Building a GPS Receiver for Space Lessons Learned

Over the past 4 years the Component Systems and Hardware branch at NASA GSFC has pursued an inhouse effort to build a unique space-flight GPS receiver. This effort has resulted in the Navigator GPS receiver. Navigator's first flight opportunity will come with the STS-125 HST-SM4 mission in August 2008. This paper covers the overall hardware design for the receiver and the difficulties encountered during the transition from the breadboard design to the final flight hardware design. Among the different lessons learned, the paper stresses the importance of selecting and verifying parts that are appropriate for space applications, as well as what happens when these parts are not accurately characterized by their datasheets. Additionally, the paper discusses what analysis needs to be performed when deciding system frequencies and filters. The presentation also covers how to prepare for thermal vacuum testing, and problems that may arise during vibration testing. It also contains what criteria should be considered when determining which portions of a design to create in-house, and which portions to license from a third party. Finally, the paper shows techniques which have proven to be extraordinarily helpful in debugging and analysis

Generating acceptable Arabic Core Vocabularies and Symbols for AAC users

This paper discusses the development of an Arabic Symbol Dictionary for Augmentative and Alternative Communication (AAC) users, their families, carers, therapists and teachers as well as those who may benefit from the use of symbols to enhance literacy skills. With a requirement for a bi-lingual dictionary, a vocabulary list analyzer has been developed to evaluate similarities and differences in word frequencies from a range of word lists in order to collect suitable AAC lexical entries. An online bespoke symbol management has been created to hold the lexical entries alongside specifically designed symbols which are then accepted via a voting system using a series of criteria. Results to date have highlighted how successful these systems can be when encouraging participation along with the need for further research into the development of personalised context sensitive core vocabularies

Tendinopathy—from basic science to treatment

Chronic tendon pathology (tendinopathy), although common, is difficult to treat. Tendons possess a highly organized fibrillar matrix, consisting of type I collagen and various 'minor' collagens, proteoglycans and glycoproteins. The tendon matrix is maintained by the resident tenocytes, and there is evidence of a continuous process of matrix remodeling, although the rate of turnover varies at different sites. A change in remodeling activity is associated with the onset of tendinopathy. Major molecular changes include increased expression of type III collagen, fibronectin, tenascin C, aggrecan and biglycan. These changes are consistent with repair, but they might also be an adaptive response to changes in mechanical loading. Repeated minor strain is thought to be the major precipitating factor in tendinopathy, although further work is required to determine whether it is mechanical overstimulation or understimulation that leads to the change in tenocyte activity. Metalloproteinase enzymes have an important role in the tendon matrix, being responsible for the degradation of collagen and proteoglycan in both healthy patients and those with disease. Metalloproteinases that show increased expression in painful tendinopathy include ADAM (a disintegrin and metalloproteinase)-12 and MMP (matrix metalloproteinase)-23. The role of these enzymes in tendon pathology is unknown, and further work is required to identify novel and specific molecular targets for therapy

Why a successful task substitution in glaucoma care could not be transferred from a hospital setting to a primary care setting: A qualitative study

Background: Healthcare systems are challenged by a demand that exceeds available resources. One policy to meet this challenge is task substitution-transferring tasks to other professions and settings. Our study aimed to explore stakeholders' perceived feasibility of transferring hospital-based monitoring of stable glaucoma patients to primary care optometrists.Methods: A case study was undertaken in the Rotterdam Eye Hospital (REH) using semi-structured interviews and document reviews. They were inductively analysed using three implementation related theoretical perspectives: sociological theories on professionalism, management theories, and applied political analysis.Results: Currently it is not feasible to use primary care optometrists as substitutes for optometrists and ophthalmic technicians working in a hospital-based gl

The design and implementation of a study to investigate the effectiveness of community vs hospital eye service follow-up for patients with neovascular age-related macular degeneration with quiescent disease

