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result(s) for
"Praz, C."
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Determination and climatology of the planetary boundary layer height above the Swiss plateau by in situ and remote sensing measurements as well as by the COSMO-2 model
by
Kaufmann, P.
,
Calpini, B.
,
Ruffieux, D.
in
Analysis
,
Atmospheric composition
,
Dynamic meteorology
2014
The planetary boundary layer (PBL) height is a key parameter in air quality control and pollutant dispersion. The PBL height cannot, however, be directly measured, and its estimation relies on the analysis of the vertical profiles of the temperature, turbulence or the atmospheric composition. An operational PBL height detection method including several remote sensing instruments (wind profiler, Raman lidar, microwave radiometer) and several algorithms (Parcel and bulk Richardson number methods, surface-based temperature inversion, aerosol or humidity gradient analysis) was developed and tested with 1 year of measurements, which allows the methods to be validated against radio sounding measurements. The microwave radiometer provides convective boundary layer heights in good agreement with the radio sounding (RS) (median bias < 25 m, R2 > 0.70) and allows the analysis of the diurnal variation of the PBL height due to its high temporal resolution. The Raman lidar also leads to a good agreement with RS, whereas the wind profiler yields some more dispersed results mostly due to false attribution problems. A comparison with the numerical weather prediction model COSMO-2 has shown a general overestimation of the model PBL height by some hundreds to thousand meters. Finally the seasonal cycles of the daytime and nighttime PBL heights are discussed for each instrument and each detection algorithm for two stations on the Swiss plateau.
Journal Article
Elevated rates of dietary generalization in eusocial lineages of the secondarily herbivorous bees
2023
Background
Within the Hymenoptera, bees are notable for their relationship with flowering plants, being almost entirely dependent on plant pollen and nectar. Though functionally herbivorous, as a result of their role as pollinators, bees have received comparatively little attention as models for insect herbivory. Bees often display dietary specialization, but quantitative comparison against other herbivorous insects has not previously been conducted.
Results
In the most comprehensive analysis to date for 860 bee species, dietary specialization amounted to 50.1% of studied species collecting pollen from between 1 and 2 botanical families with a relatively long tail of dietary generalists, with 11.1% of species collecting from more than 10 botanical families. This distribution deviated from the truncated Pareto distribution of dietary breadth seen in other herbivorous insect lineages. However, this deviation was predominantly due to eusocial bee lineages, which show a range of dietary breadths that conformed to a normal distribution, while solitary bees show a typical truncated distribution not strongly different from other herbivorous insects. We hypothesize that the relatively low level of dietary specialization in bees as a whole reflects the relaxation of the constraints typically observed in herbivorous insects with a comparatively reduced importance of plant chemistry and comparatively increased importance of phenology and foraging efficiency. The long flight periods of eusocial bees that are necessary to allow overlapping generations both allows and necessitates the use of multiple flowering resources, whereas solitary bees with short flight periods have more limited access to varied resources within a constrained activity period.
Conclusions
Collectively, solitary bees show slightly lower specialization compared to other herbivorous insects, possibly due to their balanced relationship with plants, rather than direct antagonism such as seen in the direct consumption of plant tissues. An additional factor may be the mediocre diversity of bees at low latitudes combined with low levels of dietary specialization, whereas these areas typically display a high rate of specialization by herbivorous insects in general. Though the most important factors structuring dietary specialization in bees appear to differ from many other herbivorous insects, solitary bees show a surprisingly similar overall pattern of dietary specialization.
Journal Article
Measurement of time-dependent CP asymmetries in$${B}^{0}\\to {K}_{\\text{S}}^{0}{\\pi }^{+}{\\pi }^{-}\\gamma $$decays at Belle and Belle II
2026
We present a measurement of the time-dependent CP asymmetry in$${B}^{0}\\to {K}_{\\text{S}}^{0}{\\pi }^{+}{\\pi }^{-}\\gamma $$decays using a data set of 365 fb − 1 recorded by the Belle II experiment and the final data set of 711 fb − 1 recorded by the Belle experiment at the Υ(4S) resonance. The direct and mixing-induced time-dependent CP violation parameters C and S are determined along with two additional quantities, S + and S − , defined in the two halves of the$${m}^{2}\\left({K}_{\\text{S}}^{0}{\\pi }^{+}\\right)-{m}^{2}\\left({K}_{\\text{S}}^{0}{\\pi }^{-}\\right)$$plane. The measured values are C = − 0 . 17 ± 0 . 09 ± 0 . 04, S = − 0 . 29 ± 0 . 11 ± 0 . 05, S + = −0 . 57 ± 0 . 23 ± 0 . 10 and S − = 0 . 31 ± 0 . 24 ± 0 . 05, where the first uncertainty is statistical and the second systematic.
