Results from the Radiation Assessment Detector on the International Space Station: Part 1, the Charged Particle Detector.

We report the results of the first six years of measurements of the energetic particle radiation environment on the International Space Station (ISS) with the Radiation Assessment Detector (ISS-RAD), spanning the period from February 2016 to February 2022. The first RAD was designed and built for MSL, the Mars Science Laboratory rover, also known as Curiosity; it has been operating on Mars since 2012 and is referred to here as MSL-RAD. ISS-RAD combines two sensor heads, one nearly identical to the single MSL-RAD sensor head, the other with greatly enhanced sensitivity to fast neutrons. These two sensor heads are referred to as the Charged Particle Detector (CPD) and Fast Neutron Detector (FND), respectively. Despite its name, the CPD is also capable of measuring high-energy neutrons and γ-rays, as is MSL-RAD. ISS-RAD was flown to the ISS in December 2015 and was deployed in February 2016, initially in the USLab module. RAD was used as a survey instrument from January 2017 through May 2020, when the instrument was positioned in the USLab and set to a zenith-pointing orientation. The energetic particle environment on the ISS is complex and varies on short time scales owing to the orbit, which has a 51.6∘ inclination with respect to the equator and has had an altitude in the 400-440 km range in this time period. The ISS moves continuously through the geomagnetic field, the strength of which varies with latitude, longitude, and altitude. The orbit passes through the South Atlantic Anomaly (SAA) several times a day, where magnetically trapped protons and electrons produce large but transient increases in observed fluxes and absorbed dose rates. The environment inside the ISS is affected by the solar cycle, altitude, and the local shielding, which varies between different ISS modules. We report results for charged particle absorbed dose and dose equivalent rates in various positions in the ISS. In an accompanying paper, we report similar results for neutron dose equivalent rates obtained with the ISS-RAD Fast Neutron Detector.

Results from the Radiation Assessment Detector on the International Space Station, Part 2: The fast neutron detector.

We report the results of the first six years of measurements of so-called fast neutrons on the International Space Station (ISS) with the Radiation Assessment Detector (ISS-RAD), spanning the period from February 2016 to February 2022. ISS-RAD combines two sensor heads, one nearly identical to the single sensor head in the Mars Science Laboratory RAD (MSL-RAD). The latter is described in a companion article to this one. The novel sensor is the FND, or fast neutron detector, designed to measure neutrons with energies in the range from 200 keV to about 8 MeV. ISS-RAD was deployed in February 2016 in the USLAB module, and then served as a survey instrument from March 2017 until May 2020. Data were acquired in Node3, the Japanese Pressurized Module, Columbus, and Node2. At the conclusion of the survey portion of RAD's planned 10-year campaign on ISS, the instrument was stationed in the USLAB; current plans call for it to remain there indefinitely. The radiation environment on the ISS consists of a complex mix of charged and neutral particles that varies on short time scales owing to the Station's orbit. Neutral particles, and neutrons in particular, are of concern from a radiation protection viewpoint, because they are both highly penetrating (since they do not lose energy via direct ionization) and, at some energies, have high biological effectiveness. Neutrons are copiously produced by GCRs and other incident energetic particles when they undergo nuclear interactions in shielding. As different ISS modules have varying amounts of shielding, they also have varying neutron environments. We report results for neutron fluences and dose equivalent rates in various positions in the ISS.

Results from the Radiation Assessment Detector on the International Space Station: Part 3, combined results from the CPD and FND.

The energetic particle radiation environment on the International Space Station (ISS) includes both charged and neutral particles. Here, we make use of the unique capabilities of the Radiation Assessment Detector (ISS-RAD) to measure both of these components simultaneously. The Charged Particle Detector (CPD) is, despite its name, capable of measuring neutrons in the energy range from about 4 MeV to a few hundred MeV. Combined with data from the Fast Neutron Detector (FND) in the 0.2 to 8 MeV range, we present the first broad-spectrum measurements of the neutron environments in various locations within the ISS since an early Bonner-Ball experiment that was conducted before the Station was fully constructed. The data presented here span the time period from February 2016 to February 2022. In addition to presenting broad-spectrum neutron fluence measurements, we show correlations of the measured neutron dose equivalent with charged-particle dose rates. The ratio of charged-particle dose to neutron dose equivalent is found to be relatively stable within the ISS.

