The influence of isosorbide on thermal properties of poly(L‐lactide) synthesized by different methods

In this article, we analyzed the influence of isosorbide content on glass transition temperature and crystallinity of poly(L ‐lactide). Different synthesis methods were applied to determine optimal procedure for polymerization of L ‐lactide in the presence of isosorbide. Two procedures were performed with tin(II) 2‐ethylhexanoate as the catalyst: first, using the vacuum sealed vessel, and second, using microwave reactor bulk polymerizations. The solution polymerization (with trifluoromethanesulfonic acid as catalyst) was possible at the temperature of 40°C. Obtained polyesters had number average molecular weights ranging from 20,000 to 65,000 g mol^–1, according to the gel permeation chromatography measurements. The polymer structure was characterized by Fourier transform infrared spectroscopy and proton nuclear magnetic resonance spectroscopy. Thermal properties of the obtained polymers were analyzed using thermogravimetry (TG) and differential scanning calorimetry (DSC). According to DSC measurements, the addition of isosorbide in the polyesters influenced the increase in both glass transition temperature and degree of crystallization for all samples. The results obtained by thermogravimetric analysis confirmed the strong influence of polymerization mechanism on synthesized poly(L ‐lactides) thermal properties. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Morphogenesis and developmental ultrastructure of Nicotiana tabacum short glandular trichomes

The anatomy and ultrastructure of the short glandular trichomes occurring on young expanding leaves of Nicotiana tabacum were investigated using light and transmission electron microscopy. The objective of the present research was to characterize the cellular changes that occur during morphogenesis of short glandular trichomes, from initiation to senescence. Ultrastructural analysis of their secretory cells revealed characteristics common to gland cells: numerous mitochondria in highly organized cytoplasm, large nuclei, and an elaborate network of endoplasmic reticulum. Initial changes in nuclear and plastidial organization were observed at a more advanced secretory stage, marking the onset of senescence. During trichome senescence, gradual reduction of the cytoplasm density occurred along with structural changes of the plastids and the tonoplast. As a result of inward blebbing of the cytoplasm into the vacuole, membrane bound vesicular structures appeared in the vacuolar space. At the late secretory stage, marked by an increase in vacuolation and extraplasmic space, degenerative changes included further fragmentation of the cytoplasm and deterioration of the tonoplast. Multimembrane myelin bodies observed in the vacuolar space were indicative of membrane digestion although plasma membrane did not appear massively degraded.     

Latent overlapped fingerprint separation: a review

Fingerprint matching is a widely used process to aid in crime scene investigation, where fingerprint fragments are often found on objects and surfaces. In such cases, the lifted fingerprints (called latents) are usually of poor quality and often appear overlapped and against a noisy background. These aspects make latent fingerprint – especially overlapped latent fingerprints – segmentation and enhancement (for subsequent matching) a difficult problem, for which several solutions have been proposed during the past few years. This paper presents an overview of contemporary techniques for overlapped fingerprint separation in the context of latent overlapped fingerprint matching. In addition to explaining the main concepts and surveying the literature in the field, it highlights the importance of the overlapped fingerprint segmentation (ROI extraction) process, a step for which there are no automatic techniques yet.     

Effect of estradiol and progesterone on thyroid gland in pigs: a histochemical, stereological, and ultrastructural study

The cellular and subcellular organization of thyroid follicular cells in peripubertal (6-month-old) male pigs treated with estradiol-dipropionate (Oe) plus progesterone (Pr) in combination on the first postnatal day was studied. A stereological method was used for morphometric determinations of the relative volume densities of the follicular epithelium, colloid and interstitium, and for establishing the epithelial height and index of activation rate. Statistically significant differences of the examined parameters between the control and Oe+Pr -treated groups were determined by Student's t-test. The subcellular organization of thyroid follicular cells was studied using transmission electron microscopy (TEM). When compared with the control group, in the Oe+Pr -treated pigs, thyroid follicles possessed a noticeably higher follicular epithelium when compared with the control animals. The observed changes were quantified and comparison between the experimental groups showed that the height, volume density of follicular epithelium, and index of activation rate were significantly (P < 0.05) increased, whereas the relative volume density of the colloid was significantly (P < 0.05) decreased. At the subcellular level the thyroid follicular cells of Oe+Pr -treated pigs were characterized by increased number of polysomes and dense bodies and extensive endoplasmatic reticulum. It was concluded that a single neonatal treatment with female gonadal steroids exerted a prolonged effect on the pig's thyroid, characterized by increased biosynthesis and reabsorption of the colloid by the follicular cells.     

Lightpath routing and spectrum allocation over elastic optical networks in content provisioning with cloud migration

In this paper, an improved receiver based on diversity combining is proposed to improve the bit error rate (BER) performance of layered asymmetrically clipped optical fast orthogonal frequency division multiplexing (ACO-FOFDM) for intensity-modulated and direct-detected (IM/DD) optical transmission systems. Layered ACO-FOFDM can compensate the weakness of traditional ACO-FOFDM in low spectral efficiency, the utilization of discrete cosine transform in FOFDM system instead of fast Fourier transform in OFDM system can reduce the computational complexity without any influence on BER performance. The BER performances of layered ACO-FOFDM system with improved receiver based on diversity combining and DC-offset FOFDM (DCO-FOFDM) system with optimal DC-bias are compared at the same spectral efficiency. Simulation results show that under different optical bit energy to noise power ratios, layered ACO-FOFDM system with improved receiver has 2.86, 5.26 and 5.72 dB BER performance advantages at forward error correction limit over DCO-FOFDM system when the spectral efficiencies are 1, 2 and 3 bits/s/Hz, respectively. Layered ACO-FOFDM system with improved receiver based on diversity combining is suitable for application in the adaptive IM/DD systems with zero DC-bias.     

Combustion characteristics of wheat straw in a fixed bed

Combustion of wheat straw was investigated in a fixed-bed reactor for two air flow rates, 1,151 and 2,125 kg/m²h. Measured temperatures, mass loss, and gas composition were used to evaluate the combustion characteristics in terms of ignition front speed, burning rate, and quality of combustion in general. At lower value of air flow rate difference between the ignition rate and burning rate was significant, which can be easily noticed by the measurement results. At higher value of air flow rate, there was still a small difference between the ignition and burning rate, while the content of oxygen in the flue gas was 10%, which leads to the conclusion that a change in the method of delivering the combustion air is necessary.     

The design and evaluation of the Simple Self-Similar Sequences Generator

This paper describes a new algorithm for the generation of pseudo random numbers with approximate self-similar structure. The Simple Self-Similar Sequences Generator (4SG) elaborates on an intuitive approach to obtain a fast and accurate procedure, capable of reproducing series of points exhibiting the property of persistence and anti-persistence. 4SG has a computational complexity of O(n) and memory requirements of the order of log₂(N), where N is the number of points to be generated. The accuracy of the algorithm is evaluated by means of computer-based simulations, recurring to several Hurst parameter estimators, namely Variance Time (VT) and the Wavelets-based estimator. The Hosking and the Wavelets-based methods for the generation of self-similar series were submitted to the same tests the 4SG was analysed with, providing for a basis for comparison of several performance aspects of the algorithm. Results show that the proposal embodies a good candidate not only for on-demand emulation of arbitrarily long self-similar sequences, but also for fast and efficient online simulations.