Married women's response to spousal pornography use: A grounded theory

Empirical research suggests that married women may more commonly experience spousal pornography use as a relational attachment threat and are more likely to experience negative relational outcomes such as distress and loss of trust. The purpose of this study was to develop a grounded theory of married women's response to the discovery or disclosure of spousal pornography use. This study included the experiences of 30 married women who reported spousal pornography use as a threat to relational attachment, who chose to remain with their spouse, and who reported evidence of individual and relational healing thereafter. The research question, "How do married women describe the experience of learning of their spouse's pornography use and the individual and relationship sequelae that follow?" was explored using grounded theory methods to analyze deidentified blogpost accounts emphasizing response to a spouse's pornography use. The results describe a process model highlighting three interrelated informant categories-emotional response, mental response, and physical response-and one resultant category-behavioral response. Implications include (a) the importance of open communication regarding pornography use within relationships, (b) the necessity for individual and relational healing following betrayal trauma, and (c) the role of therapeutic intervention in shaping adaptive healing processes.

Humility in family relationships: Exploring how humility influences relationships in religious families

In this article, we explored how humility influences family relationships in religious families. We used a qualitative methodology and interviewed a religiously, ethnically, and geographically diverse sample of 198 highly religious families (N = 476). Family-level data were collected by using multiple informants through joint interviews with family members. Semistructured interviews regarding how religion influenced family life were conducted in the participants' homes. Interview transcripts were analyzed using qualitative data analysis software, team-based coding, and grounded theory procedures. Findings included four themes: (1) Pride as an obstacle to relational well-being, (2) the influence of religious beliefs on humility, (3) the influence of religious practices on humility, and (4) humility in practice. Together, these themes suggest that humility can be both grounding and empowering for individuals and relationships. Implications and future directions are discussed. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Change in Financial Stress and Relational Wellbeing During COVID-19: Exacerbating and Alleviating Influences

Guided by the family adjustment and adaptation response (FAAR) model and using a panel survey of 1510 adults in the US administered during the summer of 2020 and a mixed methods approach, we explored associations between changes in financial stress related to COVID-19 and relational wellbeing. Regression analyses showed that, compared to those who maintained their levels of financial stress, those who reported increased financial stress reported increased conflict and those who reported decreased financial stress reported decreased conflict. However, decreased financial stress was also associated with decreases in emotional closeness and relationship happiness, suggesting that changes in financial stress can lead to both maladaptation and bonadaptation in families. Qualitative findings provide insights into factors that may exacerbate or help alleviate financial stress related to COVID-19.

Predictive Mixing for Density Functional Theory (and Other Fixed-Point Problems)

Density functional theory calculations use a significant fraction of current supercomputing time. The resources required scale with the problem size, the internal workings of the code, and the number of iterations to convergence, with the latter being controlled by what is called "mixing". This paper describes a new approach to handling trust regions within these and other fixed-point problems. Rather than adjusting the trust region based upon improvement, the prior steps are used to estimate what the parameters and trust regions should be, effectively estimating the optimal Polyak step from the prior history. Detailed results are shown for eight structures using both the "good" and "bad" multisecant versions as well as the Anderson method and a hybrid approach, all with the same predictive method. Additional comparisons are made for 36 cases with a fixed algorithm greed. The predictive method works well independent of which method is used for the candidate step, and it is capable of adapting to different problem types particularly when coupled with the hybrid approach.

Perspectives from Highly Religious Families on Boundaries and Rules About Sex

We investigated the intersection of religion and boundaries placed around sex using qualitative data from 198 highly religious Muslim, Christian, and Jewish families. Coding performed by two researchers resulted in six core themes that provide insight into the connection between these two domains. Frequency counts of the core themes, participant quotes, and implications are presented-including the benefits of practitioners inquiring into how clients' faith affects sexual behavior and scripts, how fidelity and vows might serve a protective function for the relationships of highly religious couples, and how religion may empower women in terms of sexual boundary setting.

