Martin Gardner and His Influence on Recreational Math

Recreational mathematics is a relatively new field in the world of mathematics. While sometimes overlooked as frivolous since those who practice it need no advanced knowledge of the subject, recreational mathematics is a perfect transition for people to experience the joy in logically establishing a solution. Martin Gardner recognized that this pattern of proving solutions to questions is how mathematics progresses. From his childhood on, Gardner greatly influenced the mathematical world. Although not a mathematician, he inspired many to pursue careers and make advancements in mathematics during his 25-year career with Scientific American. He encouraged novices to expand their knowledge, enlightened professionals of computer science developments, and established his own proofs

A Feasibility Report on Rooftop Photovoltaic Solar Arrays at the University of Mississippi

The following project is a feasibility report for rooftop photovoltaic (PV) solar panel installations on select building across the University of Mississippi’s campus. The purpose of this report is to determine the value of the energy that a rooftop solar system is capable of producing and the effect this generated energy will have on the energy needs of the building. As an entity with a stated commitment to sustainability and good stewardship of its resources, the University of Mississippi is on its way to become the state’s leader in sustainability, boasting the state’s largest roof-mount solar system. The analysis utilizes data collected from that system, architectural footprints of additional buildings across campus, and an online photovoltaic energy system calculator to determine the size and potential generation of solar system. The potential generation of each building’s system was then analyzed based on economic parameters. From the results of the study, recommendations are given to the university on how to best pursue its goal of sustainability and responsible use of its resources. The results of this report emphasize that the current costs associated with rooftop solar systems make the projects undesirable and that energy efficiency building operation and reduced energy demand can be much more beneficial in terms of resource stewardship

Assessing the Scalability of Parallel Programs: Case Studies from IBAMR

Programmers are driven to parallelize their programs because of both hardware limitations and the need for their applications to provide information within acceptable timescales. The modelling of yesterday's weather, while still of use, is of much less use than tomorrow's. Given this motivation, those researchers who build libraries for use in parallel codes must assess the performance when deployed at scale to ensure their end users can take full advantage of the computational resources available to them. Blindly measuring the execution time of applications provides little insight into what, if any, challenges the code faces to achieve optimal performance, and fails to provide enough information to confirm any gains made by attempts to optimize the code. This leads to the desire to gain greater insight by inspecting the call stack and communication patterns. The author reviews the definitions of the forms of scalability that are desirable for different applications, discusses tools for collecting performance data at varying levels of granularity, and describes methods for analyzing this data in the context of case studies performed with applications using the IBAMR library.Bachelor of Scienc

Relationship of Adjustment and Delinquent Behavior with School Grade, Socioeconomic Status, Category of Adjudication, Race, and Sex

Psycholog

Poor Survivorship and Frequent Complications at a Median of 10 Years After Metal-on-Metal Hip Resurfacing Revision

Background High short-term failure rates have been reported for several metal-on-metal hip resurfacing (MoMHR) designs. Early observations suggested that MoMHRs revised to total hip arthroplasties (THAs) for pseudotumor had more major complications and inferior patient-reported outcomes compared with other revision indications. However, little is known about implant survivorship and patient-reported outcomes at more than 5 years after MoMHR revision. Questions/purposes (1) What are the implant survivorship, proportion of complications and abnormal radiological findings, and patient-reported outcomes at a median of 10 years after MoMHR revision surgery? (2) Are survivorship, complications, and patient-reported outcomes influenced by revision indication? (3) Do any other factors predict survivorship, complications, and patient-reported outcomes? Methods Between 1999 and 2008, 53 MoMHR revision procedures in 51 patients (mean age, 55 years; 62% female) were performed at one center and were all included in this retrospective study. Two patients (4%) were lost to followup and two patients (4%) died before a minimum followup of 7 years (median, 10.3 years; range 7–15 years). Revision indications included pseudotumor (n = 16), femoral neck fracture (n = 21), and other causes (n = 16). In most cases (62%, n = 33) both components were revised to a non-MoM bearing THA with the remainder (38%, n = 20: fracture, loosening, or head collapse) undergoing femoral-only revision to a large-diameter MoM THA. Postrevision complications, rerevision, Oxford Hip Score (OHS), and UCLA score were determined using both a longitudinally maintained institutional database and postal questionnaire. Implant survivorship was assessed using the Kaplan-Meier method (endpoint was rerevision surgery). Radiographs at latest followup were systematically assessed for any signs of failure (loosening, migration, osteolysis) by one observer blinded to all clinical information and not involved in the revision procedures. Results Overall, 45% (24 of 53) experienced complications and 38% (20 of 53) underwent rerevision. Ten-year survival free from rerevision for revised MoMHRs was 63% (95% confidence interval [CI], 48%–74%). Revision indications were not associated with differences in the frequency of complications or repeat revisions. With the numbers available, 10-year survival free from rerevision for pseudotumor revisions (56%; 95% CI, 30%–76%) was not different from the fracture (68%; 95% CI, 42%–85%; p = 0.359) and other groups (63%; 95% CI, 35%–81%; p = 0.478). Pseudotumor revisions had inferior OHSs (median, 21; range, 2–46; p = 0.007) and UCLA scores (median, 2; range, 2–7; p = 0.0184) compared with fracture and other revisions. Ten-year survival free from rerevision after femoral-only revision using another large-diameter MoM bearing was lower (p = 0.0498) compared with all component revisions using non-MoM bearings. After controlling for potential confounding variables such as age, sex, and revision indication, we found femoral-only revision as the only factor predicting rerevision (hazard ratio, 5.7; 95% CI, 1.1–29; p = 0.040). Conclusions Poor implant survivorship and frequent complications were observed at a median of 10 years after MoMHR revision. However, patients undergoing femoral-only revisions with large-diameter MoM bearings had the worst survivorship, whereas patients revised for pseudotumor had the most inferior patient-reported outcomes. Our findings suggest these two patient subgroups require regular surveillance after MoMHR revision

