Spherical CaCO3: Synthesis, Characterization, Surface Modification and Efficacy as a Reinforcing Filler in Natural Rubber Composites.

Natural rubber (NR), an important natural polymer derived from the Hevea brasiliensis tree, has been widely used in the rubber industry owing to its excellent elastic properties. However, it requires reinforcing fillers to improve its mechanical properties for the manufacturing of rubber products. Generally, calcium carbonate (CaCO3) is employed as a non-reinforcing filler. This work aimed to synthesize spherical-shaped CaCO3 at a submicrometric scale without and with surface treatment and explore its utilization as a reinforcing filler in NR composites. The morphological shape and polymorphic phase of CaCO3 were investigated using SEM, TEM, XRD, ATR-FTIR and Raman techniques. The mechanical properties of various amounts (0 to 60 phr) of CaCO3-filled NR composites were explored. As a result, the NR/treated CaCO3 composites provided higher tensile strength than the NR/untreated CaCO3 composites and pure NR at all filler loadings. This may have been due to the improved interfacial interaction between NR and CaCO3 with the improved hydrophobicity of CaCO3 after treatment with olive soap. The optimal filler loading was 20 phr for the highest tensile strength of the rubber composites. In addition, the elongation at break of the NR/treated CaCO3 was slightly decreased. Evidence from SEM and FTIR revealed the vaterite polymorph and shape stability of CaCO3 particles in the NR matrix. The results demonstrate that the particle size and surface treatment of the filler have essential effects on the mechanical property enhancement of the rubber composites. Synthesized spherical CaCO3 could be a potential reinforcing filler with broader application in polymer composites.

A novel optical temperature sensor and energy transfer properties based on Tb3+/Sm3+ codoped SrY2(MoO4)4 phosphors.

A series of SrY2(MoO4)4 phosphors doped and co-doped with Tb3+/Sm3+ ions was synthesized to develop new optical temperature sensor materials. The structures, morphologies, and luminescent characteristics of these phosphors were thoroughly investigated. Luminescence spectra of mono-doped SrY2(MoO4)4 phosphors were measured under the excitation at 375 and 403 nm corresponding to direct excitation of Tb3+ and Sm3+, respectively. The characteristic luminescence bands corresponding to electronic transitions of terbium and samarium ions were detected and investigated for different dopant concentrations. The emission spectrum of the Tb3+/Sm3+ co-doped sample exhibited a total of five distinct emission peaks, indicating an energy transfer from Tb3+ to Sm3+ ions. The energy transfer efficiency from Tb3+ ions to Sm3+ ions was investigated in detail. At elevated temperatures, Tb3+ and Sm3+ exhibited distinct thermal sensitivities in their emission and excitation spectra, leading to evident thermochromic behavior. The fluorescence intensity ratio (FIR) was utilized with dual center to evaluate the temperature sensitivity of SrY2(MoO4)4:Tb3+/Sm3+ phosphors. The temperature sensing mechanism relied on the emission band intensity ratios of the 4G5/2 → 6H5/2, 4G5/2 → 6H9/2, and 4G5/2 → 6H7/2 transitions of Sm3+ in conjunction with the 5D5/2 → 7F5/2 transitions of Tb3+. This approach demonstrated high thermal sensitivity values, reaching up to 0.9% K-1. The studied nanoparticles exhibited sub-degree thermal resolution, making them suitable candidates for precise temperature-sensing applications.

Mechanical Properties' Strengthening of Photosensitive 3D Resin in Lithography Technology Using Acrylated Natural Rubber.

Acrylated natural rubber (ANR) with various acrylate contents (0.0-3.5 mol%) was prepared from natural rubber as a raw material and then incorporated with commercial 3D resin to fabricate specimens using digital light processing. As a result, the utilization of ANR with 1.5 mol% acrylate content could provide the maximum improvement in stretchability and impact strength, approximately 155% and 221%, respectively, over using pure 3D resin, without significant deterioration of tensile modulus and mechanical strength. According to evidence from a scanning electron microscope, this might be due to the partial interaction between the dispersed small rubber particles and the resin matrix. Additionally, the glass-transition temperature of the 3D-printed sample shifted to a lower temperature by introducing a higher acrylate content in the ANR. Therefore, this work might offer a practical way to effectively enhance the properties of the fundamental commercial 3D resin and broaden its applications. It also makes it possible to use natural rubber as a bio-based material in light-based 3D printing.

