Power Efficient Restart-Capable Acrylonitrile Butadiene Styrene-Based Arc Ignition for Hybrid Rocket Motors

Hybrid rocket ignition has historically involved either dangerous energetic materials or inefficient and failure-prone plasma sources. The vast majority of such systems cannot sup- port multiple restart cycles, thus limiting the applicability of hybrid rockets–especially for in-space propulsion. During research investigating its use as a fuel for hybrid rockets, it was discovered that Acrylonitrile Butadiene Styrene (ABS) plastic possesses unique electrical breakdown characteristics. During a properly designed breakdown event, application of a strong electric field induces a high-temperature arc along the surface of the ABS, concurrent with rapid production of hydrocarbon vapor. This behavior forms the basis of a novel ABS arc ignition system. Several such systems were designed, built and tested. Minimum conditions for successful operation were discovered, including minimum ignition pressure and electrical power requirements. Hands-off restart capability was demonstrated repeatedly. Finally, paths of inquiry for future research are outlined

Imail: a DBMS for electronic mail

Call number: LD2668 .R4 CMSC 1988 I55Master of ScienceComputing and Information Science

No influence of eye gaze on emotional face processing in the absence of conscious awareness

The human brain has evolved specialised mechanisms to enable the rapid detection of threat cues, including emotional face expressions (e.g., fear and anger). However, contextual cues – such as gaze direction – influence the ability to recognise emotional expressions. For instance, anger paired with direct gaze, and fear paired with averted gaze are more accurately recognised compared to alternate conjunctions of these features. It is argued that this is because gaze direction conveys the relevance and locus of the threat to the observer. Here, we used continuous flash suppression (CFS) to assess whether the modulatory effect of gaze direction on emotional face processing occurs outside of conscious awareness. Previous research using CFS has demonstrated that fearful facial expressions are prioritised by the visual system and gain privileged access to awareness over other expressed emotions. We hypothesised that if the modulatory effects of gaze on emotional face processing occur also at this level, then the gaze-emotion conjunctions signalling self-relevant threat will reach awareness faster than those that do not. We report that fearful faces gain privileged access to awareness over angry faces, but that gaze direction does not modulate this effect. Thus, our findings suggest that previously reported effects of gaze direction on emotional face processing are likely to occur once the face is detected, where the self-relevance and locus of the threat can be consciously appraised

Assisted Cough and Pulmonary Compliance in Patients with Duchenne Muscular Dystrophy

The aim of this study was to investigate the factors affecting cough ability, and to compare the assisted cough methods in patients with Duchenne muscular dystrophy (DMD). A total seventy-one male patients with DMD were included in the study. The vital capacity (VC) and maximum insufflation capacity (MIC) were measured. The unassisted peak cough flow (UPCF) and three different techniques of assisted peak cough flow were evaluated. UPCF measurements were possible for all 71 subjects. But when performing the three different assisted cough techniques, peak cough flows (PCFs) could be obtained from only 51 subjects. The mean value of MICs (1801 ± 780 cc) was higher than that of VCs (1502 ± 765 cc) (p < 0.01). All three assisted cough methods showed a significantly higher value than the unassisted method (F=80.92, p < 0.01). The manual assisted PCF under MIC (MPCFmic) significantly exceeded those produced by manual assisted PCF (MPCF) or PCF under MIC (PCFmic). The positive correlation between the MIC, VC difference (MIC-VC), and the difference between PCFmic and UPCF (PCFmic-UPCF) was seen (r=0.572, p < 0.01). The preservation of pulmonary compliance is important for the development of an effective cough as well as assisting the compression and expulsive phases. Thus, the clinical importance of the inspiratory phase and pulmonary compliance in assisting a cough should be emphasized

How Respiratory Muscle Strength Correlates with Cough Capacity in Patients with Respiratory Muscle Weakness

PURPOSE: The purpose of this study is to investigate how respiratory muscle strength correlates to cough capacity in patients with respiratory muscle weakness. MATERIALS AND METHODS: Forty-five patients with amyotrophic lateral sclerosis (ALS), 43 with cervical spinal cord injury (SCI), and 42 with Duchenne muscular dystrophy (DMD) were recruited. Pulmonary function tests including forced vital capacity (FVC) and respiratory muscle strength (maximal expiratory pressure, MEP; maximal inspiratory pressure, MIP) were performed. The correlation between respiratory muscle strength and cough capacity was analyzed. RESULTS: In the SCI group, FVC in a supine position (2,597 +/- 648 mL) was significantly higher than FVC in a sitting position (2,304 +/- 564 mL, p < 0.01). Conversely, in the ALS group, FVC sitting (1,370 +/- 604 mL) was significantly higher than in supine (1,168 +/- 599 mL, p < 0.01). In the DMD group, there was no statistically significant difference between FVC while sitting (1,342 +/- 506 mL) and FVC while supine (1,304 +/- 500 mL). In addition, the MEP and MIP of all three groups showed a significant correlation with peak cough flow (PCF) (p < 0.01, Pearson's correlation analysis). In the SCI group, MIP was more closely correlated with PCF, while in the ALS and DMD groups, MEP was more closely correlated with PCF (p < 0.01, multiple regression analysis). CONCLUSION: To generate cough flow, inspiratory muscle strength is significantly more important for SCI patients, while expiratory muscle function is significantly more important for ALS and DMD patients.ope

