A new setup for measurements of absolute saturation vapor pressures using a dynamical method: Experimental concept and validation.

We describe a new experimental system for direct measurements of the absolute saturation vapor pressures of liquid or solid samples. The setup allows the isolation of the sample under steady conditions in an ultra-high vacuum chamber, where the measurement of the sample's vapor pressure as a function of its temperature can be performed in a range around room temperature and in a pressure range defined only by the applied absolute pressure sensor. We characterize the setup and illustrate its capability to measure saturation vapor pressures as well as enthalpies of evaporation around room temperature with explicit measurements on four liquid compounds (diethyl phthalate, 1-decanol, 1-heptanol, and 1-hexanol) for which accurate vapor pressures have previously been reported.

Psychoeducational group interventions for adults diagnosed with attention-deficit/ hyperactivity disorder: a scoping review of feasibility, acceptability, and outcome measures.

INTRODUCTION: Although psychoeducational group interventions are increasingly used for adults diagnosed with attention-deficit/hyperactivity disorder (ADHD), a comprehensive review focused on the feasibility and acceptability indicators of these interventions remains lacking. Furthermore, although previous research has explored various aspects of psychoeducation for ADHD, such as its definition and approaches, limited research has focused on the synthesis for outcome measures and patients' experiences related to these interventions. Therefore, this scoping review aims to map the existing evidence reported on psychoeducational group interventions for adults diagnosed with ADHD. The objective is to provide a comprehensive overview of feasibility indicators, acceptability, and outcome measures used in psychoeducational group interventions. METHOD: A comprehensive structured literature search on the topic was performed in seven bibliographic databases, and the resulting records were independently screened, and their data extracted by two reviewers. We followed the Preferred Reporting Items for Systematic reviews and Meta-Analyses Extension for Scoping Reviews (PRISMA-S) to ensure the transparency and rigor of this scoping review. RESULTS: The searches yielded 7510 records. Eight studies met the inclusion criteria. These included studies were conducted in European countries and the United States. Among these, six studies used a randomized control design, one an open feasibility trial, and one a pre-post intervention design. All the studies reported some feasibility and acceptability indicators. While all the studies reported on the severity of symptoms of ADHD as an outcome measure, some also reported on outcomes related to psychological or mental-health problems, quality of life, changes in knowledge regarding ADHD, or the level of self-esteem, functioning, and impairment. CONCLUSION: This scoping review revealed that psychoeducational group interventions are generally acceptable for patients in terms of patient satisfaction with the group intervention. All included studies reported some feasibility indicators, with some reporting good attendance and relatively low dropout rates. Most studies reported positive effects on ADHD and mental health symptoms, suggesting that these interventions are beneficial for adults with ADHD. However, several gaps exist regarding the reporting on the feasibility indicators, acceptability, and outcome measures employed across studies.

On the origin of epitaxial rhombohedral-B4C growth by CVD on 4H-SiC.

Rhombohedral boron carbide, often referred to as r-B4C, is a potential material for applications in optoelectronic and thermoelectric devices. From fundamental thin film growth and characterization, we investigate the film-substrate interface between the r-B4C films grown on 4H-SiC (0001̄) (C-face) and 4H-SiC (0001) (Si-face) during chemical vapor deposition (CVD) to find the origin for epitaxial growth solely observed on the C-face. We used high-resolution (scanning) transmission electron microscopy and electron energy loss spectroscopy to show that there is no surface roughness or additional carbon-based interlayer formation for either substrate. Based on Raman spectroscopy analysis, we also argue that carbon accumulation on the surface hinders the growth of continued epitaxial r-B4C in CVD.

Nanomolecularly-induced Effects at Titania/Organo-Diphosphonate Interfaces for Stable Hybrid Multilayers with Emergent Properties.

