Thermal and electron stimulated chemistry of complex adsorbates on metal surfaces

Due to intrinsic limitations of conventional silicon based devices the trend of miniaturisation cannot continue indefinitely, thus molecular devices are being used to develop smaller, faster and higher storage density memory devices. We present a thermally activated, switchable hetero-polyoxometalate (HPOM) cluster immobilised on a highly polarisable gold surface which has potential as such a device. This cluster consists of a nanometre sized Mo(IV) oxide “shell” which encapsulates two electronically active pyramidal sulfite (SIVO32-) groups, and has the ability to reversibly interconvert between two electronic states. In the passive state, at cryogenic temperatures (77 K), the two SO32- groups are non-bonding with respect to the sulfur centres, however upon thermal activation, i.e. when the temperature is increased to room (298 K), two electrons are ejected from the active sulfite anions and delocalised over the metal oxide cluster cage. This has the effect of switching it from a fully oxidised to a two-electron reduced state, along with the concomitant formation of an S-S bonding interaction between the two sulfur centres inside the cluster shell. This process does not occur in the crystalline state and to proceed requires the stabilising effects provided by an image charge, generated as a consequence of being adsorbed onto a metal surface. The prototypical enantio-selective heterogeneously catalysed reaction involves the hydrogenation of the α-ketoester, methyl pyruvate on Pt. Using TPD, XPS and UPS we have investigated this compound’s behaviour on a model Cu(111) single crystal surface. Monolayers of methyl pyruvate at 180 K consist predominately (ca. 66%) of a chemisorbed methyl pyruvate moiety, with its keto-carbonyl bonded to the surface in a η2configuration, this moiety desorbs intact at 364 K. The rest of the monolayer contains weakly adsorbed methyl pyruvate, which desorbs at 234 K, and interacts with the surface through the lone pair electrons of the oxygen atoms of the C=O groups, adopting a η1 configuration. The observation of a strongly chemisorbed moiety in the present study is attributed to the activation of the keto-carbonyl by the electron withdrawing ester group, and is consistent with the homogeneous inorganic chemistry of ketones. It is widely assumed that the α-ketoester needs to be π-bonded to the surface for the enantio-selective hydrogenation to proceed, consequently, given both the formation of a η2 bonded methyl pyruvate moiety on Cu(l11) and the known activity of Cu as a selective hydrogenation catalyst, it is suggested that it is maybe worthwhile considering the possibility of testing the effectiveness of chirally modified supported Cu as an enantio-selective catalyst. The thermal and electron induced chemistry of (S)- and (R)-methyl lactate (MLac) on Cu(111) was investigated; both enantiomers exhibited similar behaviour. MLac adopts one of two adsorption modes on the terraces of a Cu(111) crystal, which desorb molecularly at 209 K and 220 K. Concerning the molecules adsorbed at defect sites, as the temperature is increased over the range 250 – 300 K, a fraction desorb intact, while the majority lose a hydrogen atom to form the more strongly bound alkoxy species on the surface. Of these, some recombine with the hydrogen and proceed to desorb as MLac at 360 K, while a larger proportion are dehydrogenated further and methyl pyruvate and hydrogen are ejected from the surface at 380 K. When a monolayer of MLac is irradiated with a low energy