Membrane Transport Mechanisms Probed by Capacitance Measurements With Megahertz Voltage Clamp

We have used capacitance measurements with a 1-µs voltage clamp technique to probe electrogenic ion-transporter interactions in giant excised membrane patches, The hydrophobic ion dipicrylamine was used to test model predictions for a simple charge-moving reaction. The voltage and frequency dependencies of the apparent dipicrylamine-induced capacitance, monitored by 1-mV sinusoidal perturbations, correspond to single charges moving across 76% of the membrane field at a rate of 9500 s^(-1) at 0 mV. For the cardiac Na,K pump, the combined presence of cytoplasmic ATP-and sodium induces an increase of apparent membrane capacitance which requires the presence of extracellular sodium, The dependencies of capacitance changes on frequency, voltage, ATP, and sodium verify that phosphorylation enables a slow 300- to 900-s^(-1), pump transition (the E_1-E_2 conformational change), which in turn enables fast, electrogenic, extracellular sodium binding reactions, For the GAT1 (y-aminobutyric acid,Na,Cl) cotransporter, expressed in Xenopus oocyte membrane, we find that chloride binding from the cytoplasmic side, and probably sodium binding from the extracellular side, results in a decrease of membrane capacitance monitored with 1- to 50-kHz perturbation frequencies. Evidently, ion binding by the GAT1 transporter suppresses an intrinsic fast charge movement which mag originate from a mobility of charged residues of the transporter binding sites. The results demonstrate that fast capacitance measurements can provide new insight into electrogenic processes closely associated with ion binding by membrane transporters

Quantifying residual forest structures following retention harvesting in northeast Minnesota using Landsat sensor data

Restoration based forest management has increased significantly over the last decade across North America. Retention harvesting shows promise for restoring and maintaining forest structural and compositional diversity and also increasing resilience and adaptive capacity. This includes deliberate retention of large living trees, snags and downed woody debris (DWD). However, lack of consistent monitoring limits our understanding of the effectiveness of these strategies and our ability to adapt management accordingly. We investigate the use of readily available Landsat sensor data to remotely estimate and map DWD and basal area (BA) following retention harvesting in northeastern Minnesota, USA. We used multi-temporal winter Landsat throughout a single season to calibrate models for DWD (R²: 0.54, RMSE = 19.02 m3ha-1), total BA (R²: 0.55, RMSE = 1.85 m2ha-1), hardwood BA (R²: 0.67 RMSE =1.23 m2ha-1), and conifer BA (R²: 0.52 m2ha-1, RMSE = 0.94 m2ha-1). This novel approach uses winter imagery with varying snow accumulation to estimate and map residual forest structures. In addition to practical treatment monitoring, this research provides a valuable tracking tool from which we may deepen our long-term understanding of wildlife responses to DWD, fire and carbon dynamics, and forest nutrient cycling

Structural basis of control of inward rectifier Kir2 channel gating by bulk anionic phospholipids

Inward rectifier potassium (Kir) channel activity is controlled by plasma membrane lipids. Phosphatidylinositol-4,5-bisphosphate (PIP(2)) binding to a primary site is required for opening of classic inward rectifier Kir2.1 and Kir2.2 channels, but interaction of bulk anionic phospholipid (PL(−)) with a distinct second site is required for high PIP(2) sensitivity. Here we show that introduction of a lipid-partitioning tryptophan at the second site (K62W) generates high PIP(2) sensitivity, even in the absence of PL(−). Furthermore, high-resolution x-ray crystal structures of Kir2.2[K62W], with or without added PIP(2) (2.8- and 2.0-Å resolution, respectively), reveal tight tethering of the C-terminal domain (CTD) to the transmembrane domain (TMD) in each condition. Our results suggest a refined model for phospholipid gating in which PL(−) binding at the second site pulls the CTD toward the membrane, inducing the formation of the high-affinity primary PIP(2) site and explaining the positive allostery between PL(−) binding and PIP(2) sensitivity

Castable Bulk Metallic Glass Strain Wave Gears: Towards Decreasing the Cost of High-Performance Robotics

The use of bulk metallic glasses (BMGs) as the flexspline in strain wave gears (SWGs), also known as harmonic drives, is presented. SWGs are unique, ultra-precision gearboxes that function through the elastic flexing of a thin-walled cup, called a flexspline. The current research demonstrates that BMGs can be cast at extremely low cost relative to machining and can be implemented into SWGs as an alternative to steel. This approach may significantly reduce the cost of SWGs, enabling lower-cost robotics. The attractive properties of BMGs, such as hardness, elastic limit and yield strength, may also be suitable for extreme environment applications in spacecraft

Hopf algebras of dimension 2p^2

Let H be a non-semisimple Hopf algebra of dimension 2p^2 over an algebraically closed field of characteristic zero, where p is an odd prime. We prove that H or H^* is pointed, which completes the classification for Hopf algebras of these dimensions.Comment: 16pp Latex; Corrected typos and added references; Made a correction to the proof of Lemma 2.2 in the version (V1

Dalton State College APEX Calculus

This text for Analytic Geometry and Calculus I, II, and III is a Dalton State College remix of APEX Calculus 3.0. The text was created through a Round Six ALG Textbook Transformation Grant. Topics covered in this text include: Limits Derivatives Integration Antidifferentiation Sequences Vectors Files can also be downloaded on the Dalton State College GitHub: https://github.com/DaltonStateCollege/calculus-text/blob/master/Calculus.pdf Accessible files with optical character recognition (OCR) and auto-tagging provided by the Center for Inclusive Design and Innovation.https://oer.galileo.usg.edu/mathematics-textbooks/1016/thumbnail.jp

Reducing antioxidant capacity evaluated by means of a controlled potential oxidative attack

An analytical method suitable for an antioxidant sensor is presented following the response of these substances to an extensive oxidative attack imposed by electrochemical means. The electrochemical assay simulates the action of a reactive oxygen species (ROS) by means of electrolyses carried out at a potential which is settled at the formal potential of the ROS. The antioxidant activities of trolox and ascorbic, gallic and caffeic acids and of mixtures these antioxidants was estimated from the charge required for the complete oxidation of the antioxidants from assays where the oxidative attack by O2 and by O2 were simulated.Fundação para a Ciência e Tecnologia (FCT)Centro de Química da Universidade do Minh

Analytic Geometry and Calculus I, II, & III (Dalton)

This Grants Collection for Analytic Geometry and Calculus I, II, & III was created under a Round Six ALG Textbook Transformation Grant. Affordable Learning Georgia Grants Collections are intended to provide faculty with the frameworks to quickly implement or revise the same materials as a Textbook Transformation Grants team, along with the aims and lessons learned from project teams during the implementation process. Documents are in .pdf format, with a separate .docx (Word) version available for download. Each collection contains the following materials: Linked Syllabus Initial Proposal Final Reporthttps://oer.galileo.usg.edu/mathematics-collections/1024/thumbnail.jp