Tomographic Analysis of the Anatomical Parameters for the Insertion of Cortical Bone Screws.

Objective To study the parameters related to the insertion path of cortical screws and to describe this technique. Methods Computed tomography (CT) scans of 30 patients, as well as the measurements from the L1 to the L5 vertebrae, were studied. A second observer evaluated ten randomly-selected exams. The parameters studied included the lateral angle (LA) and the screw diameter (SD) as axial variables, and the cranial angle (CA) and screw length (SL) as sagittal variables. Results We studied 15 male patients (mean age: 31.33 years) and 15 female patients (mean age: 32.01 years). The LA varied between 13.8° and 20.89°, with a tendency to increase in the proximal to distal direction. The CA varied from 17.5° to 24.9°, with a tendency to decrease in the caudal direction. The SD ranged from 2.3 mm to 7.2 mm, with a tendency to increase as we progressed from proximal to distal. The SL varied from 19 mm to 45 mm, with a tendency to decrease as we proceeded from proximal (L1) to distal (L5). No statistical difference was observed between the genders or in the interobserver agreement regarding the values studied when comparing the sides. Conclusion The path of insertion of the cortical screw shows a variation in different populations. Therefore, we recommend a preoperative imaging study to reduce the surgical risks related to the technique.

Tomographic Analysis of the Anatomical Parameters for the Insertion of Cortical Bone Screws / Análise tomográfica dos parâmetros anatômicos para inserção dos parafusos de trajeto cortical

Abstract Objective To study the parameters related to the insertion path of cortical screws and to describe this technique. Methods Computed tomography (CT) scans of 30 patients, as well as the measurements from the L1 to the L5 vertebrae, were studied. A second observer evaluated ten randomly-selected exams. The parameters studied included the lateral angle (LA) and the screw diameter (SD) as axial variables, and the cranial angle (CA) and screw length (SL) as sagittal variables. Results We studied 15 male patients (mean age: 31.33 years) and 15 female patients (mean age: 32.01 years). The LA varied between 13.8° and 20.89°, with a tendency to increase in the proximal to distal direction. The CA varied from 17.5° to 24.9°, with a tendency to decrease in the caudal direction. The SD ranged from 2.3 mm to 7.2 mm, with a tendency to increase as we progressed from proximal to distal. The SL varied from 19 mm to 45 mm, with a tendency to decrease as we proceeded from proximal (L1) to distal (L5). No statistical difference was observed between the genders or in the interobserver agreement regarding the values studied when comparing the sides. Conclusion The path of insertion of the cortical screw shows a variation in different populations. Therefore, we recommend a preoperative imaging study to reduce the surgical risks related to the technique.

Resumo Objetivo Estudar os parâmetros anatômicos do trajeto de inserção do parafuso cortical e descrever sua técnica. Métodos Analisaram-se exames de tomografia computadorizada de 30 pacientes, e as medidas nas vértebras de L1 a L5 bilateralmente. Um segundo observador avaliou dez exames aleatoriamente. Os parâmetros incluíram o ângulo lateral (AL) e o diâmetro do parafuso (DP) como variáveis axiais, e o ângulo cranial (AC) e o comprimento do parafuso (CP) como variáveis sagitais. Resultados No total, havia 15 pacientes do sexo masculino (média de idade de 31,33 anos) e 15 do sexo feminino (média de idade de 32,01 anos). O AL variou de 13,8° a 20,89°, com uma tendência de aumento no sentido de proximal a distal. O AC variou de 17,5° a 24,9°, com tendência de diminuição no sentido caudal. O DP variou de 2,3 mm a 7,2 mm, havendo uma tendência ao aumento conforme avançamos de proximal a distal. O CP variou de 19 mm a 45 mm, havendo uma tendência de diminuição conforme avançamos de proximal (L1) a distal (L5). Não houve diferença estatística entre os sexos, nem diferenças na confiabilidade interobservador, quanto aos valores estudados quando comparados os lados. Conclusão A trajetória do parafuso de trajeto cortical apresenta variações em diferentes populações. Assim, recomendamos o estudo pré-operatório de imagens para reduzir os riscos cirúrgicos relacionados à técnica.

A Vibrissa-Inspired Highly Flexible Tactile Sensor: Scanning 3D Object Surfaces Providing Tactile Images.

