Thermal modeling of lesion growth with radiofrequency ablation devices

BACKGROUND: Temperature is a frequently used parameter to describe the predicted size of lesions computed by computational models. In many cases, however, temperature correlates poorly with lesion size. Although many studies have been conducted to characterize the relationship between time-temperature exposure of tissue heating to cell damage, to date these relationships have not been employed in a finite element model. METHODS: We present an axisymmetric two-dimensional finite element model that calculates cell damage in tissues and compare lesion sizes using common tissue damage and iso-temperature contour definitions. The model accounts for both temperature-dependent changes in the electrical conductivity of tissue as well as tissue damage-dependent changes in local tissue perfusion. The data is validated using excised porcine liver tissues. RESULTS: The data demonstrate the size of thermal lesions is grossly overestimated when calculated using traditional temperature isocontours of 42°C and 47°C. The computational model results predicted lesion dimensions that were within 5% of the experimental measurements. CONCLUSION: When modeling radiofrequency ablation problems, temperature isotherms may not be representative of actual tissue damage patterns

Ablation of Dido3 compromises lineage commitment of stem cells in vitro and during early embryonic development

The death inducer obliterator (Dido) locus encodes three protein isoforms, of which Dido3 is the largest and most broadly expressed. Dido3 is a nuclear protein that forms part of the spindle assembly checkpoint (SAC) and is necessary for correct chromosome segregation in somatic and germ cells. Here we report that specific ablation of Dido3 function in mice causes lethal developmental defects at the onset of gastrulation. Although these defects are associated with centrosome amplification, spindle malformation and a DNA damage response, we provide evidence that embryonic lethality of the Dido3 mutation cannot be explained by its impact on chromosome segregation alone. We show that loss of Dido3 expression compromises differentiation of embryonic stem cells in vitro and of epiblast cells in vivo, resulting in early embryonic death at around day 8.5 of gestation. Close analysis of Dido3 mutant embryoid bodies indicates that ablation of Dido3, rather than producing a generalized differentiation blockade, delays the onset of lineage commitment at the primitive endoderm specification stage. The dual role of Dido3 in chromosome segregation and stem cell differentiation supports the implication of SAC components in stem cell fate decisions

Rac1-Dependent Collective Cell Migration Is Required for Specification of the Anterior-Posterior Body Axis of the Mouse

Live imaging and analysis of conditional mutants show that the embryonic organizer that determines the anterior-posterior axis in the mouse embryo moves by Rac1-dependent collective cell migration

Deformability of poly(amidoamine) dendrimers

Experimental data indicates that poly(amidoamine) (PAMAM) dendrimers flatten when in contact with a substrate, i.e. they are no longer spherical, but resemble flat disks. In order to better understand the deformation behavior of these branched polymers, a series of atomistic molecular dynamics simulations is performed. The resulting flattened dendrimer conformations are compared to atomic force microscopy (AFM) images of individual dendrimers at air/mica and water/mica interfaces. The ability of the polymers to deform is investigated as a function of dendrimer generation (2-5) and the required energies are calculated. Our modeling results show good agreement with the experimental AFM images, namely that dendrimers are highly flexible and capable of forming multiple interaction sites between most of their branch ends and the substrate. The deformation energy scales with dendrimer generation and does not indicate an increase in stiffness between generations 2 and 5 due to steric effects.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45831/1/10189_2003_Article_10087.pd

In quest of a systematic framework for unifying and defining nanoscience

This article proposes a systematic framework for unifying and defining nanoscience based on historic first principles and step logic that led to a “central paradigm” (i.e., unifying framework) for traditional elemental/small-molecule chemistry. As such, a Nanomaterials classification roadmap is proposed, which divides all nanomatter into Category I: discrete, well-defined and Category II: statistical, undefined nanoparticles. We consider only Category I, well-defined nanoparticles which are >90% monodisperse as a function of Critical Nanoscale Design Parameters (CNDPs) defined according to: (a) size, (b) shape, (c) surface chemistry, (d) flexibility, and (e) elemental composition. Classified as either hard (H) (i.e., inorganic-based) or soft (S) (i.e., organic-based) categories, these nanoparticles were found to manifest pervasive atom mimicry features that included: (1) a dominance of zero-dimensional (0D) core–shell nanoarchitectures, (2) the ability to self-assemble or chemically bond as discrete, quantized nanounits, and (3) exhibited well-defined nanoscale valencies and stoichiometries reminiscent of atom-based elements. These discrete nanoparticle categories are referred to as hard or soft particle nanoelements. Many examples describing chemical bonding/assembly of these nanoelements have been reported in the literature. We refer to these hard:hard (H-n:H-n), soft:soft (S-n:S-n), or hard:soft (H-n:S-n) nanoelement combinations as nanocompounds. Due to their quantized features, many nanoelement and nanocompound categories are reported to exhibit well-defined nanoperiodic property patterns. These periodic property patterns are dependent on their quantized nanofeatures (CNDPs) and dramatically influence intrinsic physicochemical properties (i.e., melting points, reactivity/self-assembly, sterics, and nanoencapsulation), as well as important functional/performance properties (i.e., magnetic, photonic, electronic, and toxicologic properties). We propose this perspective as a modest first step toward more clearly defining synthetic nanochemistry as well as providing a systematic framework for unifying nanoscience. With further progress, one should anticipate the evolution of future nanoperiodic table(s) suitable for predicting important risk/benefit boundaries in the field of nanoscience

