Verification and Temperature-Dependent Rectification by HBQ, the Smallest Unimolecular Donor-Acceptor Rectifier.

Five years ago, rectification of electrical current was found in 4'-bromo-3,4-dicyano-2',5'-dimethoxy-[1,1'-biphenyl]-2,5-dione (1), a hemibiquinone (which we will call either 1 or HBQ) that has a very small working length (1.1 nm). Monolayers of HBQ on AuTS were detected by "nanodozing" atomic force microscopy (AFM) and were contacted with two types of top electrodes: either cold Au or eutectic Ga-In. Here, we describe cyclic voltammetry of a self-assembled monolayer (SAM) of HBQ and its orientation on a gold substrate with angle-resolved X-ray photoelectron spectroscopy. New measurements of its rectification as a monolayer as a function of bias range and temperature confirm and prove that HBQ is truly the smallest donor-acceptor rectifier and provide some insight into the mechanism of rectification.

Evaluation of a novel process for selecting advanced pharmacy practice experiences.

INTRODUCTION: Matching an increasing number of pharmacy students with a limited number of advanced pharmacy practice experience (APPE) sites has become challenging for pharmacy schools. Selective tiered optimization (STO), a process for matching students with competitive APPE electives, was implemented by The University of Mississippi School of Pharmacy (UMSOP) in 2015 to address these concerns. This pilot study sought to evaluate student and preceptor satisfaction with the process. METHODS: Electronic surveys were sent to students enrolled in APPEs and individuals who precepted APPE students at the UMSOP from 2016 to 2019. The surveys were designed to gauge satisfaction with STO's process, goals, utility, and fairness. RESULTS: There were 63 responses from 149 preceptors (42% response rate) and 70 respondents from 314 students (22% response rate). Overall, both students and preceptors expressed satisfaction and found value in participating in STO. Both groups indicated that the benefit they received from participating in STO outweighed the extra effort required. Preceptors indicated that students who participated in STO were of higher quality and more focused, hardworking, and interested than those who did not participate. CONCLUSIONS: Respondents were satisfied with the STO process and experience. The process was perceived by preceptors to be fair for all students and worthwhile for its participants. Our results also demonstrated that this process is effective for easing the competitive APPE selection process. Schools and colleges of pharmacy should consider utilizing this process to alleviate applicable challenges with APPE selection.

Comparison of Semi-Automated Versus Manual Quantitative Right Ventricular Assessment in Hypoplastic Left Heart Syndrome.

Quantitative echocardiographic evaluation is important for systemic right ventricles, but its asymmetric shape makes this challenging and time consuming when performed manually. Semi-automated software could make these quantitative measures easier to accomplish in the clinical setting. We hypothesized that semi-automated software would approximate manual measures of right ventricular size and function. Children with hypoplastic left heart who had echocardiograms were prospectively identified. These measurements were performed using manual and semi-automated techniques: end-diastolic and end-systolic area, fractional area change (FAC), dimensions (longitudinal, basal and mid-cavitary diameters), and tricuspid annular plane systolic excursion (TAPSE). Agreement between measures was evaluated. Sixty-three echocardiograms were analyzed. Intra- and inter-observer reliability was acceptable and similar between methods except that inter-observer reliability for the manual method was superior for TAPSE. Correlation between methods was high (r > 0.9, p < 0.001) for most of the measures. Correlation for FAC was r = 0.79, and for TAPSE the correlation was r = 0.61 (both p < 0.001). The percent relative difference between manual and semi-automated methods was less than 6% for most measures. End-systolic area and FAC had a relative difference of 10% and 11% respectively. The only measure with substantial bias between the manual and semi-automated methods was TAPSE which had a relative difference of 52%. EchoInsight® semi-automated software provides similar measures of right ventricular dimensions and FAC in patients with hypoplastic left heart compared to manual measures. Measures of TAPSE do not correlate well between manual and semi-automated methods. Further research is warranted on the use of semi-automated analyses in this patient population.

Evidence-based diagnosis and treatment of cervical spine disorders.

Neck pain from cervical spine disorders is the second-leading cause of musculoskeletal disorders. Neck pain can exist alone or with the presence of upper extremity symptoms. This review of evidence-based guidelines assists the provider in identifying and treating various cervical disorders.

Quo vadis, unimolecular electronics?

This paper reviews the present status of unimolecular electronics (UME). The field started in the 1970s with a hope that some day organic molecules (∼2 nm in size), when used as electronic components, would challenge Si-based inorganic electronics in ultimate-high-density integrated circuits. The technological push to ever smaller inorganic device sizes (Moore's "law") was driven by a profit motive and by vast investments. UME, the underfunded pauper, may have lost that "race to the bottom", but some excellent science is left to be done.

