Energy conditions in general relativity and quantum field theory

This review summarizes the current status of the energy conditions in general relativity and quantum field theory. We provide a historical review and a summary of technical results and applications, complemented with a few new derivations and discussions. We pay special attention to the role of the equations of motion and to the relation between classical and quantum theories. Pointwise energy conditions were first introduced as physically reasonable restrictions on matter in the context of general relativity. They aim to express e.g. the positivity of mass or the attractiveness of gravity. Perhaps more importantly, they have been used as assumptions in mathematical relativity to prove singularity theorems and the non-existence of wormholes and similar exotic phenomena. However, the delicate balance between conceptual simplicity, general validity and strong results has faced serious challenges, because all pointwise energy conditions are systematically violated by quantum fields and also by some rather simple classical fields. In response to these challenges, weaker statements were introduced, such as quantum energy inequalities and averaged energy conditions. These have a larger range of validity and may still suffice to prove at least some of the earlier results. One of these conditions, the achronal averaged null energy condition, has recently received increased attention. It is expected to be a universal property of the dynamics of all gravitating physical matter, even in the context of semiclassical or quantum gravity.Comment: 61 pages, 6 figures, Topical review accepted by Classical and Quantum Gravit

The Power Control Rack: A Modular Solution for Building Power Systems

LDRD proposal presentation to ETA ALD at LBNL. Proposing use of SST to create a modular efficient single point of common coupling for buildings

2009 Alaska Health Workforce Vacancy Study

Alaska continues to experience health professional shortages. The state has long had a deficient “supply side” characterized by insufficient numbers of key health workers whose recruitment, retention, and training have been impeded by Alaska’s remoteness, harsh climate, rural isolation, low population density, and scarce training resources. Alaska is the only state without a pharmacy school and lacks its own dental and physical therapy schools as well. Health professional shortages can be decreased through the start of new training programs, the expansion of existing programs, and the improvement of the effectiveness of recruitment and retention efforts. However, strategic planning and the execution of such programs require valid and accurate data. To this end, stakeholders such as the Alaska Mental Health Trust Authority (AMHTA) and Alaskan's For Access to Health Care (ACCESS), along with schools and departments within the University of Alaska Anchorage (UAA), funded the Alaska Center for Rural Health-Alaska’s AHEC (ACRH) and the Institute of Social and Economic Research (ISER) to conduct a comprehensive health workforce study during winter and spring of 2009. This report highlights employers’ needs for employees to fill budgeted positions. This is different from a needs assessment that would take into account population demographics and disease incidence and prevalence. This health workforce study is an assessment of health manpower shortage based on budgeted staff positions and their vacancies in organizations throughout the state. Respondents included part-time positions, which resulted in our counting full-time equivalent (FTE) rather than individuals (“bodies”). In situations where a position was divided among more than one occupation (e.g., Dental Assistant and Billing Clerk), we asked the respondent to count the position under which they considered the position’s “primary occupation.” This was a point-in-time cross-sectional study. Recently filled vacancies or imminent vacancies were not counted. Positions filled by relief/temporary/locum/contract health workers were counted as vacancies only if these workers were temporarily filling a currently vacant, budgeted position. Due to budget and time constraints, we were not able to conduct a trend analysis that is a comparison of this study’s findings and the prior 2007 study. The key questions this study sought to answer were (1) How many budgeted positions, either full- or part-time, existed in organizations providing health services in Alaska? (2) How many of these budgeted positions were currently vacant? (3) What was the vacancy rate? (4) How many of the organizations that employ these occupations hired new graduates of training programs? (5) How many of the currently vacant budgeted positions (#2) could be filled by new graduates of training programs? (6) What were the mean and maximum length of time, expressed in months, that the vacancies have existed? (7) What were the principal, underlying causes of vacancies? The study was designed in consultation with an advisory group that included AMHTA, ACCESS, and UAA. The study targeted 93 health occupations. The unit of analysis was the employment site by organization type, which allowed for the allocation of positions and vacancies by geographic region. For each employer, we identified the staff person most knowledgeable about hiring and vacancies. In large organizations this meant that one employer might provide information about multiple sites and organization types; smaller employers were responsible for only a single site.Alaska Mental Health Trust Authority. Alaskan's for Access to Health Care. University of Alaska Fairbanks, Tanana Valley campus Telemedicine program. University of Alaska Anchorage, Community and Technical College. University of Alaska Anchorage, School of Nursing.Acknowledgements / Executive Summary / Table of Contents / Problem and Rationale / Methodology / Limitations of Study / Findings / Appendix A. List of Health Occupations / Appendix B. Health Workforce Surveys / Appendix C. Cover Letter Accompanying Survey Forms / Appendix D. Confidence Intervals for Positions, Vacancies, Number of Vacancies Filled with New Graduates, and Length of Longest Vacancy in Months / Appendix E. Tables of Samples and Estimates of Positions, Vacancies, Vacancy Rates, Number of Vacancies Filled with New Graduates, Mean and Maximum Length of Longest Vacancy in Months / Appendix F. Tables of Occupations Sorted By Estimates of Positions, Vacancies, Vacancy Rates, Number of Vacancies Filled with New Graduates, Mean and Maximum Length of Longest Vacancy in Month

