Jonas Gruber

O papel da Radiologia em Odontologia Legal

There are various methods for the identification of human remains; most of them are based on comparisons between available ante- and post-mortem data. Although fingerprinting is the most accurate and precise method, in many cases, such as in mutilated, decomposed, burned or fragmented bodies, it cannot be used, and the dental methods become of the utmost importance, since teeth and dental restorations are very resistant to destruction by fire--they keep numerous characteristics, which are quite unique, and offer the possibility of accurate and legally acceptable identification of remains. This brief review describes the progress of forensic dentistry during the last 25 years, regarding the procedures and techniques that use ante-mortem and post-mortem radiographs. Among the discussed progresses one can point out: a specially designed self-supporting film holder that retains intra-oral films in the mouths of deceased persons whose mandibular musculature has been fixed in rigor mortis; positioning devices suitable for reproducing the geometry of ante-mortem radiographic images; methods involving digital radiographs, which can be easily stored in a central archive, retrieved and transmitted, via modem, to mass casualty sites; age estimation procedures; identification of edentulous individuals comparing radiographs of the maxilla; and studies of validation of dental radiographs taken with ante-mortem and post-mortem intervals of up to 30 years.

A novel soluble poly(fluorenylenevinylene) conjugated polymer: synthesis, characterization and application to optoelectronic devices

We report the synthesis and characterization of poly(9,9-dioctyl-1,4-fluorenylenevinylene), PDO14FV. This polymer is a novel poly(arylenevinylene) with fluorene units and long chain substituents that ensure solubility in organic solvents. PDO14FV presents green photoluminescence and yellow–green electroluminescence. The estimated ionization potential of PDO14FV is 5.3 eV and its estimated electroaffinity 2.5 eV. Organic light-emitting diodes based on PDO14FV were constructed, showing electroluminescent intensity onset at ca. 6 V.

Efficiency assessment of single unit monomer insertion reactions for monomer sequence control: kinetic simulations and experimental observations

The reaction efficiency of single unit monomer insertion (SUMI) reactions via the reversible addition fragmentation chain transfer (RAFT) method is investigated in detail by the determination of obtained product yields of optimized batch and microflow synthesis procedures in combination with kinetic simulations of the radical insertion process. A method is developed to obtain exact concentration information on different SUMI products from calibration of the corresponding electrospray ionization mass spectra that are recorded on-line during synthesis. Experimental data show that isolated yields decrease for each subsequent SUMI reaction. This effect is investigated via kinetic modelling to understand which parameters have a beneficial or negative influence on the reaction outcome. Although most reaction conditions (such as monomer concentration or radical flux) do not play a considerable role in the obtainable yield of the insertion reaction, the model clearly shows that the propagation rate coefficient must display a strong chain-length dependency in order to explain the experimental observations. When taken into account, the simulations very well fit the experimental data obtained from optimized microreactor flow synthesis and recommendations for SUMI reactions are formulated. Finally, the optimized SUMI conditions obtained from microreactor experiments and kinetic modelling insights have been applied to upscale the SUMI synthesis reactions in a mesoflow reactor. This demonstrates the simple upscalability of continuous flow reactions and opens the pathway towards future synthesis of longer sequence controlled oligomers.

A conductive polymer based electronic nose for early detection of Penicillium digitatum in post-harvest oranges.

We describe the construction of an electronic nose, comprising four chemiresistive sensors formed by the deposition of thin conductive polymer films onto interdigitated electrodes, attached to a personal computer via a data acquisition board. This e-nose was used to detect biodeterioration of oranges colonized by Penicillium digitatum. Significant responses were obtained after only 24 h of incubation i.e. at an early stage of biodeterioration, enabling remedial measures to be taken in storage facilities and efficiently distinguishing between good and poor quality fruits. The instrument has a very low analysis time of 40 s.

An electrochemical route to poly(p-phenylenevinylene) polymers (PPVs) and copolymers via cathodically generated quinodimethanes: preparative and structural aspects

An electrochemical route to poly(p-phenylenevinylenes)(PPVs) is described which involves cathodic cleavage of bis(dibromomethyl)arenes at a mercury pool cathode. Insoluble and organosoly PPVs are obtained in good yields and are characterised as regular and linear. Copolymers are obtained by co-electrolysis of different bis(dibromomethyl)arenes. The method is versatile and much functionality is tolerated. The polymers can be made conducting by doping with BF3 or SO3. The effect of substituents on conductivity correlates, roughly but significantly, with Hammett σ-values. Poly(p-phenylenevinylene), the parent PPV, forms conducting blends with poly(vinyl alcohol).

