Auswahl der wissenschaftlichen Literatur zum Thema „DmvA Architecten“

The paper compares and evaluates the influence of the presence of perforations on the sound absorption coefficient (SAC) of a negative stiffness metamaterial based on a foamed ceramic geopolymer. Chemical–physical, microstructural, dynamic–mechanical, and sound characterisations are presented. A rigid, lightweight geopolymeric porous material has been prepared using an inorganic/organic monomeric mixture containing oligomeric sialates and siloxanes foamed with aluminium powder. This process results in an amorphous rigid light foam with an apparent 180 Kg/m3 density and a 78% open-pore. The viscoelastic characterisation by dynamic mechanical analysis (DMA) carried out from 10−3 to 103 Hz indicates the behaviour of a mechanical metamaterial with negative stiffness enabling ultrahigh energy absorption at straining frequencies from 300 to 1000 Hz. The material loss factor (the ratio of dissipative/elastic shear moduli) is about 0.03 (essentially elastic behaviour) for frequencies up to 200 Hz to suddenly increase up to a value of six at 1000 Hz (highly dissipative behaviour). The corresponding storage and loss moduli were 8.2 MPa and 20 MPa, respectively. Impedance tube acoustic absorption measurements on perforated and unperforated specimens highlighted the role of perforation-resonant cavities in enhancing sound absorption efficiency, particularly within the specified frequency band where the mass of the negative stiffness foamed geopolymer matrix magnifies the dissipation effect. In the limits of a still exploratory and comparative study, we aimed to verify the technological transfer potentiality of using architected metamaterials in sustainable building practices.

Virus infection is a process that requires combined contributions from both virus and host factors. For this process to be efficient within the crowded host environment, viruses have evolved ways to manipulate and reorganize host structures to produce cellular microenvironments. Positive-strand RNA virus replication and assembly occurs in association with cytoplasmic membranes, causing a reorganization of these membranes to create microenvironments that support viral processes. Similarities between virus-induced membrane domains and cellular organelles have led to the description of these structures as virus replication organelles (vRO). Electron microscopy analysis of vROs in positive-strand RNA virus infected cells has revealed surprising morphological similarities between genetically diverse virus species. For all positive-strand RNA viruses, vROs can be categorized into two groups: those that make invaginations into the cellular membranes (In-vRO), and those that cause the production of protrusions from cellular membranes (Pr-vRO), most often in the form of double membrane vesicles (DMVs). In this review, we will discuss the current knowledge on the structure and biogenesis of these two different vRO classes as well as comparing morphology and function of vROs between various positive-strand RNA viruses. Finally, we will discuss recent studies describing pharmaceutical intervention in vRO formation as an avenue to control virus infection.

“As the old technologies become automatic and invisible, we find ourselves more concerned with fighting or embracing what’s new”—Dennis Baron, From Pencils to Pixels: The Stage of Literacy Technologies What constitutes a computer, as we have come to expect it? Are they necessarily monolithic “beige boxes”, connected to computer monitors, sitting on computer desks, located in computer rooms or computer labs? In order for a device to be considered a true computer, does it need to have a keyboard and mouse? If this were 1991 or earlier, our collective perception of what computers are and are not would largely be framed by this “beige box” model: computers are stationary, slab-like, and heavy, and their natural habitats must be in rooms specifically designated for that purpose. In 1992, when Apple introduced the first PowerBook, our perception began to change. Certainly there had been other portable computers prior to that, such as the Osborne 1, but these were more luggable than portable, weighing just slightly less than a typical sewing machine. The PowerBook and subsequent waves of laptops, personal digital assistants (PDAs), and so-called smart phones from numerous other companies have steadily forced us to rethink and redefine what a computer is and is not, how we interact with them, and the manner in which these tools might be used in the classroom. However, this reconceptualization of computers is far from over, and is in fact steadily evolving as new devices are introduced, adopted, and subsequently adapted for uses beyond of their original purpose. Pat Crowe’s Book Reader project, for example, has morphed Nintendo’s GameBoy and GameBoy Advance into a viable electronic book platform, complete with images, sound, and multi-language support. (Crowe, 2003) His goal was to take this existing technology previously framed only within