Distinguishing a Minimalist Role for Grand Theorizing

A major theoretical shortcoming in international relations (IR) is the lack of any semblance of a common understanding regarding the role of grand theory. This article argues that explicit theoretical work of this sort is useful, but that a search for a single overarching grand theory to guide inquiry is misguided and that the primary business of IR is to form and evaluate middle-range theories

Correspondence: debating China's rise and the future of U.S. power

Parkinson’s disease (PD) is the second most common neurodegenerative disease worldwide and the most common movement disorder. A defining pathologic feature of PD is the progressive death of dopaminergic neurons in a basal ganglia nucleus termed the substantia nigra (SN). Another hallmark feature of PD pathology is the presence of Lewy bodies and Lewy neurites, which are cellular inclusions with aggregated protein depositions, representing pathology in neuronal cell bodies and neuritic processes. Recently, epidemiological and genetic studies support roles for neuroinflammation in the progression of PD. Two types of cells that play a critical role in regulating neuroinflammation are microglia and astrocytes, which are activated in the basal ganglia of PD patients. Studies within this dissertation characterized activation of microglial cells by alpha-synuclein (α-synuclein), the most abundant protein in Lewy bodies, which has been implicated in PD pathogenesis. To garner insights into molecular mechanisms associated with astrocyte proliferation and activation, genomic alterations during developmental stages of astrocytes were examined since they are likely to recapitulate the reactivity associated with gliosis in PD brain. The activation of these glial cells and pathology of neurons in the basal ganglia causes the hallmark symptoms of PD. The symptoms of PD are termed parkinsonism. These are thought to result, at least in part, from alterations in the balance of output of the neostriatal efferent neurons, due to the loss of dopaminergic neuronal innervation of these cells. Phosphodiesterase 10A (PDE10A) is preferentially expressed in neostriatal efferent pathways and PDE10A inhibitors (PDE10i) have been shown to target dopamine signaling mechanisms. Studies here have utilized PDE10i to understand the balance of activation of medium spiny neurons in the indirect pathway versus activation of the direct pathway, since recent findings show PDE10i lead to a decrease in thalamic drive to the motor cortex, a primary symptom of PD. In conclusion, the aims of this dissertation sought to identify neuroinflammatory mechanisms within activated microglia in response to α-synuclein and proliferating astrocytes. Also, this work evaluated an inhibition of PDE10A in neurons within a region important to the progression of PD

Climate Change and Biosphere Response: Unlocking the Collections Vault

Natural history collections (NHCs) are an important source of the long-term data needed to understand how biota respond to ongoing anthropogenic climate change. These include taxon occurrence data for ecological modeling, as well as information that can be used to reconstruct mechanisms through which biota respond to changing climates. The full potential of NHCs for climate change research cannot be fully realized until high-quality data sets are conveniently accessible for research, but this requires that higher priority be placed on digitizing the holdings most useful for climate change research (e.g., whole-biota studies, time series, records of intensively sampled common taxa). Natural history collections must not neglect the proliferation of new information from efforts to understand how present-day ecosystems are responding to environmental change. These new directions require a strategic realignment for many NHC holders to complement their existing focus on taxonomy and systematics. To set these new priorities, we need strong partnerships between NHC holders and global change biologists

Spin-dynamics of the low-dimensional magnet (CH3)2NH2CuCl3

Dimethylammonium copper (II) chloride (also known as DMACuCl3 or MCCL) is a low dimensional S=1/2 quantum spin system proposed to be an alternating ferro-antiferromagnetic chain with similar magnitude ferromagnetic (FM) and antiferromagnetic (AFM) exchange interactions. Subsequently, it was shown that the existing bulk measurements could be adequately modeled by considering DMACuCl3 as independent AFM and FM dimer spin pairs. We present here new inelastic neutron scattering measurements of the spin-excitations in single crystals of DMACuCl3. These results show significant quasi-one-dimensional coupling, however the magnetic excitations do not propagate along the expected direction. We observe a band of excitations with a gap of 0.95 meV and a bandwidth of 0.82 meV.Comment: 3 pages, 2 figures included in text, submitted to proceedings of International Conference on Neutron Scattering, December 200

SpinWaves in the Frustrated Kagomé Lattice Antiferromagnet KFe\u3csub\u3e3\u3c/sub\u3e(OH)\u3csub\u3e6\u3c/sub\u3e(SO\u3csub\u3e4\u3c/sub\u3e)\u3csub\u3e2\u3c/sub\u3e

The spin wave excitations of the S = 5/2 kagomé lattice antiferromagnet KFe3(OH)6(SO4)2 have been measured using high-resolution inelastic neutron scattering. We directly observe a flat mode which corresponds to a lifted ‘‘zero energy mode,’’ verifying a fundamental prediction for the kagomé lattice. A simple Heisenberg spin Hamiltonian provides an excellent fit to our spin wave data. The antisymmetric Dzyaloshinskii-Moriya interaction is the primary source of anisotropy and explains the low-temperature magnetization and spin structure