University of Pennsylvania

About: University of Pennsylvania is a education organization based out in Philadelphia, Pennsylvania, United States. It is known for research contribution in the topics: Population & Medicine. The organization has 109318 authors who have published 257688 publications receiving 14150562 citations. The organization is also known as: UPenn & Penn.

Joint ventures: Theoretical and empirical perspectives

Abstract: This paper compares the perspectives of transaction costs and strategic behavior in explaining the motivation to joint venture. In addition, a theory of joint ventures as an instrument of organizational learning is proposed and developed. Existing studies of joint ventures are examined in light of these theories. Data on the sectoral distribution and stability of joint ventures are presented.

MDS clinical diagnostic criteria for Parkinson's disease

Abstract: This document presents the Movement Disorder Society Clinical Diagnostic Criteria for Parkinson's disease (PD). The Movement Disorder Society PD Criteria are intended for use in clinical research but also may be used to guide clinical diagnosis. The benchmark for these criteria is expert clinical diagnosis; the criteria aim to systematize the diagnostic process, to make it reproducible across centers and applicable by clinicians with less expertise in PD diagnosis. Although motor abnormalities remain central, increasing recognition has been given to nonmotor manifestations; these are incorporated into both the current criteria and particularly into separate criteria for prodromal PD. Similar to previous criteria, the Movement Disorder Society PD Criteria retain motor parkinsonism as the core feature of the disease, defined as bradykinesia plus rest tremor or rigidity. Explicit instructions for defining these cardinal features are included. After documentation of parkinsonism, determination of PD as the cause of parkinsonism relies on three categories of diagnostic features: absolute exclusion criteria (which rule out PD), red flags (which must be counterbalanced by additional supportive criteria to allow diagnosis of PD), and supportive criteria (positive features that increase confidence of the PD diagnosis). Two levels of certainty are delineated: clinically established PD (maximizing specificity at the expense of reduced sensitivity) and probable PD (which balances sensitivity and specificity). The Movement Disorder Society criteria retain elements proven valuable in previous criteria and omit aspects that are no longer justified, thereby encapsulating diagnosis according to current knowledge. As understanding of PD expands, the Movement Disorder Society criteria will need continuous revision to accommodate these advances.

Persuasion with case studies

Abstract: This article presents some helpful suggestions on how researchers can write an interesting and convincing paper based on case-based research. A single case study, unless the subject is extremely interesting, will be hard to make interesting enough to hold readers' attention. Case-based research is often criticized for having a biased sample of cases. The main object of case studies should be to provoke thought and new ideas, rather than to poke holes in existing theories. Theories are only simplifications of a much more complex reality.

Weyl and Dirac semimetals in three-dimensional solids

Abstract: Weyl and Dirac semimetals are three-dimensional phases of matter with gapless electronic excitations that are protected by topology and symmetry. As three-dimensional analogs of graphene, they have generated much recent interest. Deep connections exist with particle physics models of relativistic chiral fermions, and, despite their gaplessness, to solid-state topological and Chern insulators. Their characteristic electronic properties lead to protected surface states and novel responses to applied electric and magnetic fields. The theoretical foundations of these phases, their proposed realizations in solid-state systems, and recent experiments on candidate materials as well as their relation to other states of matter are reviewed.

Cosmological imprint of an energy component with general equation of state

Abstract: We examine the possibility that a significant component of the energy density of the Universe has an equation of state different from that of matter, radiation, or cosmological constant ( $\ensuremath{\Lambda}$). An example is a cosmic scalar field evolving in a potential, but our treatment is more general. Including this component alters cosmic evolution in a way that fits current observations well. Unlike $\ensuremath{\Lambda}$, it evolves dynamically and develops fluctuations, leaving a distinctive imprint on the microwave background anisotropy and mass power spectrum.