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Introduction: The introduction of trapped ion mobility spectrometry (TIMS) in combination with fast high-resolution time-of-flight (TOF) mass spectrometry to the proteomics field led to a jump in protein identifications and quantifications, as well as a lowering of the limit of detection for proteins from biological samples. Parallel Accumulation-Serial Fragmentation (PASEF) is a driving force for this development and has been adapted to discovery as well as targeted proteomics. Areas covered: Over the last decade, the PASEF concept has been optimized and led to the implementation of eleven new measurement techniques. In this review, we describe all currently described PASEF measurement techniques and their application to clinical proteomics. Literature was searched using PubMed and Google Scholar search engines. Expert Opinion: The use of a dual TIMS tunnel has revolutionized the depth and the speed of proteomics measurements. Currently, we witness how this technique is pushing clinical proteomics forward. [ABSTRACT FROM AUTHOR]

This study established a simple, rapid, and sensitive ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method for the simultaneous quantification of contezolid and its major metabolite M2 in human plasma and cerebrospinal fluid (CSF). We used isotope-labeled internal standards (IS) along with protein precipitation to efficiently eliminate impurities. The ion transition was m/z 409.1 → 269.1 for contezolid, m/z 414.1 → 269.0 for contezolid-d5, m/z 445.1 → 385.1 for M2, and m/z 450.2 → 390.1 for M2-d5. The flow rate was 0.4 mL/min with a run time of 2.5 min. Validation results demonstrated that the calibration range was 10–5000 ng/mL for contezolid, and 5–2500 ng/mL for M2 in plasma and CSF. Both analytes exhibit excellent linear relationships (all R2 ≥ 0.99). Intra- and inter-batch accuracy and precision for all quality control (QC) levels were within ± 15%, including the lower limit of quantification (LLOQ). The recoveries of contezolid and M2 were 92.60–100.4% and 92.26–99.61% in plasma and 93.33–99.19% and 91.31–98.21% in CSF, respectively. The matrix effects for contezolid and M2 were 97.20–110.3% and 98.27–105.47% in plasma and 105.25–112.99% and 103.35–109.84% in CSF, respectively. The coefficients of variation (CV%) were ≤ 12.58%. Conteozolid and M2 remained stable in plasma and CSF. This study has established a simple and accurate method for determining contezolid and M2 in human plasma and CSF, making it a valuable tool for monitoring the efficacy of central nervous system (CNS) drugs. [ABSTRACT FROM AUTHOR]

The pharmaceutical industry continues to expand its search for innovative biotherapeutics. The comprehensive characterization of such therapeutics requires many analytical techniques to fully evaluate critical quality attributes, making analysis a bottleneck in discovery and development timelines. While thorough characterization is crucial for ensuring the safety and efficacy of biotherapeutics, there is a need to further streamline analytical characterization and expedite the overall timeline from discovery to market. This review focuses on recent developments in liquid-phase separations coupled with ion mobility-mass spectrometry (IM-MS) for the development and characterization of biotherapeutics. We cover uses of IM-MS to improve the characterization of monoclonal antibodies, antibody-drug conjugates, host cell proteins, glycans, and nucleic acids. This discussion is based on an extensive literature search using Web of Science, Google Scholar, and SciFinder. IM-MS has the potential to enhance the depth and efficiency of biotherapeutic characterization by providing additional insights into conformational changes, post-translational modifications, and impurity profiles. The rapid timescale of IM-MS positions it well to enhance the information content of existing assays through its facile integration with standard liquid-phase separation techniques that are commonly used for biopharmaceutical analysis. [ABSTRACT FROM AUTHOR]

Metabolomics aims to profile the extensive array of metabolites that exists in different types of matrices using modern analytical techniques. These techniques help to separate, identify, and quantify the plethora of chemical compounds at various analytical platforms. Hence, ion mobility spectrometry (IMS) has emerged as an advanced analytical approach, exclusively owing to the 3D separation of metabolites and their isomers. Furthermore, separated metabolites are identified based on their mass fragmentation pattern and CCS (collision cross-section) values. The IMS provides an advanced alternative dimension to separate the isomeric metabolites with enhanced throughput with lesser chemical noise. Thus, the present review highlights the types, factors affecting the resolution, and applications of IMMS (Ion mobility mass spectrometry) for isomeric separations, and ionic contaminants in the plant samples. Furthermore, an overview of IMS-based applications for the identification of plant metabolites (volatile and non-volatile) over the last few decades has been discussed, followed by future assumptions for creating IM-based databases. Such approaches could be significant to accelerate and improve our knowledge of the vast chemical diversity found in plants. [ABSTRACT FROM AUTHOR]

A portable high-field asymmetric ion transfer spectrometer (FAIMS) was miniaturized to improve the design. The prototype consists of a main controller, a galvanometer, a high-voltage square-wave power supply, a Raspberry Pi module, and integrated circuitry. The new design eliminates a main power supply and meets the high- and low-voltage requirements. Qt, a cross-platform software package for creating graphical user interfaces, was used to map the molecular structure fingerprint. The timing, circuit structure, and mechanical assembly were optimized. The dimensions were 45 cm × 48 cm × 23 cm. 16 s were required to collect 1000 data points; the usage time exceeded 8 h, and the background noise was approximately 0.2 pA. The prototype offers excellent efficiency, stability, and multiple applications. The accuracy of FAIMS with the deep-learning model for data acquisition is good. This system is anticipated to evaluate the concentrations of volatiles in diverse types of samples. [ABSTRACT FROM AUTHOR]

This study isolated two dominant molds (Penicillium chrysogenum and Aspergillus sydowii) from cigar tobacco leaves. Gas chromatography–ion mobility spectrometry (GC–IMS) was used for rapid qualitative and semi-quantitative analysis of mold growing from 0 to 7 days on potato dextrose agar (PDA). GC–IMS fingerprint, galleryplot, one-way analysis of variance (ANOVA), and partial least squares – discriminant analysis (PLS-DA) were used to assess different periods of cigar tobacco mildew. ANOVA and PLS-DA were compared to identify possible mildew markers in PDA. The potential mildew markers were verified using 0–7 days of artificial mildew samples. The results showed that 1-octene-3-alcohol, 1-pentanol, and pentanal were characteristic markers of early mildew in cigar tobacco. In conclusion, GC–IMS and chemometrics enables early warning of cigar tobacco mold, which is of great significance for storage and quality control. [ABSTRACT FROM AUTHOR]

