Narrow homogeneous linewidths and slow cooling dynamics across infrared intra-band transitions in n-doped HgSe colloidal quantum dots.

Intra-band transitions in colloidal quantum dots (QDs) are promising for opto-electronic applications in the mid-IR spectral region. However, such intra-band transitions are typically very broad and spectrally overlapping, making the study of individual excited states and their ultrafast dynamics very challenging. Here, we present the first full spectrum two-dimensional continuum infrared (2D CIR) spectroscopy study of intrinsically n-doped HgSe QDs, which exhibit mid-infrared intra-band transitions in their ground state. The obtained 2D CIR spectra reveal that underneath the broad absorption line shape of ∼500 cm-1, the transitions exhibit surprisingly narrow intrinsic linewidths with a homogeneous broadening of 175-250 cm-1. Furthermore, the 2D IR spectra are remarkably invariant, with no sign of spectral diffusion dynamics at waiting times up to 50 ps. Accordingly, we attribute the large static inhomogeneous broadening to the distribution of size and doping level of the QDs. In addition, the two higher-lying P-states of the QDs can be clearly identified in the 2D IR spectra along the diagonal with a cross-peak. However, there is no indication of cross-peak dynamics indicating that, despite the strong spin-orbit coupling in HgSe, transitions between the P-states must be longer than our maximum waiting time of 50 ps. This study illustrates a new frontier of 2D IR spectroscopy enabling the study of intra-band carrier dynamics in nanocrystalline materials across the entire mid-infrared spectrum.

Full spectrum 2D IR spectroscopy reveals below-gap absorption and phonon dynamics in the mid-IR bandgap semiconductor InAs.

While the mid-infrared spectral region spans more than 3000 cm-1, ultrafast mid-IR spectroscopies are normally limited to the spectral bandwidth that can be generated in optical parametric amplifiers-typically a few hundred cm-1. As such, the spectral coverage in conventional two dimensional infrared (2D IR) spectroscopy captures only about 1% of the full potential 2D mid-IR spectrum. Here, we present 2D IR spectra using a continuum source as both the excitation and probe pulses, thus capturing close to the full 2D IR spectrum. While the continuum pulses span the entire mid-IR range, they are currently too weak to efficiently excite molecular vibrational modes but strong enough to induce electronic responses and excite phonons in semiconductors. We demonstrate the full spectrum 2D IR spectroscopy of the mid-IR bandgap semiconductor indium arsenide with a bandgap at 2855 cm-1. The measured response extends far below the bandgap and is due to field-induced band-shifting, causing probe absorption below the bandgap. While the band-shifting induces an instantaneous response that exists only during pulse overlap, the 2D IR spectra reveal additional off-diagonal features that decay on longer timescales. These longer-lived off-diagonal features result from coherent phonons excited via a Raman-like process at specific excitation frequencies. This study illustrates that the full spectrum 2D IR spectroscopy of electronic states in the mid-IR is possible with current continuum pulse technology and is effective in characterizing semiconductor properties.

Trends in dentate status and preventive dental visits of the adult population in Denmark over 30 years (1987-2017).

This study analyzed the trend in self-reported dentate status over 30 years (1987-2017) among Danish adults, the self-reported frequencies of preventive dental visits undertaken annually during the period 1987-2013, and the self-reported use of the 2016 recall scheme for preventive dental check-ups. The impact of social determinants (education, employment, civil status, and ethnic background) on these dental outcome variables in 2017 was explored. Questionnaire data were obtained from the Danish Health and Morbidity Surveys conducted from 1987-2017, and they were analyzed by tri-variate frequency distributions and multivariate analyses. The prevalence of complete tooth loss was 17.7% in 1987 but 3.4% in 2017. The frequency of adults having 20 or more teeth grew markedly from 1987 (65.9%) to 2017 (85.1%). Educational inequality in dentate status persisted over the period. The frequency of preventive dental visits at least annually increased from 1987 to 2013, although visits were less frequent for young people. In 2017, preventive dental check-ups were reported in intervals: less than 12 months (56.4%), 12-18 months (18.9%), 19-24 months (4.8%), and more than 24 months (5.2%). In 2017, dentate status and preventive dental check-ups varied profoundly by social determinants. In conclusion, social policies should be implemented to tackle the persistent inequities in dentate status and public health policies should target Universal Health Coverage.

Twenty-four-hour fluid administration in emergency department patients with suspected infection: A multicenter, prospective, observational study.