Does Flexoelectricity Drive Triboelectricity?

The triboelectric effect, charge transfer during sliding, is well established but the thermodynamic driver is not well understood. We hypothesize here that flexoelectric potential differences induced by inhomogeneous strains at nanoscale asperities drive tribocharge separation. Modeling single asperity elastic contacts suggests that nanoscale flexoelectric potential differences of ±1-10  V or larger arise during indentation and pull-off. This hypothesis agrees with several experimental observations, including bipolar charging during stick slip, inhomogeneous tribocharge patterns, charging between similar materials, and surface charge density measurements.

"The family that prays together . . .": Relational processes associated with regular family prayer

In the present article we explored how family prayer reportedly influenced family relationships. We conceptualized family prayer as a family ritual in religious families and used a qualitative methodology to interview a religiously, ethnically, and geographically diverse sample of 198 families (N = 476). Analysis of data revealed 7 related themes. Family prayer served important functions and influenced relationships in various ways including (a) as a time of family togetherness and interaction; (b) as a space for social support; and (c) as a means for intergenerational transmission of religion. Further, family prayer (d) involved issues and concerns of individuals and the family; (e) helped reduce relational tensions; (f) provided feelings of connectedness, unity, and bonding. Finally, (g) families struggled to pray together when there was disunity. Implications, applications, and future directions are addressed. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Sacred Practices and Family Processes in a Jewish Context: Shabbat as the Weekly Family Ritual Par Excellence

The present article provides a deep and more focused look at the utility, meaning, processes, and power involved in a specific, family-level, sacred practice or ritual from Judaism: Shabbat (Sabbath). Content analysis of in-depth interviews with 30 diverse, marriage-based Jewish families living in the United States (N = 77 individuals) yielded three emergent themes: (a) "Shabbat brings us closer together"; (b) How Shabbat brings the family together; and (c) The Power of Blessing the Children. These themes will be discussed respectively, along with related verbatim data from participants' in-depth qualitative interviews.

Direct Observation of "Pac-Man" Coarsening

We report direct observation of a "Pac-Man" like coarsening mechanism of a self-supporting thin film of nickel oxide. The ultrathin film has an intrinsic morphological instability due to surface stress leading to the development of local thicker regions at step edges. Density functional theory calculations and continuum modeling of the elastic instability support the model for the process.

Nanoparticle shape, thermodynamics and kinetics

Nanoparticles can be beautiful, as in stained glass windows, or they can be ugly as in wear and corrosion debris from implants. We estimate that there will be about 70,000 papers in 2015 with nanoparticles as a keyword, but only one in thirteen uses the nanoparticle shape as an additional keyword and research focus, and only one in two hundred has thermodynamics. Methods for synthesizing nanoparticles have exploded over the last decade, but our understanding of how and why they take their forms has not progressed as fast. This topical review attempts to take a critical snapshot of the current understanding, focusing more on methods to predict than a purely synthetic or descriptive approach. We look at models and themes which are largely independent of the exact synthetic method whether it is deposition, gas-phase condensation, solution based or hydrothermal synthesis. Elements are old dating back to the beginning of the 20th century-some of the pioneering models developed then are still relevant today. Others are newer, a merging of older concepts such as kinetic-Wulff constructions with methods to understand minimum energy shapes for particles with twins. Overall we find that while there are still many unknowns, the broad framework of understanding and predicting the structure of nanoparticles via diverse Wulff constructions, either thermodynamic, local minima or kinetic has been exceedingly successful. However, the field is still developing and there remain many unknowns and new avenues for research, a few of these being suggested towards the end of the review.