Solid polymer electrolytes (SPEs) have been recognized as a preferable alternative to liquid electrolytes for energy storage application. However, low conductivity of SPEs has restricted their application. This issue can be overcome by adding controlled amount of dopant salt to the SPEs. In this work, various concentration of ammonium thiocyanate (NH4SCN) salt was incorporated into dextran using solution cast technique in order to study the effect of NH4SCN on electrical properties, crystallite size, morphology and ionic conductivity. Results from Fourier-transform infrared (FTIR) analysis confirm the coordination of cation of salt at the OH and C-O-C groups of dextran. Deconvolution of the FTIR band between 2015 and 2090 cm−1 was performed to investigate the ion association and dissociation phenomena. It is confirmed that the ion mobility and diffusion are directly proportional to the ionic conductivity. Based on the electrochemical impedance spectroscopy (EIS) result, an optimum ionic conductivity of (3.18 ± 1.19) × 10−4 S cm−1 was achieved with the sample containing 40 wt.% salt concentration. The conductivity result can be clarified by the crystallite size obtained from X-ray diffraction (XRD) analysis and field emission scanning electron microscopy (FESEM) images. [ABSTRACT FROM AUTHOR]

The conformational changes of lysozyme due to the formation of its complexes with polystyrene sulfonate (PSS) oligomers were monitored at different charge states using trapped ion mobility spectrometry-time-of-flight mass spectrometer (TIMS-TOF-MS). The mixtures of disulfide-intact lysozyme and PSS oligomers were directly infused into the ESI source of the TIMS-TOF-MS instrument. At charge states from 7+ to 12+ in the gas phase, mobilograms obtained from TIMS-TOF-MS analyses were extracted for the protein and each complex ion. Changes occurring in the protein conformation as a result of the binding of PSS oligomers of different chain lengths were evaluated by comparing the obtained integrated peak areas for compact and extended conformers in the extracted ion mobilograms. The increase in the abundance of compact conformers due to the complexation of lysozyme and PSS oligomers was observed more clearly in the 8+ charge state. The number and lengths of PSS chains had little or no effect on the complex conformation in the higher charge states that did not provide compaction in the entire structure. It was observed that the molecular dynamics (MD) simulations of the protein and complexes correlate well with the results obtained by TIMS-TOF-MS. The PSS chains interact with the positively charged sites of the protein and cause compaction in the conformation by changing the locations of the excess charge on the structure in the gas phase that was monitored using TIMS regarding the length and number of the attached polyelectrolyte chain. [ABSTRACT FROM AUTHOR]

Electrospray ionization ion mobility mass spectrometry (ESI-IMS—MS) is a rapidly progressing analytical technique for the examination of complex compounds in the gas phase. ESI-IMS—MS separates isomers, provides structural information, and quantitatively identifies peptides, lipids, carbohydrates, polymers, and metabolites in biological samples. ESI-IMS—MS has pharmaceutical, environmental, and manufacturing applications quickly characterizing drugs, petroleum products, and metal macromolecules. This review provides the history of ESI-IMS—MS development and applications to date. [ABSTRACT FROM AUTHOR]

The emission of vapors from solid samples of Pentaerythritol Tetranitrate (PETN) in a flow of nitrogen from ~20 to 140°C was characterized using atmospheric pressure chemical ionization mass spectrometry equipped with a 63Ni ion source. Mass analysis of ions derived from vapors from military grade PETN at room temperature, without deposition from solution, included only NO3− (62 Da) and HNO3·NO3− (125 Da) and were attributed to residual levels of nitric acid in the PETN solid. The vapor level of HNO3 persisted until 80°C and after this declined asymptotically to background levels; ions observed above 110°C were nitrate adducts of molecular PETN including (PETN)n·NO3− with mass values of 378 Da (n = 1) and 695 Da (n = 2). Subsequent reheating of the PETN solid caused an increase release of nitric acid and formation, above 140°C, of the same nitrate adducts of PETN,, consistent with thermal degradation of some PETN to nitric acid. A commercial handheld ion mobility spectrometer was used to sample airborne vapors from solid PETN in an open container and heated in ambient air. The ion mobility spectra showed that ionization chemistry was rapidly transformed from O2− to NO3− which persisted indefinitely and produced ion above 80°C with Ko values of 1.48, 1.21, 1.15, and 1.10 cm2/V s. These relatively low-mobility peaks were attributed to cluster ions of nitrate with nitric acid and molecular PETN generated from thermal decomposition and some vaporization of solid PETN. Persistence of nitrate as a reactant ion in the handheld analyzer suggested a need for specialized designs and materials for such explosives vapor measurements. [ABSTRACT FROM AUTHOR]

Intrinsically disordered proteins (IDPs) represent a family of proteins that lack secondary or tertiary structure. IDPs are hubs in interaction networks, participate in liquid–liquid phase separation processes, and drive the formation of proteinaceous membrane-less organelles. Their unfolded structure makes them particularly prone to post-translational modifications (PTMs) that play key functional modulatory roles. We discuss different analytical approaches to study phosphorylation of IDPs starting from methods for IDP enrichment (strong acid extractions and heat-based pre-fractionation), strategies to enrich and map phosphopeptides/proteins, and mass spectrometry-based tools to study the phosphorylation-dependent conformational alterations of IDPs (limited proteolysis, HDX, chemical cross-linking, covalent labeling, and ion mobility). There is a growing interest in IDPs and their PTMs since they are involved in several diseases. The intrinsic disorder could be exploited to facilitate purification and synthetic production of IDPs taking full advantage of those structural mass-spectrometry-based methods that can be used to investigate IDPs and their phospho-dependent conformational alterations. The diffusion and implementation of mass spectrometers with ion mobility devices and electron transfer dissociation capabilities could be key-elements for increasing information on IDP biology. [ABSTRACT FROM AUTHOR]

Challenges, strategies and new technologies in the field of biotransformation were presented and discussed at the 3rd European Biotransformation Workshop which was held in collaboration with the DMDG on 5–6 October 2022 in Amsterdam. In this meeting report we summarise the presentations and discussions from this workshop. The topics covered are listed below: Accelerator mass spectrometry (AMS) for the support of microtracer studies Biotransformation of the novel myeloperoxidase inhibitor AZD4831 in preclinical species and humans AMS in biotransformation studies: unusual case studies Discussion on new FDA draft guidance and AMS Multimodal molecular imaging and ion mobility applications in drug discovery and development Metabolites in Safety Testing considerations for large molecules [ABSTRACT FROM AUTHOR]

Ion mobility spectrometry coupled to gas-chromatographic (GC-IMS) is tested regarding their ability to analyze various refined edible vegetable oils, including sunflower seed, rapeseed, sesame, soybean, peanut, corn, camellia, linseed, walnut, coconut, grape seed and extra virgin olive oils. GC-IMS assay displays peak difference of each edible vegetable oil in three-dimensional information at retention time in gas phase and at ion mobility rate in IMS. Moreover, 74 main peak intensities are extracted and imported into Excel for analysis. Then, chemometric methods are employed to establish discriminant models. The results show that based on Kennards-Stone (KS), the prediction accuracy of the soft independent modeling of class analogy (SIMCA) is perfect. Therefore, the GC-IMS system is shown to be an effective method to classification of edible vegetable oils. [ABSTRACT FROM AUTHOR]

