A novel method for producing a glulam from the wood of peeler cores

This study presents an opportunity for rational utilization of poplar wood peeler cores in the production of glued laminated timber (glulam) beams. An approach for optimal use of small-diameter raw material with a circular cross-section is also proposed in order to obtain a final product in a significantly high quantitative yield. The applied novel method of sawing the peeler cores and subsequent combination of gluing the obtained lamellas allows to achieve: reduction of labor and energy consumption in the processing; rational utilization of this waste raw material; obtaining a product sought by consumers; opportunity to implement technology for the production of glulam from peeler cores. The results showed that sawing the peeler cores and obtaining lamellas with a trapezoidal cross-section leads to a high quantitative yield of 76,3 %. The final quantitative yield in subsequent technological operations in the manufacturing of engineered wood of glulam type reaches 48,8 % of the volume of  raw material. In addition, equations have been working are used for the determination of the most suitable sizes of the lamellas, depending on the diameter and the kerf width

Iskorištavanje borovine (Pinus sylvestris L.) s greškama za proizvodnju kompozitnog drva

This study presents opportunities for the utilization of timber by-products with defects for manufacturing engineered wood panels. Three gluing methods were proposed for this waste raw material derived from Scots pine (Pinus sylvestris L.) wood. The methods used for combining and gluing enabled a more complete and complex utilization of wood with defects. The physical properties (density and moisture content) and mechanical properties (bending strength and modulus of elasticity) of the laboratory-fabricated engineered wood panels were evaluated in accordance with the European standards. The highest density of 643 kg/m3 and bending strength values (28.6 N/mm2) were obtained from the panels manufactured using method 3 and veneered with beech veneer sheets. The modulus of elasticity of the laboratory-made engineered wood panels reached values of up to 5580 N/mm2. This study demonstrated the feasibility of the utilization of defective wood pieces in the manufacturing of engineered wood panels.U radu je predstavljena mogućnost iskorištavanja otpadnog drva s greškama za proizvodnju kompozitnog drva u graditeljstvu. Predložene su tri metode lijepljenja otpadnog drva borovine (Pinus sylvestris L.). Metode kombiniranja i lijepljenja omogućile su potpunije iskorištavanje drva s greškama. Fizička svojstva (gustoća i sadržaj vode) i mehanička svojstva (čvrstoća na savijanje i modul elastičnosti) laboratorijski proizvedenih kompozitnih drvnih ploča za graditeljstvo ocijenjena su prema europskim standardima. Najveću gustoću (643 kg/m3) i čvrstoću na savijanje (28,6 N/mm2) imale su ploče proizvedene metodom 3 i furnirane bukovim furnirom. Modul elastičnosti laboratorijski proizvedenih kompozitnih drvnih ploča za graditeljstvo dosegnuo je vrijednost od 5580 N/mm2. Ovo je istraživanje uputilo na mogućnost iskorištavanja drva s greškama za proizvodnju kompozitnih drvnih ploča namijenjenih graditeljstvu

Utilization of peeler cores for producing beams with hollow cross-section

This study presents an opportunity to utilize peeler cores derived from poplar wood for the production of hollow beams. In this way, final products to meet the needs of consumers can be obtained. The proposed novel methods for sawing and gluing the produced materials allow rational application of the waste raw material in the plywood manufacturing. Another advantage in this case is that products with a square cross-section with dimensions close to or corresponding to the standard ones are obtained from small-diameter round wood. The raw material used to receive the proposed hollow beams is up to 33% less than a conventional beam with the same dimensions. The manufactured products are lighter and with a significantly stable cross-sectional shape, compared to natural wood beams with the same dimensions. Sawing the peeler cores and obtaining materials with a triangular and trapezoidal cross-section helps to achieve volume yields from 60.6% to 71.1% of the raw material initial volume

Fluorescence Correlation Spectroscopy in Dilute Polymer Solutions: Effects of Molar Mass Dispersity and the type of fluorescent Labeling

© 2015 American Chemical Society. Fluorescence correlation spectroscopy (FCS) has become an important tool in polymer science. Among various other applications the method is often applied to measure the hydrodynamic radius and the degree of fluorescent labeling of polymers in dilute solutions. Here we show that such measurements can be strongly affected by the molar mass dispersity of the studied polymers and the way of labeling. As model systems we used polystyrene and poly(methyl methacrylate) synthesized by atom transfer radical polymerization or free-radical polymerization. Thus, the polymers were either end-labeled bearing one fluorophore per chain or side-labeled with a number of fluorophores per chain proportional to the degree of polymerization.The experimentally measured autocorrelation curves were fitted with a newly derived theoretical model that uses the Schulz-Zimm distribution function to describe the dispersity in the degree of polymerization. For end-labeled polymers having a molecular weight distribution close to Schulz-Zimm, the fits yield values of the number-average degree of polymerization and the polydispersity index similar to those obtained by reference gel permeation chromatography. However, for the side-labeled polymers such fitting becomes unstable, especially for highly polydisperse systems. Brownian dynamic simulations showed that the effect is due to a mutual dependence between the fit parameters, namely, the polydispersity index and the number-average molecular weight. As a consequence, an increase of the polydispersity index can be easily misinterpreted as an increase of the molecular weight when the FCS autocorrelation curves are fitted with a standard single component model, as commonly done in the community.status: publishe

Molecular Exchange Kinetics of Diblock Copolymer Micelles Monitored by Fluorescence Correlation Spectroscopy

