Trends in Pediatric Cancer Care in Florida From 1981-2020: Changing Patterns in a Growing and Increasingly Diverse Population.

Background The Florida Association of Pediatric Tumor Programs (FAPTP) has used the Statewide Patient Information Reporting System (SPIRS) since 1981 to track all new cases of pediatric cancer. We reviewed the last 40 years of data to see how pediatric cancer care has evolved. Methods We retrospectively analyzed SPIRS data from 1981 through 2020 in five-year increments, looking at numbers of new diagnoses, care delivery sites, and trial enrollment in Children's Oncology Group (COG) studies. Results From 1981-2020 Florida's population increased almost 88% while the pediatric population only grew 61%. New pediatric cancer diagnoses increased 326% to over 1,000 new cases/year. The percentage of patients treated at FAPTP centers grew from 30% to 57% with an annual percentage change (APC) of 10.3% (95% Confidence Interval [CI] of 0.6 to 20.9%). The rate of COG clinical trial enrollment decreased from 32% in 1981-1985 to 20% in 2016-2020, for an APC of 8.91% (95% CI of -13.3 to -4.3%). Conclusions The striking increase in pediatric cancer cases in Florida over the last 40 years was out of proportion to the population growth. More patients received care at FAPTP centers, but a lower percentage were enrolled on COG trials.

Collisional excitation of HNC by He found to be stronger than for structural isomer HCN in experiments at the low temperatures of interstellar space.

HCN and its unstable isomer HNC are widely observed throughout the interstellar medium, with the HNC/HCN abundance ratio correlating strongly with temperature. In very cold environments HNC can even appear more abundant than HCN. Here we use a chirped pulse Fourier transform spectrometer to measure the pressure broadening of HCN and HNC, simultaneously formed in situ by laser photolysis and cooled to low temperatures in uniform supersonic flows of helium. Despite the apparent similarity of these systems, we find the HNC-He cross section to be more than twice as big as the HCN-He cross section at 10 K, confirming earlier quantum calculations. Our experimental results are supported by high-level scattering calculations and are also expected to apply with para-H2, demonstrating that HCN and HNC have different collisional excitation properties that strongly influence the derived interstellar abundances.

A novel Ka-band chirped-pulse spectrometer used in the determination of pressure broadening coefficients of astrochemical molecules.

A novel chirped-pulse Fourier transform microwave (CP-FTMW) spectrometer has been constructed to cover the Ka-band (26.5 GHz-40 GHz) for use in the CRESUCHIRP project, which aims to study the branching ratios of reactions at low temperatures using the chirped-pulse in uniform flow technique. The design takes advantage of recent developments in radio-frequency components, notably, high-frequency, high-power solid-state amplifiers. The spectrometer had a flatness of 5.5 dB across the spectral range, produced harmonic signals below -20 dBc, and the recorded signal scaled well to 6 × 106 averages. The new spectrometer was used to determine pressure broadening coefficients with a helium collider at room temperature for three molecules relevant to astrochemistry, applying the Voigt function to fit the magnitude of the Fourier-transformed data in the frequency domain. The pressure broadening coefficient for carbonyl sulfide was determined to be (2.45 ± 0.02) MHz mbar-1 at room temperature, which agreed well with previous measurements. Pressure broadening coefficients were also determined for multiple transitions of vinyl cyanide and benzonitrile. Additionally, the spectrometer was coupled with a cold, uniform flow from a Laval nozzle. The spectrum of vinyl cyanide was recorded in the flow, and its rotational temperature was determined to be (24 ± 11) K. This temperature agreed with a prediction of the composite temperature of the system through simulations of the experimental environment coupled with calculations of the solution to the optical Bloch equations. These results pave the way for future quantitative studies in low-temperature and high-pressure environments using CP-FTMW spectroscopy.

Broadband rotational spectroscopy of trans 3-pentenenitrile and 4-pentenenitrile.

