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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,369 records · Page 76
All sourcesNASA NTRSDOE OSTI
NASA NTRS1996

Skeletal response to corticosteroid deficiency and excess in growing male rats

The study was designed to investigate bone histomorphometric changes induced by corticosteroid deficiency and supplementation at different dose levels in the rat skeleton. Male rats were adrenalectomized (ADX) or sham-operated and divided into six groups. At 2 days after surgery, sham-operated control rats (CON + PLA) and one group of ADX rats (ADX + PLA) were implanted subcutaneously (s.c.) with placebo pellets. ADX rats in the remaining four groups (ADX + C25, ADX + C50, ADX + C100, and ADX + C300) were implanted sc with corticosterone pellets designed to release 25, 50, 100, or 300 mg of the hormone over a 60 day period. Each ADX rat was also implanted sc with an aldosterone pellet (2.5 mg) similarly designed to release its contents over the same time period. All rats were killed at 3 weeks after implantation of pellets. Terminal blood samples were collected for serum biochemistry and the proximal tibial metaphyses (PTM), tibial diaphyses, and first lumbar vertebrae (LV) were processed undecalcified for quantitative bone histomorphometry. A dose-dependent increase in serum corticosterone concentration was observed in ADX rats implanted with hormone pellets. In comparison to CON + PLA rats, ADX + PLA rats had lower cancellous bone volume associated with a stimulation in longitudinal bone growth, an increase in mineral apposition rate, and a trend for increased osteoclast and osteoblast surfaces in PTM. In contrast, cancellous bone of ADX + C25 rats was preserved at nearly the CON + PLA level. However, the higher doses of corticosterone increased cancellous bone mass, but decreased longitudinal bone growth and all indices of bone resorption and formation in a dose-dependent manner in PTM. Similar cancellous bone changes were observed in the LV of corticosterone-treated rats, with the exception of a lack of an hormonal effect on cancellous bone mass. In the tibial diaphysis, corticosterone inhibited periosteal bone formation in a dose-dependent manner, but did not affect cortical bone mass. The results indicate that corticosteroid deficiency induces cancellous osteopenia, whereas supplementation with a near physiologic dose of the hormone prevents this bone loss in ADX rats. Furthermore, corticosteroid excess inhibits bone growth and bone turnover in a dose-dependent manner, but does not induce cancellous osteopenia in growing male rats.

Non-NASA Center↗
NASA NTRS1992

Mechanisms of alpha 1-adrenergic vascular desensitization in conscious dogs

To investigate the mechanisms of alpha 1-adrenergic vascular desensitization, osmotic minipumps containing either saline (n = 9) or amidephrine mesylate (AMD) (n = 9), a selective alpha 1-adrenergic receptor agonist, were implanted subcutaneously in dogs with chronically implanted arterial and right atrial pressure catheters and aortic flow probes. After chronic alpha 1-adrenergic receptor stimulation, significant physiological desensitization to acute AMD challenges was observed, i.e., pressor and vasoconstrictor responses to the alpha 1-adrenergic agonist were significantly depressed (p < 0.01) compared with responses in the same dogs studied in the conscious state before pump implantation. However, physiological desensitization to acute challenges of the neurotransmitter norepinephrine (NE) (0.1 micrograms/kg per minute) in the presence of beta-adrenergic receptor blockade was not observed for either mean arterial pressure (MAP) (30 +/- 7 versus 28 +/- 5 mm Hg) or total peripheral resistance (TPR) (29.8 +/- 4.9 versus 28.9 +/- 7.3 mm Hg/l per minute). In the presence of beta-adrenergic receptor plus ganglionic blockade after AMD pump implantation, physiological desensitization to NE was unmasked since the control responses to NE (0.1 micrograms/kg per minute) before the AMD pumps were now greater (p < 0.01) than after chronic AMD administration for both MAP (66 +/- 5 versus 32 +/- 2 mm Hg) and TPR (42.6 +/- 10.3 versus 23.9 +/- 4.4 mm Hg/l per minute). In the presence of beta-adrenergic receptor, ganglionic, plus NE-uptake blockade after AMD pump implantation, desensitization was even more apparent, since NE (0.1 micrograms/kg per minute) induced even greater differences in MAP (33 +/- 5 versus 109 +/- 6 mm Hg) and TPR (28.1 +/- 1.8 versus 111.8 +/- 14.7 mm Hg/l per minute). The maximal force of contraction induced by NE in the presence or absence of endothelium was significantly decreased (p < 0.05) in vitro in mesenteric artery rings from AMD pump dogs compared with saline control dogs. Furthermore, alpha 1-adrenergic receptor density, as determined by [3H]prazosin binding in membrane preparations from vessels in the mesentery, was decreased (8.2 +/- 1.0 versus 18.4 +/- 1.4 fmol/mg protein, p < 0.001) without any change in Kd in the AMD pump dogs compared with the saline pump dogs.(ABSTRACT TRUNCATED AT 400 WORDS).