IntroductionStandard treatment for neovascular age-related macular degeneration (nAMD) is intravitreal injections of anti-VEGF drugs. Following multiple injections, nAMD lesions often become quiescent but there is a high risk of reactivation, and regular review by hospital ophthalmologists is the norm. The present trial examines the feasibility of community optometrists making lesion reactivation decisions.MethodsThe Effectiveness of Community vs Hospital Eye Service (ECHoES) trial is a virtual trial; lesion reactivation decisions were made about vignettes that comprised clinical data, colour fundus photographs, and optical coherence tomograms displayed on a web-based platform. Participants were either hospital ophthalmologists or community optometrists. All participants were provided with webinar training on the disease, its management, and assessment of the retinal imaging outputs. In a balanced design, 96 participants each assessed 42 vignettes; a total of 288 vignettes were assessed seven times by each professional group.The primary outcome is a participant's judgement of lesion reactivation compared with a reference standard. Secondary outcomes are the frequency of sight threatening errors; judgements about specific lesion components; participant-rated confidence in their decisions about the primary outcome; cost effectiveness of follow-up by optometrists rather than ophthalmologists.DiscussionThis trial addresses an important question for the NHS, namely whether, with appropriate training, community optometrists can make retreatment decisions for patients with nAMD to the same standard as hospital ophthalmologists. The trial employed a novel approach as participation was entirely through a web-based application; the trial required very few resources compared with those that would have been needed for a conventional randomised controlled clinical trial

Cost-effectiveness of monitoring glaucoma patients in shared care: an economic evaluation alongside a randomized controlled trial

Background. Population aging increases the number of glaucoma patients which leads to higher workloads of glaucoma specialists. If stable glaucoma patients were monitored by optometrists and ophthalmic technicians in a glaucoma follow-up unit (GFU) rather than by glaucoma specialists, the specialists' workload and waiting lists might be reduced. We compared costs and quality of care at the GFU with those of usual care by glaucoma specialists in the Rotterdam Eye Hospital (REH) in a 30-month randomized clinical trial. Because quality of care turned out to be similar, we focus here on the costs. Methods. Stable glaucoma patients were randomized between the GFU and the glaucoma specialist group. Costs per patient year were calculated from four perspectives: those of patients, the Rotterdam Eye Hospital (REH), Dutch healthcare system, and society. The outcome measures were: compliance to the protocol; patient satisfaction; stability according to the practitioner; mean difference in IOP; results of the examinations; and number of treatment changes. Results. Baseline characteristics (such as age, intraocular pressure and target pressure) were comparable between the GFU group (n = 410) and the glaucoma specialist group (n = 405). Despite a higher number of visits per year, mean hospital costs per patient year were lower in the GFU group (€139 vs. €161). Patients' time and travel costs were similar. Healthcare costs were significantly lower for the GFU group (€230 vs. €251), as were societal costs (€310 vs. €339) (p < 0.01). Bootstrap-, sensitivity- and scenario-analyses showed that the costs were robust when varying hospital policy and the duration of visits and tests. Conclusion. We conclude that this GFU is cost-effective and deserves to be considered for implementation in other hospitals

Tendon Is Covered by a Basement Membrane Epithelium That Is Required for Cell Retention and the Prevention of Adhesion Formation

The ability of tendons to glide smoothly during muscle contraction is impaired after injury by fibrous adhesions that form between the damaged tendon surface and surrounding tissues. To understand how adhesions form we incubated excised tendons in fibrin gels (to mimic the homeostatic environment at the injury site) and assessed cell migration. We noticed cells exiting the tendon from only the cut ends. Furthermore, treatment of the tendon with trypsin resulted in cell extravagation from the shaft of the tendons. Electron microscopy and immunolocalisation studies showed that the tendons are covered by a novel cell layer in which a collagen type IV/laminin basement membrane (BM) overlies a keratinised epithelium. PCR and western blot analyses confirmed the expression of laminin β1 in surface cells, only. To evaluate the cell retentive properties of the BM in vivo we examined the tendons of the Col4a1+/Svc mouse that is heterozygous for a G-to-A transition in the Col4a1 gene that produces a G1064D substitution in the α1(IV) chain of collagen IV. The flexor tendons had a discontinuous BM, developed fibrous adhesions with overlying tissues, and were acellular at sites of adhesion formation. In further experiments, tenotomy of wild-type mice resulted in expression of laminin throughout the adhesion. In conclusion, we show the existence of a novel tendon BM-epithelium that is required to prevent adhesion formation. The Col4a1+/Svc mouse is an effective animal model for studying adhesion formation because of the presence of a structurally-defective collagen type IV-containing BM