We investigated the equilibrium chain-exchange kinetics of amphiphilic diblock copolymer micelles, using a new method based on fluorescence correlation spectroscopy. The micelles were formed from polystyrene-<i>block</i>-poly­[oligo­(ethylene glycol) methyl ether methacrylate] (PS–POEGMA) in different solvents and studied at various temperatures. This linear-brush copolymer was chosen as a model system, forming micelles with short and bulky corona. Depending on the applied solvent, fast exchange could be observed even at temperatures well below the nominal glass transition of the core-forming PS block. The effect is caused by swelling of the core and allows extensive tuning of the chain-exchange rate by adding to the system minor amounts of good or bad solvent for the core block

James Cook viaje al Polo Sur y alrededor del mundo (fragmento)

A new generation of nanosensors based on mesoporous silica nanocapsules with the ability to monitor the onset of metallic corrosion is successfully developed and tested on 304 stainless steel. The core of the nanocapsules contains water insoluble organic molecules that fluoresce during the anodic dissolution of metallic substrates in the corrosion process. The dispersion of the nanosensors in organic coatings applied on metal substrate allows a very sensitive fluorescent detection of the initiation of metal dissolution, close to defects in the substrate. This promising concept offers therefore new perspectives for the development of smart coatings for corrosion sensing

HPMA-LMA Copolymer Drug Carriers in Oncology: An in Vivo PET Study to Assess the Tumor Line-Specific Polymer Uptake and Body Distribution

Polymeric drug carriers aim to selectively target tumors in combination with protecting normal tissue. In this regard polymer structure and molecular weight are key factors considering organ distribution and tumor accumulation of the polymeric drug delivery system. Four different HPMA based copolymer structures (random as well as block copolymers with lauryl methacrylate as hydrophobic block) varying in molecular weight, size and resulting architecture were analyzed in two different tumor models (AT1 prostate carcinoma and Walker-256 mammary carcinoma) in vivo. Polymers were labeled with ¹⁸F and organ/tumor uptake was followed by μPET imaging and <i>ex vivo</i> biodistribution. Vascular permeability was measured by dextran extravasation and vascular density by immunohistochemistry. Cellular polymer uptake was determined in vitro using fluorescence-labeled polymers. Most strikingly, the high molecular weight HPMA-LMA random copolymer demonstrated highest tumor uptake and blood pool concentration. The molecular structure (e.g., amphiphilicity) is holding a higher impact on desired in vivo properties than polymer size. The results also revealed pronounced differences between the tumor models although vascular permeability was almost comparable. Accumulation in Walker-256 carcinomas was much higher, presumably due to a better cellular uptake in this cell line and a denser vascular network in the tumors. These investigations clearly indicate that the properties of the individual tumor determine the suitability of polymeric drug carriers. The findings also illustrate the general necessity of a preclinical screening to analyze polymer uptake for each individual patient (e.g., by noninvasive PET imaging) in order to individualize polymer-based chemotherapy

HPMA-LMA Copolymer Drug Carriers in Oncology: An in Vivo PET Study to Assess the Tumor Line-Specific Polymer Uptake and Body Distribution

Polymeric drug carriers aim to selectively target tumors in combination with protecting normal tissue. In this regard polymer structure and molecular weight are key factors considering organ distribution and tumor accumulation of the polymeric drug delivery system. Four different HPMA based copolymer structures (random as well as block copolymers with lauryl methacrylate as hydrophobic block) varying in molecular weight, size and resulting architecture were analyzed in two different tumor models (AT1 prostate carcinoma and Walker-256 mammary carcinoma) in vivo. Polymers were labeled with ¹⁸F and organ/tumor uptake was followed by μPET imaging and <i>ex vivo</i> biodistribution. Vascular permeability was measured by dextran extravasation and vascular density by immunohistochemistry. Cellular polymer uptake was determined in vitro using fluorescence-labeled polymers. Most strikingly, the high molecular weight HPMA-LMA random copolymer demonstrated highest tumor uptake and blood pool concentration. The molecular structure (e.g., amphiphilicity) is holding a higher impact on desired in vivo properties than polymer size. The results also revealed pronounced differences between the tumor models although vascular permeability was almost comparable. Accumulation in Walker-256 carcinomas was much higher, presumably due to a better cellular uptake in this cell line and a denser vascular network in the tumors. These investigations clearly indicate that the properties of the individual tumor determine the suitability of polymeric drug carriers. The findings also illustrate the general necessity of a preclinical screening to analyze polymer uptake for each individual patient (e.g., by noninvasive PET imaging) in order to individualize polymer-based chemotherapy

Nanocarrier for Oral Peptide Delivery Produced by Polyelectrolyte Complexation in Nanoconfinement

The hydrophilic peptide YY (PYY) is a promising hormone-based antiobesity drug. We present a new concept for the delivery of PYY from pH-responsive chitosan-based nanocarriers. To overcome the drawbacks while retaining the merits of the polyelectrolyte complex (PEC) method, we propose a one-pot approach for the encapsulation of a hydrophilic peptide drug in cross-linked PEC nanocarriers. First, the hydrophilic peptide is encapsulated via polyelectrolyte complexation within water-in-oil miniemulsion droplets. In a second step, the PEC surface is reinforced by controlled interfacial cross-linking. PYY is efficiently encapsulated and released upon pH change. Such nanocarriers are promising candidates for the fight against obesity and, in general, for the oral delivery of protein drugs