the context of proprietary adolescent entertainment, and repurpose it for open, flexible uses typically associated with learning and literacy. Similar efforts are underway to repurpose Microsoft’s Xbox, perhaps the ultimate symbol of “closed” technology given Microsoft’s propensity for proprietary code, in order to make it a viable platform for Open Source Software (OSS). However, these efforts are not forgone conclusions, and are in fact typical of the ongoing battle over who controls the technology we own in our homes, and how open source solutions are often at odds with a largely proprietary world. In late 2001, Microsoft launched the Xbox with a multimillion dollar publicity drive featuring events, commercials, live models, and statements claiming this new console gaming platform would “change video games the way MTV changed music”. (Chan, 2001) The Xbox launched with the following technical specifications: 733mhz Pentium III 64mb RAM, 8 or 10gb internal hard disk drive CD/DVD ROM drive (speed unknown) Nvidia graphics processor, with HDTV support 4 USB 1.1 ports (adapter required), AC3 audio 10/100 ethernet port, Optional 56k modem (TechTV, 2001) While current computers dwarf these specifications in virtually all areas now, for 2001 these were roughly on par with many desktop systems. The retail price at the time was $299, but steadily dropped to nearly half that with additional price cuts anticipated. Based on these features, the preponderance of “off the shelf” parts and components used, and the relatively reasonable price, numerous programmers quickly became interested in seeing it if was possible to run Linux and additional OSS on the Xbox. In each case, the goal has been similar: exceed the original purpose of the Xbox, to determine if and how well it might be used for basic computing tasks. If these attempts prove to be successful, the Xbox could allow institutions to dramatically increase the student-to-computer ratio in select environments, or allow individuals who could not otherwise afford a computer to instead buy and Xbox, download and install Linux, and use this new device to write, create, and innovate . This drive to literally and metaphorically “open” the Xbox comes from many directions. Such efforts include Andrew Huang’s self-published “Hacking the Xbox” book in which, under the auspices of reverse engineering, Huang analyzes the architecture of the Xbox, detailing step-by-step instructions for flashing the ROM, upgrading the hard drive and/or RAM, and generally prepping the device for use as an information appliance. Additional initiatives include Lindows CEO Michael Robertson’s $200,000 prize to encourage Linux development on the Xbox, and the Xbox Linux Project at SourceForge. What is Linux? Linux is an alternative operating system initially developed in 1991 by Linus Benedict Torvalds. Linux was based off a derivative of the MINIX operating system, which in turn was a derivative of UNIX. (Hasan 2003) Linux is currently available for Intel-based systems that would normally run versions of Windows, PowerPC-based systems that would normally run Apple’s Mac OS, and a host of other handheld, cell phone, or so-called “embedded” systems. Linux distributions are based almost exclusively on open source software, graphic user interfaces, and middleware components. While there are commercial Linux distributions available, these mainly just package the freely available operating system with bundled technical support, manuals, some exclusive or proprietary commercial applications, and related services. Anyone can still download and install numerous Linux distributions at no cost, provided they do not need technical support beyond the community / enthusiast level. Typical Linux distributions come with open source web browsers, word processors and related productivity applications (such as those found in OpenOffice.org), and related tools for accessing email, organizing schedules and contacts, etc. Certain Linux distributions are more or less designed for network administrators, system engineers, and similar “power users” somewhat distanced from that of our students. However, several distributions including Lycoris, Mandrake, LindowsOS, and other are specifically tailored as regular, desktop operating systems, with regular, everyday computer users in mind. As Linux has no draconian “product activation key” method of authentication, or digital rights management-laden features associated with installation and implementation on typical desktop and laptop systems, Linux is becoming an ideal choice both individually and institutionally. It still faces an uphill battle in terms of achieving widespread acceptance as a desktop operating system. As Finnie points out in Desktop Linux Edges Into The Mainstream: “to attract users, you need ease of installation, ease of device configuration, and intuitive, full-featured desktop user controls. It’s all coming, but slowly. With each new version, desktop Linux comes closer to entering the mainstream. It’s anyone’s guess as to when critical mass will