Two-body and three-body contacts for three bosons in the unitary regime: Analytic expressions and limiting forms

The two and three-body contacts are central to a set of univeral relations between microscopic few-body physics within an ultracold Bose gas and its thermodynamical properties. They may also be defined in trapped few-particle systems, which is the subject of this work. In this work, we focus on the unitary three-body problem in a trap, where interactions are as strong as allowed by quantum mechanics. We derive analytic results for the two and three-body contacts in this regime and compare with existing limiting expressions and previous numerical studies.Comment: 11 pages, 2 figures, Atoms special issue "Few-body Physics in Ultracold Quantum Gases

OH-Radical Oxidation of Lung Surfactant Protein B on Aqueous Surfaces

Air pollutants generate reactive oxygen species on lung surfaces. Here we report how hydroxyl radicals (·OH) injected on the surface of water react with SP-B_(1–25), a 25-residue polypeptide surrogate of human lung surfactant protein B. Our experiments consist of intersecting microjets of aqueous SP-B_(1–25) solutions with O_3/O_2/H_2O/N_2(g) gas streams that are photolyzed into ·OH(g) in situ by 266 nm laser nanosecond pulses. Surface-sensitive mass spectrometry enables us to monitor the prompt (<10 μs) and simultaneous formation of primary O_n-containing products/intermediates (n ≤ 5) triggered by the reaction of ·OH with interfacial SP-B_(1–25). We found that O-atoms from both O_3 and ·OH are incorporated into the reactive cysteine Cys_8 and Cys_(11) and tryptophan Trp_9 components of the hydrophobic N-terminus of SP-B_(1–25) that lies at the topmost layers of the air–liquid interface. Remarkably, these processes are initiated by ·OH additions rather than by H-atom abstractions from S–H, C–H, or N–H groups. By increasing the hydrophilicity of the N-terminus region of SP-B_(1–25), these transformations will impair its role as a surfactant

Assessing the Impact of Public Transfers on Private Risk Sharing Arrangements: Evidence from a Randomized Experiment in Mexico

We adopt a structural approach to studying the effects of public transfers on consumption smoothing, risk sharing and welfare in small village economies. We calibrate the key parameters of a dynamic limited commitment model using data gathered as part of the Mexican Progresa program, and take advantage of the randomized experimental design of the data to validate the model using the treatment sample. The limited commitment model enriched to allow for unobserved heterogeneity in preferences can reasonably well explain consumption dynamics and cross-sectional distributions. The calibrated model correctly predicts the increase in consumption smoothing of transfers’ recipients, and the decrease in risk sharing between beneficiaries and non beneficiaries of the program. Progresa transfers are found to crowd-out between 3% and 10% of the pre-existing private transfers, but the overall direct e,ect of the subsidy on consumption is welfare improving for all households. Last, we use our structural model to evaluate a counterfactual, fully funded, insurance scheme.Risk Sharing, Limited Commitment, Crowding-out, Transfers Programs

Assessing the Impact of Public Transfers on Private Risk Sharing Arrangements. Evidence from a Randomized Experiment in Mexico

We adopt a structural approach to studying the effects of public transfers on consumption smoothing, risk sharing and welfare in small village economies. We calibrate the key parameters of a dynamic limited commitment model using data gathered as part of the Mexican Progresa program, and take advantage of the randomized experimental design of the data to validate the model using the treatment sample. The limited commitment model enriched to allow for unobserved heterogeneity in preferences can reasonably well explain consumption dynamics and cross-sectional distributions. The calibrated model correctly predicts the increase in consumption smoothing of transfers’ recipients, and the decrease in risk sharing between beneficiaries and non beneficiaries of the program. Progresa transfers are found to crowd-out between 3% and 10% of the pre-existing private transfers, but the overall direct effect of the subsidy on consumption is welfare improving for all households. Last, we use our structural model to evaluate a counterfactual, fully funded, insurance scheme.Risk Sharing, Limited Commitment, Crowding-out, Transfers Programsd

Do Concentration Cells Store Charge in Water? Comment on Can Water Store Charge?

