Phase-Insensitive Scattering of Terahertz Radiation

The nonlinear interaction between Near-Infrared (NIR) and Terahertz pulses is principally investigated as a means for the detection of radiation in the hardly accessible THz spectral region. Most studies have targeted second-order nonlinear processes, given their higher efficiencies, and only a limited number have addressed third-order nonlinear interactions, mainly investigating four-wave mixing in air for broadband THz detection. We have studied the nonlinear interaction between THz and NIR pulses in solid-state media (specifically diamond), and we show how the former can be frequency-shifted up to UV frequencies by the scattering from the nonlinear polarisation induced by the latter. Such UV emission differs from the well-known electric-field-induced second harmonic (EFISH) one, as it is generated via a phase-insensitive scattering, rather than a sum- or difference-frequency four-wave-mixing process

The Dynamical Instability of Static, Spherically Symmetric Solutions in Nonsymmetric Gravitational Theories

We consider the dynamical stability of a class of static, spherically-symmetric solutions of the nonsymmetric gravitational theory. We numerically reproduce the Wyman solution and generate new solutions for the case where the theory has a nontrivial fundamental length scale \mu^{-1}. By considering spherically symmetric perturbations of these solutions we show that the Wyman solutions are generically unstable.Comment: 13 pages, uses amslatex, graphicx and subfigure package

Étude paléolimnologique de l'histoire trophique du lac Saint-Charles, réservoir d'eau potable de la Communauté Urbaine de Québec

Cette étude utilise une approche paléolimnologique pour reconstituer l'histoire trophique du réservoir d'eau potable de la Communauté Urbaine de Québec (CUQ), le lac Saint-Charles. Ce lac manifeste présentement un manque d'oxygène près du fond à la fin de la stratification estivale et hivernale. L'étude révèle des changements dans la communauté diatomifère fossile depuis environ les 150 dernières années. L'événement ayant entraîné le plus de changements biologiques et physico-chimiques dans le bassin est la transformation hydrologique engendrée par la construction d'un barrage en 1934 qui éleva le niveau du lac d'environ 1,5 à 2 mètres. Par conséquent, il y eut des changements dans la structure des communautés de diatomées avec des effets sur le ratio espèces planctoniques / benthiques, sur la paléoproductivité et les caractéristiques physico-chimiques des sédiments suivant cette période. Les assemblages diatomifères indiquent que les conditions mésotrophes se sont maintenues pendant toute la période étudiée. L'analyse du phosphore total dans les sédiments et la reconstitution à partir des diatomées fossiles du phosphore total dans l'eau montrent une légère diminution de la concentration en phosphore avec le temps. Ces observations démontrent qu'il n'y a pas eu d'accélération du processus d'eutrophisation engendrée par les activités humaines. Par contre, l'analyse géochimique des sédiments révèle un apport plus important de métaux depuis la fin du 19e siècle, qui atteint un plateau vers la fin des années 70.This study adopted a combined paleolimnological-limnological approach towards evaluating the trophic history of Lake Saint-Charles, the drinking water reservoir for a population of 305,000 in the Québec City (Canada) region. Our limnological measurements indicate that the lake is currently in a state of advanced mesotrophy. Water column profiles during late summer stratification (September) showed that the bottom waters were anoxic, enriched in phosphorus (up to 17 µg total P L-1) and had a pH almost 2 units lower than the surface waters. Surface phytoplankton concentrations were high at this time of year with Chlorophyll a concentrations of up to 12 µg·L-1. At the end of winter stratification, oxygen concentrations were below saturation at all depths, ranging from 72% immediately under the ice to 4% at the bottom of the water column. This tendency towards eutrophic conditions was offset, however, by a rapid flushing rate (mean hydraulic residence time=23 days). Because there are concerns that the lake has experienced accelerated nutrient enrichment due to increased human activities in its drainage basin, the objectives of our paleolimnological approach were to document the recent trophic history of this lake, to estimate the extent of recent changes in trophic status, and to identify critical periods of past anthropogenic disturbances from the fossils of siliceous algae (diatoms; class Bacillariophyceae) preserved in its sediments. Quantitative estimates of past total phosphorus (TP) concentrations in the water column of Lake Saint-Charles were obtained by applying a diatom-TP reconstruction model developed for 54 lakes located in south-eastern Ontario to fossil diatom assemblages from a 28 cm long sediment core. The timing of changes in the fossil diatom record was estimated by210 Pb dating. The study reveals changes in fossil diatom assemblage composition during the past ca. 150 years, with the most striking biological and physico-chemical changes occurring immediately after 1934. This date coincides with the construction of a dam, which raised the lake water level by 1.5-2 m. This modification was accompanied by significant shifts in diatom community structure, especially in the planktonic/benthic ratio (with increases in planktonic diatoms Cyclotella stelligera and Aulacoseira distans), and by changes in the physico-chemical characteristics of the sediments. Paleoproductivity increased at the same time, but remained more or less stable following conservation efforts between 1950 and 1970 (e.g., construction of a sewage treatment system). The organic matter content of the sediments showed an increase in the order of 20% between 1850 and 1950, after which it remained constant. Fossil diatom community structure indicates that mesotrophic conditions have prevailed during the recent history of Lake Saint-Charles, and that diatoms typical of eutrophic conditions never became established in the lake. The geochemical analysis of phosphorus in the sediments as well as the diatom-inferred quantitative reconstruction of lake water total phosphorus reveals a slight decrease in total phosphorus over time, from close to 17 µg·L- prior to 1887 to about 13 µg·L- 1 in recent times. These observations suggest that Lake Saint-Charles has not experienced significant recent changes in trophic status due to increased human activities in its drainage basin. However, our geochemical analyses show a sharp rise in metal concentrations (especially Fe, Mn, Cu, Pb and Zn), beginning in the late 19th century, reaching a plateau by the late 1970s, which may be attributed to increased atmospheric pollution since the beginning of intense human colonization in the lake's catchment and surrounding areas. This in combination with the advanced mesotrophic status of the lake indicates the ongoing need for careful management of the watershed to prevent further changes in this important urban water resource

