Modification of an Implant Material

Titanium metal is a commonly used implant material which can be colonized by bacteria. Biofilms are formed when bacteria colonizes, attaches to a surface, and immobilizes. Bacterial infections or biofilms are hard to treat once formed on the surface of a metal implant. Coating the material may minimize bacteria attachment. Self-assembled monolayers are comprised of molecules that contain both a head and tail group, and can be used to coat metal to prevent biofilm formation and bacteria growth. 12-mercaptododecylphosphonic acid self-assembled monolayers have a phosphonic acid head group and a thiol tail group. A solution of 12-mercaptododecylphosphonic acid in tetrahydrofuran was used to form self-assembled monolayers on the surface of titanium. Diffuse reflectance infrared Fourier transform spectroscopy was used to evaluate the attachment of the self-assembled monolayers. Alkyl-chain ordered self-assembled monolayers formed on the titanium surface, with the thiol tail group free at the interface for additional reactions. The monolayer attachment strength was further tested through acid, base, and tape tests

Concise comparative summaries (CCS) of large text corpora with a human experiment

In this paper we propose a general framework for topic-specific summarization of large text corpora and illustrate how it can be used for the analysis of news databases. Our framework, concise comparative summarization (CCS), is built on sparse classification methods. CCS is a lightweight and flexible tool that offers a compromise between simple word frequency based methods currently in wide use and more heavyweight, model-intensive methods such as latent Dirichlet allocation (LDA). We argue that sparse methods have much to offer for text analysis and hope CCS opens the door for a new branch of research in this important field. For a particular topic of interest (e.g., China or energy), CSS automatically labels documents as being either on- or off-topic (usually via keyword search), and then uses sparse classification methods to predict these labels with the high-dimensional counts of all the other words and phrases in the documents. The resulting small set of phrases found as predictive are then harvested as the summary. To validate our tool, we, using news articles from the New York Times international section, designed and conducted a human survey to compare the different summarizers with human understanding. We demonstrate our approach with two case studies, a media analysis of the framing of “Egypt” in the New York Times throughout the Arab Spring and an informal comparison of the New York Times’ and Wall Street Journal’s coverage of “energy.” Overall, we find that the Lasso with L2 normalization can be effectively and usefully used to summarize large corpora, regardless of document size.Statistic

In vitro kinetic study of growth and mineralization of osteoblast-like cells (Saos-2) on titanium surface coated with a RGD functionalized bisphosphonate

Osteoconduction and osseointegration are the critical stages for implantation success. Peptides containing RGD (Arg-Gly-Asp) adhesive sequence are known to promote cell adhesion and consequently to favor osseointegration of medical devices. In this study, RGD peptides were coupled to a bisphosphonate used as an anchor system and chemically adsorbed on polished titanium discs. Two different concentrations, 10−10 mol/L (RGD 10−10) and 10−4 mol/L (RGD 10−4) were compared to non coated discs (RGD 0). Adhesion, spreading, and mineralization of osteoblast-like cells (Saos-2) were assessed. Mineralization kinetic was done at 3, 6, 10, 14, and 18 days of culture; the extent of mineral deposits was quantified by image analysis. Histogram repartitions of nuclear area, characterizing cell spreading, showed a shift to higher values in cells cultured on RGD coated titanium disks. Mineralization started at day 3 in the three groups, but had a faster development in the RGD 10−10 group from day 6 to day 18 compared to RGD 0 and RGD 10−4. At day 18, the percentage of mineralized area was significantly higher for RGD 10−10 compared to RGD 0 (p < 0.05). In the present study, this new method was found suitable to anchor RGD containing species on titanium: this favored adhesion and spreading of osteoblast-like cells and mineralization compared to noncoated titanium

