Human metapneumovirus (HMPV) is a major cause of respiratory illnesses in children, the elderly and immunocompromised patients. Although this pathogen was only discovered in 2001, an enormous amount of research has been conducted in order to develop safe and effective vaccines to prevent people from contracting the disease. In this review, we summarize current knowledge about the most promising experimental B- and T-cell epitopes of human metapneumovirus for the rational design of HMPV vaccines using vector delivery systems, paying special attention to the conservation of these epitopes among different lineages/genotypes of HMPV. The prospects of the successful development of an epitope-based HMPV vaccine are discussed in the context of recent findings regarding HMPV’s ability to modulate host immunity. In particular, we discuss the lack of data on experimental human CD4 T-cell epitopes for HMPV despite the role of CD4 lymphocytes in both the induction of higher neutralizing antibody titers and the establishment of CD8 memory T-cell responses. We conclude that current research should be focused on searching for human CD4 T-cell epitopes of HMPV that can help us to design a safe and cross-protective epitope-based HMPV vaccine. Human metapneumovirus (HMPV) was first isolated in the Netherlands in 2001 . HMPV waPneumoviridae family [Metapneumovirus is an enveloped RNA virus that belongs to the e family . The vire family . Studiese family ,13.Unlike influenza, no vaccine or specific prophylaxis for HMPV has been approved for human use, despite the tremendous efforts of researchers around the world . A vacciMore advanced strategies for generating recombinant live attenuated HMPV vaccines have been explored in recent years, yielding promising results in animal models ,20,21. TRM) responses, and these TRMs can recognize evasive pathogens and promptly respond to the infection by rapidly proliferating effector T cells [Attenuated influenza viruses represent another attractive platform for the development of HMPV vaccines due to the ability of influenza viruses to induce long-lasting local and systemic immunity. Influenza vaccination campaigns are routinely implemented in many countries, and live attenuated influenza vaccines (LAIVs) have been used in clinical practice for decades without safety concerns ,35. In a T cells . HoweverIn order to induce protective immune responses against HMPV without the simultaneous development of enhanced pulmonary disease, it is critical to take into account the specific mechanisms this virus uses to modulate host immunity. In humans, higher levels of IgG and HMPV-neutralizing antibodies were associated with protection against HMPV during the winter seasons . In animT-cell immunity to HMPV infection plays an important role in virus control, but it can also contribute to pathology. In experiments on mice with T cell depletion, both CD4 and CD8 T cells were required for efficient viral clearance during primary HMPV infection; however, both subsets played a role in the enhancement of disease manifestation. Depletion of one of the subsets showed that both CD4 and CD8 T cells were engaged in the development of a lung pathology, with a greater involvement of CD4 T cells. Although CD4-depleted mice had impaired generation of neutralizing antibodies, they were fully protected against HMPV replication and clinical disease, indicating that the presence of the CD8 subset alone can be sufficiently protective . In lineIt is believed that a successful vaccine against respiratory viruses should induce memory CD8 T-cell responses. Upon re-encountering a pathogen, these memory T cells can quickly reactivate their effector functions and proliferate, contributing to protection . One of During natural infection, HMPV employs different strategies to circumvent the host’s interferon response to the pathogen, thus resulting in impaired innate and adaptive immune responses . HMPV moHMPV’s interference with the functions of dendritic cells (DCs), which aims to subvert the activation of both innate and adaptive immune responses, has been studied in detail in a mouse model ,57. In DThe main cause of enhanced disease manifestation during HMPV infection is overactivation of Th2 cells and immune-mediated pathologies in airways. As mentioned above, depletion of CD4 was found to significantly decrease the number of lung pathologies in mice . At the Currently, the mechanisms by which HMPV modulates host immunity are being intensively studied; however, there remain many unsolved problems. The main problem that needs to be solved in order for a vaccine to successfully be developed is that of correctly priming the host for proper immune responses after natural infection with HMPV . The information that we currently have suggests that CTLs, in collaboration with neutralizing antibodies, play a primary role in anti-HMPV protective immunity. The goal of a successful vaccine design is the proper stimulation of CD4 T cells after immunization. This stimulation is needed in order to increase the production of antibodies (with T follicular helpers) and to form a pool of CD8 memory T cells for rapid and effective secondary CTL responses to natural infection with HMPV. Therefore, studying the CD4 branch of HMPV immunity is the key requirement for the control of pathological processes and the development of prevention strategies.As was mentioned earlier, classical approaches to the development of HMPV vaccines were shown to be ineffective. Current strategies for rational HMPV vaccine design include the use of recombinant viral proteins (perhaps in a VLP formulation), recombinant live attenuated HMPV vaccines, and viral-vectored constructs.A non-replicating VLP-based vaccine, consisting of an M protein and a fusion-competent F protein, was developed by Cox et al. . C57BL/6ClinicalTrials.gov identifier: NCT01255410) [Several live attenuated vaccines against HMPV are currently under development ,20,68. N1255410) . The rHMAnother group of live attenuated HMPV vaccine candidates consists of genetically modified HMPV strains that lack one or two non-essential viral proteins known to negatively modulate innate and adaptive immune responses, such as G, SH, and M2-2 . Experiments have shown that it is possible to delete the G, SH, and M2-2 genes while retaining virus infectivity. Such engineered viruses were attenuated in non-human primates and protected animals against reinfection . SH deleMore recent approaches to the rational design of recombinant live attenuated HMPV vaccines include the removal of the N-linked carbohydrate at the 172nd amino acid of the F protein of an HMPV strain  and the Overall, the use of live attenuated vaccines against HMPV infection can be considered to be a promising strategy for vaccine design since these vaccines are administered intranasally and are capable of stimulating both humoral and cell-mediated immunity. Importantly, these vaccines will provide maximal HLA allele population coverage since the majority of immunogenic T-cell epitopes are present in the attenuated HMPV viruses. On the other hand, due to the complicated nature of the interactions between HMPV and the host’s immune system, these engineered viruses might include yet-to-be-described factors that contribute to modulating the host’s immunity. Therefore, any further clinical development of these candidates should include a broad assessment of immunogenicity and the duration of the protective response. Special attention should be paid to experiments involving specific models to estimate the respiratory pathology after challenge with HMPV.The use of other respiratory viruses as vector delivery systems seems to be the most promising strategy for the rational design of HMPV vaccines because these vectors can effectively deliver HMPV antigens to the right cell compartments, resulting in the proper presentation of antigens to the immune system and the development of balanced antibody and cell-mediated immune responses . Viral-vBesides heterologous respiratory viruses, other vector delivery platforms have shown promise for inducing protective immunity against HMPV. Virus-replicon particles of the Venezuelan equine encephalitis virus expressing HMPV’s F, but not G, protein were shown to be immunogenic and protective in mice, cotton rats, and African green monkeys after intranasal (mice and cotton rats) or intradermal (monkeys) immunization ,78. BactWhile the majority of viral-vectored HMPV vaccines that have been developed to date express one HMPV protein, other viral proteins can also contain important epitopes for the induction of balanced B- and T-cell immunity with memory potential. The selection of those epitopes, which are distributed among all HMPV proteins and conserved between different HMPV genotypes, may open up perspectives on the development of broadly protective HMPV vaccines using different vector delivery platforms. Importantly, the use of target epitopes, rather than whole genes, to design vaccines is crucial to vectors with a limited genome capacity to insert foreign antigens, such as attenuated influenza viruses ,81. LikeIt is well accepted that epitope-specific memory CD8 T cells are capable of providing protection against reinfection with respiratory viruses . HoweverSeveral CTL-targeted HMPV vaccines have been studied in animal models. The HBs-Ag vectored vaccine, which expresses a multiepitope cassette that includes an HMPV epitope, was shown to be immunogenic in mice and a CTL response after immunization was confirmed as IFNγ was detected after stimulation with a peptide . In a stTaken together, these studies yield important conclusions regarding the mechanisms of epitope-based vaccines; however, T-cell epitopes have been proven to be immunodominant for non-transgenic mice and thus cannot be used in human vaccines. Only epitopes that are restricted to human MHC alleles should be considered when designing vaccines for human use.Compared with RSV, the basis for HMPV epitope immunity is less studied: 773 RSV epitopes have been deposited at