Nanoscale hybrid inorganic-organic multilayers are attractive for accessing emergent phenomena and properties through superposition of nanomolecularly-induced interface effects for diverse applications. Here, we demonstrate the effects of interfacial molecular nanolayers (MNLs) of organo-diphosphonates on the growth and stability of titania nanolayers during the synthesis of titania/MNL multilayers by sequential atomic layer deposition and single-cycle molecular layer deposition. Interfacial organo-diphosphonate MNLs result in ∼20-40% slower growth of amorphous titania nanolayers and inhibit anatase nanocrystal formation from them when compared to amorphous titania grown without MNLs. Both these effects are more pronounced in multilayers with aliphatic backbone-MNLs and likely related to impurity incorporation and incomplete reduction of the titania precursor indicated by our spectroscopic analyses. In contrast, both MNLs result in two-fold higher titania nanolayer roughness, suggesting that roughening is primarily due to MNL bonding chemistry. Such MNL-induced effects on inorganic nanolayer growth rate, roughening, and stability are germane to realizing high-interface-fraction hybrid nanolaminate multilayers.

A Walk on the Wild Side: Genome Editing of Tuber-Bearing Solanum bulbocastanum.

Solanum bulbocastanum is a wild diploid tuber-bearing plant. We here demonstrate transgene-free genome editing of S. bulbocastanum protoplasts and regeneration of gene-edited plants. We use ribonucleoproteins, consisting of Cas9 and sgRNA, assembled in vitro, to target a gene belonging to the nitrate and peptide transporter family. Four different sgRNAs were designed and we observed efficiency in gene-editing in the protoplast pool between 8.5% and 12.4%. Twenty-one plants were re-generated from microcalli developed from individual protoplasts. In three of the plants we found that the target gene had been edited. Two of the edited plants had deletion mutations introduced into both alleles, whereas one only had a mutation in one of the alleles. Our work demonstrates that protocols for the transformation of Solanum tuberosum can be optimized to be applied to a wild Solanum species.

Optimized barley phytase gene expression by focused FIND-IT screening for mutations in cis-acting regulatory elements.

Introduction: Induced modification of plant gene expression is of both fundamental and applied importance. Cis-acting regulatory elements (CREs) are major determinants of the spatiotemporal strength of gene expression. Yet, there are few examples where induced genetic variation in predetermined CREs has been exploited to improve or investigate crop plants. Methods: The digital PCR based FIND-IT technology was applied to discover barley mutants with CRE variants in the promoter of the nutritional important barley grain phytase (PAPhy_a) gene. Results and discussion: Mutants with higher or lower gene expression and ultimately higher or lower mature grain phytase activity (MGPA), respectively, were discovered. Field trials and inositol phosphate profiling during germination showed that PAPhy_a does not influence agronomic performance under the trial conditions but it does shorten the lag time of phosphate mobilization during germination. Higher endogenous MGPA is an improvement of grain quality for feed use as it improves the phosphate bioavailability for monogastric animals. Moreover, as the targeted CRE motifs of the PAPhy_a promoter are shared with a range of seed expressed genes like key cereal and legume storage genes, the current results demonstrates a concept for modulating individual gene expression levels of a range of seed genes.

High fat diet is associated with gut microbiota dysbiosis and decreased gut microbial derived metabolites related to metabolic health in young Göttingen Minipigs.