Developing precise, reliable and rapid techniques for measuring hazardous materials in the environment is of crucial importance. In this paper, corona discharge ionization ion mobility spectrometry (IMS) was used for detecting and quantifying diazinon in soil samples. We optimized and calibrated a solid-liquid extraction procedure in soil and washed sand samples. Various parameters including solvent type and volume, agitation, centrifugation, solvent ionic strength and filtration were examined and the optimum condition was adopted. Results indicated that methanol was the most efficient solvent for the extraction of diazinon, recovered best by 5 minutes centrifugation at 4000 rpm after 2 hours of shaking. The recovery values for shaking and sonication were 80 and 76 for the soil sample and 89 and 80 for the sand sample, respectively. Filtration could not influence the recovery values. The method was successfully applied to three different soils, spiked with different diazinon concentrations and the obtained recovery values ranged between 95% and 104%. Overall, the proposed method is efficient enough to be routinely used for diazinon determination in soil samples. [ABSTRACT FROM AUTHOR]

Azobenzene macrocycles are widely investigated as potential drug delivery systems and as part of molecular machines due to their photo-responsive properties. Herein, we detect the formation of a series of new azobenzene macrocycles that feature up to eight switchable repeating units. High-resolution mass spectrometry and ion mobility (IM) mass spectrometry experiments and 1H and diffusion-ordered spectroscopy (DOSY) NMR are used to detect the presence of the macrocycles that contain 10 to 40 aromatic rings in the gas phase and solution, respectively. The responsiveness of the Z-to-E photo-switching of the smallest of the macrocycles, exhibiting two azobenzene units and in total 10 aromatic rings, separated with column chromatography, is studied with irradiation experiments, using both UV-Vis light and thermal excitation and relaxation, and monitoring the sample with UV-Vis absorption and 1H NMR spectroscopy. DFT calculations are used to understand the conformation of this isolated species in solution. [ABSTRACT FROM AUTHOR]

A selective GC-MS method was developed and evaluated for the determination of genotoxic impurities Chloroacetic acid (Cl-AcOH) and Dichloroacetic acid (DCl-AcOH) in Armodafinil (AMD) drug substance. Chromatographic separation of Cl-AcOH and DCl-AcOH was achieved on DB-624 column (30 m x 0.32 mm, 1.8 µm), which contains 6% cyanopropylphenyl and 94% dimethylpolysiloxane stationary phase by helium carrier gas. Mass fragment m/z 59 was selected for the quantification of both Cl-AcOH and DCl-AcOH impurities. Further, mass fragments m/z=108 was selected for Cl-AcOH and m/z=83 was selected for DCl-AcOH as qualifier ion. The performance of the method was assessed by evaluating the specificity, linearity, sensitivity, precision and accuracy experiments. The limits of detection (LOD) and limits of quantification (LOQ) values for Cl-AcOH were 0.00003 µg mL−1, 0.00009 µg mL−1 and for DCl-AcOH analyte were 0.00003 µg mL−1 and 0.00009 µg mL−1 respectively. The correlation coefficient values of linearity experiment were 0.9929 for Cl-AcOH, 0.9908 for DCl-AcOH. The average recovery for Cl-AcOH was in the range of 104.7% to 111.4% and for DCl-AcOH was in the range of 108.2% to 111.7%. The results proved that the method is suitable for the determination of Cl-AcOH and DCl-AcOH contents in Armodafinil drug substance and method can be successfully applied in the quality control analysis. [ABSTRACT FROM AUTHOR]

The aim of this study is identification, isolation, structural characterization and qualification of degradation products DP-1, DP-2, DP-3 and DP-4. These impurities are major acid hydrolysis degradation products identified i n Osimertinib M esylate (OSM) Tablets. T he O SM i s o bserved s table u nder thermal, photolytic and neutral conditions. The degradation of drug is observed under acidic, basic and oxidative conditions. Basic and oxidative degradation products already been reported, however, four novel degradation products are formed in acid hydrolysis which are not reported in the literature. Therefore, Using HPLC/PDA gradient program with waters X-bridge (250 mm × 4.6 mm, 5 µm) C18 column, the four acid hydrolysis degradants were identified and further characterized using UHPLC-IMS-QTOF-MS (ion mobility quadrupole time-of-flight m ass spectrometer) a nd N MR. T he s tructures o f D P-1, D P-2, D P-3 a nd D P-4 w ere further elucidated as hydroxy OSM Impurity, Des-acryl OSM impurity, Chloro OSM impurity and OSM dimer impurity, respectively. The structural characterization was followed by qualification of Impurities DP-1, DP-2, DP-3 and DP-4 using several different in-silico methodologies. From the results obtained, it can be concluded that no new structural alerts have been generated for DP-1 and DP-4 relative to the parent compound OSM. However, the degradation products, DP-2 and DP-3 shows structural alert positive for genotoxicity, which were both potential genotoxic substances. The current study presents separation, isolation, characterization and in-silico toxicity study for major acid degradants of OSM. The OSM generates DP-1 around 3.1%, DP-2 around 14.1%, DP-3 around 18.3% and DP-4 around 2.8% under acid hydrolysis on HPLC. The stress study was carried out in order to properly define the quality specifications for OSM drug products. [ABSTRACT FROM AUTHOR]

Data-independent acquisition (DIA) is an emerging technology for large-scale proteomic studies. DIA data analysis methods are evolving rapidly, and deep learning has cut a conspicuous figure in this field. This review discusses and provides an overview of the deep learning methods that are used for DIA data analysis, including spectral library prediction, feature scoring, and statistical control in peptide-centric analysis, as well as de novo peptide sequencing. Literature searches were performed for articles, including preprints, up to December 2021 from PubMed, Scopus, and Web of Science databases. While spectral library prediction has broken through the limitation on proteome coverage of experimental libraries, the statistical burden due to the large query space is the remaining challenge of utilizing proteome-wide predicted libraries. Analysis of post-translational modifications is another promising direction of deep learning-based DIA methods. [ABSTRACT FROM AUTHOR]

1. Challenges and opportunities in the field of biotransformation were presented and discussed at the 1st European Biotransformation workshop which was conducted virtually in collaboration with the DMDG 27 January 2021. Here we summarize the presentations and discussions from this workshop. The following topics were covered: 2. Needs for radiolabel for IND filing versus quantitation without standards. 3. Applications of cyclic ion mobility in the field of biotransformation. 4. Computational predictions of xenobiotic metabolism. 5. Future (outsourcing) needs in biotransformation. 6. Genotoxicity risk assessment of metabolites and qualification of impurities using metabolite data. 7. Regulatory aspects of MIST. [ABSTRACT FROM AUTHOR]

