A novel mechanism to produce and detect light dark matter in experiments making use of GeV electrons (and positrons) impinging on a thick target (beam dump) is proposed. The positron-rich environment ...produced by the electromagnetic shower allows us to produce an A^{'} via nonresonant (e^{+}+e^{-}→γ+A^{'}) and resonant (e^{+}+e^{-}→A^{'}) annihilation on atomic electrons. The latter mechanism, for some selected kinematics, results in a larger sensitivity with respect to limits derived by the commonly used A^{'}-strahlung. This idea, applied to beam-dump experiments and active beam-dump experiments, pushes down the current limits by an order of magnitude.
High-energy positron annihilation is a viable mechanism to produce dark photons (A′). This reaction plays a significant role in beam-dump experiments using multi-GeV electron beams on thick targets ...by enhancing the sensitivity to A′ production. The positrons produced by the electromagnetic shower can produce an A′ via nonresonant (e++e−→γ+A′) and resonant (e++e−→A′) annihilation on atomic electrons. For visible decays, the contribution of resonant annihilation results in a larger sensitivity with respect to limits derived by the commonly used A′-strahlung in certain kinematic regions. When included in the evaluation of the E137 beam-dump experiment reach, positron annihilation pushes the current limit on ϵ downwards by a factor of 2 in the range 33 MeV/c2<mA′<120 MeV/c2.
Medium-energy electron beam-dump experiments provide an intense source of secondary muons. These particles can be used to search for muon-coupling light dark scalars that may explain the (g − 2)μ ...anomaly. We applied this idea to the SLAC E137 experiment deriving new exclusion limits and evaluated the expected sensitivity for the planned Jefferson Lab BDX experiment (in case of a null result report). The calculation is based on numerical simulations that include a realistic description of secondary muons generation in the dump, dark scalar production, propagation, and decay, and, finally, the decay product (electrons, positrons, or photons) interaction with the detector. For both experiments, exclusion limits were extended to cover a broader area in the scalar-to-muon coupling vs scalar mass parameter space. This study demonstrates that electron beam-dump experiments have an enhanced sensitivity to new physics in processes that are usually studied using proton beams.
This paper describes the design and performance of a compact detector, BDX-MINI, that incorporates all features of a concept that optimized the detection of light dark matter in the MeV-GeV mass ...range produced by electrons in a beam dump. It represents a reduced version of the future BDX experiment expected to run at JLAB. BDX-MINI was exposed to penetrating particles produced by a 2.176 GeV electron beam incident on the beam dump of Hall A at Jefferson Lab. The detector consists of 30.5 kg of PbWO
4
crystals with sufficient material following the beam dump to eliminate all known particles except neutrinos. The crystals are read out using silicon photomultipliers. Completely surrounding the detector are a passive layer of tungsten and two active scintillator veto systems, which are also read out using silicon photomultipliers. The design was validated and the performance of the robust detector was shown to be stable during a six month period during which the detector was operated with minimal access.
The organic compound 2-phenylethanol (2PE) has a pleasant floral scent and is intensively used in the cosmetic and food industries. Microbial production of 2PE by phenylalanine bioconversion or de ...novo biosynthesis from sugar offer sustainable, reliable and natural production processes compared to chemical synthesis. Despite the ability of Saccharomyces cerevisiae to naturally synthesize 2PE, de novo synthesis in high concentration and yield remains a metabolic engineering challenge. Here, we demonstrate that improving phosphoenolpyruvate supply by expressing pyruvate kinase variants and eliminating the formation of p-hydroxy-phenylethanol without creating tyrosine auxotrophy significantly contributed to improve 2PE production in S. cerevisiae. In combination with the engineering of the aromatic amino acid biosynthesis and Ehrlich pathway, these mutations enabled better connection between glycolysis and pentose phosphate pathway optimizing carbon flux towards 2PE. However, attempts to further connect these two parts of central carbon metabolism by redirecting fructose-6P towards erythrose-4P by expressing a phosphoketolase-phosphotransacetylase pathway did not result in improved performance. The best performing strains were capable of producing 13mM of 2PE at a yield of 0.113 mol mol-1, which represents the highest yield for de novo produced 2PE in S. cerevisiae and other yeast species.