Spontaneous reduction of a hydroborane to generate a B-B single bond using a Lewis pair

The ansa‐aminohydroborane 1‐NMe2‐2‐(BH2)C6H4 crystallizes in an unprecedented type of dimer containing a B−H bond activated by one FLP moiety. Upon mild heating and without the use of any catalyst, this molecule liberates one equivalent of hydrogen to generate a diborane molecule. The synthesis and structural characterization of these new compounds, as well as the kinetic monitoring of the reaction and the DFT investigation of its mechanism, are reported

Feasibility of a randomised trial of a continuing medical education program in shared decision-making on the use of antibiotics for acute respiratory infections in primary care: the DECISION+ pilot trial

Abstract Background The misuse and limited effectiveness of antibiotics for acute respiratory infections (ARIs) are well documented, and current approaches targeting physicians or patients to improve appropriate use have had limited effect. Shared decision-making could be a promising strategy to improve appropriate antibiotic use for ARIs, but very little is known about its implementation processes and outcomes in clinical settings. In this matter, pilot studies have played a key role in health science research over the past years in providing information for the planning, justification, and/or refinement of larger studies. The objective of our study was to assess the feasibility and acceptability of the study design, procedures, and intervention of the DECISION+ program, a continuing medical education program in shared decision-making among family physicians and their patients on the optimal use of antibiotics for treating ARIs in primary care. Methods A pilot clustered randomised trial was conducted. Family medicine groups (FMGs) were randomly assigned, to either the DECISION+ program, which included three 3-hour workshops over a four- to six-month period, or a control group that had a delayed exposure to the program. Results Among 21 FMGs contacted, 5 (24%) agreed to participate in the pilot study. A total of 39 family physicians (18 in the two experimental and 21 in the three control FMGs) and their 544 patients consulting for an ARI were recruited. The proportion of recruited family physicians who participated in all three workshops was 46% (50% for the experimental group and 43% for the control group), and the overall mean level of satisfaction regarding the workshops was 94%. Conclusions This trial, while aiming to demonstrate the feasibility and acceptability of conducting a larger study, has identified important opportunities for improving the design of a definitive trial. This pilot trial is informative for researchers and clinicians interested in designing and/or conducting studies with FMGs regarding training of physicians in shared decision-making. Trial Registration Clinicaltrials.Gov NCT0035431

Retrieval of publications addressing shared decision making: an evaluation of full-text searches on medical journal websites.