the IEDB, whereas only 138 HMPV epitopes have been described in 14 studies. Thirty-seven of these HMPV epitopes were confirmed in T-cell assays and are class I epitopes . One hunAll HMPV B-cell epitopes identified to date were found in the fusion glycoprotein, which is the main target for neutralizing antibodies in the HMPV virion. Attachment protein G has been shown to be more variable than attachment protein F and, in experimental studies, did not generate protective immunity ,28,97. ESix more linear B-cell epitopes within HMPV F protein were predicted using bioinformatics tools . Mice imhttp://www.allelefrequencies.net database.The development of a successful T-cell-based vaccine for humans has to be based on experimentally confirmed information regarding natural T-cell epitope processing, immunodominant capacities, the ability to induce memory T cells, and HLA allele coverage. In addition, the selected epitopes should be conserved among different HMPV genotypes to generate cross-protective immunity. In experimental studies, natural processing for 24 HMPV epitopes was confirmed. Sixteen were restricted by the MHC-I molecule of the HLA-A*02:01 allele, five were restricted by the HLA-B*07 allele, one was restricted by the HLA-B*11 allele, and two were found in PBMCs of non-typed donors . Some ofviprbrc.org) and mapped all experimentally established HMPV T-cell epitopes deposited at the IEDB to these alignments. Many of the described T-cell epitopes corresponded to highly conserved viral protein regions, indicating their broad reactivity (To narrow down the list of promising CD8 T-cell epitopes based on their cross-protective potential, we performed an alignment of full-genome sequences of 157 HMPV strains of all genotypes deposited at the Virus Pathogen Database (ViPR, activity , Table 2Despite the relatively short history of HMPV research, much progress has been made in the development and evaluation of anti-HMPV vaccines. Nevertheless, no vaccines have been licensed to date, although several candidates have yielded promising results in animal models. Overall, there are many potential targets for the rational design of epitope-based HMPV vaccines, preferably using vectored platforms. Viral vectors are a promising platform for the development of vaccines against other viruses due to effective immunogen delivery and stimulation of the appropriate components of the immune system specific for intracellular pathogens. Some of the experimentally evaluated neutralizing epitopes and CD8 T-cell epitopes have the potential to provide broad reactivity against various HMPV genotypes. However, more research needs to be done in order to find an optimal way to induce good-quality memory responses to HMPV. In particular, there is a lack of data on experimental human CD4 T-cell epitopes for HMPV, whereas animal studies suggest that proper induction of CD4 responses can help to generate memory immune responses ,103. On


Shape memory alloys (SMAs) have been widely used in civil engineering applications including active and passive control of structures, sensors and actuators and strengthening of reinforced concrete (RC) structures owing to unique features such as the shape memory effect and pseudo-elasticity. Iron-based shape memory alloys (Fe-SMAs) have become popular in recent years. Use of iron-based SMAs for strengthening RC structures has received attention in the recent decade due to the advantages it presents, that is, no ducts or anchor heads are required, friction losses do not occur and no space is needed for a hydraulic device to exert force. Accordingly, Fe-SMAs embedded in a shotcrete layer have been used for pre-stressing RC beams at Empa. The aim of this study is to present an approach to model and analyze the behavior of RC members strengthened and pre-stressed with Fe-SMA rebars embedded in a shotcrete layer. The lack of research on developing finite element models for studying the behavior of concrete structures strengthened by iron-based shape memory alloys is addressed. Three-dimensional finite element models were developed in the commercial finite element code ABAQUS, using the concrete damaged plasticity model to predict the studied beams’ load–displacement response. The results of the finite element analyses show a considerably good agreement with the experimental data in terms of the beams’ cracking load and ultimate load capacity. The effects of different strengthening parameters, including SMA rebar diameter, steel rebar diameter and pre-stressing force level on the beam behavior, were investigated based on the verified finite element models. The results were compared. The load-displacement response of an 18-m concrete girder strengthened and pre-stressed with iron-based SMA bars was examined by the developed finite element model as a case study. Shape memory alloys are a class of materials that have gained popularity in recent decades owing to unique features such as the shape memory effect (SME) and pseudo-elasticity. Numerous studies have addressed the use of these alloys in engineering applications. In civil engineering applications, Ni-Ti based alloys have been widely used in the confinement of columns, dampers, self-centering bridge components and pre-stressing of structural members . Iron-based shape memory alloys (Fe-SMAs) are an appropriate alternative for Ni-Ti based alloys in structural applications based on their lower cost, wider thermal hysteresis, good machinability, higher stiffness and the ability to develop high recovery stresses without thermomechanical training. It is noteworthy that the lower cost of Fe-SMAs stems from the lower cost of Fe and the less expensive production cost that can be conducted under atmospheric conditions ,7,8,9,10Shahverdi et al. experimentally investigated the application of a novel Fe-SMA developed at Empa for near-surface mounted (NSM) strengthening; their studies  showed tSMA-reinforced structures have been simulated through finite element models in few studies ,15,16. AAlthough many publications have numerically modeled Ni–Ti behavior in civil engineering structures using the inherent SME and super-elasticity of the Ni–Ti alloy, few researchers  have addThe main aim of this study is to detail the modeling of RC beams strengthened and pre-stressed with ribbed Fe-SMA bars embedded in a shotcrete layer. The Fe-SMA bars, with a diameter of 8 mm, were pre-strained and fixed to the bottom of the concrete beams. A shotcrete layer was applied to embed the bars. The recovery stress in the embedded Fe-SMA bars was activated by resistive heating . The resThree concrete beams with a cross-section of 160 mm × 250 mm and a span of 2 m were tested by Shahverdi et al.  Figure . Beam 9 To model the concrete behavior in ABAQUS, three methods are available: the smeared crack model, the brittle cracking model and the concrete damaged plasticity model. In the first method, as the name implies, cracks are not modeled individually on a macroscopic scale. The yield criteria are checked at each integration point and the corresponding stress and strain are calculated accordingly. However, defining damage parameters is not possible using this approach. The brittle cracking model is used when tensile cracking is the dominant behavior in members; compressive crushing is not considered. This model is capable of defining proper concrete behavior in the post-cracking stage but it simply assumes that concrete behaves elastically under compression. Concrete damaged plasticity is a combined model that accounts for both tensile cracking and compressive crushing of concrete. It is designed to predict the nonlinear behavior of concrete using the concepts of damage and plasticity, which are characterized by changes in elastic stiffness and irreversible deformations upon loading ,23. Numerous models have been proposed to define concrete behavior under uniaxial compression. The model suggested by , represeTo determine the direct tensile strength in this simulation, Equation (4) proposed in ACI-318  is used Equation (5) is used to convert flexural tensile strength to direct tensile strength  for shotTo define the tension stiffening in RC members, the contribution of concrete to the rigidity of RC members even after cracking should be considered . There ation (6) .(6)Gf=∫Equation (7) was proposed in CEB-FIP 90  to deterhotcrete . The behaviors of Fe-SMA bars with a composition of Fe–17Mn–5Si–10Cr–4Ni–1 (mass %), were modeled in this study. During pre-straining, the Fe-SMA bars were loaded to a tensile strain of 4% and unloaded to a stress-free state. The bars were anchored to the bottom face of the beam and the shape change was suppressed. The shape memory effect was activated in Fe-SMA bars by heating, resulting in the development of recovery stress due to the enforced deformation constraint. The generated recovery stress was used to pre-stress the concrete members. ABAQUS/Standard was used in this study as a finite element simulation tool to capture geometric and material nonlinearities. Only a quarter of the beam was modeled, due to symmetry in both the longitudinal and transverse directions, as shown in According to the experiments, no considerable slippage occurred between the Fe-SMA bars and the surrounding shotcrete or between the steel rebar and the concrete . Thus, tThe concrete–shotcrete interaction was a demanding step in this simulation, as the interfacial behavior had to transfer the pre-stressing force to the upper concrete section. To this end, cohesive behavior and rough contact options were used. Without defining a cohesive behavior, the pre-stressing force applied to shotcrete has no effect on the beam response because the concrete and shotcrete lose contact during loading. Rough frictional behavior was used, which assigns an infinite coefficient of friction to the concrete–shotcrete interface. As stated in the ABAQUS manual , combiniThe pre-stressing force was applied in the initial step before loading using the predefined field option in ABAQUS. The calculation for the upward deflection