Ionic Coulomb blockade controls the current in a short narrow carbon nanotube.

We use all-atom molecular dynamics simulations to investigate ionic conduction in a short, charged, single-wall carbon nanotube. They reveal ionic Coulomb blockade (ICB) oscillations in the current as a function of the fixed charge on the wall, and an associated occupancy staircase. Current peaks related to fluctuations around the 2 → 1 and 1 → 0 steps in occupancy are clearly resolved, in agreement with ICB theory.

Effects of Augmented Reality on Thoracolumbar Pedicle Screw Instrumentation Across Different Levels of Surgical Experience.

Objective: Augmented reality (AR) is an emerging technology that may accelerate skill acquisition and improve accuracy of thoracolumbar pedicle screw placements. We aimed to quantify the relative assistance of AR compared with freehand (FH) pedicle screw accuracy across different surgical experience levels.

Methods: A spine fellowship-trained and board-certified attending neurosurgeon, postgraduate year 4 neurosurgery resident, and second-year medical student placed 32 FH and 32 AR-assisted thoracolumbar pedicle screws in 3 cadavers.

Improved Accuracy and Lowered Learning Curve of Ventricular Targeting Using Augmented Reality-Phantom and Cadaveric Model Testing.

Background: Augmented reality (AR) has demonstrated significant potential in neurosurgical cranial, spine, and teaching applications. External ventricular drain (EVD) placement remains a common procedure, but with error rates in targeting between 10% and 40%.

Objective: To evaluate Novarad VisAR guidance system for the placement of EVDs in phantom and cadaveric models.

Augmented Reality Spine Surgery Navigation: Increasing Pedicle Screw Insertion Accuracy for Both Open and Minimally Invasive Spine Surgeries.

Study Design: Collectively, seven cadavers were instrumented with 124 thoracolumbar pedicle screws using VisAR augmented reality/guidance. Sixty-five screws were inserted into four donors using open dissection spine surgery. Fifty-nine screws were positioned in three donors with a minimally invasive spine surgery (MISS) procedure.

The application of augmented reality-based navigation for accurate target acquisition of deep brain sites: advances in neurosurgical guidance.

Objective: The objective of this study is to quantify the navigational accuracy of an advanced augmented reality (AR)-based guidance system for neurological surgery, biopsy, and/or other minimally invasive neurological surgical procedures.

Methods: Five burr holes were drilled through a plastic cranium, and 5 optical fiducials (AprilTags) printed with CT-visible ink were placed on the frontal, temporal, and parietal bones of a human skull model. Three 0.

Field-Dependent Dehydration and Optimal Ionic Escape Paths for CN Membranes.

Most analytic theories describing electrostatically driven ion transport through water-filled nanopores assume that the corresponding permeation barriers are bias-independent. While this assumption may hold for sufficiently wide pores under infinitely small bias, transport through subnanometer pores under finite bias is difficult to interpret analytically. Given recent advances in subnanometer pore fabrication and the rapid progress in detailed computer simulations, it is important to identify and understand the specific field-induced phenomena arising during ion transport.

Physics of Selective Conduction and Point Mutation in Biological Ion Channels.

We introduce a statistical and linear response theory of selective conduction in biological ion channels with multiple binding sites and possible point mutation. We derive an effective grand-canonical ensemble and generalized Einstein relations for the selectivity filter, assuming strongly coordinated ionic motion, and allowing for ionic Coulomb blockade. The theory agrees well with data from the KcsA K^{+} channel and a mutant.

Application of a Statistical and Linear Response Theory to Multi-Ion Na Conduction in NaChBac.

Biological ion channels are fundamental to maintaining life. In this manuscript we apply our recently developed statistical and linear response theory to investigate Na+ conduction through the prokaryotic Na+ channel NaChBac. This work is extended theoretically by the derivation of ionic conductivity and current in an electrochemical gradient, thus enabling us to compare to a range of whole-cell data sets performed on this channel.

Use of augmented reality for image-guided spine procedures.