Non-NASA Center↗
DOE OSTI2024

Development of AlGaN‐Based Deep‐Ultraviolet Avalanche Photodetectors—Toward Their Intrinsic Characteristics

Al 0.6 Ga 0.4 N deep‐UV p–i–n avalanche photodiodes (APDs) are demonstrated grown by metalorganic chemical vapor deposition (MOCVD) on a (0001) c‐plane aluminum nitride (AlN) bulk substrate and fabricated both with and without an ion implantation process for mesa‐edge electric‐field termination. Three design considerations are taken into account: the optical absorption of the AlN bulk substrate, the photosensitivity of the APD, and the breakdown electric field. The MOCVD growth conditions of the AlGaN APD layers are optimized. Then, a detailed description of the seven device fabrication steps of the APDs is provided, which includes nitrogen ion implantation. The APDs fabricated by the ion implant process exhibit a dark‐current density under low reverse bias ≈1 × 10 −9 A cm −2 . This is one order of magnitude lower than the APD fabricated without ion implantation from the same wafer. The breakdown voltage of the APD is ≈−140 V. The calculated optical gain of the ion‐implanted APD beyond avalanche breakdown is ≈5.2 × 10 5 (current limited) and the device has an average zero‐bias photoresponse of ≈68 mA W −1 at a wavelength of 250 nm.

Jeong, Hoon [Department of Electronic Engineering ↗
DOE OSTI2012

Uterine Artery Embolization Combined with Local Methotrexate and Systemic Methotrexate for Treatment of Cesarean Scar Pregnancy with Different Ultrasonographic Pattern

Purpose: This study was designed to compare the effectiveness of systemic methotrexate (MTX) with uterine artery embolization (UAE) combined with local MTX for the treatment of cesarean scar pregnancy (CSP) with different ultrasonographic pattern, and to indicate the preferable therapy in CSP patients. Methods: The results of 21 CSP cases were reviewed. All subjects were initially administrated with systemic MTX (50 mg/m{sup 2} body surface area). UAE combined with local MTX was added to the patients who had failed systemic MTX. The transvaginal ultrasonography data were retrospectively assessed, and two different ultrasonographic patterns were found: surface implantation and deep implantation of amniotic sac. The management and its effectiveness for patients with the two ultrasonographic patterns were studied retrospectively. Ultrasound scan and serum {beta}-hCG were monitored during follow-up. Data were analyzed with the Student's t test. Results: Nine patients were successfully treated with systemic MTX. The remaining 12 cases were successfully treated with additional UAE combined with local MTX. According to the classification by Vial et al. of CSP on ultrasonography, most surface implanted CSPs (8/11, 72.7%) could be successfully treated with systemic MTX, whereas most deeply implanted CSPs (9/10, 90%) had failed systemic MTX but still could be successfully treated with additional UAE combined with local MTX. All patients recovered without severe side effects. Most patients with a future desire for reproduction achieved subsequent pregnancy. Conclusions: For CSP patients suitable for nonsurgical treatment, UAE combined with local MTX would be the superior option compared with systemic MTX in the cases with deep implantation of amniotic sac.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2018

