Order Selection Problems in Hiring Pipelines

Motivated by hiring pipelines, we study two order selection problems in which applicants for a finite set of positions must be interviewed or made offers sequentially. There is a finite time budget for interviewing or making offers, and a stochastic realization after each decision, leading to computationally-challenging problems. In the first problem we study sequential interviewing, and show that a computationally-tractable, non-adaptive policy that must make offers immediately after interviewing is approximately optimal, assuming offerees always accept their offers. In the second problem, we assume that applicants have already been interviewed but only accept offers with some probability; we develop a computationally-tractable policy that makes offers for the different positions in parallel, which is approximately optimal even relative to a policy that does not need to make parallel offers. Our two results both generalize and improve the guarantees in the work of Purohit et al. on hiring algorithms, from 1/2 and 1/4 to approximation factors that are at least 1-1/e

Discrete conformal maps and ideal hyperbolic polyhedra

We establish a connection between two previously unrelated topics: a particular discrete version of conformal geometry for triangulated surfaces, and the geometry of ideal polyhedra in hyperbolic three-space. Two triangulated surfaces are considered discretely conformally equivalent if the edge lengths are related by scale factors associated with the vertices. This simple definition leads to a surprisingly rich theory featuring M\"obius invariance, the definition of discrete conformal maps as circumcircle preserving piecewise projective maps, and two variational principles. We show how literally the same theory can be reinterpreted to addresses the problem of constructing an ideal hyperbolic polyhedron with prescribed intrinsic metric. This synthesis enables us to derive a companion theory of discrete conformal maps for hyperbolic triangulations. It also shows how the definitions of discrete conformality considered here are closely related to the established definition of discrete conformality in terms of circle packings.Comment: 62 pages, 22 figures. v2: typos corrected, references added and updated, minor changes in exposition. v3, final version: typos corrected, improved exposition, some material moved to appendice

Una licitación combinatorial aplicada a la provisión de Internet a las escuelas de Buenos Aires

Una de las clases de licitación más estudiadas en la literatura es la multi-unidades, aquella en la que se licitan varios ítems idénticos. En este trabajo, definimos una nueva subclase de las licitaciones multi-unidades, que llamamos multi-unidades logística. La característica central de una licitación multi-unidades logística es que existen fuertes asimetrías de costos entre los oferentes a causa de consideraciones logísticas. Ciertas unidades pueden ser atractivas para una firma y no para otra, de acuerdo a dichas consideraciones, y lo contrario puede suceder en otras unidades a licitar. Este tipo de licitación aparece en la provisión de Internet en las escuelas de Buenos Aires, la capital de Argentina. En 2008, la ciudad de Buenos Aires debía licitar la conexión de Internet para sus 709 escuelas públicas. En este trabajo mostramos cómo fue diseñada la licitación para realizar la adjudicación minimizando el gasto de la ciudad destinado a este fin. En nuestro diseño, cada firma debe dar un precio general por el servicio mensual a ser brindado en cada escuela, descuentos por volumen en bandas prefijadas de antemano y el listado de escuelas en las que le interesa brindar el servicio. La licitación multi-unidades logística resultante se puede interpretar como una licitación combinatorial. Se implementó un modelo de programación lineal entera para obtener el conjunto de ofertas más conveniente para el estado.De acuerdo con los análisis presentados en este trabajo, se puede estimar que la ciudad de Buenos Aires obtuvo ahorros cercanos al 20% por implementar este nuevo modelo de licitación en lugar del formato de licitación originalmente propuesto.Fil: Bonomo, Flavia. Consejo Nacional de Invest.cientif.y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Instituto de Investigaciones Matematicas;Fil: Catalán, J.. Universidad de Chile. Fac. de Cs. Físicas y Matemáticas; Chile;Fil: Duran, Guillermo Alfredo. Universidad de Buenos Aires. Facultad de Cs.exactas y Naturales. Instituto de Calculo; Argentina;Fil: Epstein, R.. Universidad de Chile. Fac. de Cs. Físicas y Matemáticas; Chile;Fil: Jawtuschenko, Alexis Boris. Consejo Nacional de Invest.cientif.y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Instituto de Investigaciones Matematicas;Fil: Marenco, Nelida Silvia. Universidad Nacional de General Sarmiento. Instituto de Ciencias; Argentina

