Structure and origin of cometary nuclei

There is strong evidence that a comet nucleus consists of a single object whose basic structure is Whipple's icy conglomerate. A number of cometary phenomena indicate that the nucleus is a low density, fragile object with a large degree of radial uniformity in structure and composition. Details of the ice-dust pattern are more uncertain. A working model is proposed which is based on theories of accumulation of larger objects from grains. This nucleus is a distorted spherical aggregate of a hierarchy of ice-dust cometesimals. These cometesimals retain some separate identity which lead to comet fragmentation when larger components break off. The outer layers of new comets were modified by cosmic ray irradiation in the Oort Cloud. The evidence for meteorite-comet association is steill controversial. Current dynamical studies do not seem to require a cometary source of meteorites

Modern Observational Techniques for Comets

Techniques are discussed in the following areas: astrometry, photometry, infrared observations, radio observations, spectroscopy, imaging of coma and tail, image processing of observation. The determination of the chemical composition and physical structure of comets is highlighted

From C/Mrkos to P/Halley: 30 years of cometary spectroscopy

An Atlas of Cometary Spectra was compiled, as a sequel to the well-known Atlas published by Swings and Haser in 1956. The new atlas comprises some 400 reproductions of cometary spectra secured in the world's largest observatories during the three decades or so from the passage of comet Mrkos 1957 V, for which the very first high-dispersion spectrum was obtained, to the return of Halley's comet. The illustrations refer to 40 different comet apparitions; they are grouped into a set of 186 loose 11 x 14 in. plates, while the texts, comments, and relevant data are given in a separate booklet. The main purpose of this atlas is to show in detail the tremendous progress which was achieved in cometary spectroscopy during the period covered, essentially thanks to the use of high-resolution coude spectrographs and large telescopes, the considerable extension of the observed wavelength range, and the advent of electronic detectors. It is divided into two parts. Part 1, which contains about two-thirds of the selected material, presents photographic spectra, while electronically recorded spectra covering the vacuum ultraviolet, through the optical, infrared, and radio regions appear in Part 2

Sclerosing Mesenteritis

Background: A 55-year-old Caucasian man presented with weight loss, cramping abdominal pains, an increasing abdominal circumference and diarrhea. Physical examination showed no abnormalities besides a puffy abdomen. His past medical history included a recent subcutaneous swelling in the neck, histologically compatible to a benign solitary fibrous tumor. All blood results were within normal limits. Abdominal ultrasonography showed a tumor with diameter of 6.7 cm, probably originating from the pancreas, with ascites and retroperitoneal lymphadenopathy. This was followed by a CT scan. CT scan of the abdomen was repeated following therapy

Growth conditions of F9 embryonal carcinoma cells affect the degree of DNA methylation

We have investigated differences in C * pG methylation between F9 embryonal carcinoma cells in vitro and as tumor cells grown in vivo using Msp I and Hpa II restriction isoschizomers. Southerns were hybridized with two low copy number probes, mouse major β-globin (f7) and a class I, histocompatibility-2 cDNA clone (pH-2 d -4). In each case, the tumor-DNA was hypomethylated while the DNA from F9 cells grown in vitro was moderately methylated. We conclude that growth conditions or cell-cell interactions can greatly affect methylation of C * pG sites.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43248/1/11033_2004_Article_BF00776983.pd

Associations between depression subtypes, depression severity and diet quality: cross-sectional findings from the BiDirect study

Depression is supposed to be associated with an unhealthy lifestyle including poor diet. The objective of this study was to investigate differences in diet quality between patients with a clinical diagnosis of depression and population-based controls. Additionally, we aimed to examine effects of specific depression characteristics on diet by analyzing if diet quality varies between patients with distinct depression subtypes, and if depression severity is associated with diet quality.The study included 1660 participants from the BiDirect Study (n = 840 patients with depression, n = 820 population-based controls). The psychiatric assessment was based on clinical interviews and a combination of depression scales in order to provide the classification of depression subtypes and severity. Diet quality scores, reflecting the adherence to a healthy dietary pattern, were calculated on the basis of an 18-item food frequency questionnaire. Using analysis of covariance, we calculated adjusted means of diet quality scores and tested differences between groups (adjusted for socio-demographic, lifestyle-, and health-related factors).We found no differences in diet quality between controls and patients with depression if depression was considered as one entity. However, we did find differences between patients with distinct subtypes of depression. Patients with melancholic depression reported the highest diet quality scores, whereas patients with atypical depression reported the lowest scores. Depression severity was not associated with diet quality.Previous literature has commonly treated depression as a homogeneous entity. However, subtypes of depression may be associated with diet quality in different ways. Further studies are needed to enlighten the diet-depression relationship and the role of distinct depression subtypes.Corinna Rahe, Bernhard T Baune, Michael Unrath, Volker Arolt, Jürgen Wellmann, Heike Wersching and Klaus Berge

