Long gone are the days when you could use a logic analyser on a CPU to find out what it is executing. Caches, out-of-order memory accesses and especially multi-processing all effectively hide the sequence of instructions that the CPU is working on. Traditional debug techniques with breakpoints and single-stepping help, but require interactive sessions at human rates rather than the gigahertz rates of today's processors. To help this situation, many of today's sophisticated processors come with a side-port (e.g. BDM, ETM, Nexus or Aurora) that the CPU can use to communicate what it is doing in real-time, at its full rate. By using a debug probe to capture this stream of information, the activities of the CPU can be traced. This trace data can be post-analysed to determine what the processor did, and even what memory values were processed. The problem is that at gigahertz processing speeds, that's many gigabytes of data every second: what techniques are available to help understand this firehose of data? This trace data is one-dimensional: linear over time. So if a programming bug occurred during the trace capture, it is possible to see the sequence of steps leading up to it. Indeed, it is also possible to work backwards through the data looking for the exact condition that started the bug. The data is also suitable for use in profiling and coverage analysis: how often or whether certain routines were executed, and how long they took - all without instrumenting the code by adding time-wasting in-band profiling code, or by using statistical sampling techniques. Useful as this is, even more information can be gleaned by adding a second dimension: depth. More for optimising code than debugging it, being able to analyse call stacks can give insights into the (perhaps unexpected) way that the code base functions. However, to see code two-dimensionally requires a different view from the traditional source-based one: a graphical view, one that represents the call stack over time. This article explores these techniques, and explains how, through visualisation, the way a system is working (or not) can be more fully understood. Real-life examples of how using trace data helped debugging are also provided.

Natural convection in a spherical geometry is considered for prediction of the buoyancy of single- and double-walled balloons in a cryogenic environment such as Titan’s atmosphere. The steady-state flow characteristics obtained by solving the Reynolds-averaged Navier–Stokes equations with a standard turbulence model are used to determine the net buoyancy as a function of heat input. Thermal radiation effects are shown to have a minor impact on the buoyancy, as would be expected at cryogenic conditions. The predicted buoyancy and temperature fields compare favorably with experiments preformed on a 1-m-diameter Montgolfiere prototype in a cryogenic facility. In addition, both numerical and experimental results were compared with correlations for the heat transfer coefficients for free convection internal and external to the balloon as well as in the concentric gap of the double-walled balloons. Finally, scaling issues related to inferring the performance of the full-scale Montgolfiere from the model-scale results are examined.

Computational models are developed to predict the natural convection heat transfer and buoyancy for a Montgolfiere under conditions relevant to the Titan atmosphere. Idealized single and double-walled balloon geometries are simulated using algorithms suitable for both laminar and (averaged) turbulent convection. Steady-state performance results are compared to existing heat transfer coefficient correlations. The laminar results, in particular, are used to test the validity of the correlations in the absence of uncertainties associated with turbulence modeling. Some discrepancies are observed, especially for convection in the gap, and appear to be primarily associated with temperature nonuniformity on the balloon surface. The predicted buoyancy for the single-walled balloon in the turbulent convection regime, predicted with a standard k ǫ turbulence model, was within 10% of predictions based on the empirical correlations. There was also good agreement with recently conducted experiments in a cryogenic facility designed to simulate the Titan atmosphere.

A previous study of histone H3 in Saccharomyces cerevisiae identified a mutant with a single amino acid change, leucine 61 to tryptophan, that confers several transcriptional defects. We now present several lines of evidence that this H3 mutant, H3-L61W, is impaired at the level of transcription elongation, likely by altered interactions with the conserved factor Spt16, a subunit of the transcription elongation complex yFACT. First, a selection for suppressors of the H3-L61W cold-sensitive phenotype has identified novel mutations in the gene encoding Spt16. These genetic interactions are allele specific, suggesting a direct interaction between H3 and Spt16. Second, similar to several other elongation and chromatin mutants, including spt16 mutants, an H3-L61W mutant allows transcription from a cryptic promoter within the FLO8 coding region. Finally, chromatin-immunoprecipitation experiments show that in an H3-L61W Mutant there is a dramatically altered profile of Spt16 association over transcribed regions, with reduced levels over 5'-coding regions and elevated levels over the 3' regions. Taken together, these and other results provide strong evidence that the integrity of histone H3 is crucial for ensuring proper distribution of Spt16 across transcribed genes and suggest a model for the mechanism by which Spt16 normally dissociates from DNA following transcription.

