Direct printing of 2-component silicones in facial & body prostheses

Traditionally maxillofacial prostheses are fabricated by hand carving the missing anatomical defect in wax, and creating a mould into which pigmented silicone elastomer is placed. Modern technologies have been used to manufacture anatomical face/body parts utilizing computed tomography (CT) data in conjunction with rapid prototyping (RP) techniques utilizing a hard plastic resin or thermoformed wax. However, these methods still require moulds into which a biocompatible pigmented silicone elastomer is placed. The purpose of this paper is to explore the development of direct printing of two component silicone elastomers in conjunction with a PVA support structure to create complex shapes using a customized 3D printer. A custom designed 3D printer with x- y-z gantry robot with an accuracy of 0.1µm was adapted with a custom designed printing head. Secondly, a two-component printable silicone elastomer was formulated that incorporated the desired characteristics and properties similar to those commercially available for the provision of facial and body prostheses. The silicone is composed of polydimethylsiloxane (PDMS) chains, filler, catalyst and cross-linker. Varying the amount of these components the mechanical properties of the silicone elastomer can be altered e.g. tensile strength, tear strength, hardness and wettability. To achieve these desired properties consideration must also be given to the set time and viscosity of the silicone elastomer and additionally the speed at which the material is printed. A thermal print head was used to deliver Polyvinyl acetate (PVA) to support the complex silicone shapes. Further development is needed to ensure appropriate digital colouring of the silicone elastomer to match the patients’ natural tissues. Ultimately, this would provide the maxillofacial prosthetist with a tool that manufactures prostheses reliably, with less emphasis placed on individual artistic interpretation. This technology has the potential to solve possible manufacturing solutions to complex shapes for both commercial and industry in addition to the current medical applications

CUP: Comprehensive User-Space Protection for C/C++

Memory corruption vulnerabilities in C/C++ applications enable attackers to execute code, change data, and leak information. Current memory sanitizers do no provide comprehensive coverage of a program's data. In particular, existing tools focus primarily on heap allocations with limited support for stack allocations and globals. Additionally, existing tools focus on the main executable with limited support for system libraries. Further, they suffer from both false positives and false negatives. We present Comprehensive User-Space Protection for C/C++, CUP, an LLVM sanitizer that provides complete spatial and probabilistic temporal memory safety for C/C++ program on 64-bit architectures (with a prototype implementation for x86_64). CUP uses a hybrid metadata scheme that supports all program data including globals, heap, or stack and maintains the ABI. Compared to existing approaches with the NIST Juliet test suite, CUP reduces false negatives by 10x (0.1%) compared to the state of the art LLVM sanitizers, and produces no false positives. CUP instruments all user-space code, including libc and other system libraries, removing them from the trusted code base

Policy-Directed Certificate Retrieval

Any large scale security architecture that uses certificates to provide security in a distributed system will need some automated support for moving certificates around in the network. We believe that for efficiency, this automated support should be tied closely to the consumer of the certificates: the policy verifier. As a proof of concept, we have built QCM, a prototype policy language and verifier that can direct a retrieval mechanism to obtain certificates from the network. Like previous verifiers, QCM takes a policy and certificates supplied by a requester and determines whether the policy is satisfied. Unlike previous verifiers, QCM can take further action if the policy is not satisfied: QCM can examine the policy to decide what certificates might help satisfy it and obtain them from remote servers on behalf of the requester. This takes place automatically, without intervention by the requester; there is no additional burden placed on the requester or the policy writer for the retrieval service we provide. We present examples that show how our technique greatly simplifies certificate-based secure applications ranging from key distribution to ratings systems, and that QCM policies are simple to write. We describe our implementation, and illustrate the operation of the prototype

Principal typings and type inference

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1996.Includes bibliographical references (p. 115-120) and index.by Trevor Jim.Ph.D

Developing intercultural competence in a ‘comfortable’ third space:postgraduate studies in the UK

With the number of international postgraduate students in UK universities steadily increasing, there is great interest in understanding how institutions can more effectively meet these students’ expectations and needs through programme-supported development of intercultural competence. This paper reports on a project that explored experiences and perceptions of the development of intercultural competence in a UK higher education context. Academic staff (N = 8) and international postgraduate students (N = 24), from a range of countries, were recruited for preliminary interviews (two staff from each of the four faculties), focus groups (students of these staff), and stimulated recall interviews (same staff). The project targeted tensions and issues occurring between the perspectives of participants. It focused on the performance and negotiation of identities in the ‘third space’ that emerged between participants using different cultural discourses. The findings suggest that, despite the inherent contradiction of comfort and the conflict of negotiation, efforts are made by both students and staff to create a ‘comfortable’ third space in which to negotiate learning. By this we mean an environment in which to negotiate learning where those present feel at ease with their own and others’ cultural identities and differences. This raises significant implications for policies and practices regarding the development of intercultural competence. Specifically, the university needs to build a better understanding of how to create a ‘sphere of interculturality’ in which international postgraduate learning can take place

