Metals resources: products in turmoil

Resource /Energy Economics and Policy,

An Improved Model for Relativistic Solar Proton Acceleration applied to the 2005 January 20 and Earlier Events

This paper presents results on modelling the ground level response of the higher energy protons for the 2005 January 20 ground level enhancement (GLE). This event, known as GLE 69, produced the highest intensity of relativistic solar particles since the famous event on 1956 February 23. The location of recent X-ray and gamma-ray emission (N14 W61) was near to Sun-Earth connecting magnetic field lines, thus providing the opportunity to directly observe the acceleration source from Earth. We restrict our analysis to protons of energy greater than 450 MeV to avoid complications arising from transport processes that can affect the propagation of low energy protons. In light of this revised approach we have reinvestigated two previous GLEs: those of 2000 July 14 (GLE 59) and 2001 April 15 (GLE 60). Within the limitations of the spectral forms employed, we find that from the peak (06:55 UT) to the decline (07:30 UT) phases of GLE 69, neutron monitor observations from 450 MeV to 10 GeV are best fitted by the Gallegos-Cruz & Perez-Peraza stochastic acceleration model. In contrast, the Ellison & Ramaty spectra did not fit the neutron monitor observations as well. This result suggests that for GLE 69, a stochastic process cannot be discounted as a mechanism for relativistic particle acceleration, particularly during the initial stages of this solar event. For GLE 59 we find evidence that more than one acceleration mechanism was present, consistent with both shock and stochastic acceleration processes dominating at different times of the event. For GLE 60 we find that Ellison & Ramaty spectra better represent the neutron monitor observations compared to stochastic acceleration spectra. The results for GLEs 59 and 60 are in agreement with our previous work.Comment: 42 pages, 10 figures, 10 tables, published in ApJ, August 200

Does The Hype Exceed The Reality For ERP Applications And Small Manufacturing Companies: A Case Study

This case study describes the implementation of an ERP in a new arena – small manufacturing companies – and explores possible differences compared with successful implementations of ERP’s in larger manufacturing companies. The company that was studied is a small manufacturing company in Maine (less than $10 million in annual sales) that began implementing a small business ERP 12 months ago. Information was collected through interviews and the completion of a questionnaire based on the Stratman-Roth ERP Competence Scales (2002). Results suggest that while this company’s ERP implementation has been more positive than negative, a small company’s limited financial resources and lack of internal experience and expertise in large IT system projects add to the already complex challenges surrounding an ERP implementation

Relativistic Proton Production During the 14 July 2000 Solar Event: The Case for Multiple Source Mechanisms

Protons accelerated to relativistic energies by transient solar and interplanetary phenomena caused a ground-level cosmic ray enhancement on 14 July 2000, Bastille Day. Near-Earth spacecraft measured the proton flux directly and ground-based observatories measured the secondary responses to higher energy protons. We have modelled the arrival of these relativistic protons at Earth using a technique which deduces the spectrum, arrival direction and anisotropy of the high-energy protons that produce increased responses in neutron monitors. To investigate the acceleration processes involved we have employed theoretical shock and stochastic acceleration spectral forms in our fits to spacecraft and neutron monitor data. During the rising phase of the event (10:45 UT and 10:50 UT) we find that the spectrum between 140 MeV and 4 GeV is best fitted by a shock acceleration spectrum. In contrast, the spectrum at the peak (10:55 UT and 11:00 UT) and in the declining phase (11:40 UT) is best fitted with a stochastic acceleration spectrum. We propose that at least two acceleration processes were responsible for the production of relativistic protons during the Bastille Day solar event: (1) protons were accelerated to relativistic energies by a shock, presumably a coronal mass ejection (CME). (2) protons were also accelerated to relativistic energies by stochastic processes initiated by magnetohydrodynamic (MHD) turbulence.Comment: 38 pages, 9 figures, accepted for publication in the Astrophysical Journal, January, 200

Spatial and Temporal Variability of the Gamma Radiation from Earth's Atmosphere during a Solar Cycle

The Solar Maximum Mission satellite's Gamma Ray Spectrometer observed Earth's atmosphere for most of the period 1980-1989. Its 28deg orbit ensured that a range of geomagnetic latitudes (geomagnetic cutoff rigidities) was sampled. We measured the variation with time and rigidity of albedo gamma-ray lines at 1.6 MeV, 2.3 MeV and 4.4 MeV which are diagnostic of Galactic cosmic radiation penetrating the cutoff and of the secondary neutrons produced in the atmosphere. We found that the gamma-ray line intensities varied inversely with solar activity and cutoff rigidity, as expected. The line ratio (1.6 MeV + 2.3 MeV)/4.4 MeV was remarkably constant (close to 0.39) at all times and rigidities; the former two lines are produced by 5-10 MeV secondary neutrons causing excitation and de-excitation of 14N, while the latter is produced by more energetic (>20 MeV) neutrons inducing spallation. We infer that the shape of the secondary neutron energy spectrum is virtually constant everywhere and at all times. We also measured the intensity of the 0.511 MeV electron-positron annihilation line. This line too varies with solar cycle and cutoff rigidity, but its fall-off from low to high rigidity is less marked than that of the nuclear lines. This results from the energy dependences of the cross sections for positron production and for the hadronic processes which which produce secondary neutrons.Comment: 11 pages, 12 figs., J. Geophys. Res. in pres