The nature and properties of amorphous colloids formed from Mazama tephra

Soil samples from the Mazama tephra deposit were collected from the AC and C2 horizons at five different locations along the axis of the main depositional lobe. The clay fraction from the samples was recovered and studied by means of chemical, x-ray, DTA and electron microscopy methods in order to characterize the nature and properties of amorphous clays forming in this relatively homogeneous parent material of known age. Dispersion of the amorphous clays from the pumice samples was found to be difficult unless samples were first pretreated to remove iron oxides and organic matter. The diothionite-citratebicarbonate (DCB) iron removal treatment, however, was found to significantly alter the morphology of a reference imogolite sample by leaving individual strands of mineral coated with a gel. The comparison of DTA data from the imogolite and synthetic allophanes before and after defferation treatment also shows that significant changes in the amorphous clays resulted from the clean up treatment. Alternate methods for amorphous clay dispersion were tried on a variety of ando soil samples. None of the methods were found to be effective for dispersing all samples. Several washings in distilled water adjusted to pH 5. 0 with HC1 resulted in the dispersion of most samples and was used in this study to separate the amorphous clays from the Mazama tephra. The clays removed from the pumice samples contained from 47 to 84 percent amorphous colloids. The molar ratio of SiO₂:Al₂0₃ for all the samples was generally between 1 and 2. The types of clays found at each site studied along the transect were rather varied. Halloysite was found at all locations except one and generally was more common near the base of the pumice profile. The mineral dominated the clay fraction at a poorly drained site near the source but was absent in another similar site about 400 km away. The latter contained abundant imogolite and allophane. This difference in secondary mineralogy from the same parent material under similar weathering regimes presents an enigma. One possible explanation is based on the observation that samples of undisturbed tephra at far distances from the source contain fewer feldspars than samples near the source. The halloysite is thought to be related to feldspar weathering. Samples from drier sites along the transect had clay fractions containing predominately allophane with some few crystals of halloysite and some imogolite All samples had appreciable quantities of clay size glass shards. Masses of silica bodies and oxides of iron in addition to halloysite and allophane were found in the C2 horizon at the driest site. The cation exchange capacities of the clay samples were highly pH dependent. All samples had appreciable anion exchange capacities at pH 4.0. The DCB treated samples had CEC values much higher than non-treated samples. The magnitude of CEC for the synthetic gels depended on their composition and was highest when the molar SiO₂ :A1₂O₃ ratio was about 4.0. The clays sorbed large amounts of phosphate. The samples highest in the amorphous gels generally sorbed more phosphate than samples containing halloysite. All the clays had weak acid buffering curves. Most samples had two distinct buffering ranges, one at low pH and one at high pH. The curves for the samples highest in halloysite were buffered at much higher pH values than samples containing mostly amorphous clays. The nature and properties of the amorphous clays in the Mazama tephra were found to be similar to those reported by Japanese and New Zealand workers for other volcanic tephra deposits

Development of a Space-Flight ADR Providing Continuous Cooling at 50 Mk with Heat Rejection at 10 K

Future astronomical instruments will require sub-Kelvin detector temperatures to obtain high sensitivity. In many cases large arrays of detectors will be used, and the associated cooling systems will need performance surpassing the limits of present technologies. NASA is developing a compact cooling system that will lift heat continuously at temperatures below 50 mK and reject it at over 10 K. Based on Adiabatic Demagnetization Refrigerators (ADRs), it will have high thermodynamic efficiency and vibration-free operation with no moving parts. It will provide more than 10 times the current flight ADR cooling power at 50 mK and will also continuously cool a 4 K stage for instruments and optics. In addition, it will include an advanced magnetic shield resulting in external field variations below 5 T. We describe the cooling system here and report on the progress in its development