Looking for the Silver Lining: Benefit Finding after Hurricanes Katrina and Rita in Middle-Aged, Older, and Oldest-Old Adults

Looking for potentially positive outcomes is one way that people cope with stressful events. In two studies, we examined perceived "silver linings" after the 2005 Hurricanes Katrina and Rita among indirectly affected adults. In Study 1, middle-aged (ages 47-64 years), older (ages 65-89 years), and oldest-old (ages 90-95 years) adults in the Louisiana Healthy Aging Study (LHAS) responded to an open-ended question on perceived silver linings in a longitudinal assessment carried out during the immediate impact (1 to 4 months after landfall) and post-disaster recovery phase (6 to 14 months post-storm). Qualitative grounded theory methods were employed to analyze these narrative data. Team-based coding yielded three core themes: (1) learning experience and better preparedness for future disasters, (2) having improved cities (Baton Rouge and New Orleans), and (3) an increase in "Good Samaritan" acts such as strangers helping one another. Responses were similar across age groups, although older adults were the least likely to report positive outcomes. Study 2 was a conceptual replication using a different sample of adults (ages 31 to 82 years) tested at least five years after the storms. A learning experience and preparedness core theme replicated Study 1's findings while improved social cohesion amongst family and friends emerged as a new core theme in Study 2. These data indicate that identifying lessons learned and potentially positive outcomes are psychological reactions that may facilitate post-disaster coping and foster resilience for indirectly affected adults in the years after disaster.

Long-term psychological outcomes in older adults after disaster: relationships to religiosity and social support

OBJECTIVES

Natural disasters are associated with catastrophic losses. Disaster survivors return to devastated communities and rebuild homes or relocate permanently, although the long-term psychological consequences are not well understood. The authors examined predictors of psychological outcomes in 219 residents of disaster-affected communities in south Louisiana.

METHOD

Current coastal residents with severe property damage from the 2005 Hurricanes Katrina and Rita, and exposure to the 2010 British Petroleum Deepwater Horizon oil spill were compared and contrasted with former coastal residents and an indirectly affected control group. Participants completed measures of storm exposure and stressors, religiosity, perceived social support, and mental health.

RESULTS

Non-organizational religiosity was a significant predictor of post-traumatic stress disorder (PTSD) in bivariate and multivariate logistic regressions. Follow-up analyses revealed that more frequent participation in non-organizational religious behaviors was associated with a heightened risk of PTSD. Low income and being a coastal fisher were significant predictors of depression symptoms in bivariate and multivariate models. Perceived social support had a protective effect for all mental health outcomes, which also held for symptoms of depression and GAD in multivariate models.

CONCLUSION

People who experienced recent and severe trauma related to natural and technological disasters are at risk for adverse psychological outcomes in the years after these events. Individuals with low income, low social support, and high levels of non-organizational religiosity are also at greater risk. Implications of these data for current views on the post-disaster psychological reactions and the development of age-sensitive interventions to promote long-term recovery are discussed.

Transition from Order to Configurational Disorder for Surface Reconstructions on SrTiO_{3}(111)

There is growing interest in ternary oxide surfaces due to their role in areas ranging from substrates for low power electronics to heterogeneous catalysis. Descriptions of these surfaces to date focus on low-temperature explanations where enthalpy dominates, and less on the implications of configurational entropy at high temperatures. We report here the structure of three members of the n×n  (2≤n≤4) reconstructions of the strontium titanate (111) surface using a combination of transmission electron diffraction, density functional theory modeling, and scanning tunneling microscopy. The surfaces contain a mixture of the tetrahedral TiO_{4} units found on the (110) surface sitting on top of octahedral TiO_{5}[] (where [] is a vacant octahedral site), and TiO_{6} units in the second layer that are similar to those found on the (001) surface. We find clear evidence of a transition from the ordered enthalpy-dominated 3×3 and 4×4 structures to a configurational entropy-dominated 2×2 structure that is formed at higher temperatures. This changes many aspects of how oxide surfaces should be considered, with significant implications for oxide growth.

