Behavior of Electrodeposited Cd and Pb Schottky Junctions on CH3-Terminated n-Si(111) Surfaces

n-Si/Cd and n-Si/Pb Schottky junctions have been prepared by electrodeposition of Cd or Pb from acidic aqueous solutions onto H-terminated and CH3-terminated n-type Si(111) surfaces. For both nondegenerately (n-) and degenerately (n+-) doped H–Si(111) electrodes, Cd and Pb were readily electroplated and oxidatively stripped, consistent with a small barrier height (Phib) at the Si/solution and the Si/metal junctions. Electrodeposition of Cd or Pb onto degenerately doped CH3-terminated n+-Si(111) electrodes occurred at the same potentials as Cd or Pd electrodeposition onto H-terminated n+-Si(111). However, electrodeposition on nondegenerately doped CH3-terminated n-Si(111) surfaces was significantly shifted to more negative applied potentials (by −130 and −347 mV, respectively), and the anodic stripping of the electrodeposited metals was severely attenuated, indicating large values of Phib for contacts on nondegenerately doped n-type CH3–Si(111) surfaces. With either Cd or Pb, current–voltage measurements on the dry, electrodeposited Schottky junctions indicated that much larger values of Phib were obtained on CH3-terminated n-Si(111) surfaces than on H-terminated n-Si(111) surfaces. Chronoamperometric data indicated that CH3–Si(111) surfaces possessed an order-of-magnitude lower density of nucleation sites for metal electrodeposition than did H–Si(111) surfaces, attesting to the high degree of structural passivation afforded by the CH3–Si surface modification

Near-Ideal Photodiodes from Sintered Gold Nanoparticle Films on Methyl-Terminated Si(111) Surfaces

We report photocurrent-voltage data for improved n-Si/metal devices using CH_3-terminated n-Si(111) and Au nanoparticles (NPs). CH_3-terminated Si(111) surfaces maintain good electronic properties throughout device assembly, while the use of Au NPs as precursors to metal films circumvents the standard issues associated with interfacial reactivity of metals in Schottky barrier formation. Such devices demonstrate excellent photovoltaic properties, with photovoltages that approach the maximum values predicted for photodiodes that are limited by Si bulk diffusion/recombination processes rather than interfacial processes. These devices are compared to standard n-Si/Au devices made via thermally evaporated Au films which are well-known to be limited by junction-based recombination

Response versus Chain Length of Alkanethiol-Capped Au Nanoparticle Chemiresistive Chemical Vapor Sensors

Au nanoparticles capped with a homologous series of straight chain alkanethiols (containing 4−11 carbons in length) have been investigated as chemiresistive organic vapor sensors. The series of alkanethiols was used to elucidate the mechanisms of vapor detection by such capped nanoparticle chemiresistive films and to highlight the molecular design principles that govern enhanced detection. The thiolated Au nanoparticle chemiresistors demonstrated rapid and reversible responses to a set of test vapors (n-hexane, n-heptane, n-octane, iso-octane, cyclohexane, toluene, ethyl acetate, methanol, ethanol, isopropanol, and 1-butanol) that possessed a variety of analyte physicochemical properties. The resistance sensitivity to nonpolar and aprotic polar vapors systematically increased as the chain length of the capping reagent increased. Decreases in the nanoparticle film resistances, which produced negative values of the differential resistance response, were observed upon exposure of the sensor films to alcohol vapors. The response signals became more negative with higher alcohol vapor concentrations, producing negative values of the sensor sensitivity. Sorption data measured on Au nanoparticle chemiresistor films using a quartz crystal microbalance allowed for the measurement of the partition coefficients of test vapors in the Au nanoparticle films. This measurement assumed that analyte sorption only occurred at the organic interface and not the surface of the Au core. Such an assumption produced partition coefficient values that were independent of the length of the ligand. Furthermore, the value of the partition coefficient was used to obtain the particle-to-particle interfacial effective dielectric constant of films upon exposure to analyte vapors. The values of the dielectric constant upon exposure to alcohol vapors suggested that the observed resistance response changes observed were not significantly influenced by this dielectric change, but rather were primarily influenced by morphological changes and by changes in the interparticle spacing

Antibiotic Stewardship in Skin and Soft Tissue Infections

Introduction: Skin and soft tissue infections (SSTIs) are characterized by microbial invasion of the skin layers and are common in various healthcare settings. A study conducted between 2005-2010 in the United States, found a combined total of 2.3 million cases of SSTIs in ambulatory and inpatient settings. This was higher than the rates of pneumonia and urinary tract infections during the same time period. Another study found that between 2000 and 2012, there was a 40% increase (2.4 million to 3.3 million) in cases of SSTIs. Our aim is to study the primary uses of vancomycin and piperacillin/tazobactam and their average days of therapy in the treatment of SSTIs. Objective: Our aim is to study the primary uses of vancomycin and piperacillin/tazobactam and their average days of therapy in the treatment of SSTIs. Methods: Data was collected for during January of 2019 of all administrations of antimicrobial use in a local hospital, which included the emergency department, inpatient admissions, and intensive care unit. These data points were sorted by antimicrobial, dates administered, and then by their indicated use. Indicated uses were then tallied on a histogram and an average days on therapy was calculated per patient. Discussion: Our analysis illustrates that the top three indicated uses of vancomycin was other, sepsis, and SSTIs, in descending order. The average days of therapy per patient for use of vancomycin in the treatment of SSTIs was 2.97 days. Piperacillin/tazobactam similarly was used primarily for sepsis, gastrointestinal/intra-abdominal infections, and SSTIs, in descending order. Conclusion: Our analysis shows that the average days of therapy for use of vancomycin in the treatment of SSTIs was 2.97. Study limitations include the limited, one-month duration of the data set. Our plan is to expand this work using data from a 12-month period on use of antimicrobials in the same hospital. We intend to compare the average days of therapy for different indications (i.e sepsis) and compare to national averages. We hope to interpret these data in the context of guideline recommendations on duration of intravenous therapy for SSTIs, so as to surmise what differences may exist between guidelines and clinical practice

Genetic Algorighm Representation Selection Impact on Binary Classification Problems

In this thesis, we explore the impact of problem representation on the ability for the genetic algorithms (GA) to evolve a binary prediction model to predict whether a physical therapist is paid above or below the median amount from Medicare. We explore three different problem representations, the vector GA (VGA), the binary GA (BGA), and the proportional GA (PGA). We find that all three representations can produce models with high accuracy and low loss that are better than Scikit-Learn’s logistic regression model and that all three representations select the same features; however, the PGA representation tends to create lower weights than the VGA and BGA. We also find that mutation rate creates more of a difference in accuracy when comparing the individual with the best fitness (lowest binary cross entropy loss) and the most accurate solution when the mutation rate is higher. We then explore potential of biases in the PGA mapping functions that may encourage the lower values. We find that the PGA has biases on the values they can encode depending on the mapping function; however, since we do not find a bias towards lower values for all tested mapping functions, it is more likely that it is more difficult for the PGA to encode more extreme values given crossover tends to have an averaging effect on the PGA chromosome