Journal Article
Measurements of the branching fractions of$$ {\\Xi}_c^0\\to {\\Xi}^0{\\pi}^0 $$ ,$$ {\\Xi}_c^0\\to {\\Xi}^0\\eta $$ , and$$ {\\Xi}_c^0\\to {\\Xi}^0{\\eta}^{\\prime } $$and asymmetry parameter of$$ {\\Xi}_c^0\\to {\\Xi}^0{\\pi}^0
2024
We present a study of$$ {\\Xi}_c^0\\to {\\Xi}^0{\\pi}^0 $$Ξ c 0 → Ξ 0 π 0 ,$$ {\\Xi}_c^0\\to {\\Xi}^0\\eta $$Ξ c 0 → Ξ 0 η , and$$ {\\Xi}_c^0\\to {\\Xi}^0{\\eta}^{\\prime } $$Ξ c 0 → Ξ 0 η ′ decays using the Belle and Belle II data samples, which have integrated luminosities of 980 fb − 1 and 426 fb − 1 , respectively. We measure the following relative branching fractions$$ {\\displaystyle \\begin{array}{c}\\mathcal{B}\\left({\\Xi}_c^0\\to {\\Xi}^0{\\pi}^0\\right)/\\mathcal{B}\\left({\\Xi}_c^0\\to {\\Xi}^{-}{\\pi}^{+}\\right)=0.48\\pm 0.02\\left(\\textrm{stat}\\right)\\pm 0.03\\left(\\textrm{syst}\\right),\\\ {}\\mathcal{B}\\left({\\Xi}_c^0\\to {\\Xi}^0\\eta \\right)/\\mathcal{B}\\left({\\Xi}_c^0\\to {\\Xi}^{-}{\\pi}^{+}\\right)=0.11\\pm 0.01\\left(\\textrm{stat}\\right)\\pm 0.01\\left(\\textrm{syst}\\right),\\\ {}\\mathcal{B}\\left({\\Xi}_c^0\\to {\\Xi}^0{\\eta}^{\\prime}\\right)/\\mathcal{B}\\left({\\Xi}_c^0\\to {\\Xi}^{-}{\\pi}^{+}\\right)=0.08\\pm 0.02\\left(\\textrm{stat}\\right)\\pm 0.01\\left(\\textrm{syst}\\right)\\end{array}} $$B Ξ c 0 → Ξ 0 π 0 / B Ξ c 0 → Ξ − π + = 0.48 ± 0.02 stat ± 0.03 syst , B Ξ c 0 → Ξ 0 η / B Ξ c 0 → Ξ − π + = 0.11 ± 0.01 stat ± 0.01 syst , B Ξ c 0 → Ξ 0 η ′ / B Ξ c 0 → Ξ − π + = 0.08 ± 0.02 stat ± 0.01 syst for the first time, where the uncertainties are statistical (stat) and systematic (syst). By multiplying by the branching fraction of the normalization mode,$$ \\mathcal{B}\\left({\\Xi}_c^0\\to {\\Xi}^{-}{\\pi}^{+}\\right) $$B Ξ c 0 → Ξ − π + , we obtain the following absolute branching fraction results$$ {\\displaystyle \\begin{array}{c}\\mathcal{B}\\left({\\Xi}_c^0\\to {\\Xi}^0{\\pi}^0\\right)=\\left(6.9\\pm 0.3\\left(\\textrm{stat}\\right)\\pm 0.5\\left(\\textrm{syst}\\right)\\pm 1.3\\left(\\operatorname{norm}\\right)\\right)\\times {10}^{-3},\\\ {}\\mathcal{B}\\left({\\Xi}_c^0\\to {\\Xi}^0\\eta \\right)=\\left(1.6\\pm 0.2\\left(\\textrm{stat}\\right)\\pm 0.2\\left(\\textrm{syst}\\right)\\pm 0.3\\left(\\operatorname{norm}\\right)\\right)\\times {10}^{-3},\\\ {}\\mathcal{B}\\left({\\varXi}_c^0\\to {\\Xi}^0{\\eta}^{\\prime}\\right)=\\left(1.2\\pm 0.3\\left(\\textrm{stat}\\right)\\pm 0.1\\left(\\textrm{syst}\\right)\\pm 0.2\\left(\\operatorname{norm}\\right)\\right)\\times {10}^{-3},\\end{array}} $$B Ξ c 0 → Ξ 0 π 0 = 6.9 ± 0.3 stat ± 0.5 syst ± 1.3 norm × 10 − 3 , B Ξ c 0 → Ξ 0 η = 1.6 ± 0.2 stat ± 0.2 syst ± 0.3 norm × 10 − 3 , B Ξ c 0 → Ξ 0 η ′ = 1.2 ± 0.3 stat ± 0.1 syst ± 0.2 norm × 10 − 3 , where the third uncertainties are from$$ \\mathcal{B}\\left({\\Xi}_c^0\\to {\\Xi}^{-}{\\pi}^{+}\\right) $$B Ξ c 0 → Ξ − π + . The asymmetry parameter for$$ {\\Xi}_c^0\\to {\\Xi}^0{\\pi}^0 $$Ξ c 0 → Ξ 0 π 0 is measured to be$$ \\alpha \\left({\\Xi}_c^0\\to {\\Xi}^0{\\pi}^0\\right)=-0.90\\pm 0.15\\left(\\textrm{stat}\\right)\\pm 0.23\\left(\\textrm{syst}\\right) $$α Ξ c 0 → Ξ 0 π 0 = − 0.90 ± 0.15 stat ± 0.23 syst .