Pressure-dependence Raman spectroscopy and the lattice dynamic calculations of Bi2(MoO4)3 crystal.

This work reports a pressure-dependent Raman spectroscopic study and the theoretical lattice dynamics calculations of a Bi2(MoO4)3 crystal. The lattice dynamics calculations were performed, based on a rigid ion model, to understand the vibrational properties of the Bi2(MoO4)3 system and to assign the experimental Raman modes under ambient conditions. The calculated vibrational properties were helpful to support pressure-dependent Raman results, including eventual structural changes induced by pressure changes. Raman spectra were measured in the spectral region between 20 and 1000 cm-1 and the evolution of the pressures values was recorded in the range of 0.1-14.7 GPa. Pressure-dependent Raman spectra showed changes observed at 2.6, 4.9 and 9.2 GPa, these changes being associated with structural phase transformations. Finally, principal component analysis (PCA) and hierarchical cluster analysis (HCA) were performed to infer the critical pressure of phase transformations undergone by the Bi2(MoO4)3 crystal.

A temperature-dependent Raman scattering and X-ray diffraction study of K2Mo2O7·H2O and ab initio calculations of K2Mo2O7.

This study reports a temperature-dependent Raman scattering and X-ray diffraction study of K2Mo2O7·H2O. The high-temperature Raman scattering analysis shows that the material remains structurally stable, with triclinic symmetry, in a temperature range from 300 to 413 K and undergoes a structural phase transition between 413 and 418 K. This phase transition is most likely connected with the dehydration process of K2Mo2O7·H2O. The temperature-dependent X-ray diffraction patterns are measured from 30 to 573 K. The results show that the discovered phase transition occurs between 419 and 433 K, in good agreement with the Raman scattering results. According to the Raman data, with increasing temperature, the dehydrated crystal of K2Mo2O7 undergoes a new phase transformation at 603 K and melts at ~843 K. Principal component and hierarchical cluster analyses are performed based on the treatment of the raw spectral data to infer the phase transformations occurring in the material. Assignments of the Raman modes for the K2Mo2O7 system at ambient conditions are studied through first-principles calculations based on density functional perturbation theory. These calculations are applied to understand the electronic properties, including the band structure and the associated projected density of states, of K2Mo2O7 under the local density approximation.

Pressure-induced phase transition in Glycinium maleate crystal.

The multicomponent glycinium maleate single crystal was grown by the slow evaporation method. The crystal was submitted to pressures ranging from 1 atm to 5.6 GPa and Raman spectroscopy was used as a spectroscopic probe. The modifications of relative intensity bands related to the lattice modes at 0.3 GPa were associated with rearrangements of hydrogen bonds. Moreover, between 1.7 and 4.8 GPa the Raman results indicate that the crystal experience a long structural phase transition, which was confirmed by PCA analysis. DFT calculations gave us more precision in the assignments of modes. The behavior of the internal modes under pressure showed that the maleic acid molecule undergoes greater modifications than glycine amino acid. All observed modifications were reversible when the pressure was released.

Lattice dynamics calculations and high-pressure Raman spectra of the ZnMoO4.

