Flipping the Winner of a Poset Game

Partially-ordered set games, also called poset games, are a class of two-player combinatorial games. The playing field consists of a set of elements, some of which are greater than other elements. Two players take turns removing an element and all elements greater than it, and whoever takes the last element wins. Examples of poset games include Nim and Chomp. We investigate the complexity of computing which player of a poset game has a winning strategy. We give an inductive procedure that modifies poset games to change the nim- value which informally captures the winning strategies in the game. For a generic poset game G, we describe an efficient method for constructing a game not G such that the first player has a winning strategy if and only if the second player has a winning strategy on G. This solves the long-standing problem of whether this construction can be done efficiently. This construction also allows us to reduce the class of Boolean formulas to poset games, establishing a lower bound on the complexity of poset games

Melt-driven erosion in microparticle impact

Impact-induced erosion is the ablation of matter caused by being physically struck by another object. While this phenomenon is known, it is empirically challenging to study mechanistically because of the short timescales and small length scales involved. Here, we resolve supersonic impact erosion in situ with micrometer- and nanosecond-level spatiotemporal resolution. We show, in real time, how metallic microparticles (~10-μm) cross from the regimes of rebound and bonding to the more extreme regime that involves erosion. We find that erosion in normal impact of ductile metallic materials is melt-driven, and establish a mechanistic framework to predict the erosion velocity.United States. Department of Energy. Division of Materials Sciences and Engineering (Award DE-SC0018091)United States. Army Research Office (Contract No. W911NF-13-D-0001)United States. Army Research Office (Contract No. (W911NF-18-2-0048)United States. Office of Naval Research. Defense University Research Instrumentation Program (Grant No. N00014-13-1-0676

Direct correlation of crystal structure and optical properties in wurtzite/zinc-blende GaAs nanowire heterostructures

A novel method for the direct correlation at the nanoscale of structural and optical properties of single GaAs nanowires is reported. Nanowires consisting of 100% wurtzite and nanowires presenting zinc-blende/wurtzite polytypism are investigated by photoluminescence spectroscopy and transmission electron microscopy. The photoluminescence of wurtzite GaAs is consistent with a band gap of 1.5 eV. In the polytypic nanowires, it is shown that the regions that are predominantly composed of either zinc-blende or wurtzite phase show photoluminescence emission close to the bulk GaAs band gap, while regions composed of a nonperiodic superlattice of wurtzite and zinc-blende phases exhibit a redshift of the photoluminescence spectra as low as 1.455 eV. The dimensions of the quantum heterostructures are correlated with the light emission, allowing us to determine the band alignment between these two crystalline phases. Our first-principles electronic structure calculations within density functional theory, employing a hybrid-exchange functional, predict band offsets and effective masses in good agreement with experimental results

Comparing pediatric gastroenteritis emergency department care in Canada and the United States

BACKGROUND: Between-country variation in health care resource use and its impact on outcomes in acute care settings have been challenging to disentangle from illness severity by using administrative data. METHODS: We conducted a preplanned analysis employing patient-level emergency department (ED) data from children enrolled in 2 previously conducted clinical trials. Participants aged 3 to,48 months with,72 hours of gastroenteritis were recruited in pediatric EDs in the United States (N = 10 sites; 588 participants) and Canada (N = 6 sites; 827 participants). The primary outcome was an unscheduled health care provider visit within 7 days; the secondary outcomes were intravenous fluid administration and hospitalization at or within 7 days of the index visit. RESULTS: In adjusted analysis, unscheduled revisits within 7 days did not differ (adjusted odds ratio [aOR]: 0.72; 95% confidence interval (CI): 0.50 to 1.02). At the index ED visit, although participants in Canada were assessed as being more dehydrated, intravenous fluids were administered more frequently in the United States (aOR: 4.6; 95% CI: 2.9 to 7.1). Intravenous fluid administration rates did not differ after enrollment (aOR: 1.4; 95% CI: 0.7 to 2.8; US cohort with Canadian as referent). Overall, intravenous rehydration was higher in the United States (aOR: 3.8; 95% CI: 2.5 to 5.7). Although hospitalization rates during the 7 days after enrollment (aOR: 1.1; 95% CI: 0.4 to 2.6) did not differ, hospitalization at the index visit was more common in the United States (3.9% vs 2.3%; aOR: 3.2; 95% CI: 1.6 to 6.8). CONCLUSIONS: Among children with gastroenteritis and similar disease severity, revisit rates were similar in our 2 study cohorts, despite lower rates of intravenous rehydration and hospitalization in Canadian-based EDs

Variables Associated with Intravenous Rehydration and Hospitalization in Children with Acute Gastroenteritis: A Secondary Analysis of 2 Randomized Clinical Trials