•PYK1D147N expression supplies an improved PEP flux towards 2PE synthesis.•TYR1 expression driven by YEN1pr results in >90% reduction of pOH2PE.•Expression of a BbXfpk and Ckpta shunt did not result in improve 2PE production.•2PE production is limited by product inhibition.•The best performing strain produced 13mM of 2PE with a 0.113 mol mol-1
The CLAS12 Trigger System Raydo, B.; Boyarinov, S.; Celentano, A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2020, Letnik:
960, Številka:
C
Journal Article
Recenzirano
Odprti dostop
This article describes the CLAS12 Trigger System. The simulation, hardware, and software design, as well as all validation procedures, are discussed. The firmware development tools used are discussed ...as well, including our experience with VIVADO High Level Synthesis.
An unsteady one-dimensional model for the solid phase is applied to simulate the spontaneous ignition and burning of thick wood samples with grain orientation parallel or perpendicular to incident ...heat fluxes in the range 18–40 kW/m2, that is, in the absence of flame. The description of heat and mass transfer processes, at constant gas pressure, is combined with global volumetric rates of wood decomposition and char oxidation. Surface regression occurs for a limit value of char density while a critical surface temperature describes ignition. Good quantitative predictions are obtained for the ignition times and the surface temperature and mass loss rate profiles during burning. Conversion always consists of three main stages. The first short transients correspond to the formation of a relatively thin charred surface layer and glowing ignition. The second much longer stage represents a pseudo-steady-state burning, where the rates of advancement of the decomposition and oxidation zones are approximately constant as well as the surface temperature and the global rate of mass loss. Finally, the last short stage, resulting from the adiabatic bottom condition, is the enlargement of the decomposition zone to the entire sample. The first transient stage and the ignition times are noticeably affected by the external heating conditions whereas the characteristics of the pseudo-steady-state burning are mainly dependent on the char oxidation rate, which is controlled by the oxygen diffusion rate.
•The mathematical model describes passive and active mechanical responses of muscles.•It is formulated within a rational mechanical framework.•It is tested with isometric and isotonic data from ...murine extensor digitorum muscle.•It provides a measure of the muscle rest length.•It captures experimental observations with only 3 scalar parameters.
A new mathematical model is presented to describe both the active and passive mechanics of muscles. In order to account for the active response, a two–layer kinematics that introduces both the visible and rest lengths of the muscle is presented within a rational mechanics framework. The formulation is based on an extended version of the principle of virtual power and the dissipation principle. By using an accurate constitutive description of muscle mobility under activation, details of microscopic processes that lead to muscle contraction are glossed over while macroscopic effects of chemical/electrical stimuli on muscle mechanics are retained. The model predictions are tested with isometric and isotonic experimental data collected from murine extensor digitorum muscle. It is shown that the proposed model captures experimental observations with only three scalar parameters.
The CLAS12 Geant4 simulation Ungaro, M.; Angelini, G.; Battaglieri, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2020, Letnik:
959, Številka:
C
Journal Article
Recenzirano
Odprti dostop
The Geant4 Monte-Carlo (GEMC) package is used to simulate the passage of particles through the various CLAS12 detectors. The geometry is implemented through a database of Geant4 volumes created ...either through the GEMC native API, by the CLAS12 geometry service, or imported from the CAD engineering model. The truth information is digitized with a plugin mechanism by routines specific to each detector and includes the use of the CLAS12 calibration database constants to produce both ADC and TDC response functions. Theoretical models that produce the generated events interface with GEMC through the LUND data format. The merging of simulated data with real random trigger data provides a mechanism to include both beam and electronic background into the simulation of generated events to accurately model beam data from the CLAS12 detector. The performance of simulation is demonstrated by comparison with the experimental data.