Molecular and histological study on the effects of non-thermal irreversible electroporation on the liver

Highlights: • Hepatocytes completely disintegrate within 6 h after NTIRE, TUNEL stain is seen as a diffuse stain throughout the treated volume 6 h after NTIRE. • The extracellular matrix in the treated volume is intact after NTIRE. • Hepatocytes, normal and bi-nucleated, are seen in the treated volume, 24 h after NTIRE. • Cleaved caspase-3 is actually downregulated after NTIRE. • Cleaved caspase-1, gasdermin D, RIP3 and MLKL are upregulated 6 h, and downregulated 24 h after NTIRE. Non-thermal irreversible electroporation (NTIRE) is a biophysical phenomenon in which certain electric fields delivered across the cell membrane in tissue, cause cell death, without affecting the extracellular matrix. “Minimally invasive regenerative surgery” is a new medical modality for treatment of end-stage organ or tissue failure in which exogenous cells are implanted in a decellularized niche in tissue, formed by the delivery of NTIRE electric fields across a targeted volume of tissue. We anticipate that the success of the procedure will depend on the time of implantation relative to the application of NTIRE. This study was performed to elucidate the histological and molecular events that occur within 24 h after NTIRE, in the context of optimal criteria for the time of implantation. To this end, we examined the histology of NTIRE treated rat liver with H&E, Masson trichrome and TUNEL staining. Western blot was used to examine pro and cleaved caspase-3 (marker for apoptosis), pro and cleaved caspase-1 and gasdermin D (markers for pyroptosis), and RIP3 and MLKL (markers for necroptosis). The key findings are that, complete hepatocytes disintegration within an intact extracellular matrix is seen at 6 h and, new hepatocytes are seen in the treated region at 24 h, after NTIRE. There is no evidence of apoptotic cell death from NTIRE, contrary to commonly made claims in the NTIRE literature. However, molecular pathways of pyroptosis and necroptosis, programed necrosis associated with inflammation, are activated at 6 h after NTIRE and are not evident at 24 h after NTIRE. These are fundamental new findings of basic value to the field of NTIRE in all its applications. Taken together the results suggest the hypothesis that an optimal time for implantation is about 24 h after NTIRE. Future studies in which exogenous cells are implanted at different times after NTIRE are required to examine this hypothesis.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

β-particle energy-summing correction for β-delayed proton emission measurements

One common approach to studying β-delayed proton emission is to measure the energy of the emitted proton and corresponding nuclear recoil in a double-sided silicon-strip detector (DSSD) after implanting the β-delayed proton-emitting (βp) nucleus. However, in order to extract the proton-decay energy, the measured energy must be corrected for the additional energy implanted in the DSSD by the β-particle emitted from the βp nucleus, an effect referred to here as β-summing. Here, we present an approach to determine an accurate correction for β-summing. Our method relies on the determination of the mean implantation depth of the βp nucleus within the DSSD by analyzing the shape of the total (proton + recoil + β) decay energy distribution shape. We validate this approach with other mean implantation depth measurement techniques that take advantage of energy deposition within DSSDs upstream and downstream of the implantation DSSD.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2013

Effect of the substrate orientation on the formation of He-plates in Si

The effect of the crystalline orientation on the implantation-induced strain/stress and on the formation of He-plates was studied by combining high-resolution X-ray scattering and transmission electron microscopy. The highest strains are obtained in (001)-oriented implanted substrates regardless of the fluence and of the channeling effects. The anisotropic properties of the silicon that generate an anisotropic elastic response of the substrate were taken into account to explain these different values of strain. Upon specific thermal annealing, it is shown that the formation of He-plates occurs only in the (001) habit planes regardless of the orientation of the substrates, non-tilted and tilted (001)-, (110)-, and (111)-substrates. Moreover, the distribution of He-plates in the (001) variants was found to be strongly dependent on the angle of the habit plane with the surface and on the intensity of the implantation-induced strain/stress. The implantation-induced stress thus favors the formation of He-plates in specific planes (of low angle with the surface) forming different defect configurations. The nucleation and growth of He-plates are thus discussed with regard to the implantation-induced stress.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Local traps as nanoscale reaction-diffusion probes: B clustering in c-Si