Local deformation in a hydrogel induced by an external magnetic field

The aim of this study is to prove the feasibility of a system able to apply local mechanical loading on cells seeded in a hydrogel for tissue engineering applications. This experimental study is based on a previously developed artificial cartilage model with different concentrations of poly(vinyl alcohol) (PVA) that simulates the cartilage extracellular matrix (ECM). Poly(l-lactic acid) (PLLA) microspheres with dispersed magnetic nanoparticles (MNPs) were produced with an emulsion method. These microspheres were embedded in aqueous PVA solutions with varying concentration to resemble increased viscosity of growing tissue during regeneration. The ability to induce a local deformation in the ECM was assessed by applying a steady or an oscillatory magnetic field gradient to different PVA solutions containing the magnetic microparticles, similarly as in ferrogels. PLLA microparticle motion was recorded, and the images were analyzed. Besides, PVA gels and PLLA microparticles were introduced into the pores of a polycaprolactone scaffold, and the microparticle distribution and the mechanical properties of the construct were evaluated. The results of this experimental model show that the dispersion of PLLA microparticles containing MNPs, together with cells in a supporting gel, will allow applying local mechanical stimuli to cells during tissue regeneration. This local stimulation can have a positive effect on the differentiation of seeded cells and improve tissue regeneration.The authors gratefully acknowledge the financial support from the Spanish Ministry of Economy and Competitiveness through the MAT2013-46467-C4-1-R project, including the Feder funds. CIBER-BBN is an initiative funded by the VI National R&D&I Plan 2008-2011, Iniciativa Ingenio 2010, Consolider Program. CIBER Actions are financed by the Instituto de Salud Carlos III with assistance from the European Regional Development Fund. The authors thank "Servicio de Microscopia Electronica" of Universitat Politecnica de Valencia for their invaluable help. The translation of this paper was funded by the Universitat Politecnica de Valencia, Spain.Vikingsson, L.; Vinals Guitart, Á.; Valera Martínez, A.; Riera Guasp, J.; Vidaurre Garayo, AJ.; Gallego Ferrer, G.; Gómez Ribelles, JL. (2016). Local deformation in a hydrogel induced by an external magnetic field. Journal of Materials Science. 51(22):9979-9990. https://doi.org/10.1007/s10853-016-0226-8S997999905122Eyre D (2002) Collagen of articular cartilage. Arthritis Res 4:30–35Roughley PJ, Lee ER (1994) Cartilage proteoglycans: structure and potential functions. Microsc Res Tech 28:385–397Gillard GC, Reilly HC, Bell-Booth PG, Flint MH (1979) The influence of mechanical forces on the glycosaminoglycan content of the rabbit flexor digitorum profundus tendon. Connect Tissue Res 7:37–46Quinn TM, Grodzinsky AJ, Buschmann MD, Kim YJ, Hunziker EB (1998) Mechanical compression alters proteoglycan deposition and matrix deformation around individual cells in cartilage explants. J Cell Sci 111:573–583Banes AJ, Tsuzaki M, Yamamoto J, Fischer T, Brigman B, Brown T, Miller L (1995) Mechanoreception at the cellular level: the detection, interpretation, and diversity of responses to mechanical signals. Biochem Cell Biol 73:349–365Appelman T, Mizrahi J, Elisseeff J, Seliktar D (2011) The influence of biological motifs and dynamic mechanical stimulation in hydrogel scaffold systems on the phenotype of chondrocytes. Biomaterials 32:1508–1516Mow VC, Ratcliffe A, Poole AR (1992) Cartilage and diarthrodial joints as paradigms for hierarchical materials and structures. Biomaterials 13:67–97Mow VC, Huiskes R (2005) Basic orthopaedic biomechanics and mechano-biology. Lippincott Williams and Wilkins, PhiladelphiaBrady MA, Waldman SD, Ethier CR (2015) The application of multiple biophysical cues to engineer functional neocartilage for treatment of osteoarthritis. Part I: cellular response. Tissue Eng Part B Rev 21:1–19Valhmu WB, Stazzone EJ, Bachrach NM, Saed-Nejad F, Fischer SG, Mow VC, Ratcliffe A (1998) Load-controlled compression of articular cartilage induces a transient stimulation of aggrecan gene expression. Arch Biochem Biophys 353:29–36Ingber DE (1997) Tensegrity: the architectural basis of cellular mechanotransduction. Ann Rev Physiol 59:575–599Khan S, Sheetz MP (1997) Force effects on biochemical kinetics. Ann Rev Biochem 66:785–805Hutmacher DW (2000) Scaffolds in tissue engineering bone and cartilage. Biomaterials 21:2529–2543Crick FHC, Hughes AFW (1950) The physical properties of cytoplasm: a study by means of the magnetic particle method. Exp Cell Res 1:37–80Valberg PA, Albertini DF (1985) Cytoplasmic motions, rheology, and structure probed by a novel magnetic particle method. J Cell Biol 101:130–140Valberg PA, Feldman HA (1987) Magnetic