of the beam pre-stressed with two Fe-SMA bars activated with a recovery stress of 300 MPa is shown in Equation (8). The calculated deflection of 0.36 mm shows a good correlation with the FE result in b0/fc0, which was set to 1.16 according to the ABAQUS manual [Sensitivity analyses were conducted to determine the appropriate values for some concrete damaged plasticity model parameters. The first investigated parameter was the ratio of the initial biaxial compressive strength to the uniaxial compressive strength, fS manual  as therec and the plastic potential eccentricity e, were set as 2/3 and 0.1, respectively, as suggested by the ABAQUS manual [c is determined from the results of the full triaxial test of concrete. However, these data were not available and the default values were assigned [The shape of the loading surface kS manual . The kc assigned . The resThe concrete dilation angle ψ, which can be characterized as the internal friction angle of concrete, is an important parameter in the damaged plasticity model . As showViscosity or relaxation time is an optional parameter in the CDP model and helps to improve the convergence rate in the analysis . As statAs the CDP parameters were chosen based on the sensitivity analysis, the finite element models were fully developed. Pre-stressing concrete beams using Fe-SMA bars embedded in a shotcrete layer is state-of-the-art; the pros and cons have not been sufficiently studied. Thus, parametric studies are necessary to investigate the effect of variations in important parameters such as the diameter of the Fe-SMA bars on the response of beams, as shown in The displacement ductility index Based on the innovative nature of this strengthening technique, the feasibility of using ribbed Fe-SMA bars to strengthen the beams without activating the recovery stress is investigated. The results are compared to those for the pre-stressed beam and the beam reinforced by two steel rebars embedded in the shotcrete layer, as shown in ρ) of 0.34%, 0.75% and 1.3%, corresponding to rebar diameters of 8 mm, 12 mm and 16 mm, were analyzed. The analyses were conducted for different levels of pre-stressing, 100 MPa, 300 MPa and 400 MPa. A parametric study was conducted to investigate the effect of the recovery stress value on the beam flexural response. This study was conducted on the FE model of Beam 10, with different diameters assigned to the longitudinal steel reinforcement. Beams with reinforcement ratios  are 5, 3.5 and 2.2, respectively.2 cross-sectional area. A 1.25 m × 0.2 m upper concrete slab was also modeled. The cross-section schematic and longitudinal profile of the reference girder are illustrated in In previous sections, the feasibility of strengthening and pre-stressing reinforced concrete beams using ribbed Fe-SMA bars embedded in a shotcrete layer was studied by means of numerical analysis. The validated 3-D finite element models are used in this section in a case study on the load-bearing capacity of an 18m reinforced and pre-stressed concrete bridge girder strengthened by activated or non-activated Fe-SMA bars embedded in a shotcrete layer. The reference girder, used for comparison, is characterized by a double-tee section with a height of 1 m and is pre-stressed by three parabolic and two straight steel tendons, each with a 345 mmThe depth of the assumed bottom shotcrete layer was chosen as 40 mm. The shotcrete had the same material properties as the shotcrete applied to the beams in the previous sections. Key parameters defining the mechanical properties of concrete, longitudinal steel bars and tendons are presented in The simulated girders, strengthened by activated or non-activated Fe-SMA bars, were analyzed under static loading conditions. The results are compared to those for the non-strengthened girder (reference girder) in terms of the load vs. mid-span deflection curves. The results of the finite element analysis for girder G5 are illustrated in It can be concluded that application of activated Fe-SMA bars has a more considerable impact on cracking and yielding load of girders compared to the girders strengthened with non-activated bars. This advantage of activation must be evaluated considering the equipment and cost of activating bars for such massive structures. To recap, the case study in this paper aimed to investigate the feasibility of strengthening concrete bridge girders with Fe-based alloys. The finite element simulation results were promising; however, the applicability of the proposed strengthening method should be tested on several girder geometries with different reinforcement levels. Also, the proposed method’s applicability under different loading patterns could be an essential subject of further studies.c and the ratio of the biaxial compressive strength to the uniaxial compressive strength did not significantly affect the load–displacement response of the models; different concrete dilation angles yielded different results in the post-cracking stage. Adopting a proper viscosity parameter had a positive effect on the convergence and accuracy of the analysis results.In this study, numerical analyses of concrete beams strengthened and pre-stressed with Fe-based shape memory alloy bars were conducted. The constitutive models used for each material in the RC beam were explained along with the proper approach to implementing the pre-stressing effect on the beams in the 3-D finite element model. The results of the analyses compared to the experimental data indicate that the finite element models successfully predicted the load vs. mid-span displacement response of the beams. In addition, sensitivity analyses were performed to study the effect of variations in parameters in the concrete damaged plasticity model in ABAQUS. The results indicate that changes in eccentricity, k(ρ varies from 0.34–1.3%). Moreover, the variation in the recovery stress affects the cracking load more significantly than the yielding load and the ultimate load.Finite element analyses conducted for beams reinforced with different ratios of longitudinal rebars pre-stressed with three values of recovery stress activated in the Fe-SMA bars indicate that variation in the pre-stressing force produces a greater effect on a beam with a lower reinforcement ratio The flexural behavior of a similar beam strengthened by non-activated Fe-SMA bars was also investigated and compared to the pre-stressed and reference beams. The results indicate that activating the recovery stress increases the ultimate load by less than 5% compared to the non-prestressed beam; however, the cracking and yielding loads increase significantly. The feasibility of pre-stressing an 18-m concrete bridge girder by means of activated and non-activated Fe-SMA bars embedded in a shotcrete layer was studied. It was concluded that the load-bearing capacity of the bridge girders was significantly enhanced when using this method with Fe-SMA bars of a sufficient number and diameter.


OpenFlow makes a network highly flexible and fast-evolving by separating control and data planes. The control plane thus becomes responsive to changes in topology and load balancing requirements. OpenFlow also offers a new approach to handle security threats accurately and responsively. Therefore, it is used as an innovative firewall that acts as a first-hop security to protect networks against malicious users. However, the firewall provided by OpenFlow suffers from Internet protocol version 6 (IPv6) fragmentation, which can be used to bypass the OpenFlow firewall. The OpenFlow firewall cannot identify the message payload unless the switch implements IPv6 fragment reassembly. This study tests the IPv6 fragmented packets that can evade the OpenFlow firewall, and proposes a new mechanism to guard against attacks carried out by malicious users to exploit IPv6 fragmentation loophole in OpenFlow networks. The proposed mechanism is evaluated in a simulated environment by using six scenarios, and results exhibit that the proposed mechanism effectively fixes the loophole and successfully prevents the abuse of IPv6 fragmentation in OpenFlow networks. The use of software-defined networking (SDN) has rapidly increased in the last decade, and this increased usage has resulted in a new technique to control and manage a network from a centralized controller . SDN useThe firewall capabilities of OpenFlow switches can be used to filter packets on layer two, three and four to prevent and mitigate various types of attacks such as Denial of Service (DoS) and Man-in-the-middle (MITM). However, these firewall-based rules and filters can easily be circumvented in IPv6 based networks because many attacks can be fused with the IPv6 fragmented packet to bypass OpenFlow filtering. OpenFlow documentation  suggestsSeveral forwarding and protective devices that enforce a forwarding policy on a packet-by-packet basis are available in traditional networks. These devices suffer from evasion by fragmented packets that do not contain the entire IPv6 header chain. Therefore, RFC7112 recommends that intermediate systems  discard these fragmented packets . These pThe remaining sections are arranged as follows. Section 2 presents background information concerning IPv6 extension headers (EHs), IPv6 Fragmentation, abuse of IPv6 EHs, and how the OpenFlow protocol started its support for IPv6. Section 3 presents related works. Section 4 describes the conceptual model for the proposed mechanism. Section 5 discusses the implementation details and validates the results by using six scenarios. Section 6 discusses the results and implications of the proposed mechanism, and Section 7 presents the conclusion and future work.Extension Headers [Extension Headers create new attack opportunities [Extension Headers in greater detail in the first subsection. The second subsection presents the IPv6 fragmentation. The third subsection shows an example of how an attacker can exploit IPv6 fragmentation to circumvent a firewall. The last two subsections briefly discuss OpenFlow standard and its support