Parental perceptions of technology and technology-focused parenting: Associations with youth screen time

In the present study we propose a model linking parental perceptions of technology to technology-related parenting strategies to youth screen time, and, finally, to internalizing and externalizing problem behaviors. Participants were 615 parents drawn from three community samples of families with children across three developmental stages: young childhood, middle childhood, and adolescence. The model was tested at each stage with the strongest support emerging in the young childhood sample. One component of parental perceptions of technology, perceived efficacy, was related to technology-related parenting strategies across developmental stages. However, the association of these strategies to child screen time and, in turn, problem behaviors, diminished as children increased in age. Implications for intervention are considered

Substrate Release Mechanisms for Gas Metal Arc 3-D Aluminum Metal Printing. 3D Printing &Additive Manufacturing

International audienceLimited material options, prohibitively expensive equipment, and high production costs currently limit the ability of small and medium enterprises to use 3-D printing to prototype and manufacture metallic goods. A low-cost open-source 3-D metal printer that utilizes gas metal arc welding technology has been developed that could make metal printing accessible to the average consumer. Unfortunately, this technology would demand access to expensive cutting tools for part removal from the substrate. This paper investigates several substrate treatments to provide a low-cost method to easily remove 3-D printed 1100 aluminum parts from a reusable substrate. Coatings of aluminum oxide and boron nitride on 1100 aluminum and A36 low carbon steel substrates were tested. Lap shear tests were performed to assess the interlayer adhesion between the printed metal part and the print substrate. No warping of the substrate was observed during printing. It was determined that boron nitride coated low carbon steel provided the lowest adhesion strength. Printing aluminum on uncoated low carbon steel also allowed easy removal of the aluminum part with the benefit of no additional coating steps or costs

Predicting running away in girls who are victims of commercial sexual exploitation

Youth that are victims of commercial sexual exploitation of children (CSEC) have a host of clinical problems and often run away from home, residential care, and treatment, which complicates and limits treatment effectiveness. No research to date has attempted to predict running away in CSEC victims. The present study aimed to 1) characterize a clinically referred sample of girls who were victims of CSEC and compare them to other high-risk girls (i.e., girls who also have a history of trauma and running away, but deny CSEC); and 2) examine the utility of using the Youth Level of Service/Case Management Inventory (YLS/CMI) to predict future running away. Data were collected from de-identified charts of 80 girls (mean age = 15.38, SD = 1.3, 37.9% White, 52.5% CSEC victims) who were referred for psychological assessment by the Department of Child Services. Girls in the CSEC group were more likely to have experienced sexual abuse (χ2 = 6.85, p = .009), an STI (χ2 = 6.45, p = .01), a post-traumatic stress disorder diagnosis (χ2 = 11.84, p = .001), and a substance use disorder diagnosis (χ2 = 11.32, p = .001) than high-risk girls. Moderated regression results indicated that YLS/CMI scores significantly predicted future running away among the CSEC group (β = 0.23, SE = .06, p = .02), but not the high-risk group (β = -.008, SE = .11, p =.90). The YLS/CMI shows initial promise for predicting future running away in girls who are CSEC victims. Predicting running away can help identify those at risk for and prevent running away and improve treatment outcomes. We hope current findings stimulate future work in this area

Conduct disorder symptoms and illicit drug use in juvenile justice involved youth: The reciprocal relationship between positive illicit drug use attitudes and illicit drug use

Conduct disorder (CD) symptoms cooccur at high rates with illicit drug use in juvenile justice involved youth, which results in poorer outcomes; however, research has not identified where best to intervene in this relationship, limiting the identification of modifiable risk factors to reduce negative effects of CD symptoms. Two mediation models were examined to investigate the potential for CD symptoms to influence a reciprocal relationship between illicit drug use and positive drug attitudes, controlling for age, gender, and race. Data were examined for 245 juvenile justice involved youth (mean age = 15.46, SD = 1.30, range 12-18, 64.9% Black, 80.4% male) who completed court-ordered psychological assessments. Findings indicate: (1) Positive attitudes toward illicit drug use significantly mediated the relationship between CD symptoms and illicit drug use (β = 0.16, CI 0.09-0.27; test for indirect effect z = 4.17, p < .001) and (2) illicit drug use significantly mediated the relationship between CD symptoms and positive attitudes toward illicit drug use (β = 0.20, CI 0.12-0.32; test for indirect effect z = 4.87, p < .001). Overall, the present study suggests that CD symptoms impart risk for illicit drug use both indirectly, through more positive attitudes toward illicit drug use, and directly, which further strengthens positive attitudes toward illicit drug use