Background
Conflicting evidence challenges clinical decision‐making when breast reconstruction is considered in the context of radiotherapy. Current literature was evaluated and key statements on ...topical issues were generated and discussed by an expert panel at the International Oncoplastic Breast Surgery Meeting in Milan 2017.
Methods
Studies on radiotherapy and breast reconstruction (1985 to September 2017) were screened using MEDLINE, Embase and CENTRAL. The literature review yielded 30 controversial key questions. A set of key statements was derived and the highest levels of clinical evidence (LoE) for each of these were summarized. Nineteen panellists convened for dedicated discussions at the International Oncoplastic Breast Surgery Meeting to express agreement, disagreement or abstention for the generated key statements.
Results
The literature review identified 1522 peer‐reviewed publications. A list of 22 key statements was produced, with the highest LoE recorded for each statement. These ranged from II to IV, with most statements (11 of 22, 50 per cent) supported by LoE III. There was full consensus for nine (41 per cent) of the 22 key statements, and more than 75 per cent agreement was reached for half (11 of 22).
Conclusion
Poor evidence exists on which to base patient‐informed consent. Low‐quality studies are conflicting with wide‐ranging treatment options, precluding expert consensus regarding optimal type and timing of breast reconstruction in the context of radiotherapy. There is a need for high‐quality evidence from prospective registries and randomized trials in this field.
Antecedentes
El hecho de que la evidencia disponible sea conflictiva supone un reto para la toma de decisiones a la hora de considerar la reconstrucción mamaria en el contexto de radioterapia (radiotherapy, RT). En el seno de un panel de expertos reunidos durante el International Oncoplastic Breast Surgery Meeting celebrado en Milán en 2017, se revisó la literatura disponible y se generaron y discutieron los aspectos más relevantes.
Métodos
Se hizo una búsqueda bibliográfica de los estudios de RT y reconstrucción mamaria (1985‐septiembre de 2017) en las bases MEDLINE, EMBASE y CENTRAL. La revisión de la literatura permitió identificar 30 cuestiones clave controvertidas. A partir de ellas, se construyeron una serie de afirmaciones, para las que se obtuvo el mayor nivel de evidencia (levels of clinical evidence, LoE) posible. El acuerdo, desacuerdo o abstención respecto a las cuestiones propuestas fueron el resultado de las discusiones de 19 expertos reunidos durante el International Oncoplastic Breast Surgery Meeting.
Resultados
Se identificaron 1.522 artículos publicados en revistas con peer review. Se elaboró una lista de 22 afirmaciones clave y se anotó el LoE más alto obtenido para cada una de ellas. El grado de variabilidad fue de II a IV, pero la mayoría de las afirmaciones (54,5%) obtuvieron un LoE III. Hubo un consenso total en el 41% (9/22) de las afirmaciones, mientras que se obtuvo más de un 75% de acuerdo en la mitad de las afirmaciones (11/22).
Conclusión
La evidencia en la que basar el consentimiento informado en estos pacientes es escasa. Se trata de estudios de baja calidad con gran variedad de opciones terapéuticas, que dificultan el consenso de los expertos acerca del tipo y momento óptimo para la reconstrucción mamaria en el contexto de RT. Para obtener datos de mayor calidad se precisan estudios prospectivos y ensayos clínicos en este campo.
Conflicting evidence challenges clinical decision‐making when breast reconstruction is considered in the context of radiotherapy. This study aimed to evaluate the current literature and generate key statements on topical issues that were discussed by an expert panel at the International Oncoplastic Breast Surgery Meeting in Milan in 2017. Poor evidence exists on which to base patient‐informed consent. Low‐quality studies are conflicting with wide‐ranging treatment options, precluding expert consensus regarding optimal type and timing for breast reconstruction in the context of radiotherapy. There is a need for high‐quality evidence from prospective registries and randomized trials in this field.
More research needed urgently
PDF