BACKGROUND: To describe 24-hour fluid administration in emergency department (ED) patients with suspected infection. METHODS: A prospective, multicenter, observational study conducted in three Danish hospitals, January 20 to March 2, 2020. We included consecutive adult ED patients with suspected infection (drawing of blood culture and/or intravenous antibiotic administration within 6 hours of admission). Oral and intravenous fluids were registered for 24 hours. PRIMARY OUTCOME: 24-hour total fluid volume. We used linear regression to investigate patient and disease characteristics' effect on 24-hour fluids and to estimate the proportion of the variance in fluid administration explained by potential predictors. RESULTS: 734 patients had 24-hour fluids available: 387 patients had simple infection, 339 sepsis, eight septic shock. Mean total 24-hour fluid volumes were 3656 mL (standard deviation [SD]:1675), 3762 mL (SD: 1839), and 6080 mL (SD: 3978) for the groups, respectively. Fluid volumes varied markedly. Increasing age (mean difference [MD]: 60-79 years: -470 mL [95% CI: -789, -150], +80 years; -974 mL [95% CI: -1307, -640]), do-not-resuscitate orders (MD: -466 mL [95% CI: -797, -135]), and preexisting atrial fibrillation (MD: -367 mL [95% CI: -661, -72) were associated with less fluid. Systolic blood pressure < 100 mmHg (MD: 1182 mL [95% CI: 820, 1543]), mean arterial pressure < 65 mmHg (MD: 1317 mL [95% CI: 770, 1864]), lactate ≥ 2 mmol/L (MD: 655 mL [95% CI: 306, 1005]), heart rate > 120 min (MD: 566 [95% CI: 169, 962]), low (MD: 1963 mL [95% CI: 813, 3112]) and high temperature (MD: 489 mL [95% CI: 234, 742]), SOFA score > 5 (MD: 1005 mL [95% CI: 501, 510]), and new-onset atrial fibrillation (MD: 498 mL [95% CI: 30, 965]) were associated with more fluid. Clinical variables explained 37% of fluid variation among patients. CONCLUSIONS: Patients with simple infection and sepsis received equal fluid volumes. Fluid volumes varied markedly, a variation that was partly explained by clinical characteristics.

Heterodyne-detected sum frequency generation of water at surfaces with varying hydrophobicity.

Aqueous surfaces mediate many atmospheric, biological, and technological processes. At the interface, the bulk hydrogen-bonding network is terminated and the interfacial water molecules restructure according to the surface chemistry of the interface. Given the complexity of both natural and technical aqueous interfaces, self-assembled monolayers provide a platform for controllably tuning the chemical composition of the surface and thus the water restructuring. Here, we study a hydrophobic monolayer, a hydrophilic monolayer, and a mixed hydrophobic/hydrophilic monolayer in contact with water. Monolayers composed of both hydrophilic and hydrophobic chains mimic the complex and heterogeneous chemical composition of natural and technological surfaces. By employing heterodyne-detected sum frequency generation, the purely absorptive vibrational line shape of interfacial water is measured experimentally. We examined the structure of the interfacial water in contact with each of the monolayers by analyzing the relative dipole moment orientations and fitting the imaginary component of χ(2) with a combination of Lorentzian and Gaussian line shapes. For all of the monolayers, the hydrogen-bonded water points toward the monolayer, which is opposite of the orientation of the hydrogen-bonded water at the air-water interface. Additionally, a strongly hydrogen-bonded water species exists for the monolayers containing hydrophilic chains. The spectroscopic results suggest that the microscopic water structure in contact with the mixed monolayer is dominated by the hydrophilic parts of the monolayer, while the contact angle shows that at the macroscopic level the surface properties lie closer to the pure hydrophobic monolayer.

Remote real-time supervision via tele-ultrasound in focused cardiac ultrasound: A single-blinded cluster randomized controlled trial.

