Probing the energetic particle environment near the Sun.

NASA's Parker Solar Probe mission1 recently plunged through the inner heliosphere of the Sun to its perihelia, about 24 million kilometres from the Sun. Previous studies farther from the Sun (performed mostly at a distance of 1 astronomical unit) indicate that solar energetic particles are accelerated from a few kiloelectronvolts up to near-relativistic energies via at least two processes: 'impulsive' events, which are usually associated with magnetic reconnection in solar flares and are typically enriched in electrons, helium-3 and heavier ions2, and 'gradual' events3,4, which are typically associated with large coronal-mass-ejection-driven shocks and compressions moving through the corona and inner solar wind and are the dominant source of protons with energies between 1 and 10 megaelectronvolts. However, some events show aspects of both processes and the electron-proton ratio is not bimodally distributed, as would be expected if there were only two possible processes5. These processes have been very difficult to resolve from prior observations, owing to the various transport effects that affect the energetic particle population en route to more distant spacecraft6. Here we report observations of the near-Sun energetic particle radiation environment over the first two orbits of the probe. We find a variety of energetic particle events accelerated both locally and remotely including by corotating interaction regions, impulsive events driven by acceleration near the Sun, and an event related to a coronal mass ejection. We provide direct observations of the energetic particle radiation environment in the region just above the corona of the Sun and directly explore the physics of particle acceleration and transport.

The main pillar: Assessment of space weather observational asset performance supporting nowcasting, forecasting, and research to operations.

Space weather forecasting critically depends upon availability of timely and reliable observational data. It is therefore particularly important to understand how existing and newly planned observational assets perform during periods of severe space weather. Extreme space weather creates challenging conditions under which instrumentation and spacecraft may be impeded or in which parameters reach values that are outside the nominal observational range. This paper analyzes existing and upcoming observational capabilities for forecasting, and discusses how the findings may impact space weather research and its transition to operations. A single limitation to the assessment is lack of information provided to us on radiation monitor performance, which caused us not to fully assess (i.e., not assess short term) radiation storm forecasting. The assessment finds that at least two widely spaced coronagraphs including L4 would provide reliability for Earth-bound CMEs. Furthermore, all magnetic field measurements assessed fully meet requirements. However, with current or even with near term new assets in place, in the worst-case scenario there could be a near-complete lack of key near-real-time solar wind plasma data of severe disturbances heading toward and impacting Earth's magnetosphere. Models that attempt to simulate the effects of these disturbances in near real time or with archival data require solar wind plasma observations as input. Moreover, the study finds that near-future observational assets will be less capable of advancing the understanding of extreme geomagnetic disturbances at Earth, which might make the resulting space weather models unsuitable for transition to operations. KEY POINTS: Manuscript assesses current and near-future space weather assetsCurrent assets unreliable for forecasting of severe geomagnetic stormsNear-future assets will not improve the situation.

Infrared analysis of rat bone: age dependency of amorphous and crystalline mineral fractions.

Quantitative infrared spectrophotometric analysis of whole femurs from male rats demonstrates that anorphous calcium phosphate is a major component of bone mineral. The amount of amorphous calcium phosphate in whole bone decreases while the crystalline bone apatite increases during early stages of bone formation. Mature rat bone contains constant levels of both amorphous and crystalline calcium phosphate.

Modulated binding of SATB1, a matrix attachment region protein, to the AT-rich sequence flanking the major breakpoint region of BCL2.

The t(14,18) chromosomal translocation that occurs in human follicular lymphoma constitutively activates the BCL2 gene and disrupts control of apoptosis. Interestingly, 70% of the t(14,18) translocations are confined to three 15-bp clusters positioned within a 150-bp region (major breakpoint region or [MBR]) in the untranslated portion of terminal exon 3. We analyzed DNA-protein interactions in the MBR, as these may play some role in targeting the translocation to this region. An 87-bp segment (87MBR) immediately 3' to breakpoint cluster 3 was essential for DNA-protein interaction monitored with mobility shift assays. We further delineated a core binding region within 87MBR: a 33-bp, very AT-rich sequence highly conserved between the human and mouse BCL2 gene (37MBR). We have purified and identified one of the core factors as the matrix attachment region (MAR) binding protein, SATB1, which is known to bind to AT-rich sequences with a high propensity to unwind. Additional factors in nuclear extracts, which we have not yet characterized further, increased SATB1 affinity for the 37MBR target four- to fivefold. Specific binding activity within 37MBR displayed cell cycle regulation in Jurkat T cells, while levels of SATB1 remained constant throughout the cell cycle. Finally, we demonstrated in vivo binding of SATB1 to the MBR, strongly suggesting the BCL2 major breakpoint region is a MAR. We discuss the potential consequences of our observations for both MBR fragility and regulatory function.

