Últimos itens adicionados do Acervo: Proceedings Nature

Nature é uma das mais prestigiosas e antigas revistas científicas do mundo: sua primeira edição é de 4 de novembro de 1869. Entre as inúmeras descobertas científicas publicadas na Nature estão a dos raios X, da estrutura em dupla hélice do ADN e o buraco na camada de ozônio.

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‣ Partial Dissociation and Hydration Quantitatively Explain the Properties of Aqueous Electrolyte Solutions and hence Empirical Activity Concepts are Unnecessary

Raji Heyrovska
Fonte: Nature Preceedings Publicador: Nature Preceedings
Tipo: Manuscript
Português
The author shows that Arrhenius's theory of partial electrolytic dissociation was immaturely displaced about eight decades ago by the empirical concept of ionic activities and the assumption of complete dissociation of electrolytes at all concentrations. The latter brought the theory of electrolytes over the next decades into a complicated state without any physical significance. Therefore, the author started a systematic investigation of the available data and could completely restore the original theory of partial dissociation. Now solution properties can be easily understood and quantitatively explained in terms of absolute concentrations and volumes of ions and ion pairs and hydration.

‣ CellML: current status and future directions

David Nickerson
Fonte: Nature Preceedings Publicador: Nature Preceedings
Tipo: Conferência ou Objeto de Conferência
Português
An overview of the current status of the CellML project and some ideas on where things are heading.

‣ Comparison of histopathological features of Vibrio cholerae O1 El Tor and O139 Bengal infections in rabbit intestinal mucosa

Atif A. Baig
Fonte: Nature Preceedings Publicador: Nature Preceedings
Tipo: Conferência ou Objeto de Conferência
Português
Vibrio cholerae is the causative agent of the infectious disease, cholera. The bacteria adhere to the mucosal membrane and release cholera toxin, leading to watery diarrhea. There are >100 serovars of V. cholerae, but the O1 and O139 serovars are the main causative agents of cholera. The present study aimed to compare the severity of intestinal mucosal infection caused by O1 El Tor and O139 V. cholerae in a rabbit ileal loop model. The results showed that although the fluid accumulation was similar in the loops inoculated with O1 and O139 V. cholerae, the presence of blood was detected only in the loops inoculated with the O139 serovar. Serosal hemorrhage was confirmed by histopathological examination and the loops inoculated with O139 showed massive destruction of villi and loss of intestinal glands. The submucosa and muscularis mucosa of the ileum showed the presence of edema with congested blood vessels, while severe hemorrhage was seen in the muscularis propria layer. The loops inoculated with O1 El Tor showed only minimal damage, with intact intestinal villi and glands. Diffuse colonies of the O139 serovar were seen to have infiltrated deep into the submucosal layer of the intestine. Although the infection caused by the O1 serovar was focal and invasive...

‣ Marked Rise in Replikin Counts in H5N1 Influenza Virus Localized to Lethality Gene p B1.

Samuel Bogoch; Elenore S. Bogoch
Fonte: Nature Preceedings Publicador: Nature Preceedings
Tipo: Manuscript
Português
Abstract: Virus outbreaks have been found to be related to the concentration of a new class of genomic peptides, Replikins^1^. The eight genes of H5N1 influenza virus were analyzed for the distribution of Replikin Counts (number Replikins /100 amino acids) in 2,441 sequences from birds and humans. An increase (p<0.001) occurred from 2004 to August 2011 in one gene, pB1.

