The Application of the Engineering Design Process to Curriculum Revision: A Collaborative Approach to STEM Curriculum Refinement in an Urban District

This study describes how student unit assessment data helped support ongoing curriculum revisions in the Baltimore City School District. This project is situated in the STEM Achievement in Baltimore Elementary Schools (SABES) project, which is a National Science Foundation funded multi‐year Math Science Partnership between the Johns Hopkins University and the Baltimore City School District. The project focuses on improving STEM education in grades three through five. The study modeled the process of curriculum revision after the engineering design process. One of the units developed by the partnership was analyzed using this revision process. Areas of unit revision and modification were identified utilizing the analysis of pre‐ and post‐assessment data from the implementation of the unit. Constraints represented by standards, unit objectives, and student‐reading levels further informed the revision process. The process resulted in modifications to aspects of the unit and assessment. Findings from this work will help inform collaborative curriculum initiatives between institutions of higher education public school districts.     

Raman enhancement of azobenzene monolayers on substrates prepared by Langmuir-Blodgett deposition and electron-beam lithography techniques

Nanostructured metallic platforms for Raman enhancement were fabricated using Langmuir-Blodgett and electron beam (e-beam) lithography techniques. The gold platforms were inscribed on thin glass slides with the purpose of using them in a transmission geometry experimental setup under a confocal microscope. The plasmon frequency of the gold nanostructures was determined in the visible-near-infrared range for various pattern sizes prepared by Langmuir-Blodgett transfer and e-beam lithography. The surface Raman enhancement factors were determined for a monolayer of azobenzene molecules adsorbed on gold through thiol bonding and compared for both LB transfer and e-beam samples for nanostructures of comparable geometries.     

Highly active and stereoselective zirconium and hafnium alkoxide initiators for solvent-free ring-opening polymerization of rac-lactide

Under solvent-free conditions (at 130 degrees C), zirconium and hafnium amine tris(phenolate) alkoxides are extremely active, well-controlled, single-site initiators for the ring-opening polymerization of rac-lactide, yielding highly heterotactic polylactide.     

Real-time and conventional PCR detection of Liberty Link® rice varieties and transgenic soy in rice sampled in the Mexican and American retail markets

Samples of rice from Mexican and USA retail stores were analyzed for the presence of transgenic (GM) events using real-time PCR. In screening for the CaMV35S promoter sequence (35SP), positive results were found in 49 and 35% of the Mexican and American samples, respectively. In further investigations in Mexican samples, 43% were positive for P35S::bar, with two above the quantifiable limit; these were 0.07% and 0.05% GMO. Fourteen out of the sixteen positive samples were labeled as imported from the USA. In testing samples bought in American retail shops, 24% showed positive results, all below the quantifiable range. It could be deduced that P35S::bar positive samples were Liberty Link(R) (LL) rice. In distinguishing between LL601 and LL62, end-point PCR was used, corroborating the P35S::bar amplicon length difference of these events. LL62 was found in one rice sample purchased in Mexico and two in the USA samples. Its presence was verified with the 35S terminator sequence. All other LL positive samples contained LL601. None of the samples analyzed showed the presence of Bt63 rice. The LL rice varieties found have been identified as not being commercially cultivated, and so their presence requires further investigation. 35SP was also present in samples which did not have any LL rice. Maize sequences could not be detected in any of the samples; however, soybean DNA was found in Mexican and USA rice samples. The Roundup Ready(R) trait was detected in trace amounts in 16 and 6% of the rice samples bought in Mexico and the USA, respectively. Real-time PCR was shown to be the method of choice for the sensitive and rapid screening of commodities and retail samples for the detection of GM and other contamination.     

Microwave high performance liquid chromatography with UV-visible detection. Application to vitamins determination

The present work describes the first attempt to use microwave reversed phase high performance liquid chromatography (MW-HPLC) to carry out the separation of organic compounds. Biotin and riboflavin were selected for the characterization of the new separation technique. Additional vitamins (nicotinamide, pyridoxine and thiamine) were used as reference compounds. In order to perform the separation, a chromatographic column was placed inside a domestic microwave oven in a hanging position. The column particular location was an extremely critical point, since it precluded the actual power absorbed by the sample. In order to avoid magnetron damage, a heat well (i.e., water vessels) was used. Vitamins were detected using a UV-VIS detector. Results obtained showed that the application of microwave radiation, even at low power levels, gave rise to a significant modification in the characteristics of the chromatograms. It was found that retention times for biotin and riboflavin shortened as the power increased. Furthermore, the peak shape also changed, with the modification being more significant for the former vitamin than for the latter one. Furthermore, sensitivity also increased as the column was exposed to the action of microwave. Comparatively speaking, MW-HPLC was more efficient in terms of compound separation than when performed at room temperature or thermostatted at 45 °C HPLC. This was likely due to the combined action of a moderate and quick heating of the mobile phase with an increase in the analytes diffusivity caused by the radiation.     

