Traffic-Emitted Amines Promote New Particle Formation at Roadsides.

New particle formation (NPF) is a major source of atmospheric aerosol particles, significantly influencing particle number concentrations in urban environments. High condensation and coagulation sinks at highly trafficked roadside sites should suppress NPF due to the low survival probability of clusters and new particles, however, observations show that roadside NPF is frequent and intense. Here, we investigate NPF at an urban background and roadside site in Central Europe using simultaneous measurements of sulfuric acid, amines, highly oxygenated organic molecules (HOMs), and particle number size distributions.

Unveiling the Role of Chirality in the Oxidation of Monoterpenes.

Monoterpene oxidation is a major contributor to the formation and growth of a secondary organic aerosol (SOA) in the atmosphere. Although most monoterpenes naturally exist in two enantiomeric forms, the impact of their molecular chirality on SOA formation has been neglected, in part due to the hypothesis that a precursor's chirality will not impact gaseous oxidation processes when considering achiral oxidants (e.g.

Ambient-Pressure Multischeme Chemical Ionization for Pesticide Detection: A MION-Orbitrap Mass Spectrometry Study.

This study explores pesticide detection with diverse ionization reagents by employing Multischeme chemical IONization inlet (MION) in conjunction with high-resolution Orbitrap mass spectrometry (MS). Various ionization schemes, specifically charging by Br and O in negative polarity, and by HO and CHOH in positive polarity, were investigated. The findings build on our previous work concerning pesticide detection using multischeme ionization and further demonstrate the effectiveness of the MION-MS methodology for detecting pesticides from complex standard mixtures and fruit extracts.

Rapid unimolecular reactions of acyl peroxy radicals: extending the structure-activity relationships.

Acyl peroxy radicals are especially efficient at forming organic accretion products in the troposphere, but they also have short lifetimes due to rapid unimolecular reactions. For this reason, we find it important to accurately represent the reactions of these species in structure-activity relationships estimating the unimolecular reactivity of atmospheric peroxy radicals. To address this, we performed multi-conformer transition state theory calculations to determine H-shift and ring closure reaction rates for aldehyde-substituted and unsaturated acyl peroxy radicals over a wide temperature range.

Selective Deuteration Reveals the Importance of Multiple Branching Pathways in α-Pinene Autoxidation.

The oxidation of monoterpenes is one of the largest single sources of atmospheric secondary organic aerosol (SOA) significantly impacting the climate and air quality. Still, the autoxidation mechanisms converting these volatile precursors to low-volatility condensable products remain elusive even for the most abundant monoterpene α-pinene. We studied the ozonolysis of α-pinene by combining advanced isotopic labeling and state-of-the-art chemical ionization mass spectrometry supported by quantum chemical calculations.

Deep learning initialized compressed sensing (Deli-CS) in volumetric spatio-temporal subspace reconstruction.

Object: Spatio-temporal MRI methods offer rapid whole-brain multi-parametric mapping, yet they are often hindered by prolonged reconstruction times or prohibitively burdensome hardware requirements. The aim of this project is to reduce reconstruction time using deep learning.

Materials And Methods: This study focuses on accelerating the reconstruction of volumetric multi-axis spiral projection MRF, aiming for whole-brain T1 and T2 mapping, while ensuring a streamlined approach compatible with clinical requirements.

Molecular dynamics-guided reaction discovery reveals endoperoxide-to-alkoxy radical isomerization as key branching point in α-pinene ozonolysis.

Secondary organic aerosols (SOAs) significantly impact Earth's climate and human health. Although the oxidation of volatile organic compounds (VOCs) has been recognized as the major contributor to the atmospheric SOA budget, the mechanisms by which this process produces SOA-forming highly oxygenated organic molecules (HOMs) remain unclear. A major challenge is navigating the complex chemical landscape of these transformations, which traditional hypothesis-driven methods fail to thoroughly investigate.

New particle formation from isoprene under upper-tropospheric conditions.

Aircraft observations have revealed ubiquitous new particle formation in the tropical upper troposphere over the Amazon and the Atlantic and Pacific oceans. Although the vapours involved remain unknown, recent satellite observations have revealed surprisingly high night-time isoprene mixing ratios of up to 1 part per billion by volume (ppbv) in the tropical upper troposphere. Here, in experiments performed with the CERN CLOUD (Cosmics Leaving Outdoor Droplets) chamber, we report new particle formation initiated by the reaction of hydroxyl radicals with isoprene at upper-tropospheric temperatures of -30 °C and -50 °C.

Blip-up blip-down circular EPI (BUDA-cEPI) for distortion-free dMRI with rapid unrolled deep learning reconstruction.

Purpose: BUDA-cEPI has been shown to achieve high-quality, high-resolution diffusion magnetic resonance imaging (dMRI) with fast acquisition time, particularly when used in conjunction with S-LORAKS reconstruction. However, this comes at a cost of more complex reconstruction that is computationally prohibitive. In this work we develop rapid reconstruction pipeline for BUDA-cEPI to pave the way for its deployment in routine clinical and neuroscientific applications.

Enhanced detection of aromatic oxidation products using NO chemical ionization mass spectrometry with limited nitric acid.

Nitrate ion-based chemical ionization mass spectrometry (NO -CIMS) is widely used for detection of highly oxygenated organic molecules (HOMs). HOMs are known to participate in molecular clustering and new particle formation and growth, and hence understanding the formation pathways and amounts of these compounds in the atmosphere is essential. However, the absence of analytical standards prevents robust quantification of HOM concentrations.

Spherical echo-planar time-resolved imaging (sEPTI) for rapid 3D quantitative and susceptibility imaging.