In this work, we report the electrical and dielectric behaviours of a ferroelectric nanoparticle-doped liquid crystal cell using the impedance and dielectric spectroscopic measurements in the frequency range 1 Hz – 2 MHz. The impact suitable equivalent electric circuit is proposed and the circuit parameters are obtained using the impedance spectroscopy technique. The impact of the nanoparticles on these parameters which attributed to mobile charge carriers accumulating near the electrodes of the cell is demonstrated and discussed. The presence of nanoparticles is found to increase the dielectric anisotropy (Δε) with maintaining a low loss tangent. As a result, a highly Δε = 120 for frequencies <100 Hz and Δε = 27 for f > 100 Hz is achieved. The dielectric measurements show that the presence of the nanoparticles leads to the appearance of low-frequency relaxation (f ≈ 500 Hz) due to the interfacial polarisation, a slight increase in the diffusion coefficient and the ion mobility. This work provides a foundation to quantitatively investigate the interface effect in dielectric composites. [ABSTRACT FROM AUTHOR]

A low-cost differential mobility spectrometer (DMS) was constructed using polytetrafluoroethylene printed circuit boards with two pairs of gold electrodes. The printed circuit boards were used to construct the drift tube into which the gas samples are introduced by a carrier gas and ionized. The ionized gas moves toward the gold electrode to which an asymmetric voltage is applied. Only the ionized gas with the proper ion mobility leaves the electrode region and reach the detection electrodes to form the ion current. Traces of five chemical warfare agents, including dimethyl methylphosphonate, triethylamine, 2-diisopropylaminoethanol, diethylaminoethanol, and N, N-dimethylethanolamine, were prepared using the permeation tube method and introduced into the sensor. All of the chemicals show characteristic ion peak shifts in the electric field. The limits of detection for the analytes are less than 1 ng/L. The recovery time was less than 10 s and the response time is 2 s. The developed sensor exhibits the ability to detect and distinguish between these chemical warfare agents. [ABSTRACT FROM AUTHOR]

The temperature dependence of the electrical conductivity of four samples of LiNbO3 crystals, which are significantly different in their electrical properties, is analyzed. It is shown that the corresponding experimental data can be correctly described within the framework of the simultaneous presence of mobile carriers with activation energies of 0.29 eV, 1.03 eV, and 1.33 eV, which correspond to polaron, proton, and lithium conductivity, respectively. [ABSTRACT FROM AUTHOR]

The metabolism and pharmacokinetics of gefitinib (Iressa®, N-(3-chloro-4-fluorophenyl)-7-methoxy-6-(3-morpholino-propoxy)quinazolin-4-amine), a selective thymidylate kinase inhibitor for the epidermal growth factor receptor (EGFR), was studied after IV and PO administration to male C57BL6 mice at 10 and 50 mg/kg respectively. The pharmacokinetics and metabolism of gefitinib were investigated using a range of rapid UHPLC-MS and UHPLC-IM-HRMS methods, using both reversed-phase (RP) and hydrophilic interaction liquid chromatography (HILIC), to rapidly determine the drugs pharmacokinetics and metabolic fate. Rapid oral absorption resulted in peak plasma concentrations at 1 h of ca. 7 µg/mL, that declined with a half-life of 3.8 h (2.6 h for the IV route), and providing an estimated oral bioavailability of 53%. Gefitinib itself was the major circulating drug-related compound in plasma extracts, with a total of 11 metabolites identified. The urinary profiles determined using both HILIC and RP-UPLC-IM-MS detected gefitinib and 10 metabolites or 15 metabolites respectively including the detection of a number of novel glucuronide conjugates. Despite rapid, sub 5 min, LC profiling methods being employed metabolite coverage was shown to be high and compared well with that of previous studies. [ABSTRACT FROM AUTHOR]

Although the Li-ion batteries have some advantages, they have some disadvantages such as high cost, short life, and safety issues. Recently, Ca-ion batteries (CIB) have been suggested to replace Li-ion batteries due to calcium wide availability, multivalent character, and nontoxicity. Now, we evaluated the potential application of graphyne and its BN analogous (BN-yne) in the CIBs with the use of the B3LYP-gCP-D3 approach. The adsorption of Ca2+ and Ca on the graphyne is stronger and weaker than those on the BN-yne, respectively. The highest energy barrier for Ca2+ migration on the BN-yne (4.3 kcal/mol) is much lesser than that on the graphyne (5.9 kcal/mol) because of a strong cation-lone pair interaction in the BN-yne compared to the weak cation-π interaction of graphyne. Therefore, we realise the potential of the BN-yne in providing a greater Ca ion mobility and a more rapid charge/discharge rate compared to graphyne. Diffusion coefficient values calculated for the Ca2+ on the surface of graphyne and BN-yne are 3.27 × 10−11 and 5.14 × 10−9 cm2/s, and the predicted cell voltages are 3.38 and 3.66 eV, respectively. The results suggest that the BN-yne sheet may be a superior anode candidate for CIBs compared to the graphyne. [ABSTRACT FROM AUTHOR]

The continuous technical improvement in sensitivity and specificity placed mass spectrometry as an alternative method for analyzing clinical samples. In parallel to the rapid development of discovery proteomics, targeted acquisition has been implemented as a complementary option for measuring a small set of proteins with high sensitivity and robustness in a large sample cohort. The combination of trapped ion mobility with a rapid time-of-flight (TOF) mass spectrometer improves the sensitivity even further and triggers the development of prm-PASEF. This article discusses the development of prm-PASEF and its advantages over the existing targeted and discovery methods for analyzing clinical samples. We are also highlighting the different requirements for the use of prm-PASEF on clinical samples. prm-PASEF takes advantage of a dual ion-mobility trap enabling highly multiplexed targeted acquisition. It allows the implementation of a short chromatographic separation setup without sacrificing the number of targeted peptides. Analyzing clinical samples by prm-PASEF holds the promise to significantly improve throughput while maintaining sensitivity to detect the selected target proteins. [ABSTRACT FROM AUTHOR]

We report molecular dynamics simulations of multiple radiation damage cascades in the pyrochlores Gd2Ti2O7 and Gd2Zr2O7 and the solid solution Gd2(ZrxTi1–x)2O7 (x = 0.25, 0.50, 0.75). Using a simulation cell of 360,448 atoms, for each compound 2200 decay events are simulated over a total time of 10 ns, with each recoiling uranium atom (primary-knock-on atom) assigned initial kinetic energy of 5 keV. The structures generated are analysed using Steinhardt local order parameters. There is a large increase in volume for the Ti pyrochlore associated with a transition to an amorphous structure which resembles the melt while preserving the local environment of the Ti. The calculated dose for amorphisation is 20 eV atom−1 which compares well with experiment overlap of cascade and damage accumulation drives the amorphisation suppressessing the healing mechanisms. The behaviour of the zirconate is different – the substantial anion disorder produced by each recoil event is followed by healing and reversion to the parent pyrochlore. In the solid solution the onset of amorphisation is delayed to later times on increasing the Zr concentration and overall swelling reduced. Our simulations highlight the importance of ion mobility, associated with the weaker Zr–O bonds, in healing. [ABSTRACT FROM AUTHOR]

