Effective String Theory Simplified

In this set of notes we simplify the formulation of the Poincare'-invariant effective string theory in D dimensions by adding an intrinsic metric and embedding its dynamics into the Polyakov formalism. We use this formalism to construct operators order by order in the inverse physical length of the string, in a fully gauge-invariant framework. We use this construction to discuss universality and nonuniversality of observables up to and including next-to-next-to-leading order in the long string expansion.Comment: v. 3, minor change

Identifying the Effects of Monetary Policy Shocks on Exchange Rates Using High Frequency Data

This paper proposes a new approach to identifying the effects of monetary policy shocks in an international vector autoregression. Using high-frequency data on the prices of Fed Funds futures contracts, we measure the impact of the surprise component of the FOMC-day Federal Reserve policy decision on financial variables, such as the exchange rate and the foreign interest rate. We show how this information can be used to achieve identification without having to make the usual strong assumption of a recursive ordering.

Identifying the effects of monetary policy shocks on exchange rates using high frequency data

This paper proposes a new approach to identifying the effects of monetary policy shocks in an international vector autoregression. Using high-frequency data on the prices of eurodollar contracts, we measure the impact of the surprise component of the FOMC-day Federal Reserve policy decision on financial variables, such as the exchange rate and the foreign interest rate. We show how this information can be used to achieve identification without having to make the usual strong assumption of a recursive ordering. JEL Classification: C32, E52, F30Exchange Rates, High Frequency Data, Identification, monetary policy, Vector autoregression

Prescription Drug Use under Medicare Part D: A Linear Model of Nonlinear Budget Sets

Medicare Part D enrollees face a complicated decision problem: they must dynamically choose prescription drug consumption in each period given difficult- to-find prices and a non-linear budget set. We use Medicare Part D claims data from 2006-2009 to estimate a flexible model of consumption that accounts for non-linear budget sets, dynamic incentives due to myopia and uncertainty, and price salience. By using variation away from kink points, we are able to estimate structural models with a linear regression of consumption on coverage range prices. We then compare performance under several candidate models of expectations and coverage phase weighting. The estimates suggest small marginal price elasticities and substantial myopia; we also find evidence that salient plan characteristics impact consumption beyond their effect on out-of-pocket prices. A hyperbolic discounting model which allows for salient plan characteristics fits the data well, and outperforms both rational models and alternative behavioral models

Functional Evolution of PLP-dependent Enzymes based on Active-Site Structural Similarities

Families of distantly related proteins typically have very low sequence identity, which hinders evolutionary analysis and functional annotation. Slowly evolving features of proteins, such as an active site, are therefore valuable for annotating putative and distantly related proteins. To date, a complete evolutionary analysis of the functional relationship of an entire enzyme family based on active-site structural similarities has not yet been undertaken. Pyridoxal-5’-phosphate (PLP) dependent enzymes are primordial enzymes that diversified in the last universal ancestor. Using the Comparison of Protein Active Site Structures (CPASS) software and database, we show that the active site structures of PLP-dependent enzymes can be used to infer evolutionary relationships based on functional similarity. The enzymes successfully clustered together based on substrate specificity, function, and three-dimensional fold. This study demonstrates the value of using active site structures for functional evolutionary analysis and the effectiveness of CPASS

Lattice Super Yang-Mills: A Virial Approach to Operator Dimensions

The task of calculating operator dimensions in the planar limit of N=4 super Yang-Mills theory can be vastly simplified by mapping the dilatation generator to the Hamiltonian of an integrable spin chain. The Bethe ansatz has been used in this context to compute the spectra of spin chains associated with various sectors of the theory which are known to decouple in the planar (large-N_c) limit. These techniques are powerful at leading order in perturbation theory but become increasingly complicated beyond one loop in the 't Hooft parameter lambda=g_YM^2 N_c, where spin chains typically acquire long-range (non-nearest-neighbor) interactions. In certain sectors of the theory, moreover, higher-loop Bethe ansaetze do not even exist. We develop a virial expansion of the spin chain Hamiltonian as an alternative to the Bethe ansatz methodology, a method which simplifies the computation of dimensions of multi-impurity operators at higher loops in lambda. We use these methods to extract previously reported numerical gauge theory predictions near the BMN limit for comparison with corresponding results on the string theory side of the AdS/CFT correspondence. For completeness, we compare our virial results with predictions that can be derived from current Bethe ansatz technology.Comment: LaTeX, 1 figure, 28 pages; v2: typo correcte

An Evaluation of the Educational Impact of College Campus Visits:A Randomized Experiment