Combining Computational Fluid Dynamics and Agent-Based Modeling: A New Approach to Evacuation Planning

We introduce a novel hybrid of two fields—Computational Fluid Dynamics (CFD) and Agent-Based Modeling (ABM)—as a powerful new technique for urban evacuation planning. CFD is a predominant technique for modeling airborne transport of contaminants, while ABM is a powerful approach for modeling social dynamics in populations of adaptive individuals. The hybrid CFD-ABM method is capable of simulating how large, spatially-distributed populations might respond to a physically realistic contaminant plume. We demonstrate the overall feasibility of CFD-ABM evacuation design, using the case of a hypothetical aerosol release in Los Angeles to explore potential effectiveness of various policy regimes. We conclude by arguing that this new approach can be powerfully applied to arbitrary population centers, offering an unprecedented preparedness and catastrophic event response tool

US201 Study: A Phase 2, Randomized Proof-of-Concept Trial of Favipiravir for the Treatment of COVID-19

Background: Favipiravir is used to treat influenza, and studies demonstrate that it has antiviral activity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Methods: We performed a randomized, open-label, multicenter, phase 2 proof-of-concept trial of favipiravir in hospitalized adult patients with polymerase chain reaction (PCR)-positive coronavirus disease 2019 (COVID-19). Patients were randomized to standard of care (SOC) or favipiravir treatment (1800mg per os twice a day [b.i.d.] on day 1, followed by 1000mg b.i.d. for 13 days). The primary end point was time to viral clearance on day 29. Results: Fifty patients were enrolled and stratified by disease severity (critical disease, severe disease, or mild to moderate disease). Nineteen patients were censored from the event of viral clearance based on being SARS-CoV-2 PCR-negative at the study outset, being PCR-positive at day 29, or because of loss to follow-up. Data from the 31 remaining patients who achieved viral clearance show enhanced viral clearance in the favipiravir group compared with the SOC group by day 29, with 72% of the favipiravir group and 52% of the SOC group being evaluable for viral clearance through day 29. The median time to viral clearance was 16.0 days (90% CI, 12.0 to 29.0) in the favipiravir group and 30.0 days (90% CI, 12.0 to 31.0) in the SOC group. A post hoc analysis revealed an effect in the subgroup of patients who were neutralizing antibody-negative at randomization. Treatment-emergent adverse events were equally distributed between the groups. Conclusions: We demonstrate that favipiravir can be safely administered to hospitalized adults with COVID-19 and believe that further studies are warranted. ClinicalTrialsgov registration: NCT04358549

Root causes of intraoperative hypoglycemia: a case series.

STUDY OBJECTIVE: To describe the root causes of intraoperative hypoglycemic events. DESIGN: Retrospective analysis. SETTING: Large academic teaching hospital. MEASUREMENTS: Data from 80,379 ASA physical status 1, 2, 3, 4, and 5 surgical patients were reviewed. Blood glucose values, insulin, oral hypoglycemic medication doses, and doses of glucose or other medications for hypoglycemia treatment were recorded. MAIN RESULTS: Hypoglycemia in many patients had multiple etiologies, with many cases (8 of 17) involving preventable errors. The most common root causes of hypoglycemia were ineffective communication, circulatory shock, failure to monitor, and excessive insulin administration. CONCLUSION: Intraoperative hypoglycemia was rare, but often preventable. Better communication among providers and between providers and patients may reduce the number of intraoperative hypoglycemic events. Many transient episodes of hypoglycemia did not result in any apparent complications, rendering their clinical importance uncertain. Critically ill patients in circulatory shock represent a group that may require close glucose monitoring

Theoretical studies of 31P NMR spectral properties of phosphanes and related compounds in solution

Selected theoretical methods, basis sets and solvation models have been tested in their ability to predict 31P NMR chemical shifts of large phosphorous-containing molecular systems in solution. The most efficient strategy was found to involve NMR shift calculations at the GIAO-MPW1K/6-311++G(2d,2p)//MPW1K/6-31G(d) level in combination with a dual solvation model including the explicit consideration of single solvent molecules and a continuum (PCM) solvation model. For larger systems it has also been established that reliable 31P shift predictions require Boltzmann averaging over all accessible conformations in solution