The effect of contact load on CoCrMo wear and the formation and retention of tribofilms

Tribochemical reactions in a protein lubricated metal-on-metal (MoM) sliding contact may play a significant role for its wear performance. Such reactions lead to the formation of a carbonaceous 'tribofilm', which can act as a protective layer against corrosion and wear. The purpose of this study was to determine the effect of contact load on wear and the formation and retention of tribofilms. Wear tests were performed in a custom-made ball-on-flat testing apparatus that incorporated an electrochemical cell. A ceramic ball was used to articulate against low-carbon wrought CoCrMo alloy pins in bovine serum. Using a range of contact loads at a single potentiostatic condition (close to free potential), weight loss and changes in surface properties were evaluated. We determined that wear was influenced by the loading condition. As expected, wear increased with load, but the association between applied load and measured weight loss was not linear. In the intermediate load region, in the range of 32-48 N (~58-80 MPa), there was more than an order of magnitude drop in the wear per unit load, and the wear versus load data suggested an inflexion point at 49 N. Regression analyses yielded a cubic model (R²=0.991; p=0.0002), where the cubic term, which represents the inflexion, was highly significant (p=0.0021). This model is supported by the observations that the minimum in the friction versus load curve is at 52 N and the highest relative increase in polarization resistance occurred at 49 N. Scanning electron microscopy and Raman spectroscopy indicated the absence of a tribofilm for the low and within the contact area of the high load cases. Synergistic interactions of wear and corrosion seem to play an important role.

Romanian Children’s Representations of Negative and Self-Conscious Emotions in a Narrative Story Stem Technique

This research uses children’s story-stem play narratives to investigate dimensions of negative emotional expression. Fifty-one Romanian children between 6 and 11-years old participated in the study. Children’s narratives were coded for three basic negative emotions and five self-conscious emotions. Parents completed a general questionnaire for demographic data and the amount of time they spent with their children. Differences were found for frequencies of negative emotional representations in relation to the specific story-stems in which they occurred. Girls were more likely than boys to enact in their narratives guilt feelings coupled with apology following some wrongdoing. Children who spent more time with parents enacted significantly less anger and fear. Simultaneous expressions of multiple negative emotions were observed in the narrative responses of these middle childhood-aged Romanian children. While findings should be viewed with caution, owing to the small and homogeneous sample, new directions for future research with this assessment method are indicated.

Perceptions of Longevity and Successful Aging in Very Old Adults

We examined perceptions of longevity and successful aging in young-old (60 to 74 years), old-old (75 to 89 years), and oldest-old (90 + years) adults drawn from the Louisiana Healthy Aging Study (LHAS). Participants' responses to three open-ended questions that assessed their attributions for longevity, what they look forward to, and advice for younger persons today were compared. Content analyses yielded three emergent themes: maintaining physical, mental, and relational well-being; living a healthy life; and living a faithful life. Implications of these findings for current views on successful aging and insights for promoting a long and healthy life are considered.

New insights into hard phases of CoCrMo metal-on-metal hip replacements

The microstructural and mechanical properties of the hard phases in CoCrMo prosthetic alloys in both cast and wrought conditions were examined using transmission electron microscopy and nanoindentation. Besides the known carbides of M(23)C(6)-type (M=Cr, Mo, Co) and M(6)C-type which are formed by either eutectic solidification or precipitation, a new mixed-phase hard constituent has been found in the cast alloys, which is composed of ∼100 nm fine grains. The nanosized grains were identified to be mostly of M(23)C(6) type using nano-beam precession electron diffraction, and the chemical composition varied from grain to grain being either Cr- or Co-rich. In contrast, the carbides within the wrought alloy having the same M(23)C(6) structure were homogeneous, which can be attributed to the repeated heating and deformation steps. Nanoindentation measurements showed that the hardness of the hard phase mixture in the cast specimen was ∼15.7 GPa, while the M(23)C(6) carbides in the wrought alloy were twice as hard (∼30.7 GPa). The origin of the nanostructured hard phase mixture was found to be related to slow cooling during casting. Mixed hard phases were produced at a cooling rate of 0.2 °C/s, whereas single phase carbides were formed at a cooling rate of 50 °C/s. This is consistent with sluggish kinetics and rationalizes different and partly conflicting microstructural results in the literature, and could be a source of variations in the performance of prosthetic devices in-vivo.