Observation of current rectification by a new asymmetric iron(iii) surfactant in a eutectic GaIn|LB monolayer|Au sandwich.

In this paper we expand on the search for molecular rectifiers of electrical current and report on a hexacoordinate metallosurfactant [FeIII(LN3O)(OMe)2], where (LN3O)- is the deprotonated form of the new asymmetric ligand 2-((E)-((4,5-bis(2-methoxyethoxy)-2-(((E)-pyridin-2-ylmethylene)amino)phenyl)imino)methyl)-4,6-di-tert-butyl-phenol. This species rectifies current when deposited as a Langmuir-Blodget film in a "EGaIn/Ga2O3|LB|Au" sandwich with rectification ratios ranging from 25 to 300 at 1 Volt.

Modeling the structural origins of drug resistance to isoniazid via key mutations in Mycobacterium tuberculosis catalase-peroxidase, KatG.

WHO reported 10.4 million new tuberculosis (TB) cases and 1.8 million deaths in 2015, making M. tuberculosis the most successful human pathogen with highest mortality among infectious diseases [1,2]. Drug-resistant TB is a major threat to global TB control [2,3]. Recently Torres et al. [4] identified 14 novel substitutions in M. tuberculosis-KatG (the enzyme associated with resistance to isoniazid-an important first-line anti-TB drug) and demonstrated that 12 of the 14 can cause INH-resistance in M. smegmatis. This study presents an in silico structure-based analysis of these 14 amino acid substitutions using homology models and x-ray crystal structures (when available) in M. tuberculosis. Our models demonstrate that several of these mutations cluster around three openings in the KatG tertiary structure which appear to initiate channels to the heme group at the catalytic center of the enzyme. We studied the effects of these mutations on the tertiary structure of KatG, focusing on conformational changes in the three channels in the protein structure. Our results suggest that the 14 novel mutations sufficiently restrict one or more of these access channels, thus potentially preventing INH from reaching the catalytic heme. These observations provide valuable insights into the structure-based origins of INH resistance and provide testable hypotheses for future experimental studies.

Structure-based analysis of Bacilli and plasmid dihydrofolate reductase evolution.

Dihydrofolate reductase (DHFR), a key enzyme in tetrahydrofolate-mediated biosynthetic pathways, has a structural motif known to be highly conserved over a wide range of organisms. Given its critical role in purine and amino acid synthesis, DHFR is a well established therapeutic target for treating a wide range of prokaryotic and eukaryotic infections as well as certain types of cancer. Here we present a structural-based computer analysis of bacterial (Bacilli) and plasmid DHFR evolution. We generated a structure-based sequence alignment using 7 wild-type DHFR x-ray crystal structures obtained from the RCSB Protein Data Bank and 350 chromosomal and plasmid homology models we generated from sequences obtained from the NCBI Protein Database. We used these alignments to compare active site and non-active site conservation in terms of amino acid residues, secondary structure and amino acid residue class. With respect to amino acid sequences and residue classes, active-site positions in both plasmid and chromosomal DHFR are significantly more conserved than non-active site positions. Secondary structure conservation was similar for active site and non-active site positions. Plasmid-encoded DHFR proteins have greater degree of sequence and residue class conservation, particularly in sequence positions associated with a network of concerted protein motions, than chromosomal-encoded DHFR proteins. These structure-based were used to build DHFR specific phylogenetic trees from which evidence for horizontal gene transfer was identified.

Evidence-based practice guidelines for the diagnosis and treatment of lumbar spinal conditions.

Low back pain remains one of the most common patient complaints. It can exist alone or with the presence of lower extremity symptoms. Review of evidence-based guidelines will assist primary care providers in the identification and treatment of various lumbar disorders in addition to ruling out specific lumbar spinal pathologies.

Janus Reversal and Coulomb Blockade in Ferrocene-Perylenebisimide and N,N,N',N'-Tetramethyl-para-phenylenediamine-Perylenebisimide D-σ-A Rectifiers.

Sandwiches "EGaIn|Ga2O3|LB monolayer of 2|Au" and "EGaIn|Ga2O3|LB monolayer of 3|Au" rectify. They are formed from a Langmuir-Blodgett (LB) monolayer of 2 or 3 transferred onto thermally evaporated gold. Molecules 2 and 3 are of the donor-sigma-acceptor (D-σ-A) type and have the same perylenebisimide (PBI) acceptor as previously studied molecule 1. Molecule 1 has the weak donor pyrene, 2 has the good donor ferrocene, and 3 has the very strong donor N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD). All three molecules have a long swallowtail ending in a thioacetyl group, which ensures slow chemisorption onto the Au electrode. These molecules were contacted directly by a gallium indium eutectic (EGaIn) drop, covered by a defective oxide Ga2O3 layer. As before for 1, the direction of rectification for 2 is bias-dependent. In the ±1.0 V range, the rectification is at positive V, with a rectification ratio (RR) that is initially greater than 5 and then decreases on successive scans to 2, while the currents decrease by as much as 2 orders of magnitude. In the ±2.5 V range, the rectification direction for 2 reverses, while upon repeated scanning the rectification ratio (in the negative direction) increases and the currents decrease. For molecule 3, both directions have a charge-trapped state (Coulomb blockade) leading to Voffset in both biases, but at high potentials rectification set is, with large RR (up to 2,800) at ±2.5 V.