A series of B implantation experiments into initially amorphized and not fully recrystallized Si, i.e., into an existing a/c-Si bi-layer material, have been conducted. We varied B dose, energy, and temperature during implantation process itself. Significant B migration has been observed within c-Si part near the a/c-interface and near the end-of-range region before any activation annealing. We propose a general concept of local trapping sites as experimental probes of nanoscale reaction-diffusion processes. Here, the a/c-Si interface acts as a trap, and the process itself is explored as the migration and clustering of mobile BI point defects in nearby c-Si during implantation at temperatures from 77 to 573 K. We find that at room temperature—even at B concentrations as high as 1.6 atomic %, the key B-B pairing step requires diffusion lengths of several nm owing to a small, ∼0.1 eV, pairing energy barrier. Thus, in nanostructures doped by ion implantation, the implant distribution can be strongly influenced by thermal migration to nearby impurities, defects, and interfaces.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Development of known-fate survival monitoring techniques for juvenile wild pigs (Sus scrofa)

ContextWild pigs are an invasive species linked to numerous negative impacts on natural and anthropogenic ecosystems in many regions of the world. Robust estimates of juvenile wild pig survival are needed to improve population dynamics models to facilitate management of this economically and ecologically important invasive species. Despite this critical knowledge gap, to date no successful known-fate study of wild piglet survival (<5 months of age) has been conducted, due to a lack of appropriate method for this species.AimsTo aid in locating and tagging neonates, we piloted the use of vaginal implant transmitters (VITs) in adult wild pigs and evaluated average retention times of stud ear-tag transmitters, clip ear-tag transmitters, sutured and epoxied transmitters, harness transmitters, and surgically implanted transmitters to monitor known-fate survival of piglets.MethodsWe captured pregnant female pigs and implanted them with VITs. We tagged subsequently located neonates and piglets captured in traps with the aforementioned transmitters and monitored them to determine retention times and feasibility of each method.Key resultsVITs were effectively used to determine the location and time of wild pig parturition, allowing counting and tagging of neonate wild pigs. Stud ear-tag and abdominal implant transmitters were well retained by piglets weighing ≥3kg, in contrast to the other tested transmitters.ConclusionsStud ear-tag and abdominal implant transmitters allowed known-fate monitoring of juvenile wild pigs, although, of these, stud ear-tag transmitters may be more practical as they do not require field surgery on piglets. Due to their relatively large size, the stud ear tag transmitters were infeasible for monitoring of true neonates (~1kg); however, this application method may be suitable for neonates upon development of lighter-weight transmitters. The other transmitter attachment methods we tested were ineffective for monitoring of piglet survival, due to poor retention of transmitters.ImplicationsThe techniques piloted in this study will facilitate research into the reproductive ecology of wild pigs and known-fate studies of piglet mortality to aid in population modelling and evaluation of cause-specific mortality and factors affecting survival of these often-invasive animals.

Environmental Sciences & Ecology↗
DOE OSTI2015

Muscle segment homeobox genes direct embryonic diapause by limiting inflammation in the uterus