IPv6 protocol.Several of the features of IPv6 are new and unique, and one of the most significant features and improvement in IPv6 is the  Headers . The addtunities . An adverequired per case. Within an IPv6 packet, these optional extension headers are placed between IPv6 header and transport layer protocol headers such as TCP, UDP, or ICMPv6. The extension headers are linked to the IPv6 header so that each successive header points to the next one. The type of subsequent headers can be determined by examining the next header field , which may have one of the values given in No Next Header) which indicates the end of the header chain. IPv6 packets may contain zero, one, or more extension headers, and each extension header includes a length field and a Next Header field. Every offset of extension header starts after the length of a preceding header is finished. IPv6 extension headers are optional fields that are added to support extra functionality IP fragmentation is a process that breaks packets into smaller pieces (fragments) so that the resulting pieces can pass through a link with a smaller maximum transmission unit (MTU). In IPv6 networks, fragmentation is carried out at the source node, and the receiver node reassembles the fragmented packets to its original form .Fragmentation requires the source node to discover a path with the smallest MTU supported by any sub-network on the path by using Path MTU Discovery (PMTUD). PMTUD is a mechanism to check the MTU size along the path between two nodes. When a source node sends a packet to the destination node, all routers on the path compare the packet size with their MTU. If packet size exceeds the MTU size, then the router will drop the packet and generate an ICMPv6 error message containing its MTU size and send it back to the source node. Upon receiving the smallest MTU size along the path, the source node will fragment the packets to match the smallest MTU for the current flow, as shown in Fragment Header. Unlike IPv4 protocol where fragmentation-fields were part of the IPv4 header, these fields have been moved to extension header in IPv6. All the fragmented packets must contain extension Fragment Header along with the header information of the original packet as shown in Fragment Header has all the information required to reassemble the packet at the destination. Fragment Header format [Fragment Header has the following fields:In IPv6 protocol, fragmentation is accomplished using an extension r format . The FraFragment Header.Next header (8-bits): Defines the type of next header that follows the extension Fragment Offset (13-bits): Identifies where the fragment must be placed during the reassembling of the fragmented packet.Resaved (2-bits): Reserved for future use.Id for the original packet.Identification (32-bits): Identify a unique The basic idea behind the abuse of IPv6 fragmentation is that the legitimate IPv6 packet is crafted in a manner that IPv6 header chain of the attacker packet is fragmented into several fragments and the first fragmented packet may not contain the necessary information about upper-layer protocols such as TCP and UDP. IPv6 header chain is required by security devices to determine that the incoming packets are compliant with their configured policies. Often, intermediate devices such as routers and non-stateful devices only inspect the first fragmented packet containing the header information , allowing attackers to obfuscate data in subsequent fragmented packets to circumvent the security devices. The Attacker breaks down a legitimate packet in many smaller fragmented packets to hide data. The obfuscated data carried out in these small fragmented packets look legitimate and can easily pass through security systems, however, once reassembled in its entirety at the receiving host, it can be used to execute a DoS attack on the target machine. According to Gont (2014) , two typType-1) of fragmented packets, an attacker can use Fragment Header along with Destination Options Header, Hop-By-Hop, or Routing Header to hide upper-layer protocol headers . Next Header field of the first fragment is set to value 6, i.e., TCP , whereas the upper-layer header  itself is shifted in the second fragment. The switch processing only second fragment cannot determine how many bytes should be skipped to get the offset of the upper-layer header because the Destination Options Header breaks the header chain by occupying space between Fragment Header and Upper-Layer header [In this type (r header .Type-2), the attacker hides both the last Next Header and the Upper-Layer header; hence, the switch cannot determine the type of Upper-Layer protocol. This concealment can be achieved by using Fragment Header and two Extension Headers . Next Header field of the first fragment is set to Destination Options Header, and the last Next Header field of the original packet is in the second fragment. Thus, the first fragment does not expose the last Next Header of the original packet  [Type-2 of the fragmented packet presents similar challenges as the first attack. Besides, the first fragment does not have the Upper-Layer header type.In the second type (rotocol) . The TypThe functional operations of any conventional switching device can be broadly categorized into two types, namely, Data-Plane and Control-Plane. The Data-Plane activities operate on received data packets and take necessary actions such as forwarding incoming packets to a specific outbound port. The Control-Plane deals with management activities, such as maintaining switching tables, and enforce packet forwarding policies .Controllers. Upon receiving a packet from any node, the OpenFlow switch will perform a table-lookup and based on flow entries it will take appropriate actions , otherwise and it will consult the centralized controller if it does not find a match-entry for the received packet [In any conventional switching device, both Data-Plane and Control-Plane activities take place on the same switching device. In OpenFlow networks, the Control-Plane is decoupled from Data-Plane. The OpenFlow switches only take care of Data-Plane, whereas the Control-Plane activities are handled by centralized d packet . The OpeIn the OpenFlow network, the OpenFlow controller manages the entire network. The controller is considered the brain of the OpenFlow network . The conThe basic workflow of the OpenFlow network is when the switch receives a packet, it checks the flow table to match the packet header against flow entry. If the packet header matches a flow entry, the switch will take action according to the instructions of the flow entry. Otherwise, the switch sends the packet header to the controller. The controller supplies the switch on how to handle the packet by using OpenFlow flow entries. Subsequently, the Switch forwards the packet based on the controller instruction and saves this instruction to forward the other similar packets. The following section explains match field that used to match exceptional conditions in IPv6 Extension Headers .OpenFlow has undergone many revisions, and additional changes are likely . OpenFloIn traditional networks, there are many protection mechanisms that devices that enforce a forwarding policy on a packet-by-packet basis. These protection mechanisms can be evaded by using IPv6 fragmentation. The following are the most common security mechanisms that prevent the abuse of IPv6 Fragmentation.undetermined-transport” keyword. When this keyword is used with a deny statement, the ACL drops a packet if it cannot determine the upper-layer protocol in the fragmented packet [Access control list (ACL), a stateless firewall, is the most popular mitigation technique against IPv6 attacks mentioned in . ACL defd packet .Router advertisement (RA) guard is another protection firmware designed to protect networks against RA based Attack. The RA based attack is one of the most common attacks in the IPv6 network, which is rogue RA message crafted by the attacker and send to IPv6 nodes in the network to inject rogue information in the IPv6 host which could cause either DoS or MITM attacks. An RA-Guard mechanism is used to validate incoming RA messages and determine whether they match the conditions defined in the policy. The RA-Guard mechanism was unable to handle fragmented packets. The newer versions of RA-Guard opted to discard the first fragment that does not include the entire header chain because the RA-Guard cannot determine the content of the first fragment .Dynamic host configuration protocol (DHCP) v6-Shield is another firmware designed to protect networks against a rogue DHCP server. An adversary could install a rogue DHCPv6 server on an IPv6 network to inject malicious information to carry out attacks such as DoS and MITM. A DHCPv6-Shield mechanism is used to validate incoming DHCPv6 server messages on a specific port. This mechanism also can be evaded by the IPv6 fragmentation packet. Therefore, it is designed to discard the first fragment that does not contain the entire header chain .The main limitations of the aforementioned mechanisms are firstly because it is very difficult to manage OpenFlow switches in medium to large-scale/enterprise networks ; SecondlExtension Headers enables attackers to deceive switches form adequately applying OpenFlow policies to filter and block IPv6 fragmented packets discussed in section Abuse of IPv6 Fragmentation. Each type of fragmented packets has attributes for first and non-first fragments. The proposed mechanism intends to match anomalous conditions in the first fragment of an IPv6 fragmented packet. The attack by exploiting IPv6 fragmentation can be easily identified by analyzing the first fragment because the suspicious presence of incomplete and broken IPv6 header chain indicates an anomalous behavior. On the other hand, IPv6 fragmented attack carried out using non-first fragmented packets is difficult if not impossible to detect since non-first fragmented packets contain only Fragmented Header extension chain which does not reveal the information about