Surprisingly Big Rectification Ratios for a Very Small Unimolecular Rectifier.

To shrink electrical circuits beyond the looming practical limits of Moore's "Law", it has been a common goal to create carbon-based components. Here is the first example of a new class of donor-σ-acceptor rectifiers: hemibiquinones (HBQs). HBQs possess donor and acceptor moieties that are electronically isolated by inter-ring torsion. A HBQ-dinitrile self-assembles on a template-stripped gold surface through directed chemisorption, forming a 1.1 nm-thick monolayer. Rectification is measured through the monolayer or single molecules by using three different top electrode arrangements. Even though the HBQs are composed of relatively weak electrophores, rectification ratios ranging from 5 to 160 were observed at 2.5 V.

Crystal structure of 4,4'-di-bromo-2',5'-dimeth-oxy-[1,1'-biphen-yl]-2,5-dione (BrHBQBr).

In the title compound, C14H10Br2O4, the dihedral angle between the aromatic rings is 67.29 (19)°. Both meth-oxy-group C atoms lie close to the plane of their attached ring [deviations = -0.130 (4) and 0.005 (5) Å]. In the crystal, mol-ecules pack in a centrosymmetric fashion and inter-act via a mixture of weak π-π stacking inter-actions [centroid-centoid separations = 4.044 (2) and 4.063 (3) Å], weak C-H⋯O hydrogen bonding, and Br⋯Br halogen bonding. This induces a geometry quite different than that predicted by theory.

Spondylolysis and spondylolisthesis: what the primary care provider should know.

PURPOSE: To provide nurse practitioners (NPs) with an overview of spondylolysis and spondylolisthesis, including the pathophysiology and etiology, incidence and prevalence, clinical presentation, diagnosis and differentials, management, and prognosis for these conditions. DATA SOURCES: Selected research, reviews, and clinical articles, and the authors' experience. CONCLUSIONS: Spondylolysis and spondylolisthesis are two common and confusing diagnoses identified by healthcare providers in the treatment of low back pain. Symptoms can vary depending on the degree of disarticulation with radiculopathy occurring in advanced grades of spondylolisthesis. Standing, lateral lumbosacral radiographs remain the gold standard for diagnosis. The majority of patients will improve with conservative treatments. Surgical options are warranted after 6 months of failed conservative treatments for patients with radiculopathy, neurogenic claudication, progressive neurological deficits, high-grade slips, or bladder and bowel symptoms. IMPLICATIONS FOR PRACTICE: NPs can distinguish these diagnoses and perform appropriate conservative management prior to referral to specialists for surgical evaluation. NPs are important providers in interdisciplinary care by assisting patients with both psychosocial and physical management of their back pain.

Unimolecular amplifier: principles of a three-terminal device with power gain.

A single molecule composed of three linked moieties can function as an amplifier of electrical current, when certain conditions are met by the molecular orbitals of the three component parts. This device should exhibit power gain at appropriate voltages. In this work, we will explain a plausible mechanism by which this device should work, and present its operating characteristics. In particular, we find that a fundamental requirement for current amplification is to have the LUMO of the central moiety more strongly coupled to a control electrode than it is to the other orbitals in the molecule, while the HOMO of this moiety should be more strongly coupled to the orbitals in the other moieties than it is to the control electrode.

Unimolecular electronic devices.

The first active electronic components used vacuum tubes with appropriately-shaped electrodes, then junctions of appropriately-doped Ge, Si, or GaAs semiconductors. Electronic components can now be made with appropriately-designed organic molecules. As the commercial drive to make ever-smaller and faster circuits approaches the 3-nm limit, these unimolecular organic devices may become more useful than doped semiconductors. Here we discuss the electrical contacts between metallic electrodes and organic molecular components, and survey representative organic wires composed of conducting groups and organic rectifiers composed of electron-donor and -acceptor groups, and the Aviram-Ratner proposal for unimolecular rectification. Molecular capacitors and amplifiers are discussed briefly. Molecular electronic devices are not only ultimately small (<3 nm in all directions) and fast, but their excited states may be able to decay by photons, avoiding the enormous heat dissipation endured by Si-based components that decay by phonons. An all-organic computer is an ultimate, but more distant, goal.