Purpose: To develop a 3D spherical EPTI (sEPTI) acquisition and a comprehensive reconstruction pipeline for rapid high-quality whole-brain submillimeter and QSM quantification.

Methods: For the sEPTI acquisition, spherical k-space coverage is utilized with variable echo-spacing and maximum k ramp-sampling to improve efficiency and signal incoherency compared to existing EPTI approaches. For reconstruction, an iterative rank-shrinking B estimation and odd-even high-order phase correction algorithms were incorporated into the reconstruction to better mitigate artifacts from field imperfections.

Road Traffic Emissions Lead to Much Enhanced New Particle Formation through Increased Growth Rates.

New particle formation (NPF) is a major source of atmospheric aerosol particles, including cloud condensation nuclei (CCN), by number globally. Previous research has highlighted that NPF is less frequent but more intense at roadsides compared to urban background. Here, we closely examine NPF at both background and roadside sites in urban Central Europe.

Direct Measurements of Covalently Bonded Sulfuric Anhydrides from Gas-Phase Reactions of SO with Acids under Ambient Conditions.

Sulfur trioxide (SO) is an important oxide of sulfur and a key intermediate in the formation of sulfuric acid (HSO, SA) in the Earth's atmosphere. This conversion to SA occurs rapidly due to the reaction of SO with a water dimer. However, gas-phase SO has been measured directly at concentrations that are comparable to that of SA under polluted mega-city conditions, indicating gaps in our current understanding of the sources and fates of SO.

Gas-Phase Oxidation of Atmospherically Relevant Unsaturated Hydrocarbons by Acyl Peroxy Radicals.

This study assesses the atmospheric impact of reactions between unsaturated hydrocarbons such as isoprene and monoterpenes and peroxy radicals containing various functional groups. We find that reactions between alkenes and acyl peroxy radicals have reaction rates high enough to be feasible in the atmosphere and lead to high molar mass accretion products. Moreover, the reaction between unsaturated hydrocarbons and acyl peroxy radicals leads to an alkyl radical, to which molecular oxygen rapidly adds.

Cost-effective approach for atmospheric accretion reactions: a case of peroxy radical addition to isoprene.

We present an accurate and cost-effective method for investigating the accretion reactions between unsaturated hydrocarbons and oxidized organic radicals. We use accretion between isoprene and primary, secondary and tertiary alkyl peroxy radicals as model reactions. We show that a systematic semiempirical transition state search can lead to better transition state structures than relaxed scanning with density functional theory with a significant gain in computational efficiency.

High-resolution myelin-water fraction and quantitative relaxation mapping using 3D ViSTa-MR fingerprinting.

Purpose: This study aims to develop a high-resolution whole-brain multi-parametric quantitative MRI approach for simultaneous mapping of myelin-water fraction (MWF), T, T, and proton-density (PD), all within a clinically feasible scan time.

Methods: We developed 3D visualization of short transverse relaxation time component (ViSTa)-MRF, which combined ViSTa technique with MR fingerprinting (MRF), to achieve high-fidelity whole-brain MWF and T/T/PD mapping on a clinical 3T scanner. To achieve fast acquisition and memory-efficient reconstruction, the ViSTa-MRF sequence leverages an optimized 3D tiny-golden-angle-shuffling spiral-projection acquisition and joint spatial-temporal subspace reconstruction with optimized preconditioning algorithm.

Iodine oxoacids enhance nucleation of sulfuric acid particles in the atmosphere.

The main nucleating vapor in the atmosphere is thought to be sulfuric acid (HSO), stabilized by ammonia (NH). However, in marine and polar regions, NH is generally low, and HSO is frequently found together with iodine oxoacids [HIO, i.e.

Correction: Ring-opening yields and auto-oxidation rates of the resulting peroxy radicals from OH-oxidation of α-pinene and β-pinene.

[This corrects the article DOI: 10.1039/D2EA00133K.].

Evidence of nitrate-based nighttime atmospheric nucleation driven by marine microorganisms in the South Pacific.

Our understanding of ocean-cloud interactions and their effect on climate lacks insight into a key pathway: do biogenic marine emissions form new particles in the open ocean atmosphere? Using measurements collected in ship-borne air-sea interface tanks deployed in the Southwestern Pacific Ocean, we identified new particle formation (NPF) during nighttime that was related to plankton community composition. We show that nitrate ions are the only species for which abundance could support NPF rates in our semicontrolled experiments. Nitrate ions also prevailed in the natural pristine marine atmosphere and were elevated under higher sub-10 nm particle concentrations.

DTI-MR fingerprinting for rapid high-resolution whole-brain T , T , proton density, ADC, and fractional anisotropy mapping.

Purpose: This study aims to develop a high-efficiency and high-resolution 3D imaging approach for simultaneous mapping of multiple key tissue parameters for routine brain imaging, including T , T , proton density (PD), ADC, and fractional anisotropy (FA). The proposed method is intended for pushing routine clinical brain imaging from weighted imaging to quantitative imaging and can also be particularly useful for diffusion-relaxometry studies, which typically suffer from lengthy acquisition time.

Methods: To address challenges associated with diffusion weighting, such as shot-to-shot phase variation and low SNR, we integrated several innovative data acquisition and reconstruction techniques.

Calcium Sulfate Microparticle Size Modification for Improved Alginate Hydrogel Fabrication and Its Application in 3D Cell Culture.

Calcium ion-crosslinked alginate hydrogels are widely used as a materials system for investigating cell behavior in 3D environments . Suspensions of calcium sulfate particles are often used as the source of Ca to control the rate of gelation. However, the instability of calcium sulfate suspensions can increase chances of reduced homogeneity of the resulting gel and requires researcher's proficiency.