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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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All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Structural basis for preferential binding of human TCF4 to DNA containing 5-carboxylcytosine

The psychiatric risk-associated transcription factor 4 (TCF4) is linked to schizophrenia. Rare TCF4 coding variants are found in individuals with Pitt-Hopkins syndrome—an intellectual disability and autism spectrum disorder. TCF4 contains a C-terminal basic-helix-loop-helix (bHLH) DNA binding domain which recognizes the enhancer-box (E-box) element 5'-CANNTG-3' (where N = any nucleotide). A subset of the TCF4-occupancy sites have the expanded consensus binding specificity 5'-C(A/G)-CANNTG-3', with an added outer Cp(A/G) dinucleotide; for example in the promoter for CNIH3, a gene involved in opioid dependence. In mammalian genomes, particularly brain, the CpG and CpA dinucleotides can be methylated at the 5-position of cytosine (5mC), and then may undergo successive oxidations to the 5-hydroxymethyl (5hmC), 5-formyl (5fC), and 5-carboxyl (5caC) forms. We find that, in the context of 5'- 0 CG- 1 CA- 2 CG- 3 TG-3'(where the numbers indicate successive dinucleotides), modification of the central E-box 2 CG has very little effect on TCF4 binding, E-box 1 CA modification has a negative influence on binding, while modification of the flanking 0 CG, particularly carboxylation, has a strong positive impact on TCF4 binding to DNA. Crystallization of TCF4 in complex with unmodified or 5caC-modified oligonucleotides revealed that the basic region of bHLH domain adopts multiple conformations, including an extended loop going through the DNA minor groove, or the N-terminal portion of a long helix binding in the DNA major groove. The different protein conformations enable arginine 576 (R576) to interact, respectively, with a thymine in the minor groove, a phosphate group of DNA backbone, or 5caC in the major groove. The Pitt-Hopkins syndrome mutations affect five arginine residues in the basic region, two of them (R569 and R576) involved in 5caC recognition. Our analyses indicate, and suggest a structural basis for, the preferential recognition of 5caC by a transcription factor centrally important in brain development.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

Symposium NM09: Novel Approaches and Material Platforms for Plasmonics and Metamaterials

The goal of this symposium was to present through a series of invited lectures from world-leading experts in the field, an overview of the current state-of-the-art in nanophotonics over a broad swath of topics, ranging from metal-based plasmonics to dielectric species. It was focused on investigations into novel resonator designs and into alternative materials. Over the 10 years it has been held, this symposium has provided an excellent education forum to participating students and postdocs through the direct interaction with world-renowned researchers, the opportunity to present their research results in both poster and oral form, the full-day tutorial session before the conference, and in listening to the results of other research groups. DOE funding provided need-based travel support to students and invited speakers who had financial difficulties in participating in the MRS meeting. The organizers made every effort to publicize the available support and were strongly committed to encourage participation from under-represented groups including women and minorities. The organizers are grateful to DOE for its support.

36 MATERIALS SCIENCE↗
NASA NTRS2002

Long Term Manipulations of Intact Microbial Mat Communities in a Greenhouse Collaboratory: Simulating Earth's Present and Past Field Environments

Photosynthetic microbial mat communities were obtained from marine hypersaline saltern ponds, maintained in a greenhouse facility, and examined for the effects of salinity variations. Because these microbial mats are considered to be useful analogs of equivalent ancient marine communities, they offer insights about evolutionary events during the greater than 3 billion year time interval wherein mats co-evolved with Earth's geosphere and atmosphere. Although photosynthetic mats can be highly dynamic and exhibit extremely high activity, the mats in the present study have been maintained for more than one year with relatively minor changes. The major groups of microorganisms, as assayed using microscopic, genetic, and biomarker methodologies, are essentially the same as those in the original field samples. Field and greenhouse mats were similar with respect to rates of exchange of oxygen and dissolved inorganic carbon across the mat-water interface, both during the day and at night. Field and greenhouse mats exhibited similar rates of efflux of methane and hydrogen. Manipulations of salinity in the water overlying the mats produced changes in the community that strongly resemble those observed in the field. A collaboratory testbed and an array of automated features are being developed to support remote scientific experimentation with the assistance of intelligent software agents. This facility will permit teams of investigators to explore ancient environmental conditions that are rare or absent today but might have influenced the early evolution of these photosynthetic ecosystems.