The dose from Compton backscatter screening.

Systems based on the detection of Compton backscattered X rays have been deployed for screening personnel for weapons and explosives. Similar principles are used for screening vehicles at border-crossing points. Based on well-established scattering cross sections and absorption coefficients in conjunction with reasonable estimates of the image contrast and resolution, the entrance skin dose and the dose at a depth of 1 cm can be calculated. The effective dose can be estimated using the same conversion coefficients as used to convert exposure measurements to the effective dose. It is shown that the effective dose is highly dependent on image resolution (i.e. pixel size).The effective doses for personnel screening systems are unlikely to be in compliance with the American National Standards Institute standard NS 43.17 unless the pixel sizes are >4 mm. Nevertheless, calculated effective doses are well below doses associated with health effects.

Kidney transplantation as primary therapy for end-stage renal disease: a National Kidney Foundation/Kidney Disease Outcomes Quality Initiative (NKF/KDOQITM) conference.

BACKGROUND AND OBJECTIVES: Kidney transplantation is the most desired and cost-effective modality of renal replacement therapy for patients with irreversible chronic kidney failure (end-stage renal disease, stage 5 chronic kidney disease). Despite emerging evidence that the best outcomes accrue to patients who receive a transplant early in the course of renal replacement therapy, only 2.5% of incident patients with end-stage renal disease undergo transplantation as their initial modality of treatment, a figure largely unchanged for at least a decade. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: The National Kidney Foundation convened a Kidney Disease Outcomes Quality Initiative (KDOQI) conference in Washington, DC, March 19 through 20, 2007, to examine the issue. Fifty-two participants representing transplant centers, dialysis providers, and payers were divided into three work groups to address the impact of early transplantation on the chronic kidney disease paradigm, educational needs of patients and professionals, and finances of renal replacement therapy. RESULTS: Participants explored the benefits of early transplantation on costs and outcomes, identified current barriers (at multiple levels) that impede access to early transplantation, and recommended specific interventions to overcome those barriers. CONCLUSIONS: With implementation of early education, referral to a transplant center coincident with creation of vascular access, timely transplant evaluation, and identification of potential living donors, early transplantation can be an option for substantially more patients with chronic kidney disease.

Impact of the expanded criteria donor allocation system on candidates for and recipients of expanded criteria donor kidneys.

BACKGROUND: A national policy to allocate kidneys from expanded criteria donors (ECD) took effect October 31, 2002. METHODS: To assess its impact, we analyzed data from the Scientific Registry of Transplant Recipients for ECD kidney candidates and recipients between November 1999 and October 2005. RESULTS: The likelihood of being listed for ECD transplant, of receiving any transplant, and of receiving an ECD transplant were assessed using logistic regression models. As of October 31, 2005, 42.6% of candidates were listed with an ECD designation (range by donation service area [DSA], 1.9% to 94.9%). ECD-listed candidates were likely to be older, diabetic, and sensitized. By October 31, 2005, candidates listed for ECD as of November 1, 2002 were 41% more likely to receive any kidney transplant than those not ECD-listed. Among ECD-listed recipients, 30.1% received an ECD transplant and 69.9% a non-ECD transplant. Recipients more likely to receive an ECD transplant were significantly older and in DSAs where a high percentage of ECD transplants were performed and/or a low percentage of candidates were ECD-listed. CONCLUSIONS: A large, regionally variable fraction of candidates are opting to receive ECD offers. Listing with an ECD designation increases the likelihood of transplantation in selected populations. Selective listing of ECD candidates is associated with a higher likelihood of receiving an ECD transplant.

Unimolecular rectification of monolayers of CH3C(O)S-C14H28Q(+)-3CNQ(-) and CH3C(O)S-C16H32Q(+)-3CNQ(-) organized by self-assembly, Langmuir-Blodgett, and Langmuir-Schaefer techniques.

The advantage of "self-assembly" (strong covalent binding to substrates) was combined with the advantage of Langmuir-Blodgett (LB) or Langmuir-Schaefer (LS) transfer to a solid substrate (quantitative transfer of monolayers to the substrate). The electrical rectification (asymmetric conduction) by a monolayer of thioacetylalkylquinolinium tricyanoquinodimethanide was critically compared when these molecules had been transferred, by such competing techniques, onto gold electrodes, and then covered by a "cold gold" pad electrode. Unimolecular rectification was observed in the expected directions in the LB and LS monolayers. The Self-Assembled Monolayers (SAMs) were disordered; macroscopic measurements of rectification were unsuccessful for the SAMs, but successful for the down-stroke LB and LS monolayers, whose orientation and potential bonding to the Au surface should be identical to that of an ideal SAM.