Upper-Layer protocol header. Fortunately, filtering and blocking of the first fragmented packet are sufficient to detect and prevent the attack because without having the first-fragmented packet, the receiving host cannot reassemble the fragmented packet, and hence the packets are discarded.The abuse of IPv6 Type-1 and Type-2 anomalous fragmented packets. These flags are OFPIEH_UNDLH (Undetermined Last Header), and OFPIEH_UNDLNH (Undetermined Last Next Header) to match Type-1 and Type-2 anomalous conditions, respectively. Two new flags have been added and used in the proposed mechanism to filter out These flags will be set to value 1 whenever IPv6 fragmented packets match the anomalous conditions. For simplicity, these two flags have been added in the existing standard OpenFlow protocol without introducing new matching fields. The proposed mechanism uses the OXM_OF_IPV6_EXTHDR field, and the two flags are appended to the end of the flags of the OXM_OF_IPV6_EXTHDR field, as illustrated in 2 this equivalent to (1024)10. These newly added flags offer flexibility to match different types of packets. For example, the OFPIEH_UNDLH flag can be used with OpenFlow’s OXM_OF_IP_PROTO match field (upper-layer protocol) that helps to pass through or drop the first fragment that has the type of upper-layer protocol and the hidden upper-layer header. The added flags give OpenFlow programmers more flexibility to forward or drop the desired packet at will.The two new flags, OFPIEH_UNDH and OFPFIEH_UNDLH, are appended next to the OFIEH_UNSEQ, and they obtain bit numbers 9 and 10, respectively. To match the first fragment, as shown in https://github.com/al-ani/fragmenation_attack.The proposed mechanism is implemented to apply the modifications to the OpenFlow switch and controller. The Ryu Controller  running Host-A and Host-B), one OpenFlow switch and one controller server, as shown in Host-B.The network topology used to test the functionality and effectiveness of the proposed mechanism is comprised of two host machines , which enforces the switch to drop such packets. Following are findings observed at the switch and the host Host-A:The switch in Scenario-II was unable to block the attack carried out by using IPv6 fragmented packets; therefore, the Scenario-III tests the “OFPIEH_ UNDLH” flag to drop the fragmented packet crafted in Scenario-II. To attain this, the switch is preconfigured with the Host-B that, Host-B does not receive the first fragmented packet, and only receives the second fragmented packet, as shown in Host-B, without having the first fragment, cannot reassemble the fragmented packet and discards it.It can be observed in Wireshark dump captured at Host-A was received at the switch, and it was dropped based on the action enforced by Flow-Entry-2.Based on the results as mentioned above, it can be claimed that the flag OFPIEH_UNDLH was effectively used to identify and drop the fragmented packet.Type-1 fragmented packets; however, the flow table entries Flow-Entry-1 and Flow-Entry-2 are not sufficient to prevent Type-2 fragmented packets. To prove this, the scenario-IV aims to evade an OpenFlow switch preconfigured with F1 and F2 by using the ICMPv6 fragmented echo-request packet that has neither the last Next Header nor the last header (similar to Type-2 of fragmented packets explained in section Abuse of IPv6 Fragmentation). The attack is carried out from Host-A by sending a fragmented ICMPv6 echo request message, similar to that shown in Host-B, as shown in Flow-entry-2 could not match this fragmented packet because it matches the fragmented packet that has the last Next Header set to ICMPv6. Therefore, the fragmented packet evades the OpenFlow switch that has Flow-Entry-1 and Flow-Entry-2.The flag OFPIEH_ UNDLH used in Scenario-III successfully patched the loophole and blocked Flow-Entry-3 to fix the loophole caused by Type-2 IPv6 fragmented packets. Once again, the Host-A sends a crafted packet similar to that shown in Host-B. As it can be seen in Host-A, and it dropped the packet by matching Flow-Entry-3. The Wireshark also shows that Host-B received only the second fragmented packet, as illustrated in Type-2 loophole and enabled the switch to drop the anomalous packets.In this scenario, the flag OFPIEH_ UNDLNH is used to fix the problem highlighted in the Scenario-IV. The switch is preconfigured with Type-1 of a fragmented packet). The scenario started when Host-A sent the fragmented TCP packet to Host-B. Wireshark showed that Host-B received the fragmented packet, as illustrated in All the previous scenarios attempted to block the ICMPv6 echo request message. However, this scenario aims to test the flows that can allow the TCP fragment hidden in the last header and with the last Next Header set to 6 (TCP) to pass  from passing through. The Scenario-III demonstrated that the switch was preconfigured with F1 and F2 dropped the first fragment, and successfully prevented it from passing through. The flag (OFPIEH_UNDH) served its purpose and helped out the switch to drop the intended packet. It should be noted here that, non-first fragmented packets evaded the switch. The non-first fragmented packets were dropped on Host-B because Host-B cannot reassemble fragmented packets without the first fragment. Scenario-IV demonstrated that the switch having F1 and F2 could only prevent Type-1 packets from passing through and it cannot block Type-2 packets. To prevent Type-2 packets from passing through, this time, in Scenario-V, the switch was preconfigured with F1, F2, and F3 flow entries, and as it can be seen in Type-2 packet was successfully dropped on the switch. The final scenario  demonstrated that network developers enjoy the freedom and the flexibility to drop selected packets matching with flow entries preconfigured on the switch. The Scenario-VI demonstrated that a fragmented TCP packet successfully passed through the switch, because flow entries F1, F2, and F3 only matched with ICMPv6 packets.To the best of our knowledge, there exists no specialized technique that prevents IPv6 fragmented packets from invading the OpenFlow networks. IPv6 fragmented packets can be used to launch attacks in the network. This study exposed that an attacker could use IPv6 fragmentation to evade the OpenFlow first-hop security and static OpenFlow firewall. Abuse of IPv6 fragmentation can be used in combination with various attacks, such as SYN and UDP flood attacks, to evade the OpenFlow forwarding policies. In typical networks, network devices have specialized firmware designed to deal with RA-based and DHCPv6 server-based attacks. However, in OpenFlow networks, protection against these attacks is left to the OpenFlow controller, which can be evaded by abusing IPv6 fragmentation  that canS1 Data(RAR)Click here for additional data file.


Background: A major disadvantage of current spacers for two-stage revision total knee arthroplasty (R-TKA) is the risk of (sub-) luxation during mobilization in the prosthesis-free interval, limiting their clinical success with detrimental consequences for the patient. The present study introduces a novel inverse spacer, which prevents major complications, such as spacer (sub-) luxations and/or fractures of spacer or bone. Methods: The hand-made inverse spacer consisted of convex tibial and concave femoral components of polymethylmethacrylate bone cement and was intra-operatively molded under maximum longitudinal tension in 5° flexion and 5° valgus position. Both components were equipped with a stem for rotational stability. This spacer was implanted during an R-TKA in 110 knees with diagnosed or suspected periprosthetic infection. Postoperative therapy included a straight leg brace and physiotherapist-guided, crutch-supported mobilization with full sole contact. X-rays were taken before and after prosthesis removal and re-implantation. Results: None of the patients experienced (sub-) luxations/fractures of the spacer, periprosthetic fractures, or soft tissue compromise requiring reoperation. All patients were successfully re-implanted after a prosthesis-free interval of 8 weeks, except for three patients requiring an early exchange of the spacer due to persisting infection. In these cases, the prosthetic-free interval was prolonged for one week. Conclusion: The inverse spacer in conjunction with our routine procedure is a safe and cost-effective alternative to other articulating or static spacers, and allows crutch-supported sole contact mobilization without major post-operative complications. Maximum longitudinal intra-operative tension in 5° flexion and 5° valgus position appears crucial for the success of surgery. Predominant causes for revision total knee arthroplasty (R-TKA) are periprosthetic joint infections PJI; 22.6%), followed by instability (20.0%), aseptic loosening 14.9%), and retropatellar arthrosis  bone cement during R-TKA. They aim at achieving optimal adaptation to existing bone surface and joint space in patients with ligamentous instability and large defects after explantation. Due to their design, static spacers resemble an arthrodesis with limited mobility of the knee joint and the potential for increased bone loss. This may either lead to joint stiffness and subsequent problems upon re-implantation ,10,11 orArticulating spacers, on the other hand, were primarily developed to improve the mobility in the prosthesis-free interval ,13,14 anTherefore, the aim of this study was to develop and evaluate the results of such a novel spacer without the risk of (sub-) luxation, paying particular attention to: (1) a fine-tuned shape of the spacer ; (2) joint positioning during the final molding and hardening of the spacer ; (3) defined mechanical conditions during the post-operative mobilization of the patient .The Caucasian patient cohort in this retrospective study  consisted of all 101 chronic PJI patients admitted to the Department of Orthopedics, Jena University Hospital, Waldkliniken Eisenberg GmbH during a period of 6 consecutive years , range 43 to 82 years; 55 females, 67.9 ± 1.2 