We report here the analysis of vibrational properties of the ZnMoO4 by using theoretical and experimental approaches, well as results of high pressure experiments in this system. The analysis of the lattice dynamics calculations through the classical rigid ion model, was applied to determine the mode assignment in the triclinic phase of the ZnMoO4. Additionally, the experimental high-pressure Raman spectra of the ZnMoO4 were carried out from 0 GPa up to 6.83 GPa to shed light on the structural stability of this system. The pressure-dependent studies showed that this crystal undergoes a first order phase transition at around 1.05 GPa. The Raman spectrum analysis of the new phase shows a significant change in the number of modes for the spectral range of 20-1000 cm-1. The instability of this phase occurs due to the decrease of the MoO bond lengths in the high-pressure phase, connected with tilting and/or rotations of the MoO4 tetrahedra leading to a disorder at the MoO4 sites. The second and third phase transformations were observed, respectively, at about 2.9 GPa and 4.77 GPa, with strong evidences, in the Raman spectra, of crystal symmetry change. The principal component analysis (PCA) and the hierarchical cluster analysis (HCA) were used in order to infer the intervals of pressure where the different phases do exist. Discussion about the number of non equivalent sites for Mo ions and the kind of coordination for molybdenum atoms is also furnished.

Temperature dependence Raman spectroscopy and DFT calculations of Bi2(MoO4)3.

This work reports a theoretical and experimental study on the electronic and vibrational properties of Bi2(MoO4)3. First-principle calculations were applied to increase the understanding on the properties of the chemical composition through the energy bands. The conduction band minimum (CBM) is found at the high symmetric Γ-point, while the valence-band maximum (VBM) is located between the Z and the Γ-points. Therefore, these facts confirm that the Bi2(MoO4)3 crystal is a semiconductor compound with an indirect band-gap of about 2.1 eV. Moreover, lattice dynamic properties were calculated using density functional perturbation theory (DFPT) in order to assign the experimental Raman bands. In addition, we performed temperature-dependent Raman spectroscopic studies in the Bi2(MoO4)3 crystals to obtain information on structural changes induced by effects of the temperature change. From the changes observed in the Raman spectra phase transitions at ∼ 668 and 833 K were inferred, with the last one possibly related to the disorder due to the heating process.

Phase transformation in the C form of myristic-acid crystals and DFT calculations.

In this study, the vibrational frequencies of myristic acid (CH3(CH2)12COOH) were obtained using density functional theory calculations, and the results were compared with experimental Raman and infrared data. Additionally, Raman spectra of crystalline myristic acid were recorded in the 300-20 K range. Raman spectroscopy gives important insights into the effect of low temperatures on its monoclinic phase. X-ray diffraction was performed from 298 to 133 K to provide additional information about the cryogenic behavior of the crystals. These undergo a phase transformation, which was confirmed by differential scanning calorimetry through an enthalpy anomaly observed at low temperatures. Raman spectra and X-ray diffraction refinement of the cell parameters in combination with differential scanning calorimetry at low temperatures revealed slight modifications, confirming a conformational change in the myristic acid molecules involving rearrangement of dimers within the unit cell.

Morphological, histological and ultrastructural changes in the olive pistil during flowering.

Sexual reproduction is essential for the propagation of higher plants. From an agronomical point of view, this is a particularly key process because fertilization guarantees fruit formation in most cultivated fruit species. In the olive, however, in spite of its agricultural importance, little attention has been paid to the study of sexual reproduction. In order to investigate the cellular and molecular mechanisms that regulate pollen-pistil interactions in the olive during the progamic phase, it is essential to first have a good knowledge of the reproductive structures involved in such interactions. This study characterizes the anatomical and ultrastructural changes in the olive pistil, beginning from the young pistil developing within the bud until the time of petal loss and visible stigma senescence. We have correlated changes in the pistil with a series of defined floral developmental stages and determined that olive pistil structures cannot be considered completely mature and ready to be pollinated and fertilized until the onset of anthesis. Our results clearly show histological and ultrastructural variation during the diverse flowering events. We discuss whether the changes observed might influence or result from pollen-pistil interactions during the progamic phase.

Recombinogenic effects of the aqueous extract of pulp from pequi fruit (Caryocar brasiliense) on somatic cells of Drosophila melanogaster.

