University of Groningen

About: University of Groningen is a education organization based out in Groningen, Groningen, Netherlands. It is known for research contribution in the topics: Population & Context (language use). The organization has 36346 authors who have published 69116 publications receiving 2940370 citations. The organization is also known as: Rijksuniversiteit Groningen & RUG.

Diagnosis and Management of Stable Chronic Obstructive Pulmonary Disease: A Clinical Practice Guideline Update from the American College of Physicians, American College of Chest Physicians, American Thoracic Society, and European Respiratory Society

Abstract: This guideline from 4 medical societies updates the 2007 American College of Physicians clinical practice guideline on diagnosis and management of stable chronic obstructive pulmonary disease (COPD...

Treatment of single brain metastasis: Radiotherapy alone or combined with neurosurgery

Abstract: Most patients treated for single or multiple brain metastases die from progression of extracranial tumor activity. This makes it uncertain whether the combination of neurosurgery and radiotherapy for treatment of single brain metastasis will lead to better results than less invasive treatment with radiotherapy alone. The effect of neurosurgical excision plus radiotherapy was compared with radiotherapy alone in a prospectively randomized trial with 63 evaluable patients with systemic cancer and a radiological diagnosis of single brain metastasis. Radiotherapy was given to the whole brain by a novel scheme of 2 fractions per day of each 2 Gy for a total of 40 Gy. Before randomization, patients were stratified by site (lung cancer vs nonlung cancer) and status of extracranial disease (progressive vs stable). Survival as such and functionally independent survival (FIS; defined as World Health Organization performance status < or = 1 and neurological function < or = 1) were compared between both treatment arms. The combined treatment compared with radiotherapy alone led to a longer survival (p = 0.04) and a longer FIS (p = 0.06). This was most pronounced in patients with stable extracranial disease (median survival, 12 vs 7 mo; median FIS, 9 vs 4 mo). Patients with progressive extracranial cancer had a median overall survival of 5 months and a FIS of 2.5 months irrespective of given treatment. Improvement in functional status occurred more rapidly and for longer periods of time after neurosurgical excision and radiotherapy than after radiotherapy alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Sampling and Definitions of Placental Lesions: Amsterdam Placental Workshop Group Consensus Statement

Abstract: Context.—The value of placental examination in investigations of adverse pregnancy outcomes may be compromised by sampling and definition differences between laboratories. Objective.—To establish an agreed-upon protocol for sampling the placenta, and for diagnostic criteria for placental lesions. Recommendations would cover reporting placentas in tertiary centers as well as in community hospitals and district general hospitals, and are also relevant to the scientific research community. Data Sources.—Areas of controversy or uncertainty were explored prior to a 1-day meeting where placental and perinatal pathologists, and maternal-fetal medicine specialists discussed available evidence and subsequently reached consensus where possible. Conclusions.—The group agreed on sets of uniform sampling criteria, placental gross descriptors, pathologic terminologies, and diagnostic criteria. The terminology and microscopic descriptions for maternal vascular malperfusion, fetal vascular malperfusion, delayed villous m...

Quantum Mechanics of Electrons in Crystal Lattices

Abstract: Introduction .–Through the work of Bloch our understanding of the behaviour of electrons in crystal lattices has been much advanced. The principal idea of Bloch’s theory is the assumption that the interaction of a given electron with the other particles of the lattice may be replaced in first approximation by a periodic field of potential. With this model an interpretation of the specific heat, the electrical and thermal conductivity, the magnetic susceptibility, the Hall effect, and the optical properties of metals could be obtained. The advantages and limitations inherent in the assumption of Bloch will be much the same as those encountered when replacing the interaction of the electrons in an atom by a suitable central shielding of the unclear field, as in the work of Thomas and Hartree. In the papers quoted a number of general results were given regarding the behaviour of electrons in any periodic field of potential. To obtain a clearer idea of the details of this behaviour with a view to the application in special problems, however, it appeared worth while to investigate the mechanics of electrons in periodic fields of potential somewhat similar to those met with in practice and of such nature that the energy values W and eigenfunctions Ψ of the wave-equation can actually be computed. It is the purpose of this article to discuss a case where the integration is possible. In Section 1 the energy values and in Section 2 the wave-functions in their dependence on the binding introduced by the potential field are discussed for the one dimensional problem. In Section 3 the matrix elements of the linear momentum, which furnish the electric current associated with the various stationary states, are well as the probability of radiative transitions between these states, are evaluated. In Section 4 the results are extended to the three dimensional case and those features considered which one may expect to find in the case of more general periodic fields of potential. Section 5 deals with some applications to physical problems.

First M87 Event Horizon Telescope Results. IV. Imaging the Central Supermassive Black Hole

Abstract: We present the first Event Horizon Telescope (EHT) images of M87, using observations from April 2017 at 1.3 mm wavelength. These images show a prominent ring with a diameter of ~40 μas, consistent with the size and shape of the lensed photon orbit encircling the "shadow" of a supermassive black hole. The ring is persistent across four observing nights and shows enhanced brightness in the south. To assess the reliability of these results, we implemented a two-stage imaging procedure. In the first stage, four teams, each blind to the others' work, produced images of M87 using both an established method (CLEAN) and a newer technique (regularized maximum likelihood). This stage allowed us to avoid shared human bias and to assess common features among independent reconstructions. In the second stage, we reconstructed synthetic data from a large survey of imaging parameters and then compared the results with the corresponding ground truth images. This stage allowed us to select parameters objectively to use when reconstructing images of M87. Across all tests in both stages, the ring diameter and asymmetry remained stable, insensitive to the choice of imaging technique. We describe the EHT imaging procedures, the primary image features in M87, and the dependence of these features on imaging assumptions.