Respiratory Muscle Strength and Cough Capacity in Patients with Duchenne Muscular Dystrophy

The function of inspiratory muscles is crucial for effective cough as well as expiratory muscles in patients with Duchenne muscular dystrophy (DMD). However, there is no report on the correlation between cough and inspiratory muscle strength. To investigate the relationships of voluntary cough capacity, assisted cough techniques, and inspiratory muscle strength as well as expiratory muscle strength in patients with DMD (n = 32). The vital capacity (VC), maximum insufflation capacity (MIC), maximal inspiratory pressure (MIP), and maximal expiratory pressure (MEP) were measured. Unassisted peak cough flow (UPCF) and three different techniques of assisted PCF were evaluated. The mean value of MICs (1918 ± 586 mL) was higher than that of VCs (1474 ± 632 mL) (p < 0.001). All three assisted cough methods showed significantly higher value than unassisted method (212 ± 52 L/min) (F = 66.13, p < 0.001). Combined assisted cough technique (both manual and volume assisted PCF; 286 ± 41 L/min) significantly exceeded manual assisted PCF (MPCF; 246 ± 49 L/min) and volume assisted PCF (VPCF; 252 ± 45 L/min) (F = 66.13, p < 0.001). MIP (34 ± 13 cmH2O) correlated significantly with both UPCF and all three assisted PCFs as well as MEP (27 ± 10 cmH2O) (p < 0.001). Both MEP and MIP, which are the markers of respiratory muscle weakness, should be taken into account in the study of cough effectiveness

Autistic young people adaptively use gaze to facilitate joint attention during multi-gestural dyadic interactions

Autistic people often experience difficulties navigating face-to-face social interactions. Historically, the empirical literature has characterised these difficulties as cognitive ‘deficits’ in social information processing. However, the empirical basis for such claims is lacking, with most studies failing to capture the complexity of social interactions, often distilling them into singular communicative modalities (e.g. gaze-based communication) that are rarely used in isolation in daily interactions. The current study examined how gaze was used in concert with communicative hand gestures during joint attention interactions. We employed an immersive virtual reality paradigm, where autistic (n = 22) and non-autistic (n = 22) young people completed a collaborative task with a non-autistic confederate. Integrated eye-, head- and hand-motion-tracking enabled dyads to communicate naturally with each other while offering objective measures of attention and behaviour. Autistic people in our sample were similarly, if not more, effective in responding to hand-cued joint attention bids compared with non-autistic people. Moreover, both autistic and non-autistic people demonstrated an ability to adaptively use gaze information to aid coordination. Our findings suggest that the intersecting fields of autism and social neuroscience research may have overstated the role of eye gaze during coordinated social interactions. Lay abstract: Autistic people have been said to have ‘problems’ with joint attention, that is, looking where someone else is looking. Past studies of joint attention have used tasks that require autistic people to continuously look at and respond to eye-gaze cues. But joint attention can also be done using other social cues, like pointing. This study looked at whether autistic and non-autistic young people use another person’s eye gaze during joint attention in a task that did not require them to look at their partner’s face. In the task, each participant worked together with their partner to find a computer-generated object in virtual reality. Sometimes the participant had to help guide their partner to the object, and other times, they followed their partner’s lead. Participants were told to point to guide one another but were not told to use eye gaze. Both autistic and non-autistic participants often looked at their partner’s face during joint attention interactions and were faster to respond to their partner’s hand-pointing when the partner also looked at the object before pointing. This shows that autistic people can and do use information from another person’s eyes, even when they don’t have to. It is possible that, by not forcing autistic young people to look at their partner’s face and eyes, they were better able to gather information from their partner’s face when needed, without being overwhelmed. This shows how important it is to design tasks that provide autistic people with opportunities to show what they can do

Chronic Hypoxia Impairs Muscle Function in the Drosophila Model of Duchenne's Muscular Dystrophy (DMD)