BACKGROUND: Supervision via tele-ultrasound presents a remedy for lacking on-site supervision in focused cardiac ultrasound, but knowledge of its impact is largely absent. We aimed to investigate tele-supervised physicians' cine-loop quality compared to that of non-supervised physicians and compared to that of experts. METHODS: We conducted a single-blinded cluster randomized controlled trial in an emergency department in western Denmark. Physicians with basic ultrasound competence scanned admitted patients twice. The first scan was non-supervised, and the second was non-supervised (control) or tele-supervised (intervention). Finally, experts in focused cardiac ultrasound scanned the same patient. Two blinded observers graded cine-loops recorded from all scans on a 1-5 scale. The outcome was the mean summarized scan gradings compared with a linear mixed-effects model. RESULTS: In each group, 10 physicians scanned 44 patients. From the mean summarized gradings, on a scale from 4 to 20, the second non-supervised scan grading was 10.9 (95% CI 10.2-11.7), whereas the tele-supervised grading was 12.6 (95% CI: 11.8-13.3). From the first to the second scan, tele-supervised physicians moved 9% (1.09; 95% CI: 1.00-1.19; P = 0.041) closer to the experts' quality than the non-supervised physicians. CONCLUSION: Tele-supervised physicians performed scans of better quality than non-supervised physicians. The present study supports the use of tele-supervision for physicians with basic focused ultrasound competence in a setting where on-site supervision is unavailable.

Remote Real-Time Ultrasound Supervision via Commercially Available and Low-Cost Tele-Ultrasound: a Mixed Methods Study of the Practical Feasibility and Users' Acceptability in an Emergency Department.

Minor emergency departments (ED) struggle to access sufficient expertise to supervise learners of lung and cardiac point-of-care ultrasound (POCUS). Using tele-ultrasound (tele-US) for remote supervision may remedy this situation. We aimed to evaluate the feasibility of real-time supervision via tele-US when applied to an everyday ED clinic. We conducted a mixed methods study that assessed practical feasibility, determined performance, and explored users' acceptability of supervision via tele-US. Technical performance was assessed quantitatively by the ratio in mean gray value between images on site and as received by the supervisor, and by after-compression frame rate. Qualitatively, 12 exploratory semi-structured interviews were conducted with exposed junior doctors and supervisors. Remote supervision via tele-US was performed with 10 junior doctors scanning 45 included patients. During performance assessment, neither alternating internet connection nor software significantly changed the mean gray value ratio. The lowest median frame rate of 4.6 (interquartile range [IQR]: 3.1-5.0) was found by using a 4G internet connection; the highest of 28.5 (IQR: 28.5-29.0) was found with alternative computer and local area network internet connection. In interviews, supervisors stressed the importance of preserving frame rate, and junior doctors emphasized a need for shared ultrasound terminology. In the qualitative analysis, setup mobility, accessibility, and time consumption were emphasized as being of key importance for future clinical implementations. Remote supervision via a commercially available and low-cost tele-US setup is operational for both junior doctors and supervisors when applied to lung and cardiac POCUS scans of hospitalized patients.

Interpreting Quasi-Thermal Effects in Ultrafast Spectroscopy of Hydrogen-Bonded Systems.

Vibrational excitation of molecules in the condensed phase relaxes through vibrational modes of decreasing energy to ultimately generate an equilibrium state in which the energy is distributed among low-frequency modes. In ultrafast vibrational spectroscopy, changes in the vibrational features of hydrogen-bonded NH and OH stretch modes are typically observed to persist long after these high-frequency vibrations have relaxed. Due to the resemblance to the spectral changes caused by heating the sample, these features are typically described as arising from a hot ground state. However, these spectral features appear on ultrafast time scales that are much too fast to result from a true thermal state, and significant differences between the thermal difference spectrum and the induced quasi-thermal changes in ultrafast spectroscopy are often observed. Here, we examine and directly compare the thermal and quasi-thermal responses of the hydrogen-bonded homodimer of 7-azaindole with temperature-dependent FTIR spectroscopy and ultrafast mid-IR continuum spectroscopy. We find that the thermal difference spectra contain contributions from both dissociation of the hydrogen bonds and from frequency shifts due to changes in the thermal population of low-frequency modes. The transient spectra in ultrafast vibrational spectroscopy are also found to contain two contributions: initial frequency shifts over 2.3 ± 0.11 ps associated with equilibration of the initial excitation, and frequency shifts associated with the excitation of several fingerprint modes, which decay over 21.8 ± 0.11 ps, giving rise to a quasi-thermal response caused by a distribution of fingerprint modes being excited within the sample ensemble. This resembles the thermal frequency shifts due to population changes of low-frequency modes, but not the overall thermal spectrum, which is dominated by features caused by dimer dissociation. These findings provide insight into the changes in the vibrational spectrum from different origins and are important for assigning, analyzing, and comparing features in thermal and ultrafast vibrational spectroscopy of hydrogen-bonded complexes.

