XinuPi3: Teaching Multicore Concepts Using Embedded Xinu

As computer platforms become more advanced, the need to teach advanced computing concepts grows accordingly. This paper addresses one such need by presenting XinuPi3, a port of the lightweight instructional operating system Embedded Xinu to the Raspberry Pi 3. The Raspberry Pi 3 improves upon previous generations of inexpensive, credit card-sized computers by including a quad-core, ARM-based processor, opening the door for educators to demonstrate essential aspects of modern computing like inter-core communication and genuine concurrency. Embedded Xinu has proven to be an effective teaching tool for demonstrating low-level concepts on single-core platforms, and it is currently used to teach a range of systems courses at multiple universities. As of this writing, no other bare metal educational operating system supports multicore computing. XinuPi3 provides a suitable learning environment for beginners on genuinely concurrent hardware. This paper provides an overview of the key features of the XinuPi3 system, as well as the novel embedded system education experiences it makes possible

Using Embedded Xinu and the Raspberry Pi 3 to Teach Operating Systems

Multicore processors have become the standard in modern computing platforms. Such complex hardware enables faster execution of the programs it runs, but this is only true if its programmer has the knowledge and ability to make it so. Thus, there is a great need to prepare computing students by establishing robust educational tools. Existing tools often include abstract learning environments such as a virtual machine. While such platforms are widely available and convenient, they are unable to expose students to concurrency on real hardware.This paper presents multicore Embedded Xinu, an educational operating system used to teach concurrency concepts at the university level. The latest port of Embedded Xinu to the four-core, ARM-based Raspberry Pi 3 B+ enabled an operating systems curriculum in which students build their own concurrency-oriented kernel and execute it on a real machine. Assignments that have been run in the course include concepts of synchronization, scheduling, and memory allocation on a multicore platform. Upon completing the course, students are capable of solving problems commonly found in the field of parallel computing

Diol Dehydratase: Purification, Structural Characterization, and Mechanism of Action

Abstract to Chapter I A new isolation procedure for propanediol dehydratase increases by a factor of about 16 the yield of enzyme obtainable from Klebsiella pneumoniae; the enzyme thus isolated has a specific activity of 95 ± 4 units/mg. The apoenzyme consists of four different subunits with molecular weights of 60 K, 51 K, 29 K, and 15 K daltons in the ratio of 2:1:2:2, respectively. In this new procedure, care was taken to prevent the partial proteolysis of the propanediol dehydratase which seems to occur in earlier procedures. The other novel aspect recognizes that the enzyme is associated with the cell membrane. Accordingly, after gentle sonication, the membrane fragments are separated from cytosol, and the enzyme is solubilized by extraction with buffers containing detergent. The amino acid compositions and N-terminal amino acid sequences for each of the subunits was also determined. From the amino acid compositions of the individual subunits, diol dehydratase appears to be a peripheral membrane protein. Abstract to Chapter II When diol dehydratase holoenzyme is inactivated by reaction with radioactive glycerol, one mole of glycerol appears to become tightly associated with each 250,000 daltons of the holoenzyme complex with a significant loss of tritium from C-2 being observed. However, denaturation of the inactivated complex releases the modified glycerol from the protein, indicating that the protein is not covalently modified by the inactivator. Similar experiments were carried out with radioactive isobutylene glycol, but due to the high level of nonspecific labeling, the results were not as definitive. As described in Chapter I, former isolation procedures (Abeles, 1966; Poznanskaya et al., 1979) yielded enzyme which had been proteolysed. For this reason inactivation studies employing various deuterated derivatives of glycerol and isobutylene glycol, as well as a new class of inactivators represented by hydroxyacetone and dihydroxyacetone, were carried out with native enzyme to compare results from similar studies with proteolysed enzyme (Bachovchin et al., 1977; Moore, 1979). It was found that proteolysis had little effect on the constants associated with the glycerol inactivation, but an enormous effect on the constants describing the inactivation by isobutylene glycol. The results of the radiolabeling studies and kinetic experiments are consistent with the formation of a secondary alkylcobalamin upon inactivation of diol dehydratase by glycerol. Kinetic evidence also suggests that the inactivation of diol dehydratase by isobutylene glycol occurs after the abstraction of hydrogen from C-1, but before the substrate rearranges. Abstract to Chapter III A reinvestigation of trace label experiments with native diol dehydratase isolated by the method of McGee and Richards (1981) (see Chapter I) has shown that the probability of net intramolecular transfer for tritium is 0.33 ± 0.02 as opposed to the value of about 0.03 obtained earlier (Frey et al., 1967a) with an enzyme preparation obtained by a different method. Our observed value of 0.33 is about 20 times larger than what one would predict on the basis of the mechanism for the migration of hydrogen given in the Introduction to this thesis. In contrast, tritium washout experiments, similar to those conducted by Essenberg et al. (1971), yielded a value of kHH/kHT = 29 ± 2 which is approximately the value predicted by Moore et al. (1979). Also, tritium washout experiments were carried out in such a way that, in addition to the C-5' hydrogens of adenosylcobalamin containing tritium, any other multiple-hydrogen reservoirs should have contained tritium as well. These experiments yielded identical results to those in which only the C-5' hydrogens contained reactable tritium; therefore, it appears that only the C-5' hydrogens of C-5' deoxyadenosine participate directly in catalysis. Also, the tritium isotope effect on the first hydrogen transfer was determined to be 6.1 ± 0.5 by measuring the isotopic enrichment in unreacted [1-3H]-1,2-propanediol as a function of the extent of reaction. The results of our study suggest that the generally accepted pathway for catalysis, which proceeds through the C-5' deoxyadenosine hydrogen reservoir, constitutes about 95% of the catalytic events with unlabeled substrate; however, there appears to be an alternate catalytic pathway whose contribution to catalysis can be enhanced by isotopic substitution at C-1 of substrate.</p