Duchenne's muscular dystrophy (DMD) is a severe progressive myopathy caused by mutations in the DMD gene leading to a deficiency of the dystrophin protein. Due to ongoing muscle necrosis in respiratory muscles late-stage DMD is associated with respiratory insufficiency and chronic hypoxia (CH). To understand the effects of CH on dystrophin-deficient muscle in vivo, we exposed the Drosophila model for DMD (dmDys) to CH during a 16-day ascent to the summit of Mount Denali/McKinley (6194 meters above sea level). Additionally, dmDys and wild type (WT) flies were also exposed to CH in laboratory simulations of high altitude hypoxia. Expression profiling was performed using Affymetrix GeneChips® and validated using qPCR. Hypoxic dmDys differentially expressed 1281 genes, whereas the hypoxic WT flies differentially expressed 56 genes. Interestingly, a number of genes (e.g. heat shock proteins) were discordantly regulated in response to CH between dmDys and WT. We tested the possibility that the disparate molecular responses of dystrophin-deficient tissues to CH could adversely affect muscle by performing functional assays in vivo. Normoxic and CH WT and dmDys flies were challenged with acute hypoxia and time-to-recover determined as well as subjected to climbing tests. Impaired performance was noted for CH-dmDys compared to normoxic dmDys or WT flies (rank order: Normoxic-WT ≈ CH-WT> Normoxic-dmDys> CH-dmDys). These data suggest that dystrophin-deficiency is associated with a disparate, pathological hypoxic stress response(s) and is more sensitive to hypoxia induced muscle dysfunction in vivo. We hypothesize that targeting/correcting the disparate molecular response(s) to hypoxia may offer a novel therapeutic strategy in DMD

Arginine Metabolism by Macrophages Promotes Cardiac and Muscle Fibrosis in mdx Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is the most common, lethal disease of childhood. One of 3500 new-born males suffers from this universally-lethal disease. Other than the use of corticosteroids, little is available to affect the relentless progress of the disease, leading many families to use dietary supplements in hopes of reducing the progression or severity of muscle wasting. Arginine is commonly used as a dietary supplement and its use has been reported to have beneficial effects following short-term administration to mdx mice, a genetic model of DMD. However, the long-term effects of arginine supplementation are unknown. This lack of knowledge about the long-term effects of increased arginine metabolism is important because elevated arginine metabolism can increase tissue fibrosis, and increased fibrosis of skeletal muscles and the heart is an important and potentially life-threatening feature of DMD.We use both genetic and nutritional manipulations to test whether changes in arginase metabolism promote fibrosis and increase pathology in mdx mice. Our findings show that fibrotic lesions in mdx muscle are enriched with arginase-2-expressing macrophages and that muscle macrophages stimulated with cytokines that activate the M2 phenotype show elevated arginase activity and expression. We generated a line of arginase-2-null mutant mdx mice and found that the mutation reduced fibrosis in muscles of 18-month-old mdx mice, and reduced kyphosis that is attributable to muscle fibrosis. We also observed that dietary supplementation with arginine for 17-months increased mdx muscle fibrosis. In contrast, arginine-2 mutation did not reduce cardiac fibrosis or affect cardiac function assessed by echocardiography, although 17-months of dietary supplementation with arginine increased cardiac fibrosis. Long-term arginine treatments did not decrease matrix metalloproteinase-2 or -9 or increase the expression of utrophin, which have been reported as beneficial effects of short-term treatments.Our findings demonstrate that arginine metabolism by arginase promotes fibrosis of muscle in muscular dystrophy and contributes to kyphosis. Our findings also show that long-term, dietary supplementation with arginine exacerbates fibrosis of dystrophic heart and muscles. Thus, commonly-practiced dietary supplementation with arginine by DMD patients has potential risk for increasing pathology when performed for long periods, despite reports of benefits acquired with short-term supplementation

Neuronal Nitric Oxide Synthase-Rescue of Dystrophin/Utrophin Double Knockout Mice does not Require nNOS Localization to the Cell Membrane

Survival of dystrophin/utrophin double-knockout (dko) mice was increased by muscle-specific expression of a neuronal nitric oxide synthase (nNOS) transgene. Dko mice expressing the transgene (nNOS TG+/dko) experienced delayed onset of mortality and increased life-span. The nNOS TG+/dko mice demonstrated a significant decrease in the concentration of CD163+, M2c macrophages that can express arginase and promote fibrosis. The decrease in M2c macrophages was associated with a significant reduction in fibrosis of heart, diaphragm and hindlimb muscles of nNOS TG+/dko mice. The nNOS transgene had no effect on the concentration of cytolytic, CD68+, M1 macrophages. Accordingly, we did not observe any change in the extent of muscle fiber lysis in the nNOS TG+/dko mice. These findings show that nNOS/NO (nitric oxide)-mediated decreases in M2c macrophages lead to a reduction in the muscle fibrosis that is associated with increased mortality in mice lacking dystrophin and utrophin. Interestingly, the dramatic and beneficial effects of the nNOS transgene were not attributable to localization of nNOS protein at the cell membrane. We did not detect any nNOS protein at the sarcolemma in nNOS TG+/dko muscles. This important observation shows that sarcolemmal localization is not necessary for nNOS to have beneficial effects in dystrophic tissue and the presence of nNOS in the cytosol of dystrophic muscle fibers can ameliorate the pathology and most importantly, significantly increase life-span