BACKGROUND: Full-text searches of articles increase the recall, defined by the proportion of relevant publications that are retrieved. However, this method is rarely used in medical research due to resource constraints. For the purpose of a systematic review of publications addressing shared decision making, a full-text search method was required to retrieve publications where shared decision making does not appear in the title or abstract. OBJECTIVE: The objective of our study was to assess the efficiency and reliability of full-text searches in major medical journals for identifying shared decision making publications. METHODS: A full-text search was performed on the websites of 15 high-impact journals in general internal medicine to look up publications of any type from 1996-2011 containing the phrase "shared decision making". The search method was compared with a PubMed search of titles and abstracts only. The full-text search was further validated by requesting all publications from the same time period from the individual journal publishers and searching through the collected dataset. RESULTS: The full-text search for "shared decision making" on journal websites identified 1286 publications in 15 journals compared to 119 through the PubMed search. The search within the publisher-provided publications of 6 journals identified 613 publications compared to 646 with the full-text search on the respective journal websites. The concordance rate was 94.3% between both full-text searches. CONCLUSIONS: Full-text searching on medical journal websites is an efficient and reliable way to identify relevant articles in the field of shared decision making for review or other purposes. It may be more widely used in biomedical research in other fields in the future, with the collaboration of publishers and journals toward open-access data

Geodesic and Path Motion in the Nonsymmetric Gravitational Theory

We study the problem of test-particle motion in the Nonsymmetric Gravitational Theory (NGT) assuming the four-velocity of the particle is parallel-transported along the trajectory. The predicted motion is studied on a static, spherically symmetric background field, with particular attention paid to radial and circular motions. Interestingly, it is found that the proper time taken to travel between any two non-zero radial positions is finite. It is also found that circular orbits can be supported at lower radii than in General Relativity for certain forms of motion. We present three interactions which could be used as alternate methods for coupling a test-particle to the antisymmetric components of the NGT field. One of these takes the form of a Yukawa force in the weak-field limit of a static, spherically symmetric field, which could lead to interesting phenomenology.Comment: 17 pages, REVTeX 3.0 with amssymb.st

Publication trends of shared decision making in 15 high impact medical journals: a full-text review with bibliometric analysis.

BACKGROUND: Shared Decision Making (SDM) is increasingly advocated as a model for medical decision making. However, there is still low use of SDM in clinical practice. High impact factor journals might represent an efficient way for its dissemination. We aimed to identify and characterize publication trends of SDM in 15 high impact medical journals. METHODS: We selected the 15 general and internal medicine journals with the highest impact factor publishing original articles, letters and editorials. We retrieved publications from 1996 to 2011 through the full-text search function on each journal website and abstracted bibliometric data. We included publications of any type containing the phrase "shared decision making" or five other variants in their abstract or full text. These were referred to as SDM publications. A polynomial Poisson regression model with logarithmic link function was used to assess the evolution across the period of the number of SDM publications according to publication characteristics. RESULTS: We identified 1285 SDM publications out of 229,179 publications in 15 journals from 1996 to 2011. The absolute number of SDM publications by journal ranged from 2 to 273 over 16 years. SDM publications increased both in absolute and relative numbers per year, from 46 (0.32% relative to all publications from the 15 journals) in 1996 to 165 (1.17%) in 2011. This growth was exponential (P < 0.01). We found fewer research publications (465, 36.2% of all SDM publications) than non-research publications, which included non-systematic reviews, letters, and editorials. The increase of research publications across time was linear. Full-text search retrieved ten times more SDM publications than a similar PubMed search (1285 vs. 119 respectively). CONCLUSION: This review in full-text showed that SDM publications increased exponentially in major medical journals from 1996 to 2011. This growth might reflect an increased dissemination of the SDM concept to the medical community

Generation of broad XUV continuous high harmonic spectra and isolated attosecond pulses with intense mid-infrared lasers

We present experimental results showing the appearance of a near-continuum in the high-order harmonic generation (HHG) spectra of atomic and molecular species as the driving laser intensity of an infrared pulse increases. Detailed macroscopic simulations reveal that these near-continuum spectra are capable of producing IAPs in the far field if a proper spatial filter is applied. Further, our simulations show that the near-continuum spectra and the IAPs are a product of strong temporal and spatial reshaping (blue shift and defocusing) of the driving field. This offers a possibility of producing IAPs with a broad range of photon energy, including plateau harmonics, by mid-IR laser pulses even without carrier-envelope phase stabilization.Comment: 7 pages, 5 figures, submitted to J.Phys. B (Oct 2011