‣ Gas phase enthalpies of formation, isomerization, and disproportionation of mono- through tetra-substituted tetrahedranes: A G4MP2/G4 theoretical study

Sierra Rayne; Kaya Forest
Fonte: Nature Preceedings Publicador: Nature Preceedings
Tipo: Manuscript
Português
Gas phase (298.15 K, 1 atm) enthalpies of formation (Δ~f~H°~(g)~), enthalpies of disproportionation to two corresponding acetylene molecules (Δ~rxn~H°~(g),Td→acet~), and enthalpies of isomerization from a tetrahedrane geometry to a 1,3-cyclobutadiene structure (Δ~isom~H°~(g),Td→CBD~) were calculated for the mono- through tetra-substituted hydro, fluoro, chloro, bromo, methyl, ethynyl, and cyano carbon tetrahedrane derivatives at the G4MP2 and G4 levels of theory. All derivatives have endothermic Δ~f~H°~(g)~ indicative of the cage strain in these systems. In all cases, Δ~rxn~H°~(g),Td→acet~ and Δ~isom~H°~(g),Td→CBD~ are predicted to be substantially exothermic. High quality linear regression fits within a homologous series were obtained between the number of substituents and the G4MP2/G4 estimated Δ~f~H°~(g)~. Via calculations on lower homolog members, this strategy was employed to allow extrapolated G4 and/or G4MP2 Δ~f~H°~(g)~ (as well as some Δ~rxn~H°~(g),Td→acet~ and Δ~isom~H°~(g),Td→CBD~) to be obtained for the mono- through tetra-substituted t-butyl, trifluoromethyl, and trimethylsilyl carbon tetrahedrane derivatives.

‣ Annual cycle of aerosol backscatter coefficient and aerosol mixed layer height above Neuchâtel (Switzerland, 47.00°N, 6.95°E)

Manoj K Srivastava; Max Frioud; Renoud Matthey; Valentin Mitev
Fonte: Nature Preceedings Publicador: Nature Preceedings
Tipo: Poster
Português
Due to the complexity of the direct and indirect effects of the atmospheric aerosols on the air quality and atmospheric radiation balance, complementary methods are necessary to assess the aerosol optical properties. In this sense the backscatter lidar methods are critical in aerosol vertical distribution study. This work presents the annual cycle of aerosol backscatter coefficient (ABC) and aerosol mixed layer (AML) height over Neuchâtel, Switzerland (47.00 N; 6.950 E, 485 m asl). The study is performed by a ground based backscatter lidar operating at 532 nm wavelength as part of EARLINET program of EU. Atmospheric layering for this study is based on a classification of lower atmosphere from 1 km to 2 km above sea level (asl) and from 2 km to 5 km asl, respectively.

‣ Enzyme activities in brown forest soils after introduction of Bacillus thuringiensis-based bioinsecticides

Hasmik S. Movsesyan; Arevik M. Sargsyan; Naira P. Ghazaryan
Fonte: Nature Preceedings Publicador: Nature Preceedings
Tipo: Poster
Português
Much attention in the complex of forest pest control methods nowadays is devoted to the application of biological preparations, especially to bacterial formulations produced on the base of Bacillus thuringiensis (BT) that in addition to their high biological effectiveness against injurious insects are safe for man, homoiоtherms, beneficial insects and fish. As is known only 20-40% of sprayed preparation influences directly on pests while its 60-80% by different ways eventually penetrates into the soil. Taking into account also the fact that usage norm of commercial bacterial preparations makes up to 1-3 kg ha^-1^ and that preparation powder contains 45-100 billion viable spores g^-1^ it becomes evident that as a result of spraying huge quantity of bacterial stimulants introduces into the forest soils. In this connection a goal was set to determine the impact of some separately applied domestic insecticides of BT species (BT кб-1, BT кб-2, BT(SAR)-49, BT(SAR)-54, BT(SAR)-86, BT subsp. thuringiensis) introduced into the brown forest soils after spraying on soil enzymatic activity (invertase, urease) defining its fertility. Studies were conducted in 2010 under laboratory conditions. The results obtained indicate that in soils sprayed and non-sprayed by bioinsecticides the activities of invertase and urease undergo to changes from May to August. Maximal activities in soils were registered in June (25.641mg C~6~H~12~O~6~ g^-1^ for invertase and 12.254 mg NH~3~ g^-1^ for urease) and minimal – in May (20.643 mg C~6~H~12~O~6~ g^-1^ for invertase) and in August (9.297 mg NH~3~ g^-1^ for urease) at the average for all variants. By statistical analysis of study results it has been established that there aren’t any significant differences between indices of enzyme activities in sprayed and non-sprayed by biopesticides soils. Study results have led us to the assumption that tested insecticides don’t influence adversely on enzyme activities of brown forest soils and can be widely used in the field of plant protection.