Titan, a moon of Saturn, has a nitrogen- and methane-rich atmosphere that is similar to prebiotic earth, and is replete with organic nitriles. Pentenenitriles have not yet been detected in Titan's atmosphere or in molecular clouds, but are potential precursors to hetero-aromatic compounds such as pyridine. We performed broadband microwave studies in the 8-18 GHz range on the trans isomer of 3-pentenenitrile (3-PN) and 4-pentenenitrile (4-PN) under jet-cooled conditions. Strong-field coherence breaking (SFCB) was used to selectively modulate the intensities of microwave transitions in a conformer-specific manner for 3-PN, aiding analysis. Two conformers of 3-PN and five conformers of 4-PN were identified and the rotational transitions were assigned. Evidence for methyl internal rotation splitting was observed for both the conformers of 3-PN, and the barrier heights of both conformers was determined experimentally. Comparison is made of the conformational preferences, stability and isomerization barriers through the acquired rotational spectra and potential energy surface (PES) calculations of the structural isomers 3-PN and 4-PN.

Low Temperature Kinetics of the Reaction Between Methanol and the CN Radical.

Methanol (CH3OH) is considered by astronomers to be the simplest complex organic molecule (COM) and has been detected in various astrophysical environments, including protoplanetary disks, comets, and the interstellar medium (ISM). Studying the reactivity of methanol at low temperatures will aid our understanding of the formation of other complex and potentially prebiotic molecules. A major destruction route for many neutral COMs, including methanol, is via their reactions with radicals such as CN, which is ubiquitous in space. Here, we study the kinetics of the reaction between methanol and the CN radical using the well-established CRESU technique (a French acronym standing for Reaction Kinetics in Uniform Supersonic Flow) combined with Pulsed-Laser Photolysis-Laser-Induced Fluorescence (PLP-LIF). Electronic structure calculations were also performed to identify the exothermic channels through which this reaction can proceed. Our results for the rate coefficient are represented by the modified Arrhenius equation, k(T) = 1.26 × 10-11(T/300 K)-0.7 exp(-5.4 K/T), and display a negative temperature dependence over the temperature range 16.7-296 K, which is typical of what has been seen previously for other radical-neutral reactions that do not possess potential energy barriers. The rate coefficients obtained at room temperature strongly disagree with a previous kinetics study, which is currently available in the Kinetics Database for Astrochemistry (KIDA) and therefore used in some astrochemical models.

Multiplexed characterization of complex gas-phase mixtures combining chirped-pulse Fourier transform microwave spectroscopy and VUV photoionization time-of-flight mass spectrometry.

We report details of the design and operation of a single apparatus that combines Chirped-Pulse Fourier Transform Microwave (CP-FTMW) spectroscopy with vacuum ultraviolet (VUV) photoionization Time-of-Flight Mass Spectrometry (TOFMS). The supersonic expansion used for cooling samples is interrogated first by passing through the region between two microwave horns capable of broadband excitation and detection in the 2-18 GHz frequency region of the microwave. After passing through this region, the expansion is skimmed to form a molecular beam, before being probed with 118 nm (10.5 eV) single-photon VUV photoionization in a linear time-of-flight mass spectrometer. The two detection schemes are powerfully complementary to one another. CP-FTMW detects all components with significant permanent dipole moments. Rotational transitions provide high-resolution structural data. VUV TOFMS provides a gentle and general method for ionizing all components of a gas phase mixture with ionization thresholds below 10.5 eV, providing their molecular formulae. The advantages, complementarity, and limitations of the combined methods are illustrated through results on two gas-phase mixtures made up of (i) three furanic compounds, two of which are structural isomers of one another, and (ii) the effluent from a flash pyrolysis source with o-guaiacol as the precursor.

AC Stark Effect Observed in a Microwave-Millimeter/Submillimeter Wave Double-Resonance Experiment.

Microwave-millimeter/submillimeter wave double-resonance spectroscopy has been developed with the use of technology typically employed in chirped pulse Fourier transform microwave spectroscopy and fast-sweep direct absorption (sub)millimeter-wave spectroscopy. This technique offers the high sensitivity provided by millimeter/submillimeter fast-sweep techniques with the rapid data acquisition offered by chirped pulse Fourier transform microwave spectrometers. Rather than detecting the movement of population as is observed in a traditional double-resonance experiment, instead we detected the splitting of spectral lines arising from the AC Stark effect. This new technique will prove invaluable when assigning complicated rotational spectra of complex molecules. The experimental design is presented along with the results from the double-resonance spectra of methanol as a proof-of-concept for this technique.

