The concentrations of the rare earth elements (REE) in surface waters and sediments, when normalized on an element-by-element basis to one of several rock standards and plotted versus atomic number, yield curves that ...The concentrations of the rare earth elements (REE) in surface waters and sediments, when normalized on an element-by-element basis to one of several rock standards and plotted versus atomic number, yield curves that reveal their partitioning between different sediment fractions and the sources of those fractions, for example, between terrestrial-derived lithogenous debris and seawater-derived biogenous detritus and hydrogenous metal oxides. The REE of ancient sediments support their partitioning into these same fractions and further contribute to the identification of the redox geochemistry of the sea water in which the sediments accumulated. The normalized curves of the REE that have been examined in several South American wine varietals can be interpreted to reflect the lithology of the bedrock on which the vines may have been grown, suggesting limited fractionation during soil development.展开更多
The knowledge of Martian geology has increased enormously in the last 40 yr. Several missions orbiting or roving Mars have revolutionized our understanding of its evolution and geological features, which in several wa...The knowledge of Martian geology has increased enormously in the last 40 yr. Several missions orbiting or roving Mars have revolutionized our understanding of its evolution and geological features, which in several ways are similar to Earth, but are extremely different in many respects. The impressive dichotomy between the two Martian hemispheres is most likely linked to its impact cratering history, rather than internal dynamics such as on Earth. Mars＇ volcanism has been extensive, very longlived and rather constant in its setting. Water was available in large quantities in the distant past of Mars, when a magnetic field and more vigorous tectonics were active. Exogenic forces have been shaping Martian landscapes and have led to a plethora of landscapes shaped by wind, water and ice. Mars＇ dynamical behavior continues, with its climatic variation affecting climate and geology until very recent times. This paper tries to summarize major highlights in Mars＇ Geology, and points to deeper and more extensive sources of important scientific contributions and future exploration.展开更多
In this article,we consider a fully nonlinear partial differential equation which can be expressed as a sum of two Monge-Ampere operators acting in different two-dimensional coordinate sections.This equation is ellipt...In this article,we consider a fully nonlinear partial differential equation which can be expressed as a sum of two Monge-Ampere operators acting in different two-dimensional coordinate sections.This equation is elliptic,for example,in the class of convex functions.We show that the notion of Monge-Ampere measures and Aleksandrov generalized solutions extends to this equation,subject to a weaker notion of convexity which we call bi-planar convexity.While the equation is also elliptic in the class of bi-planar convex functions,the contrary is not necessarily true.This is a substantial difference compared to the classical Monge-Ampere equation where ellipticity and convexity coincide.We provide explicit counter-examples:classical solutions to the bi-planar equation that satisfy the ellipticity condition but are not generalized solutions in the sense introduced.We conclude that the concept of generalized solutions based on convexity arguments is not a natural setting for the bi-planar equation.展开更多
Humans are exposed to radiofrequency electromagnetic fields （RFEMF） from various sources （e.g., mobile and cordless phones, base stations, TV and radio transmitters, wifi adapters）. So far, there is no evidence th...Humans are exposed to radiofrequency electromagnetic fields （RFEMF） from various sources （e.g., mobile and cordless phones, base stations, TV and radio transmitters, wifi adapters）. So far, there is no evidence that would indicate that RFEMF exposure is causing adverse health effects with respect to cancer, sleep disorder, headache, etc. Some results of in vitro and in vivo experiments revealed negative effects on male fertility. When looking at those studies in detail, many problems are identified with respect to correct dosimetry and proper experimental design. This field of research is notoriously difficult for various reasons, and experiments should be planned and performed with experts from the respective areas.展开更多