Importance: Despite guidelines endorsing oral rehydration therapy, intravenous fluids are commonly administered to children with acute gastroenteritis in high-income countries. Objective: To identify factors associated with intravenous fluid administration and hospitalization in children with acute gastroenteritis. Design, Setting, and Participants: This study is a planned secondary analysis of the Pediatric Emergency Research Canada (PERC) and Pediatric Emergency Care Applied Research Network (PECARN) probiotic trials. Participants include children aged 3 to 48 months with 3 or more watery stools in 24 hours between November 5, 2013, and April 7, 2017, for the PERC study and July 8, 2014, and June 23, 2017, for the PECARN Study. Children were from 16 pediatric emergency departments throughout Canada (6) and the US (10). Data were analyzed from November 2, 2018, to March 16, 2021. Exposures: Sex, age, preceding health care visit, distance between home and hospital, country (US vs Canada), frequency and duration of vomiting and diarrhea, presence of fever, Clinical Dehydration Scale score, oral ondansetron followed by oral rehydration therapy, and infectious agent. Main Outcomes and Measures: Intravenous fluid administration and hospitalization. Results: This secondary analysis of 2 randomized clinical trials included 1846 children (mean [SD] age, 19.1 [11.4] months; 1007 boys [54.6%]), of whom 534 of 1846 (28.9%) received oral ondansetron, 240 of 1846 (13.0%) received intravenous rehydration, and 67 of 1846 (3.6%) were hospitalized. The following were independently associated with intravenous rehydration: higher Clinical Dehydration Scale score (mild to moderate vs none, odds ratio [OR], 8.73; 95% CI, 5.81-13.13; and severe vs none, OR, 34.15; 95% CI, 13.45-86.73); country (US vs Canada, OR, 6.76; 95% CI, 3.15-14.49); prior health care visit with intravenous fluids (OR, 4.55; 95% CI, 1.32-15.72); and frequency of vomiting (per 5 episodes, OR, 1.66; 95% CI, 1.39-1.99). The following were independently associated with hospitalization: higher Clinical Dehydration Scale score (mild to moderate vs none, OR, 11.10; 95% CI, 5.05-24.38; and severe vs none, OR, 23.55; 95% CI, 7.09-78.25) and country (US vs Canada, OR, 3.37; 95% CI, 1.36-8.40). Oral ondansetron was associated with reduced odds of intravenous rehydration (OR, 0.21; 95% CI, 0.13-0.32) and hospitalization (OR, 0.44; 95% CI, 0.21-0.89). Conclusions and Relevance: Intravenous rehydration and hospitalization were associated with clinical evidence of dehydration and lack of an oral ondansetron-supported oral rehydration period. Strategies focusing on oral ondansetron administration followed by oral rehydration therapy in children with dehydration may reduce the reliance on intravenous rehydration and hospitalization. Trial Registration: ClinicalTrials.gov Identifiers: NCT01853124 (PERC) and NCT01773967 (PECARN)

Observation of Exclusive Two-Body B Decays to Kaons and Pions

We have studied two-body charmless hadronic decays of B mesons into the final states $\pi\pi$, $K \pi$, and $KK$. Using 3.3 million $B\bar{B}$ pairs collected with the CLEO-II detector, we have made the first observation of the decays $B^0\to K^+\pi^-$, $B^+\to K^0\pi^+$, and the sum of $B^+ \to \pi^+\pi^0$ and $B^+ \to K^+\pi^0$ decays (an average over charge-conjugate states is always implied). We place upper limits on branching fractions for the remaining decay modes.Comment: 9 page postscript file, postscript file also available through http://w4.lns.cornell.edu/public/CLN

Biallelic disruption of DDX41 activity is associated with distinct genomic and immunophenotypic hallmarks in acute leukemia

IntroductionInherited DDX41 mutations cause familial predisposition to hematologic malignancies including acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS), with the majority of DDX41 mutated MDS/AMLs described to date harboring germline DDX41 and co-occurring somatic DDX41 variants. DDX41-AMLs were shown to share distinguishing clinical features such as a late AML onset and an indolent disease associated with a favorable outcome. However, genotype-phenotype correlation in DDX41-MDS/AMLs remain poorly understood.MethodsHere, we studied the genetic profile, bone marrow morphology and immunophenotype of 51 patients with DDX41 mutations. We further assessed the functional impact of ten previously uncharacterized DDX41 variants of uncertain significance.ResultsOur results demonstrate that MDS/AML cases harboring two DDX41 variants share specific clinicopathologic hallmarks that are not seen in other patients with monoallelic DDX41 related hematologic malignancies. We further showed that the features seen in these individuals with two DDX41 variants were concordant with biallelic DDX41 disruption.DiscussionHere, we expand on previous clinicopathologic findings on DDX41 mutated hematologic malignancies. Functional analyses conducted in this study unraveled previously uncharacterized DDX41 alleles and further illustrate the implication of biallelic disruption in the pathophysiology of this distinct AML entity

Constraints on the χ_(c1) versus χ_(c2) polarizations in proton-proton collisions at √s = 8 TeV

The polarizations of promptly produced χ_(c1) and χ_(c2) mesons are studied using data collected by the CMS experiment at the LHC, in proton-proton collisions at √s=8  TeV. The χ_c states are reconstructed via their radiative decays χ_c → J/ψγ, with the photons being measured through conversions to e⁺e⁻, which allows the two states to be well resolved. The polarizations are measured in the helicity frame, through the analysis of the χ_(c2) to χ_(c1) yield ratio as a function of the polar or azimuthal angle of the positive muon emitted in the J/ψ → μ⁺μ⁻ decay, in three bins of J/ψ transverse momentum. While no differences are seen between the two states in terms of azimuthal decay angle distributions, they are observed to have significantly different polar anisotropies. The measurement favors a scenario where at least one of the two states is strongly polarized along the helicity quantization axis, in agreement with nonrelativistic quantum chromodynamics predictions. This is the first measurement of significantly polarized quarkonia produced at high transverse momentum