334 research outputs found
Soft Gamma Rays from Heavy WIMPs
We propose an explanation of the galactic center gamma ray excess by
supersymmetric WIMPs as heavy as 500 GeV. The lightest neutralino annihilates
into vector-like leptons or quarks which cascade decay through intermediate
Higgs bosons. Due to the long decay chains, the gamma ray spectrum is much
softer than naively expected and peaks at GeV energies. The model predicts
correlated diboson and dijet signatures to be tested at the LHC.Comment: 8 pages, 8 figures; v2: focus on gamma ray excess, matches published
versio
Distilling Non-Locality
Two parts of an entangled quantum state can have a correlation in their joint
behavior under measurements that is unexplainable by shared classical
information. Such correlations are called non-local and have proven to be an
interesting resource for information processing. Since non-local correlations
are more useful if they are stronger, it is natural to ask whether weak
non-locality can be amplified. We give an affirmative answer by presenting the
first protocol for distilling non-locality in the framework of generalized
non-signaling theories. Our protocol works for both quantum and non-quantum
correlations. This shows that in many contexts, the extent to which a single
instance of a correlation can violate a CHSH inequality is not a good measure
for the usefulness of non-locality. A more meaningful measure follows from our
results.Comment: Revised abstract, introduction and conclusion. Accepted by PR
Intrinsic spin dynamics in semiconductor quantum dots
We investigate the characteristic spin dynamics corresponding to
semiconductor quantum dots within the multiband envelope function approximation
(EFA). By numerically solving an Hamiltonian we treat
systems based on different III-V semiconductor materials.It is shown that, even
in the absence of an applied magnetic field, these systems show intrinsic spin
dynamics governed by intraband and interband transitions leading to
characteristic spin frequencies ranging from the THz to optical frequencies.Comment: to be published in Nanotechnology. Separated figure file
Proactive food waste prevention in grocery retail supply chains – an exploratory study
Purpose
Regarding the retail internal supply chain (SC), both retailers and research are currently focused on reactive food waste reduction options in stores (e.g. discounting or donations). These options reduce waste after a surplus has emerged but do not prevent an emerging surplus in the first place. This paper aims to reveal how retailers can proactively prevent waste along the SC and why the options identified are impactful but, at the same time, often complex to implement.
Design/methodology/approach
The authors follow an exploratory approach for a nascent topic to obtain insights into measures taken in practice. Interviews with experts from retail build the main data source.
Findings
The authors identify and analyze 21 inbound, warehousing, distribution and store-related options applied in grocery retail. Despite the expected high overall impact on waste, prevention measures in inbound logistics and distribution and warehousing have not been intensively applied to date.
Practical implications
The authors provide a structured approach to mitigate waste within retailers' operations and categorize the types of barriers that need to be addressed.
Originality/value
This research provides a better understanding of prevention options in retail operations, which has not yet been empirically explored. Furthermore, this study conceptualizes prevention and reduction options and reveals implementation patterns
Interplay between Zeeman interaction and spin-orbit coupling in a two-dimensional semiconductor system
We analyse the interplay between Dresselhaus, Bychkov-Rashba, and Zeeman
interactions in a two-dimensional semiconductor quantum system under the action
of a magnetic field. When a vertical magnetic field is considered, we predict
that the interplay results in an effective cyclotron frequency that depends on
a spin-dependent contribution. For in-plane magnetic fields, we found that the
interplay induces an anisotropic effective gyromagnetic factor that depends on
the orientation of the applied field as well as on the orientation of the
electron momentum.Comment: 5 page
Acoustic Resonance Effects and Cavitation in SAW Aerosol Generation
The interaction of surface acoustic waves (SAWs) with liquids enables the
production of aerosols with adjustable droplet sizes in the micrometer range
expelled from a very compact source. Understanding the nonlinear
acousto-hydrodynamics of SAWs with a regulated micro-scale liquid film is
essential for acousto-microfluidics platforms, particularly aerosol generators.
