An evaluation of courses of study in mathematics for grades 9 to 12

Thesis (M.A.)--Boston UniversityThe purpose of this study was to evaluate courses of study in mathematics for grades 9-12. This evaluation was to determine: 1) what makes a good course of study, and 2) if there are many good courses of study existing at the present time. Only those courses of study in specialized mathematics that are being used in the high schools and which are available on request were considered

Conjunto mínimo de parâmetros para avaliação da microbiota do solo e da fixação biológica do nitrogênio pela soja.

O objetivo deste trabalho foi avaliar e validar um conjunto mínimo de parâmetros para o monitoramento, em campo, da microbiota do solo e da fixação biológica do N2 (FBN) pela soja. Os ensaios foram conduzidos em áreas de plantios comerciais (safra 2002/2003) e experimentais (safra 2004/2005), em blocos ao acaso. O C e o N da biomassa microbiana (CBM e NBM) mostraram-se adequados para a avaliação quantitativa da microbiota do solo e ambos os parâmetros foram correlacionados significativamente, portanto, apenas um deles precisa ser determinado. Foram obtidas correlações positivas e significativas entre a massa da parte aérea seca das plantas (MPAS) e o CBM e o NBM. A análise do DNA total do solo por eletroforese em géis desnaturantes (DGGE) detectou alterações qualitativas na microbiota do solo, relacionadas à homogeneidade da área e a diferenças entre tratamentos, áreas e coletas. A massa de nódulos secos (MNS) foi o melhor parâmetro para a avaliação da nodulação. Correlações significativas foram constatadas entre a MPAS e o N total acumulado na parte aérea (NTPA). Resultados semelhantes foram observados entre a MPAS e o N de ureídos (NTU). O monitoramento da FBN pela soja pode ser realizado apenas pela determinação da MNS e da MPAS

Staying alive on an active volcano. 80 years population dynamics of Cytisus aeolicus (Fabaceae) from Stromboli (Aeolian Islands, Italy)

Cytisus aeolicus is a narrow endemic species restricted to the Aeolian archipelago (SE Tyrrhenian Sea, Italy) and it is one of the most evolutionarily isolated plants in the Mediterranean flora. Historical and literature data suggest that both metapopulations and isolated individuals of C. aeolicus are gradually shrinking. Field investigations and drone images demonstrate that the C. aeolicus metapopulation from Stromboli experienced a strikingly fast increase during the last decades. As of 2019, more than 7000 ± 3000 mature individuals occur on Stromboli, i.e. 14 to 20 times more than those counted during the last census, 25 years ago. The diachronic analysis of aerial photos concerning last 80 years and the analysis of the growth rings of some selected plants pointed out that the surface occupied, the demographic structure and the distribution pattern of the subpopulations of Stromboli has been highly fluctuating during last decades. Moreover, data issuing from field observations in permanent plots placed in a transect between two isolated mature individuals showed that, under natural conditions, the germination rate of the seedlings of C. aeolicus can be very high and their establishment rate may exceed 40%. By contrast, seedlings mortality is subject to strong annual fluctuations. Additionally, the pollen morphology of the Strombolian metapopulation of this rare and isolated species is studied here for the first time. Contrary to what is stated in recent literature, the C. aeolicus metapopulation from Stromboli is healthy and very dynamic, albeit frequently damaged by the volcanic activity. Regular and repeated field surveys carried out during 3 years (2017–2019) allowed improving our knowledge on the life cycle of C. aeolicus and a new extinction risk assessment of the species, according to IUCN criteria, is presented

A Mechanistic Analysis of Phase Evolution and Hydrogen Storage Behavior in Nanocrystalline Mg(BH4)2 within Reduced Graphene Oxide.