Measurements of the neutron spectrum in transit to Mars on the Mars Science Laboratory.

The Mars Science Laboratory spacecraft, containing the Curiosity rover, was launched to Mars on 26 November 2011. Although designed for measuring the radiation on the surface of Mars, the Radiation Assessment Detector (RAD) measured the radiation environment inside the spacecraft during most of the 253-day, 560-million-kilometer cruise to Mars. An important factor for determining the biological impact of the radiation environment inside the spacecraft is the specific contribution of neutrons with their high biological effectiveness. We apply an inversion method (based on a maximum-likelihood estimation) to calculate the neutron and gamma spectra from the RAD neutral particle measurements. The measured neutron spectrum (12-436 MeV) translates into a radiation dose rate of 3.8±1.2 µGy/day and a dose equivalent of 19±5 µSv/day. Extrapolating the measured spectrum (0.1-1000 MeV), we find that the total neutron-induced dose rate is 6±2 µGy/day and the dose equivalent rate is 30±10 µSv/day. For a 360 day round-trip from Earth to Mars with comparable shielding, this translates into a neutron induced dose equivalent of about 11±4 mSv.

Total protein extraction from cultured cells for use in electrophoresis and western blotting.

Experimentation with cultured cells often requires analyzing cellular protein extract by gel electrophoresis and immunoblotting. Traditional methods for extracting cellular proteins by homogenization or detergent solubilization usually produce protein samples that are viscous (due to the presence of DNA) and prone to degradation due to the presence of endogenous protease activity. We have developed a method that involves solubilization of cells with sodium dodecyl sulfate (SDS), precipitation of proteins with trichloroacetic acid (TCA) with special physical exclusion of DNA aggregate and reconstitution of precipitated proteins with Tris base. Protein samples prepared by this method contain little DNA, making them ideal for long-term storage. The solubilized total protein extracts are fully compatible with protein assay, gel electrophoresis and Western blotting. When compared to protein extracts from a homogenization method, those from the TCA method showed an identical total protein staining pattern on SDS polyacrylamide gel electrophoresis and contained distinct cellular proteins recognized by many monoclonal and polyclonal antibodies tested (including anti-actin, spectrin, protein kinase C (alpha), talin and spectrin) on Western blots.

The surface chemistry of bone mineral and related calcium phosphates.

A review of the surface chemistry of bone mineral, hydroxyapatite and amorphous calcium phosphate is presented. Small-angle x-ray scattering and low-temperature nitrogen adsorption measurements show the magnitude of bone mineral surface to range from 100-200 m-2/g; the synthetic hydroxyapatite surface can vary from 25-200 m-2/g, while synthetic amorphous calcium phosphate ranges in surface from 20-60 m-2/g, according to the respective preparation conditions. The magnitude of heats of adsorption of certain small molecules (CO, Ar, N2, H2O, CH3OH) on bone mineral and hydroxyapatite show that these are polarizing surfaces that form strong bonds with polar or polarizable molecules; water is hydrogen-bonded to these surfaces with energies ranging from 23 kcal/mole for low coverage to 11 kcal/mole after two full monolayers; concomitantly, methanol ranges from 24 kcal/mole to 9 kcal/mole after the adsorption of one and a half monolayers. Stearic acid will close-pack perpendicularly on bone apatite surfaces when adsorbed from cyclohexane solution in a way reminiscent of the adsorption of this long, straight-chain molecule on water surface. It is believed that these molecules are hydrogen-bonded to electronegative ions on the apatite surface. Synthetic hydroxyapatite has long been used in chromatographic adsorption columns because of the specific bonding capacity the surfaces have for certain proteins and polynucleotides. The metabolic interrelationship of bone mineral and the body fluids is in great part dependent upon the nature and magnitude of mineral surface. From the surface studies described herein it was suggested that a chemical linkage could exist in bone between the mineral surface and certain free polar groups of collagen.