Vibrational tug-of-war: The pKA dependence of the broad vibrational features of strongly hydrogen-bonded carboxylic acids.

Medium and strong hydrogen bonds give rise to broad vibrational features frequently spanning several hundred wavenumbers and oftentimes exhibiting unusual substructures. These broad vibrational features can be modeled from first principles, in a reduced dimensional calculation, that adiabatically separates low-frequency modes, which modulate the hydrogen bond length, from high-frequency OH stretch and bend modes that contribute to the vibrational structure. Previously this method was used to investigate the origin of an unusual vibrational feature frequently found in the spectra of dimers between carboxylic acids and nitrogen-containing aromatic bases that spans over 900 cm-1 and contains two broad peaks. It was found that the width of this feature largely originates from low-frequency modes modulating the hydrogen bond length and that the structure results from Fermi resonance interactions. In this report, we examine how these features change with the relative acid and base strength of the components as reflected by their aqueous pKA values. Dimers with large pKA differences are found to have features that can extend to frequencies below 1000 cm-1. The relationships between mean OH/NH frequency, aqueous pKA, and O-N distance are examined in order to obtain a more rigorous understanding of the origin and shape of the vibrational features. The mean OH/NH frequencies are found to correlate well with O-N distances. The lowest OH stretch frequencies are found in dimer geometries with O-N distances between 2.5 and 2.6 Å. At larger O-N distances, the hydrogen bonding interaction is not as strong, resulting in higher OH stretch frequencies. When the O-N distance is smaller than 2.5 Å, the limited space between the O and N determines the OH stretch frequency, which gives rise to frequencies that decrease with O-N distances. These two effects place a lower limit on the OH stretch frequency which is calculated to be near 700 cm-1. Understanding how the vibrational features of strongly hydrogen-bonded structures depend on the relative pKA and other structural parameters will guide studies of biological structures and analysis of proton transfer studies using photoacids.

Cross sectional study of multiresistant bacteria in Danish emergency departments: prevalence, patterns and risk factors for colonization (AB-RED project).

BACKGROUND: Multiresistant bacteria (MRB) is an increasing problem. Early identification of patients with MRB is mandatory to avoid transmission and to target the antibiotic treatment. The emergency department (ED) is a key player in the early identification of patients who are colonized with MRB. There is currently sparse knowledge of both prevalence and risk factors for colonization with MRSA, ESBL, VRE, CPE and CD in acutely admitted patients in Western European countries including Denmark. To develop evidence-based screening tools for identifying carriers of resistant bacteria among acutely admitted patients, systematic collection of information on risk factors and exposures is required. Since a geographical variation is suspected, it is desirable to include emergency departments across the country. The aim of this project is to provide a comprehensive overview of prevalence and risk factors for MRSA, ESBL, VRE, CPE and CD colonization in patients admitted to Danish ED's. The objectives are to describe the prevalence and demography of resistance, co-infections, to identify risk factors for carrier state and to develop and validate a screening tool for identification of carriers. METHODS: Multicenter descriptive and analytic cross-sectional survey from January-May 2018 of around 10.000 acutely admitted patients > 18 years in 8 EDs for carrier state and risk factors for antibiotic resistant bacteria. Information about the background and possible risk factors for carrier status together with swabs from the nose, throat and rectum is collected and analyzed for MRSA, ESBL, VRE, CPE and CD. The prevalence of the resistant bacteria are calculated at hospital level, regional level and national level and described with relation to residency, sex, age and risk factors. A screening model for identification of carrier stage of resistant bacteria is developed and validated. DISCUSSION: The study will provide the prevalence of colonized patients with resistant bacteria on arrival to the ED and variation in demographic patterns, and will develop a clinical tool to identify certain risk groups. This will enable the clinician to target antibiotic treatments and to reduce the in-hospital spreading of resistant bacteria. This knowledge is important for implementing and evaluating antimicrobial stewardships, screening and infection control strategies. TRIAL REGISTRATION: Clinicaltrials.gov : NCT03352167 (registration date: 20. November 2017).

Promoting Oral Health and Quality of Life of Older People - The Need for Public Health Action.