electron beam, the molecules at the terrace sites are electronically excited and desorb as intact molecules, while those at the defect sites undergo electron induced hydroxyl O-H bond cleavage. Subsequent to electron bombardment there is consequently a decrease in molecularly adsorbed MLac and an increase in the number of strongly bound alkoxy species on the surface, entities which are not susceptible to ESD. We believe the ESD excitation mechanism is dissociative electron attachment. Low energy electrons of <1 eV are prevalent in the secondary electron background and can excite the hydroxyl O-H stretch, facilitating its cleavage at a threshold of 1.4 + 0.7 eV. The cross sections for the electron induced processes are high, 3.0 + 0.4 x 10-16 cm2 for 50 eV electrons, thus MLac is extremely susceptible to electron stimulated desorption. The enantio-specific adsorption of both the (S)- and (R)- enantiomers of methyl lactate on the chiral Cu(643)R surface has been investigated. The results from the (111) surface enabled us to assign the features in the TPD profiles. The peaks arising from molecular desorption at terrace and step sites occurred at the same temperature for both enantiomers, however, those attributed to desorption from the kink sites differed by 13 K, representing an enantio-specific difference in desorption energies of 0.94 kcal mol-1. This value is significantly larger than those observed in previous experimental work, although it is consistent with theoretical studies. Furthermore, we also observed enantio-specific surface reactions. It was found that there was a greater tendency for the (R)- enantiomer to undergo both the alkoxide recombination reaction and further dehydrogenation to methyl pyruvate, while the (S)-enantiomer had a greater proclivity to undergo total decomposition. We have discovered, to the best of our knowledge, the first example of enantio-specific surface chemistry initiated by a beam of non-chiral low energy electrons. When (S)- and (R)-methyl lactate molecularly adsorbed at the chiral kink sites of a Cu(643)R substrate is irradiated with 50 eV electrons, it has been found that (R)-methyl lactate is more receptive to both electron induced desorption of the parent molecule and electron induced cleavage of the hydroxyl O-H bond. This behaviour has been attributed to the (S)-enantiomer forming a more intimate bond with the kink site than the (R)-enantiomer, as evidenced by its higher desorption temperature. Consequently the substrate is more effective at providing relaxation channels to the electronically excited adsorbate, which reduces the probability of ESD occurring. Starting with a racemic mixture, we have demonstrated a 20% enantiomeric enrichment in the molecular adsorbates at the chiral kink sites, after only 30% depletion of the initial population. As a control, the initial rates of desorption from terrace and step sites were found to be unaffected by enantiomeric identity, which was to be expected because these sites are achiral, and as such both enantiomers interact to a similar degree with each. When the monolayer is considered as a whole, it was found that electron irradiation drives desorption more completely with an (R)-MLac covered surface than with (S). It has been suggested that this property of the system could be exploited in the laboratory as a method for separating racemic mixtures, and that in an astrochemical context, it could provide insight into the origins of biohomochirality.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Can the APO method be used for measuring soft data?: A pilot study.