Electrochemical sensors, MTT and immunofluorescence assays for monitoring the proliferation effects of cissus populnea extracts on Sertoli cells

<p>Abstract</p> <p>Background</p> <p>We describe the development of an electrochemical sensor array for monitoring the proliferation effects of cissus populnea plant extracts on TM4 Sertoli cells.</p> <p>Methods</p> <p>The proliferation activities of the extracts on Sertoli cells were studied using a high-throughput electrochemical sensor array (DOX-96) and the analytical sensor characteristics were compared with conventional colorimetric MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay and fluorescence spectroscopy.</p> <p>Results</p> <p>This work shows that there is a definite positive trend in the proliferation effect of the extract of <it>Cissus populnea </it>on the TM4 Sertoli cells. All of the three techniques confirmed that the most effective concentration for the proliferation is 10 ppm. At this concentration, the proliferation effect was established around 120% for both DOX-96 and MTT techniques, whereas fluorescence assays showed a higher level (120-150%). DOX-96 showed a lower limit of detection (1.25 × 10(4) cells/ml); whereas the LOD recorded for both MTT and fluorescence techniques was 2.5 × 10(4) cells/ml. Visual examination of the cells by means of confocal fluorescence microscopy confirmed the proliferation of Sertoli cells as was determined using the MTT assay. This investigation provides a confident interpretation of the results and proved that the most effective concentration for the proliferation using <it>Cissus populnea </it>plant extract is 10 ppm.</p> <p>Conclusions</p> <p>Overall, the DOX results compared well with the conventional methods of checking proliferation of cells. The fascinating feature of the sensor array is the ability to provide continuous proliferation experiments with no additional reagents including 96 simultaneous electrochemical experiments. The use of the DOX-96 could reduce a typical bioassay time by 20-fold. Thus the DOX-96 can be used as both a research tool and for practical cell culture monitoring.</p

Equal Outcomes 4 All: A Study of Student Learning in ECS

This study investigated patterns in the development of computational thinking practices in the context of the Exploring Computer Science (ECS) program, a high school introductory CS course and professional development program designed to foster deep engagement through equitable inquiry around CS concepts. Past research indicates that the personal relevance of the ECS experience influences students\u27 expectancy-value towards computer science. Expectancy-value is a construct that is predictive of career choices. We extended our research to examine whether expectancy-value influences the development of computational thinking practices. This study took place in the context of two ECS implementation projects across two states. Twenty teachers, who implemented ECS in 2016-17, participated in the research. There were 906 students who completed beginning and end of year surveys and assessments. The surveys included demographic questions, a validated expectancy-value scale, and questions about students\u27 course experiences. The assessments were developed and validated by SRI International as a companion to the ECS course. Overall, student performance statistically increased from pretest to posttest with effect size of 0.74. There were no statistically significant differences in performance by gender or race/ethnicity. These results are consistent with earlier findings that a personally relevant course experience positively influences students\u27 expectancy for success. These results expanded on prior research by indicating that students\u27 expectancy-value for computer science positively influenced student learning

