305 research outputs found
Modified Structure of Protons and Neutrons in Correlated Pairs
The atomic nucleus is made of protons and neutrons (nucleons), that arethemselves composed of quarks and gluons. Understanding how the quark-gluonstructure of a nucleon bound in an atomic nucleus is modified by thesurrounding nucleons is an outstanding challenge. Although evidence for suchmodification, known as the EMC effect, was first observed over 35 years ago,there is still no generally accepted explanation of its cause. Recentobservations suggest that the EMC effect is related to close-proximity ShortRange Correlated (SRC) nucleon pairs in nuclei. Here we report the firstsimultaneous, high-precision, measurements of the EMC effect and SRCabundances. We show that the EMC data can be explained by a universalmodification of the structure of nucleons in neutron-proton (np) SRC pairs andpresent the first data-driven extraction of this universal modificationfunction. This implies that, in heavier nuclei with many more neutrons thanprotons, each proton is more likely than each neutron to belong to an SRC pairand hence to have its quark structure distorted
Transmission of High-Power Electron Beams Through Small Apertures
Tests were performed to pass a 100 MeV, 430 kWatt c.w. electron beam from the
energy-recovery linac at the Jefferson Laboratory's FEL facility through a set
of small apertures in a 127 mm long aluminum block. Beam transmission losses of
3 p.p.m. through a 2 mm diameter aperture were maintained during a 7 hour
continuous run.Comment: arXiv admin note: text overlap with arXiv:1305.019
Measured Radiation and Background Levels During Transmission of Megawatt Electron Beams Through Millimeter Apertures
We report measurements of photon and neutron radiation levels observed while
transmitting a 0.43 MW electron beam through millimeter-sized apertures and
during beam-off, but accelerating gradient RF-on, operation. These measurements
were conducted at the Free-Electron Laser (FEL) facility of the Jefferson
National Accelerator Laboratory (JLab) using a 100 MeV electron beam from an
energy-recovery linear accelerator. The beam was directed successively through
6 mm, 4 mm, and 2 mm diameter apertures of length 127 mm in aluminum at a
maximum current of 4.3 mA (430 kW beam power). This study was conducted to
characterize radiation levels for experiments that need to operate in this
environment, such as the proposed DarkLight Experiment. We find that sustained
transmission of a 430 kW continuous-wave (CW) beam through a 2 mm aperture is
feasible with manageable beam-related backgrounds. We also find that during
beam-off, RF-on operation, multipactoring inside the niobium cavities of the
accelerator cryomodules is the primary source of ambient radiation when the
machine is tuned for 130 MeV operation.Comment: 9 pages, 11 figures, submitted to Nuclear Instruments and Methods in
Physics Research Section
Mapping Iranian patents based on International Patent Classification (IPC), from 1976 to 2011
Australian Gay Men’s Satisfaction with Sexual Agreements: The Roles of Relationship Quality, Jealousy, and Monogamy Attitudes
Measuring efficiency of innovation using combined Data Envelopment Analysis and Structural Equation Modeling:empirical study in EU regions
The main aim of this paper is to investigate the impact of patent applications, development level, employment level and degree of technological diversity on innovation efficiency. Innovation efficiency is derived by relating innovation inputs and innovation outputs. Expenditures in Research and Development and Human Capital stand for innovation inputs. Technological knowledge diffusion that comes from spatial and technological neighborhood stands for innovation output. We derive innovation efficiency using Data Envelopment Analysis for 192 European regions for a 12-year period (1995–2006). We also examine the impact of patents production, development and employment level and the level of technological diversity on innovation efficiency using Structural Equation Modeling. This paper contributes a method of innovation efficiency estimation in terms of regional knowledge spillovers and causal relationship of efficiency measurement criteria. The study reveals that the regions presenting high innovation activities through patents production have higher innovation efficiency. Additionally, our findings show that the regions characterized by high levels of employment achieve innovation sources exploitation efficiently. Moreover, we find that the level of regional development has both a direct and indirect effect on innovation efficiency. More accurately, transition and less developed regions in terms of per capita GDP present high levels of efficiency if they innovate in specific and limited technological fields. On the other hand, the more developed regions can achieve high innovation efficiency if they follow a more decentralized innovation policy
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