Purpose: Because of its ability to superimpose imaging data on a patient, while anchoring the user's view to the immediate surroundings, augmented reality (AR) has the potential to dramatically improve the accuracy and reduce the time required for preoperative planning and performance of minimally invasive spine surgeries and procedures. Described and reported herein is the direct clinical application of AR navigation on a series of common percutaneous image-guided spine procedures.

Materials And Methods: AR, including a "virtual needle" (VN) asset, was used to guide and navigate a total of 18 procedures performed on 10 patients.

Ionic Coulomb blockade and the determinants of selectivity in the NaChBac bacterial sodium channel.

Mutation-induced transformations of conductivity and selectivity in NaChBac bacterial channels are studied experimentally and interpreted within the framework of ionic Coulomb blockade (ICB), while also taking account of resonant quantised dehydration (QD) and site protonation. Site-directed mutagenesis and whole-cell patch-clamp experiments are used to investigate how the fixed charge Q at the selectivity filter (SF) affects both valence selectivity and same-charge selectivity. The new ICB/QD model predicts that increasing ∣Q∣ should lead to a shift in selectivity sequences toward larger ion sizes, in agreement with the present experiments and with earlier work.

Outcomes of Yttrium-90 Radioembolization for Unresectable Combined Biphenotypic Hepatocellular-Cholangiocarcinoma.

Purpose: To evaluate outcomes of yttrium-90 radioembolization in patients with combined biphenotypic hepatocellular-cholangiocarcinoma (cHCC-CC).

Materials And Methods: A retrospective review of patients with biopsy-confirmed cHCC-CC treated with yttrium-90 radioembolization between 2012 and 2018 was performed. Twenty-two patients with cHCC-CC (mean age 65.

Exploring the pore charge dependence of K and Cl permeation across a graphene monolayer: a molecular dynamics study.

Selective permeation through graphene nanopores is attracting increasing interest as an efficient and cost-effective technique for water desalination and purification. In this work, using umbrella sampling and molecular dynamics simulations with constant electric field, we analyze the influence of pore charge on potassium and chloride ion permeation. As pore charge is increased, the barrier of the potential of mean force (PMF) gradually decreases until it turns into a well split in two subminima.

The use of a binary chelate formulation: Could gadolinium based linear contrast agents be rescued by the addition of zinc selective chelates?

Tissue and bone retention of gadolinium based contrast agents (GBCAs) has become a clinical concern because of the potential short and long term toxic effects of free gadolinium. This is a critical problem for most open-chain agents that more readily transmetallate in vivo, in comparison to macrocyclic compounds. Gadolinium diethylene tri-aminepentaacetic acid bis-glucosamide (Gd-DTPA-BIGA) is an experimental, open-chain contrast agent which has a significantly increased relaxivity coefficient in comparison to other GBCAs.

Whole-Body Computed Tomography-Based Body Mass and Body Fat Quantification: A Comparison to Hydrostatic Weighing and Air Displacement Plethysmography.

Objective: We correlate and evaluate the accuracy of accepted anthropometric methods of percent body fat (%BF) quantification, namely, hydrostatic weighing (HW) and air displacement plethysmography (ADP), to 2 automatic adipose tissue quantification methods using computed tomography (CT).

Methods: Twenty volunteer subjects (14 men, 6 women) received head-to-toe CT scans. Hydrostatic weighing and ADP were obtained from 17 and 12 subjects, respectively.

Volumetric analysis of central body fat accurately predicts incidence of diabetes and hypertension in adults.

Background: Central adipose tissue is appreciated as a risk factor for cardiometabolic disorders. The purpose of this study was to determine the efficacy of a volumetric 3D analysis of central adipose tissue in predicting disease. Full body computerized tomography (CT) scans were obtained from 1225 female (518) and male (707) subjects, aged 18-88.

Comparison of Gd(DTPA-BMA) (Omniscan) versus Gd(HP-DO3A) (ProHance) relative to gadolinium retention in human bone tissue by inductively coupled plasma mass spectroscopy.

Objective: The objective of this study was to determine the gadolinium (Gd) concentration remaining in human bone tissue after administration of standard clinical doses of 2 Gd-based contrast agents: ProHance and Omniscan.