In steel continuous casting(CC),the choice of the appropriate speed at which the slab is cast can be influenced by many different factors and phenomena.While the slab thickness seems to have the biggest impact,other f...In steel continuous casting(CC),the choice of the appropriate speed at which the slab is cast can be influenced by many different factors and phenomena.While the slab thickness seems to have the biggest impact,other features like the slab width have been consistently overlooked.In fact,the slab width practically limits the casting speed via the mass flow constraint which governs the input and output balance at the tundish.Here,we present a case study that aims at analyzing steel production data from the perspective of casting speed constraints.By studying the speed fluctuations of an industrial CC machine,we identify a strategic regime change toward a stricter consideration of the mass flow constraint.The regime change manifests itself in a significant increase in the correlation between the actual casting speed and the maximal speed associated with the mass flow constraint.On the surface,taking greater account of the input and output balance at the tundish has reduced the productivity of the continuous caster;however,one can argue that the lessened yield is compensated by a diminished risk of eventual slab breaking.From the perspective of this trade-off,we establish a visualization technique that enables us to pinpoint the boundary beyond which one strategic regime becomes economically more advantageous than the other.展开更多
Acquisition and registration of terrestrial 3D laser scans is a fundamental task in mapping and modeling of cities in three dimensions. To automate this task marker-flee registration methods are required. Based on the...Acquisition and registration of terrestrial 3D laser scans is a fundamental task in mapping and modeling of cities in three dimensions. To automate this task marker-flee registration methods are required. Based on the existence of skyline features, this paper proposes a novel method. The skyline features are extracted from panoramic 3D scans and encoded as strings enabling the use of string matching for merging the scans. Initial results of the proposed method in the old city center of Bremen are presented.展开更多
Despite serotonin’s and FMRF-amide’s wide distribution in the nervous system of invertebrates and their importance as neurotransmitters, the exact roles they play in neuronal networks leaves many questions. We mappe...Despite serotonin’s and FMRF-amide’s wide distribution in the nervous system of invertebrates and their importance as neurotransmitters, the exact roles they play in neuronal networks leaves many questions. We mapped the presence of serotonin and FMRF-amide-immunoreactivity in the central nervous system and eyes of the pond snail Lymnaea stagnalis and interpreted the results in connection with our earlier findings on the central projections of different peripheral nerves. Since the chemical nature of the intercellular connections in the retina of Lymnaea stagnalis is still largely unknown, we paid special attention to clarifying the role of serotonin and FMRF-amide in the visual system of this snail and compared our findings with those reported from other species. At least one serotonin-and one FMRF-amidergic fibre were labeled in each optic nerve, and since no cell bodies in the eye showed immunoreactivity to these neurotransmitters, we believe that efferent fibres with somata located in the central ganglia branch at the base of the eye and probably release 5HT and FMRF-amide as neuro-hormones. Double labelling revealed retrograde transport of neurobiotin through the optic nerve, allowing us to conclude that the central pathways and serotonin-and FMRF-amideimmunoreactive cells and fibres have different locations in the CNS in Lymnaea stagnalis. The chemical nature of the fibres, which connect the two eyes in Lymnaea stagnalis, is neither serotoninergic nor FMRF-amidergic.展开更多
Afferent and efferent neural elements of the retina and central ganglia in the freshwater snail Planorbarius corneus were labelled using retrograde transport of neurobiotin through the optic nerve.Axons of at least so...Afferent and efferent neural elements of the retina and central ganglia in the freshwater snail Planorbarius corneus were labelled using retrograde transport of neurobiotin through the optic nerve.Axons of at least some photoreceptor cells become direct contributors to the optic nerve as no synaptic junctions could be detected.The processes enter the cerebral ganglion and form a dense bundle of thin afferent fibres,the so-called optical neuropil.Efferent neurons were revealed in all ganglia,except the buccal ones.Some of the ascending axons branch in the cerebral ganglia,cross the cerebro-cerebral commissure,reach the contralateral eye and form arborizations in the eye cup.Some efferent neurons send axons to different peripheral nerves as well：n.n.intestinalis,pallialis dexter,pallialis sinister internus et externus.Serotonin-and FMRF-amide-ergic fibres were revealed in the optic nerve.These fibres belong to those central neurons which send their axons to the ipsilateral eye only.They form abundant varicoses in the eye cup and nuclear layer of the retina,and possibly help to regulate retinal sensitivity to light.展开更多