Embryonic diapause (delayed implantation) is a reproductive strategy widespread in the animal kingdom. Under this condition, embryos at the blastocyst stage become dormant simultaneously with uterine quiescence until environmental or physiological conditions are favorable for the survival of the mother and newborn. Under favorable conditions, activation of the blastocyst and uterus ensues with implantation and progression of pregnancy. Although endocrine factors are known to participate in this process, the underlying molecular mechanism coordinating this phenomenon is not clearly understood. We recently found that uterine muscle segment homeobox (Msx) transcription factors are critical for the initiation and maintenance of delayed implantation in mice. To better understand why Msx genes are critical for delayed implantation, we compared uterine proteomics profiles between littermate floxed (Msx1/Msx2f/f) mice and mice with uterine deletion of Msx genes (Msx1/Msx2d/d) under delayed conditions. In Msx1/Msx2d/d uteri, pathways including protein translation, ubiquitin-proteasome system, inflammation, chaperone-mediated protein folding, and endoplasmic reticulum (ER) stress were enriched, and computational modeling showed intersection of these pathways on inflammatory responses. Indeed, increases in the ubiquitin-proteasome system and inflammation conformed to proteotoxic and ER stress in Msx1/Msx2d/d uteri under delayed conditions. Interestingly, treatment with a proteasome inhibitor bortezomib further exacerbated ER stress in Msx1/Msx2d/d uteri with aggravated inflammatory response, deteriorating rate of blastocyst recovery and failure to sustain delayed implantation. This study highlights a previously unrecognized role for Msx in preventing proteotoxic stress and inflammatory responses to coordinate embryo dormancy and uterine quiescence during embryonic diapause.

embryonic diapause↗
DOE OSTI2019

Periodic Surface Morphology Characteristics of Tungsten Under Simultaneous Helium and Deuterium Bombardment at 30 keV

The ITER divertor will feature tungsten monoblocks as the plasma-facing component (PFC) that will be subject to extreme temperature and radiation environments. This paper reports the development of surface morphologies on tungsten under helium bombardment at high temperatures, which has important implications for safety, retention, and PFC erosion. Polycrystalline tungsten samples were implanted in the Dual Advanced Ion Simultaneous Implantation Experiment dual-beam ion implantation experiment at the University of Wisconsin-Madison with He-only and simultaneous He-D implantation at incidence angles of 55 deg, ion energies of 30 keV, and surface temperatures of 900°C to 1100°C. Morphologies resulting from angled incidence conditions differed from those produced under normal incidence bombardment at similar energy and temperature conditions in previous work. A variety of ordered and disordered morphologies dependent on grain orientation were observed for fluences up to 6 × 10 18 He cm –2 . These morphologies displayed dependencies on crystal orientation at low fluences and incident beam directions at higher fluences. Furthermore, these structures appeared, with variation, under both single-species He and mixed He-D implantations.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Nanocrystalline SiC and Ti 3 SiC 2 Alloys for Reactor Materials: Diffusion of Fission Product Surrogates

MAX phases, such as titanium silicon carbide (Ti 3 SiC 2 ), have a unique combination of both metallic and ceramic properties, which make them attractive for potential nuclear applications. Ti 3 SiC 2 has been suggested in the literature as a possible fuel cladding material. Prior to the application, it is necessary to investigate diffusivities of fission products in the ternary compound at elevated temperatures. This study attempts to obtain relevant data and make an initial assessment for Ti 3 SiC 2 . Ion implantation was used to introduce fission product surrogates (Ag and Cs) and a noble metal (Au) in Ti 3 SiC 2 , SiC, and a dual-phase nanocomposite of Ti 3 SiC 2 /SiC synthesized at PNNL. Thermal annealing and in-situ Rutherford backscattering spectrometry (RBS) were employed to study the diffusivity of the various implanted species in the materials. In-situ RBS study of Ti 3 SiC 2 implanted with Au ions at various temperatures was also performed. The experimental results indicate that the implanted Ag in SiC is immobile up to the highest temperature (1273 K) applied in this study; in contrast, significant out-diffusion of both Ag and Au in MAX phase Ti 3 SiC 2 occurs during ion implantation at 873 K. Cs in Ti 3 SiC 2 is found to diffuse during post-irradiation annealing at 973 K, and noticeable Cs release from the sample is observed. This study may suggest caution in using Ti 3 SiC 2 as a fuel cladding material for advanced nuclear reactors operating at very high temperatures. Further studies of the related materials are recommended.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Optimization of SiV Defect Yield in Diamond Substrates