An experimental configuration for velocity map ion imaging experiments is presented, in which a pulsed voltage defocusses the ion Newton sphere along the time-of-flight axis. This significantly spreads the times-of-flight for ions with the same mass-to-charge ratio, allowing for either sliced or three-dimensional velocity imaging with high slicing resolution along the time-of-flight axis. The technique is coupled to an event-triggered, position-sensitive sensor, enabling full three-dimensional Newton sphere imaging at high count rates, with significantly improved slicing resolution (∼1–2%) compared to previous DC slicing approaches. Good slice imaging conditions can be brought about at relatively high extraction voltages, circumventing issues regarding image size, stray fields, and poor detection efficiency when operating at low extraction voltages. The method, termed Post Extraction Inversion Slice Imaging (PEISI) was optimised through ion trajectory simulations and experimentally verified on the well-studied photodissociation of OCS at around 230 nm. We demonstrate that this approach is suitable for recording full 3D angular distributions of systems lacking an axis of cylindrical symmetry in the detector plane, where conventional image inversion techniques are invalid. This method could be useful in a range of systems lacking cylindrical symmetry, including studies into angular momentum polarisation and bimolecular scattering. [ABSTRACT FROM AUTHOR]

Two-photon dissociation dynamics of carbon disulfide (CS2) have been studied by using the time-sliced velocity map ion imaging technique. Images of the S (1D2) and S (3P0) photoproducts formed in the CS2 photodissociation are acquired at four photolysis wavelengths from 303 nm to 315 nm. Vibrational states of the CS co-products are partially resolved and identified in the images. The CS (X1Σ+) products are highly vibrationally excited with moderate rotational excitation. The spin–orbit state-specific dissociation dynamics are also investigated by measuring the images of three S (3PJ) spin–orbit states (J=0, 1, and 2) at photolysis wavelength 303.878 nm. The branching ratios of CS (a3Φ)/CS (X1Σg+) are determined to be 0.05 ± 0.02, 0.17 ± 0.04, and 0.26 ± 0.05 for the three spin–orbit states S (3P0), S (3P1), and S (3P2) respectively, implying a strong spin–orbit coupling exists in the dissociation process. The averaged anisotropy parameters β2>0 and β4∼0 suggest that the CS2 molecules undergo a sequential transition 21B2(21Σ+)←11B2(1Δu)←X1Σg+ with the intermediate state 11B2 having a long lifetime, followed by nonadiabatic and spin–orbit couplings to other electronic states and then dissociate. [ABSTRACT FROM AUTHOR]

This article focuses on the mean charge per particle of monodisperse submicron aerosols charged by the diffusion of unipolar ions in post-corona discharge. It aims to confirm and discuss the limits of considering a single value of Ni·t to describe aerosol charging and then to present methods to control the size-charge relation. Three aerosol chargers with different mixings of ion and aerosol flows are investigated. Despite comparable ion sources with discharge currents of a few tens of µA, the size-charge relations differ from one charger to another due to different ion-aerosol mixing conditions and subsequent differences in ion density along the particles' trajectories. Discrepancies are even more noticeable as the particle size increases. Discharge current, velocities of ion and aerosol flows and the electric field control post-discharge ion density at each point of the charging zone. The control of particle trajectory in expanding unipolar ion clouds leads to tuneable size-charge relations. Aerosol inertia and charging dynamics both depend on particle size, affect the Ni·t experienced by the particle and thus the final charge of the particle. Operating conditions to reach a constant mean charge for particles larger than 200 nm are reported. Conclusions provide a basis to design aerosol chargers devoted to electric mobility selection for aerosol deposition, separation or electrical measurements, especially to overcome the limits of mobility-to-size data inversion due to the multiple charge ambiguity inherent to diffusion chargers. Copyright © 2020 American Association for Aerosol Research [ABSTRACT FROM AUTHOR]

Modification of the traditional unipolar charging theory by consideration of the adsorption-desorption of ions on the particle surface is considered in the whole range of the Knudsen number. It is shown that the absorbing boundary conditions at the particle surface for the ion drift-diffusion problem, assumed in the traditional approach, becomes invalid at a late stage of the unipolar charging process, resulting in particle charge saturation. For the bipolar charging problem, the same modification of the theory in the hydrodynamic (continuum) regime is applied to a relatively low ion pairs concentration in the gas phase, typical for the air atmosphere with natural ionization sources, resulting in the attainment of complete equilibrium in the system with the saturated particle charge and zero ion fluxes. Copyright © 2020 American Association for Aerosol Research [ABSTRACT FROM AUTHOR]

While existing ion mobility calculators are capable of feats as impressive as calculating collision cross sections (CCS) within a few per cent and within a very reasonable time, the simplifications assumed in their estimations precludes them from being more precise, potentially overreaching with respect to the interpretation of existing calculations. With ion mobility instrumentation progressively reaching resolutions of several hundreds to thousands (accuracy in the range of ∼0.1%), a more accurate theoretical description of gas-phase ion mobility becomes necessary to correctly interpret experimental state-of-the-art separations. This manuscript entails an effort to consolidate the most relevant theoretical work pertaining to ion mobility within the 'free molecular' regime, describing in detail the rationale for approximations up to the two-temperature theory, using both a momentum transfer approach as well as the solution to the moments of the Boltzmann equation for the ion. With knowledge of the existing deficiencies in the numerical methods, the manuscript provides a series of necessary additions in order to better simulate some of the separations observed experimentally due to second-order effects, namely, high field effects, dipole alignment, angular velocities and moments of inertia, potential interactions and inelastic collisions among others. [ABSTRACT FROM AUTHOR]

A parallel plate differential mobility analyzer (DMA) having 100 independent current collectors is calibrated to relate the axial distances Ln between the inlet slit and the detector position to the particle mobility Z at given voltage difference V and sheath gas flow rate Q. Calibrating species are tetraheptylammonium bromide clusters (THABr) and polyethylene glycol (PEG35k, 5 nm in diameter), generated by a bipolar electrospray source, and purified in a cylindrical DMA. Gaussian fitting of the raw discrete mobility spectra in the form of ion current In versus collector position Ln, In(Ln), yield the mean value Lo of the collector position maximizing the signal for a given ion. The many (Z,V,Lo) triads obtained at given Q from many different DMA voltages and standard mobilities collapse into a single 1/(ZiVj) vs Lo curve when slight adjustments are made to the Zi. For different flow rates, Q/(ZiVj) vs. Lo curves collapse also, as long as the peaks are moderately narrow. However, for sufficiently small Q/Z, the THABr cluster peaks become broad, and the curves Q/(ZiVj) vs. Lo cease to collapse precisely. In contrast, the data for PEG show that this behavior is not a low-Q (Reynolds number) effect from the growth of the two lateral boundary layers, but is rather due to the broad and non-Gaussian peak shapes obtained at low Q or high Z. The calibration is accordingly unaffected by the Reynolds number. This simplicity was unexpected, given the three-dimensional flow in this DMA with growing lateral boundary layers. Copyright © 2020 American Association for Aerosol Research [ABSTRACT FROM AUTHOR]

