Modified perturbation theory approach for tt-bar production and decay

The modified perturbation theory (MPT), based on direct expansion of probabilities instead of amplitudes, allows one to avoid divergences in the phase-space integrals resulting from production and decay of unstable particles. In the present paper the range of applicability of MPT is determined numerically in the case of the process $e^+e^- \to (\gamma,Z) \to t\bar t \to W^{+}b:W^{-}\bar b$. It is shown that with the complete expansion in powers of the coupling constant (without Dyson resummation) MPT operates best at the energies located near the maximum of the cross-section and slightly above the maximum. In this region the MPT expansion within the next-to-leading order considerably exceeds in accuracy well-known DPA approach.Comment: LaTeX, 11 pages, 3 eps figure

OMS-bar scheme of UV renormalization in the presence of unstable fundamental particles

A generalization of the on-mass-shell scheme of UV renormalization (the OMS-bar scheme) to the case of presence of unstable fundamental particles (like W and Z bosons) is proposed. Its basic ingredients are as follows: (i) the renormalized mass coincides with a real part of the position of the complex pole of the corresponding propagator, (ii) the imaginary part of the on-shell self-energy coincides with the imaginary part of the complex pole position. The latter property implies the gauge-invariance of the imaginary part of the on-shell self-energy in the OMS-bar scheme and its connection with the lifetime of an unstable particle. Starting with the three-loops this connection becomes nontrivial.Comment: 8 pages, LaTeX, no figures. 3 references are added, 2 misprints are corrected, minor changes in the tex

Identification of a mosaic non-inherited small supernumerary ring chromosome 2: cytogenetic-molecular studies and genotype-phenotype correlation

Introduction: The identification of supernumerary marker chromosomes (SMCs) derived from all the autosomes is currently possible, but rarely by conventional cytogenetics alone. Supernumerary ring chromosomes (SRCs) account for about 10% of these cases. SRCs derived from chromosome 2 are unusual, and there are only a few cases reported in the literature. The severity of the phenotype depends on the type of the mosaicism, the percentage of cells affected by the genetic change and the chromosome involved. Methods: The authors report the case of a boy aged 8 referred for cytogenetic studies, presenting with behavior and learning problems, mental retardation with uncoordenated speech, attention deficit and hyperactivity (PHDA), as well as small slanting palpebral fissures. The karyotype was obtained from peripheral blood lymphocyte cultures using high resolution GTL banding and standard techniques. Fluorescence in situ hybridization (FISH) was performed using specific probes for the centromeric regions of all chromosomes (Chromoprobe Multiprobe - ISystem). Results: Cytogenetic analysis revealed two cell lines: one with a supernumerary marker ring chromosome, 47,XY,+r (52%), and a normal cell line, 46,XY (48%). The SRC was identified by FISH with the chromosome 2 centromeric probe. Since the parents had normal karyotypes, this abnormality was “de novo”. Final karyotype of the proband was: mos 47,XY,+r[26]/46,XY[24].ish r(2)(D2Z2+)dn. Discussion: The clinical description of this patient is in agreement with other reports of the literature. Molecular characterization by FISH analyses is an useful way of investigating the presence of euchromatin contained in a SMC and establishing new chromosomal syndromes. However, to better characterize this ring, in order to establish a more accurate genotype-phenotype correlation, more studies involving other technologies should be performed, thus allowing suitable genetic counsellin

Deleção cromossómica intersticial em 14q “de novo”: apresentação de um caso

Introdução: As deleções intersticiais são anomalias cromossómicas estruturais, desequilibradas, resultantes de dois pontos de quebra, frequentemente associadas a quadros clínicos anormais devido à perda de material genético ativo (eucromatina). As consequências fenotípicas dependem do segmento cromossómico perdido e do número de genes aí localizados. Material e Métodos: Os autores apresentam o caso de um indivíduo do sexo masculino, de 11 anos de idade, referenciado para estudo citogenético por apresentar um quadro clínico de atraso de desenvolvimento psicomotor, défice cognitivo e problemas de comportamento. Realizaram-se culturas sincronizadas de linfócitos de sangue periférico, bandas GTG de alta resolução e, posteriormente, estudos de hibridação in situ por fluorescência (FISH) com sondas de pintura cromossómica total e subtelomérica, específicas para o cromossoma 14. Resultados: A análise das metafases revelou a presença de uma anomalia estrutural no cromossoma 14, interpretada como uma deleção intersticial do segmento compreendido entre as bandas 14q24.3 e 14q32.1. A análise por FISH permitiu confirmar esta deleção intersticial. Como os cariótipos dos pais foram normais, conclui-se que esta anomalia cromossómica é “de novo”, estabelecendo-se o cariótipo do doente como: 46,XY,del(14)(q24.3q32.1).ish del(14)(wcp 14+,SHGC36156+)dn Discussão: A deleção intersticial encontrada no cromossoma 14 implica uma monossomia do segmento 14q24.3→14q32.1. As alterações descritas mais comuns, associadas a esta deleção, incluem ADPM e algumas malformações minor. Os autores apresentam este caso pela raridade da anomalia citogenética encontrada e comparam-no com a literatura atual