PTSD Symptoms Mediate the Relationship Between Sexual Abuse and Substance Use Risk in Juvenile Justice-Involved Youth

Juvenile justice-involved youth face disproportionate rates of sexual abuse, which increases the risk of post-traumatic stress disorder (PTSD) and substance use disorders (SUDs), both of which are associated with poor long-term outcomes. The present study tested two mediation and moderation models, controlling for age, race, and history of physical abuse, with gender as a moderator, to determine whether PTSD symptoms serve as a risk factor and/or mechanism in the relationship between sexual abuse and substance use. Data were examined for 197 juvenile justice-involved youth (mean age = 15.45, 68.9% non-White, 78.4% male) that completed court-ordered psychological assessments. Results indicated that PTSD symptoms significantly mediated the relationship between sexual abuse and drug (β = 3.44, confidence interval [CI] [0.26, 7.41]; test for indirect effect z = 2.41, p = .02) and alcohol use (β = 1.42, CI [0.20, 3.46]; test for indirect effect z = 2.23, p = .03). PTSD symptoms and gender were not significant moderators. Overall, PTSD symptoms mediate the relationship between sexual abuse and SUDs in juvenile justice-involved youth, which suggests viability of targeting PTSD symptoms as a modifiable risk factor to reduce the effects of sexual abuse on substance use in this high-risk population

A controlled study of cold dust content in galaxies from z=0−2z=0-2

At $z=1-3$, the formation of new stars is dominated by dusty galaxies whose far-IR emission indicates they contain colder dust than local galaxies of a similar luminosity. We explore the reasons for the evolving IR emission of similar galaxies over cosmic time using: 1) Local galaxies from GOALS $(L_{\rm IR}=10^{11}-10^{12}\,L_\odot)$; 2) Galaxies at $z\sim0.1-0.5$ from the 5MUSES ($L_{\rm IR}=10^{10}-10^{12}\,L_\odot$); 3) IR luminous galaxies spanning $z=0.5-3$ from GOODS and Spitzer xFLS ($L_{\rm IR}>10^{11}\,L_\odot$). All samples have Spitzer mid-IR spectra, and Herschel and ground-based submillimeter imaging covering the full IR spectral energy distribution, allowing us to robustly measure $L_{\rm IR}^{\rm\scriptscriptstyle SF}$, $T_{\rm dust}$, and $M_{\rm dust}$ for every galaxy. Despite similar infrared luminosities, $z>0.5$ dusty star forming galaxies have a factor of 5 higher dust masses and 5K colder temperatures. The increase in dust mass is linked with an increase in the gas fractions with redshift, and we do not observe a similar increase in stellar mass or star formation efficiency. $L_{160}^{\rm\scriptscriptstyle SF}/L_{70}^{\rm\scriptscriptstyle SF}$, a proxy for $T_{\rm dust}$, is strongly correlated with $L_{\rm IR}^{\rm\scriptscriptstyle SF}/M_{\rm dust}$ independently of redshift. We measure merger classification and galaxy size for a subsample, and there is no obvious correlation between these parameters and $L_{\rm IR}^{\rm \scriptscriptstyle SF}/M_{\rm dust}$ or $L_{160}^{\rm\scriptscriptstyle SF}/L_{70}^{\rm\scriptscriptstyle SF}$. In dusty star forming galaxies, the change in $L_{\rm IR}^{\rm\scriptscriptstyle SF}/M_{\rm dust}$ can fully account for the observed colder dust temperatures, suggesting that any change in the spatial extent of the interstellar medium is a second order effect.Comment: Accepted for publication in ApJ. 21 pages, 11 figure

The evolution of submillimetre galaxies: two populations and a redshift cut-off

We explore the epoch dependence of number density and star-formation rate for submillimetre galaxies (SMGs) found at 850 um. The study uses a sample of 38 SMG in the GOODS-N field, for which cross-waveband identifications have been obtained for 35/38 members together with redshift measurements or estimates. A maximum-likelihood analysis is employed, along with the `single-source-survey' technique. We find a diminution in both space density and star formation rate at z > 3, closely mimicking the redshift cut-offs found for QSOs selected in different wavebands. The diminution in redshift is particularly marked, at a significance level too small to measure. The data further suggest, at a significance level of about 0.001, that two separately-evolving populations may be present, with distinct luminosity functions. These results parallel the different evolutionary behaviours of LIRGs and ULIRGs, and represent another manifestation of `cosmic down-sizing', suggesting that differential evolution extends to the most extreme star-forming galaxies.Comment: 12 pages, 11 figures, MNRAS accepted. The new version, as accepted for MNRAS, is substantially revised, with more detail on sample selection as well as extended significance tests of the result