There is increasing consensus that the perspectives of children need to be taken into account in decisions made by divorcing parents and the courts and that young adults who have lived through their parents' divorces can be an important source of information about children's perspectives. In this study, the authors assessed the perspectives of 820 college adults from divorced families on the issue of children's living arrangements after divorce. Respondents wanted to have spent more time with their fathers as they were growing up, and the living arrangement they believed was best was living equal time with each parent. The living arrangements they had as children gave them generally little time with their fathers. Respondents reported that their fathers wanted more time with them but that their mothers generally did not want them to spend more time with their fathers.

Increased attention is now being focused on developing new technologies to cure atrial fibrillation using catheter ablation techniques. The performance of a MAZE-type procedure using standard catheter ablation technologies is arduous and is associated with an unacceptable risk of complications. The Guidant Heart Rhythm Technologies Linear Ablation System was developed to create long transmural linear lesions. Unique features of this system include the availability of different preshaped multi-electrode steerable ablation catheters, the use of phased radiofrequency (RF) energy, and the control of RF output by varying the duty cycle. A prospective multicenter clinical trial to evaluate the safety and efficacy of a right atrial ablation procedure using this technology to treat atrial fibrillation is currently underway. To date, 15 patients have been enrolled and the procedure was acutely effective in 14 of 15 patients with no complications. Atrial fibrillation has recurred during short-term follow-up in 12 of 15 patients, a not surprising result, because this initial phase of testing involved only right-sided ablation. The early results of the phase I clinical trial confirm the findings of others that successful ablation of chronic atrial fibrillation is likely to require a left atrial approach. This clinical trial, as well as others that are currently underway, will be invaluable in the continuing development of catheter ablation of atrial fibrillation and, ultimately, in determining if the routine use of this therapeutic tool can become a reality.

Engraftment of stem cell-enriched donor marrow implanted in the thymus of a foreign host might facilitate acceptance of donor-specific organ or tissue grafts. To test this hypothesis, allogeneic and xenogeneic CD34+marrow cells from unrelated adult male baboons and humans were injected intrathymically in eight infant female baboons, both with and without standard cyclosporine-based immunosuppression. In allogeneic experiments, male (donor) cells, of both T- and B-cell lineages, were detected by PCR in the peripheral blood of all six recipients and persisted for at least 15 months in 2/4 recipients studied longtutudinally. Donor-derived skin grafts survived twice as long as third party grafts in unimmunosuppressed recipients. In xenogeneic protocols, human male (donor) cells were demonstrable for 7 and 15 months, respectively, in two baboon recipients with evidence that implanted human CD34+cells had produced lymphoid progeny. Survival of donor-specific skin xenografts was prolonged in one of two recipients. These experiments demonstrate that the intrathymic injection of CD34+marrow cells can result in long-lasting lymphohematopoeitic microchimerism in unrelated primates even without immunosuppression and can alter donor-specific skin graft survival.

Albino axolotl eyes were transplanted embryonically to normal and albino axolotl hosts. The animals were allowed to mature for several months and then their transplanted eyes were injected with tritiated proline. The projections from these albino eyes were compared with those obtained from similar transplants of normally pigmented eyes. Special attention was paid to the crossed and uncrossed components of the projections. No differences were found between normal and albino transplants. These results indicate that abnormal retinofugal crossing, which results from a lack of pigmentation in the mammalian eye, does not occur in the axolotl even when the fraction of retinal cells projecting ipsilaterally is experimentally increased by transplanting supernumerary eyes into embryos.

In order to evaluate the effect of perilimbal conjunctival resection on the corneal immune response, we immunized rabbits with either intravenous or topical administration of bovine gamma globulin. After unilateral perilimbal conjunctival resection, the corneas were challenged with intracorneal injections of bovine gamma globulin. Perilimbal conjunctival resection prevented the development of peripheral corneal infiltrates in the rabbits immunized intravenously (P less than .0016) but not in those immunized topically. All the animals developed antibody titers to bovine gamma globulin. Similarly, perilimbal conjunctival resection did not prevent corneal graft rejection in rabbits sensitized to their donors by previous skin grafting.