The migration of cations, which leads to the transportation of water molecules, is the essential driving force of electrokinetic dewatering. Several bench-scale experiments on Hangzhou sludge were performed using ferrum, graphite, copper, and aluminum electrodes. The element contents of Na, K, Mg, Ca, Fe, Al, and Cu in the effluent water as well as in the treated soil were measured to investigate the migration process of the corresponding cations. The electrokinetic drainage was noted to have a higher total content of the considered elements compared to that in gravity drainage, which demonstrated that electrokinetic treatment is effective for bound water. In the electrokinetic drainage, the contents of Na and K were much higher than those of other elements. Furthermore, the steady contents of Na and K in the electrokinetic drainage demonstrated the consistent electrokinetic mobility of Na and K ions. Ca and Mg ions tended to precipitate in the cathodic area. Most of the Fe ions generated from the reaction at the anode remained in the anodic area. The extremely low Cu content in the drainage and soil meant that no variations could be observed. Different cations were noted to have different electrokinetic mobilities. Higher electrokinetic mobilities were observed for cations having lower valency or smaller atomic weights. The order of ion electrokinetic mobility was noted to be Na+ > K+ > Mg2+ > Ca2+ > Al3+ > Cu2+ > Fe2+/Fe3+. Therefore, electrokinetic dewatering depends primarily on the presence of cations having a low valency or small atomic weight such as Na, K, Ca, Mg, and Al ions. Fe and Cu ions have low electrokinetic mobility and do not contribute considerably to the transportation of water molecules. The study provided guidance in the application evaluation of the electrokinetic technique in drying various soils. [ABSTRACT FROM AUTHOR]

Deposition of aerosol nanoparticles using an electrostatic precipitator is widely used in the aerosol community. Despite this, basic knowledge regarding what governs the deposition has been missing. This concerns the prediction of the size of the particle collection zone, but also, perhaps more importantly, prediction of the nanoparticle concentration distribution on the substrate, both of which are necessary to achieve faster and more precise deposition. In this article, we have used COMSOL Multiphysics simulations, experimental depositions, and two analytical models to describe the deposition. Based on that, we propose a simple equation that can be used to predict the size of the deposition spot as well as the particle concentration on the substrate. The equation we derive concludes that the size of the deposition spot only depends on the gas flow rate into the precipitator, and on the constant drift velocity of a particle in an electric field. The equation also displays that the deposited particle concentration is independent of the gas flow rate. Our general mathematical analysis has great applicability, as it can be used to model different geometries and different types of deposition methods than the one described in this article. We can therefore also propose that the drift velocity in this model easily could be replaced by another velocity acting on the particles at other deposition conditions, for instance, the thermophoretic velocity during thermophoretic deposition. This would result in the same dependence as presented in this article. Finally, we demonstrate analytically and through experiment that the particle distribution inside the spot will be homogenous and follows a top hat profile. [ABSTRACT FROM AUTHOR]

An adverse electric field is often encountered or utilized when classifying charged nanoparticles or ions according to their electrical mobility. For instance, the classified charged particles usually have to be transported through an adverse electric field against the aerosol sample flow before exiting the outlet of a differential mobility analyzer (DMA). Recently, we reported the transmission of charged nanoparticles through the DMA adverse axial electric field and its improvements. Herein, the simplified analytical model used in that study and a new simplified numerical model to evaluate particle transmission efficiency through the adverse axial electric field are introduced in detail. In addition to the DMA sample outlet, these models are also tested for the electrical mobility filter (EMF) for segregating charged nanoparticles, especially under the unfavorable conditions when the assumptions for these models are violated. The modeled results are compared to a Monte Carlo method based on single-particle tracking and the experimentally determined transmission efficiencies. For the typical geometries and test conditions of a half-mini DMA sample outlet and the EMF, the mean absolute differences between these models and the Monte Carlo method are less than 1%. However, the accuracy of these models is guaranteed only when their assumptions are satisfied, i.e., when the adverse electric field is longer than 4 times the tube radius so that the field lines are axially parallel and the tube length before the adverse electric field is at least half of the entrance length for the air flow. In addition, the simplified analytical model may deviate from the true transmission efficiency when the adverse electric field is longer than 10% of the entire tube. In such cases that the assumptions for both the simplified analytical model and the simplified numerical model are violated, the Monte Carlo method can be used instead. Copyright © 2019 American Association for Aerosol Research [ABSTRACT FROM AUTHOR]

Retarding filed analyzers (RFAs) measure the ion velocity distribution in edge plasmas, leading to an estimate of the ion temperature and space potential through curve fitting. This paper describes the bi-directional RFA detector installed on the Experimental Advanced Superconducting Tokamak for edge plasma parameter measurements. The paper also describes a technique to compensate for a known induced noise using a dummy signal line and a method to reconstruct the I–V curve from the scanning voltage signal and the resultant ion current waveform. Fitting to experimental data and numerical simulations show that the I–V curve reconstruction method serves for both smoothing and induction noise compensation purposes. [ABSTRACT FROM AUTHOR]

We investigated the dynamic properties of alkali halide solutions (NaCl, NaF, NaBr, NaI, LiCl, and KCl) using molecular dynamics simulations and several non-polarisable, polarisable, and scaled-charge models. The concentration dependence of shear viscosity was obtained with low statistical uncertainties to allow for calculation of the viscosity Jones-Dole B-coefficients. No prior values are available for the B-coefficients from molecular simulations of fully atomistic models for electrolyte solutions. In addition, we obtained diffusion coefficients with rigorous finite-size corrections to access ion mobilities; these provide insights on single ion hydration behaviour. We find that all models studied, even polarisable and scaled-charge models, quantitatively over-predict water structuring but qualitatively follow the experimentally determined Hofmeister series. All ion models considered are kosmotropes based on their calculated B-coefficient and diffusion coefficients, even for ions experimentally found to be chaotropes. These observations indicate that the water-ion interactions in these models are not adequately represented; additional interactions such as charge transfer must be incorporated in future models in order to better represent electrolyte solution properties. [ABSTRACT FROM AUTHOR]