Objectives. The aims were to develop auditing according to the APO (Audit Project Odense) method for measuring soft data, exemplified by a holistic view, and to test the instrument. Design. A descriptive study of the development of an APO chart and a test registration. Setting. Primary health care, Blekinge County, Sweden. Subjects. Ten general practitioners (GPs) were invited to transform categories of the concept of a holistic view obtained in an earlier study, into 30 variables on an APO registration chart. The participants chose to study different kinds of knowledge as aspects of holistic care. Main outcome measure. An APO registration chart and test of the instrument. Results. After three meetings the group had drawn up an APO registration chart supplemented with Likert scales. A pilot audit was performed. Eight doctors registered 255 consultations. In assessment of the patients' problems, factual medical knowledge was important in 83% of the cases, familiarity in 53%, and a capacity for judgement in 36%. In decision-making factual medical knowledge was used in 88% and capacity for judgement in 58%. A holistic view was necessary for the outcome in 43% and valuable in 25%. The GPs used the Likert scales in a majority of the cases. Conclusions. In this first step in developing an instrument, the results indicate that the APO method could be an alternative for studying what happens in the consultation, and the occurrence of an abstract phenomenon such as the use of different kinds of knowledge as part of a holistic view

Seasonality of fertility measured by physical activity traits in Holstein cows

AbstractSeasonality of female fertility traits, including the interval from calving to first high activity (CFHA), duration of high activity episode (DHA), and strength of high activity episode (SHA) of first estrus, were studied. The physical activity traits were derived from electronic activity tags for 20,794 Holstein cows in 135 commercial Holstein herds in Denmark. Data were categorized in 3 ways: (1) into 4 seasons of calving: winter (January–March), spring (April–June), summer (July–September), and fall (October–December); (2) into 2 seasons: a cold season (October–March) and a warm season (April–September); and (3) into an increasing light season (IL; January–June), where daylight hours gradually increased, and a decreasing light season (DL; July–December), where daylight hours gradually decreased. At the phenotypic level, least squares means of CFHA were highest at 55d for cows calving in December and lowest at 31d for cows calving in September. The highest least squares means of DHA and SHA were recorded for cows calving in November and lowest for cows calving in May and June. Genetic parameters for all traits were estimated using average information-REML in a bivariate animal model that treated the same trait in different calving seasons as different traits. Heritability estimates for CFHA were highest for the winter season (0.13) and low for the other seasons (0.03–0.04), whereas heritability estimates for DHA and SHA were lowest for winter and highest for fall. Heritability estimates for CFHA for the cold season (0.17) was higher than that for the warm season (0.10). Heritability estimates of CFHA for the IL season (0.12) was higher than for the DL season (0.07), but the opposite pattern was found for DHA and SHA. Genetic correlations (rA) of CFHA between winter and summer (rA=0.34±0.27), and winter and fall (rA=0.65±0.20) were significantly lower than unity. The corresponding correlations of DHA and SHA between seasons were all close to unity, except for the correlation of SHA between winter and fall (rA=0.36±0.34). When the year was split into only 2 seasons, the genetic correlation of CFHA between cold and warm seasons was only moderate (rA=0.46±0.15) but was slightly stronger between IL and DL seasons (rA=0.63±0.16); both significantly deviated from unity. These results indicate the existence of a genotype by environment interaction for CFHA regardless of calving season classification

Dementia prevention : The potential long-term cost-effectiveness of the FINGER prevention program

Introduction The aim of this study was to estimate the potential cost-effectiveness of the Finnish Geriatric Intervention Study to Prevent Cognitive Impairment and Disability (FINGER) program. Methods A life-time Markov model with societal perspective, simulating a cohort of people at risk of dementia reflecting usual care and the FINGER program. Results Costs were 1,653,275 and 1,635,346 SEK and quality-adjusted life years (QALYs) were 8.636 and 8.679 for usual care and the FINGER program, respectively, resulting in savings of 16,928 SEK (2023 US$) and 0.043 QALY gains per person, supporting extended dominance for the FINGER program. A total of 1623 dementia cases were avoided with 0.17 fewer person-years living with dementia. The sensitivity analysis confirmed the conclusions in most scenarios. Discussion The model provides support that programs like FINGER have the potential to be cost-effective in preventing dementia. Results at the individual level are rather modest, but the societal benefits can be substantial because of the large potential target population.Peer reviewe

Effect of a Multidomain Lifestyle Intervention on Estimated Dementia Risk

We investigated the effect of a multidomain lifestyle intervention on the risk of dementia estimated using the validated CAIDE risk score (post-hoc analysis). The Finnish Geriatric Intervention Study to Prevent Cognitive Impairment and Disability (FINGER) is a 2-year randomized controlled trial among 1,260 at-risk older adults (60-77 years). Difference in the estimated mean change in CAIDE score at 2 years in the intervention compared to the control group was -0.16 (95 % CI -0.31 to 0.00) (p = 0.013), corresponding to a relative dementia risk reduction between 6.04-6.50%. This could be interpreted as a reflection of the prevention potential of the intervention.Peer reviewe

Resource tracking within and across continents in long-distance bird migrants

Migratory birds track seasonal resources across and between continents. We propose a general strategy of tracking the broad seasonal abundance of resources throughout the annual cycle in the longest-distance migrating land birds as an alternative to tracking a certain climatic niche or shorter-term resource surplus occurring, for example, during spring foliation. Whether and how this is possible for complex annual spatiotemporal schedules is not known. New tracking technology enables unprecedented spatial and temporal mapping of long-distance movement of birds. We show that three Palearctic-African species track vegetation greenness throughout their annual cycle, adjusting the timing and direction of migratory movements with seasonal changes in resource availability over Europe and Africa. Common cuckoos maximize the vegetation greenness, whereas red-backed shrikes and thrush nightingales track seasonal surplus in greenness. Our results demonstrate that the longest-distance migrants move between consecutive staging areas even within the wintering region in Africa to match seasonal variation in regional climate. End-of-century climate projections indicate that optimizing greenness would be possible but that vegetation surplus might be more difficult to track in the future