Just as the sense of touch complements vision in various species, several robots could benefit from advanced tactile sensors, in particular when operating under poor visibility. A prominent tactile sense organ, frequently serving as a natural paragon for developing tactile sensors, is the vibrissae of, e.g., rats. Within this study, we present a vibrissa-inspired sensor concept for 3D object scanning and reconstruction to be exemplarily used in mobile robots. The setup consists of a highly flexible rod attached to a 3D force-torque transducer (measuring device). The scanning process is realized by translationally shifting the base of the rod relative to the object. Consequently, the rod sweeps over the object's surface, undergoing large bending deflections. Then, the support reactions at the base of the rod are evaluated for contact localization. Presenting a method of theoretically generating these support reactions, we provide an important basis for future parameter studies. During scanning, lateral slip of the rod is not actively prevented, in contrast to literature. In this way, we demonstrate the suitability of the sensor for passively dragging it on a mobile robot. Experimental scanning sweeps using an artificial vibrissa (steel wire) of length 50 mm and a glass sphere as a test object with a diameter of 60 mm verify the theoretical results and serve as a proof of concept.

Resolution of the paradox of the diamagnetic effect on the Kibble coil.

Employing very simple electro-mechanical principles known from classical physics, the Kibble balance establishes a very precise and absolute link between quantum electrical standards and macroscopic mass or force measurements. The success of the Kibble balance, in both determining fundamental constants (h, [Formula: see text], e) and realizing a quasi-quantum mass in the 2019 newly revised International System of Units, relies on the perfection of Maxwell's equations and the symmetry they describe between Lorentz's force and Faraday's induction, a principle and a symmetry stunningly demonstrated in the weighing and velocity modes of Kibble balances to within [Formula: see text], with nothing but imperfect wires and magnets. However, recent advances in the understanding of the current effect in Kibble balances reveal a troubling paradox. A diamagnetic effect, a force that does not cancel between mass-on and mass-off measurement, is challenging balance maker's assumptions of symmetry at levels that are almost two orders of magnitude larger than the reported uncertainties. The diamagnetic effect, if it exists, shows up in weighing mode without a readily apparent reciprocal effect in the velocity mode, begging questions about systematic errors at the very foundation of the new measurement system. The hypothetical force is caused by the coil current changing the magnetic field, producing an unaccounted force that is systematically modulated with the weighing current. Here we show that this diamagnetic force exists, but the additional force does not change the equivalence between weighing and velocity measurements. We reveal the unexpected way that symmetry is preserved and show that for typical materials and geometries the total relative effect on the measurement is [Formula: see text].

Effect of adsorbed/intercalated anionic dyes into the mechanical properties of PVA: layered zinc hydroxide nitrate nanocomposites.

Zinc hydroxide nitrate (ZHN) was adsorbed with anions of blue dyes (Chicago sky blue, CSB; Evans blue, EB; and Niagara blue, NB) and intercalated with anions of orange dyes (Orange G, OG; Orange II, OII; methyl orange, MO). Transparent, homogeneous and colored nanocomposite films were obtained by casting after dispersing the pigments (dye-intercalated/adsorbed into LHSs) into commercial poly(vinyl alcohol) (PVA). The films were characterized by XRD, UV-Vis spectroscopy, and mechanical testing. The mechanical properties of the PVA compounded with the dye-intercalated/adsorbed ZHN were evaluated, and reasonable increases in Young's modulus and ultimate tensile strength were observed, depending on the amount and choice of layered filler. These results demonstrate the possibility of using a new class of layered hydroxide salts intercalated and adsorbed with anionic dyes to prepare multifunctional polymer nanocomposite materials.

Zn2Al layered double hydroxides intercalated and adsorbed with anionic blue dyes: a physico-chemical characterization.

Three different anionic blue organic dyes have been intercalated into the structure of Zn(2)Al layered double hydroxides, using the co-precipitation method at constant pH. Using the same synthetic procedure, Zn(2)Al-Cl has been prepared and used as an adsorptive phase to retain the blue dyes from an aqueous solution. All the organic/inorganic (O/I) hybrid LDH compounds were analyzed by X-ray powder diffraction (XRPD), thermal analysis (TG/DTA), elemental analysis, solid state (13)C nuclear magnetic resonance (CPMAS (13)C NMR), and Fourier transform infrared spectroscopy (FTIR). In the adsorption experiments, Gibbs free energy DeltaG values for the temperatures in a range between 10 and 40 degrees C were found to be negative, which indicates that the nature of adsorption is spontaneous and shows the affinity of LDH material towards the blue anionic dyes. Additionally a decrease in DeltaG values at higher temperature further indicates that this process is even more favorable at these conditions. The enthalpy DeltaH values were between physisorption and chemisorption, and it may be concluded that the process was a physical adsorption enhanced by a chemical effect, characterized by a combined adsorption/intercalation reaction, making these O/I assemblies reminiscent of the Maya blue.