We hypothesize that a lack of experience with college poses a non-trivial barrier to college access for historically underrepresented students. We study whether visits to a college campus during the eighth grade can reduce these psychological barriers to college access. Using an experimental design, we study whether college visits affect students’ knowledge about college, postsecondary intentions, college-going behaviors, academic engagement, and ninth grade course enrollment decisions. We recruited 885 students across 15 schools who participated in our project during the academic year 2017-2018. We randomized students within schools to either a treatment or control condition. Students in the control condition receive an information packet about college. Students in the treatment condition receive the same information and visit a flagship university three times during their 8th-grade academic year. Students assigned to participate in these campus visits demonstrate higher levels of knowledge about college, higher levels of effort while completing the survey, a higher likelihood of having conversations with school personnel about college, and a decreased desire to attend technical school. Additionally, treated students are more likely to enroll in advanced math and science/social science courses in 9th grade

Providing and Receiving Feedback: It Takes Two to Tango!

Effective feedback is essential for maximizing learning, improving teacher effectiveness, and ensuring optimal team performance. Despite how critical feedback is to patient care, many educators find it difficult to provide feedback, and learners sometimes feel uncomfortable receiving feedback

Including ultrasound scans in antenatal care in low-resource settings: Considering the complementarity of obstetric ultrasound screening and maternity waiting homes in strengthening referral systems in low-resource, rural settings

Recent World Health Organization (WHO) antenatal care recommendations include an ultrasound scan as a part of routine antenatal care. The First Look Study, referenced in the WHO recommendation, subsequently shows that the routine use of ultrasound during antenatal care in rural, low-income settings did not improve maternal, fetal or neonatal mortality, nor did it increase women\u27s use of antenatal care or the rate of hospital births. This article reviews the First Look Study, reconsidering the assumptions upon which it was built in light of these results, a supplemental descriptive study of interviews with patients and sonographers that participated in the First Look study intervention, and a review of the literature. Two themes surface from this review. The first is that focused emphasis on building the pregnancy risk screening skills of rural primary health care personnel may not lead to adaptations in referral hospital processes that could benefit the patient accordingly. The second is that agency to improve the quality of patient reception at referral hospitals may need to be manufactured for obstetric ultrasound screening, or remote pregnancy risk screening more generally, to have the desired impact. Stemming from the literature, this article goes on to examine the potential for complementarity between obstetric ultrasound screening and another approach encouraged by the WHO, the maternity waiting home. Each approach may address existing shortcomings in how the other is currently understood. This paper concludes by proposing a path toward developing and testing such a hybrid approach

Factors influencing referrals for ultrasound-diagnosed complications during prenatal care in five low and middle income countries

BACKGROUND: Ultrasound during antenatal care (ANC) is proposed as a strategy for increasing hospital deliveries for complicated pregnancies and improving maternal, fetal, and neonatal outcomes. The First Look study was a cluster-randomized trial conducted in the Democratic Republic of Congo, Guatemala, Kenya, Pakistan and Zambia to evaluate the impact of ANC-ultrasound on these outcomes. An additional survey was conducted to identify factors influencing women with complicated pregnancies to attend referrals for additional care. METHODS: Women who received referral due to ANC ultrasound findings participated in structured interviews to characterize their experiences. Cochran-Mantel-Haenszel statistics were used to examine differences between women who attended the referral and women who did not. Sonographers\u27 exam findings were compared to referred women\u27s recall. RESULTS: Among 700 referred women, 510 (71%) attended the referral. Among referred women, 97% received a referral card to present at the hospital, 91% were told where to go in the hospital, and 64% were told that the hospital was expecting them. The referred women who were told who to see at the hospital (88% vs 66%), where to go (94% vs 82%), or what should happen, were more likely to attend their referral (68% vs 56%). Barriers to attending referrals were cost, transportation, and distance. Barriers after reaching the hospital were substantial. These included not connecting with an appropriate provider, not knowing where to go, and being told to return later. These barriers at the hospital often led to an unsuccessful referral. CONCLUSIONS: Our study found that ultrasound screening at ANC alone does not adequately address barriers to referrals. Better communication between the sonographer and the patient increases the likelihood of a completed referral. These types of communication include describing the ultrasound findings, including the reason for the referral, to the mother and staff; providing a referral card; describing where to go in the hospital; and explaining the procedures at the hospital. Thus, there are three levels of communication that need to be addressed to increase completion of appropriate referrals-communication between the sonographer and the woman, the sonographer and the clinic staff, and the sonographer and the hospital