Mental health problems, health risk behaviors, and prevention: A qualitative interview study on perceptions and attitudes among elite male soccer players

BackgroundThe purpose of this study was to investigate the perception of mental health problems and health risk behaviors among Swedish male elite soccer players and their attitudes toward possible prevention strategies.MethodTwenty elite soccer players, aged 15–30 years, were recruited through purposive sampling and interviewed via a digital video calling platform. A semi-structured interview guide, encompassing questions about mental health problems, health risk behaviors among soccer teams, peer-relations, relations to coaches, and attitudes toward health risk behaviors, along with proposals for effective interventions, was employed. The interviews were transcribed verbatim and analyzed with qualitative content analysis.ResultsThe informants reported positive feelings in relation to playing soccer, good health, and few health risk behaviors. Risk factors included a large income, excessive free time, and the need for excitement. Stress and mental health problems were linked to performance pressure, social media, and injuries. Hesitation to talk openly about personal problems due to concerns about negative consequences and the “macho culture” was highlighted as barriers to admit and seek help for personal problems. Some statements indicated openness and the club's efforts to destigmatize personal problems. Positive attitudes toward prevention and suggestions for various measures were prominent.ConclusionFuture research and implementation of interventions should focus on the prevention of health risk behaviors and alleviation of stress and performance pressure, as well as continue the efforts to destigmatize mental health problems and raise awareness among coaches of the importance of their communication and behavior for players' mental health and performance. This could be achieved by developing strategic and systematic policy work, information, and dialogue among players and coaches, in addition to individual digital or face-to-face support, provided by professionals outside the soccer context

Detailed diesel exhaust characteristics including particle surface area and lung deposited dose for better understanding of health effects in human chamber exposure studies.

Several diesel exhaust (DE) characteristics, comprising both particle and gas phase, recognized as important when linking with health effects, are not reported in human chamber exposure studies. In order to understand effects of DE on humans there is a need for better characterization of DE when performing exposure studies. The aim of this study was to determine and quantify detailed DE characteristics during human chamber exposure. Additionally to compare to reported DE properties in conducted human exposures. A wide battery of particle and gas phase measurement techniques have been used to provide detailed DE characteristics including the DE particles (DEP) surface area, fraction and dose deposited in the lungs, chemical composition of both particle and gas phase such as NO, NO2, CO, CO2, volatile organic compounds (including aldehydes, benzene, toluene) and polycyclic aromatic hydrocarbons (PAHs). Eyes, nose and throat irritation effects were determined. Exposure conditions with PM1 (<1 mm) mass concentration 280 mg m3, number concentration 4 105 cm3 and elemental to total carbon fraction of 82% were generated from a diesel vehicle at idling. When estimating the lung deposited dose it was found that using the size dependent effective density (in contrast to assuming unity density) reduced the estimated respiratory dose by 132% by mass. Accounting for agglomerated structure of DEP prevented underestimation of lung deposited dose by surface area by 37% in comparison to assuming spherical particles. Comparison of DE characteristics reported in conducted chamber exposures showed that DE properties vary to a great extent under the same DEP mass concentration and engine load. This highlights the need for detailed and standardized approach for measuring and reporting of DE properties. Eyes irritation effects, most probably caused by aldehydes in the gas phase, as well as nose irritation were observed at exposure levels below current occupational exposure limit values given for exhaust fumes. Reporting detailed DE characteristics that include DEP properties (such as mass and number concentration, size resolved information, surface area, chemical composition, lung deposited dose by number, mass and surface) and detailed gas phase including components known for their carcinogenic and irritation effect (e.g. aldehydes, benzene, PAHs) can help in determination of key parameters responsible for observed health effects and comparison of chamber exposure studies