Diagnóstico Pré-natal de Síndrome de Wolf-Hirschhorn: a propósito de um caso

Introdução: O Síndrome de Wolf-Hirschhorn é uma patologia originada por uma deleção da região terminal do braço curto do cromossoma 4. O tamanho da deleção pode ser variável levando a um espectro alargado de manifestações clínicas. Em diagnóstico pré-natal (DPN), as alterações fetais mais frequentes incluem atraso do crescimento intra-uterino, lábio leporino e/ou fenda do palato e anomalias cardíacas. A prevalência estimada é de 1/50.000 nascimentos afetando duas vezes mais indivíduos do sexo feminino do que do sexo masculino. Objectivo: Apresentação de um caso de Síndrome de Wolf-Hirschhorn em DPN comparando-o com outros casos publicados. Material e métodos: Grávida com 17semanas de gestação, referenciada para estudos cromossómicos por idade materna avançada (35 anos) e rastreio bioquímico positivo para trissomia 18. A análise citogenética convencional dos amniócitos cultivados foi realizada de acordo com os métodos habituais usando bandas GTG. O estudo foi complementado por técnicas de citogenética molecular (FISH) utilizando-se a sonda específica para a região do Síndrome de Wolf-Hirschhorn. Resultados: O estudo cromossómico efetuado, revelou uma deleção na região terminal do braço curto do cromossoma 4. A análise por FISH confirmou a existência da deleção desta região, permitindo estabelecer o cariótipo 46,XX,del(4)(p15.3).ish del(4)(p16.3p16.3)(WCHR-). Os cariótipos efetuados aos pais foram normais. Conclusões: Discute-se a importância deste caso pela raridade da anomalia citogenética encontrada, assim como pela dificuldade em realizar o diagnóstico por citogenética convencional, em alguns destes casos, quando não se obtêm bandas de alta resolução

Clinical, cytogenetic and molecular findings of a “de novo” inv dup del (6q)

Introduction: Complex rearrangements resulting in inverted duplications contiguous to a terminal deletion (inv dup del) were first reported for the short arm of chromosome 8 in1976. Since then this type of structural anomaly has been described for an increasing number of chromosomes. In these rearrangements, the concomitant presence of a deletion and a duplication has important consequences in genotype-phenotype correlations. The authors describe the clinical findings and the cytogenetic characterization of a rare inv dup del involving the long arm of chromosome 6. Material and methods: A girl aged 5 was referred for subtelomeric studies with the indication of psychomotor retardation, autistic features and stereotipies. Chromosome analysis with high resolution GTL-banding was performed on metaphases obtained from cultured peripheral blood lymphocytes. Molecular studies included MLPA (Kits P036 and P070, MRC-Holland), FISH with subtelomeric and whole chromosome painting probes specific for chromosome 6, and cCGH techniques. Results: Initial MLPA studies detected a subtelomeric deletion in the long arm of chromosome 6; the subsequent karyotype revealed a structurally abnormal chromosome 6 with additional material in the end of the long arm. FISH analysis showed the deletion and demonstrated that the extra material was derived from chromosome 6; cCGH tecnhiques defined the extension and confirmed the breakpoints of the duplicated segment. Thus this rearrangement was interpreted as an inv dup del (6q). Since parental karyotypes were normal, this anomaly was considered “de novo”. Discussion: As far as we know this is the first description of a patient presenting with a “de novo” inv dup del (6q). We compare the clinical features in this child with the previously reported cases with either an isolated terminal deletion or a duplication of distal 6q. The authors enhance the importance of the combination of high resolution banding with molecular studies in the characterization of this rare rearrangement

Interstitial deletion 15q21 and Prader-Willi like syndrome phenotype: Case report

Introduction: Chromosome 15q interstitial deletions not involving the Prader-Willi/Angelman region are uncommon and poorly characterized. Very few cases of different segmental losses involving the 15q21 region have been reported at cytogenetic level. All the described patients present with moderate to several mental retardation and characteristic facial dysmorphic features. Some authors compare the similarity between the phenotype of these patients with some features of Prader-Willi syndrome (PWS). Methods: We report the case of a girl aged 8 referred for conventional cytogenetics and fluorescence in situ hybridization (FISH) for the PWS region, presenting with mental retardation, almond-shaped eyes, obesity, small hands with short fingers and diminished pigmentation of the hair. Results: The chromosomal analysis revealed an interstitial deletion of the long arm of chromosome 15, apparently between 15q21 and 15q22. Deletion at 15q11.2 (Prader-Willi/Angelman critical region) was excluded by FISH. To establish the exact breakpoints molecular studies were performed using bacterial artificial chromosome (BAC) clones spanning the 15q21.3 region. The absence of signal in this region defines the proband’s final karyotype as: 46,XX,del(15)(q21.3q21.3).ish del(15)(q21.3q21.3)(bA74K1-) Discussion: The authors emphasize the importance of complementary FISH and molecular studies in chromosomal abnormalities and compare the proband’s phenotype with similar cases described in the literature