years, range 52 to 89 years) without any exclusion criteria. The diagnosis of the PJI was based on internationally established procedures including a combination of laboratory, histopathology, microbiology, and imaging studies  tight embracing of the convex tibial part by the concave femoral part recalls pure hinge joints such as the elbow joint, in which approximately 50% of the convex trochlea is covered by the concave ulna. This shape sufficiently prevents anterior to posterior (ap) translation of the spacer; (ii) the usually smaller bone defect on the tibia, in conjunction with its anatomic shape and its levelled, broad weight-bearing surface, suggested a convex shape on the tibia. In contrast, the larger, anatomically concave femur defect with the central notch rather suggested a concave shape of the femoral component; (iii) after initial molding and polymerization of the tibial component, molding of the concave femoral component under maximal tension turned out straightforward and efficient, allowing to adapt the two spacer components with minimized play until the last minute of the polymerization. In addition, both parts of the spacer were designed with a stem component to ensure optimal anchoring in the medullary canal for rotational stability ,14.The novel inverse spacer was intraoperatively molded with PMMA bone cement containing antibiotics adapted to the antibiogram of the respective microorganism according to the supplier’s instructions . For this purpose, first the tibial spacer component was pre-formed in the surgeon’s hand, implanted, and formed in a convex manner with a spatulum. Thereafter, the femoral spacer component was pre-formed, implanted, and intra-articularly molded with a spatulum to adapt its concavity as closely and congruently as possible to the convex tibial component without specific adaptation to the retropatellar surface (for details of the joint position see below). Comparable amounts of PMMA bone cement were utilized for the two different spacer components.The cement was molded during the bonding phase to avoid complete bony integration, but reach sufficient bony anchorage. This allowed a quicker removal without causing more defects before the re-implantation. To maximize the surface for the release of antibiotics, the cement was mixed without vacuum.® ½ polyhexanide wound solutions for 15 min , rinsing with 0.9% saline solution , and implantation of the inverse spacer as described above. During implantation of the femoral component, the leg was stringently held by an assistant in 5° flexion and 5° valgus position under maximum longitudinal tension, a step considered crucial for successful spacer molding and implantation. After spacer implantation and full polymerization, an intra-articular drain was inserted, followed by conventional closure of the situs and sterile wound dressing. All patients received intravenous antibiotic therapy according to the concurrent international guidelines for 10 days with subsequent oral antibiotic coverage for a total of four weeks, followed by an antibiotic holiday until re-implantation.After removal of the infected prosthesis and tissue sampling, a wide surgical debridement and complete synovectomy was performed. This was followed by irrigation of the joint with sterile, iso-osmotic LAVANIDAnterior to posterior and lateral X-rays of the knee were taken before and after prosthesis removal and re-implantation.Postoperative crutch- or walker-assisted mobilization with obligatory application of a straight 0° leg brace C was limThe Kaplan–Maier failure rate of the spacer was calculated as previously published .n = 101; total of 110 R-TKAs) were treated with the inverse antibiotic- loaded spacer. In 3 patients, an early spacer exchange was necessary within the first week after the primary spacer implantation because of persistent or increased infection parameters and continuing wound secretion. The X-ray after spacer implantation indicated a correct positioning of the spacer without fractures of spacer or bone.All patients with a diagnosed or suspected infection after TKA during a period of six consecutive years  was still reached in all patients before re-implantation.The advantages of the current two-component spacer with restricted post-operative ROM in comparison with a conventional static spacer can thus be summarized as follows: (i) by reducing the post-operative forces/friction occurring at the cement-spacer interface, the current spacer design may help to avoid gross bone loss and bone fractures, as exemplified in representative Of note, Lanting et al. pointed out that sagittal (anterior-posterior), but not coronal  subluxation, of the knee had a significant influence on early to mid-term functional knee scores following a two-stage R-TKA for infection . This isStandardized fabrication of spacers for R-TKA may be of advantage to favor reproducible spacer shapes and features and in order to save operating time and personnel effort. Indeed, there are several studies reporting on pre-fabricated spacer components or molds for standardized production of spacer parts with PMMA bone cement ,17,18. HIn the present study, maximum longitudinal intra-operative tension along the physiological axis in 5° flexion and 5° valgus position proved crucial for the success of surgery. This was necessary to position the spacer with minimized play in the artificial “joint” and thus to avoid initial wobbling possibly leading to loosening of the spacer. This concept is in good agreement with the statements of other authors, who suggested to achieve the correct, quasi-physiological tension in the knee joint by using appropriately sized components and/or cement mantle thicknesses, thus ensuring that the implant is neither fitted too loosely nor too tightly ,11,15,25The application of a straight leg brace was also considered crucial for the clinical success, since it prevented medio-lateral knee movement and strongly limited knee flexion. In the previous literature numerous different possibilities for the regulation of joint ROM were applied, ranging from post-operative mobilization without any brace for dynamic spacers  to complIn line with these considerations, crutch-supported sole contact mobilization was considered appropriate in the present clinical design of the R-TKA. As in the case of the brace application, several different approaches for weight bearing have been reported previously, ranging from sole contact (present study), to partial or “gentle” weight bearing ,15,20, aThe present study has the following limitations: (i) it contains a limited number of R-TKAs , however, it is one of the few studies with a case number clearly exceeding 100 (e.g., ,7,8,9,24The study confirms our main hypothesis that the novel, correctly implanted inverse spacer, in conjunction with our routine clinical procedure, seems to be a safe and cost-effective alternative to other articulating or static spacers for the therapy of PJI after primary TKA, allowing crutch-supported sole contact mobilization without major post-operative complications. Whether the spacer is also suitable for partial or full weight bearing, as possibly and unintentionally performed in the present study, will have to be analyzed in future studies.


COVID-19 infection caused by a novel coronavirus SARS-coV-2 has made the diagnosis and the treatment of inflammatory diseases incredibly challenging. On the one hand, because of its pro-inflammatory state, that may aggravate or trigger flares in autoimmune diseases such as systemic lupus erythematosus (SLE). On the other hand, the risk of an immunosuppressive therapy during the active phase SARS-coV-2 infection that may lead to catastrophic outcomes. We report a case of a 24-year-old female newly diagnosed with SLE during COVID-19 pandemic who developed COVID-19 infection during her induction treatment for lupus nephritis.A 24-year-old Nepali female, with no past medical history of note, presented to her regional hospital with a history of flu-like symptoms few days ago, peripheral oedema, acute kidney injury with proteinuria and hypertension. Further investigations showed a high titre of double-stranded DNA antibodies, anti-cardiolipin IgM and B2 microglobulin positive and low C3. She also developed a haemolytic anaemia and thrombocytopenia during her admission. She received pulsed steroid therapy and was started on mycophenolate mofetil (MMF) for a probable lupus nephritis awaiting the results of biopsy, which showed later a lupus nephritis Class IV-G with active lesions. She then developed symptoms of COVID-19 infection and had a positive PCR leading to an interruption of her induction therapy. She was recruited to the RECOVERY trial on the lopinavir-ritonavir arm and made a good recovery.It is well known that viruses can trigger or aggravate auto-immune response in patients predisposed genetically. However, the role of SARS-coV-2 is not elucidated yet. The EULAR COVID-19 registry showed that rheumatoid arthritis and SLE were the most prevalent rheumatic diseases, and there was an increased risk in those who are on moderate to high dose corticosteroids. In patients with SLE and COVID-19 infection, it is agreed by all the national and international rheumatology societies to interrupt their immunosuppressive therapy until the symptoms resolve, especially those with renal involvement or an active disease. Which is the case in our patient. Luckily, she resumed her MMF a month later after a negative PCR and her renal function has continued to improve.Lupus nephritis is a major risk factor for overall morbidity and mortality in SLE. It requires an early immunosuppressive treatment to induce remission.Randomized clinical trials showed that MMF is at least equally effective as cyclophosphamide in inducing remission and that it has been associated with a reduced risk of infection and amenorrhea. It seems to be a suitable alternative in women of childbearing age. In patients with concomitant COVID-19 disease, immunosuppressive therapy should be paused until the symptoms improve.