New multifunctional materials obtained by the intercalation of anionic dyes into layered zinc hydroxide nitrate followed by dispersion into poly(vinyl alcohol) (PVA).

Different anionic blue and orange dyes have been immobilized on a zinc hydroxide nitrate (Zn(5)(OH)(8)(NO(3))(2)nH(2)O--Zn-OH-NO(3)) by anion exchange with interlayer and/or outer surface nitrate ions of the layered matrix. Orange G (OG) was totally intercalated, orange II (OII) was partially intercalated, while Niagara blue 3B (NB) and Evans blue (EV) were only adsorbed at the outer surface. Several composite films of poly(vinyl alcohol)--PVA were prepared by casting through the dispersion of the hybrid material (Zn-OH-OG) into a PVA aqueous solution and evaporation of water in a vacuum oven. The obtained composite films were transparent, colored, and capable of absorbing UV radiation. Improved mechanical properties were also obtained in relation to the nonfilled PVA films. These results demonstrate the onset of a new range of potential applications for layered hydroxide salts in the preparation of polymer composite multifunctional materials.

Organic inorganic dye filler for polymer: blue-coloured layered double hydroxides into polystyrene.

A series of blue dye molecules, Evans blue (EB), Chicago sky blue (CB), Niagara blue (NB) were incorporated by direct co-precipitation within the galleries of negatively charge layered double hydroxide (LDH). The materials of cation composition Zn/Al = 2 lead to well-defined organic inorganic assemblies. The molecular arrangement of the interleaved dye molecule is proposed by 1D electronic density projection along the stacking direction for the hydrothermally treated samples with alternatively a highly inclined orientation of EB and CB and a parallel-bilayer arrangement for NB. Blue coloured LDH assemblies were subsequently dispersed into polystyrene (PS). It was found that the hybrid fillers do not interfere in the radical polymerization of styrene, giving rise to similar molecular weight and polydispersity than filler free PS, while higher glass transition temperatures were obtained for the nanocomposites. This was consistent with the rheological behaviour with the observation for LDH/NB filler based nanocomposite of shear thinning exponent different from zero, underlining frictional interaction between filler and PS chain. The absorption maximum slightly blue-shifted for the hybrid filler in comparison to the corresponding organic dye was found unmodified for the PS nanocomposite, thus giving rise to blue coloured plastic films, reminiscent somehow of the blue Maya effect.

Structural and magnetic properties of Fe and Co nanoparticles embedded in powdered Al2O3.

The structural and magnetic properties of powdered composites consisting of nanosized Fe and Co particles embedded in alumina grains have been investigated. The composites were synthesized by a novel and simple method using co-precipitation from a hybrid gel solution containing layered double hydroxide and aluminium hydroxide. After a vacuum annealing procedure, the Fe composites have a negligible number of Fe(+3) ions and a high concentration of crystalline alpha-Fe nanoparticles having truncated polyhedron shapes with an average diameter of 20 nm that are physically well separated from each other. Magnetization measurements as a function of temperature revealed a superparamagnetic-like behavior characteristic of an assembly of fine particles. A spurious ferromagnetism related to surface interaction between magnetic particles from different powder grains and the formation mechanism of the composites are also discussed.

Covalent grafting of ethylene glycol and glycerol into brucite.

Layered brucite was synthesized at room temperature and, after characterization, was reacted in a closed flask with either ethylene glycol or glycerol. Powder X-ray diffraction patterns have shown that new compounds with interlayer expansions were obtained. New bands attributed to grafting of ethylene glycol and glycerol into the interlayer surface of brucite were detected by FTIR. XPS spectroscopy and thermal analyses (TG/DSC) have shown that nearly all of the hydroxide groups of the layers were replaced by either ethylene glycol or glycerol through Mg-O-C bonds.