PURPOSE: This report intends to review the global burden of oral disease among older people and to examine their oral health needs. The evidence on the inter-relationships between poor oral health conditions of older people, general health and quality of life is highlighted. Finally, WHO strategies to improve oral health of older people are reviewed. METHODS: The information relevant to this review was extracted from the WHO Global Oral Health Data Bank, the PubMed database, and the Cochrane Library. Surveys were carried out according to the criteria recommended by the WHO epidemiological manual Oral Health Surveys - Basic Methods. In addition, global data were sought on coverage of oral health care among older people. Finally, WHO policy documents on health care for aged people were gathered through the WHO website. RESULTS: Across the globe, many older people suffer from oral pain or discomfort. Poor oral health during old age is mostly manifest in high caries experience, high prevalence rates of advanced periodontal disease, severe tooth loss, dry mouth, and oral pre-cancer/cancer. In both developing and developed countries, the burden of disease is particularly high among underprivileged and disadvantaged older people. In numerous countries, high proportions of the aged population are not covered by primary oral health care; this is mainly the case in low and middle income countries due to a critical shortage of dentists. CONCLUSIONS: In 2015, the WHO published the World Report on Ageing and Health, which outlines a framework for action to foster healthy ageing. The policies are highly relevant to the improvement of oral health. Transformation of oral health systems away from a disease-based curative model and towards disease prevention, as well as the provision of older-person-centred integrated care are required. Moreover, wide-ranging public health action on ageing is urgently needed.

A combined electronic structure and molecular dynamics approach to computing the OH vibrational feature of strongly hydrogen-bonded carboxylic acids.

Medium and strong hydrogen bonds give rise to vibrational features that can span several hundreds of wavenumbers and have unusual line shapes. For example, dimers consisting of carboxylic acids hydrogen-bonded to nitrogen-containing aromatic bases exhibit a vibrational feature that spans over 900 cm-1 and contains two very broad peaks. In this report, we demonstrate how this feature can be reproduced using a combined molecular dynamics (MD) and electronic structure "spectral map" approach, which has been very successful in modeling the vibrational spectrum of water in different environments. In this approach, spectral maps are created, relating the transition frequencies and probabilities to the electric field along the OH bond, which are obtained from the density functional theory calculations of snapshots taken from a classical MD simulation. This map was used to compute the spectral properties of thousands of geometries of the pyridine-acetic acid dimer sampled by a MD simulation, which were used to compute the overall spectral feature. It was found that this approach reproduced the experimental spectrum better than the previous dimer stretch approaches (which were based on describing the dimer geometries harmonically) through a more accurate sampling of dimer geometries. The broadness of these vibrational features largely originates from the range of geometries present in the condensed phase, while the unusual line shape is caused by strong Fermi resonances.

Phosphate Ions Affect the Water Structure at Functionalized Membrane Surfaces.

Antifouling surfaces improve function, efficiency, and safety in products such as water filtration membranes, marine vehicle coatings, and medical implants by resisting protein and biofilm adhesion. Understanding the role of water structure at these materials in preventing protein adhesion and biofilm formation is critical to designing more effective coatings. Such fouling experiments are typically performed under biological conditions using isotonic aqueous buffers. Previous studies have explored the structure of pure water at a few different antifouling surfaces, but the effect of electrolytes and ionic strength (I) on the water structure at antifouling surfaces is not well studied. Here sum frequency generation (SFG) spectroscopy is used to characterize the interfacial water structure at poly(ether sulfone) (PES) and two surface-modified PES films in contact with 0.01 M phosphate buffer with high and low salt (Ionic strength, I= 0.166 and 0.025 M, respectively). Unmodified PES, commonly used as a filtration membrane, and modified PES with a hydrophobic alkane (C18) and with a poly(ethylene glycol) (PEG) were used. In the low ionic strength phosphate buffer, water was strongly ordered near the surface of the PEG-modified PES film due to exclusion of phosphate ions and the creation of a surface potential resulting from charge separation between phosphate anions and sodium cations. However, in the high ionic strength phosphate buffer, the sodium and potassium chloride (138 and 3 mM, respectively) in the phosphate buffered saline screened this charge and substantially reduced water ordering. A much smaller water ordering and subsequent reduction upon salt addition was observed for the C18-modified PES, and little water structure change was seen for the unmodified PES. The large difference in water structuring with increasing ionic strength between widely used phosphate buffer and phosphate buffered saline at the PEG interface demonstrates the importance of studying antifouling coatings in the same aqueous environment for which they are designed. These results further suggest that strong long-range water structuring is limited in high ionic strength environments, such as within cells, facilitating chemical and biological reactions and processes.