The objectives were 1) to characterize a Göttingen Minipig model of metabolic syndrome regarding its colon microbiota and circulating microbial products, and 2) to assess whether ovariectomized female and castrated male minipigs show similar phenotypes. Twenty-four nine-week-old Göttingen Minipigs were allocated to four groups based on sex and diet: ovariectomized females and castrated males fed either chow or high-fat diet (HFD) for 12 weeks. At study end, body composition and plasma biomarkers were measured, and a mixed meal tolerance test (MMT) and an intravenous glucose tolerance test (IVGTT) were performed. The HFD groups had significantly higher weight gain, fat percentage, fasting plasma insulin and glucagon compared to the chow groups. Homeostatic model assessment of insulin resistance index (HOMA-IR) was increased and glucose effectiveness derived from the IVGTT and Matsuda´s insulin sensitivity index from the MMT were decreased in the HFD groups. The HFD groups displayed dyslipidemia, with significantly increased total-, LDL- and HDL-cholesterol, and decreased HDL/non-HDL cholesterol ratio. The colon microbiota of HFD minipigs clearly differed from the lean controls (GuniFrac distance matrix). The main bacteria families driving this separation were Clostridiaceae, Fibrobacteraceae, Flavobacteriaceae and Porphyromonadaceae. Moreover, the species richness was significantly decreased by HFD. In addition, HFD decreased the circulating level of short chain fatty acids and beneficial microbial metabolites hippuric acid, xanthine and trigonelline, while increasing the level of branched chain amino acids. Six and nine metabolically relevant genes were differentially expressed between chow-fed and HFD-fed animals in liver and omental adipose tissue, respectively. The HFD-fed pigs presented with metabolic syndrome, gut microbial dysbiosis and a marked decrease in healthy gut microbial products and thus displayed marked parallels to human obesity and insulin resistance. HFD-fed Göttingen Minipig therefore represents a relevant animal model for studying host-microbiota interactions. No significant differences between the castrated and ovariectomized minipigs were observed.

Incidence and sequence of scoliosis and windswept hip deformity: which comes first in 4148 children with cerebral palsy? A longitudinal cohort study.

BACKGROUND: The aim was to analyse whether scoliosis or windswept hip deformity (WSH) occurs first for children with cerebral palsy (CP). METHODS: This longitudinal cohort study using data from 1994 - 2020 (26 years) involved 41,600 measurements of 4148 children (2419 [58.3%] boys) with CP born 1990 - 2018 and registered into the Swedish CP follow-up program. Children were followed from a mean age of 2.8 [SD 1.4] years, until they developed either scoliosis or WSH or were removed at surgery. RESULTS: WSH developed first in 16.6% of the children (mean age 8.1 [SD 5.0] years), and scoliosis in 8.1% (mean age 8.1 [SD 4.9] years). The incidence of WSH was higher than scoliosis across all levels I-V of the Gross Motor Function Classification System (GMFCS), both sexes, and for those with dyskinetic (20.0%) or spastic (17.0%) CP. The incidence of scoliosis was highest (19.8%) and developed earliest in children with GMFCS level V (mean age 5.5 [SD 3.5] years), and in children with dyskinetic (17.9%) CP (mean age 7.0 [SD 4.7] years). CONCLUSIONS: WSH presents earlier than scoliosis in most children with CP. Children with higher GMFCS level or dyskinetic CP are more likely to develop these deformities at a younger age.

A comparison of the original major depression inventory with a modified version: A Danish validation study.

BACKGROUND: The Major Depression Inventory (MDI) is a patient-reported outcome measure used by general practitioners to assist with diagnosing and evaluation of the severity of a patient's depression. However, recent studies have questioned the structural validity of the MDI. OBJECTIVES: We proposed a modified version (mMDI) of the MDI with fewer response categories and four rephrased items and aimed to compare the psychometric properties of the changes in a joint cohort of patients from general practice and mental health associations. METHODS: We used Rasch analysis, confirmatory factor analysis, and the area under the receiver operating curve (AUROC) to assess the validity and reliability of the two versions. Equipercentile linking was used to compute cut-off points for the mMDI. RESULTS: For both versions, local dependence was found between the three item pairs (loss of interest, lack of energy), (lack of self-confidence, feelings of guilt), and (concentration problems, feeling restless/slowed down). The mMDI displayed lower measurement error in the upper end of the scale and better item level fit for three of the four reformulated items compared to the MDI. For the MDI, 5.3% of the respondents gave improbable responses; the corresponding number was 3.4% for the mMDI. The mMDI displayed better fit to a one-factor model compared to the MDI. When comparing the correlation of the scales with the WHO-5 instrument, the corresponding AUROC estimates for the mMDI and MDI were found to be 0.93 (0.92; 0.96) and 0.91 (0.87; 0.94), respectively. The cut-off points for mild, moderate, and severe depression in the mMDI were found to be 17, 20, and 23, respectively. CONCLUSION: The proposed changes of the MDI are psychometrically sound upgrades of the original.