Magnesium borohydride (Mg(BH4)2, abbreviated here MBH) has received tremendous attention as a promising onboard hydrogen storage medium due to its excellent gravimetric and volumetric hydrogen storage capacities. While the polymorphs of MBH-alpha (α), beta (β), and gamma (γ)-have distinct properties, their synthetic homogeneity can be difficult to control, mainly due to their structural complexity and similar thermodynamic properties. Here, we describe an effective approach for obtaining pure polymorphic phases of MBH nanomaterials within a reduced graphene oxide support (abbreviated MBHg) under mild conditions (60-190 °C under mild vacuum, 2 Torr), starting from two distinct samples initially dried under Ar and vacuum. Specifically, we selectively synthesize the thermodynamically stable α phase and metastable β phase from the γ-phase within the temperature range of 150-180 °C. The relevant underlying phase evolution mechanism is elucidated by theoretical thermodynamics and kinetic nucleation modeling. The resulting MBHg composites exhibit structural stability, resistance to oxidation, and partially reversible formation of diverse [BH4]- species during de- and rehydrogenation processes, rendering them intriguing candidates for further optimization toward hydrogen storage applications

Quantitative And Qualitative Analysis Of Microorganisms In Root-filled Teeth With Persistent Infection: Monitoring Of The Endodontic Retreatment.

The aim of this study was to investigate in vivo microorganisms detected in root-filled teeth with post-treatment apical periodontitis and quantify colony-forming units (CFU) during endodontic retreatment. Fifteen root-filled teeth had their previous gutta-percha removed and were randomly instrumented before being divided into three groups and medicated with either [Ca(OH)2 + 2% CHX gel], [Ca(OH)2 + 0.9% NaCl] or 2% CHX gel. Samples were taken after removal of gutta-percha (S1), after chemomechanical preparation using 2% CHX gel (S2), and after inter-appointment dressing (S3) for 7 or 14 days later. Cultivable bacteria recovered from infected root canals at the three stages were counted and identified by means of culture and PCR assay (16S rDNA). Quantitative data were statistically analyzed by using Mann-Whitney test in which pairs of groups were compared (P < 0.05). CFU counts decreased significantly from S1 to S2 (P < 0.05). No significant difference was found between S2 and S3 (P = 0.3093) for all three experimental groups. Chemomechanical preparation and intra-canal dressing promoted significant median reductions of 99.61% and 99.57%, respectively, in the number of bacteria compared to S1 samples. A total of 110 cultivable isolates were recovered by culture technique from 32 different species and 7 different genera. Out of the 13 target species-specific primer of bacteria analyzed, 11 were detected during endodontic retreatment. The great majority of taxa found in post-treatment samples were Gram-positive bacteria, although Gram-negative bacteria were found by molecular methods. Moreover, our results showed that gutta-percha removal and chemomechanical preparation are effective for root canal disinfection, whereas additional intra-canal dressing did not improve disinfection.7302-

Evaluation of the biocompatibility of root canal sealers using subcutaneous implants

The purpose of this study was to evaluate in vivo the biocompatibility of Endométhasone, Pulp Canal Sealer EWT and AH-Plus root canal sealers after implantation in rat connective tissue. Twenty-four Wistar-Furth rats were used. Polyethylene tubes were filled with the sealers and implanted into specific dorsal subdermal tissue sites of the rats. Implants were removed after 3, 7 and 30 days, fixed and processed for glycol methacrylate-embedding technique to be examined microscopically. On the 3rd day, there was a mild inflammatory reaction to Pulp Canal Sealer EWT implants, but a severe response to the other sealers with presence of acute inflammatory cells. On the 7th day, tissue organization was more evident with attenuation of the inflammatory reaction, especially for the AH-Plus implants. On the 30th day, connective tissue with few inflammatory cells was observed in contact with all sealer implants. In this time interval, the tissue in contact with Pulp Canal Sealer EWT implants was more organized, while the tissue close to Endométhasone and AH-Plus implants showed a mild persistent inflammatory reaction and had similar results to each other. In conclusion, the sealers had a similar pattern of irritation, which was more severe in the beginning and milder with time, in such a way that all sealers showed a persistent mild reaction. Pulp Canal Sealer EWT yielded better tissue organization than Endométhasone and AH-Plus, which, in turn, showed similar results to each other