Hearing voices among Russian patients with schizophrenia.

There has been relatively little work which systematically examines whether the content of hallucinations in individuals diagnosed with schizophrenia varies by cultural context. The work that exists finds that it does. The present project explores the way auditory hallucinations, or "voices," manifest in a Russian cultural context. A total of 28 individuals, diagnosed with schizophrenia, who reported hearing voices at the Republican Clinical Psychiatric Hospitals in Kazan, Russia, were interviewed about their experience of auditory hallucinations. The voices reported by our Russian participants did appear to have culturally specific content. Commands tended to be non-violent and focused on chores or other activities associated with daily life (byt). Many patients also reported sensory hallucinations involving other visions, sounds, and smells which sometimes reflected Russian folklore themes. For the most part, religious themes did not appear in patients' auditory vocal hallucinations, though nearly all patients expressed adherence to a religion. These findings support research that finds that the content, and perhaps the form, of auditory hallucinations may be shaped by local culture.

Experimental and ab initio studies on the structural, magnetic, photocatalytic, and antibacterial properties of Cu-doped ZnO nanoparticles.

Copper-doped ZnO nanoparticles with a dopant concentration varying from 1-7 mol% were synthesized and their structural, magnetic, and photocatalytic properties were studied using XRD, TEM, SQUID magnetometry, EPR, UV-vis spectroscopy, and first-principles methods within the framework of density functional theory (DFT). Structural analysis indicated highly crystalline Cu-doped ZnO nanoparticles with a hexagonal wurtzite structure, irrespective of the dopant concentration. EDX and EPR studies indicated the incorporation of doped Cu2+ ions in the host ZnO lattice. The photocatalytic activities of the Cu-doped ZnO nanoparticles investigated through the degradation of methylene blue demonstrated an enhancement in photocatalytic activity as the degradation rate changed from 9.89 × 10-4 M min-1 to 4.98 × 10-2 M min-1. By the first-principles method, our results indicated that the Cu(3d) orbital was strongly hybridized with the O(2p) state below the valence band maximum (VBM) due to covalent bonding, and the ground states of the Cu-doped ZnO is favorable for the ferromagnetic state by the asymmetry of majority and minority states due to the presence of unpaired electron.

Development of Photosensitive Natural Rubber as a Mechanical Modifier for Ultraviolet-Curable Resin Applied in Digital Light Processing-Based Three-Dimensional Printing Technology.

Natural rubber (NR), a natural product from the Hevea brasiliensis tree, has been developed as a photosensitive mechanical modifier utilized in lithography-based three-dimensional (3D) printing technology. Here, we transformed NR to photosensitive NR (PNR) by incorporating acrylate groups via chemical modifications. The acrylated NR was blended with a commercial resin (CR) at various rubber contents (0 to 3 wt %) by a simple mixing approach. The blended resin was solidified to pattern the desired specimen using a digital light processing-based 3D printer. The effect of PNR contents on mechanical properties and thermal performance of the printed specimen compared to the neat CR was studied in this work. A printed sample containing 1.5 wt % PNR can increase the elongation ability and impact strength by approximately 59 and 116%, respectively, compared to the neat CR. The microstructure of the printed objects shows a heterogeneous surface consisting of dispersed rubber droplets and a continuous CR matrix. Two glass transition temperatures belonging to the rubber phase and the resin matrix can be observed. The thermal decomposition of the printed part decreased slightly with the elevation in the rubber content. Consequently, the synthesized photosensitive natural rubber could be used as a toughness modifier employed in ultraviolet-curable resin for the light-based 3D printing technology.

Current methods to monitor microalgae-nanoparticle interaction and associated effects.