Despite serotonin’s and FMRF-amide’s wide distribution in the nervous system of invertebrates and their importance as neurotransmitters,the exact roles they play in neuronal networks leaves many questions.We mapped ...Despite serotonin’s and FMRF-amide’s wide distribution in the nervous system of invertebrates and their importance as neurotransmitters,the exact roles they play in neuronal networks leaves many questions.We mapped the presence of serotonin and FMRF-amide-immunoreactivity in the central nervous system and eyes of the pond snail Lymnaea stagnalis and interpreted the results in connection with our earlier findings on the central projections of different peripheral nerves.Since the chemical nature of the intercellular connections in the retina of L.stagnalis is still largely unknown,we paid special attention to clarifying the role of serotonin and FMRF-amide in the visual system of this snail and compared our findings with those reported from other species.At least one serotonin-and one FMRF-amidergic fibre were labeled in each optic nerve,and since no cell bodies in the eye showed immunoreactivity to these neurotransmitters,we believe that efferent fibres with somata located in the central ganglia branch at the base of the eye and probably release 5HT and FMRF-amide as neuro-hormones.Double labelling revealed retrograde transport of neurobiotin through the optic nerve,allowing us to conclude that the central pathways and serotonin-and FMRF-amide-immunoreactive cells and fibres have different locations in the CNS in L.stagnalis.The chemical nature of the fibres,which connect the two eyes in L.stagnalis,is neither serotoninergic nor FMRF-amidergic.展开更多
For 20 years the so-called ＂sperm crisis＂ caused unrest among the public as well as the scientific community. Studies precipitated by this virtual crisis have refuted its existence, but have also illuminated hithert...For 20 years the so-called ＂sperm crisis＂ caused unrest among the public as well as the scientific community. Studies precipitated by this virtual crisis have refuted its existence, but have also illuminated hitherto neglected aspects of male reproductive function and indicated a need for prospective, long-term monitoring systems.展开更多
Typically, a Lewis acid and a Lewis base can react with each other and form a classical Lewis adduct. The neutralization reaction can however be prevented by ligating the acid and base with bulky substituents and the ...Typically, a Lewis acid and a Lewis base can react with each other and form a classical Lewis adduct. The neutralization reaction can however be prevented by ligating the acid and base with bulky substituents and the resulting complex is known as a "frustrated Lewis pair"(FLP). Since the Lewis acid and base reactivity remains in the formed complex, FLPs can display interesting chemical activities, with promising applications in catalysis. For example, FLPs were shown to function as the first metal-free catalyst for molecular hydrogen activation. This, and other recent applications of FLPs, have opened a new thriving research field. In this short-review, we recapitulate the computational and experimental studies of the H_2 activation by FLPs. We discuss the thus-far uncovered mechanistic aspects, including pre-organization of FLPs,the reaction paths for the activation, the polarization of He H bond and other factors affecting the reactivity. We aim to provide a rather complete mechanistic picture of the H_2 activation by FLPs, which has been under debate for decades since the first discovery of FLPs. This review is meant as a starting point for future studies and a guideline for industrial applications.展开更多
An efficient chlorination reaction of in situ generated(β-diazo-α,α-difluoroethyl)phosphonates has been achieved with hydrochloric acid as a chlorine source under mild and operationally convenient conditions.The re...An efficient chlorination reaction of in situ generated(β-diazo-α,α-difluoroethyl)phosphonates has been achieved with hydrochloric acid as a chlorine source under mild and operationally convenient conditions.The reaction does not need any catalyst and tolerates a wide scope of substrates,which affords the(β-chlorodifluoroethyl)phosphonate products in good to excellent yields.This reaction represents the first example of the halogenation of difluoroalkyl diazo compounds,and also provides an easy way for the synthesis of difluoromethylenephosphonate-containing compounds.展开更多
Background: The opinion of physicians clearly counts in prioritizing health care, but there is little information on the rationales underlying treatment decisions and whether these rationales are accepted by patients....Background: The opinion of physicians clearly counts in prioritizing health care, but there is little information on the rationales underlying treatment decisions and whether these rationales are accepted by patients. Objective: To compare physicians and patients regarding their understanding and use of therapeutic benefit and treatment costs as criteria for prioritizing health care. Methods: Seven physicians and twelve patients were purposefully selected to yield a heterogeneous sample. Participants were interviewed face-to-face, following a semi-structured topic guide comprising three scenarios that focused on interventions with low or unproven therapeutic benefit and high costs, respectively. For data analysis we used qualitative content analysis. Results: We found that patients and physicians differed in their understanding of therapeutic benefit, their expectations of what medicine can do and their use of costs as criteria for prioritizing health care. Physicians were less likely to assess a certain intervention as effec tive, and they less often accepted upper funding limits in health care. Unlike the physicians, patients raised non-medical aspects in decision making such as the patient’s consent and social inequalities. Conclusions: The revealed differences point toward the necessity to strengthen the doctor-patient communication, to improve information for patients about the possibilities and limits of health care and to gain a deeper understanding of their attitudes, wishes and concerns to reach an agreement by physicians and patients on the treatment to be implemented.展开更多