Childhood asthma and physical activity: a systematic review with meta-analysis and Graphic Appraisal Tool for Epidemiology assessment.

BACKGROUND: Childhood asthma is a global problem affecting the respiratory health of children. Physical activity (PA) plays a role in the relationship between asthma and respiratory health. We hypothesized that a low level of PA would be associated with asthma in children and adolescents. The objectives of our study were to (1) summarize the evidence available on associations between PA and asthma prevalence in children and adolescents and (2) assess the role of PA in new-onset or incident asthma among children and adolescents. METHODS: We searched Medline, the Cochrane Library, and Embase and extracted data from original articles that met the inclusion criteria. Summary odds ratios (ORs) and confidence intervals (CIs) were used to express the results of the meta-analysis (forest plot). We explored heterogeneity using funnel plots and the Graphic Appraisal Tool for Epidemiology (GATE). RESULTS: We retrieved 1,571 titles and selected 11 articles describing three cohort and eight cross-sectional studies for inclusion. A meta-analysis of the cohort studies revealed a risk of new-onset asthma in children with low PA (OR [95 % CI] 1.32 [0.95; 1.84] [random effects] and 1.35 [1.13; 1.62] [fixed effects]). Three cross-sectional studies identified significant positive associations between childhood asthma or asthma symptoms and low PA. CONCLUSIONS: Children and adolescents with low PA levels had an increased risk of new-onset asthma, and some had a higher risk of current asthma/or wheezing; however, there was some heterogeneity among the studies. This review reveals a critical need for future longitudinal assessments of low PA, its mechanisms, and its implications for incident asthma in children. The systematic review was prospectively registered at PROSPERO (registration number: CRD42014013761; available at: http://www.crd.york.ac.uk/PROSPERO [accessed: 24 March 2016]).

Origin of the Hadzi ABC structure: An ab initio study.

Medium and strong hydrogen bonds are well known to give rise to broad features in the vibrational spectrum often spanning several hundred wavenumbers. In some cases, these features can span over 1000 cm(-1) and even contain multiple broad peaks. One class of strongly hydrogen-bonded dimers that includes many different phosphinic, phosphoric, sulfinic, and selenic acid homodimers exhibits a three-peaked structure over 1500 cm(-1) broad. This unusual feature is often referred to as the Hadzi ABC structure. The origin of this feature has been debated since its discovery in the 1950s. Only a couple of theoretical studies have attempted to interpret the origin of this feature; however, no previous study has been able to reproduce this feature from first principles. Here, we present the first ab initio calculation of the Hadzi ABC structure. Using a reduced dimensionality calculation that includes four vibrational modes, we are able to reproduce the three-peak structure and much of the broadness of the feature. Our results indicate that Fermi resonances of the in-plane bend, out-of-plane bend, and combination of these bends play significant roles in explaining this feature. Much of the broadness of the feature and the ability of the OH stretch mode to couple with many overtone bending modes are captured by including an adiabatically separated dimer stretch mode in the model. This mode modulates the distance between the monomer units and accordingly the strength of the hydrogen-bonds causing the OH stretch frequency to shift from 2000 to 3000 cm(-1). Using this model, we were also able to reproduce the vibrational spectrum of the deuterated isotopologue which consists of a single 500 cm(-1) broad feature. Whereas previous empirical studies have asserted that Fermi resonances contribute very little to this feature, our study indicates that while not appearing as a separate peak, a Fermi resonance of the in-plane bend contributes substantially to the feature.

Origin of the 900 cm(-1) broad double-hump OH vibrational feature of strongly hydrogen-bonded carboxylic acids.

Medium and strong hydrogen bonds are common in biological systems. Here, they provide structural support and can act as proton transfer relays to drive electron and/or energy transfer. Infrared spectroscopy is a sensitive probe of molecular structure and hydrogen bond strength but strongly hydrogen-bonded structures often exhibit very broad and complex vibrational bands. As an example, strong hydrogen bonds between carboxylic acids and nitrogen-containing aromatic bases commonly display a 900 cm(-1) broad feature with a remarkable double-hump structure. Although previous studies have assigned this feature to the OH, the exact origin of the shape and width of this unusual feature is not well understood. In this study, we present ab initio calculations of the contributions of the OH stretch and bend vibrational modes to the vibrational spectrum of strongly hydrogen-bonded heterodimers of carboxylic acids and nitrogen-containing aromatic bases, taking the 7-azaindole--acetic acid and pyridine--acetic acid dimers as examples. Our calculations take into account coupling between the OH stretch and bend modes as well as how both of these modes are affected by lower frequency dimer stretch modes, which modulate the distance between the monomers. Our calculations reproduce the broadness and the double-hump structure of the OH vibrational feature. Where the spectral broadness is primarily caused by the dimer stretch modes strongly modulating the frequency of the OH stretch mode, the double-hump structure results from a Fermi resonance between the out of the plane OH bend and the OH stretch modes.