Psychoeducation for adult ADHD: a scoping review about characteristics, patient involvement, and content.

BACKGROUND: Psychosocial interventions such as psychoeducation are increasingly being used to treat adult ADHD, both as an alternative and as a supplement to pharmacotherapy. A thorough overview of the literature on psychoeducation for adult ADHD is lacking. The objectives of this scoping review were therefore to identify the characteristics of psychoeducation interventions designed for adults with ADHD, examine how the patient experience or perspective is considered during the intervention's development and implementation, determine the typical themes covered, and explore how 'psychoeducation' is defined in these interventions. METHODS: A comprehensive search was performed to identify records in MEDLINE, Embase, PsycINFO, Web of Science, Cochrane CENTRAL, AMED, and ClinicalTrials.gov. Two or more reviewers were included in every step of the screening process and the final selection of included studies. The Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) checklist (Supplementary Material 1) was used to report the results, and the framework developed by Arksey and O'Malley was used as a guide throughout the scoping process. RESULTS: A total of 2121 records were identified through the literature search. After screening and full-text analysis, ten studies were included for final analysis. Most studies were conducted in Europe and followed a group format. Seven main themes were identified: Information about the diagnosis, treatment options, somatic health and ADHD, the insider perspective, ADHD and social life, coping and psychological skills, and ADHD and work. There was significant overlap in themes covered, but coverage of each theme varied. Themes deemed important by newer research, such as sexuality and gender-specific issues, were missing. Only one intervention involved patients in its development and implementation, and two interventions involved family members. There was variation in how psychoeducation was defined in the included studies, and the implications of this are discussed. CONCLUSION: The literature on psychoeducation for adult ADHD is not ready for any systematic effect estimation. Before such estimations are conducted, a shared understanding and definition of psychoeducation are needed. The involvement of end users in the development and delivery of interventions may aid reach this goal but results from this review indicate that such practices are rare.

Gas-to-Particle Partitioning of Products from Ozonolysis of Δ3-Carene and the Effect of Temperature and Relative Humidity.

Formation of oxidized products from Δ3-carene (C10H16) ozonolysis and their gas-to-particle partitioning at three temperatures (0, 10, and 20 °C) under dry conditions (<2% RH) and also at 10 °C under humid (78% RH) conditions were studied using a time-of-flight chemical ionization mass spectrometer (ToF-CIMS) combined with a filter inlet for gases and aerosols (FIGAERO). The Δ3-carene ozonolysis products detected by the FIGAERO-ToF-CIMS were dominated by semivolatile organic compounds (SVOCs). The main effect of increasing temperature or RH on the product distribution was an increase in fragmentation of monomer compounds (from C10 to C7 compounds), potentially via alkoxy scission losing a C3 group. The equilibrium partitioning coefficient estimated according to equilibrium partitioning theory shows that the measured SVOC products distribute more into the SOA phase as the temperature decreases from 20 to 10 and 0 °C and for most products as the RH increases from <2 to 78%. The temperature dependency of the saturation vapor pressure (above an assumed liquid state), derived from the partitioning method, also allows for a direct way to obtain enthalpy of vaporization for the detected species without accessibility of authentic standards of the pure substances. This method can provide physical properties, beneficial for, e.g., atmospheric modeling, of complex multifunctional oxidation products.

Workload and GP burnout: a survey and register-based study in Danish general practice.

BACKGROUND: Burnout is common among GPs. Previous studies have indicated an association between high workload and burnout among doctors. AIM: To assess the risk of burnout among single-handed GPs in Denmark in relation to self-reported and register-based workload. DESIGN & SETTING: Questionnaire data from 312 Danish single-handed GPs and register data on their patients and provided services. METHOD: Burnout was measured using the Maslach Burnout Inventory-Human Services Survey (MBI-HSS). A composite burnout score of quartile points was calculated. The questionnaire provided information on working hours. Register data included number of services and patient list size. Association between composite burnout score and workload was estimated with binomial regression analyses adjusting for the GP's age and sex, and social deprivation score of their patient lists. RESULTS: Working >5 days a week in practice increased the risk of a high burnout score (adjusted risk ratio [RR] = 2.34, 95% confidence interval [CI] = 1.62 to 3.37). Spending >7.5 hours a day on patient-related tasks increased the risk of a high burnout score. The highest score was among GPs spending 8.5-9.5 hours a day on patient-related tasks (adjusted RR = 2.01, 95% CI = 0.90 to 4.51), although not statistically significant. There was no association between number of services and risk of burnout. CONCLUSION: Working 5 days a week in practice significantly increased the risk of burnout in Danish single-handed GPs. Spending >7.5 hours a day on patient-related tasks tended to increase the risk. We found no association between a high number of services and increased risk of burnout.