Monitoring the functional status of poststroke patients after they transition home is significant for rehabilitation. Mobile health  technologies may provide an opportunity to reach and follow patients post discharge. However, the feasibility and validity of functional assessments administered by mHealth technologies are unknown.This study aimed to evaluate the feasibility, validity, and reliability of functional assessments administered through the videoconference function of a mobile phone–based app compared with administration through the telephone function in poststroke patients after rehabilitation hospitalization.A randomized controlled trial was conducted in a rehabilitation hospital in Southeast China. Participants were randomly assigned to either a videoconference follow-up (n=60) or a telephone follow-up (n=60) group. We measured the functional status of participants in each group at 2-week and 3-month follow-up periods. Half the participants in each group were followed by face-to-face home visit assessments as the gold standard. Validity was assessed by comparing any score differences between videoconference follow-up and home visit assessments, as well as telephone follow-up and home visit assessments. Reliability was assessed by computing agreements between videoconference follow-up and home visit assessments, as well as telephone follow-up and home visit assessments. Feasibility was evaluated by the levels of completion, satisfaction, comfort, and confidence in the 2 groups.X21=1.6, P=.21 for 2-week follow-up; X21=1.9, P=.17 for 3-month follow-up). Patients in the videoconference follow-up group perceived higher confidence than those in the telephone follow-up group at both 2-week and 3-month follow-up periods . The videoconference follow-up group demonstrated higher satisfaction than the telephone follow-up group at 3-month follow-up .Scores obtained from the videoconference follow-up were similar to those of the home visit assessment. However, most scores collected from telephone administration were higher than those of the home visit assessment. The agreement between videoconference follow-up and home visit assessments was higher than that between telephone follow-up and home visit assessments at all follow-up periods. In the telephone follow-up group, completion rates were 95% and 82% at 2-week and 3-month follow-up points, respectively. In the videoconference follow-up group, completion rates were 95% and 80% at 2-week and 3-month follow-up points, respectively. There were no differences in the completion rates between the 2 groups at all follow-up periods (The videoconference follow-up assessment of functional status demonstrates higher validity and reliability, as well as higher confidence and satisfaction perceived by patients, than the telephone assessment. The videoconference assessment provides an efficient means of assessing functional outcomes of patients after hospital discharge. This method provides a novel solution for clinical trials requiring longitudinal assessments.chictr.org.cn: ChiCTR1900027626; http://www.chictr.org.cn/edit.aspx?pid=44831&htm=4. Stroke is one of the leading causes of death and disability worldwide . As in oPoststroke home-based therapies seem to be a viable option for the delivery of stroke care. Follow-up assessments and interventions not only provide a means of monitoring the functional status of patients after transitioning to home and community , but alsTelephone administration is a common alternative. This method allows participants to be recruited from diverse geographical areas, is typically less expensive than the face-to-face home assessment, and has a quick turnaround time . Prior sWith advances in computing power and mobile connectivity, many mobile health  technologies, such as mobile devices, sensors, apps, and social media, are becoming available to obtain data pertinent to wellness and disease diagnosis, prevention, and management . WeChat Although the utility of the WeChat app has been demonstrated in other populations, little is known about whether the WeChat app could be feasible to assess the postdischarge functional status of patients following a stroke, because most poststroke patients experience cognitive and communication difficulties that may make it difficult to operate the app and understand its instructions. To address this question, we conducted a pilot randomized controlled trial in a group of discharged stroke patients by randomly assigning them into 2 different modes of administration during 2-week and 3-month follow-up periods: WeChat video conference or WeChat telephone administration. This study had 2 specific aims. The first aim was to compare the validity and reliability of functional assessment between these 2 modes of administration in stroke patients. We hypothesized that videoconference administration would demonstrate higher validity and reliability than telephone administration, because examiners using videoconference administration can observe how the respondent performs specific tasks to provide appropriate ratings, whereas examiners in the telephone administration group demand more subjective appraisals of task performance based on the respondent’s verbal descriptions. Our second aim was to examine the feasibility of the functional assessment administered via the videoconference function compared with the telephone call function in stroke patients after rehabilitation hospitalization. We hypothesized that both modes of administration would demonstrate high levels of completion, comfort, satisfaction, and confidence.This study was a parallel, 2-group, and pragmatic randomized controlled trial of an mHealth app of functional outcome data collection after inpatient stroke rehabilitation. The trial was registered with the Chinese Clinical Trial Registry: ChiCTR1900027626. A total of 120 eligible stroke patients from the affiliated rehabilitation hospital of Fujian University of Traditional Chinese Medicine were recruited for this study. Participants were approached by a research assistant, who provided the study information. After participants provided informed consent and were screened for eligibility, participants were randomized into 1 of the 2 WeChat app administration groups: videoconference follow-up or telephone follow-up, with a ratio of 1:1. Eligible participants were randomized using a random number table generated by a study coordinator who was not involved in the recruitment and assessment of participants for the study.This trial was implemented in compliance with the declaration of Helsinki and approved by the Ethics Board of the affiliated rehabilitation hospital of Fujian University of Traditional Chinese Medicine (number: 2016KY-032-01). All participants provided informed, written consent before participation. Participants received an honorarium to acknowledge their research contribution.Patients were eligible to participate in the study if they met the following criteria: (1) aged at least 18 years, (2) diagnosis of first stroke, (3) normal speech function according to the Mandarin Language Screening Test with cutoff scores of >13 for those with primary school education or >14 for those with junior high school or higher education, (4) normal cognitive function according to the Montreal Cognitive Assessment with a cutoff score of >26, and (5) home discharge. Participants were excluded if they (1) did not own a mobile phone, (2) were unwilling to install and use the WeChat software on their mobile phone, (3) had emotional dysfunction according to the Beck Depression Inventory with a cutoff score of >13, or (4) had other medical illnesses limiting study participation. As we included only participants who served as their own informant rather than including participants on a nonselected basis, it is likely that individuals who were too cognitively impaired or were unable to understand the study materials were excluded.Participants were recruited from the inpatient rehabilitation hospital. Recruitment was initiated while the stroke patient was still in the hospital. The research assistant screened the medical records of all patients undergoing inpatient rehabilitation for a stroke. Once potential participants were identified, the research assistant approached the individual and provided information about the study. Participants provided informed consent once they agreed to participate. The research assistant reviewed the inclusion and exclusion criteria and completed the screening tests to confirm eligibility. Participants were then enrolled, and randomization occurred only after recruitment by a study coordinator.All research assistants received training in assessing the eligibility of potential participants, obtaining informed consent from participants, the study protocol, and obtaining outcome measures for both groups. They also received training in how to coach and assist participants using the WeChat app, including the videoconference and telephone call functions. After randomization, all participants received the baseline assessment at the week of discharge, followed by the completion of 2 mHealth app follow-up sessions (either videoconference or telephone), and half of the participants from each group received 2 home visits. The first follow-up session occurred 2 weeks after home discharge. Within 1 week of the first follow-up session, half of the study participants were selected to conduct the first home visit based on stratified sampling in each group. The stratified sampling criteria were grounded on participants’ functional abilities. As home visits are costly, this study was limited by randomly selecting half of the study participants for the home visit assessment. The second follow-up session occurred 3 months after home discharge. Within 1 week of the second follow-up session, we completed the second home visit in this subgroup of participants. The time interval between videoconference or telephone follow-up and home visit of 1 week was considered long enough to ensure that the previous responses were forgotten and short enough to ensure that the patient’s clinical condition would not substantially change. All assessments were conducted by our trained research assistants with training in physical therapy, occupational therapy, or rehabilitation medicine. To reduce assessor bias in the trial, research assistants who completed the videoconference or telephone follow-up sessions also conducted home visits with patients in the same group. We treated the face-to-face, home visit assessment as the gold standard in this study.Participants in the videoconference follow-up group received training on the usage of the videoconference function of the WeChat app before discharge. During the follow-up sessions, research assistants asked participants to complete individual functional tasks and rate their actual performance through the videoconference, with the exception of bladder and bowel management tasks, which were assessed by the participant’s verbal descriptions. Participants also described difficulties pertaining to their individual task performance. During the home visit, research assistants completed the face-to-face observations by rating participants as they completed the same functional tasks. We used the same scoring criteria to evaluate the performance of our study participants in both videoconference and face-to-face, home visit assessments. Participants in the telephone follow-up group received training on the usage of the telephone function of the WeChat app before discharge. During the follow-up sessions, research assistants made telephone calls, asked participants how they performed in each functional item, and appraised their performance based on the participant’s verbal descriptions. During the home visit, research assistants completed the same protocol as in the videoconference follow-up group. We used the same scoring criteria to evaluate the performance of our study participants in both telephone and home visit assessments.As recommended in a systematic review of optimal outcome measures for stroke therapy trials , the priWe also defined 2 outcome variables to examine the feasibility of using an mHealth app to measure functional status of stroke participants in this study. The first variable was the completion of the MBI among our study participants in both groups at both follow-up periods. The second variable was the acceptability among our study participants  of using the videoconference or telephone functions to complete the functional assessment at follow-up periods. We