Materials And Methods: After administration of 0.1 mmol/kg of Gd chelate to patients undergoing hip replacement surgery, bone specimens were collected and analyzed, and compared with an age-matched control population without a history of Gd chelate administration.

Basic principles of magnetic resonance imaging.

We have come full circle from spinning quarks to 3D medical images. The bulk of MRI is now performed using slice-selective gradients, during which RF energy is applied to excite the hydrogen nuclei. By stepping a phase-encoding gradient during each TR and using a frequency-encoding gradient as the data are sampled, the 3D human object can be reduced to many individual points or voxels.

Comparison of Gd DTPA-BMA (Omniscan) versus Gd HP-DO3A (ProHance) retention in human bone tissue by inductively coupled plasma atomic emission spectroscopy.

Rationale And Objectives: Human bone tissue was collected following administration of a clinical dose of gadolinium chelate (0.1 mmol per kg) to patients undergoing hip joint replacement surgery to determine if measurable differences in Gd deposition occur between 2 widely available magnetic resonance contrast agents.

Materials And Methods: Gd HP-DO3A (ProHance), Gd DTPA-BMA (Omniscan), and an age-matched control population without history of gadolinium chelate administration were compared.

Human in vivo comparative study of zinc and copper transmetallation after administration of magnetic resonance imaging contrast agents.

Rationale And Objectives: The authors compare in vivo transmetallation of three magnetic resonance contrast agents in humans in terms of their kinetic stability.

Methods: Blood and urine samples were taken before and after the intravenous injection of gadolinium (Gd)-HP-DO3A, Gd-DTPA, or Gd-DTPA-BMA at 0.1 mmol/kg to healthy volunteers.

Comparative transmetallation kinetics and thermodynamic stability of gadolinium-DTPA bis-glucosamide and other magnetic resonance imaging contrast media.

Rationale And Objectives: The relative stability and selectivity of magnetic resonance (MR) imaging contrast agents were compared with in vitro transmetallation and ligand competition reactions.

Materials And Methods: A gadolinium (Gd)-DTPA-BIGA, Gd-DTPA-BMA, Gd-DTPA, or Gd-HP-DO3A solution was mixed with an equimolar solution of zinc (Zn) citrate in 1:1 volume ratio at pH 7.4 in a transmetallation assay.

Pseudotumor cerebri: CT findings and correlation with vision loss.

Objective: The purpose of this study was to determine if orbital and cerebral CT can be used to distinguish normal patients from those with pseudotumor cerebri, and to correlate CT findings with the severity of visual impairment.

Subjects And Methods: Seventeen patients with a clinical diagnosis of pseudotumor cerebri were compared with 20 age- and sex-matched control subjects. Thin-section coronal and axial CT scans of the orbit and whole-brain axial CT scans were available for all subjects.

Biodistribution and magnetic resonance imaging of cross-linked DTPA polysaccharides.

Large polysaccharide complexes, cross-linked with DTPA and chelated with gadolinium have been tested for various potential uses for magnetic resonance imaging (MRI) in rats. Biodistribution and pharmacokinetic data for several of the soluble polymers are presented and compared with Gd-DTPA and GdCl3. By varying the initial polysaccharide length and ratio of DTPA to glucose units, polymers of molecular weights (mol wt) from 17,000 to several million were formed, giving soluble material, gels, or particles.

Cross-linked DTPA polysaccharides for magnetic resonance imaging. Synthesis and relaxation properties.

An attempt was made to develop a macromolecular paramagnetic contrast agent that would be easily and inexpensively synthesized, low in toxicity, and quickly eliminated from the body after completion of the desired imaging studies. Under more rigorous conditions than attainable with proteins, the bis-anhydride of DTPA was reacted in anhydrous, hot DMSO with dextrans ranging in size from 17,000 molecular weight (MW) to 150,000 MW in various ratios of DTPA to glucose units from 1:1 to 1:40. Up to several hundred DTPA units per saccharide complex could be attached with this technique.

MR contrast agents: an overview.

In this article an overview of current and potential MR contrast agents is given. The mechanism of action of contrast agents and their relationship to both T1 and T2 relaxation are explored. Both paramagnetic and superparamagnetic substances are considered.