Journal Article
Working Together and Being Physically Active Are Not Enough to Advise Uniformly and Adequately Low Back Pain Patients: A Cross-Sectional Study
2018
The profession of the health-care providers (HCPs) influences their recommendations to the patients. Conversely, interdisciplinarity seeks to challenge such differences, so that the patient receives one single and consistent therapeutic message. Some studies also suggest associations between HCPs life habits and recommendations. Our hypotheses were (1) that despite interdisciplinary work, the profession remains a predictor of recommendations and (2) that HCPs who are more physically active recommend more activity. Three clinical vignettes were presented to a group of experts of low back pain (LBP) (guidelines), and 20 physicians, 22 physiotherapists, and 23 nurses to assess how they evaluate the symptoms and pathologies of LBP patients and how much work and physical activity they recommend. Physical activity was assessed with accelerometers and questionnaires. Some interprofessional differences remained present within an interdisciplinary team. The nurses were more restrictive and further away from the guidelines. The physicians were the most in line with them. The physiotherapists recommend as much physical activity, but less work activity than the physicians. The level of physical activity of the HCPs is not associated with their recommendations. To ensure a clear and unique message, educational actions may be undertaken to promote the biopsychosocial model and clarify the guidelines.
Journal Article
Specialized Bees Fail to Develop on Non-host Pollen: Do Plants Chemically Protect Their Pollen?
by
Praz, Christophe J.
,
Müller, Andreas
,
Dorn, Silvia
in
Adaptation, Physiological
,
Animal and plant ecology
,
Animal, plant and microbial ecology
2008
Bees require large amounts of pollen for their own reproduction. While several morphological flower traits are known to have evolved to protect plants against excessive pollen harvesting by bees, little is known on how selection to minimize pollen loss acts on the chemical composition of pollen. In this study, we traced the larval development of four solitary bee species, each specialized on a different pollen source, when reared on non-host pollen by transferring unhatched eggs of one species onto the pollen provisions of another species. Pollen diets of Asteraceae and Ranunculus (Ranunculaceae) proved to be inadequate for all bee species tested except those specialized on these plants. Further, pollen of Sinapis (Brassicaceae) and Echium (Boraginaceae) failed to support larval development in one bee species specialized on Campanula (Campanulaceae). Our results strongly suggest that pollen of these four taxonomic groups possess protective properties that hamper digestion and thus challenge the general view of pollen as an easy-to-use protein source for flower visitors.
Journal Article
Solid hydrometeor classification and riming degree estimation from pictures collected with a Multi-Angle Snowflake Camera
by
Praz, Christophe
,
Berne, Alexis
,
Roulet, Yves-Alain
in
Accuracy
,
Algorithms
,
Atmospheric water
2017
A new method to automatically classify solid hydrometeors based on Multi-Angle Snowflake Camera (MASC) images is presented. For each individual image, the method relies on the calculation of a set of geometric and texture-based descriptors to simultaneously identify the hydrometeor type (among six predefined classes), estimate the degree of riming and detect melting snow. The classification tasks are achieved by means of a regularized multinomial logistic regression (MLR) model trained over more than 3000 MASC images manually labeled by visual inspection. In a second step, the probabilistic information provided by the MLR is weighed on the three stereoscopic views of the MASC in order to assign a unique label to each hydrometeor. The accuracy and robustness of the proposed algorithm is evaluated on data collected in the Swiss Alps and in Antarctica. The algorithm achieves high performance, with a hydrometeor-type classification accuracy and Heidke skill score of 95 % and 0.93, respectively. The degree of riming is evaluated by introducing a riming index ranging between zero (no riming) and one (graupel) and characterized by a probable error of 5.5 %. A validation study is conducted through a comparison with an existing classification method based on two-dimensional video disdrometer (2DVD) data and shows that the two methods are consistent.