CRISPR/Cas9-mediated mutation of Eil1 transcription factor genes affects exogenous ethylene tolerance and early flower senescence in Campanula portenschlagiana.

Improving tolerance to ethylene-induced early senescence of flowers and fruits is of major economic importance for the ornamental and food industry. Genetic modifications of genes in the ethylene-signalling pathway have frequently resulted in increased tolerance but often with unwanted side effects. Here, we used CRISPR/Cas9 to knockout the function of two CpEil1 genes expressed in flowers of the diploid ornamental plant Campanula portenschlagiana. The ethylene tolerance in flowers of the primary mutants with knockout of only one or all four alleles clearly showed increased tolerance to exogenous ethylene, although lower tolerance was obtained with one compared to four mutated alleles. The allele dosage effect was confirmed in progenies where flowers of plants with zero, one, two, three and four mutated alleles showed increasing ethylene tolerance. Mutation of the Cpeil1 alleles had no significant effect on flower longevity and endogenous flower ethylene level, indicating that CpEil1 is not involved in age-dependent senescence of flowers. The study suggests focus on EIN3/Eils expressed in the organs subjected to early senescence for obtaining tolerance towards exogenous ethylene. Furthermore, the observed allelic dosage effect constitutes a key handle for a gradual regulation of sensitivity towards exogenous ethylene, simultaneously monitoring possibly unwanted side effects.

Filtration and tubular handling of EWE-hC3Nb1, a complement inhibitor nanobody, in wild type mice and a mouse model of proteinuric kidney disease.

Tubular activation and deposition of filtered complement proteins have been implicated in the progression of proteinuric kidney disease. The potent C3b-specific nanobody inhibitor of the alternative pathway, EWE-hC3Nb1, is likely freely filtered in the glomerulus to allow complement inhibition in the tubular lumen and may provide a novel treatment option to prevent tubulointerstitial injury. However, more information on the pharmacokinetic properties and renal tubular handling of EWE-hC3Nb1 nanobody is required for its pharmacological application in relation to kidney disease. Here, we examined the pharmacokinetic properties of free EWE-hC3Nb1 in mouse plasma and urine, following subcutaneous injection in wild-type control and podocin knock out (KO) mice with severe proteinuria. Tubular handling of filtered EWE-hC3Nb1 was assessed by immunohistochemistry (IHC) on kidney tissue from control, proteinuric mice, and KO mice deficient in the proximal tubule endocytic receptor megalin. Rapid plasma absorption and elimination of EWE-hC3Nb1 was observed in both control and proteinuric mice; however, urinary excretion of EWE-hC3Nb1 was markedly increased in proteinuric mice. Urinary EWE-hC3Nb1 excretion was amplified in megalin KO mice, and substantial accumulation of EWE-hC3Nb1 was observed in megalin-expressing renal proximal tubules by IHC. Moreover, free EWE-hC3Nb1 was found to be rapidly cleared from plasma. In conclusion, filtered EWE-hC3Nb1 is reabsorbed by a megalin-dependent process in the proximal tubules. Increased load of filtered proteins in the tubular fluid may inhibit the megalin-dependent uptake of EWE-hC3Nb1 in proteinuric mice. Treatment with EWE-hC3Nb1 may allow investigation of the effects of complement inhibition in the tubular fluid.

Excited-state dynamics and fluorescence lifetime of cryogenically cooled green fluorescent protein chromophore anions.

