Tubular Surface Evolution for Segmentation of the Cingulum Bundle From DW-MRI

Presented at the 2nd MICCAI Workshop on Mathematical Foundations of Computational Anatomy: Geometrical and Statistical Methods for Biological Shape Variability Modeling, September 6th, 2008, Kimmel Center, New York, USA.This work provides a framework for modeling and extracting the Cingulum Bundle (CB) from Diffusion-Weighted Imagery (DW-MRI) of the brain. The CB is a tube-like structure in the brain that is of potentially of tremendous importance to clinicians since it may be helpful in diagnosing Schizophrenia. This structure consists of a collection of fibers in the brain that have locally similar diffusion patterns, but vary globally. Standard region-based segmentation techniques adapted to DW-MRI are not suitable here because the diffusion pattern of the CB cannot be described by a global set of simple statistics. Active surface models extended to DW-MRI are not suitable since they allow for arbitrary deformations that give rise to unlikely shapes, which do not respect the tubular geometry of the CB. In this work, we explicitly model the CB as a tube-like surface and construct a general class of energies defined on tube-like surfaces. An example energy of our framework is optimized by a tube that encloses a region that has locally similar diffusion patterns, which differ from the diffusion patterns immediately outside. Modeling the CB as a tube-like surface is a natural shape prior. Since a tube is characterized by a center-line and a radius function, the method is reduced to a 4D (center-line plus radius) curve evolution that is computationally much less costly than an arbitrary surface evolution. The method also provides the center-line of CB, which is potentially of clinical significance

Diffusion Tensor Imaging, Structural Connectivity, and Schizophrenia

A fundamental tenet of the “disconnectivity” theories of schizophrenia is that the disorder is ultimately caused by abnormal communication between spatially disparate brain structures. Given that the white matter fasciculi represent the primary infrastructure for long distance communication in the brain, abnormalities in these fiber bundles have been implicated in the etiology of schizophrenia. Diffusion tensor imaging (DTI) is a magnetic resonance imaging (MRI) technique that enables the visualization of white matter macrostructure in vivo, and which has provided unprecedented insight into the existence and nature of white matter abnormalities in schizophrenia. The paper begins with an overview of DTI and more commonly used diffusion metrics and moves on to a brief review of the schizophrenia literature. The functional implications of white matter abnormalities are considered, particularly with respect to myelin's role in modulating the transmission velocity of neural discharges. The paper concludes with a speculative hypothesis about the relationship between gray and white matter abnormalities associated with schizophrenia

The infuence of glycosidic linkage neighbors on disaccharide conformation in vacuum

Correct description of the free energy of conformation change of disaccharides is important in understanding a variety of biochemical processes and, ultimately, in the manufacture of better food and paper products. In this study, we determine the relative free energy of a series of 12 disaccharides in vacuum using replica exchange molecular dynamics (repMD) simulations. The chosen sugars and the novel application of this method allow the exploration of the role of glycosidic linkage neighbors in conformer stabilization. In line with expectations, we find that hydrogen bonding (and therefore energetically preferred conformations) are determined both by the nature of the glycosidic linkage (i.e., 1 f 2, 1 f 3, or 1 f 4), the C1 epimer of the of the nonreducing monosaccharide, and by the configuration of carbon atoms once removed from the glycosidic linkage. Contrary to suggestions by prior authors for repMD more generally, we also demonstrate that repMD provides enhanced sampling, relative to conventional MD simulations of equivalent length, for disaccharides in vacuum at 300 K.Fundação para a Ciência e a Tecnologia (FCT)SFRH/BPD/20555/2004/0GVLNational Science Foundation under Grant CHE-043132

Propylthiocyclopentadiene: A new synthetic route to complexes of iron and group 4 transition metals. Molecular structure of (C5H4SCH2CH2CH3)(2)ZrCl2

The use of the propylthio-substituted cyclopentadienylsodium salt leads to 1,1'-bis(propylthio) ferrocene and dichlorobis(propylthiocyclopentadienyl)zirconium, titanium or hafnium(IV). The structure of (C5H4SCH2CH2CH3)(2)ZrCl2 has been established by X-ray analysis (orthorhombic, Pbcn, a = 11.943(1) Angstrom, b = 6.883(2) Angstrom, c = 22.412(2) Angstrom, V = 1842.4(2) Angstrom(3), Z = 4, R(F) = 0.027). The complexes have been characterized by H-1 and C-13 NMR and electrochemical studies. The physico chemical properties of 1,1'-bis(propylthio) ferrocene are discussed by a molecular approach at the extended Huckel level

A global atmospheric electricity monitoring network for climate and geophysical research