Journal Article
Identification of blowing snow particles in images from a Multi-Angle Snowflake Camera
2020
A new method to automatically discriminate between hydrometeors and blowing snow particles on Multi-Angle Snowflake Camera (MASC) images is introduced. The method uses four selected descriptors related to the image frequency, the number of particles detected per image, and their size and geometry to classify each individual image. The classification task is achieved with a two-component Gaussian mixture model fitted on a subset of representative images of each class from field campaigns in Antarctica and Davos, Switzerland. The performance is evaluated by labeling the subset of images on which the model was fitted. An overall accuracy and a Cohen kappa score of 99.4 % and 98.8 %, respectively, are achieved. In a second step, the probabilistic information is used to flag images composed of a mix of blowing snow particles and hydrometeors, which turns out to occur frequently. The percentage of images belonging to each class from an entire austral summer in Antarctica and during a winter in Davos, respectively, is presented. The capability to distinguish precipitation, blowing snow and a mix of those in MASC images is highly relevant to disentangle the complex interactions between wind, snowflakes and snowpack close to the surface.
Journal Article
Seedling survival and growth of three ectomycorrhizal caesalpiniaceous tree species in a Central African rain forest
2006
Tree recruitment is determined in part by the survivorship and growth of seedlings. Two seedling cohorts of the three most abundant caesalpiniaceous species forming groves at Korup, Cameroon, were followed from 1995/1997 to 2002, to investigate why Microberlinia bisulcata, the most abundant species, currently has very few recruits compared with Tetraberlinia korupensis and T. bifoliolata. Numbers of seedlings dying, and the heights and leaf numbers of survivors, were recorded on 30 occasions. Survivorship after 2.5 y was 30% for M. bisulcata and 59% for the similar Tetraberlinia spp. together. After 7 y the corresponding values were 4 and 21%. Growth of all species was slow for the first 4 y; but survivors of T. korupensis became 63% taller, as the other species stagnated, by 7 y. The poor recruitment of M. bisulcata was the result of its very low seedling survival. Within species, the tallest seedlings of M. bisulcata and T. bifoliolata, but medium-height ones of T. korupensis, survived longest. This was likely due to higher root allocation in T. korupensis. Seedling dynamics of M. bisulcata and T. korupensis over 7 y accorded well with relative abundances of adult trees; T. bifoliolata is predicted to recruit later.
Journal Article
Observations of the singly Cabibbo-suppressed decays Ξc+→pKS0, Ξc+→Λπ+, and Ξc+→Σ0π+ at Belle and Belle II
by
Madaan, C.
,
Althubiti, N.
,
Borah, J.
in
Charged particles
,
Classical and Quantum Gravitation
,
Elementary Particles
2025
A
bstract
Using data samples of 983.0 fb
−
1
and 427.9 fb
−
1
accumulated with the Belle and Belle II detectors operating at the KEKB and SuperKEKB asymmetric-energy
e
+
e
−
colliders, singly Cabibbo-suppressed decays
Ξ
c
+
→
p
K
S
0
,
Ξ
c
+
→
Λ
π
+
, and
Ξ
c
+
→
Σ
0
π
+
are observed for the first time. The ratios of branching fractions of
Ξ
c
+
→
p
K
S
0
,
Ξ
c
+
→
Λ
π
+
, and
Ξ
c
+
→
Σ
0
π
+
relative to that of
Ξ
c
+
→
Ξ
−
π
+
π
+
are measured to be
B
Ξ
c
+
→
p
K
S
0
B
Ξ
c
+
→
Ξ
−
π
+
π
+
=
2.47
±
0.16
±
0.07
%
,
B
Ξ
c
+
→
Λ
π
+
B
Ξ
c
+
→
Ξ
−
π
+
π
+
=
1.56
±
0.14
±
0.09
%
,
B
Ξ
c
+
→
Σ
0
π
+
B
Ξ
c
+
→
Ξ
−
π
+
π
+
=
4.13
±
0.26
±
0.22
%
.
Multiplying these values by the branching fraction of the normalization channel,
B
Ξ
c
+
→
Ξ
−
π
+
π
+
=
2.9
±
1.3
%
, the absolute branching fractions are determined to be
B
Ξ
c
+
→
p
K
S
0
=
7.16
±
0.46
±
0.20
±
3.21
×
10
−
4
,
B
Ξ
c
+
→
Λ
π
+
=
4.52
±
0.41
±
0.26
±
2.03
×
10
−
4
,
B
Ξ
c
+
→
Σ
0
π
+
=
1.20
±
0.08
±
0.07
±
0.54
×
10
−
3
.
The first and second uncertainties above are statistical and systematic, respectively, while the third ones arise from the uncertainty in
B
Ξ
c
+
→
Ξ
−
π
+
π
+
.
Journal Article