be reached, but you can feel the inevitability: There’s pent-up demand for something different.” (Finnie 2003) Linux is already spreading rapidly in numerous capacities, in numerous countries. Linux has “taken hold wherever computer users desire freedom, and wherever there is demand for inexpensive software.” Reports from technology research company IDG indicate that roughly a third of computers in Central and South America run Linux. Several countries, including Mexico, Brazil, and Argentina, have all but mandated that state-owned institutions adopt open source software whenever possible to “give their people the tools and education to compete with the rest of the world.” (Hills 2001) The Goal Less than a year after Microsoft introduced the The Xbox, the Xbox Linux project formed. The Xbox Linux Project has a goal of developing and distributing Linux for the Xbox gaming console, “so that it can be used for many tasks that Microsoft don’t want you to be able to do. ...as a desktop computer, for email and browsing the web from your TV, as a (web) server” (Xbox Linux Project 2002). Since the Linux operating system is open source, meaning it can freely be tinkered with and distributed, those who opt to download and install Linux on their Xbox can do so with relatively little overhead in terms of cost or time. Additionally, Linux itself looks very “windows-like”, making for fairly low learning curve. To help increase overall awareness of this project and assist in diffusing it, the Xbox Linux Project offers step-by-step installation instructions, with the end result being a system capable of using common peripherals such as a keyboard and mouse, scanner, printer, a “webcam and a DVD burner, connected to a VGA monitor; 100% compatible with a standard Linux PC, all PC (USB) hardware and PC software that works with Linux.” (Xbox Linux Project 2002) Such a system could have tremendous potential for technology literacy. Pairing an Xbox with Linux and OpenOffice.org, for example, would provide our students essentially the same capability any of them would expect from a regular desktop computer. They could send and receive email, communicate using instant messaging IRC, or newsgroup clients, and browse Internet sites just as they normally would. In fact, the overall browsing experience for Linux users is substantially better than that for most Windows users. Internet Explorer, the default browser on all systems running Windows-base operating systems, lacks basic features standard in virtually all competing browsers. Native blocking of “pop-up” advertisements is still not yet possible in Internet Explorer without the aid of a third-party utility. Tabbed browsing, which involves the ability to easily open and sort through multiple Web pages in the same window, often with a single mouse click, is also missing from Internet Explorer. The same can be said for a robust download manager, “find as you type”, and a variety of additional features. Mozilla, Netscape, Firefox, Konqueror, and essentially all other OSS browsers for Linux have these features. Of course, most of these browsers are also available for Windows, but Internet Explorer is still considered the standard browser for the platform. If the Xbox Linux Project becomes widely diffused, our students could edit and save Microsoft Word files in OpenOffice.org’s Writer program, and do the same with PowerPoint and Excel files in similar OpenOffice.org components. They could access instructor comments originally created in Microsoft Word documents, and in turn could add their own comments and send the documents back to their instructors. They could even perform many functions not yet capable in Microsoft Office, including saving files in PDF or Flash format without needing Adobe’s Acrobat product or Macromedia’s Flash Studio MX. Additionally, by way of this project, the Xbox can also serve as “a Linux server for HTTP/FTP/SMB/NFS, serving data such as MP3/MPEG4/DivX, or a router, or both; without a monitor or keyboard or mouse connected.” (Xbox Linux Project 2003) In a very real sense, our students could use these inexpensive systems previously framed only within the context of entertainment, for educational purposes typically associated with computer-mediated learning. Problems: Control and Access The existing rhetoric of technological control surrounding current and emerging technologies appears to be stifling many of these efforts before they can even be brought to the public. This rhetoric of control is largely typified by overly-restrictive digital rights management (DRM) schemes antithetical to education, and the Digital Millennium Copyright Act (DMCA). Combined,both are currently being used as technical and legal clubs against these efforts. Microsoft, for example, has taken a dim view of any efforts to adapt the Xbox to Linux. Microsoft CEO Steve Ballmer, who has repeatedly referred to Linux as a cancer and has equated OSS as being un-American, stated, “Given the way the economic model works - and that is a subsidy followed, essentially, by fees for every