A highly efficient catalyst of graphene-supported mixed-valent Mn_(16)-containing polyoxometalate is reported here by electrochemical strategy. The modified electrode with the catalyst exhibits an excellent electrocat...A highly efficient catalyst of graphene-supported mixed-valent Mn_(16)-containing polyoxometalate is reported here by electrochemical strategy. The modified electrode with the catalyst exhibits an excellent electrocatalytic performance for water oxidation, which will contribute to the development of highly efficient catalysts for oxygen evolution.展开更多
Using the Health Action Process Approach (HAPA) as a theoretical backdrop, the aim of this research, which consists of two studies, was to understand the process of goal setting and deciding to sign an organ donor car...Using the Health Action Process Approach (HAPA) as a theoretical backdrop, the aim of this research, which consists of two studies, was to understand the process of goal setting and deciding to sign an organ donor card. In Study 1 (N = 550), we tested the HAPA’s stages in terms of discontinuity patterns in the variables predicting goal setting for organ donation. As expected, multigroup structural equation modeling revealed discontinuity patterns in terms of different prediction patterns. In Study 2 (N = 389), the efficacy of a planning intervention that aimed to foster the translation of goals into behavior was tested: participants who received the intervention were more likely to order a donor card than those who did not. Contrary to the HAPA’s predictions, within the intenders group the planning intervention did not stimulate behavior more frequently than in the control condition. In general, the stage-specific planning intervention is of practical importance, as it shows that brief and relatively inexpensive communication can enhance organ donation behavior.展开更多
The rare metals of Abu Dabbab area in the Central Eastern Desert of Egypt have been investigated for their mineralogy and conditions of precipitation using combination of EMPA and fluid inclusions studies,in order to ...The rare metals of Abu Dabbab area in the Central Eastern Desert of Egypt have been investigated for their mineralogy and conditions of precipitation using combination of EMPA and fluid inclusions studies,in order to delineate the source,mechanism of formation and evolutionary model for these economic metals.The(Ta-Nb-Sn)-bearing minerals at the Abu Dabbab area include columbite group minerals(CGMs),wodginite and cassiterite.In both granitic intrusion and its enclosed quartz veins,most of zoned CGMs and cassiterite grains are commonly characterized by a well-developed twostage texture.Hence,columbite-(Mn)(CGM-Ⅰ)represents the early formed phase of CGMs that is characterized by high Mn#values(0.64-0.92)with quite low Ta#values(0.13-0.49).It was invaded by Ta-rich phases including tantalite-(Mn)(CGM-Ⅱ;Ta#=0.13-0.49)and wodginite,which contain high Ta_(2)O_(5)and SnO_(2)(17.91 wt.%).In regard to cassiterite,there are distinct compositional differences between the early-phase cassiterite(Cst-Ⅰ)and the late-phase one(Cst-Ⅱ),where the latter is enriched in Ta_(2)O_(5),Nb_(2)O_(5)and FeO.The chemistry and textural criteria of the early stage CGM-Ⅰand Cst-Ⅰ,all are indicative of magmatic origin.While,the latter CGM-Ⅱ,wodginite and Cst-Ⅱwere influenced by the late magmatic Ta-rich fluids.Fluid inclusions microthermometry shows criteria of phase separation represented by both boiling and fluid immiscibility.The initial fluid was supposed to be of magmatic origin(magmatic CH4),that was consequently influenced by fluid mixing/dilution with post-hydrothermal/meteoric water with respect to the decompression process during uplift.Isochore construction gave rise to an estimate P-T conditions(T=330-370℃,P=22-50 MPa).The fluid inclusions’microthermometry supports a transition between magmatic and late to post-hydrothermal activities in addition to surface-derived fluid(meteoric fluid?)in a part as main source for the polymetallic deposits.展开更多
Disaccharides are a very important group of carbohydrates, being main components of many daily food products. The heating of these biomolecule causes the formation of caramel, an extremely complex material. The domina...Disaccharides are a very important group of carbohydrates, being main components of many daily food products. The heating of these biomolecule causes the formation of caramel, an extremely complex material. The dominant fraction of non-volatile compounds, responsible for both color and flavor of food products, has been studied on a few occasions. Herein, the composition of caramels obtained by heating of sucrose, lactose and maltose were studied using combined mass spectrometry techniques. High resolution electrospray mass spectrometry was applied followed by targeted multi-stage LC-tandem mass spectrometry （ESI-MSn） and MALDI-MS. Novel graphical interpretation strategies such as van Krevelen and Kendrick mass analysis have been applied to study the composition of caramels. Products of caramel include oligomerization, depolymerization, hydration and dehydration products. Oligomers with up to eight carbohydrate units and dehydrated oligomers losing up to eight water molecules have been identified.展开更多