Removal of undesired substances from water is a field of investigation recently focused at the nanoscale. Towards this direction, molecular dynamics simulations are conducted in this paper to investigate unwanted ion removal in nanochannel flows. The simulation method incorporates a Poiseuille-like water/ion flow system at the nanoscale where an electric field, of various magnitudes in the range of E = 0.25–1.5 V/Å, is applied perpendicular to the flow, leading anions and cations close to the wall regions, similar to the Capacitive De-Ionization method. The time needed for ions to reach equilibrium, i.e. to flow in the region near the walls while pure water flows in the channel interior, is t = 1.3 ns when E = 1.5 V/Å and t = 4.0 ns when E = 0.25 V/Å, showing a dependency on the value of the electric field. Calculations on density, velocity, and temperature values report on fluid properties to be used in the proposed desalination configuration and could act as a basis to guide novel technological applications and extend to higher scales. [ABSTRACT FROM AUTHOR]

This paper is about the Gas Electron Multiplier (GEM), a gas detector that will be installed on the new Super BigBite Spectrometer (SBS), under construction at Jefferson Laboratory in Newport News, VA, USA; the main interest of JLAB physics is the study of the fundamental interactions and constituents of hadronic matter and in particular the study of the electromagnetic Form Factors of the nucleons. The Italian group, JLAB12, is engaged in the construction, characterization and commissioning of two of the detectors that will be implemented in SBS: the GEM front tracker and the hadron calorimeter HCAL-J. A Gas Electron Multiplier is a gas detector useful to track the charged particles. It is composed of 2 layers of copper and a layer of Kapton, a dielectric material; all the layers together are inside a box with a mixture of gas: 70 % of Argon an 30 % of CO 2 . In each GEM foil there are a lot of biconical holes, and it is placed between a drift plane and a readout plane; when a charge particle crosses the gas, it loses energy creating couple ion-electron. If we apply a potential difference, the pairs are accelerated by the electric field, and they have enough energy to create an avalanche. The gain that we can reach with a single GEM foil is 1000. In JLAB's configuration for SBS, a TripleGEMs system will be used; a TripleGEM is composed of 3 GEM foil placed in cascade. The advantages of this technology are: the layers structure, so the primary ionization, the multiplication and the charge collection regions are separated, the high gain about 100,000, the flexibility of geometry, the good spatial resolution about 70 µm, low costs and small streamer or charging up phenomena. To verify GEMs performances and to optimize the digitalization model, we started simulations changing some physical and geometric parameters. In order to run the GEM's simulations, we used two different software: ANSYS Mechanical APDL to create the detector geometry, assign the materials, define the meshes in shape and size and the electric field, and Garfield++, a toolkit for detailed Monte Carlo simulation of a gaseous detector, to evaluate the distribution of the charged particles on the readout plane when we change some parameters like the type of the primary particle, its energy and its incident slope. In particular, we built two different models: a triple GEM model and a cascade model; we are comparing the simulations results with the real test that we did in Juelich (Germany) with a beam of 2.8 GeV protons. [ABSTRACT FROM AUTHOR]

Flavonoids are a large class of dietary molecules, among which quercetin is the most ubiquitous, which undergo an extensive intestinal phase-II metabolism. We compared the in vivo metabolism of quercetin in healthy volunteers with two in vitro models, HT29 cells and 3 D human intestinal tissues. Supernatants of the in vitro experiments and the human intestinal fluids (HIF) were analyzed by LC-IMS-MS and LC-HRMS in a qualitative way. Quercetin glucuronides, sulfates and their methyl conjugates were detected in all three systems. The metabolic profiles were found to be different, both in terms of the metabolites produced and their relative proportions. In particular, quercetin sulfates were almost absent in supernatants from HT29 cells incubations while they were a major metabolite in HIF and also found in 3 D intestinal tissues incubations. IMS provided structural information as well as a third dimension of characterization, while HRMS brought increased sensitivity and MS/MS confirmation. HT29 cells are a useful tool to generate phase-II metabolites but do not represent the in vivo situation. 3 D intestinal tissues appear as a more relevant tool to study the intestinal phase-II metabolism of flavonoids. [ABSTRACT FROM AUTHOR]

A V-shaped ion funnel (IF) drift tube was developed for proton transfer reaction mass spectrometry (PTR-MS). The ion transmissions were characterized at variable radio frequency voltages and frequencies to obtain optimized conditions while considering the effects of radial-focusing, reaction rate, and collision-induced dissociation. The improvements in sensitivity for common compounds were experimentally obtained and ranges from 2 to 22 times depending on the analyte. The product ions distributions were also studied for V-shaped IF PTR-MS. Together with the literature reports for U-shaped IF PTR-MS, a valuable and comprehensive reference is provided for future optimization of IF PTR-MS and other mass spectrometers. [ABSTRACT FROM AUTHOR]

Finding inorganic materials with significant Al ion mobility could push the development of alternative rechargeable batteries, as they could potentially serve as solid electrolytes or intercalation cathodes. While for single‐ and double‐charged ions numerous solid electrolytes are known, the situation is rather unclear and only sparingly researched for ions with a charge higher than two. To assist in the systematic analysis, compounds described in literature as solid electrolytes or intercalation materials for Al3+, as well as some materials generally known for high mobilities for multivalent ions, are critically reviewed and analyzed by the bond‐valence energy landscape approach. For this purpose a thorough list of investigated cathode materials for rechargeable Al batteries is provided first. While it is demonstrated that solid electrolytes for Al3+ cannot be unequivocally identified in literature yet, the analysis of the intercalation cathodes reveals promising structural motifs for comparatively fast Al diffusion, which can be used for the analysis, comparison and design of new promising materials. Furthermore, chances and limits of the bond‐valence energy analysis for high‐valent battery materials are exemplarily shown. Thus, this work aims at encouraging more theoretical and experimental work on Al battery materials and provides guidelines for doing so. [ABSTRACT FROM AUTHOR]

Machine learning based mobile traffic classification has become a popular topic in recent years. As mobile traffic data is dynamic in nature, the static model has become ineffective for the task of classifying future traffic. This is known as the concept drift problem in data streams. To this end, this paper presents an adaptive mobile traffic classification method. Specifically, a method based on the fuzzy competence model is devised to detect concept drift, and a dynamic learning method is presented to update the classification model, so as to adapt to an ever-changing environment at an appropriate time. The concept drift detection method relies on the data distribution instead of the classification error rate. Furthermore, the weights of flow samples are dynamically updated and flow samples are resampled for training a new model when a concept drift is detected. Moreover, recently trained models are saved and used for classification in weighted voting. The weight of each model is updated according to the performance it obtains on the most recent flow samples. On mobile traffic data, experimental results show that our proposed method obtains lower classification error rate with less time consumption on updating models as compared to related methods designed for handling concept drift problems. [ABSTRACT FROM AUTHOR]