Evaluation of encapsulating and microporous nondegradable hydrogel scaffold designs on islet engraftment in rodent models of diabetes

Islet transplantation is a promising therapeutic option for type 1 diabetes mellitus, yet the current delivery into the hepatic portal vasculature is limited by poor engraftment. Biomaterials have been used as a means to promote engraftment and function at extrahepatic sites, with strategies being categorized as encapsulation or microporous scaffolds that can either isolate or integrate islets with the host tissue, respectively. Although these approaches are typically studied separately using distinct material platforms, herein, we developed nondegradable polyethylene glycol (PEG)‐based hydrogels for islet encapsulation or as microporous scaffolds for islet seeding to compare the initial engraftment and function of islets in syngeneic diabetic mice. Normoglycemia was restored with transplantation of islets within either encapsulating or microporous hydrogels containing 700 islet equivalents (IEQ), with transplantation on microporous hydrogels producing lower blood glucose levels at earlier times. A glucose challenge test at 1 month after transplant indicated that encapsulated islets had a delay in glucose‐stimulated insulin secretion, whereas microporous hydrogels restored normoglycemia in times consistent with native pancreata. Encapsulated islets remained isolated from the host tissue, whereas the microporous scaffolds allowed for revascularization of the islets after transplant. Finally, we compared the inflammatory response after transplantation for the two systems and noted that microporous hydrogels had a substantially increased presence of neutrophils. Collectively, these findings suggest that both encapsulation and microporous PEG scaffold designs allow for stable engraftment of syngeneic islets and the ability to restore normoglycemia, yet the architecture influences islet function and responsiveness after transplantation.Non‐degradable PEG hydrogels were developed for islet encapsulation or islet seeding to compare engraftment. Using a syngeneic rodent model of diabetes, normoglycemia was restored using either encapsulating or microporous scaffolds containing 700 islet equivalent, with microporous hydrogels achieving lower blood glucose levels at earlier time points. Characterization of the inflammatory response demonstrated microporous scaffolds had a substantially increased presence of neutrophils. These studies confirm both scaffold designs allow for engraftment, yet the architecture influences islet function and responsiveness post‐transplantation.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/146483/1/bit26741.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/146483/2/bit26741_am.pd

Comparative Evaluation of the Hemodynamic Effects of Oral Cimetidine, Ranitidine, and Famotidine as Determined by Echocardiography

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90052/1/j.1875-9114.1995.tb04349.x.pd

The Momentum of Human Behavior in a Natural Setting

Adults with mental retardation in a group home received popcorn or coffee reinforcers for sorting plastic dinnerware. In Part 1 of the experiment, reinforcers were dispensed according to a variable-interval 60-s schedule for sorting dinnerware of one color and according to a variable-interval 240-s schedule for sorting dinnerware of a different color in successive components of a multiple schedule. Sorting rates were similar in baseline, but when a video program was shown concurrently, sorting of dinnerware was more resistant to distraction when correlated with a higher rate of reinforcement. In Part 2 of the experiment, popcorn or coffee reinforcers were contingent upon sorting both colors of dinnerware according to variable-interval 60-s schedules, but additional reinforcers were given independently of sorting according to a variable-time 30-s schedule during one dinnerware-color component. Baseline sorting rate was lower but resistance to distraction by the video program was greater in the component with additional variable-time reinforcers. These results demonstrate that resistance to distraction depends on the rate of reinforcers obtained in the presence of component stimuli but is independent of baseline response rates and response-reinforcer contingencies. Moreover, these results are similar to those obtained in laboratory studies with pigeons, demonstrating that the determination of resistance to change by stimulus-reinforcer relations is not confined to controlled laboratory settings or unique to the pigeon

Testicular infarction in the newborn: Ultrasound findings

Three patients with neonatal testicular torsion and infarction (two bilateral, one unilateral) are presented with a distinctive sonographic appearance. All five testes appeared inhomogeneously hypoechoic and each was surrounded by a brightly echogenic rim. Whereas surgical exploration was required in the past to establish the diagnosis of testicular infarction in the neonate, sonographic demonstration of the abnormality in the appearance of the testicular parenchyma permits nonoperative diagnosis. Because surgical salvage of the testis in the setting of neonatal extravaginal torsion is thought to be quite rare, the necessity of removing the testis is less clear when the diagnosis is established preoperatively.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46692/1/247_2005_Article_BF02013166.pd