Technical Education, Essays Dedicated to The Memory of Michael Clune: Pamphlet

A collection of essays dedicated to the memory of Michael Clune, a teacher with the City of Dublin Vocational Education Committee. Produced by a group of his colleagues and friends following his death in 1983

Formal Type Soundness for Cyclone's Region System

Cyclone is a polymorphic, type-safe programming language derived from C\@. The primary design goals of Cyclone are to let programmers control data representations and memory management without sacrificing type-safety. In this paper, we focus on the region-based memory management of Cyclone and its static typing discipline. The design incorporates several advancements, including support for region subtyping and a coherent integration with stack allocation and a garbage collector. To support separate compilation, Cyclone requires programmers to write some explicit region annotations, but uses a combination of default annotations, local type inference, and a novel treatment of region effects to reduce this burden. As a result, we integrate C idioms in a region-based framework. In our experience, porting legacy C to Cyclone has required altering about 8\% of the code; of the changes, only 6\% (of the 8\%) were region annotations. This technical report is really two documents in one: The first part is a paper submitted for publication in November, 2001. The second part is the full formal language and type-safety proof mentioned briefly in the first part. If you have already read a version of, ``Region-Based Memory Management in Cyclone'', then you should proceed directly to Section 9

Defeating Script Injection Attacks with Browser Enforced Embedded Policies

Web sites that accept and display content such as wiki articles or comments typically filter the content to prevent injected script code from running in browsers that view the site. The diversity of browser rendering algorithms and the desire to allow rich content makes filtering quite difficult, however, and attacks such as the Samy and Yamanner worms have exploited filtering weaknesses. To solve this problem, this paper proposes a simple mechanism called Browser-Enforced Embedded Policies (BEEP). The idea is that a web site can embed a policy inside its pages that specifies which scripts are allowed to run. The browser, which knows exactly when it will run a script, can enforce this policy perfectly. We have added BEEP support to several browsers, and built tools to simplify adding policies to web applications. We found that supporting BEEP in browsers requires only small and localized modifications, modifying web applications requires minimal effort, and enforcing policies is generally lightweight

Conditions under which glutathione disrupts the biofilms and improves antibiotic efficacy of both ESKAPE and NON-ESKAPE species

Bacterial antibiotic resistance has increased in recent decades, raising concerns in hospital and community settings. Novel, innovative strategies are needed to eradicate bacteria, particularly within biofilms, and diminish the likelihood of recurrence. In this study, we investigated whether glutathione (GSH) can act as a biofilm disruptor, and enhance antibiotic effectiveness against various bacterial pathogens. Biological levels (10 mM) of GSH did not have a significant effect in inhibiting growth or disrupting the biofilm in four out of six species tested. However, exposure to 30 mM GSH showed >50% decrease in growth for all bacterial species, with almost 100% inhibition of Streptococcus pyogenes and an average of 94–52% inhibition for Escherichia coli, Methicillin-resistant Staphylococcus aureus (MRSA) and Methicillin-sensitive S. aureus (MSSA) and multi-drug resistant Acinetobacter baumannii (MRAB) isolates, respectively. Klebsiella pneumoniae and Enterobacter sp. isolates were however, highly resistant to 30 mM GSH. With respect to biofilm viability, all species exhibited a >50% decrease in viability with 30 mM GSH, with confocal imaging showing considerable change in the biofilm architecture of MRAB isolates. The mechanism of GSH-mediated biofilm disruption is possibly due to a concentration-dependent increase in GSH acidity that triggers cleaving of the matrix components. Enzymatic treatment of MRAB revealed that eDNA and polysaccharides are essential for biofilm stability and eDNA removal enhanced amikacin efficiency. Combination of GSH, amikacin and DNase-I showed the greatest reduction in MRAB biofilm viability. Additionally, GSH alone and in combination with amikacin fostered human fibroblast cell (HFF-1) growth and confluence while inhibiting MRAB adhesion and colonization