The laser ablation of boron-nitride (BN) ceramic was employed for the preparation of thin films in high vacuum and nanoparticles and nanocrystals generated in water. The obtained plasma was investigated using ion detectors to determine the ion velocity, the energy per charge state and the plasma temperature and describing the acceleration mechanism. The kinetics of laser ablation in water and the comparison of different ablation rates in the vacuum and in water, and the possible applications of the BN thin film and nanoparticles are presented and discussed. [ABSTRACT FROM AUTHOR]

Electrical mobility size spectrometers (with a neutralizer, an electrical mobility classifier, and a detector as key components) are widely used to measure aerosol size distributions. The performance of a neutralizer is often evaluated separately from the spectrometer. In real-world applications of a neutralizer, i.e., typically with uncontrolled composition of the neutralizer carrier gas including trace constituents that can lead to variabilities in properties of positive and negative ions, charge fractions may differ from those predicted by widely used aerosol charging models with fixed ion properties and subsequently cause significant uncertainties in reported aerosol size distributions. In this study, we proposed an empirical method to retrieve the variations in neutralizer ion properties and aerosol charge fractions when measuring aerosol size distributions. Our approach requires measuring both positively and negatively charged particles using the electrical mobility size spectrometer to provide information on the performance of the neutralizer. Bipolar diffusion charging theories were applied to illustrate that aerosol charge fractions are governed by the mobility ratio of positive and negative ions. Positively and negatively charged particles measured by the spectrometer can be used to estimate the mobility ratio of positive and negative ions for the neutralizer. A modified Gunn and Woessner’s formula can then be used to calculate aerosol charge fractions from the retrieved ion mobility ratio. These charge fractions can be used for size distribution data inversion. Both simulated aerosols and experiments were used to evaluate the proposed method. We found that this new method can capture the variations in neutralizer ion properties and aerosol charge fractions under various conditions and help to achieve more accurate measurement of aerosol size distributions. Copyright © 2018 American Association for Aerosol Research [ABSTRACT FROM AUTHOR]

The self-toughening property of calcium hexaluminate (CaO•6Al2O3, CA6) in engineering ceramics causes a remarkable interest in the in-situ CA6 in monolithic refractory. The determination of significant factors which controls the formation and microstructure of CA6 in monolithic refractory is mainly discussed in this study. Samples were prepared by using calcium aluminate cement and sintered alumina and the chemical composition was fixed at the molar ratio of CaO: Al2O3 = 1:6. In order to evaluate the suitable sintering condition and SiO2 content for CA6 phase formation, the variation of firing temperature and holding time was first modified at 1400-1500°C for 1-5 h. The second factor was done by adding 2-10 mass% of SiO2 into the primary mixture. In comparison, the results were confirmed that high firing temperature at 1500°C provided the highest quantity of CA6 phase and plate-like microstructure. In addition, longer proceeding time contributed to the grain growth of CA6, especially, within 5 h of holding time. SiO2 importantly helped to enhance hexagonal platelike microstructure due to the ability of ion mobility in low-melting phase of gehlenite but the suitable content of SiO2 should not exceed 2 mass% for the better control ability of CA6 formation and microstructure. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulations were carried out to model aqueous solution with different concentration of α,α-trehalose, one kind of non-reducing sugars possessing outstanding freeze-drying protective effect on biological system. The dihedral angles of the intraglycosidic linkage in trehalose were measured to estimate its structure rigidity. The dynamics and hydrogen bonding properties were studied by calculating the self-diffusion coefficient of trehalose and the distributions and lifetimes of various types of H-bonds in the solution. Through analysing the results as well as comparison with another common sugar sucrose, the freeze-drying protective mechanism of trehalose was explained at molecule level. First, trehalose is able to maintain the local structure around it as a frame due to its relatively rigid conformation. Second, the addition of trehalose restrains the water molecules from rearrangement as a result of low mobility, thus reduces the probability of freezing; trehalose has lower diffusion coefficient than water and bigger thermal diffusivity, which are favourable for vitrification. Third, the formation of H-bonds between trehalose and water and between trehalose molecules is the essence of the protective effect. Trehalose does not work via strengthening the H-bonds formed between water molecules (W–W H-bonds), instead of which it breaks the potential tetrahedral pattern of W–W H-bonds, thus suppresses the tendency of ice formation. It was also found that trehalose realises protective action better at higher concentration as far as this study is concerned. [ABSTRACT FROM PUBLISHER]

Results of a study of electronic energy loss of low keV protons interacting with multilayer graphene targets are presented. Proton energy loss shows an unexpectedly high value as compared with measurements in amorphous carbon and carbon nanotubes. Furthermore, we observe a classical linear behavior of the energy loss with the ion velocity but with an apparent velocity threshold around 0.1 a.u., which is not observed in other carbon allotropes. This suggests low dimensionality effects which can be due to the extraordinary graphene properties. [ABSTRACT FROM AUTHOR]

The inference of particle size distributions from differential mobility analyzer (DMA) data requires knowledge of the charge distribution on the particles being measured. The charge distribution produced by a bipolar aerosol charger depends on the properties of the ions produced in the charger, and on the kinetics of charge transfer from molecular ions or ion clusters to the particles. A single parameterization of a theoretically predicted charge distribution is employed in most DMA analyses regardless of the atmospheric conditions being probed. Deviations of the actual charge distribution from that assumed in the data analysis will bias the estimated particle size distribution. We examine these potential biases by modeling measurements and data inversion using charge distributions calculated for a range of atmospheric conditions. Moreover, simulations were performed using the ion-to-particle flux coefficients predicted for a range of properties of both the particles and ions. To probe the biases over the full range of particle sizes, the measurements were simulated through an atmospheric new particle formation event. The differences between the actual charge distribution and that according to the commonly used parametrization resulted in biases as large as a factor of 5 for nucleation-mode particles, and up to 80% for larger particles. Incorrect estimates of the relative permittivity of the particles or not accounting for the temperature and pressure effects for measurements at 10 km altitude produced biases in excess of 50%; threefold biases result from erroneous estimates of the ion mobility distribution. We further report on the effects of the relative permittivity of the ions, the relative concentrations of negative and positive ions, and truncation of the number of charge states considered in the inversion. [ABSTRACT FROM AUTHOR]

A water-based condensational growth channel was developed for imaging mobility-separated particles within a parallel plate separation channel of the Fast Integrated Mobility Spectrometer (FIMS). Reported are initial tests of that system, in which the alcohol condenser of the FIMS was replaced by a water-based condensational growth channel. Tests with monodispersed sodium chloride aerosol verify that the water-condensational growth maintained the laminar flow, while providing sufficient growth for particle imaging. Particle positions mapped onto particle mobility, in accordance with theoretical expectations. Particles ranging in size from 12 nm to 100 nm were counted with the same efficiency as with a butanol-based ultrafine particle counter, once inlet and line losses were taken into account. [ABSTRACT FROM AUTHOR]