Time-resolved action spectroscopy together with a fs-pump probe scheme is used in an electrostatic ion-storage ring to address lifetimes of specific vibrational levels in electronically excited states. Here we specifically consider the excited-state lifetime of cryogenically cooled green fluorescent protein (GFP) chromophore anions which is systematically measured across the S0-S1 spectral region (450-482 nm). A long lifetime of 5.2 ± 0.3 ns is measured at the S0-S1 band origin. When exciting higher vibrational levels in S1, the lifetime changes dramatically. It decreases by more than two orders of magnitude in a narrow energy region ∼250 cm-1 (31 meV) above the 0-0 transition. This is attributed to the opening of internal conversion over an excited-state energy barrier. The applied experimental technique provides a new way to uncover even small energy barriers, which are crucial for excited-state dynamics.

Measuring patient satisfaction with four items: validity of the client satisfaction questionnaire 4 in an outpatient population.

INTRODUCTION: Patient satisfaction with mental health services has for several decades been considered an important component when evaluating service quality. It is often assessed in the context of monitoring quality of care, developing or evaluating newly implemented interventions or changes in practice. Because of this, patient satisfaction questionnaires are often added to longer questionnaire batteries, and shorter questionnaires are preferred to prevent respondent fatigue and non-compliance and to secure easy implementation. However, most studies use unvalidated patient satisfaction measures, making comparisons between studies difficult. Validation studies of short patient satisfaction measures are therefore warranted. METHODS: The primary aim was to examine the construct validity and internal reliability of the Client Satisfaction Questionnaire-4 (CSQ-4) in a Norwegian outpatient mental health setting. A total of 467 patients were recruited from an outpatient psychiatric care clinic in Central Norway. The secondary aim was to examine an earlier proposed cutoff for classifying dissatisfied patients in this new population. A principal component analysis was conducted to evaluate factor structure, correlation analyses were conducted to test for predicted relationships, and Cronbach's alpha was calculated to examine internal reliability. RESULTS: The CSQ-4 showed a clear unidimensional structure with one factor explaining 80% of its variance. Its internal reliability was very high, with a Cronbach's alpha of 0.92. As hypothesised this study found no statistically significant sex differences in satisfaction and no statistically significant association between age and satisfaction. Positive changes in symptoms during treatment and higher post-treatment functional impairment were associated with higher patient-reported treatment satisfaction scores, which indicates good construct validity. CONCLUSION: This is the first study to evaluate the CSQ-4 in a psychiatric population. The CSQ-4 demonstrated good structural validity and internal reliability and was correlated with outcome variables in terms of symptom change and post-treatment functioning. In sum, this indicates that the CSQ-4 is a good short alternative for evaluating patient satisfaction in routine outpatient mental health care.

The construct validity of an abridged version of the general self-efficacy scale for adults with attention-deficit/hyperactivity disorder.

Objectives: The General Self-Efficacy (GSE) scale is a validated self-rated questionnaire increasingly used in mental health research. However, despite several psychometric advantages of the GSE scale, its validity in those diagnosed with attention-deficit/hyperactivity disorder (ADHD) has not yet been examined. Moreover, a shorter version of the GSE scale would contribute to a more rational use of resources in extensive multivariate studies. Therefore, as self-rated scales to measure self-efficacy in this population are lacking, the current study aims to develop a condensed version of the GSE for adults with ADHD. Methods: A group of patient collaborators (user representatives) from an ADHD organization and health professionals shortened the original 10-item GSE scale to six items and evaluated the content validity of the revised scale. Second, 525 potential participants were invited to participate in a cross-sectional study conducted in 2021 (between January 19th and February 7th). Of them, 403 filled out the GSE-6 for ADHD and two scales measuring psychological well-being and mental health (the five-item World Health Organization Well-Being Index, WHO-5, and the four-item Patient Health Questionnaire, PHQ-4). The psychometric properties of the new scale were examined, testing a priori formulated hypotheses. Results: The brief GSE-6 for ADHD displayed good internal consistency with a Cronbach's α of 0.907. No floor or ceiling effect was detected. Exploratory and confirmatory factor analyses supported a one-factor structure. The GSE-6 also showed a moderate positive correlation with the WHO-5 (rs = 0.578) and a moderate negative correlation with the depression and anxiety rating scale PHQ-4 (rs = -0.595). Conclusion: The 6-item GSE for ADHD was evaluated to have good content validity. The scale demonstrated good psychometric properties. The results indicate that the GSE-6 may help assess self-efficacy in adults with ADHD.