In this study, we demonstrate the presence of micro-cavitation in an
MHz-frequency SAW aerosol generation platform, which is touted as a leap in
aerosol technology with versatile application fields including biomolecule
inhalation therapy, micro-chromatography and spectroscopy, olfactory displays,
and material deposition. Using analysis methods with high temporal and spatial
resolution, we demonstrate that SAWs stabilize spatially arranged liquid
micro-domes atop the generator's surface. Our experiments show that these
liquid domes become acoustic resonators with highly fluctuating pressure
amplitudes that can even nucleate cavitation bubbles, as supported by
analytical modeling. The observed fragmentation of liquid domes indicates the
participation of three droplet generation mechanisms, including cavitation and
capillary-wave instabilities. During aerosol generation, the cavitation bubbles
contribute to the ejection of droplets from the liquid domes and also explain
observed microstructural damage patterns on the chip surface eventually caused
by cavitation-based erosion
Ascending Axonal Degeneration of the Corticospinal Tract in Pure Hereditary Spastic Paraplegia: A Cross-Sectional DTI Study
Objective: To identify structural white matter alterations in patients with pure hereditary spastic paraplegia (HSP) using high angular resolution diffusion tensor imaging (DTI). Methods: We examined 37 individuals with high resolution DTI, 20 patients with pure forms of hereditary spastic paraplegia and 17 age and gender matched healthy controls. DTI was performed using a 3 T clinical scanner with whole brain tract-based spatial statistical (TBSS) analysis of the obtained fractional anisotropy (FA) data as well as a region-of-interest (ROI)-based analysis of affected tracts including the cervical spinal cord. We further conducted correlation analyses between DTI data and clinical characteristics. Results: TBSS analysis in HSP patients showed significantly decreased fractional anisotropy of the corpus callosum and the corticospinal tract compared to healthy controls. ROI-based analysis confirmed significantly lower FA in HSP compared to controls in the internal capsule (0.77 vs. 0.80, p = 0.048), the corpus callosum (0.84 vs. 0.87, p = 0.048) and the cervical spinal cord (0.72 vs. 0.79, p = 0.003). FA values of the cervical spinal cord significantly correlated with disease duration. Conclusion: DTI metrics of the corticospinal tract from the internal capsule to the cervical spine suggest microstructural damage and axonal degeneration of motor neurons. The CST at the level of the cervical spinal cord is thereby more severely affected than the intracranial part of the CST, suggesting an ascending axonal degeneration of the CST. Since there is a significant correlation with disease duration, FA may serve as a future progression marker for assessment of the disease course in HSP
The Use and Impact of Biotechnology in Potato Breeding: Experience of the Potato Breeding Program at INIA, Chile
The potato breeding program of Instituto de Investigaciones Agropecuarias (INIA) Chile has developed and released 11 commercial varieties of potato. It is estimated that these varieties have 50% of the Chilean potato market and are being evaluated in seven foreign countries. The aim of this work is to summarize the current importance and scope of biotechnology in breeding in Chile, by presenting a program that has generated widespread material among farmers and consumers. The germplasm bank is the source of genetic diversity for controlled crosses. Techniques to introduce the material to in vitro conditions and thermotherapy to obtain pathogen-free in vitro plants are applied. The material is characterized by SSR markers. There is a flow of material from gene bank to the annual scheme of controlled crosses and selection in the plant breeding program. In the selection plots, molecular markers associated with one or few genes that have a large and heritable effect in important traits are used: golden nematode resistance, virus resistance, and late blight resistance. Then, in the early stages of seed production, all the material of the new varieties is checked by fingerprint and molecular and ELISA test for pathogen, to assure the identity and pathogen-free status of the starting seed material
Making food systems safer: Time to curb use of highly hazardous pesticides
Use of synthetic chemical pesticides has expanded widely. These insecti-cides, herbicides, and fungicides have helped to boost crop production, but at a major cost – one whose full extent remains unknown. Many commonly used pesticides – especially in developing countries – are now considered “highly hazardous” by experts due to their proven or likely harms to nature and people.1 Evidence from farms in the global South confirms heavy use of pesticides, including substances banned elsewhere. Farmers and nearby communities face the most direct health threats. This policy brief outlines key harms and research findings, high-lights alternatives to pesticide-intensive agricultural practices, and calls for phasing out the riskiest substances – in line with human rights and proper application of the precautionary principle
Recent advances in the biology and treatment of brain metastases of non-small cell lung cancer: summary of a multidisciplinary roundtable discussion
This article is the result of a round table discussion held at the European Lung Cancer Conference (ELCC) in Geneva in May 2017. Its purpose is to explore and discuss the advances in the knowledge about the biology and treatment of brain metastases originating from non-small cell lung cancer. The authors propose a series of recommendations for research and treatment within the discussed context
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