Transport, Magnetic, and Thermal Properties of La 0.7

We report the transport, magnetic, and thermal properties of La0.7Ca0.24Sr0.06MnO3 single crystal. It was prepared using floating zone technique used under oxygen pressure of 1 bar with a typical growth rate of 1 mm/hr. The resistivity data shows the metal to insulator transition (M-I) occuring at TMI=290 K along the c-axis and at TMI=280 K along the ab-plane. It is observed that the TMI is higher along the c-axis as compared to that in the ab-plane, thus indicating that more favorable hoping of electrons is along the c-axis. From bolometric application point of view, the temperature coefficient of resistance (TCR) is found to be ~28% K−1. The ac-susceptibility measurement shows that this material exhibits ferromagnetic to paramagnetic transition temperature (TC) 277 K. Sharp peak around this temperature in heat capacity data indicates the onset of long-range ordering. The entropy change associated with this transition is found to be 2.3 J/mol K

Structural Neuroimaging to Generate Biomarkers of Response to Deep Brain Stimulation

Deep Brain Stimulation (DBS) is the use of continuous, typically high-frequency direct electrical current, delivered through neurosurgically implanted electrodes, aimed at altering activity within dysfunctional brain circuits. DBS is now an established therapy for several neurological conditions such as Parkinson’s Disease, dystonia, and tremor, and is emerging as a viable therapy in several others including depression and disorders of memory. However, the response to DBS is highly variable across individuals with the same disease, a fact often attributed to clinical factors such as age or illness severity, or to technical factors such as DBS electrode position. The central hypothesis underlying this thesis is that brain structure, as evaluated by structural magnetic resonance imaging (MRI), is also a key factor influencing clinical response to DBS therapy across various neurological and psychiatric diseases. The specific aims of the thesis project were to determine: 1) whether pre-DBS brain structure relates to, or predicts, eventual clinical response to DBS; and 2) whether ongoing DBS therapy produces detectable structural changes in the brain that may influence clinical response. In study #1, we demonstrate that in patients undergoing DBS of the subcallosal cingulate region (SCG) for depression, future response to DBS is predicted by pre-treatment variations in brain structure, especially volume of the SCG, thalamus, and the total volume of cortical grey matter. Studies #2 and #3 provide preliminary, first-in-human evidence, in two different patient populations (Parkinson’s Disease and Alzheimer’s Disease), that DBS is associated with structural neuroplasticity demonstrable on post-operative MRI scans, and may even result in the reversal of focal atrophy in selected patients. Study #4, however, illustrates the difficulties inherent in replicating these results on a larger scale because of methodological concerns related to the reliability and concordance of automated algorithms currently used to analyze structural neuroimaging data. Despite these concerns, this thesis illustrates that structural neuroimaging with MRI indeed has the potential to generate clinically useful biomarkers of response to DBS therapy, which may ultimately influence patient selection for DBS, guide DBS programming, and inform prognosis after DBS implantation.Ph.D

Sicyopterus garra Hora, 1925, a valid species of sicydiine goby from the Andaman Islands, India

International audienc

Deep Brain Stimulation Target Selection for Parkinson's Disease

During the DBS Canada Day symposium held in Toronto July 4-5, 2014, the scientific committee invited experts to discuss three main questions on target selection for deep brain stimulation (DBS) of patients with Parkinson's disease (PD). First, is the subthalamic nucleus (STN) or the globus pallidus internus (GPi) the ideal target? In summary, both targets are equally effective in improving the motor symptoms of PD. STN allows a greater medications reduction, while GPi exerts a direct antidyskinetic effect. Second, are there further potential targets? Ventral intermediate nucleus DBS has significant long-term benefit for tremor control but insufficiently addresses other motor features of PD. DBS in the posterior subthalamic area also reduces tremor. The pedunculopontine nucleus remains an investigational target. Third, should DBS for PD be performed unilaterally, bilaterally or staged? Unilateral STN DBS can be proposed to asymmetric patients. There is no evidence that a staged bilateral approach reduces the incidence of DBS-related adverse events

Brain retraction and thickness of cerebral neocortex: an automated technique for detecting retraction-induced anatomic changes using magnetic resonance imaging.

BACKGROUND: Treating deep-seated cerebral lesions often requires retracting the brain. Retraction, however, causes clinically significant postoperative neurological deficits in 3% to 9% of intracranial cases. OBJECTIVE: This pilot study used automated analysis of postoperative magnetic resonance images (MRIs) to determine whether brain retraction caused local anatomic changes to the cerebral neocortex and whether such changes represented sensitive markers for detecting brain retraction injury. METHODS: Pre- and postoperative maps of whole-brain cortical thickness were generated from 3-dimensional MRIs of 6 patients who underwent selective amygdalohippocampectomy for temporal lobe epilepsy (5 left hemispheres, 1 right hemisphere). Mean cortical thickness was determined in the inferior temporal gyrus (ITG test), where a retractor was placed during surgery, and in 2 control gyri-the posterior portion of the inferior temporal gyrus (ITG control) and motor cortex control. Regions of cortical thinning were also compared with signs of retraction injury on early postoperative MRIs. RESULTS: Postoperative maps of cortical thickness showed thinning in the inferior temporal gyrus where the retractor was placed in 5 patients. Postoperatively, mean cortical thickness declined from 4.1 +/- 0.4 mm to 2.9 +/- 0.9 mm in ITG test (P = .03) and was unchanged in the control regions. Anatomically, the region of neocortical thinning correlated with postoperative edema on MRIs obtained within 48 hours of surgery. CONCLUSION: Postoperative MRIs can be successfully interrogated for information on cortical thickness. Brain retraction is associated with chronic local thinning of the neocortex. This automated technique may be sensitive enough to detect regions at risk for functional impairment during craniotomy that cannot be easily detected on postoperative structural imaging