On the exchange of intersection and supremum of sigma-fields in filtering theory

We construct a stationary Markov process with trivial tail sigma-field and a nondegenerate observation process such that the corresponding nonlinear filtering process is not uniquely ergodic. This settles in the negative a conjecture of the author in the ergodic theory of nonlinear filters arising from an erroneous proof in the classic paper of H. Kunita (1971), wherein an exchange of intersection and supremum of sigma-fields is taken for granted.Comment: 20 page

Fenologia de três espécies de plantas daninhas de pastagem em uma área de ecótono Cerrado-Pantanal.

A competição das plantas daninhas com as forrageiras em áreas de pastagens ocorre desde o momento da semeadura e perdura até mesmo após o estabelecimento do pasto (DIAS-FILHO, 1990; DIAS-FILHO, 2006), sendo que o manejo destas plantas envolve práticas associadas ao controle mecânico (remoção das plantas), controle químico (uso de herbicidas) e a queima (SANTOS et al., 2006). Na pecuária, algumas plantas daninhas são indesejáveis por prejudicar a produção animal, competir com as forrageiras, serem tóxicas e/ou causarem ferimentos ao homem ou aos animais (POTT; POTT; SOUZA, 2006). Nos casos do Cerrado e do Pantanal, parte considerável das espécies daninhas de pastagens são plantas nativas, ou seja, já possuem associações com espécies locais e são oportunistas em relação à colonização de novos habitats (POTT; POTT; SOUZA, 2006; SANTOS et al., 2006). Uma vez que o conhecimento da fenologia de plantas daninhas é crucial para práticas de controle mais adequadas das mesmas (SPADOTT et al., 1994; DIAS et al., 2013), o objetivo deste trabalho foi registrar e caracterizar os eventos fenológicos de três espécies de plantas daninhas de pastagens em uma área de ecótono Cerrado-Pantanal: Croton campestris A. St.-Hil. (Euphorbiaceae), Sapium haematospermum Müll. Arg. (Euphorbiaceae) e Annona crassiflora Mart. (Annonaceae) e fornecer subsídios para o manejo e a conservação do ecótono Cerrado-Pantanal

Bimolecular porous supramolecular networks deposited from solution on layered materials: graphite, boron nitride and molybdenum disulphide

A two-dimensional porous network formed from perylene tetracarboxylic diimide (PTCDI) and melamine may be deposited from solution on the surfaces of highly oriented pyrolytic graphite (HOPG), hexagonal boron nitride (hBN) and molybdenum disulphide (MoS2). Images acquired using high resolution atomic force microscopy (AFM) operating under ambient conditions have revealed that the network forms extended orderedmonolayers (41 lm2) on HOPG and hBN whereas on MoS2 much smaller islands are observed

One-pot synthesis and AFM imaging of a triangular aramide macrocycle

Macrocyclizations in exceptionally good yields were observed during the self-condensation of N-benzylated phenyl p-aminobenzoates in the presence of LiHMDS to yield three-membered cyclic aramides that adopt a triangular shape. An ortho-alkyloxy side chain on the N-benzyl protecting group is necessary for the macrocyclization to occur. Linear polymers are formed exclusively in the absence of this Li-chelating group. A model that explains the lack of formation of other cyclic congeners and the demand for an N-(o-alkoxybenzyl) protecting group is provided on the basis of DFT calculations. High-resolution AFM imaging of the prepared molecular triangles on a calcite(10.4) surface shows individual molecules arranged in groups of four due to strong surface templating effects and hydrogen bonding between the molecular triangles