Electrochemical synthesis of poly(p-xylylenes)(PPXs) and poly(p-phenylenevinylenes)(PPVs) and the study of xylylene (quinodimethane) intermediates; an underrated approach

The electrosynthesis of poly(p-xylylenes) (PPXs) and poly(p-phenylenevinylenes) (PPVs) by the direct and mediated cathodic reduction of (halomethyl)arenes is reviewed and, where appropriate, comparisons made with more conventional chemical routes. Attention is drawn to the advantages of mild (non-thermal) conditions and to the consequent toleration of a wide range of substituents in the (halomethyl)arene precursors. Copolymers are obtained by co-electrolyses and aprotic and aqueous conditions may be used. Several polymers that are inaccessible by the Wessling and related routes may be prepared electrochemically. The properties, including lifetimes, of the key quinodimethane (xylylene) intermediates have been examined by cyclic voltammetry and the results are consistent with a radical-chain mechanism for polymerisation, initiated by electrogenerated radical-anion. The physical properties of electrochemically derived polymers are comparable re molecular weight and photoelectrical properties to those prepared chemically.

Efficient multiblock star polymer synthesis from photo-induced copper-mediated polymerization with up to 21 arms

Photo-induced copper-mediated polymerization (photoCMP) is employed for the synthesis of multiarm-multiblock star copolymers. Based on a core-first approach, star polymers with four, six and twenty-one arms have been synthesized. Due to the high efficiency of the photoCMP process with respect to the reaction rate and end group functionality, each arm could be chain extended multiple times, allowing for up to 8 sequential polymerizations on the four-arm star and up to 4 blocks on the 21-arm star. Relatively high dilutions of the reaction mixtures and premature stopping of the polymerizations between 50–70% monomer conversion must be maintained in order to avoid the occurrence of star–star coupling reactions. For the optimization of the reactions, microreactor polymerizations were used to achieve economic and fast screening of the reactions. Flow reactors show improved control over the polymerizations, and also are beneficial in order to handle large amounts of solvents, which are required to synthesize the multiblock star polymers in significant quantities. By switching between an n-alkyl acrylate and tert-butyl acrylate (that can be hydrolyzed to acrylic acid segments after polymerization) in the chain extensions, hierarchically structured star polymers are obtained in which hydrophilic and hydrophobic blocks are alternated. These materials show pH responsiveness and complex self-assembly in the aqueous phase depending on the number of arms and the length of the individual blocks.

Electrochemical route to xylylene polymers and copolymers via cathodically generated quinodimethanes: preparative and structural aspects

Electrochemical reductive elimination of bis(α-bromoalkyl)arenes gives quinodimethane intermediates that polymerize, mostly in high yield, to linear polymers of the poly(p-xylylene) type. At a stirred mercury cathode reaction proceeds to completion and the polymers precipitate. A considerable variety of structural variation in the precursors is tolerated. Co-electrolysis of different precursors gives copolymers. In some cases organo-sole fractions are formed. Key structural features of the polymers and copolymers are obtained by NMR spectroscopy [1H and 13C (solution and solid-state)] and by direct pyrolysis mass spectrometry. The high reactivity of the p-quinodimethanes is evident from the observed random polymerization and co-polymerization.

Efficient organic light-emitting diodes with fluorine-doped tin-oxide anode and electrochemically synthesized sulfonated polyaniline as hole transport layer

In this work we report efficiency measurements on light-emitting diodes with electrochemically synthesized sulfonated polyaniline as hole transport layer. The anode used in our devices is fluorine-doped tin oxide, the blocking layer is electrochemically synthesized poly(9,9-dioctyl-1,4-fluorenylenevinylene) and the electron transporting material and emitter is tris-(8-hydroxyquinoline) aluminum. Sulfonated polyaniline based devices presented efficiency of 0.79 cd/A.

Identification of Four Wood Species by an Electronic Nose and by LIBS

This paper presents two complementary methods capable of identifying four wood species (Cedrela fissilis, Ocotea porosa, Hymenolobium petraeum, and Aspidosperma subincanum) both by their volatile organic compounds and by the presence of 10 chemical elements: Al, B, Ca, Mg, Zn, Cu, Mn, Fe, Na, and Si. The volatile compounds were detected by an electronic nose formed by an array of three different conductive polymer gas sensors. The elemental determination was made by laser-induced breakdown spectrometry (LIBS). The emissions measured were treated by principal component analysis (PCA). Leave-one-out analysis showed a rate of hits of 100%.