Phenytoin pretreatment prevents hypoxic-ischemic brain damage in neonatal rats.

This study was performed to investigate whether the anticonvulsant phenytoin has neuroprotective effect in a model of hypoxia-ischemia with neonatal rats. The left carotid artery of each rat was ligated, followed by 3 h of hypoxic exposure (8% O2) in a temperature-regulated environment (36 degrees C). Two weeks later, brain damage was assessed by measuring loss of brain hemisphere weight. Phenytoin had no effect on body temperature or plasma glucose, but attenuated brain damage in a dose-dependent manner (3, 10, and 30 mg/kg i.p.) when administered before the hypoxic episode. Phenytoin administered during or after hypoxia did not alter hypoxic brain damage significantly. A parallel experiment using histological examination of frozen brain sections demonstrated less brain infarction after phenytoin treatment (30 mg/kg i.p.). In an additional experiment measuring breakdown of an endogenous brain calpain substrate, spectrin, phenytoin treatment reduced this measure of early cellular damage. Our results indicate that pretreatment with phenytoin is neuroprotective at a plasma phenytoin concentration of approximately 12 micrograms/ml. These results are consistent with the hypothesis that blockade of voltage-dependent sodium channels reduces brain damage following ischemia.

Formation of calcium phosphates in saliva and dental plaque.

This is an X-ray diffraction study of the mineral phases in saliva and early dental plaque. The salivas studied came from patients with cystic fibrosis (CF), those with asthma, and heavy and light calculus formers. One-week old plaque was studied from individuals who are heavy, moderate, and light calculus formers.

Mineral parameters in early fracture repair.

In an effort to define and characterize the initial mineralization product of fracture-healing, we studied the mineral components within a model of endochondral osseous repair. Fracture calluses from the tibiae of rats and rabbits undergoing endochondral fracture-healing were analyzed, in toto and following density fractionation, by physicochemical and crystallographic techniques. Significant changes in mineral composition, crystal size, and density occurred in the early phases of fracture repair. In the rat, two weeks after fracture, the calcium-to-phosphorus ratio was higher than that of the mineral component, possibly due to calcium-binding to some of the macromolecules known to be present. The earliest mineral was poorly crystallized hydroxyapatite with a high carbonate content. Crystal perfection improved rapidly and approached that of normal diaphyseal bone within eight weeks after endochondral fracture in both the rabbit and the rat.

Problems in formulating method-insensitive proficiency testing materials.

Significant problems exist in formulating method-insensitive proficiency materials. Many steps are required in processing human plasma, and difficult choices are involved in the selection of appropriate materials to be added to the processed plasma. Additionally, analytes may vary widely in their recovery from method to method. To enhance understanding of the procedures and problems involved in the development and manufacture of proficiency materials, a number of constituents and their method-specific recoveries are reviewed.

Bone structure, composition, and mineralization.

Bone structure and function are dependent on complex interactions between cells, matrix, cell-derived factors, and systemic factors. The deposition of mineral in bone, which enables the skeleton to function properly, is described as a four-step process of matrix modification, crystal nucleation, crystal growth, and remodeling. Insight into the function of bone components in the mineralization process is provided by in vitro studies and analysis of abnormal calcifications.

Measurements of energetic particle radiation in transit to Mars on the Mars Science Laboratory.

The Mars Science Laboratory spacecraft, containing the Curiosity rover, was launched to Mars on 26 November 2011, and for most of the 253-day, 560-million-kilometer cruise to Mars, the Radiation Assessment Detector made detailed measurements of the energetic particle radiation environment inside the spacecraft. These data provide insights into the radiation hazards that would be associated with a human mission to Mars. We report measurements of the radiation dose, dose equivalent, and linear energy transfer spectra. The dose equivalent for even the shortest round-trip with current propulsion systems and comparable shielding is found to be 0.66 ± 0.12 sievert.