Widespread use of nanoparticles for different applications has diffused their presence in the environment, particularly in water. Many studies have been conducted to evaluate their effects on aquatic organisms. Microalgae are at the base of aquatic trophic chains. These organisms which can be benthic or pelagic, meaning that they can enter into interaction with all kinds of particulate materials whatever their density, and constitute an interesting model study. The purpose of this review was to gather more than sixty studies on microalgae exposure to the different nanoparticles that may be present in the aquatic environment. After a brief description of each type of nanoparticle (metals, silica and plastic) commonly used in ecotoxicological studies, techniques to monitor their properties are presented. Then, different effects on microalgae resulting from interaction with nanoparticles are described as well as the parameters and techniques for monitoring them. The impacts described in the literature are primarily shading, ions release, oxidative stress, adsorption, absorption and disruption of microalgae barriers. Several parameters are proposed to monitor effects such as growth, photosynthesis, membrane integrity, biochemical composition variations and gene expression changes. Finally, in the literature, while different impacts of nanoparticles on microalgae have been described, there is no consensus on evidence of nanomaterial toxicity with regard to microalgae. A parallel comparison of different nanoparticle types appears essential in order to prioritize which factors exert the most influence on toxicity in microalgae cultures: size, nature, surface chemistry, concentration or interaction time.

Detection of molecular changes induced by antibiotics in Escherichia coli using vibrational spectroscopy.

This study aimed to test Raman (400-1800cm-1) and Infra-red (1900-500cm-1) spectroscopies followed by statistical analysis (principal component analysis) to detect molecular changes induced by antibiotics (ampicillin, cefotaxime - cell wall synthesis inhibitors, tetracycline - protein synthesis inhibitor, ciprofloxacin - DNA synthesis inhibitor) against Escherichia coli TOP10. In case of ampicillin and cefotaxime, a decrease in protein bands in both Raman (1240, 1660cm-1), and IR spectra (1230, 1530, 1630cm-1), and an increase in carbohydrate bands (1150, 1020cm-1) in IR spectra were observed. Tetracycline addition caused an increase in nucleic acid bands (775, 1478, 1578cm-1), a sharp decrease in phenylalanine (995cm-1) in Raman spectra and the amide I and amide II bands (1630, 1530cm-1) in IR spectra, an increase in DNA in both Raman (1083cm-1) and IR spectra (1080cm-1). Regarding ciprofloxacin, an increase in nucleic acids (775, 1478, 1578cm-1) in Raman spectra and in protein bands (1230, 1520, 1630cm-1), in DNA (1080cm-1) in IR spectra were detected. Clear discrimination of antibiotic-treated samples compared to the control was recorded, showing that Raman and IR spectroscopies, coupled to principal component analysis for data, could be used to detect molecular modifications in bacteria exposed to different classes of antibiotics. These findings contribute to the understanding of the mechanisms of action of antibiotics in bacteria.

A new way to discriminate polluted wood by vibrational spectroscopies.

In this work, two sets of samples were considered: field samples collected from local waste wood and synthetic samples made by mixing clean wood (including oak, beech, poplar) with typical organic pollutants: creosote, polychlorinated byphenils (PCBs), pentachlorophenol (PCP), cypermethrin, dodecyl dimethyl ammonium chloride (DDAC). Vibrational spectroscopy techniques were tested to detect organic pollutants in wood items. Raman and infrared spectroscopies were showed as fast, non-destructive and non-invasive fingerprint techniques for detection of organic molecules. Associated with principal component analysis, we have shown the evidence of quick detection of and discrimination of polluted wood items by kinds and versus concentration.

Microplastic interactions with freshwater microalgae: Hetero-aggregation and changes in plastic density appear strongly dependent on polymer type.

In this study, the interactions between microplastics, chosen among the most widely used in industry such as polypropylene (PP) and high-density polyethylene (HDPE), and a model freshwater microalgae, Chlamydomas reinhardtii, were investigated. It was shown that the presence of high concentrations of microplastics with size >400 µm did not directly impact the growth of microalgae in the first days of contact and that the expression of three genes involved in the stress response was not modified after 78 days. In parallel, a similar colonization was observed for the two polymers. However, after 20 days of contact, in the case of PP only, hetero-aggregates constituted of microalgae, microplastics and exopolysaccharides were formed. An estimation of the hetero-aggregates composition was approximately 50% of PP fragments and 50% of microalgae, which led to a final density close to 1.2. Such hetero-aggregates appear as an important pathway for the vertical transport of PP microplastics from the water surface to sediment. Moreover, after more than 70 days of contact with microplastics, the microalgae genes involved in the sugar biosynthesis pathways were strongly over-expressed compared to control conditions. The levels of over-expression were higher in the case of HDPE than in PP condition. This work presents the first evidence that depending on their chemical nature, microplastics will follow different fates in the environment.