piece of software sold - our license framework has to do that.” (Becker 2003) Since the Xbox is based on a subsidy model, meaning that Microsoft actually sells the hardware at a loss and instead generates revenue off software sales, Ballmer launched a series of concerted legal attacks against the Xbox Linux Project and similar efforts. In 2002, Nintendo, Sony, and Microsoft simultaneously sued Lik Sang, Inc., a Hong Kong-based company that produces programmable cartridges and “mod chips” for the PlayStation II, Xbox, and Game Cube. Nintendo states that its company alone loses over $650 million each year due to piracy of their console gaming titles, which typically originate in China, Paraguay, and Mexico. (GameIndustry.biz) Currently, many attempts to “mod” the Xbox required the use of such chips. As Lik Sang is one of the only suppliers, initial efforts to adapt the Xbox to Linux slowed considerably. Despite that fact that such chips can still be ordered and shipped here by less conventional means, it does not change that fact that the chips themselves would be illegal in the U.S. due to the anticircumvention clause in the DMCA itself, which is designed specifically to protect any DRM-wrapped content, regardless of context. The Xbox Linux Project then attempted to get Microsoft to officially sanction their efforts. They were not only rebuffed, but Microsoft then opted to hire programmers specifically to create technological countermeasures for the Xbox, to defeat additional attempts at installing OSS on it. Undeterred, the Xbox Linux Project eventually arrived at a method of installing and booting Linux without the use of mod chips, and have taken a more defiant tone now with Microsoft regarding their circumvention efforts. (Lettice 2002) They state that “Microsoft does not want you to use the Xbox as a Linux computer, therefore it has some anti-Linux-protection built in, but it can be circumvented easily, so that an Xbox can be used as what it is: an IBM PC.” (Xbox Linux Project 2003) Problems: Learning Curves and Usability In spite of the difficulties imposed by the combined technological and legal attacks on this project, it has succeeded at infiltrating this closed system with OSS. It has done so beyond the mere prototype level, too, as evidenced by the Xbox Linux Project now having both complete, step-by-step instructions available for users to modify their own Xbox systems, and an alternate plan catering to those who have the interest in modifying their systems, but not the time or technical inclinations. Specifically, this option involves users mailing their Xbox systems to community volunteers within the Xbox Linux Project, and basically having these volunteers perform the necessary software preparation or actually do the full Linux installation for them, free of charge (presumably not including shipping). This particular aspect of the project, dubbed “Users Help Users”, appears to be fairly new. Yet, it already lists over sixty volunteers capable and willing to perform this service, since “Many users don’t have the possibility, expertise or hardware” to perform these modifications. Amazingly enough, in some cases these volunteers are barely out of junior high school. One such volunteer stipulates that those seeking his assistance keep in mind that he is “just 14” and that when performing these modifications he “...will not always be finished by the next day”. (Steil 2003) In addition to this interesting if somewhat unusual level of community-driven support, there are currently several Linux-based options available for the Xbox. The two that are perhaps the most developed are GentooX, which is based of the popular Gentoo Linux distribution, and Ed’s Debian, based off the Debian GNU / Linux distribution. Both Gentoo and Debian are “seasoned” distributions that have been available for some time now, though Daniel Robbins, Chief Architect of Gentoo, refers to the product as actually being a “metadistribution” of Linux, due to its high degree of adaptability and configurability. (Gentoo 2004) Specifically, the Robbins asserts that Gentoo is capable of being “customized for just about any application or need. ...an ideal secure server, development workstation, professional desktop, gaming system, embedded solution or something else—whatever you need it to be.” (Robbins 2004) He further states that the whole point of Gentoo is to provide a better, more usable Linux experience than that found in many other distributions. Robbins states that: “The goal of Gentoo is to design tools and systems that allow a user to do their work pleasantly and efficiently as possible, as they see fit. Our tools should be a joy to use, and should help the user to appreciate the richness of the Linux and free software community, and the flexibility of free software. ...Put another way, the Gentoo philosophy is to create better tools. When a tool is doing its job perfectly, you might not even be very aware of its presence, because it does not interfere and make its presence known, nor does it force you to interact with