Caryocar brasiliense Camb. is a tree popularly known in Central Brazil as pequi. Its fruit contains carotenes, retinols, vitamin C, and polyphenols. These compounds possess antioxidant properties preventing excessive free radical formation and modulating the genotoxicity of physical and chemical agents in the body. However, at high concentrations these compounds can have recombinogenic and mutagenic effects, because they can act as pro-oxidants. We examined the genotoxic effects of aqueous extracts of pequi pulp on wing spots of Drosophila melanogaster using the somatic mutation and recombination test (SMART). SMART was applied to a standard cross and to a high bioactivation cross. Two types of descendants were obtained from these crosses: marked-heterozygous (mwh + / + flr3) and balancer-heterozygous (mwh + / + TM3, Bds). Seventy-two-hour larvae from both crosses were treated with pequi pulp extract at 1, 5 and 10%. The extract increased significantly the frequency of mutant spots when compared with the negative control. Recombinogenic effects were also observed in the mwh/TM3 descendants.

Olive pollen profilin (Ole e 2 allergen) co-localizes with highly active areas of the actin cytoskeleton and is released to the culture medium during in vitro pollen germination.

Pollen allergens offer a dual perspective of study: some of them are considered key proteins for pollen physiology, but they are also able to trigger allergy symptoms in susceptible humans after coming in contact with their tissues. Profilin (Ole e 2 allergen) has been characterized, to some extent, as one of the major allergens from Olea europaea L. pollen, a highly allergenic species in the Mediterranean countries. In order to obtain clues regarding the biological role of this protein, we have analyzed both its cellular localization and the organization of actin throughout pollen hydration and early pollen tube germination. The localization of the cited proteins was visualized by confocal laser scanning microscopy immunofluorescence using different antibodies. Upon pollen hydration and pollen germination, a massive presence of profilin was detected close to the site of pollen tube emergence, forming a ring-like structure around the 'effective' apertural region. Profilin was also detected in the pollen exine of the germinating pollen grains and in the germination medium. After using a permeabilization-enhanced protocol for immunolocalization, profilin was also localized in the cytoplasm of the pollen tube, particularly at both the proximal and apical ends. Noticeable accumulations of actin were observed in the cytoplasm of the pollen tube; particularly, in both the apical region and the area immediately close to the aperture. Actin filaments were not observed, probably due to the need of further enhanced fixation procedures. The ultrastructural localization of profilin showed the presence of the protein in the cytoplasm of both the mature pollen grain and the pollen tube. The results shown here could be interpreted as signs of a massive dissociation of the actin-profilin complexes, mobilization of actin monomers, and therefore, an intense activity of the actin cytoskeleton. The extensive release of allergenic proteins from the pollen grain into the surrounding aqueous media, as described here for profilin, may help us to understand the mechanisms by which these allergens might come in contact with the human mucosa, therefore triggering the symptoms of allergy.

Differential characteristics of olive pollen from different cultivars: biological and clinical implications.

The olive tree is grown in many parts of the world. Its germplasm is very broad, with 250 varieties in Spain alone. Variations in the ability of pollen to germinate have been studied in detail and show conspicuous differences between varieties. However, commercial olive pollen from cultivars whose origin is unknown is the material that is commonly used for clinical and biological studies. We aim to assess the putative heterogeneity of olive cultivars with regard to the presence of several pollen allergens and to determine whether these differences have biological and clinical relevance. Previous studies show that most allergens isolated and characterized to date are highly polymorphic. Olive cultivars display wide differences in the expression levels of many allergens and in the number and molecular characteristics of the allergen isoforms expressed. These differences are maintained over the years, and are intrinsic to the genetics of each cultivar. Such broad polymorphism seems to be involved in the physiology of the olive reproductive system, which might include the adaptation of the plant to different environmental conditions, the establishment of the compatibility system, and pollen performance. The differences in allergen composition in cultivars, particularly in the Ole e 1 allergen, are responsible for the important differences in the allergenic potency of the extracts. These findings could have a number of implications for the diagnosis and therapy of olive pollen allergy. We discuss how cultivar differences affect extract quality, diagnostic and therapeutic efficacy and safety, and the development of new vaccines based on the use of recombinant allergens.