We consider a network composed of an arbitrary number of directed links. We employ a grand canonical partition function to study the statistical averages of the network in equilibrium. The Hamiltonian is composed of t...We consider a network composed of an arbitrary number of directed links. We employ a grand canonical partition function to study the statistical averages of the network in equilibrium. The Hamiltonian is composed of two parts: a “free” Hamiltonian H0 attributing a constant energy E to each link, and an interacting Hamiltonian Hint involving terms quadratic in the number of links. A Gaussian integration leads to a reformulated Hamiltonian, where now the number of links appears linearly. The reformulated Hamiltonian allows obtaining the exact behavior in limiting cases. At high temperatures the system reproduces the behavior of the free model, while at low temperatures the thermodynamic behavior is obtained by using a renormalized chemical potential, μeff = μ + l, where l is the strength of the interaction. We also resort to a mean field approximation, describing accurately the system over the entire range of all dynamical parameters. A detailed Monte-Carlo simulation verifies our theoretical expectations. We indicate that our model may serve as a prototype model to address a number of different systems.展开更多
文摘The concentrations of the rare earth elements (REE) in surface waters and sediments, when normalized on an element-by-element basis to one of several rock standards and plotted versus atomic number, yield curves that reveal their partitioning between different sediment fractions and the sources of those fractions, for example, between terrestrial-derived lithogenous debris and seawater-derived biogenous detritus and hydrogenous metal oxides. The REE of ancient sediments support their partitioning into these same fractions and further contribute to the identification of the redox geochemistry of the sea water in which the sediments accumulated. The normalized curves of the REE that have been examined in several South American wine varietals can be interpreted to reflect the lithology of the bedrock on which the vines may have been grown, suggesting limited fractionation during soil development.
文摘The knowledge of Martian geology has increased enormously in the last 40 yr. Several missions orbiting or roving Mars have revolutionized our understanding of its evolution and geological features, which in several ways are similar to Earth, but are extremely different in many respects. The impressive dichotomy between the two Martian hemispheres is most likely linked to its impact cratering history, rather than internal dynamics such as on Earth. Mars＇ volcanism has been extensive, very longlived and rather constant in its setting. Water was available in large quantities in the distant past of Mars, when a magnetic field and more vigorous tectonics were active. Exogenic forces have been shaping Martian landscapes and have led to a plethora of landscapes shaped by wind, water and ice. Mars＇ dynamical behavior continues, with its climatic variation affecting climate and geology until very recent times. This paper tries to summarize major highlights in Mars＇ Geology, and points to deeper and more extensive sources of important scientific contributions and future exploration.
基金This article contributes to the project"Systematic multi-scale modeling and analysis for geophysical flow"of the Collaborative Research Center TRR 181"Energy Transfers in Atmosphere and Ocean"funded by the Deutsche Forschungsgemeinschaft(DFG,German Research Foundation)under project number 274762653.
文摘In this article,we consider a fully nonlinear partial differential equation which can be expressed as a sum of two Monge-Ampere operators acting in different two-dimensional coordinate sections.This equation is elliptic,for example,in the class of convex functions.We show that the notion of Monge-Ampere measures and Aleksandrov generalized solutions extends to this equation,subject to a weaker notion of convexity which we call bi-planar convexity.While the equation is also elliptic in the class of bi-planar convex functions,the contrary is not necessarily true.This is a substantial difference compared to the classical Monge-Ampere equation where ellipticity and convexity coincide.We provide explicit counter-examples:classical solutions to the bi-planar equation that satisfy the ellipticity condition but are not generalized solutions in the sense introduced.We conclude that the concept of generalized solutions based on convexity arguments is not a natural setting for the bi-planar equation.
文摘Humans are exposed to radiofrequency electromagnetic fields （RFEMF） from various sources （e.g., mobile and cordless phones, base stations, TV and radio transmitters, wifi adapters）. So far, there is no evidence that would indicate that RFEMF exposure is causing adverse health effects with respect to cancer, sleep disorder, headache, etc. Some results of in vitro and in vivo experiments revealed negative effects on male fertility. When looking at those studies in detail, many problems are identified with respect to correct dosimetry and proper experimental design. This field of research is notoriously difficult for various reasons, and experiments should be planned and performed with experts from the respective areas.