Graphitic tribological layers in metal-on-metal hip replacements

Arthritis is a leading cause of disability, and when nonoperative methods have failed, a prosthetic implant is a cost-effective and clinically successful treatment. Metal-on-metal replacements are an attractive implant technology, a lower-wear alternative to metal-on-polyethylene devices. Relatively little is known about how sliding occurs in these implants, except that proteins play a critical role and that there is a tribological layer on the metal surface. We report evidence for graphitic material in the tribological layer in metal-on-metal hip replacements retrieved from patients. As graphite is a solid lubricant, its presence helps to explain why these components exhibit low wear and suggests methods of improving their performance; simultaneously, this raises the issue of the physiological effects of graphitic wear debris.

Longitudinal Assessment of Cognitive and Psychosocial Functioning After Hurricanes Katrina and Rita: Exploring Disaster Impact on Middle-Aged, Older, and Oldest-Old Adults

The authors examined the effects of Hurricanes Katrina and Rita (HKR) on cognitive and psychosocial functioning in a lifespan sample of adults 6 to 14 months after the storms. Participants were recruited from the Louisiana Healthy Aging Study (LHAS). Most were assessed during the immediate impact period and retested for this study. Analyses of pre-and post-disaster cognitive data confirmed that storm-related decrements in working memory for middle-aged and older adults observed in the immediate impact period had returned to pre-hurricane levels in the post-disaster recovery period. Middle-aged adults reported more storm-related stressors and greater levels of stress than the two older groups at both waves of testing. These results are consistent with a burden perspective on post-disaster psychological reactions.

Wulff construction for alloy nanoparticles

The Wulff construction is an invaluable tool to understand and predict the shape of nanoparticles. We demonstrate here that this venerable model, which gives a size-independent thermodynamic shape, becomes size dependent in the nanoscale regime for an alloy and that the infinite reservoir approximation breaks down. The improvements in structure and energetic modeling have wide-ranging implications both in areas where energetics govern (e.g., nucleation and growth) and where the surface composition is important (e.g., heterogeneous catalysis).

Religion and Coping with Trauma: Qualitative Examples from Hurricanes Katrina and Rita

In this article, we consider the intersection of religious coping and the experience of Hurricanes Katrina and Rita in a lifespan sample of adults living in South Louisiana during the 2005 storms. Participants were young, middle-age, older, and oldest-old adults who were interviewed during the post-disaster recovery period. Qualitative analyses confirmed that three dimensions of religion were represented across participants' responses. These dimensions included: 1) faith community, in relation to the significant relief effort and involvement of area churches; 2) religious practices, in the sense of participants' behavioral responses to the storms, such as prayer; and c) spiritual beliefs, referring to faith as a mechanism underlying individual and family-level adjustment, acceptance and personal growth in the post-disaster period. Implications for future disaster preparedness are considered.

Vacant-site octahedral tilings on SrTiO(3) (001), the (sqrt[13]×sqrt[13])R33.7° surface, and related structures

The structure of the SrTiO(3) (001) (sqrt[13]×sqrt[13])R33.7° surface reconstruction has been determined using transmission electron diffraction combined with direct methods and density functional theory. It has a TiO(2)-rich surface with a 2D tiling of edge or corner-sharing TiO(5)□ octahedra. Additionally, different arrangements of these octahedral units at the surface, dictated by local bond-valence sums, form 2D networks that can account for many ordered surface reconstructions as well as disordered glasslike structures consistent with the multitude of structures observed experimentally, and potentially other materials and interfaces.