it when you don’t want it to. The tool serves the user rather than the user serving the tool.” (Robbins 2004) There is also a so-called “live CD” Linux distribution suitable for the Xbox, called dyne:bolic, and an in-progress release of Slackware Linux, as well. According to the Xbox Linux Project, the only difference between the standard releases of these distributions and their Xbox counterparts is that “...the install process – and naturally the bootloader, the kernel and the kernel modules – are all customized for the Xbox.” (Xbox Linux Project, 2003) Of course, even if Gentoo is as user-friendly as Robbins purports, even if the Linux kernel itself has become significantly more robust and efficient, and even if Microsoft again drops the retail price of the Xbox, is this really a feasible solution in the classroom? Does the Xbox Linux Project have an army of 14 year olds willing to modify dozens, perhaps hundreds of these systems for use in secondary schools and higher education? Of course not. If such an institutional rollout were to be undertaken, it would require significant support from not only faculty, but Department Chairs, Deans, IT staff, and quite possible Chief Information Officers. Disk images would need to be customized for each institution to reflect their respective needs, ranging from setting specific home pages on web browsers, to bookmarks, to custom back-up and / or disk re-imaging scripts, to network authentication. This would be no small task. Yet, the steps mentioned above are essentially no different than what would be required of any IT staff when creating a new disk image for a computer lab, be it one for a Windows-based system or a Mac OS X-based one. The primary difference would be Linux itself—nothing more, nothing less. The institutional difficulties in undertaking such an effort would likely be encountered prior to even purchasing a single Xbox, in that they would involve the same difficulties associated with any new hardware or software initiative: staffing, budget, and support. If the institutional in question is either unwilling or unable to address these three factors, it would not matter if the Xbox itself was as free as Linux. An Open Future, or a Closed one? It is unclear how far the Xbox Linux Project will be allowed to go in their efforts to invade an essentially a proprietary system with OSS. Unlike Sony, which has made deliberate steps to commercialize similar efforts for their PlayStation 2 console, Microsoft appears resolute in fighting OSS on the Xbox by any means necessary. They will continue to crack down on any companies selling so-called mod chips, and will continue to employ technological protections to keep the Xbox “closed”. Despite clear evidence to the contrary, in all likelihood Microsoft continue to equate any OSS efforts directed at the Xbox with piracy-related motivations. Additionally, Microsoft’s successor to the Xbox would likely include additional anticircumvention technologies incorporated into it that could set the Xbox Linux Project back by months, years, or could stop it cold. Of course, it is difficult to say with any degree of certainty how this “Xbox 2” (perhaps a more appropriate name might be “Nextbox”) will impact this project. Regardless of how this device evolves, there can be little doubt of the value of Linux, OpenOffice.org, and other OSS to teaching and learning with technology. This value exists not only in terms of price, but in increased freedom from policies and technologies of control. New Linux distributions from Gentoo, Mandrake, Lycoris, Lindows, and other companies are just now starting to focus their efforts on Linux as user-friendly, easy to use desktop operating systems, rather than just server or “techno-geek” environments suitable for advanced programmers and computer operators. While metaphorically opening the Xbox may not be for everyone, and may not be a suitable computing solution for all, I believe we as educators must promote and encourage such efforts whenever possible. I suggest this because I believe we need to exercise our professional influence and ultimately shape the future of technology literacy, either individually as faculty and collectively as departments, colleges, or institutions. Moran and Fitzsimmons-Hunter argue this very point in Writing Teachers, Schools, Access, and Change. One of their fundamental provisions they use to define “access” asserts that there must be a willingness for teachers and students to “fight for the technologies that they need to pursue their goals for their own teaching and learning.” (Taylor / Ward 160) Regardless of whether or not this debate is grounded in the “beige boxes” of the past, or the Xboxes of the present, much is at stake. Private corporations should not be in a position to control the manner in which we use legally-purchased technologies, regardless of whether or not these technologies are then repurposed for literacy uses. I believe the exigency associated with this control, and the ongoing evolution of what is and is not a computer, dictates