文摘In steel continuous casting(CC),the choice of the appropriate speed at which the slab is cast can be influenced by many different factors and phenomena.While the slab thickness seems to have the biggest impact,other features like the slab width have been consistently overlooked.In fact,the slab width practically limits the casting speed via the mass flow constraint which governs the input and output balance at the tundish.Here,we present a case study that aims at analyzing steel production data from the perspective of casting speed constraints.By studying the speed fluctuations of an industrial CC machine,we identify a strategic regime change toward a stricter consideration of the mass flow constraint.The regime change manifests itself in a significant increase in the correlation between the actual casting speed and the maximal speed associated with the mass flow constraint.On the surface,taking greater account of the input and output balance at the tundish has reduced the productivity of the continuous caster;however,one can argue that the lessened yield is compensated by a diminished risk of eventual slab breaking.From the perspective of this trade-off,we establish a visualization technique that enables us to pinpoint the boundary beyond which one strategic regime becomes economically more advantageous than the other.
文摘Acquisition and registration of terrestrial 3D laser scans is a fundamental task in mapping and modeling of cities in three dimensions. To automate this task marker-flee registration methods are required. Based on the existence of skyline features, this paper proposes a novel method. The skyline features are extracted from panoramic 3D scans and encoded as strings enabling the use of string matching for merging the scans. Initial results of the proposed method in the old city center of Bremen are presented.
文摘Despite serotonin’s and FMRF-amide’s wide distribution in the nervous system of invertebrates and their importance as neurotransmitters, the exact roles they play in neuronal networks leaves many questions. We mapped the presence of serotonin and FMRF-amide-immunoreactivity in the central nervous system and eyes of the pond snail Lymnaea stagnalis and interpreted the results in connection with our earlier findings on the central projections of different peripheral nerves. Since the chemical nature of the intercellular connections in the retina of Lymnaea stagnalis is still largely unknown, we paid special attention to clarifying the role of serotonin and FMRF-amide in the visual system of this snail and compared our findings with those reported from other species. At least one serotonin-and one FMRF-amidergic fibre were labeled in each optic nerve, and since no cell bodies in the eye showed immunoreactivity to these neurotransmitters, we believe that efferent fibres with somata located in the central ganglia branch at the base of the eye and probably release 5HT and FMRF-amide as neuro-hormones. Double labelling revealed retrograde transport of neurobiotin through the optic nerve, allowing us to conclude that the central pathways and serotonin-and FMRF-amideimmunoreactive cells and fibres have different locations in the CNS in Lymnaea stagnalis. The chemical nature of the fibres, which connect the two eyes in Lymnaea stagnalis, is neither serotoninergic nor FMRF-amidergic.
文摘Afferent and efferent neural elements of the retina and central ganglia in the freshwater snail Planorbarius corneus were labelled using retrograde transport of neurobiotin through the optic nerve.Axons of at least some photoreceptor cells become direct contributors to the optic nerve as no synaptic junctions could be detected.The processes enter the cerebral ganglion and form a dense bundle of thin afferent fibres,the so-called optical neuropil.Efferent neurons were revealed in all ganglia,except the buccal ones.Some of the ascending axons branch in the cerebral ganglia,cross the cerebro-cerebral commissure,reach the contralateral eye and form arborizations in the eye cup.Some efferent neurons send axons to different peripheral nerves as well：n.n.intestinalis,pallialis dexter,pallialis sinister internus et externus.Serotonin-and FMRF-amide-ergic fibres were revealed in the optic nerve.These fibres belong to those central neurons which send their axons to the ipsilateral eye only.They form abundant varicoses in the eye cup and nuclear layer of the retina,and possibly help to regulate retinal sensitivity to light.
基金This work was supported by DAAD student fellowship
文摘Despite serotonin’s and FMRF-amide’s wide distribution in the nervous system of invertebrates and their importance as neurotransmitters,the exact roles they play in neuronal networks leaves many questions.We mapped the presence of serotonin and FMRF-amide-immunoreactivity in the central nervous system and eyes of the pond snail Lymnaea stagnalis and interpreted the results in connection with our earlier findings on the central projections of different peripheral nerves.Since the chemical nature of the intercellular connections in the retina of L.stagnalis is still largely unknown,we paid special attention to clarifying the role of serotonin and FMRF-amide in the visual system of this snail and compared our findings with those reported from other species.At least one serotonin-and one FMRF-amidergic fibre were labeled in each optic nerve,and since no cell bodies in the eye showed immunoreactivity to these neurotransmitters,we believe that efferent fibres with somata located in the central ganglia branch at the base of the eye and probably release 5HT and FMRF-amide as neuro-hormones.Double labelling revealed retrograde transport of neurobiotin through the optic nerve,allowing us to conclude that the central pathways and serotonin-and FMRF-amide-immunoreactive cells and fibres have different locations in the CNS in L.stagnalis.The chemical nature of the fibres,which connect the two eyes in L.stagnalis,is neither serotoninergic nor FMRF-amidergic.