Bebout, Brad↗
DOE OSTI2011

Controlling Non-Covalent Interactions to Modulate the Dispersion of Fullerenes in Polymer Nanocomposites

Polymer nanocomposites (PNCs) are materials based on a class of filled plastics that contain relatively small amounts of nanoparticles, which can impart improved structural, mechanical, and thermal properties relative to the neat polymer. However, the homogeneous dispersion of the nanoparticles into a polymer matrix is critical and an impeding factor for the controlled enhancement of PNC properties. In this work, we provide new insight into the importance of polymer chain connectivity and nanoparticle shape and curvature on the formation of noncovalent electron donoracceptor (EDA) interactions between polymers and nanoparticles. This is accomplished by experimentally monitoring the dispersion of nanoparticles in copolymers containing varying amounts of functional moieties that can form noncovalent interactions with carbon nanoparticles with corroboration through density functional calculations. The results show that the presence of a minority of interacting functional groups within a polymer chain leads to an optimum interaction between the polymer and fullerene. Density functional theory calculations that identify the binding energy and geometry of the interaction between the functional monomers and fullerenes correspond very well with the experimental results. Moreover, comparison of these results to similar studies with single-walled carbon nanotubes (SWNT) indicate a distinct difference in the ability of EDA interactions to improve the dispersion of fullerenes relative to their impact on SWNT. Thus, the polymer chain connectivity, the polymer chain conformation, and size and shape of the nanoparticle modulate the formation of intermolecular interactions and directly impact the dispersion of the resultant nanocomposite.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2011

Controlling Non-Covalent Interactions to Modulate the Dispersion of Fullerenes in Polymer Nanocomposites

Polymer nanocomposites (PNCs) are materials based on a class of filled plastics that contain relatively small amounts of nanoparticles, which can impart improved structural, mechanical, and thermal properties relative to the neat polymer. However, the homogeneous dispersion of the nanoparticles into a polymer matrix is critical and an impeding factor for the controlled enhancement of PNC properties. In this work, we provide new insight into the importance of polymer chain connectivity and nanoparticle shape and curvature on the formation of noncovalent electron donor-acceptor (EDA) interactions between polymers and nanoparticles. This is accomplished by experimentally monitoring the dispersion of nanoparticles in copolymers containing varying amounts of functional moieties that can form noncovalent interactions with carbon nanoparticles with corroboration through density functional calculations. The results show that the presence of a minority of interacting functional groups within a polymer chain leads to an optimum interaction between the polymer and fullerene. Density functional theory calculations that identify the binding energy and geometry of the interaction between the functional monomers and fullerenes correspond very well with the experimental results. Moreover, comparison of these results to similar studies with single-walled carbon nanotubes (SWNT) indicate a distinct difference in the ability of EDA interactions to improve the dispersion of fullerenes relative to their impact on SWNT. Thus, the polymer chain connectivity, the polymer chain conformation, and size and shape of the nanoparticle modulate the formation of intermolecular interactions and directly impact the dispersion of the resultant nanocomposite.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2015

Spine stereotactic body radiation therapy plans: Achieving dose coverage, conformity, and dose falloff

We report our experience of establishing planning objectives to achieve dose coverage, conformity, and dose falloff for spine stereotactic body radiation therapy (SBRT) plans. Patients with spine lesions were treated using SBRT in our institution since September 2009. Since September 2011, we established the following planning objectives for our SBRT spine plans in addition to the cord dose constraints: (1) dose coverage—prescription dose (PD) to cover at least 95% planning target volume (PTV) and 90% PD to cover at least 99% PTV; (2) conformity index (CI)—ratio of prescription isodose volume (PIV) to the PTV < 1.2; (3) dose falloff—ratio of 50% PIV to the PTV (R{sub 50%}); (4) and maximum dose in percentage of PD at 2 cm from PTV in any direction (D{sub 2cm}) to follow Radiation Therapy Oncology Group (RTOG) 0915. We have retrospectively reviewed 66 separate spine lesions treated between September 2009 and December 2012 (31 treated before September 2011 [group 1] and 35 treated after [group 2]). The χ{sup 2} test was used to examine the difference in parameters between groups. The PTV V{sub 100%} {sub PD} ≥ 95% objective was met in 29.0% of group 1 vs 91.4% of group 2 (p < 0.01) plans. The PTV V{sub 90%} {sub PD} ≥ 99% objective was met in 38.7% of group 1 vs 88.6% of group 2 (p < 0.01) plans. Overall, 4 plans in group 1 had CI > 1.2 vs none in group 2 (p = 0.04). For D{sub 2cm}, 48.3% plans yielded a minor violation of the objectives and 16.1% a major violation for group 1, whereas 17.1% exhibited a minor violation and 2.9% a major violation for group 2 (p < 0.01). Spine SBRT plans can be improved on dose coverage, conformity, and dose falloff employing a combination of RTOG spine and lung SBRT protocol planning objectives.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2024