Fast sweep direct absorption (sub)millimeter-wave spectroscopy.

Direct absorption spectroscopy has been the mainstay for spectral acquisition in the millimeter and submillimeter wavelength regimes because of the sensitivity offered by standard hot electron bolometer detectors. However, this approach is limited in its utility because of the slow spectral acquisition speeds. A few rapid acquisition techniques that offer reasonable levels of sensitivity have been developed, but these rely on specialized and costly equipment. We present here a new instrument design for a (sub)millimeter spectrometer that offers both rapid spectral acquisition and highly sensitive detection while using equipment from existing chirped-pulse Fourier transform spectrometers and direct absorption spectrometers. We report on spectrometer design and performance and compare the results to standard lock-in detection techniques.

Weakly Bound Clusters in Astrochemistry? Millimeter and Submillimeter Spectroscopy of trans-HO3 and Comparison to Astronomical Observations.

The emergence of chemical complexity during star and planet formation is largely guided by the chemistry of unstable molecules that are reaction intermediates in terrestrial chemistry. Our knowledge of these intermediates is limited by both the lack of laboratory studies and the difficulty in their astronomical detection. In this work, we focus on the weakly bound cluster HO3 as an example of the connection between laboratory spectroscopic study and astronomical observations. Here, we present a fast-sweep spectroscopic technique in the millimeter and submillimeter range to facilitate the laboratory search for trans-HO3 and DO3 transitions in a discharge supersonic jet and report their rotational spectra from 70 to 450 GHz. These new measurements enable full determination of the molecular constants of HO3 and DO3. We also present a preliminary search for trans-HO3 in 32 star-forming regions using this new spectroscopic information. HO3 is not detected, and column density upper limits are reported. This work provides additional benchmark information for computational studies of this intriguing radical, as well as a reliable set of molecular constants for extrapolation of the transition frequencies of HO3 for future astronomical observations.

Multipass millimeter/submillimeter spectrometer to probe dissociative reaction dynamics.

We present here the instrument design and first experimental results from a multipass millimeter/submillimeter spectrometer designed to probe dissociative reaction dynamics. This work focuses on benchmarking the instrument performance through detection of the CH3O and H2CO products from methanol dissociation induced by a high-voltage plasma discharge. Multiple rotational lines from CH3O and H2CO were observed when this plasma discharge was applied to a sample of methanol vapor seeded in an argon supersonic expansion. The rotational temperature of the dissociation products and their abundance with respect to methanol were determined using a Boltzmann analysis. The minimum detectable absorption coefficient for this instrument was determined to be αmin ≤ 5 × 10(-9) cm(-1). We discuss these results in the context of future applications of this instrument to the study of photodissociation branching ratios for small organic molecules that are important in complex interstellar chemistry.

Theoretical examination of O((1)D) insertion reactions to form methanediol, methoxymethanol, and aminomethanol.

A computational study of O((1)D) insertion reactions with methanol (CH3OH), dimethyl ether (CH3OCH3), and methyl amine (CH3NH2) was performed to guide laboratory investigations of the insertion product molecules methanediol (HOCH2OH), methoxymethanol (CH3OCH2OH), and aminomethanol (HOCH2NH2), respectively. The minimum energy and higher energy conformer geometries of the products were determined at the MP2/aug-cc-pVTZ level of theory, and CCSD(T)/aug-cc-pVTZ calculations were performed on the reactants, products, and transitions states to examine the insertion reaction energetics. Torsional barriers for internal motion in methanediol, methoxymethanol, and aminomethanol were also determined. It was found that O((1)D) insertion into the C-H bond was the most energetically favored reaction pathway, proceeding through a direct and barrierless insertion mechanism. The pathways of O((1)D) insertion into N-H or O-H bonds are also possible, though these reactions are less energetically favored, as they proceed through an association product intermediate before proceeding to the insertion products. Predictions are presented for the pure rotational spectra for the methanediol, methoxymethanol, and aminomethanol products based on the determined molecular parameters. These results provide an excellent starting point to guide laboratory spectral studies of the products.