Eigenvector continuation with subspace learning

A common challenge faced in quantum physics is finding the extremal eigenvalues and eigenvectors of a Hamiltonian matrix in a vector space so large that linear algebra operations on general vectors are not possible. There are numerous efficient methods developed for this task, but they generally fail when some control parameter in the Hamiltonian matrix exceeds some threshold value. In this work we present a new technique called eigenvector continuation that can extend the reach of these methods. The key insight is that while an eigenvector resides in a linear space with enormous dimensions, the eigenvector trajectory generated by smooth changes of the Hamiltonian matrix is well approximated by a very low-dimensional manifold. We prove this statement using analytic function theory and propose an algorithm to solve for the extremal eigenvectors. We benchmark the method using several examples from quantum many-body theory.Comment: Version to appear in Physical Review Letters, 4 + 6 pages (main + supplemental materials), 1 + 6 figures (main + supplemental materials

Time fractals and discrete scale invariance with trapped ions

We show that a one-dimensional chain of trapped ions can be engineered to produce a quantum mechanical system with discrete scale invariance and fractal-like time dependence. By discrete scale invariance we mean a system that replicates itself under a rescaling of distance for some scale factor, and a time fractal is a signal that is invariant under the rescaling of time. These features are reminiscent of the Efimov effect, which has been predicted and observed in bound states of three-body systems. We demonstrate that discrete scale invariance in the trapped ion system can be controlled with two independently tunable parameters. We also discuss the extension to n-body states where the discrete scaling symmetry has an exotic heterogeneous structure. The results we present can be realized using currently available technologies developed for trapped ion quantum systems.Comment: 4 + 5 pages (main + supplemental materials), 2 + 3 figures (main + supplemental materials), version to appear in Physical Review A Rapid Communication

Learning To Rank Diversely At Airbnb

Airbnb is a two-sided marketplace, bringing together hosts who own listings for rent, with prospective guests from around the globe. Applying neural network-based learning to rank techniques has led to significant improvements in matching guests with hosts. These improvements in ranking were driven by a core strategy: order the listings by their estimated booking probabilities, then iterate on techniques to make these booking probability estimates more and more accurate. Embedded implicitly in this strategy was an assumption that the booking probability of a listing could be determined independently of other listings in search results. In this paper we discuss how this assumption, pervasive throughout the commonly-used learning to rank frameworks, is false. We provide a theoretical foundation correcting this assumption, followed by efficient neural network architectures based on the theory. Explicitly accounting for possible similarities between listings, and reducing them to diversify the search results generated strong positive impact. We discuss these metric wins as part of the online A/B tests of the theory. Our method provides a practical way to diversify search results for large-scale production ranking systems.Comment: Search ranking, Diversity, e-commerc

Lessons Learned from Juntos Y Saludables Peer-Led Parent Education

Purpose: The objective of this study was to assess the quality of training received by peer educators in the Juntos y Saludables (Get Healthy Together) program. Juntos y Saludables is a multi-component childhood obesity prevention program for Head Start. Method: This study applied the peer led education approach to provide parents with education regarding healthy growth among their children. Seven parents were recruited through teachers, other parents, and the Parent Leadership Institute at a local Head Start center. Faculty and graduate assistants from local universities provided training to the parent educators in both English and Spanish. Training sessions were conducted the week of each new parent education session, with one booster training after spring break (7 training sessions in total). The parent educators were trained to: (1) encourage the Head Start parents to participate in the sessions, (2) explain the health messages, and (3) answer any questions the parents had. A focus group was conducted at the end of the program, with all seven parent educators, to assess their feedback about the training they received. Results: The peer parent educators reported that they became educators to improve children’s health. They were satisfied with the training methods and felt that they learned a lot of information regarding nutrition and physical activity recommendations for their children. They also reported feeling comfortable delivering health information to other parents. Parent educators appreciated that they could work together (e.g., in bilingual pairs) to provide the health education to parents in both English and Spanish. The peer parent education training session attendance was high-71% and greater. Conclusions: Most peer parent educators felt comfortable and confident delivering the material as the program progressed. Earlier training might assist the parent educators to have greater familiarity with content prior to the first session. Educators also created strategies to deal with situations that arose during the sessions (e.g. crowd control, parents requesting extra bags). Future training can include suggested strategies to handle similar situations

Towards spin-polarized two-dimensional electron gas at a surface of an antiferromagnetic insulating oxide

The surfaces of transition-metal oxides with the perovskite structure are fertile grounds for the discovery of novel electronic and magnetic phenomena. In this article, we combine scanning transmission electron microscopy (STEM) with density functional theory (DFT) calculations to obtain the electronic and magnetic properties of the (001) surface of a ( LaFe O 3 ) 8 / ( SrFe O 3 ) 1 superlattice film capped with four layers of LaFe O 3 . Simultaneously acquired STEM images and electron-energy-loss spectra reveal the surface structure and a reduction in the oxidation state of iron from F e 3 + in the bulk to F e 2 + at the surface, extending over several atomic layers, which signals the presence of oxygen vacancies. The DFT calculations confirm the reduction in terms of oxygen vacancies and further demonstrate the stabilization of an exotic phase in which the surface layer is half metallic and ferromagnetic, while the bulk remains antiferromagnetic and insulating. Based on the calculations, we predict that the surface magnetism and conductivity can be controlled by tuning the partial pressure of oxygen

Towards spin-polarized two-dimensional electron gas at a surface of an antiferromagnetic insulating oxide

The surfaces of transition-metal oxides with the perovskite structure are fertile grounds for the discovery of novel electronic and magnetic phenomena. In this article, we combine scanning transmission electron microscopy (STEM) with density functional theory (DFT) calculations to obtain the electronic and magnetic properties of the (001) surface of a ( LaFe O 3 ) 8 / ( SrFe O 3 ) 1 superlattice film capped with four layers of LaFe O 3 . Simultaneously acquired STEM images and electron-energy-loss spectra reveal the surface structure and a reduction in the oxidation state of iron from F e 3 + in the bulk to F e 2 + at the surface, extending over several atomic layers, which signals the presence of oxygen vacancies. The DFT calculations confirm the reduction in terms of oxygen vacancies and further demonstrate the stabilization of an exotic phase in which the surface layer is half metallic and ferromagnetic, while the bulk remains antiferromagnetic and insulating. Based on the calculations, we predict that the surface magnetism and conductivity can be controlled by tuning the partial pressure of oxygen

Acupuncture for cancer pain in adults.