Dilute alloy catalysts for electrochemical CO 2 reduction

A product includes a dilute alloy catalyst for carbon dioxide reduction. The catalyst has a majority component and at least one minority component. The majority component is present in a concentration of greater than 90 atomic percent of the catalyst. The majority component is copper, and each minority component is selected from the group consisting of: a transition metal, a main group metal, a lanthanide, and a semimetal. A method includes forming a product on a cathode. The product includes a dilute alloy catalyst for carbon dioxide reduction. The catalyst has a majority component and at least one minority component. The majority component is present in a concentration of greater than 90 atomic percent of the catalyst. The majority component is copper, and each minority component is selected from the group consisting of: a transition metal, a main group metal, a lanthanide, and a semimetal.

Biener, Juergen↗
DOE OSTI2020

Activation and surface reactions of CO and H 2 on ZnO powders and nanoplates under CO hydrogenation reaction conditions

Here, activation and surface reactions of CO and H 2 on ZnO powders and nanoplates under CO hydrogenation reaction conditions were (quasi) in situ studied using temperature programmed surface reaction spectra, diffuse reflectance Fourier transform infrared spectroscopy, inelastic neutron scattering spectroscopy and electron paramagnetic resonance. CO undergoes disproportion reaction to produce gaseous CO 2 and surface carbon adatoms, and adsorbs to form surface formate species. H 2 adsorption forms dominant irreversibly-adsorbed surface hydroxyl groups and interstitial H species and very minor surface Zn-H species. Surface formate species and hydroxyl groups react to produce CO 2 and H 2 , while surface carbon adatoms are hydrogenated by surface Zn-H species sequentially to produce CH(a), CH 2 (a), CH 3 (a) and eventually gaseous CH 4 . The ZnO nanoplates, exposing a higher fraction of Zn-ZnO(0001) and O-ZnO(000–1) polar facets, are more active than the ZnO powders to catalyze CO hydrogenation to CH 4 . These results provide fundamental understanding of the reaction mechanisms and structural effects of CO hydrogenation reaction catalyzed by ZnO-based catalysts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Uterine Artery Embolization to Treat Uterine Adenomyosis with or without Uterine Leiomyomata: Results of Symptom Control and Health-Related Quality of Life 40 Months after Treatment

Purpose: To evaluate the clinical outcome for uterine adenomyosis with or without uterine leiomyomata 40 months after uterine artery embolization (UAE). Methods: Forty women aged 39-56 years (median 46 years) with symptomatic uterine adenomyosis and magnetic resonance imaging findings of uterine adenomyosis with or without combined uterine leiomyomata underwent UAE. Self-perceived changes in clinical symptoms were assessed, and residual symptom severity and health-related quality of life (HRQOL) after UAE were evaluated. Clinical failure was defined as no symptomatic improvement or second invasive therapy after UAE. Results were stratified by the extent of uterine adenomyosis at baseline magnetic resonance imaging. Results: Patients were followed for a median of 40 months (range 5-102 months). UAE led to symptomatic control after UAE in 29 (72.5%) of 40 patients while 11 women underwent hysterectomy (n = 10) or dilatation and curettage (n = 1) for therapy failure. No significant difference between women with pure uterine adenoymosis and women with uterine adenomyosis combined with uterine leiomyomata was observed. Best results were shown for UAE in uterine adenomyosis with uterine leiomyomata predominance as opposed to predominant uterine adenomyosis with minor fibroid disease (clinical failure 0% vs. 31.5%, P = 0.058). Throughout the study group, HRQOL score values increased and symptom severity scores decreased after UAE. Least improvement was noted for women with pure adenomyosis. Conclusions: UAE is clinically effective in the long term in most women with uterine adenomyosis. Symptomatic control and HRQOL were highest in patients with combined disease of uterine adenomyosis but leiomyomata predominance.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2012