Atomic Layer Deposition as the Enabler for the Metastable Semiconductor InN and Its Alloys.

Indium nitride (InN) is a low-band-gap semiconductor with unusually high electron mobility, making it suitable for IR-range optoelectronics and high-frequency transistors. However, the development of InN-based electronics is hampered by the metastable nature of InN. The decomposition temperature of InN is lower than the required growth temperature for most crystal growth techniques. Here, we discuss growth of InN films and epitaxial layers by atomic layer deposition (ALD), a growth technique based on self-limiting surface chemical reactions and, thus, inherently a low-temperature technique. We describe the current state of the art in ALD of InN and InN-based ternary alloys with GaN and AlN, and we contrast this to other growth technologies for these materials. We believe that ALD will be the enabling technology for realizing the promise of InN-based electronics.

Secondary ionization of pyrimidine nucleobases and their microhydrated derivatives in helium nanodroplets.

Radiation damage in biological systems by ionizing radiation is predominantly caused by secondary processes such as charge and energy transfer leading to the breaking of bonds in DNA. Here, we study the fragmentation of cytosine (Cyt) and thymine (Thy) molecules, clusters and microhydrated derivatives induced by direct and indirect ionization initiated by extreme-ultraviolet (XUV) irradiation. Photofragmentation mass spectra and photoelectron spectra of free Cyt and Thy molecules are compared with mass and electron spectra of Cyt/Thy clusters and microhydrated Cyt/Thy molecules formed by aggregation in superfluid helium (He) nanodroplets. Penning ionization after resonant excitation of the He droplets is generally found to cause less fragmentation compared to direct photoionization and charge-transfer ionization after photoionization of the He droplets. When Cyt/Thy molecules and oligomers are complexed with water molecules, their fragmentation is efficiently suppressed. However, a similar suppression of fragmentation is observed when homogeneous Cyt/Thy clusters are formed in He nanodroplets, indicating a general trend. Penning ionization electron spectra (PIES) of Cyt/Thy are broad and nearly featureless but PIES of their microhydrated derivatives point at a sequential ionization process ending in unfragmented microsolvated Cyt/Thy cations.

Interlocking Matrix and Filler for Enhanced Individualization and Reinforcement in Polymer-Single-Walled Carbon Nanotube Composites.

Poor individualization and interfacial adhesion prevent single-walled carbon nanotube (SWNT)-polymer composites from reaching outstanding mechanical properties. With much larger diameters, but common structural features (high aspect ratio and absence of functional groups for covalent or supramolecular attachment with the polymer), carbon fibers face similar problems, which are addressed by covering the fibers with a thin layer of polymer. This sizing strategy has allowed carbon fibers to become the filler of choice for the highest performing materials. Inspired by this, here we investigate the use of the mechanical bond to wrap SWNTs with a layer of polymeric material to produce SWNTs mechanically interlocked with a layer of polymer. We first validate the formation of mechanically interlocked nanotubes (MINTs) using mixtures of SWNTs of relatively large average diameter (1.6 ± 0.4 nm), which are commercially available at reasonable prices and therefore could be technologically relevant as polymer fillers. We then design and synthesize by ring-opening metathesis polymerization (ROMP) a polymer decorated with multiple U-shaped molecules, which are later ring-closed around the SWNTs using metathesis. The obtained hybrids contain a high degree of individualized SWNTs and exhibit significantly increased mechanical properties when compared to the matrix polymer. We envision that this strategy could be employed to produce SWNTs interlocked with polymer layers with various designs for polymer reinforcement.