Gold-Coated Iron Composite Nanospheres Targeted the Detection of Escherichia coli.

We report the preparation and characterization of spherical core-shell structured Fe3O4-Au magnetic nanoparticles, modified with two component self-assembled monolayers (SAMs) consisting of 3-mercaptophenylboronic acid (3-MBA) and 1-decanethiol (1-DT). The rapid and room temperature synthesis of magnetic nanoparticles was achieved using the hydroxylamine reduction of HAuCl4 on the surface of ethylenediaminetetraacetic acid (EDTA)-immobilized iron (magnetite Fe3O4) nanoparticles in the presence of an aqueous solution of hexadecyltrimetylammonium bromide (CTAB) as a dispersant. The reduction of gold on the surface of Fe3O4 nanoparticles exhibits a uniform, highly stable, and narrow particle size distribution of Fe3O4-Au nanoparticles with an average diameter of 9 ± 2 nm. The saturation magnetization value for the resulting nanoparticles was found to be 15 emu/g at 298 K. Subsequent surface modification with SAMs against glucoside moieties on the surface of bacteria provided effective magnetic separation. Comparison of the bacteria capturing efficiency, by means of different molecular recognition agents 3-MBA, 1-DT and the mixed monolayer of 3-MBA and 1-DT was presented. The best capturing efficiency of E. coli was achieved with the mixed monolayer of 3-MBA and 1-DT-modified nanoparticles. Molecular specificity and selectivity were also demonstrated by comparing the surface-enhanced Raman scattering (SERS) spectrum of E. coli-nanoparticle conjugates with bacterial growth media.

A multi-channel bioluminescent bacterial biosensor for the on-line detection of metals and toxicity. Part II: technical development and proof of concept of the biosensor.

This research study deals with the on-line detection of heavy metals and toxicity within the context of environmental pollution monitoring. It describes the construction and the proof of concept of a multi-channel bioluminescent bacterial biosensor in immobilized phase: Lumisens3. This new versatile device, designed for the non-stop analysis of water pollution, enables the insertion of any bioluminescent strains (inducible or constitutive), immobilized in a multi-well removable card. The technical design of Lumisens3 has benefited from both a classical and a robust approach and includes four main parts: (1) a dedicated removable card contains 64 wells, 3 mm in depth, arranged in eight grooves within which bacteria are immobilized, (2) this card is incubated on a Pelletier block with a CCD cooled camera on top for bioluminescence monitoring, (3) a fluidic network feeds the card with the sample to be analyzed and finally (4) a dedicated computer interface, BIOLUX 1.0, controls all the elements of the biosensor, allowing it to operate autonomously. The proof of concept of this biosensor was performed using a set of four bioluminescent bacteria (Escherichia coli DH1 pBzntlux, pBarslux, pBcoplux, and E. coli XL1 pBfiluxCDABE) in the online detection of CdCl(2) 0.5 µM and As(2)O(3) 5 µM from an influent. When considering metals individually, the "fingerprints" from the biosensor were as expected. However, when metals were mixed together, cross reaction and synergistic effects were detected. This biosensor allowed us to demonstrate the simultaneous on-line cross detection of one or several heavy metals as well as the measurement of the overall toxicity of the sample.

Spectroscopic investigation of polystyrene surface grafting on natural rubber.

This paper investigates the structural characteristics of polystyrene (PS) grafted on a natural rubber (NR) surface using Raman scattering spectroscopy. The nitroxide-mediated radical polymerization (NMRP) technique was used to achieve the graft copolymerization of PS onto the surface of NR film using 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) as a nitroxide mediator. The reversible reaction between propagating radical and TEMPO of the NMRP process leads to a controlled radical polymerization of styrene on the NR surface. The grafting degree of PS on the NR was first measured by gravimetric methods. It was found to depend linearly on the grafting time. The characteristic signals detected by Raman scattering and by attenuated total reflection (ATR) Fourier transform infrared (FT-IR) spectroscopy provide clear evidence of the PS being grafted onto the NR. The distribution of the grafted PS on the NR substrate was determined from the Raman mapping. It is seen that the grafting occurs homogeneously over the entire surface ( approximately 40 mole % PS). The study using the Raman depth profiling technique on the original sample compared with the analysis carried out on the sample prepared by cross-sectioning led to important and comparable information regarding the uniform distribution of PS grafting inside the substrate.