Diagnóstico Citogenético em Líquidos Amnióticos Realizado entre 2000-2011 no Centro de Genética Médica Jacinto Magalhães, INSA, IP

Introdução: O diagnóstico pré-natal citogenético efetuado em líquido amniótico é um método seguro e fiável para deteção de anomalias cromossómicas fetais, sendo habitualmente realizado a partir das 15 semanas de gestação. Obtêm-se resultados, em média, após 8-10 dias de cultura dos amniócitos. Objectivo: Apresentar a estatística dos resultados obtidos na análise citogenética de líquidos amnióticos realizada na Unidade de Citogenética do Centro de Genética Médica Jacinto Magalhães entre 2000 e 2011, comparando-os com o descrito na literatura. Material e métodos: Entre janeiro de 2000 e dezembro de 2011 foram processados 10149 líquidos amnióticos. Os motivos para a realização da amniocentese foram, nomeadamente, idade materna avançada, anomalias ecográficas, marcadores ecográficos, rastreio bioquímico positivo, familiares com anomalias cromossómicas e risco de doença monogénica. Foram realizadas culturas de amniócitos de acordo com as técnicas convencionais de citogenética e os cromossomas identificados com bandas GTG ou GTL. Sempre que necessário efetuaram-se estudos de citogenética molecular (FISH) com as sondas adequadas ao esclarecimento do caso. Resultados: A análise revelou 342 cariótipos anormais (3,4%) dos quais 234 tinham anomalias numéricas e 108 estruturais. Os Síndromes de Down, de Edwards e de Turner foram as anomalias mais frequentes. Vinte e três culturas não cresceram, representando uma percentagem de 0,2% de insucesso. Conclusões: Os autores correlacionam os resultados obtidos com as indicações clínicas fornecidas e comparam-nas com o descrito na literatura. O presente estudo poderá ser utilizado para o estabelecimento de uma base de dados a nível nacional

Insights into corrosion behaviour of uncoated Mg alloys for biomedical applications in different aqueous media

MgCa and MgGd series of alloys are often reported as promising candidates for biomedical applications. In the present study, cytotoxicity and corrosion behavior of Mg1Ca and Mg10Gd alloys in different electrolytes (NaCl, PBS, MEM) have been investigated in order to make a direct comparison and understand the mechanisms behind their performance. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) were employed to analyze corrosion processes depending on media composition, whereas X-Ray diffraction (XRD) and scanning electron microscopy (SEM) were used to evaluate crystalline structure, phase composition and surface morphology of the corroded substrates after immersion in the different electrolytes. Moreover, cytotoxicity of the Mg alloys was assessed using the WST-1 reduction and lactate dehydrogenase (LDH) release assays in L929 mouse fibroblasts. The electrochemical results showed that Mg1Ca has a lower degradation rate when compared to Mg10Gd, due to the lower microgalvanic effects and the presence of Ca as an alloying element. Furthermore, the corrosion activity is reduced in MEM, for both alloys, when compared to NaCl and PBS. The cytotoxicity assays revealed that Mg10Gd was cytotoxic in all the conditions tested, while the toxicity of Mg1Ca was low. Overall, these findings show that Mg1Ca alloy presents a higher corrosion resistance and biocompatibility and is a promising material to be used in biomedical implants.This work was financed by Portugal 2020 through European Regional Development Fund (ERDF) in the frame of Operational Competitiveness and Internationalization Programme (POCI), in the scope of the project MAGICOAT POCI-01-0145-FEDER016597/PTDC/CTM-BIO/2170/2014 and in the scope of the project CICECO - Aveiro Institute of Materials, UIDB/50011/2020 & UIDP/50011/2020, financed by national funds through the Portuguese Foundation for Science and Technology/ MCTES. Furthermore, thanks are due to Portuguese Foundation for Science and Technology/MCTES for the financial support through national funds to EPI Unit (UIDB/04750/2020).info:eu-repo/semantics/publishedVersio

Two-Loop Helicity Amplitudes for Quark-Gluon Scattering in QCD and Gluino-Gluon Scattering in Supersymmetric Yang-Mills Theory

We present the two-loop QCD helicity amplitudes for quark-gluon scattering, and for quark-antiquark annihilation into two gluons. These amplitudes are relevant for next-to-next-to-leading order corrections to (polarized) jet production at hadron colliders. We give the results in the `t Hooft-Veltman and four-dimensional helicity (FDH) variants of dimensional regularization. The transition rules for converting the amplitudes between the different variants are much more intricate than for the previously discussed case of gluon-gluon scattering. Summing our two-loop expressions over helicities and colors, and converting to conventional dimensional regularization, gives results in complete agreement with those of Anastasiou, Glover, Oleari and Tejeda-Yeomans. We describe the amplitudes for 2 to 2 scattering in pure N=1 supersymmetric Yang-Mills theory, obtained from the QCD amplitudes by modifying the color representation and multiplicities, and verify supersymmetry Ward identities in the FDH scheme.Comment: 77 pages. v2: corrected errors in eqs. (3.7) and (3.8) for one-loop assembly; remaining results unaffecte