The Scientific Method as a Scaffold to Enhance Communication Skills in Chemistry

Scientific success in the field of chemistry depends upon the mastery of a wide range of soft skills, most notably scientific writing and speaking. However, training for scientific communication is typically limited at the undergraduate level, where students struggle to express themselves in a clear and logical manner. The underlying issue is deeper than basic technical skills; rather, it is a problem of students’ unawareness of a fundamental and strategic framework for writing and speaking with a purpose. The methodology has been implemented for individual mentorship and in our regional summer research program to deliver a blueprint of thought and reasoning that endows students with the confidence and skills to become more effective communicators. Our didactic process intertwines undergraduate research with the scientific method and is partitioned into six steps, referred to as “phases”, to allow for focused and deep thinking on the essential components of the scientific method. The phases are designed to challenge the student in their zone of proximal development so they learn to extract and ultimately comprehend the elements of the scientific method through focused written and oral assignments. Students then compile their newly acquired knowledge to create a compelling and logical story, using their persuasive written and oral presentations to complete a research proposal, final report, and formal 20 min presentation. We find that such an approach delivers the necessary guidance to promote the logical framework that improves writing and speaking skills. Over the past decade, we have witnessed both qualitative and quantitative gains in the students’ confidence in their abilities and skills (developed by this process), preparing them for future careers as young scientists

Monolayer-directed Assembly and Magnetic Properties of FePt Nanoparticles on Patterned Aluminum Oxide

FePt nanoparticles (NPs) were assembled on aluminum oxide substrates, and their ferromagnetic properties were studied before and after thermal annealing. For the first time, phosph(on)ates were used as an adsorbate to form self-assembled monolayers (SAMs) on alumina to direct the assembly of NPs onto the surface. The Al2O3 substrates were functionalized with aminobutylphosphonic acid (ABP) or phosphonoundecanoic acid (PNDA) SAMs or with poly(ethyleneimine) (PEI) as a reference. FePt NPs assembled on all of these monolayers, but much less on unmodified Al2O3, which shows that ligand exchange at the NPs is the most likely mechanism of attachment. Proper modification of the Al2O3 surface and controlling the immersion time of the modified Al2O3 substrates into the FePt NP solution resulted in FePt NPs assembly with controlled NP density. Alumina substrates were patterned by microcontact printing using aminobutylphosphonic acid as the ink, allowing local NP assembly. Thermal annealing under reducing conditions (96%N2/4%H2) led to a phase change of the FePt NPs from the disordered FCC phase to the ordered FCT phase. This resulted in ferromagnetic behavior at room temperature. Such a process can potentially be applied in the fabrication of spintronic devices

A comprehensive review of techniques for biofunctionalization of titanium

A number of surface modification techniques using immobilization of biofunctional molecules of Titanium (Ti) for dental implants as well as surface properties of Ti and Ti alloys have been developed. The method using passive surface oxide film on titanium takes advantage of the fact that the surface film on Ti consists mainly of amorphous or low-crystalline and non-stoichiometric TiO2. In another method, the reconstruction of passive films, calcium phosphate naturally forms on Ti and its alloys, which is characteristic of Ti. A third method uses the surface active hydroxyl group. The oxide surface immediately reacts with water molecules and hydroxyl groups are formed. The hydroxyl groups dissociate in aqueous solutions and show acidic and basic properties. Several additional methods are also possible, including surface modification techniques, immobilization of poly(ethylene glycol), and immobilization of biomolecules such as bone morphogenetic protein, peptide, collagen, hydrogel, and gelatin

Rapid and Complete Surface Modification with Strain‐Promoted Oxidation‐Controlled Cyclooctyne‐1,2‐Quinone Cycloaddition (SPOCQ)

Strain‐promoted oxidation‐controlled cyclooctyne‐1,2‐quinone cycloaddition (SPOCQ) between functionalized bicyclo[6.1.0]non‐4‐yne (BCN) and surface‐bound quinones revealed an unprecedented 100 % conjugation efficiency. In addition, monitoring by direct analysis in real time mass spectrometry (DART‐MS) revealed the underlying kinetics and activation parameters of this immobilization process in dependence on its microenvironment