particle motions within living cells. Measurement of cytoplasmic viscosity and motile activity. Biophys J 52:551–561Wang N, Ingber DE (1995) Probing transmembrane mechanical coupling and cytomechanics using magnetic twisting cytometry. Biochem Cell Biol 73:327–335Pommerenke H, Schreiber E, Durr F, Nebe B, Hahnel C, Moller W, Rychly J (1996) Stimulation of integrin receptors using a magnetic drag force device induces an intracellular free calcium response. Eur J Cell Biol 70:157–164Bausch AR, Hellerer U, Essler M, Aepfelbacher M, Sackmann E (2001) Rapid stiffening of integrin receptor-actin linkages in endothelial cells stimulated with thrombin: a magnetic bead microrheology study. Biophys J 80:2649–2657Li L, Yang G, Li J, Ding S, Zhou S (2014) Cell behaviors on magnetic electrospun poly-d, l-lactide nano fibers. Mater Sci Eng, C 34:252–261Fuhrer R, Hofmann S, Hild N, Vetsch JR, Herrmann IK, Grass RN, Stark WJ (2013) Pressureless mechanical induction of stem cell differentiation is dose and frequency dependent. PLoS One 8:e81362Cezar CA, Roche ET, Vandenburgh HH, Duda GN, Walsh CJ, Mooney DJ (2016) Biologic-free mechanically induced muscle regeneration. Proc Natl Acad Sci USA 113:1534–1539Vikingsson L, Gallego Ferrer G, Gómez-Tejedor JA, Gómez Ribelles JL (2014) An in vitro experimental model to predict the mechanical behaviour of macroporous scaffolds implanted in articular cartilage. J Mech Behav Biomed Mater 32:125–131Vikingsson L, Gomez-Tejedor JA, Gallego Ferrer G, Gomez Ribelles JL (2015) An experimental fatigue study of a porous scaffold for the regeneration of articular cartilage. J Biomech 48:1310–1317Vikingsson L, Claessens B, Gómez-Tejedor JA, Gallego Ferrer G, Gómez Ribelles JL (2015) Relationship between micro-porosity, water permeability and mechanical behavior in scaffolds for cartilage engineering. J Mech Behav Biomed Mater 48:60–69Li F, Su YL, Shi DF, Wang CT (2010) Comparison of human articular cartilage and polyvinyl alcohol hydrogel as artificial cartilage in microstructure analysis and unconfined compression. Adv Mater Res Trans Tech Publ 87:188–193Grant C, Twigg P, Egan A, Moody A, Eagland D, Crowther N, Britland S (2006) Poly(vinyl alcohol) hydrogel as a biocompatible viscoelastic mimetic for articular cartilage. Biotechnol Prog 22:1400–1406Weeber R, Kantorovich S, Holm C (2015) Ferrogels cross-linked by magnetic nanoparticles—Deformation mechanisms in two and three dimensions studied by means of computer simulations. J Magn Magn Mater 383:262–266Lebourg M, Suay Antón J, Gómez Ribelles JL (2008) Porous membranes of PLLA–PCL blend for tissue engineering applications. Eur Polym J 44:2207–2218Santamaría VA, Deplaine H, Mariggió D, Villanueva-Molines AR, García-Aznar JM, Gómez Ribelles JL, Doblaré M, Gallego Ferrer G, Ochoa I (2012) Influence of the macro and micro-porous structure on the mechanical behavior of poly (l-lactic acid) scaffolds. J Non Cryst Solids 358:3141–3149Panadero JA, Vikingsson L, Gomez Ribelles JL, Lanceros-Mendez S, Sencadas V (2015) In vitro mechanical fatigue behaviour of poly-ε-caprolactone macroporous scaffolds for cartilage tissue engineering. Influence of pore filling by a poly(vinyl alcohol) gel. J Biomed Mater Res Part B Appl Biomater 103:1037–1043Hassan CM, Peppas NA (2000) Structure and applications of poly(vinyl alcohol) hydrogels produced by conventional crosslinking or by freezing/thawing methods. Adv Polym Sci 153:37–65Labet M, Thielemans W (2009) Synthesis of polycaprolactone: a review. Chem Soc Rev 38:3484–3504Mano JF, Gómez Ribelles JL, Alves NM, Salmerón Sanchez M (2005) Glass transition dynamics and structural relaxation of PLLA studied by DSC: influence of crystallinity. Polymer 46:8258–8265Eckstein F, Lemberger B, Gratzke C, Hudelmaier M, Glaser C, Englmeier KH, Reiser M (2005) In vivo cartilage deformation after different types of activity and its dependence on physical training status. Ann Rheum Dis 64:291–295Garlotta D (2001) A literature review of poly(lactic acid). J Polym Eng 9:63–84Kovacs AJ, Aklonis JJ, Hutchinson JM, Ramos AR (1979) Isobaric volume and enthalpy recovery of glasses. II. A transparent multiparameter theory. J Polym Sci Polym Phys 17:1097–1162Hernández F, Molina Mateo J, Romero Colomer F, Salmerón Sánchez M, Gómez Ribelles JL, Mano J (2005) Influence of low-temperature nucleation on the crystallization process of poly(l-lactide). Biomacromolecules 6:3291–3299Wang Y, Gómez Ribelles JL, Salmerón Sánchez M, Mano JF (2005) Morphological contribution to glass transition in poly(l-lactic acid). Macromolecules 38:4712–4718Salmerón Sánchez M, Vincent BM, Vanden Poel G, Gómez-Ribelles JL (2007) Effect of the cooling rate on the nucleation kinetics of poly(l-lactic acid) and its influence on morphology. Macromolecules 40:7989–7997Nobuyuki O (1975) A threshold selection method from gray-level histograms. Automatica 11:23–2