What Mathematical Competencies Must Be Form in a New Ukrainian School: the Opinion of Teachers

У статті подано стислий опис і результати дослідження проблеми математичних компетеннтостей, проведеного у Львівському обласному інституті післядипломної педагогічної освіти у 2015-2019 роках за участю понад 500 учителів математики шкіл Львівської області. Формулювання проблеми. Метою дослідження було з’ясування ставлення вчителів математики до компетентнісного підходу та їхнього бачення математичних компетентностей учнів. У процесі дослідження з учителями обговорювався зміст поняття «математичні компетентності» – основного об’єкту дослідження. Матеріали і методи. Головним методом дослідження було опитування вчителів математики – слухачів курсів підвищення кваліфікації. Від стандартного анкетування дослідження відрізнялися тим, що в кожній із залучених у дослідження групі, під час заняття на тему «Компетентісний підхід в освіті», спершу проводилося обговорення заміни старого принципу політехнізму принципом життєвої практичності. Потім слухачам пропонувалося самостійно виписали ті математичні компетентності (знання-уміння-навички), що їх на думку вчителів, усі учні дійсно застосують у своєму повсякденному житті. Після обговорення виписаних учителями змістових опцій кожна група випрацьовувала спільний перелік наскрізних змістових ліній шкільної математичної освіти. Результати. Результати дослідження відображають колективну думку вчителів математики Львівської області щодо реалізації компетентнісного підходу у формуванні змісту математичної освіти у новій українській школі, на підставі якої нами було зроблемо наступні висновки Висновки. Політехнічний принцип формування змісту шкільної математичної освіти доцільно замінити принципом життєвої практичності, при якому «компетентності учня» трактуються як «життєві компетентності», тобто такі знання, уміння та навички, які кожен учень дійсно застосує у типових життєвих ситуаціях. Навчання математики слід здійснювати за п’ятьма наскрізними змістовими лініями: арифметичною, алгебраїчною, геометричною, стохастичною та логічною. Змістові одиниці треба деталізувати як конкретні відомості, уміння та навичок учнів і викласти їх у відповідній (віковим особливостям учнів і логічній структурі математики) послідовності.The article gives a brief description and results of the study of the problem of mathematical competencies, conducted at the Lviv regional institute of postgraduate pedagogical education in 2015-2019, with participation of more than 500 mathematics teachers of Lviv region schools. Formulation of the problem. The aim of the research was to find out the attitude of mathematics teachers to the competence approach and their vision of mathematical competencies of students. In the course of research with teachers, the content of the concept of "mathematical competence" – the main object of research was discussed. Materials and methods. The main method of research was the survey of teachers of mathematics – students of advanced training courses. From the standard questionnaire, the research was distinguished by the fact that in each of the groups involved in the study, during the class on "Competent approach in education," the discussion on replacing the old principle of polytechnics with the principle of practical life was discussed first. Then, students were offered to independently write down those mathematical competences (knowledge-skills-attainment), which, in the opinion of teachers, all students really apply in their daily lives. After discussing the content-based options provided by the teachers, each group developed a joint list of through-the-line content lines of school mathematical education. Results. The results of the research reflect the collective opinion of the teachers of mathematics in the Lviv region on the implementation of a competent approach in the formation of the content of mathematical education in the new Ukrainian school, on the basis of which we were able to draw the following conclusions. Conclusions. The polytechnic principle of forming the content of school mathematical education is expedient to replace the principle of practical life, in which the "student competence" is interpreted as "life competence", that is, the knowledge, skills and skills that each student will actually apply in typical life situations; the teaching of mathematics should be done through five cross-cutting content lines: arithmetic, algebraic, geometric, stochastic and logical; these content units should be detailed as specific information, skills and skills of students and put them in the corresponding (age-specific features of the students and the logical structure of mathematics) sequence