After Hurricanes Katrina and Rita: gender differences in health and religiosity in middle-aged and older adults

We examined health-related quality of life in adults in the Louisiana Health Aging Study (LHAS) after Hurricanes Katrina and Rita (HK/R) that made landfall on the U.S. Gulf Coast region in 2005. Analyses of pre- and post-disaster SF-36 scores yielded changes in physical function and bodily pain. Mental health scores were lower for women than men. Gender differences were observed in religious beliefs and religious coping, favoring women. Religious beliefs and religious coping were negatively correlated with physical function, implying that stronger reliance on religiosity as a coping mechanism may be more likely among those who are less physically capable.

Invocations and intoxication: does prayer decrease alcohol consumption?

Four methodologically diverse studies (N = 1,758) show that prayer frequency and alcohol consumption are negatively related. In Study 1 (n = 824), we used a cross-sectional design and found that higher prayer frequency was related to lower alcohol consumption and problematic drinking behavior. Study 2 (n = 702) used a longitudinal design and found that more frequent prayer at Time 1 predicted less alcohol consumption and problematic drinking behavior at Time 2, and this relationship held when controlling for baseline levels of drinking and prayer. In Study 3 (n = 117), we used an experimental design to test for a causal relationship between prayer frequency and alcohol consumption. Participants assigned to pray every day (either an undirected prayer or a prayer for a relationship partner) for 4 weeks drank about half as much alcohol at the conclusion of the study as control participants. Study 4 (n = 115) replicated the findings of Study 3, as prayer again reduced drinking by about half. These findings are discussed in terms of prayer as reducing drinking motives.

Structure and local-equilibrium thermodynamics of the c(2x2) reconstruction of rutile TiO2 (100)

We resolve the structure of a c(2x2) reconstruction of the rutile TiO2 (100) surface using a combination of transmission electron diffraction, direct methods analysis, and density functional theory. The surface structure contains an ordered array of subsurface oxygen vacancies and is in local thermodynamic equilibrium with bulk TiO2, but not the with oxygen gas-phase environment. The transition into a bulklike (1x1) reconstruction offers insights into the time-dependent local thermodynamics of TiO2 surface reconstruction under global nonequilibrium conditions.

A quantitative analysis of the cone-angle dependence in precession electron diffraction

Precession electron diffraction (PED) is a technique which is gaining increasing interest due to its ease of use and reduction of the dynamical scattering problem in electron diffraction. To further investigate the usefulness of this technique, we have performed a systematic study of the effect of precession angle on the mineral andalusite where the semiangle was varied from 6.5 to 32 mrad in five discrete steps. The purpose of this study was to determine the optimal conditions for the amelioration of kinematically forbidden reflections, and the measurement of valence charge density. We show that the intensities of kinematically forbidden reflections decay exponentially as the precession semiangle (varphi) is increased. We have also determined that charge density effects are best observed at moderately low angles (6.5-13 mrad) even though PED patterns become more kinematical in nature as the precession angle is increased further.

Surface Reconstruction with a Fractional Hole: (sqrt[5] x sqrt[5])R26.6 degrees LaAlO3 (001)

The structure of the (sqrt[5] x sqrt[5])R26.6 degrees reconstruction of LaAlO3 (001) has been determined using transmission electron diffraction combined with direct methods. It has a lanthanum oxide termination with one lanthanum vacancy per surface unit cell. Density functional calculations indicate that charge compensation occurs by a fractional number of highly delocalized holes, and that the surface contains no oxygen vacancies and the holes are not filled with hydrogen. The reconstruction can be understood in terms of expulsion of the more electropositive cation from the surface and increased covalency.