The Transmutation of Nuclear Waste in the Two-Zone Subcritical System Driven by High- Intensity Neutron Generator - 12098

The main problems of transmutation of high-level radioactive waste (minor actinides and long-lived fission products) are considered in our work. The range of radioactive waste of nuclear power is analyzed. The conditions under which the transmutation of radioactive waste will be most effective are analyzed too. The modeling results of a transmutation of the main radioactive isotopes are presented and discussed. The transmutation of minor actinides and long-lived fission products are modeled in our work (minor actinides - Np-237, Am-241, Am-242, Am-243, Cm-244, Cm-245; long-lived fission products - I-129, Tc-99). The two-zone subcritical system is calculated with help of different neutron-physical codes (MCNP, Scale, Montebarn, Origen). The ENDF/B-VI nuclear data library used in above calculations. Thus, radioactive wastes can be divided into two main groups that need to be transmuted. The minor actinides form the first group and the long-lived fission products form the second one. For the purpose of effective transmutation these isotopes must be extracted from the spent nuclear fuel with the help of either PUREX technology or pyrometallurgical technology. The two-zone reactor system with fast and thermal regions is more effective for nuclear waste transmutation than the one-zone reactor. Modeling results show that nearly all radioactive wastes can be transmuted in the two-zone subcritical system driven by a high-intensity neutron generator with the external neutron source strength of 1.10{sup 13} n/sec. Obviously, transmutation rate will increase with a rise of the external neutron source strength. From the results above we can also see that the initial loading of radioactive isotopes into the reactor system should exceed by mass those isotopes that are finally produced. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2022

Spectroscopic investigation of historical uranium glasses

Here, we present spectroscopic investigations of uranium in two historical glasses. A 1920's-1930's Art Deco (Bagley Carnival) green soda-lime-silica uranium glass bowl and a 1930's-1940's (Thomas Webb) yellow full lead crystal uranium glass vase were studied using optical absorption spectroscopy, XRF and SEM-EDX, X-band EPR and High- Energy Resolution Fluorescence-Detected (HERFD)-XANES. Uranium speciation may be different in the two glasses. Uranium occurs as uranyl groups (UO 2 2+ ) with minority reduced uranium species, mostly as U(V), more important in the Webb glass than in the Bagley glass. The differences between the two glasses arise from the fining procedure and result from the presence of other multivalent elements and differences in base glass composition. Electron Paramagnetic Resonance (EPR) spectra show the presence of an incipient signal close to g~2, partially annealed by heating to 550 °C, which we assign to a small concentration of radiation-induced defects caused by uranium decay. The presence of multivalent glass components in addition to U (As + Cu + Fe in the Bagley glass and Sb + Fe in the Webb glass) can trap the electron-hole pairs generated by the presence of uranium. This may explain the weakness of this signal in these glasses that anyway received a limited radiation dose since their fabrication. The low activity of these glasses, close to the background radiation, confirms that there is no danger to exhibiting them in museums.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Toward a Diverse Next-Generation Energy Workforce: Teaching Artificial Photosynthesis and Electrochemistry in Elementary Schools through Active Learning

Artificial photosynthesis is a promising approach to generate commodity chemicals using abundant chemical feedstocks and renewable energy sources. Despite its importance, affordable and effective hands-on classroom activities that demonstrate artificial photosynthesis and teach key concepts, especially for primary school students, are lacking. Educating young students on this topic is a critical step in the development of the next-generation energy workforce, especially one that is diverse in race and gender. Here, we hypothesize that an effective approach to educate a broad range of young students on the topic of artificial photosynthesis is through the use of an active learning-based lesson plan that employs cheap and accessible materials. This hypothesis is confirmed by evaluating the understanding of fifth grade students with a survey before and after a lesson plan on artificial photosynthesis that uses active-learning techniques and uses safe and highly accessible materials (baking soda, tap water, plastic jars, Ni coil, alligator clips, and a solar cell) to perform solar-powered water splitting. The lesson plan and survey questions are designed to align with the educational outcomes for fifth grade classrooms in California and to address four general learning objectives: (1) Motivations of Artificial Photosynthesis, (2) Applications of Artificial Photosynthesis, (3) Inputs and Outputs of Artificial Photosynthesis, and (4) Engineering Design for Artificial Photosynthesis. The survey data demonstrate a statistically significant improvement in overall student understanding from the lesson plan. Importantly, the data show that the lesson plan presented here is effective at narrowing the performance gap between minority students and overly represented groups.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Using Time-of-Flight SIMS to Investigate Group V Dopant Distribution in CdTe