BACKGROUND: Forty percent of individuals with early or intermediate stage cancer and 90% with advanced cancer have moderate to severe pain and up to 70% of patients with cancer pain do not receive adequate pain relief. It has been claimed that acupuncture has a role in management of cancer pain and guidelines exist for treatment of cancer pain with acupuncture. OBJECTIVES: To evaluate efficacy of acupuncture for relief of cancer-related pain in adults. SEARCH STRATEGY: CENTRAL, MEDLINE, EMBASE, PsycINFO, AMED, and SPORTDiscus were searched up to November 2010 including non-English language papers. SELECTION CRITERIA: Randomised controlled trials (RCTs) evaluating any type of invasive acupuncture for pain directly related to cancer in adults of 18 years or over. DATA COLLECTION AND ANALYSIS: It was planned to pool data to provide an overall measure of effect and to calculate the number needed to treat to benefit, but this was not possible due to heterogeneity. Two review authors (CP, OT) independently extracted data adding it to data extraction sheets. Quality scores were given to studies. Data sheets were compared and discussed with a third review author (MJ) who acted as arbiter. Data analysis was conducted by CP, OT and MJ. MAIN RESULTS: Three RCTs (204 participants) were included. One high quality study investigated the effect of auricular acupuncture compared with auricular acupuncture at 'placebo' points and with non-invasive vaccaria ear seeds attached at 'placebo' points. Participants in two acupuncture groups were blinded but blinding wasn't possible in the ear seeds group because seeds were attached using tape. This may have biased results in favour of acupuncture groups. Participants in the real acupuncture group had lower pain scores at two month follow-up than either the placebo or ear seeds group.There was high risk of bias in two studies because of low methodological quality. One study comparing acupuncture with medication concluded that both methods were effective in controlling pain, although acupuncture was the most effective. The second study compared acupuncture, point-injection and medication in participants with stomach cancer. Long-term pain relief was reported for both acupuncture and point-injection compared with medication during the last 10 days of treatment. Although both studies have positive results in favour of acupuncture they should be viewed with caution due to methodological limitations, small sample sizes, poor reporting and inadequate analysis. AUTHORS' CONCLUSIONS: There is insufficient evidence to judge whether acupuncture is effective in treating cancer pain in adults

College Students’ Percieved Barriers and Failitators to Maintaining a Healthy Bodyweight

PURPOSE: It has been evident that on average college students experienced excess weight gain as they transited from high school. The objectives of this study were to qualitatively explore college students’ perceived barriers and facilitators to maintaining a healthy bodyweight and identify the key modifiable factors underlying unhealthy behaviors. METHOD: The study employed photovoice (PV), a qualitative research method, in undergraduate students in South Texas. Participants took pictures and wrote descriptions of three perceived barriers and three facilitators to maintaining a healthy body weight; they were then asked to choose one of each for discussion. Eight focus groups were conducted with 96 participants and were audio-taped and transcribed verbatim. Qualitative analysis was sequential, utilizing a combination of editing and immersion crystallization. RESULTS: We were able to identify an array of common perceived facilitators and barriers to maintaining a healthy body weight among college students. Common barriers included time constraints, peer influences, unhealthy vending machine options, high cost of and limited access to healthy foods, obesogenic campus infrastructure, cultural environment, and social norms. Common facilitators included social support, access to a campus recreation center, having a variety of physical activity options available, health education classes, acting as a role model for their children, health benefits through work, sidewalks and staircases around campus, and the ability to pack healthier foods from home to take to campus. CONCLUSION: This study highlights the need for policy and environmental changes on college campuses such as: more affordable and accessible variety of healthier food options; meal heating and refrigeration facilities; bans on unhealthy vending content; and mandatory physical and health education. Social marketing campaigns and support groups would facilitate a shift of cultural and social norms toward a health promoting attitude

Triad3a induces the degradation of early necrosome to limit RipK1-dependent cytokine production and necroptosis.

Understanding the molecular signaling in programmed cell death is vital to a practical understanding of inflammation and immune cell function. Here we identify a previously unrecognized mechanism that functions to downregulate the necrosome, a central signaling complex involved in inflammation and necroptosis. We show that RipK1 associates with RipK3 in an early necrosome, independent of RipK3 phosphorylation and MLKL-induced necroptotic death. We find that formation of the early necrosome activates K48-ubiquitin-dependent proteasomal degradation of RipK1, Caspase-8, and other necrosomal proteins. Our results reveal that the E3-ubiquitin ligase Triad3a promotes this negative feedback loop independently of typical RipK1 ubiquitin editing enzymes, cIAPs, A20, or CYLD. Finally, we show that Triad3a-dependent necrosomal degradation limits necroptosis and production of inflammatory cytokines. These results reveal a new mechanism of shutting off necrosome signaling and may pave the way to new strategies for therapeutic manipulation of inflammatory responses