Precession electron diffraction 1: multislice simulation

Precession electron diffraction (PED) is a method that considerably reduces dynamical effects in electron diffraction data, potentially enabling more straightforward solution of structures using the transmission electron microscope. This study focuses upon the characterization of PED data in an effort to improve the understanding of how experimental parameters affect it in order to predict favorable conditions. A method for generating simulated PED data by the multislice method is presented and tested. Data simulated for a wide range of experimental parameters are analyzed and compared to experimental data for the (Ga,In)(2)SnO(4) (GITO) and ZSM-5 zeolite (MFI) systems. Intensity deviations between normalized simulated and kinematical data sets, which are bipolar for dynamical diffraction data, become unipolar for PED data. Three-dimensional difference plots between PED and kinematical data sets show that PED data are most kinematical for small thicknesses, and as thickness increases deviations are minimized by increasing the precession cone semi-angle phi. Lorentz geometry and multibeam dynamical effects explain why the largest deviations cluster about the transmitted beam, and one-dimensional diffraction is pointed out as a strong mechanism for deviation along systematic rows. R factors for the experimental data sets are calculated, demonstrating that PED data are less sensitive to thickness variation. This error metric was also used to determine the experimental specimen thickness. R(1) (unrefined) was found to be about 12 and 15% for GITO and MFI, respectively.

Theoretical structure factors for selected oxides and their effects in high-resolution electron-microscope (HREM) images

A reasonably detailed analysis of the effects of charge redistribution on both X-ray and electron structure factors as well as for high-resolution electron-microscope images are presented for a series of light-element oxides. The charge redistribution leads to differences of 2-3% for the X-ray structure factors and 5-7% for electron structure factors in the 0-0.5 A(-1) region. There are detectable changes in images of about 10% of the contrast, somewhat dependent upon the alignment of atom columns, specimen thickness and defocus. These studies suggest that charge redistribution may be detectable using a Cc-limited aberration-corrected microscope with a specimen thickness of about 50 A.

Religious beliefs, faith community involvement and depression: a study of rural, low-income mothers

The current study investigated the connection between religion and mental health of 131 rural, low-income mothers. Two dimensions of religion, beliefs and faith community involvement, were included and depression was assessed by the CES-D. The sample consisted of mothers who participated in Wave 2 of a multi-state research project. As hypothesized, both religious beliefs and faith community involvement were negatively related to depressive symptoms indicating that mothers with stronger religious beliefs and more involvement in religious activities may experience less depressive symptoms. The results of the current study confirm previous work and support a multifaceted view of religion.

Rapid structure determination of a metal oxide from pseudo-kinematical electron diffraction data

The electron precession diffraction technique is employed to provide quasi-kinematical data for determination of atom positions in the (Ga,In)2SnO5m-phase. Precession data are compared with conventional diffraction data captured under identical conditions and show a distinct superiority because they exhibit kinematical characteristics in the structure-defining reflections. Precessed data are not usable within a kinematical interpretation in all cases, and a simple basis is presented for omission of errant reflections to improve adherence to kinematical behavior. A second approach is demonstrated where intensities are used with direct methods instead of amplitudes, enhancing the contrast between strong and weak beams. The unrefined atom positions recovered a priori via direct methods are consistent between the two approaches and fall on average within 4 picometers of positions in the previously refined structure.

EDM 1.0: Electron direct methods

A computer program designed to provide a number of quantitative analysis tools for high-resolution imaging and electron diffraction data is described. The program includes basic image manipulation, both real space and reciprocal space image processing, Wiener-filtering, symmetry averaging, methods for quantification of electron diffraction patterns and two-dimensional direct methods. The program consists of a number of sub-programs written in a combination of C++, C and Fortran. It can be downloaded either as GNU source code or as binaries and has been compiled and verified on a wide range of platforms, both Unix based and PC's. Elements of the design philosophy as well as future possible extensions are described.

Direct observation of charge transfer at a MgO(111) surface

Transmission electron diffraction (TED) combined with direct methods have been used to study the sqrt[3]xsqrt[3]R30 degrees reconstruction on the polar (111) surface of MgO and refine the valence charge distribution. The surface is nonstoichiometric and is terminated by a single magnesium atom. A charge-compensating electron hole is localized in the next oxygen layer and there is a nominal charge transfer from the oxygen atoms to the top magnesium atom. The partial charges that we obtain for the surface atoms are in reasonable agreement with empirical bond-valence estimations.