Enabling continued development of polycrystalline CdTe solar cells with open-circuit voltages approaching 1 V requires new dopants and processes to increase acceptor concentrations and minority-carrier lifetimes. We have investigated multiple Group V dopants in single- and polycrystalline CdTe materials as well as Cl, using numerous dopant incorporation and activation strategies. The diffusion kinetics and spatial distribution of the dopants are revealed with a combination of 1-D standard depth-profiling and high-resolution 3-D tomography with time-of-flight secondary-ion mass spectrometry. For all cases where the dopant is incorporated during growth, including vapor-transport deposition, closespaced sublimation, and molecular-beam epitaxy, the dopant concentration is not enhanced at grain boundaries. When the dopant is incorporated through a post-growth incorporation process, fast grain-boundary diffusion leads to an enhanced dopant concentration at grain boundaries. Although both methods are applicable, in-situ incorporation offers control of dopants and devices independent of diffusion kinetics, grain structure, and grain-boundary chemistry.

14 SOLAR ENERGY↗
DOE OSTI2018

Chemical Degradation Pathways in Siloxane Polymers Following Phenyl Excitations

We use ensembles of quantum-based molecular dynamics simulations to predict the chemical reactions that follow radiation-induced excitations of phenyl groups in a model copolymer of polydimethylsiloxane and polydiphenylsiloxane. Our simulations span a wide range of highly porous and condensed phase densities and include both wet and dry conditions. We observe that in the absence of water, excited phenyl groups tend to abstract hydrogen from other methyl or phenyl side groups to produce benzene, with the under-hydrogenated group initiating subsequent intrachain cyclization reactions. These systems also yield minor products of diphenyl moieties formed by the complete abstraction of both phenyl groups from a single polydiphenylsiloxane subunit. In contrast, we find that the presence of water promotes the formation of free benzene and silanol side groups, reduces the likelihood for intrachain cyclization reactions, and completely suppresses the formation of diphenyl species. In addition, we predict that water plays a critical role in chain scission reactions, which indicates a possible synergistic effect between environmental moisture and radiation that could promote alterations of a larger polymer network. These results could have impact in interpreting accelerated aging experiments, where polymer decomposition reactions and network rearrangements are thought to have a significant effect on the ensuing mechanical properties.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Robotic-Assisted Versus Manual Prostatic Arterial Embolization for Benign Prostatic Hyperplasia: A Comparative Analysis

PurposeProstatic artery embolization (PAE) is a safe and efficacious procedure for benign prostatic hyperplasia (BPH), though is technically challenging. We present our experience of technical and clinical outcomes of robotic and manual PAE in patients with BPH.Materials and MethodsIRB-approved retrospective study of 40 consecutive patients 49–81 years old with moderate or severe grade BPH from May 2014 to July 2015: 20 robotic-assisted PAE (group 1), 20 manual PAE (group 2). Robotic-assisted PAE was performed using the Magellan Robotic System. American Urological Association (AUA-SI) score, cost, technical and clinical success, radiation dose, fluoroscopy, and procedure time were reviewed. Statistical analysis was performed within and between each group using paired t test and one-way analysis of variance respectively, at 1 and 3 months.ResultsNo significant baseline differences in age and AUA-SI between groups. Technical success was 100% (group 1) and 95% (group 2). One unsuccessful subject from group 2 returned for a successful embolization using robotic assistance. Fluoroscopy and procedural times were similar between groups, with a non-significant lower patient radiation dose in group 1 (30,632.8 mGy/cm{sup 2} vs 35,890.9, p = 0.269). Disposable cost was significantly different between groups with the robotic-assisted PAE incurring a higher cost (group 1 $4530.2; group 2 $1588.5, p < 0.0001). Clinical improvement was significant in both arms at 3 months: group 1 mean change in AUA-SI of 8.3 (p = 0.006), group 2: 9.6 (p < 0.0001). No minor or major complications occurred.ConclusionsRobotic-assisted PAE offers technical success comparable to manual PAE, with similar clinical improvement with an increased cost.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