Color centers (defect complexes such as SiV) in diamond have shown potential in fields ranging from metrology, cybersecurity to quantum computation. Demonstrations in these fields have pushed the envelope of state-of-the-art operations – for example, single photon sources (SPS) making use of SiV centers in diamond for quantum key distribution have demonstrated all the requirements for SPS operation including: (1) stable operation with second correlation function <<1, (2) electrically driven single photon emission and (3) compatibility with frequenc y conversion to telecommunication frequencies. To-date, however, all these demonstrations have been on lab-scale one-off devices. The key question behind how to deterministically fabricate these devices, namely activation yield has been overlooked. For context, Si based semiconductor devices are hugely successful because we have a high activation yield for implanted dopants. This is not yet true for diamond color centers. As currently understood, the color center yield is dominated by a lack of vacancies in the immediate area of the implantation. We propose to optimize the activation yield of color center using a combination of (1) focused single ion implantation with in-situ detection to count the number of implanted Si ions and (2) localized point defect (vacancy) creation using a focused Li ion beam to improve the yield. These experiments build on the unique capabilities of the SNL nanoImplanter (nI) to produce focused ion beam with spatial resolution of < 10 nm of both Si and Li ions. This work will also leverage our world-leading single ion implantation and detection capabilities.

36 MATERIALS SCIENCE↗
NASA NTRS1972

Development of GaAs solar cells

Solar cells and mesa diodes were fabricated by the implantation of zinc or beryllium ions into n-type gallium arsenide. Annealing temperatures above 750 C (zinc) or 650 C (beryllium) were found to produce 50% to 100% activation of the implanted ions. Junction depths of about 0.4 micron were produced by 600 keV zinc implants or 70 keV beryllium implants. P-layer sheet resistance was about 150 ohms for 2 x 10 to the 15th power cm/2 zinc or 1 x 10 to the 15th power cm/2 beryllium implants. This is sufficiently low for efficient solar cell fabrication. Contacting procedures were improved to yield reproducibly adherent, low resistance front and back contacts.

Source record↗
NASA NTRS1978

Development of pulsed processes for the manufacture of solar cells

The results of a 1-year program to develop the processes required for low-energy ion implantation for the automated production of silicon solar cells are described. The program included: (1) demonstrating state-of-the-art ion implantation equipment and designing an automated ion implanter, (2) making efforts to improve the performance of ion-implanted solar cells to 16.5 percent AM1, (3) developing a model of the pulse annealing process used in solar cell production, and (4) preparing an economic analysis of the process costs of ion implantation.

Minnucci, J. A.↗
NASA NTRS1992

Lunar Magnetic Fields: Implications for Resource Utilization

It is well known that solar-wind-implanted hydrogen and helium-3 in lunar soils are potentially usable resources for future manned activities. For economical mining of these implanted gases, it is desirable that relative concentrations exceed that of typical soils. It has previously been noted that the monthly variation of solar wind flux on the surface due to lunar immersion in the geomagnetic tail may have measurable consequences for resource utilization. It is pointed out that, for a constant external flux, locally strong lunar crustal magnetic fields will exert the dominant influence on solar wind volatile implantation rates. In particular, the strongest lunar crustal magnetic fields will both deflect and focus incident ions in local regions leading to local enhancements of the incident ion flux. Thus, the most economical sites for extraction of solar-wind-implanted volatiles may be within or adjacent to strong crustal magnetic fields. In addition, solar wind ion deflection by crustal magnetic fields must be considered in evaluating the issue of whether remnant cometary ice or water-bearing minerals have survived in permanently shadowed regions near the lunar poles. This is because sputter erosion of water ice by solar wind ions has been suggested to be an important ice loss mechanism within permanently shadowed regions. Thus, permanently shadowed regions that are also shielded from the solar wind by locally strong crustal fields could be the most promising locations for the survival of cometary ice. Additional numerical simulations are employed to show that solar wind ion deflection by strong lunar magnetic anomalies can produce local increases in the implantation rate of solar wind gases such as hydrogen.