Surface crystallography via electron microscopy

The study of atomic structure of surfaces is fundamental to the understanding of electronic, chemical and mechanical properties of surfaces and numerous techniques have been developed to this end. Transmission Electron Microscopy techniques, namely transmission electron imaging (TEM) and diffraction (TED), due to their ability to provide structural information at very high resolutions, have emerged as powerful tools for the study of surface structure. In this article we review the experimental method alongside the various post-processing routines that are necessary to extract vital structural information from experimental data.

Sufficient conditions for Direct Methods with swift electrons

We investigate cases where one can argue that sufficient conditions exist for Direct Methods to work with swift electrons. In addition to simple cases where kinematical scattering holds (e.g., surfaces in plan view), we identify three other configurations: (a) when 1s channeling holds and kinematical scattering is statistically correct; (b) when there is a mapping from kinematical to dynamical intensities that preserves the order of the intensities, for instance with powder or precession data, and (c) when the scattering is dominated by one type of atom. We also briefly discuss the possibility of using Direct Methods to restore the complex exit wave leaving a sample in the most general case.

Lensless imaging: a workshop on "new approaches to the phase problem for non-periodic objects."

Over the past two decades, theoretical tools and algorithms have been developed which, under not very restrictive conditions, allow the reconstruction of images from diffraction patterns of non-periodic objects. These methods promise lensless imaging for any radiation, free of aberrations, with wavelength-limited resolution. Recent experimental successes prompted an interdisciplinary international workshop on this topic at the Lawrence Berkeley National Laboratory, Berkeley, CA, USA, on May 17-19 2001, supported by the DOE, LBL and the Advanced Light Source. Our aim was to review the field, and to stimulate communication between the Signal Recovery, Coherent Optics, X-ray, Electron Microscopy and Applied Mathematics communities. The results are summarized in this paper and on the web. A second workshop is planned for 2003.

Statistical dynamical direct methods. II. The three-phase structure invariant

The triplet distribution used for kinematical diffraction is extended to the complex case appropriate for dynamical transmission electron diffraction. It is demonstrated that this gives good results if the distributions are handled statistically rather than relying upon single triplet relationships. As a consequence, conventional statistical direct methods will yield a reasonable approximation to the effective dynamical potential for thicknesses when kinematical theory is not appropriate. The recovered effective dynamical potential may be similar to the kinematical potential, but does not have to be and in general will not be.

Subsurface dimerization in III-V semiconductor (001) surfaces

We present the atomic structure of the c(8 x 2) reconstructions of InSb-, InAs-, and GaAs-(001) surfaces as determined by surface x-ray diffraction using direct methods. Contrary to common belief, group III dimers are not prominent on the surface, instead subsurface dimerization of group III atoms takes place in the second bilayer, accompanied by a major rearrangement of the surface atoms above the dimers to form linear arrays. By varying the occupancies of four surface sites the (001)-c(8 x 2) reconstructions of III-V semiconductors can be described in a unified model.

Single-walled BN nanostructures

We describe in situ synthesis and characterization of single-walled BN nanotubes terminated by fullerenelike structures using electron-cyclotron resonance nitrogen and electron beam boron sources onto polycrystalline tungsten substrates. Detailed comparisons of experimental high-resolution electron microscopy images and simulations based upon molecular models show a dominance of kinks and bends involving fourfold and eightfold ring structures as against fivefold or sevenfold which have been found with carbon. Analysis of the structures as a function of film thickness indicates that they are growing by addition of atoms to the exposed ends of single sheets, not at the substrate-nanostructure interface.

Electron crystallography in surface structure analysis

Surface structure analysis is an important area of research, and in recent years notable advances have been made in this field, both in improved techniques for studying surfaces and in methods of analyzing them. This review aims to summarize the techniques available, particularly those relating to electron microscopy, and also to outline one of the newest areas of development, the application of direct methods to surface structure analysis.