Children’s coping styles and trauma symptoms after an explosion disaster

Background: The negative impact of trauma on children and adolescents is well documented. However, few studies have investigated the relationship between coping and trauma and distress symptoms after man-made disasters, especially those not related to war. Objective: This study investigated the relationship between children’s coping styles and their self-reported levels of trauma and distress symptoms after an explosion disaster in a residential area. Method: Participants were recruited through the local public school that served the affected residential area. A total of 333 children and adolescents from grades 3 through 10 participated in the study 16 months after the explosion. All participants filled out questionnaires to assess their trauma and distress symptoms as well as their coping strategies. The adolescents answered additional questions about pre-, peri-, and post-traumatic factors and filled out questionnaires about their trauma and distress symptoms, including aspects of somatization and negative affectivity. Results: The following variables were associated with a higher degree of trauma symptoms for children in grades 6 through 10 and explained 39% to 48% of the unique variance in these symptoms: female gender; the experience of traumatic events pre-disaster; the destruction of property or danger to life occurring during the disaster; the experience of traumatic events post-disaster; and the use of self-blame, emotion regulation, wishful thinking, and cognitive restructuring. For the younger children, pre-, peri-, and post-disaster factors were not measured. However, female gender and the use of self-blame as a coping strategy explained 26% of the variance in trauma symptoms. Conclusions: This study generally supports the findings of the limited literature addressing coping skills after man-made disasters. However, contrary to previous findings in community samples after episodes of terrorism, adaptive coping strategies such as cognitive restructuring were found to influence the variance of trauma and distress symptoms

The Genomic Diversity and Phylogenetic Relationship in the Family Iridoviridae

The Iridoviridae family are large viruses (∼120–200 nm) that contain a linear double-stranded DNA genome. The genomic size of Iridoviridae family members range from 105,903 bases encoding 97 open reading frames (ORFs) for frog virus 3 to 212,482 bases encoding 211 ORFs for Chilo iridescent virus. The family Iridoviridae is currently subdivided into five genera: Chloriridovirus, Iridovirus, Lymphocystivirus, Megalocytivirus, and Ranavirus. Iridoviruses have been found to infect invertebrates and poikilothermic vertebrates, including amphibians, reptiles, and fish. With such a diverse array of hosts, there is great diversity in gene content between different genera. To understand the origin of iridoviruses, we explored the phylogenetic relationship between individual iridoviruses and defined the core-set of genes shared by all members of the family. In order to further explore the evolutionary relationship between the Iridoviridae family repetitive sequences were identified and compared. Each genome was found to contain a set of unique repetitive sequences that could be used in future virus identification. Repeats common to more than one virus were also identified and changes in copy number between these repeats may provide a simple method to differentiate between very closely related virus strains. The results of this paper will be useful in identifying new iridoviruses and determining their relationship to other members of the family

Adenine interaction with and adsorption on Fe-ZSM-5 zeolites: A prebiotic chemistry study using different techniques

Most adsorption experiments are performed under conditions that did not exist on Earth before the life arose on it. Because adsorption is the first step for all other processes (protection against degradation and polymerization), it is important that it is performed under conditions that existed on prebiotic Earth. In this paper, we use an artificial seawater (seawater 4.0 Ga), which contains major cations and anions that could present on the oceans of the prebiotic Earth. In addition, zeolites, with substituted Fe in the framework, and adenine were probably common substances on the prebiotic Earth. Thus, study the interaction between them is an important issue in prebiotic chemistry. There are two main findings described in this paper. Firstly, zeolites with different Si/Fe ratios adsorbed adenine differently. Secondly, XAFS showed that, after treatments with seawater 4.0 Ga and adenine, an increase in the complexity of the system occurred. In general, salts of seawater 4.0 Ga did not affect the adsorption of adenine onto zeolites and adenine adsorbed less onto zeolites with iron isomorphically substituted. The C=C and NH2 groups of adenine interacted with the zeolites. Gypsum, formed from aqueous species dissolved in seawater 4.0 Ga, precipitated onto zeolites. EPR spectra of zeolites showed lines caused by Fe framework and Fe3+ species. TG curves of zeolites showed events caused by loss of water weakly bound to zeolite (in the 30-140 °C range), water bounded to iron species or cations from seawater 4.0 Ga or located in the cavities of zeolites (157-268 °C) and degradation of adenine adsorbed onto zeolites (360-600 °C). Mass loss follows almost the same order as the amount of adenine adsorbed onto zeolites. The XAFS spectrum showed that Fe3+ could be substituted into the framework of the Fe7-ZSM-5 zeolite