Spirituality, Faith, and Mild Alzheimer\u27s Disease

There is some evidence for a positive association between spirituality, cognitive, and behavioral functioning in people with Alzheimer’s disease (AD). However, to our knowledge there is no published data to date that provides an explanatory model for these findings. Twenty-eight individuals with mild AD received in-depth interviews and measures of cognitive, behavioral, emotional, and spiritual functioning to gain insight into this question in this mixed methods study. Findings revealed that people with mild AD can actively engage in meaningful discussion about how spirituality influences their experience of living with AD; that they remain deeply devoted to a relationship with the transcendent (i.e., God, higher power, spirit) and their spiritual communities; that they value and benefit from the sacred aspects of their day-to-day lives; and that their core spiritual values, beliefs, and practices can be activated to help them adapt to the uncertainty of living with AD. Additionally, persons with AD who are experiencing spiritual struggle tend to experience a greater degree of anxiety, depression, and behavioral changes as compared to those who do not, suggesting that spiritual struggle is a risk factor for poorer outcomes in this population. Implications for future research, clinical practice, and community care are provided including how researchers and clinicians can effectively adapt traditional measures of spirituality for use with this population; the importance of integrating spirituality into the assessment and treatment of people with AD; and the role spiritual communitie

The Multi-Epoch Nearby Cluster Survey: type Ia supernova rate measurement in z~0.1 clusters and the late-time delay time distribution

We describe the Multi-Epoch Nearby Cluster Survey (MENeaCS), designed to measure the cluster Type Ia supernova (SN Ia) rate in a sample of 57 X-ray selected galaxy clusters, with redshifts of 0.05 < z < 0.15. Utilizing our real time analysis pipeline, we spectroscopically confirmed twenty-three cluster SN Ia, four of which were intracluster events. Using our deep CFHT/Megacam imaging, we measured total stellar luminosities in each of our galaxy clusters, and we performed detailed supernova detection efficiency simulations. Bringing these ingredients together, we measure an overall cluster SN Ia rate within R_{200} (1 Mpc) of 0.042^{+0.012}_{-0.010}^{+0.010}_{-0.008} SNuM (0.049^{+0.016}_{-0.014}^{+0.005}_{-0.004} SNuM) and a SN Ia rate within red sequence galaxies of 0.041^{+0.015}_{-0.015}^{+0.005}_{-0.010} SNuM (0.041^{+0.019}_{-0.015}^{+0.005}_{-0.004} SNuM). The red sequence SN Ia rate is consistent with published rates in early type/elliptical galaxies in the `field'. Using our red sequence SN Ia rate, and other cluster SNe measurements in early type galaxies up to $z\sim1$, we derive the late time (>2 Gyr) delay time distribution (DTD) of SN Ia assuming a cluster early type galaxy star formation epoch of z_f=3. Assuming a power law form for the DTD, \Psi(t)\propto t^s, we find s=-1.62\pm0.54. This result is consistent with predictions for the double degenerate SN Ia progenitor scenario (s\sim-1), and is also in line with recent calculations for the double detonation explosion mechanism (s\sim-2). The most recent calculations of the single degenerate scenario delay time distribution predicts an order of magnitude drop off in SN Ia rate \sim 6-7 Gyr after stellar formation, and the observed cluster rates cannot rule this out.Comment: 35 pages, 14 figures, ApJ accepte

Intracluster supernovae in the Multi-epoch Nearby Cluster Survey

The Multi-Epoch Nearby Cluster Survey (MENeaCS) has discovered twenty-three cluster Type Ia supernovae (SNe) in the 58 X-ray selected galaxy clusters (0.05 < z < 0.15) surveyed. Four of our SN Ia events have no host galaxy on close inspection, and are likely intracluster SNe. Deep image stacks at the location of the candidate intracluster SNe put upper limits on the luminosities of faint hosts, with M_{r} > -13.0 mag and M_{g} > -12.5 mag in all cases. For such limits, the fraction of the cluster luminosity in faint dwarfs below our detection limit is <0.1%, assuming a standard cluster luminosity function. All four events occurred within ~600 kpc of the cluster center (projected), as defined by the position of the brightest cluster galaxy, and are more centrally concentrated than the cluster SN Ia population as a whole. After accounting for several observational biases that make intracluster SNe easier to discover and spectroscopically confirm, we calculate an intracluster stellar mass fraction of 0.16^{+0.13}_{-0.09} (68% CL) for all objects within R_{200}. If we assume that the intracluster stellar population is exclusively old, and the cluster galaxies themselves have a mix of stellar ages, we derive an upper limit on the intracluster stellar mass fraction of <0.47 (84% one-sided CL). When combined with the intragroup SNe results of McGee & Balogh, we confirm the declining intracluster stellar mass fraction as a function of halo mass reported by Gonzalez and collaborators. (Abridged)Comment: 24 pages, 8 figures, ApJ publishe