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Although nickel allergy is the most frequent contact hypersensitivity in man, reports on successful nickel sensitization in experimental animals are scarce. Chromium hypersensitivity, on the other hand, is readily induced in guinea pigs. In this study we set out to obtain reproducible nickel sensitization in guinea pigs, in order to establish an animal model for immunospecific tolerance and desensitization studies in which two non-cross-reacting metal allergens, chromium and nickel, could be studied simultaneously. Strong and reproducible sensitization to nickel was achieved by injecting low amounts of Freund's complete adjuvant and nickel sulfate in a split-adjuvant procedure. Strong erythematous reactions were observed as early as 14 days after sensitization and could be elicited both by intradermal and open epicutaneous challenges. Optimal evaluation was with nickel sulfate administered epicutaneously in 40% dimethyl sulfoxide to enhance skin penetration. Hypersensitivity could be transferred with lymphocytes and not with serum. Sensitization procedures for nickel and chromium then could successfully be combined in a double sensitization procedure. With four different guinea pig strains no genetic restriction was observed for the induction of nickel or chromium sensitivity. However, for both metals a clear sex and age dependence was observed: female guinea pigs reached a higher degree of sensitization than males, whereas sensitization in young animals was relatively weak.

SUMMARY From animal studies we know that oral administration of T-dependent antigens before sensitization effectively induces systemic immune unresponsiveness. Such ‘oral tolerance’ is persistent, dose-dependent, antigen-specific and presumably T suppressor cell-mediated. Oral tolerance induction could be an effective way to prevent undesired T cell-mediated immune functions, such as playing a role in allograft reaction, autoimmune and allergic diseases. In the present study allergic contact hypersensitivity (ACH) to nickel, currently presenting the most frequent contact allergy in man, was chosen to establish the feasibility of oral prevention of undesired T cell-mediated immunity in man. Potentially tolerizing (oral nickel contacts via orthodontic braces) as well as sensitizing (ear piercing) events were studied retrospectively in 2176 patients attending nine European patch test clinics. Patients were interviewed by means of a confidential questionnaire. The results show that ear piercing strongly favoured development of nickel ACH. More importantly, patients having had oral contacts with nickel-releasing appliances (dental braces) at an early age, but only if prior to ear piercing, showed a reduced frequency of nickel hypersensitivity. Frequencies of other hypersensitivities, in particular to fragrance, were not affected. These results support our view that induction of specific systemic immunologic tolerance by timely oral administration of antigens is feasible in man.

Aufgabe der vorliegenden Erfindung ist es, einen Gittersensor vorzuschlagen, mit dem der Aufwand des Fertigungsprozesses sowie die Einbau- und Betriebskosten für den Gittersensor deutlich verringert und die Haltbarkeit sowie Druck- und Temperaturfestigkeit des Gittersensors gegenüber bisherigen Gittersensoren deutlich erhöht werden können. Die technische Lösung beinhaltet im Wesentlichen, dass vom Rand des Messquerschnitts (2) aus Kanäle (3) mit einer Breite von mehr als dem Durchmesser der Drahtelektroden (6) und mit einer Tiefe von weniger als der halben Dicke der Sensorplatine (1) in dieser nach außen verlaufen, dass die Kanäle (3) mit einer Metallschicht (5) ausgekleidet sind, dass die Drahtelektroden (6) mit ihren beiden Enden jeweils in einem der gegenüberliegenden Kanäle (3) an der Peripherie des Messquerschnitts (2) eingelegt und in den Kanälen (3) mittels leitfähiger Verschlussmasse (8) fixiert sind, dass die leitfähige Verschlussmasse (8) in jedem Kanal (3) mit der Oberseite der Sensorplatine (1) plan abschließt und dass die Sensorplatine (1) zwischen zwei Spannplatten (10) eingespannt ist. Fig. 2

PCsat was designed and built as a student project at the US Naval Academy and launched on 29 Sept 2001 on the Kodiak Star mission as an experimental communications payload to not only introduce students to space systems engineering, but also to begin a series of experiments in low cost spacecraft telemetry system and data communications for mobile satellite users. An additional unique feature of PCsat was the integration of multiple worldwide Internet linked ground stations allowing around the world access to satellite telemetry and communications live from anywhere. PCsat was a complete success and it has been used by thousands of users in its first 9 months of flight. It has validated the viability of our using off-the-shelf AX.25 for all Telemetry Command and Control as well as supporting a bent-pipe mission. As our first satellite, we have a lot of lessons learned and experiences with spacecraft operations and many ideas for the future. This paper sumarizes the design details for PCsat and highlights of the first year in space including what we have learned and what new experiments we want to do on our next communications mission.

There are growing opportunities for Universities to gain educational access to Space. The Naval Academy has used the Department of Defense Space Test Program for its PCsat and Sapphire projects and the Stanford Cubesat program offers a unique opportunity to get numerous small student satellite payloads into space. As a spin-off of our PCsat project, we have investigated several off-the-shelf solutions to the Telemetry, Command and control portion of small satellites that can greatly simplify small satellite and CubeSat designs. This permits students to concentrate on the various payloads and other aspects of the project without starting from scratch with a comm. system. This simple comm. System based on AX.25 packet radio is being flown this summer in the Naval Academy’s Personal Communications Satellite (PCsat) which will demonstrate downlinks receivable on Hand Held Transceivers (HT’s) with only a whip antenna. Further these simple downlinks can be easily fed into the Internet for live worldwide distribution of data. These designs are all based on the amateur radio standard on-air AX.25 packet network protocol that is implemented in a number of off-the-shelf modems (called Terminal Node Controllers or TNC’s). The following paragraphs describe three such hardware devices and the remainder of this paper describes how TNC’s and the AX.25 protocol were used on PCsat.