developed 3 questions: (1) “Are you satisfied with this follow-up assessment?” (2) “Are you comfortable with this follow-up assessment?” and (3) “Are you confident using this follow-up assessment?” All items were rated on a 4-point scale ranging from “very satisfied/comfortable/confident” to “unsatisfied/uncomfortable/unconfident.”t tests or Mann-Whitney tests for continuous variables, and Pearson chi-square tests for categorical variables. We applied Wilcoxon signed-rank tests to compare MBI score differences between videoconference and telephone assessments, as well as between videoconference/telephone and home visit assessments for the validity evaluation. We set the P value to .05 for statistical significance. We used intraclass correlation coefficients (ICCs) to evaluate the agreement of all item scores between these assessments for the reliability evaluation. According to Landis and Koch [Data were analyzed using the Statistical Package for Social Sciences, version 20 . Baseline characteristics between groups were compared using and Koch , the ICCWe adopted stratified sampling in each group to select subgroups of participants for home visit assessments. We used the discharge MBI scores of 52 participants in the videoconference follow-up group and 57 participants in the telephone follow-up group to classify their functional independence levels into 4 videoconference follow-up subgroups and 4 telephone follow-up subgroups, respectively. The number of participants in the videoconference follow-up and telephone follow-up subgroups is shown in Χ21=1.6; P=.21) at 2 weeks. At 3-month follow-up, 3 out of 52 (6%) participants in the videoconference follow-up group dropped out, and 9 out of 57 (16%) participants in the telephone follow-up group dropped out. There was no significant difference in the completion rates between the 2 groups  at 3 months.As shown in Χ23=2.5; P=.28) at 2 weeks. At 3-month follow-up, participants in the videoconference follow-up group reported higher satisfaction than those in the telephone follow-up group . Additionally, most participants were either very comfortable  or comfortable  with the videoconference function, and most participants were either very comfortable  or comfortable  with the telephone call function. There were no differences in comfort levels between the 2 groups at 2 weeks  or 3 months . Regarding participant confidence using the videoconference or telephone function for collecting functional data, participants in the videoconference follow-up group rated higher confidence than those in the telephone follow-up group at 2 weeks  and 3 months .This is one of the first studies to compare the validity and reliability of the videoconference and telephone functions of an mHealth app for collecting functional status data in stroke patients after rehabilitation hospitalization and to examine the feasibility and acceptability of using these modes of administration for data collection. We examined these questions prospectively in a cohort of patients who were discharged from inpatient stroke rehabilitation by comparing videoconference and telephone follow-up assessments, as well as comparing these 2 modes of administration to the home visit assessment as the gold standard.We found that most MBI scores obtained by videoconference administration were slightly lower than those obtained by telephone administration, although these score differences did not achieve statistical significance at either 2-week or 3-month periods. Our findings further revealed that videoconference, but not telephone, administration was as valid and reliable as face-to-face, home visit assessment at both 2-week and 3-month follow-up periods. Home visit assessment is conventionally regarded as one of the best methods for collecting posthospitalization outcome measurement data . Home viOur findings revealed that almost all MBI scores obtained by telephone administration were higher than those obtained via home visit. This overestimation of functional scores is particularly obvious at 2-week follow-up; telephone assessment of functional status using the MBI was less reliable compared with the home visit at 2-week follow-up, but reliability did improve at 3-month follow-up. Previous studies have attained strong agreement between telephone and face-to-face assessments ,44. PsycIt is noteworthy that our findings indicate that completion rates of both videoconference and telephone assessments were greater than 80% at all follow-up periods. These completion rates are within the acceptable range in clinical studies . MoreoveOur study has a number of strengths. Prior research testing the feasibility and psychometrics of mHealth assessments has primarily adopted the observational design, but ours is one of the first few studies to employ the randomized controlled design to compare these characteristics for 2 different mHealth methods to collect outcome data after discharge from inpatient stroke rehabilitation. Additionally, this study conducted 2 follow-up sessions for both assessment methods to better understand any issues related to long-term compliance. Yet, our study has several limitations. First, patients were recruited from one rehabilitation hospital in a coastal province in eastern China; therefore, results may not generalize to persons living in other regions. Second, this study only included participants who owned a mobile phone and served as their own informant to complete the assessment; patients without a mobile phone and those with severe cognitive or communication impairments may have been excluded from this study. Third, the MBI was the only outcome assessment used in the study. Future research should explore mHealth assessments for measuring other health outcomes in poststroke individuals after discharge from the hospital. Another limitation includes measuring acceptability through 3 self-constructed items , which are limited in their measurement of this construct and do not provide actionable data with which to inform future research. Even though these self-constructed items allow for efficient quantification of acceptability, future research should add a qualitative or mixed method approach to provide additional interpretation and meaning to the quantitative results . FurtherThis study found satisfactory feasibility and validity of an app-based videoconference method for collecting functional data after inpatient stroke rehabilitation. High completion and acceptability, as well as adequate validity and reliability of the videoconference follow-up method, may support its clinical application in poststroke home rehabilitation programs and long-term health monitoring after hospitalization.


The COVID-19 pandemic has led to urgent action by fertility clinics across the world. Many countries took the decision to suspend fertility treatments to mitigate the risk of spreading the infection, following international professional body guidance . Given the virulence of SARS-CoV-2 and our lack of knowledge of how it can affect medically assisted reproduction (MAR), suspension was the safest course of action.Viruses are a concern for MAR. In 2005, the European Union issued directives to ensure that all patients are screened for three blood-borne viruses HIV, HBV and HCV, prior to embarking on any form of MAR. More recently, mosquito-borne viruses have also been shown to affect fertility . For exaTypically, viruses that present with very high titres in blood (viremia) have a high chance of being shed in other body fluids such as sweat, urine, feces, breast milk and semen. To date, some 27 viruses have been detected in human semen . There iIn addition to viremia, other factors that can influence the existence of viruses in semen include the immune response in the male reproductive tract, inflammatory mediators that may alter the blood-testis barrier and the structural stability of the virus . The preSARS-CoV-2 belongs to the family Coronaviridae, alongside SARS-CoV and MERS-CoV. These viruses cause similar pathogenesis in the upper and lower respiratory tracts. Infectious SARS-CoV was detected in blood, urine and stools, while infectious MERS-CoV was not detected in nonrespiratory fluid . SARS-CoDiarrhea has been shown as one of the symptoms in COVID-19 patients, and the putative receptor ACE2 expression has been identified in absorptive enterocytes in the ileum and colon by using single-cell RNA sequencing; suggesting a potential route of infection of SARS-CoV-2 in the GI tract . Single-SARS-CoV-2 viral RNA has been detected in blood and feces, but recovery of viable viruses is yet to be observed ,13. It iAt the time of writing, two studies have reported no detection of SARS-CoV-2 viral RNA by RT-qPCR in semen or testicular tissue; one study from ten COVID-19 deceased patients  and anotOne study has now reported that SARS-CoV-2 has been detected in the semen of four out of 15 acutely ill and two out of 23 men recovering from COVID-19 . This rain situ hybridization. Moreover, Xu and colleagues reported higher levels of lymphocytes and macrophages in testicular interstitial tissue and suggested that the observed SARS-induced orchitis may not be due to viral replication but the inflammatory response in testicular tissues [The absence of infectious virus from semen does not preclude the possibility of SARS-CoV-2 affecting the male reproductive tract. SARS-CoV caused orchitis with widespread destruction of germ cells, such that the number of spermatozoa was severely reduced in the seminiferous tubules of six men who died from the disease . However tissues .About 20% of 34 males recovering from mild symptoms of COVID-19 have reported experiencing scrotal discomfort suggestive of orchitis, but the authors could not investigate this further . Taking Weighing up the evidence, and considering the presence of the blood–testes barrier, we suggest that there will be a negligible chance to have SARS-CoV-2 in semen of mildly infected COVID-19 patients, as already demonstrated in the report from Wuhan . The reaAlthough many fertility clinics and pathology labs suspended semen analysis during the height of the SARS-CoV-2 pandemic, other labs remained open. Even where diagnostic semen analysis was suspended, many pathology labs continued to perform postvasectomy semen analyses, indicating that they considered the risk of transmission to be minimal .Provided best laboratory practice is adhered to, then utmost caution should be taken when performing any type of semen analysis or semen processing for fertility treatment. Given that SARS-CoV-2 is an air-borne virus, additional care should be undertaken to avoid exposure of aerosols. Aerosol-generating events include the opening of specimen containers used to collect semen and the tubes used in sample centrifugation. During processing all tube lids should be tightly fitted and centrifuges should be used with aerosol-tight caps of centrifuge buckets. While staff in the laboratories of fertility clinics may wear appropriate personal protective equipment (PPE), these steps should become part of standard practice, if not already in use.Taking a cue from standard practice of cryopreserving viruses in laboratories, most viruses remain viable almost indefinitely at ultra-low temperatures if stored dried, in appropriate protein concentrations and between pH of 7 and 8 . For exaTo date, there is no evidence in the field of MAR for cross-contamination of any virus from one clinical sample to another while stored in liquid nitrogen or vapor phase storage. If SARS-CoV-2 was shed into a semen sample and cryopreserved in liquid nitrogen, there is almost no chance of cross-contaminating other samples while cryopreserved. However, best practice should be adhered to in MAR cryobanks, with storage of all samples in hermetically-sealed high security devices, with quarantined samples segregated from fully screened samples.At the time of writing, there are contradictory reports as to whether SARS-CoV-2 can be shed into semen of infected men. The current evidence could be considered poor quality due to the low patient numbers. As a precaution, men recovering from COVID-19 may wish to undergo a semen analysis to confirm if their fertility status has been affected by the illness.On a constructive note, the pandemic has provided an opportunity for fertility clinics to review their current practices and share perspectives with other professionals. As such, dissemination of good laboratory practice in fertility clinics worldwide may be a silver lining in the cloud cast by the COVID-19 pandemic.