Structure-function relations and rigidity percolation in the shear properties of articular cartilage.

Among mammalian soft tissues, articular cartilage is particularly interesting because it can endure a lifetime of daily mechanical loading despite having minimal regenerative capacity. This remarkable resilience may be due to the depth-dependent mechanical properties, which have been shown to localize strain and energy dissipation. This paradigm proposes that these properties arise from the depth-dependent collagen fiber orientation. Nevertheless, this structure-function relationship has not yet been quantified. Here, we use confocal elastography, quantitative polarized light microscopy, and Fourier-transform infrared imaging to make same-sample measurements of the depth-dependent shear modulus, collagen fiber organization, and extracellular matrix concentration in neonatal bovine articular cartilage. We find weak correlations between the shear modulus |G(∗)| and both the collagen fiber orientation and polarization. We find a much stronger correlation between |G(∗)| and the concentration of collagen fibers. Interestingly, very small changes in collagen volume fraction vc lead to orders-of-magnitude changes in the modulus with |G(∗)| scaling as (vc - v0)(ξ). Such dependencies are observed in the rheology of other biopolymer networks whose structure exhibits rigidity percolation phase transitions. Along these lines, we propose that the collagen network in articular cartilage is near a percolation threshold that gives rise to these large mechanical variations and localization of strain at the tissue's surface.

Oral health status among 6- and 12-year-old Jordanian schoolchildren.

PURPOSE: No nationwide oral health survey has previously been carried out in Jordan. The aims of the study were to assess the burden of dental caries and gingival health among children aged 6 and 12 years in relation to sociodemographic factors and to ascertain the trend over time in the occurrence of caries and the need for dental care. MATERIALS AND METHODS: A cross-sectional epidemiological survey was carried out which included 2496 children aged 6 years and 2560 children aged 12 years selected by stratified cluster sampling. Children were examined in schools and data comprised information about caries and gingival health status. WHO methodology and criteria were applied. Structured questionnaires were used to collect information about oral hygiene, dental visits, consumption of sugars and parents' level of education. RESULTS: The caries prevalence rates were 76.4% in 6-year-olds and 45.5% in 12-year-olds, and caries experience was 3.3 dmft and 1.1 DMFT, respectively. The prevalence of caries varied significantly by sex and geographical region. In both age groups, children of the social low and middle groups had significantly higher levels of caries experience, more untreated decayed teeth and fewer filled teeth than did children of the upper socioeconomic group. Multivariate regression analysis showed that social class was the most important independent variable for caries. The results from 2005 were compared with similar data collected in the capital, Amman, in 1993. For all social classes, the mean caries experience and the amount of untreated dental caries increased over time. Moreover, 17.7% of 6-year-old children and 49.1% of the 12-year-olds had gingival bleeding. Significant differences in gingival health were found by sex, location, geographical areas and socioeconomic group. CONCLUSION: Oral disease is a significant public health problem in Jordan. Strengthening of the school oral health programme is needed for effective prevention and control of caries and promoting gingival health. A systematic school oral health programme including oral health promotion should be established.

Strengthening of oral health systems: oral health through primary health care.

Around the globe many people are suffering from oral pain and other problems of the mouth or teeth. This public health problem is growing rapidly in developing countries where oral health services are limited. Significant proportions of people are underserved; insufficient oral health care is either due to low availability and accessibility of oral health care or because oral health care is costly. In all countries, the poor and disadvantaged population groups are heavily affected by a high burden of oral disease compared to well-off people. Promotion of oral health and prevention of oral diseases must be provided through financially fair primary health care and public health intervention. Integrated approaches are the most cost-effective and realistic way to close the gap in oral health between rich and poor. The World Health Organization (WHO) Oral Health Programme will work with the newly established WHO Collaborating Centre, Kuwait University, to strengthen the development of appropriate models for primary oral health care.