Hood, L. L.↗
NASA NTRS2003

Intrauterine Pressure (IUP) Telemetry in Pregnant and Parturient Rats: Potential Applications for Spacecraft and Centrifugation Studies

Rats exposed to spaceflight or centrifugation from mid-to late pregnancy undergo either more or fewer labor contractions at birth, respectively, as compared to those in normal Earth gravity (1-g). In this paper, we report the development and validation of a new telemetric method for quantifying intrauterine pressure (IUP) in freely-moving, late pregnant and parturient rats. We plan to utilize this technique for studies of labor in altered gravity, specifically, to ascertain forces of uterine during birth, which we believe may be changed in micro- and hypergravity. The technique we describe yields precise, reliable measures of the forces experienced by rat fetuses during parturition. A small, surgically-implantable telemetric pressure sensor was fitted within a fluid-filled balloon. The total volume of the sensor-balloon assembly matched that of a full term rat fetus. Real-time videorecordings of sensor-implanted rat dams and non- implanted control dams enabled us to characterize effects of the intrauterine implant on behavioral aspects of parturition. Contraction frequency, duration, pup-to-pup birth intervals and pup-oriented activities of the dams measured during the peri-birth period were unaffected by the sensor implant. These findings establish intrauterine telemetry as a reliable, non-invasive technique for quantifying intrauterine pressures associated with parturition on Earth and in altered gravity environments. This new technology, readily amenable to spaceflight and centrifugation platforms, will enable us to answer key questions regarding the role of altered labor frequency labor in the adaptation of newborn mammals to hypo- and hypergravity.

Ronca, A. E.↗
DOE OSTI2012

Effect of H and He Irradiation on Cavity Formation and Blistering in Ceramics

Single- or poly-crystalline specimens of SiC, Si{sub 3}N{sub 4}, MgO, Al{sub 2}O{sub 3} and MgAl{sub 2}O{sub 4} were implanted with 0.4-1 MeV H{sup +} or He{sup +} ion beams at room temperature and 650 C up to fluences of {approx}1 x 10{sup 22}/m{sup 2}. This produced peak implanted gas and displacement damage levels as high as {approx}50 at.% and 34 displacements per atom (dpa). The specimens were subsequently examined optically, and in cross-section using transmission electron microscopy. Subsurface blistering occurred for specimens irradiated to H or He fluences greater than about 3 x 10{sup 21}/m{sup 2} ({approx}15 at.% peak implanted gas concentration), and surface exfoliation occurred for fluences above {approx}1 x 10{sup 22}/m{sup 2} ({approx}40 at.% implanted gas). Both helium and hydrogen had comparable effectiveness for inducing blistering and exfoliation on an atomic basis. The threshold blistering and exfoliation fluences for both ions were weakly dependent on temperature between 25 and 650 C. Both H and He were found to be very effective in inducing matrix cavity formation, due to their low solubility in these ceramics. The implanted gas concentrations that resulted in visible cavity formation generally ranged from 1 to 5 at.%. Visible cavity formation was readily induced during room temperature irradiation despite the limited vacancy mobility in these ceramics at room temperature. Three general types of cavity morphologies were observed: isolated cavities, clusters of small cavities (typically associated with dislocation loops), and two-dimensional platelets. Cavity formation was observed to initiate at the periphery of dislocation loops in some cases. During elevated temperature irradiation, cavity formation was often observed to be preferentially associated with certain low-index habit planes, particularly if the habit plane was oriented nearly parallel to the irradiated surface: (0001) and {l_brace}1{bar 1}00{r_brace} for Al{sub 2}O{sub 3}, (0001) for a-SiC, {l_brace}001{r_brace} and {l_brace}110{r_brace} for MgO, and {l_brace}110{r_brace} and {l_brace}111{r_brace} for MgAl{sub 2}O{sub 4}. The bubble formation and blistering behavior of the ceramics was similar to that observed in other studies of metals irradiated at comparable homologous temperatures. Ionization-induced diffusion effects associated with dual-beam light ion irradiation appeared to exert only a weak effect on cavity and dislocation loop growth compared to the single ion irradiation conditions.

08 HYDROGEN↗