The Egg apparatus 1 gene from maize is a member of a large gene family found in both monocots and dicots.

The maize ZmEA1 protein was recently postulated to be involved in short-range pollen tube guidance from the embryo sac. To date, EA1-like sequences had only been identified in monocot species. Using a more conserved C-terminal motif found in the monocot species, numerous ZmEA1-like sequences were retrieved in EST databases from dicot species, as well as from unannotated genomic sequences of Arabidopsis thaliana. RT-PCR analyses were produced for these unannotated genes and showed that these were indeed expressed genes. Further structural and phylogenetic analyses revealed that all members of the EA1-like (EAL) gene family shared a conserved 27-29 amino acid motif, termed the EA box near the C-terminal end, and appear to be secretory proteins. Therefore, the EA box proteins defines a new class of small secretory proteins, some of which being possibly involved in pollen tube guidance.

Development of a biosensor for the detection of tributyltin.

A biosensor (LUMISENS I), based on the inducible bioluminescence of the Escherichia coli strain TBT3 (Ec::luxAB TBT3), was developed for the detection of the biocide tributyltin. LUMISENS I was set up with a minibioreactor and additional equipment for growth monitoring and light acquisition. The 100-mL minibioreactor has allowed us to establish a stable and reproducible environment for the bacteria (regulation of the growth rate, temperature, pH, and oxygenation), as well as for in situ contact with the xenobiotic. The optical components of the transducer were chosen according to the spectral emission of the strain being studied using a highly sensitive spectrophotometer that was initially devoted to Raman scattering. LUMISENS I was patented according to the in situ, automatic, and simultaneous measurement of the cell density and bioluminescence in the bioreactor. The first results showed that cells cultivated in a synthetic glucose medium provided a better detection limit than did those cultivated in a complex Luria-Bertani (LB) medium (0.02 and 1.5 microM of tributyltin, respectively). Cells maintained at a high growth rate (0.9 h(-1)) led to maximum bioluminescence. Moreover, air bubbling was efficient enough to provide suitable quantities of oxygen for both growth and light emission. When the TBT3 strain used the luxAB genes on its own, decanal, a long-chain aldehyde, had to be added to obtain the bioluminescence reaction. We found that the continuous addition of decanal was the most effective means of obtaining this reaction. The monitoring of the bioluminescence after tributyltin induction showed that the aldehyde was not toxic up to 300 microM during a 7-day experiment. Measurement of tributyltin with LUMISENS I was performed, which showed significant response up to 0.125 microM without any effect on optical density. Even though optimization of the performance of LUMISENS I is still under development, because of its original design, this biosensor is already in use as a warning system for the online monitoring of tributyltin.

Variación estacional de la preeclampsia. Hospital Nacional Arzobispo Loayza / Seasonal variation of pre-eclampsia. Arzobispo Loayza National Hospital

INTRODUCCION: Estudios recientes describen una variación estacional en la prevalencia de preeclampsia. La mayoría encuentra un aumento de la prevalencia en invierno. OBJETIVO: Determinar si en nuestro medio existe variación estacional o mensual en la prevalencia de la preeclampsia. DISEÑO: Estudio de tipo transversal descriptivo retrospectivo. MATERIAL Y MÉTODOS: Se revisó información de 7923 gestantes cuyo parto ocurrió entre el 1 de diciembre de 1999 y el 30 de noviembre de 2002, en el Hospital Arzobispo Loayza de Lima. Se identificó a las pacientes con preeclampsia leve y severa y se determinó mediante un análisis de regresión logística múltiple, la variación de la prevalencia de la enfermedad, en relación con el mes y la estación de parto. RESULTADOS: La prevalencia de preeclampsia fue 14,2 por ciento, siendo 28 por ciento de éstas severas. La prevalencia en septiembre (17,8 por ciento) y junio (17,3 por ciento) fue mayor respecto a febrero (11,1 por ciento) y diciembre (11,5 por ciento); por lo tanto, que hubo mayor prevalencia en invierno (16,6 por ciento) respecto al verano (12,7 por ciento) (p menor que 0,05; Para preeclampsia severa se encontró menor prevalencia en primavera (2,8 por ciento) respecto al verano (4,8 por ciento) (p menor que 0,05), por lo que la proporción de preeclampsia severa fue menor en primavera (21,4 por ciento) que en verano (38 por ciento) (p menor que 0,05). CONCLUSIONES: En nuestro medio, la prevalencia de la preeclampsia fue mayor en los meses fríos de primavera e invierno; la forma severa de la preeclampsia se presentó en menor proporción en estos meses.