文摘For 20 years the so-called ＂sperm crisis＂ caused unrest among the public as well as the scientific community. Studies precipitated by this virtual crisis have refuted its existence, but have also illuminated hitherto neglected aspects of male reproductive function and indicated a need for prospective, long-term monitoring systems.
文摘Typically, a Lewis acid and a Lewis base can react with each other and form a classical Lewis adduct. The neutralization reaction can however be prevented by ligating the acid and base with bulky substituents and the resulting complex is known as a "frustrated Lewis pair"(FLP). Since the Lewis acid and base reactivity remains in the formed complex, FLPs can display interesting chemical activities, with promising applications in catalysis. For example, FLPs were shown to function as the first metal-free catalyst for molecular hydrogen activation. This, and other recent applications of FLPs, have opened a new thriving research field. In this short-review, we recapitulate the computational and experimental studies of the H_2 activation by FLPs. We discuss the thus-far uncovered mechanistic aspects, including pre-organization of FLPs,the reaction paths for the activation, the polarization of He H bond and other factors affecting the reactivity. We aim to provide a rather complete mechanistic picture of the H_2 activation by FLPs, which has been under debate for decades since the first discovery of FLPs. This review is meant as a starting point for future studies and a guideline for industrial applications.
基金supports from the National Natural Science Foundation of China (No. 21761132021)German Research Foundation (No. RO362/74–1)Qin Lan project from Jiangsu Province for JLH is also acknowledged
文摘An efficient chlorination reaction of in situ generated(β-diazo-α,α-difluoroethyl)phosphonates has been achieved with hydrochloric acid as a chlorine source under mild and operationally convenient conditions.The reaction does not need any catalyst and tolerates a wide scope of substrates,which affords the(β-chlorodifluoroethyl)phosphonate products in good to excellent yields.This reaction represents the first example of the halogenation of difluoroalkyl diazo compounds,and also provides an easy way for the synthesis of difluoromethylenephosphonate-containing compounds.
文摘Background: The opinion of physicians clearly counts in prioritizing health care, but there is little information on the rationales underlying treatment decisions and whether these rationales are accepted by patients. Objective: To compare physicians and patients regarding their understanding and use of therapeutic benefit and treatment costs as criteria for prioritizing health care. Methods: Seven physicians and twelve patients were purposefully selected to yield a heterogeneous sample. Participants were interviewed face-to-face, following a semi-structured topic guide comprising three scenarios that focused on interventions with low or unproven therapeutic benefit and high costs, respectively. For data analysis we used qualitative content analysis. Results: We found that patients and physicians differed in their understanding of therapeutic benefit, their expectations of what medicine can do and their use of costs as criteria for prioritizing health care. Physicians were less likely to assess a certain intervention as effec tive, and they less often accepted upper funding limits in health care. Unlike the physicians, patients raised non-medical aspects in decision making such as the patient’s consent and social inequalities. Conclusions: The revealed differences point toward the necessity to strengthen the doctor-patient communication, to improve information for patients about the possibilities and limits of health care and to gain a deeper understanding of their attitudes, wishes and concerns to reach an agreement by physicians and patients on the treatment to be implemented.
基金supported by the National Natural Science Foundation of China(No.21371173,51402298,91545125)the China Postdoctoral Foundation(No.2014M550846)
文摘A highly efficient catalyst of graphene-supported mixed-valent Mn_(16)-containing polyoxometalate is reported here by electrochemical strategy. The modified electrode with the catalyst exhibits an excellent electrocatalytic performance for water oxidation, which will contribute to the development of highly efficient catalysts for oxygen evolution.