An Overview of the Management of Flexor Tendon Injuries

Flexor tendon injuries still remain a challenging condition to manage to ensure optimal outcome for the patient. Since the first flexor tendon repair was described by Kirchmayr in 1917, several approaches to flexor tendon injury have enabled successful repairs rates of 70-90%. Primary surgical repair results in better functional outcome compared to secondary repair or tendon graft surgery. Flexor tendon injury repair has been extensively researched and the literature demonstrates successful repair requires minimal gapping at the repair site or interference with tendon vascularity, secure suture knots, smooth junction of tendon end and having sufficient strength for healing. However, the exact surgical approach to achieve success being currently used among surgeons is still controversial. Therefore, this review aims to discuss the results of studies demonstrating the current knowledge regarding the optimal approach for flexor tendon repair. Post-operative rehabilitation for flexor tendon surgery is another area, which has caused extensive debate in hand surgery. The trend to more active mobilisation protocols seems to be favoured but further study in this area is needed to find the protocol, which achieves function and gliding but avoids rupture of the tendons. Lastly despite success following surgery complications commonly still occur post surgery, including adhesion formation, tendon rupture and stiffness of the joints. Therefore, this review aims to discuss the appropriate management of these difficulties post surgery. New techniques in management of flexor tendon will also be discussed including external laser devices, addition of growth factors and cytokines