Dynamic mapping of CN rotation following photoexcitation of ICN-

In a spin: the dynamics of photoexcited ICN(-) (Ar)(0-5) are presented. Photodetachment produces quasi-thermal electron emission that leaves ICN with up to 2.85 eV of internal energy. Photodissociation at 2.5 eV leads to one-atom caging and highly solvated anion products. Calculations indicate efficient energy transfer into CN rotation upon excitation to the (2)Π(1/2) excited state. CN rotation is vital to explain the unique dynamics observed.     

Electroacoustic isoelectric point determinations of bauxite refinery residues: different neutralization techniques and minor mineral effects

Bauxite refinery residue (BRR) is a highly caustic, iron hydroxide-rich byproduct from alumina production. Some chemical treatments of BRR reduce soluble alkalinity and lower residue pH (to values <10) and generate a modified BRR (MBRR). MBRR has excellent acid neutralizing (ANC) and trace-metal adsorption capacities, making it particularly useful in environmental remediation. However, soluble ANC makes standard acid-base isoelectric point (IEP) determination difficult. Consequently, the IEP of a BRR and five MBRR derivatives (sulfuric acid-, carbon dioxide-, seawater-, a hybrid neutralization, i.e, partial CO(2) neutralization followed by seawater, and an activated-seawater-neutralized MBRR) were determined using electroacoustic techniques. Residues showed three significantly different groups of IEPs (p < 0.05) based around the neutralization used. Where the primary mineral assemblage is effectively unchanged, the IEPs were not significantly different from BRR (pH 6.6-6.9). However, neutralizations generating neoformational minerals (alkalinity precipitation) significantly increased the IEP to pH 8.1, whereas activation (a removal of some primary mineralogy) significantly lowered the IEP to pH 6.2. Moreover, surface charging curves show that surfaces remain in the ±30 mV surface charge instability range, which provides an explanation as to why MBRRs remove trace metals and oxyanions over a broad pH range, often simultaneously. Importantly, this work shows that minor mineral components in complex mineral systems may have a disproportionate effect on the observable bulk IEP. Furthermore, this work shows the appropriateness of electroacoustic techniques in investigating samples with significant soluble mineral components (e.g., ANC).     

Trinuclear ruthenium clusters as bivalent electrochemical probes for ligand-receptor binding interactions

Despite their popularity, electrochemical biosensors often suffer from low sensitivity. One possible approach to overcome low sensitivity in protein biosensors is to utilize multivalent ligand-receptor interactions. Controlling the spatial arrangement of ligands on surfaces is another crucial aspect of electrochemical biosensor design. We have synthesized and characterized five biotinylated trinuclear ruthenium clusters as potential new biosensor platforms: [Ru(3)O(OAc)(6)CO(4-BMP)(py)](0) (3), [Ru(3)O(OAc)(6)CO(4-BMP)(2)](0) (4), [Ru(3)O(OAc)(6)L(4-BMP)(py)](+) (8), [Ru(3)O(OAc)(6)L(4-BMP)(2)](+) (9), and [Ru(3)O(OAc)(6)L(py)(2)](+) (10) (OAc = acetate, 4-BMP = biotin aminomethylpyridine, py = pyridine, L = pyC16SH). HABA/avidin assays and isothermal titration calorimetry were used to evaluate the avidin binding properties of 3 and 4. The binding constants were found to range from (6.5-8.0) × 10(6) M(-1). Intermolecular protein binding of 4 in solution was determined by native gel electrophoresis. QM, MM, and MD calculations show the capability for the bivalent cluster, 4, to intramolecularly bind to avidin. Electrochemical measurements in solution of 3a and 4a show shifts in E(1/2) of -58 and -53 mV in the presence of avidin, respectively. Self-assembled monolayers formed with 8-10 were investigated as a model biosensor system. Diluent/cluster ratio and composition were found to have a significant effect on the ability of avidin to adequately bind to the cluster. Complexes 8 and 10 showed negligible changes in E(1/2), while complex 9 showed a shift in E(1/2) of -43 mV upon avidin addition. These results suggest that multivalent interactions can have a positive impact on the sensitivity of electrochemical protein biosensors.     

Development of a novel molecularly imprinted polymer for the retention of 4,6-dimethyldibenzothiophene

Several molecularly imprinted polymers (MIPs) for the retention of 4,6-dimethyldibenzothiophene (4,6-DMDBT) were prepared. The first was a polymer prepared non-covalently with methacrylic acid and ethylene glycol dimethacrylate polymerized in the presence of 4,6-DMDBT. After extraction of 4,6-DMDBT, the selectivity of the imprinted polymer was evaluated by HPLC and compared to a non-imprinted control polymer prepared without 4,6-DMDBT. The imprinted polymer retained 4,6-DMDBT slightly longer than the control polymer. The second polymer was prepared using nickel (II)-methacryloylhistidinedihydrate monomer which was combined with 4,6-DMDBT, and polymerized with ethylene glycol dimethacrylate. This is a novel use of this monomer for retention of sulfur-containing organic compounds. Selectivity for 4,6-DMDBT was much greater in this polymer compared to the first, and retention in acetonitrile was more than three times greater on the imprinted polymer compared to a control polymer. Results indicate the potential use of this novel MIP for the removal of organosulfur compounds from fuel.