiting application behavior. In essence, the full instrumentation of the state of an IP network is still considered a cost prohibitive task and inference may be the only tool we have to understand the behavior of such large scale systems. The potential benefits of the proposed estimation techniques can be great. Accurate measurement of an IP traffic matrix is essential for network design and planning. Moreover, accurate estimation of the network state can facilitate troubleshooting and performance evaluation.

Chemistry and mineralogy of outcrops at Meridiani Planum

Analyses of outcrops created by the impact craters Endurance, Fram and Eagle reveal the broad lateral continuity of chemical sediments at the Meridiani Planum exploration site on Mars. Approximately ten mineralogical components are implied in these salt-rich silicic sediments, from measurements by instruments on the Opportunity rover. Compositional trends in an apparently intact vertical stratigraphic sequence at the Karatepe West ingress point at Endurance crater are consistent with non-uniform deposition or with subsequent migration of mobile salt components, dominated by sulfates of magnesium. Striking variations in Cl and enrichments of Br, combined with diversity in sulfate species, provide further evidence of episodes during which temperatures, pH, and water to rock ratios underwent significant change. To first order, the sedimentary sequence examined to date is consistent with a uniform reference composition, modified by movement of major sulfates upward and of minor chlorides downward. This reference composition has similarities to martian soils, supplemented by sulfate anion and the alteration products of mafic igneous minerals. Lesser cementation in lower stratigraphic units is reflected in decreased energies for grinding with the Rock Abrasion Tool. Survival of soluble salts in exposed outcrop is most easily explained by absence of episodes of liquid H2O in this region since the time of crater formation.

Proportional delay differentiation provision by bandwidth adaptation of class‐based queue scheduling

AbstractSupporting quality of service (QoS) over the Internet is a very important issue and many mechanisms have already been devised or are under way towards achieving this goal. One of the most important approaches is the so‐called Differentiated Services (DiffServ) architecture, which provides a scalable mechanism for QoS support in a TCP/IP network. The main concept underlying DiffServ is the aggregation of traffic flows at an ingress (or egress) point of a network and the marking of the IP packets of each traffic flow according to several classification criteria. Diffserv is classified under two taxonomies: the absolute and the relative. In absolute DiffServ architecture, an admission control scheme is utilized to provide QoS as absolute bounds of specific QoS parameters. The relative DiffServ model offers also QoS guarantees per class but in reference to the guarantees given to the other classes defined. In this paper, relative proportional delay differentiation is achieved based on class‐based queueing (CBQ) scheduler. Specifically, the service rates allocated to the classes of a CBQ scheduler are frequently adjusted in order to obtain relative delay spacing among them. The model presented can also be exploited in order to meet absolute delay constraints in conjunction with relative delay differentiation provision. Simulation experiments verify that our model can attain relative as well as absolute delay differentiation provided that the preconditions posed are satisfied. Copyright © 2004 John Wiley & Sons, Ltd.

Development of a galvanic sensor system for detecting the corrosion damage of the steel embedded in concrete structures: Part 1. Laboratory tests to correlate galvanic current with actual damage

The correlation between sensor output and corrosion rate of reinforcing steel was evaluated by laboratory electrochemical tests in saturated Ca(OH) 2 with 3.5 wt.% NaCl. In this paper, two types of electrochemical probes were developed: galvanic cells containing of steel/copper and steel/stainless steel couples. The corrosion behavior in saturated Ca(OH) 2 solution with and without 3.5 wt.% NaCl addition for the different electrodes was investigated by potentiodynamic test. Weight loss measurement and galvanic corrosion test were conducted to obtain the corrosion rate of reinforcing steel and the charge of sensor in saturated Ca(OH) 2 solution with 3.5 wt.% NaCl addition, respectively. The results of the potentiodynamic test indicated the possibility of detecting an ingress point of chlorides by measuring the galvanic current. In galvanic corrosion tests, the galvanic current of steel/copper couple was higher than that of steel/stainless steel couple, i.e., the steel/copper sensor is more suitable for high resistance environment. The steel/stainless sensor showed a better linear correlation than the steel/copper sensor. Through the relationship between the sensor system output and the weight loss (mg/cm 2) of steel, real corrosion damage of the steel embedded in concrete can be detected.

Trajectory sampling for direct traffic observation

Traffic measurement is a critical component for the control and engineering of communication networks. We argue that traffic measurement should make it possible to obtain the spatial flow of traffic through the domain, i.e., the paths followed by packets between any ingress and egress point of the domain. Most resource allocation and capacity planning tasks can benefit from such information. Also, traffic measurements should be obtained without a routing model and without knowledge of network state. This allows the traffic measurement process to he resilient to network failures and state uncertainty. We propose a method that allows the direct inference of traffic flows through a domain by observing the trajectories of a subset of all packets traversing the network. The key advantages of the method are that (1) it does not rely on routing state; (2) its implementation cost is small; and (3) the measurement reporting traffic is modest and can be controlled precisely. The key idea of the method is to sample packets based on a hash function computed over the packet content. Using the same hash function will yield the same sample set of packets in the entire domain, and enables us to reconstruct packet trajectories.

Trajectory sampling for direct traffic observation

Traffic measurement is a critical component for the control and engineering of communication networks. We argue that traffic measurement should make it possible to obtain the spatial flow of traffic through the domain, i.e., the paths followed by packets between any ingress and egress point of the domain. Most resource allocation and capacity planning tasks can benefit from such information. Also, traffic measurements should be obtained without a routing model and without knowledge of network state. This allows the traffic measurement process to be resilient to network failures and state uncertainty. We propose a method that allows the direct inference of traffic flows through a domain by observing the trajectories of a subset of all packets traversing the network. The key advantages of the method are that (i) it does not rely on routing state, (ii) its implementation cost is small, and (iii) the measurement reporting traffic is modest and can be controlled precisely. The key idea of the method is to sample packets based on a hash function computed over the packet content. Using the same hash function will yield the same sample set of packets in the entire domain, and enables us to reconstruct packet trajectories.