Pla 1 1 and Ole e 1 pollen allergens share common epitopes and similar ultrastructural localization.

BACKGROUND: English plantain (Plantago lanceolata L.) and olive (Olea europaea L.) pollens are important causes of pollinosis in large areas of North America, Australia, and the Mediterranean basin. The major pollen allergens of both plants, Pla I 1 and Ole e 1, share 38.7% of their amino acid sequences. OBJECTIVE: To analyze putative cross-reactivity between these 2 proteins. METHODS: Several antibodies and patients' sera were used in immunoblot and immunocytochemistry experiments. RESULTS: Two anti-Pla I 1 antibodies were able to bind to 3 polypeptides from olive pollen protein extracts, which correspond to the 3 glycosylation isoforms of Ole e 1 (18-22 kDa) previously described. Moreover, Pla I 1 protein was found in the cytoplasm of both the vegetative and the generative cells of P lanceolata mature pollen. On olive pollen sections, these anti-Pla I 1 antibodies displayed significant labeling in the cytoplasm of the vegetative cell and in both the exine and the material adhering to this outer layer of the pollen wall. In addition, the anti-Ole e 1 antibody 10H1 was found to cross-react with proteins of similar masses (16-20 kDa) to Pla I 1 variants. In Plantago pollen sections, the 10H1 antibody recognized proteins located in the cytoplasm of both the vegetative and generative cells. Cross-reaction was confirmed using sera from patients allergic to either plant pollen. CONCLUSION: Both allergens share common epitopes, which can be cross-recognized by different antibodies and sera from different patients, although this antigenic similarity seems to have little clinical relevance.

Mercury toxicity in the Amazon: contrast sensitivity and color discrimination of subjects exposed to mercury.

We measured visual performance in achromatic and chromatic spatial tasks of mercury-exposed subjects and compared the results with norms obtained from healthy individuals of similar age. Data were obtained for a group of 28 mercury-exposed subjects, comprising 20 Amazonian gold miners, 2 inhabitants of Amazonian riverside communities, and 6 laboratory technicians, who asked for medical care. Statistical norms were generated by testing healthy control subjects divided into three age groups. The performance of a substantial proportion of the mercury-exposed subjects was below the norms in all of these tasks. Eleven of 20 subjects (55%) performed below the norms in the achromatic contrast sensitivity task. The mercury-exposed subjects also had lower red-green contrast sensitivity deficits at all tested spatial frequencies (9/11 subjects; 81%). Three gold miners and 1 riverine (4/19 subjects, 21%) performed worse than normal subjects making more mistakes in the color arrangement test. Five of 10 subjects tested (50%), comprising 2 gold miners, 2 technicians, and 1 riverine, performed worse than normal in the color discrimination test, having areas of one or more MacAdam ellipse larger than normal subjects and high color discrimination thresholds at least in one color locus. These data indicate that psychophysical assessment can be used to quantify the degree of visual impairment of mercury-exposed subjects. They also suggest that some spatial tests such as the measurement of red-green chromatic contrast are sufficiently sensitive to detect visual dysfunction caused by mercury toxicity.

Mercury toxicity in the Amazon: contrast sensitivity and color discrimination of subjects exposed to mercury

We measured visual performance in achromatic and chromatic spatial tasks of mercury-exposed subjects and compared the results with norms obtained from healthy individuals of similar age. Data were obtained for a group of 28 mercury-exposed subjects, comprising 20 Amazonian gold miners, 2 inhabitants of Amazonian riverside communities, and 6 laboratory technicians, who asked for medical care. Statistical norms were generated by testing healthy control subjects divided into three age groups. The performance of a substantial proportion of the mercury-exposed subjects was below the norms in all of these tasks. Eleven of 20 subjects (55 percent) performed below the norms in the achromatic contrast sensitivity task. The mercury-exposed subjects also had lower red-green contrast sensitivity deficits at all tested spatial frequencies (9/11 subjects; 81 percent). Three gold miners and 1 riverine (4/19 subjects, 21 percent) performed worse than normal subjects making more mistakes in the color arrangement test. Five of 10 subjects tested (50 percent), comprising 2 gold miners, 2 technicians, and 1 riverine, performed worse than normal in the color discrimination test, having areas of one or more MacAdam ellipse larger than normal subjects and high color discrimination thresholds at least in one color locus. These data indicate that psychophysical assessment can be used to quantify the degree of visual impairment of mercury-exposed subjects. They also suggest that some spatial tests such as the measurement of red-green chromatic contrast are sufficiently sensitive to detect visual dysfunction caused by mercury toxicity.