Fusion Imaging Reduces Radiation and Contrast Medium Exposure During Endovascular Revascularization of Iliac Steno-Occlusive Disease

Introduction: To evaluate feasibility, safety and efficacy of fusion imaging in order to guide endovascular revascularization of iliac steno-occlusive disease. Materials and Methods: Retrospectively, we identified twenty-six patients (20 male, mean age 63 ± 8y; Rutherford II-V) who underwent revascularization of a chronic total occlusion (n = 6; 23%) or severe stenosis (n = 20; 77%) of the common and/or external iliac artery. Median lesion length was 33 mm (IQR 20–60). In one group of patients (NEW; n = 11), fusion imaging with 2-D/3-D registration was used to guide revascularization. No baseline digital subtraction angiography (DSA) had been acquired in these patients. In another group of patients (OLD; n = 15), no fusion imaging had been utilized and at least one DSA run had been performed to guide the procedure. In both groups, final DSA of the treated lesions was performed. Number of DSA runs, radiation and contrast medium exposure, technical success (residual stenosis < 30%) and complications were analyzed. Results: Median DSA runs needed in OLD for guidance were n = 2 (IQR 2–3) and in NEW n = 0 (IQR 0–0; p = 0.001). Compared to OLD, median dose area product (DAP) was reduced by 17,118 mGy*cm{sup 2} (IQR 10,407–23,614; p = 0.016) if fusion imaging guidance had been used (NEW). Based on the median DAP of the final angiogram in NEW, median DAP reduction was 6007 mGy*cm{sup 2} (IQR 5012–16,105; p = 0.1). Median total contrast medium volume injected in NEW was 45 ml (IQR 30–90) and in OLD 120 ml (IQR 100–140; p = 0.001). Technical success was 100% for both groups. In 1/27 patients (3.7%) a minor complication (embolism) occurred. Conclusion: Fusion imaging proved to be feasible as well as safe and significantly reduces radiation and contrast medium exposure during endovascular revascularization of iliac steno-occlusive disease.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2021

The Chemistry Graduate Student Experience: Findings from an ACS Survey

Graduate training is a key element in producing a scientific workforce that reflects the nation’s diversity. This paper examines data from a 2013 American Chemical Society (ACS) survey of 2,544 chemistry masters and doctoral students and reveals barriers to reaching this goal. Multivariate statistical analyses indicate that women reported significantly less supportive relationships with advisors. Women were less likely to plan to finish their degrees, and for PhD students, the discrepancy was larger for students at the start of their graduate program. Women were also less likely to pursue the next level of training, and the gender difference related to postdoctoral plans was greater for those who identified with a racial-ethnic group traditionally underrepresented in chemistry (underrepresented minority, URM). URM students who were beyond the first year of their graduate program reported significantly less supportive relationships with peers. They were also less likely to have funding sufficient to meet their needs and more often used personal resources including loans. Despite these difficulties, URM students were more likely to definitely plan to finish their degrees, and men who identified as URM were more likely to plan to pursue postdoctoral work. Independent of gender and identification as URMs, students in more highly ranked schools reported less advisor support. Extensive open-ended comments indicated that large proportions of the students desired more attention and meaningful feedback from advisors and changes within their programs to promote support for students and advisor accountability. Suggestions for future research are given, and a companion commentary discusses needed directions for change.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Modifications under irradiation of a self-assembled monolayer grafted on a nano-porous silica glass: a solid-state NMR characterization

Controlled pore glasses with a pore size of 8 nm are grafted with chlorodimethylsilane (ClSi(CH{sub 3}){sub 2}H). The surface of the glass is carefully characterized before and after irradiation with 10 MeV electrons by solid-state NMR measurements. {sup 1}H MAS NMR experiments in one and two dimensions (2D double quantum and 2D exchange) have been used to reveal the grafting of the chlorodimethylsilane at the silica surface and evidence the formation of a homogeneous layer on the surface. Irradiation leads to a high H{sub 2} yield (3.3 * 10{sup -7} mol/J) due to the efficient cleavage of the Si H bond. Methane is detected in smaller quantities (5.5 * 10{sup -8} mol/J), indicating that the Si-H bond is preferentially cleaved over the Si-C bond. The H{sub 2} production arising from OH groups on the surface is very minor in comparison to the S- H and Si-C radiolysis. (authors)

36 MATERIALS SCIENCE↗