文摘Using the Health Action Process Approach (HAPA) as a theoretical backdrop, the aim of this research, which consists of two studies, was to understand the process of goal setting and deciding to sign an organ donor card. In Study 1 (N = 550), we tested the HAPA’s stages in terms of discontinuity patterns in the variables predicting goal setting for organ donation. As expected, multigroup structural equation modeling revealed discontinuity patterns in terms of different prediction patterns. In Study 2 (N = 389), the efficacy of a planning intervention that aimed to foster the translation of goals into behavior was tested: participants who received the intervention were more likely to order a donor card than those who did not. Contrary to the HAPA’s predictions, within the intenders group the planning intervention did not stimulate behavior more frequently than in the control condition. In general, the stage-specific planning intervention is of practical importance, as it shows that brief and relatively inexpensive communication can enhance organ donation behavior.
基金Ministry of Higher Education of Egypt for supporting his research stay at University of Vienna(Austria)as a postdoctoral fellow。
文摘The rare metals of Abu Dabbab area in the Central Eastern Desert of Egypt have been investigated for their mineralogy and conditions of precipitation using combination of EMPA and fluid inclusions studies,in order to delineate the source,mechanism of formation and evolutionary model for these economic metals.The(Ta-Nb-Sn)-bearing minerals at the Abu Dabbab area include columbite group minerals(CGMs),wodginite and cassiterite.In both granitic intrusion and its enclosed quartz veins,most of zoned CGMs and cassiterite grains are commonly characterized by a well-developed twostage texture.Hence,columbite-(Mn)(CGM-Ⅰ)represents the early formed phase of CGMs that is characterized by high Mn#values(0.64-0.92)with quite low Ta#values(0.13-0.49).It was invaded by Ta-rich phases including tantalite-(Mn)(CGM-Ⅱ;Ta#=0.13-0.49)and wodginite,which contain high Ta_(2)O_(5)and SnO_(2)(17.91 wt.%).In regard to cassiterite,there are distinct compositional differences between the early-phase cassiterite(Cst-Ⅰ)and the late-phase one(Cst-Ⅱ),where the latter is enriched in Ta_(2)O_(5),Nb_(2)O_(5)and FeO.The chemistry and textural criteria of the early stage CGM-Ⅰand Cst-Ⅰ,all are indicative of magmatic origin.While,the latter CGM-Ⅱ,wodginite and Cst-Ⅱwere influenced by the late magmatic Ta-rich fluids.Fluid inclusions microthermometry shows criteria of phase separation represented by both boiling and fluid immiscibility.The initial fluid was supposed to be of magmatic origin(magmatic CH4),that was consequently influenced by fluid mixing/dilution with post-hydrothermal/meteoric water with respect to the decompression process during uplift.Isochore construction gave rise to an estimate P-T conditions(T=330-370℃,P=22-50 MPa).The fluid inclusions’microthermometry supports a transition between magmatic and late to post-hydrothermal activities in addition to surface-derived fluid(meteoric fluid?)in a part as main source for the polymetallic deposits.
文摘Disaccharides are a very important group of carbohydrates, being main components of many daily food products. The heating of these biomolecule causes the formation of caramel, an extremely complex material. The dominant fraction of non-volatile compounds, responsible for both color and flavor of food products, has been studied on a few occasions. Herein, the composition of caramels obtained by heating of sucrose, lactose and maltose were studied using combined mass spectrometry techniques. High resolution electrospray mass spectrometry was applied followed by targeted multi-stage LC-tandem mass spectrometry （ESI-MSn） and MALDI-MS. Novel graphical interpretation strategies such as van Krevelen and Kendrick mass analysis have been applied to study the composition of caramels. Products of caramel include oligomerization, depolymerization, hydration and dehydration products. Oligomers with up to eight carbohydrate units and dehydrated oligomers losing up to eight water molecules have been identified.
文摘We consider a network composed of an arbitrary number of directed links. We employ a grand canonical partition function to study the statistical averages of the network in equilibrium. The Hamiltonian is composed of two parts: a “free” Hamiltonian H0 attributing a constant energy E to each link, and an interacting Hamiltonian Hint involving terms quadratic in the number of links. A Gaussian integration leads to a reformulated Hamiltonian, where now the number of links appears linearly. The reformulated Hamiltonian allows obtaining the exact behavior in limiting cases. At high temperatures the system reproduces the behavior of the free model, while at low temperatures the thermodynamic behavior is obtained by using a renormalized chemical potential, μeff = μ + l, where l is the strength of the interaction. We also resort to a mean field approximation, describing accurately the system over the entire range of all dynamical parameters. A detailed Monte-Carlo simulation verifies our theoretical expectations. We indicate that our model may serve as a prototype model to address a number of different systems.