Mapping and pyramiding of qualitative and quantitative resistance to stripe rust in barley.

The identification and location of sources of genetic resistance to plant diseases are important contributions to the development of resistant varieties. The combination of different sources and types of resistance in the same genotype should assist in the development of durably resistant varieties. Using a doubled haploid (DH), mapping population of barley, we mapped a qualitative resistance gene ( Rpsx) to barley stripe rust in the accession CI10587 (PI 243183) to the long arm of chromosome 1(7H). We combined the Rpsx gene, through a series of crosses, with three mapped and validated barley stripe rust resistance QTL alleles located on chromosomes 4(4H) (QTL4), 5(1H) (QTL5), and 7(5H) (QTL7). Three different barley DH populations were developed from these crosses, two combining Rpsx with QTL4 and QTL7, and the third combining Rpsx with QTL5. Disease severity testing in four environments and QTL mapping analyses confirmed the effects and locations of Rpsx, QTL4, and QTL5, thereby validating the original estimates of QTL location and effect. QTL alleles on chromosomes 4(4H) and 5(1H) were effective in decreasing disease severity in the absence of the resistance allele at Rpsx. Quantitative resistance effects were mainly additive, although magnitude interactions were detected. Our results indicate that combining qualitative and quantitative resistance in the same genotype is feasible. However, the durability of such resistance pyramids will require challenge from virulent isolates, which currently are not reported in North America.

Localization of transcripts corresponding to the major allergen from olive pollen (Ole e I) by electron microscopic non-radioactive in situ RT-PCR.

In situ reverse transcription-PCR of mRNAs corresponding to the olive major allergen (Ole e I) has been tested at the ultrastructural level in mature olive pollen. The transcripts were present in the cytoplasm of both the vegetative and the generative cells, frequently associated to ribosomes in the endoplasmic reticulum. No labeling was detected in the pollen wall, nor in vacuoles, lipid bodies, plastids or mitochondria. Localization of the major olive allergen at ultrastructural level showed the protein present mainly in the lumen of the endoplasmic reticulum vesicles or pockets scattered in the cytoplasm, and in the outer region of the pollen exine. The results confirm the rough endoplasmic reticulum as the cell system involved in both the synthesis and storage of this protein. This is the first report of in situ RT-PCR on plant material at the ultrastructural level. The method described for mRNA amplification and detection is confirmed as a valuable tool for studying gene expression in plant material.

Ability of three root-end filling materials to prevent bacterial leakage.

This study evaluated the ability of three materials--a resinous root canal sealer (Sealer 26) prepared in a thick consistence, a reinforced zinc oxide-eugenol cement (IRM), and a glass-ionomer cement (Fuji IX)--in preventing bacterial leakage. Retrofilled teeth were mounted in an apparatus and then challenged by human saliva. The number of days required for the bacteria from saliva to penetrate the root-end filling materials was determined. Evaluation was conducted for 60 days. Leakage was observed in all teeth of the Fuji IX group, and in 95% (19 of 20 specimens) of the teeth retrofilled with IRM. Sixty-five percent (13 of 20 teeth) of the teeth retrofilled with Sealer 26 showed leakage. No difference was detected between Fuji IX and IRM (p > 0.05). However Sealer 26 was significantly more effective in preventing bacterial leakage when compared with other materials tested (p < 0.05).