In a recent article, Ovchinnikova and Pollack (O&P)(1) reported that the persistent pH gradients (>100 min after electrolysis) generated upon charging a simple electrolytic cell (Pt electrodes in dilute aqueous NaCl solutions) imply that “water can store charge”, in apparent violation of the principle of electroneutrality in bulk macroscopic fluid phases

Proton Availability at the Air/Water Interface

The acidity of the water surface sensed by a colliding gas is determined in experiments in which the protonation of gaseous trimethylamine (TMA) on aqueous microjets is monitored by online electrospray mass spectrometry as a function of the pH of the bulk liquid (pH_(BLK)). TMAH^+ signal intensities describe a titration curve whose equivalence point at pH_(BLK) 3.8 is dramatically smaller than the acidity constant of trimethylammonium in bulk solution, pK_A(TMAH^+) = 9.8. Notably, the degree of TMA protonation above pH_(BLK) 4 is enhanced hundred-fold by submillimolar LiCl or NaCl and weakly inhibited at larger concentrations. Protonation enhancements are associated with the onset of significant direct kinetic solvent hydrogen isotope effects. Since TMA(g) can be protonated by H_2O itself only upon extensive solvent participation, we infer that H3O^+ emerges at the surface of neat water below pH_(BLK) 4

How Phenol and α-Tocopherol React with Ambient Ozone at Gas/Liquid Interfaces

The exceptional ability of α-tocopherol (α-TOH) for scavenging free radicals is believed to also underlie its protective functions in respiratory epithelia. Phenols, however, can scavenge other reactive species. Herein, we report that α-TOH/α-TO^− reacts with closed-shell O_3(g) on the surface of inert solvent microdroplets in <1 ms to produce persistent α-TO−O_n^−(n = 1−4) adducts detectable by online thermospray ionization mass spectrometry. The prototype phenolate PhO^−, in contrast, undergoes electron transfer under identical conditions. These reactions are deemed to occur at the gas/liquid interface because their rates: (1) depend on pH, (2) are several orders of magnitude faster than within microdroplets saturated with O_3(g). They also fail to incorporate solvent into the products: the same α-TO−On^− species are formed on acetonitrile or nucleophilic methanol microdroplets. α-TO−O_n(=1−3)^− signals initially evolve with [O_3(g)] as expected from first-generation species, but α-TO−O^− reacts further with O_3(g) and undergoes collisionally induced dissociation into a C_(19)H_(40) fragment (vs C_(19)H_(38) from α-TO^−) carrying the phytyl side chain, whereas the higher α-TO−O_(n≥2)^− homologues are unreactive toward O_3(g) and split CO_2 instead. On this basis, α-TO−O^− is assigned to a chroman-6-ol (4a, 8a)-ene oxide, α-TO−O2^− to an endoperoxide, and α-TO−O3^− to a secondary ozonide. The atmospheric degradation of the substituted phenols detected in combustion emissions is therefore expected to produce related oxidants on the aerosol particles present in the air we breathe

Prompt Formation of Organic Acids in Pulse Ozonation of Terpenes on Aqueous Surfaces

A major atmospheric process, the gas-phase ozonation of terpenes yields suites of products via a cascade of chemically activated intermediates that ranges from primary ozonides to dioxiranes. If a similar mechanism operated in water, as it is generally assumed, such intermediates would be deactivated within picoseconds and, henceforth, be unable to produce carboxylic acids in microseconds. Herein, we report the online electrospray mass spectrometric detection of (M + 2O – H^+) and (M + 3O – H^+) carboxylates on the surface of aqueous β-caryophyllene (C_(15)H_(24), M = 204 Da) microjets exposed to a few ppmv of O_3(g) for < 10 μs. Since neither species is formed on dry solvent microjets and both incorporate deuterium from D_2O, we infer that carboxylates ensue from the interaction of nascent intermediates with interfacial water via heretofore unreported processes. These interfacial events proceed much faster than those in bulk liquids saturated with ozone