that we assert ourselves more actively into this discussion. We must take steps to provide our students with the best possible computer-mediated learning experience, however seemingly unorthodox the technological means might be, so that they may think critically, communicate effectively, and participate actively in society and in their future careers. About the Author Paul Cesarini is an Assistant Professor in the Department of Visual Communication & Technology Education, Bowling Green State University, Ohio Email: pcesari@bgnet.bgsu.edu Works Cited http://xbox-linux.sourceforge.net/docs/debian.php>.Baron, Denis. “From Pencils to Pixels: The Stages of Literacy Technologies.” Passions Pedagogies and 21st Century Technologies. Hawisher, Gail E., and Cynthia L. Selfe, Eds. Utah: Utah State University Press, 1999. 15 – 33. Becker, David. “Ballmer: Mod Chips Threaten Xbox”. News.com. 21 Oct 2002. http://news.com.com/2100-1040-962797.php>. http://news.com.com/2100-1040-978957.html?tag=nl>. http://archive.infoworld.com/articles/hn/xml/02/08/13/020813hnchina.xml>. http://www.neoseeker.com/news/story/1062/>. http://www.bookreader.co.uk>.Finni, Scott. “Desktop Linux Edges Into The Mainstream”. TechWeb. 8 Apr 2003. http://www.techweb.com/tech/software/20030408_software. http://www.theregister.co.uk/content/archive/29439.html http://gentoox.shallax.com/. http://ragib.hypermart.net/linux/. http://www.itworld.com/Comp/2362/LWD010424latinlinux/pfindex.html. http://www.xbox-linux.sourceforge.net. http://www.theregister.co.uk/content/archive/27487.html. http://www.theregister.co.uk/content/archive/26078.html. http://www.us.playstation.com/peripherals.aspx?id=SCPH-97047. http://www.techtv.com/extendedplay/reviews/story/0,24330,3356862,00.html. http://www.wired.com/news/business/0,1367,61984,00.html. http://www.gentoo.org/main/en/about.xml http://www.gentoo.org/main/en/philosophy.xml http://techupdate.zdnet.com/techupdate/stories/main/0,14179,2869075,00.html. http://xbox-linux.sourceforge.net/docs/usershelpusers.html http://www.cnn.com/2002/TECH/fun.games/12/16/gamers.liksang/. Citation reference for this article MLA Style Cesarini, Paul. "“Opening” the Xbox" M/C: A Journal of Media and Culture <http://www.media-culture.org.au/0406/08_Cesarini.php>. APA Style Cesarini, P. (2004, Jul1). “Opening” the Xbox. M/C: A Journal of Media and Culture, 7, <http://www.media-culture.org.au/0406/08_Cesarini.php>

Abstract Additive manufacturing (AM) of metals can enable rapid development of functional parts of complex geometry, with potential applications in the aerospace, automotive, and biomedical fields [1–3]. Typical metal additive manufacturing techniques are based on expensive laser melting or sintering processes which are often highly anisotropic, limiting the development and use of these methods. Furthermore, few additive manufacturing techniques focus on high temperature materials, ceramics, and fabrication of machine elements. The recent introduction of Hydrogel-Infusion Additive Manufacturing (HIAM) may reduce some of these barriers, enabling potential applications in high performance metal and ceramic devices and components. The HIAM process involves 3D printing a polyethylene oxide (PEO) photo-resin using vat polymerization, immersing the polymer in a metal salt solution which allows ionized metal cations to bond to the polymer backbone, followed by calcination to combust the polymer leaving a metal oxide that takes the same functional structure as the original polymer. Finally, the metal oxide is reduced using a forming gas (95% N2/5% H2) to give a metal product that maintains a scaled-down version of the complex as-printed architecture. This technique enables architected features with microscale resolution by use of a single photoresin simply by varying post-processing conditions. As a first step in the fabrication of machine elements and devices, this paper outlines an attempt to fabricate springs made from silver metal via HIAM. Silver nitrate is infused into an additively manufactured polymer spring structure. Based on the relative differences in the standard free energy of the oxides, Silver Oxide (AgO) is readily reduced to metallic silver under a single thermal processing step: calcination/reduction at 500°C without the need for forming gas. A variety of analytical techniques confirm HIAM processing obeys chemical kinetics of single-step calcination and reduction in accordance with literature and results in fabricated components of low microstrain (8.40E−7 ± 2.78E−9) crystalline silver with average crystallite size of 514.95 ± 5.32 Å and lattice parameter of 4.09 ± 5.23E−5 Å. Thermal analyses such as Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) elucidate the mass loss and reactions that occur during the furnace processing. Springs were subjected to quasi-static and cyclic loading using a Dynamic Mechanical Analyzer (DMA). A range of ∼2–20 N/mm stiffness was measured in unloading for different coil diameters and produced springs show consistency of part stiffness following compaction under cyclic loading.