BACKGROUND: Recent studies describe a seasonal variation on the prevalence of preeclampsia. Most of them find an increase in the prevalence in winter months. OBJETIVE: To determinate seasonal or monthly variations of preeclampsia prevalence in our settings. DESIGN: Transversal descriptive retrospective study. MATERIAL AND METHOS: We reviewed data from 7923 pregnant women who delivered at Arzobispo Loayza Hospital in Lima, between December 1, 1999, and November 30, 2002. We identified patients with mild severe preeclampsia and determined by multiple logistic regression analysis prevalence variation in relation to season and month of delivery. RESULTS: preeclampsia prevalence was 14,2 per cent, 28 per cent of cases severe preeclampsia. Prevalence was higher in September (17,8 per cent) and June (17,3 per cent) than in February (11,1 per cent) and December (11,5 per cent) (P less than 0,05); therefore prevalence was higher in winter (16,6 per cent) than in summer (12,7 per cent). Severe preeclampsia prevalence was longer in spring (2,8 per cent) compared to summer (4,8 per cent); as such, rate of severe preeclampsia was lower in spring (21,4 per cent) than in summer (38 per cent) (P less than 0,05). CONCLUSIONS: Season and month of birth influence preeclampsia prevalence; it is higher in the cold months of spring and winter. But the rate of severe forms of the disease is lower during these months.

Comparison of the spectral emission of lux recombinant and bioluminescent marine bacteria.

The purpose of the present paper was to study the influence of bacteria harbouring the luciferase-encoding Vibrio harveyi luxAB genes upon the spectral emission during growth in batch-culture conditions. In vivo bioluminescence spectra were compared from several bioluminescent strains, either naturally luminescent (Vibrio fischeri and Vibrio harveyi) or in recombinant strains (two Gram-negative Escherichia coli::luxAB strains and a Gram-positive Bacillus subtilis::luxAB strain). Spectral emission was recorded from 400 nm to 750 nm using a highly sensitive spectrometer initially devoted to Raman scattering. Two peaks were clearly identified, one at 491-500 nm (+/- 5 nm) and a second peak at 585-595 (+/- 5 nm) with the Raman CCD. The former peak was the only one detected with traditional spectrometers with a photomultiplier detector commonly used for spectral emission measurement, due to their lack of sensitivity and low resolution in the 550-650 nm window. When spectra were compared between all the studied bacteria, no difference was observed between natural or recombinant cells, between Gram-positive and Gram-negative strains, and growth conditions and growth medium were not found to modify the spectrum of light emission.

A comparison of two rapid field immunochromatographic tests to expert microscopy in the diagnosis of malaria.

In Myanmar, we tested two rapid malaria immunochromatographic kits: the OptiMAL assay for the detection of parasite lactate dehydrogenase (pLDH), and the ICT Malaria P.f./P.v. test for histidine-rich protein 2 (PfHRP2) and panmalarial antigens. A total of 229 patients were examined, of whom 133 were found to be malaria positive by Giemsa microscopy. Both OptiMAL and ICT gave lower sensitivities than previously reported. ICT sensitivity for Plasmodium falciparum and non-falciparum parasites were 86.2 and 2.9%, respectively; specificity was 76.9 and 100%, respectively. OptiMAL sensitivity for P. falciparum and non-falciparum parasites were 42.6 and 47.1%, respectively; specificity was 97.0 and 96.9%, respectively. The sensitivity of both tests for the detection of both P. falciparum and non-falciparum parasites increased with parasite density. Several explanations for these results are explored. Our results raise particular concern over batch quality variations of malaria rapid diagnostic devices (MRDDs).