The Global atmospheric Electric Circuit (GEC) is a fundamental coupling network of the climate system connecting electrically disturbed weather regions with fair weather regions across the planet. The GEC sustains the fair weather electric field (or potential gradient, PG) which is present globally and can be measured routinely at the surface using durable instrumentation such as modern electric field mills, which are now widely deployed internationally. In contrast to lightning or magnetic fields, fair weather PG cannot be measured remotely. Despite the existence of many PG datasets (both contemporary and historical), few attempts have been made to coordinate and integrate these fragmented surface measurements within a global framework. Such a synthesis is important elvinin order to fully study major influences on the GEC such as climate variations and space weather effects, as well as more local atmospheric electrical processes such as cloud electrification, lightning initiation, and dust and aerosol charging. The GloCAEM (Global Coordination of Atmospheric Electricity Measurements) project has brought together experts in atmospheric electricity to make the first steps towards an effective global network for atmospheric electricity monitoring, which will provide data in near real time. Data from all sites are available in identically-formatted files, at both one second and one minute temporal resolution, along with meteorological data (wherever available) for ease of interpretation of electrical measurements. This work describes the details of the GloCAEM database and presents what is likely to be the largest single analysis of PG data performed from multiple datasets at geographically distinct locations. Analysis of the diurnal variation in PG from all 17 GloCAEM sites demonstrates that the majority of sites show two daily maxima, characteristic of local influences on the PG, such as the sunrise effect. Data analysis methods to minimise such effects are presented and recommendations provided on the most suitable GloCAEM sites for the study of various scientific phenomena. The use of the dataset for a further understanding of the GEC is also demonstrated, in particular for more detailed characterization of day-to-day global circuit variability. Such coordinated effort enables deeper insight into PG phenomenology which goes beyond single-location PG measurements, providing a simple measurement of global thunderstorm variability on a day-to-day timescale. The creation of the GloCAEM database is likely to enable much more effective study of atmospheric electricity variables than has ever been possible before, which will improve our understanding of the role of atmospheric electricity in the complex processes underlying weather and climate

Metabolic Engineering of Pseudomonas putida KT2440 for enhanced rhamnolipid production

The production of chemicals and fuels is mainly based on fossil resources. The reduced availability of these resources and thus the increasing prices for crude oil as well as the resulting pollution of the environment require alternative strategies to be developed. One approach is the employment of microorganisms for the production of platform molecules using renewable resources as substrate. Biosurfactants, such as rhamnolipids, are an example for such products as they can be naturally produced by microorganisms and are biodegradable in contrast to chemical surfactants. The bio-based production of chemicals has to be efficient and sustainable to become competitive on the market. Several strategies can be applied to increase the efficiency of a microbial cell factory, e.g., streamlining the chassis. Here, we show the heterologous production of rhamnolipids with the non-pathogenic Pseudomonas putida KT2440 with the aim of increasing the yield. P. putida KT2440 is a well-characterized microorganism and its genome is sequenced and well annotated. Thus, the targeted removal of genes is possible and can lead to a reduction of the metabolic burden and by-product formation, which can result in a higher yield. Furthermore, the efficient supply of precursors is an important factor for optimized production processes. Rhamnolipids are amphiphilic molecules containing rhamnose and ß-hydroxy fatty acids. These precursors are synthesized by two pathways, the fatty acid de novo synthesis and the rhamnose pathway. We performed gene deletions to avoid the synthesis of by-products, like pyoverdine, exopolysaccharides, and large surface proteins and energy consuming devices as the flagellum. Most of the genome-reduced mutants reached a higher yield compared to the strain with wildtype background. With the best chassis, the yield could be increased by 35%. Furthermore, we conducted the overexpression of genes for precursor supply, either plasmid-based or genomically integrated. In this regard, the genes for the phosphoglucomutase, the complete rhamnose-synthesis pathway operon, and different enzymes in the pathway for acetyl-CoA synthesis were targeted. Various combinations were tested, and the highest yield reached was 51% higher compared to the initial rhamnolipid producer. Finally, a genome-reduced mutant was equipped with the overexpression modules and the rhamnolipid titer was increased from approximately 590 mg/L for the wildtype background to 960 mg/L, which represents a 63% increase. In conclusion, we were able to enhance the yield of rhamnolipids per glucose using metabolic engineering

Three isomeric 4-[(n-bromophenyl)carbamoyl]butanoic acids (n =2,3 and 4) as DNA intercalator: Synthesis, physiochemical characterization, antimicrobial activity, antioxidant potential and in silico study

A series of three isomeric 4-[(n-bromophenyl)carbamoyl]butanoic acids (n=2,3 and 4) were synthesized and their structures confirmed by FTIR, NMR, MS, micro elemental analysis (CHN) and single crystal X-ray crystallography. Kinks are noted in the molecular structures of the n=2 and n=3 compounds, namely about the methylene-C–C(carbonyl) and N–C(phenyl) bonds; no such twist about the former bond is seen in the n=4 molecule. In the molecular packing, supramolecular tapes are carboxylic acid-O-H…O(carbonyl) and amide-N-H…O(amide) hydrogen bonds. The compounds were evaluated for interaction with salmon sperm DNA and found that they bind via an intercalative mode resulting in hypochromism and bathochromic shift as confirmed by the UV-visible spectroscopic and viscometric techniques. The results of antimicrobial activity performed against five bacterial and two fungal strains show that these compounds have < 50% inhibition. The DPPH antioxidant activity results revealed 78% maximum scavenging activity. An in silico study performed using the SwissADME webserver revealed the compounds obey the rules of drug-likeness and exhibit good potential for bioavailability