‣ Dynamical patterns of human postural responses to emotional stimuli

Pandelis Perakakis; Jaime Vila; Sofia Idrissi; Plamen Ivanov
Fonte: Nature Preceedings Publicador: Nature Preceedings
Tipo: Manuscript
Português
Erotic scenes and images of mutilated bodies are emotional stimuli that have repeatedly shown to evoke specific neurophysiological responses associated with enhanced attention and perceptual processing. Remarkably however, only a handful of studies have investigated human motor reactions to emotional activation as a direct index of physical approximation or withdrawal. Given the inconclusive results of these studies, the approach-avoidance distinction, one of the most salient concepts in human motivational research, remains a broadly exploited hypothesis that has never been empirically demonstrated. Here, we investigate postural responses elicited by discrete emotional stimuli in healthy young adults. We discover that both positive and negative affective pictures induce a significant posterior deviation from postural baseline equilibrium. Further, we find that neutral pictures also evoke posterior deviation, although with a less pronounced amplitude. Exploring the dynamical evolution of postural responses to emotional pictures at high temporal resolution, we uncover a characteristic profile that remains stable for stimuli from all three affective categories. In contrast, the postural response amplitude is modulated by the emotional content of the stimulus. Our observations do not support the interpretation of postural responses to affective picture-viewing as approach-avoidance behavior. Instead...

‣ The computational magic of the ventral stream

Tomaso Poggio
Fonte: Nature Preceedings Publicador: Nature Preceedings
Tipo: Manuscript
Português
I argue that the sample complexity of (biological, feedforward) object recognition is mostly due to geometric image transformations and conjecture that a main goal of the ventral stream – V1, V2, V4 and IT – is to learn-and-discount image transformations. In the first part of the paper I describe a class of simple and biologically plausible memory-based modules that learn transformations from unsupervised visual experience. The main theorems show that these modules provide (for every object) a signature which is invariant to local affine transformations and approximately invariant for other transformations. I also prove that, in a broad class of hierarchical architectures, signatures remain invariant from layer to layer. The identification of these memory-based modules with complex (and simple) cells in visual areas leads to a theory of invariant recognition for the ventral stream. In the second part, I outline a theory about hierarchical architectures that can learn invariance to transformations. I show that the memory complexity of learning affine transformations is drastically reduced in a hierarchical architecture that factorizes transformations in terms of the subgroup of translations and the subgroups of rotations and scalings. I then show how translations are automatically selected as the only learnable transformations during development by enforcing small apertures – eg small receptive fields – in the first layer. In a third part I show that the transformations represented in each area can be optimized in terms of storage and robustness...

‣ PrionOme: A database of prions and other sequences relevant to prion phenomena

Djamel Harbi; Marimuthu Parthiban; Deena Gendoo; Sepehr Ehsani; Manish Kumar; Gerold Schmitt-Ulms; Ramanathan Sowdhamini; Paul M. Harrison
Fonte: Nature Preceedings Publicador: Nature Preceedings
Tipo: Manuscript
Português
Prions are units of propagation of an altered state of a protein or proteins. Prions can propagate from cell to cell, and from organism to organism, through cooption of other protein copies. Prions contain no necessary nucleic acids, and are important both as both pathogenic agents, and as a potential force in epigenetic phenomena. The original prions were derived from a misfolded form of the mammalian Prion Protein PrP. Infection by these prions causes neurodegenerative diseases. Other prions cause non-Mendelian inheritance in budding yeast, and sometimes act as diseases of yeast. We have compiled a database of >2000 prion-related sequences, called the PrionOme. The database comprises seven PrionOme classification categories: prionogenic sequences (i.e., sequences that can make prions), ‘prionoids’ (i.e., phenomena that have some prion characteristics), orthologs, paralogs, pseudogenes, prion interactors, and prion-like molecules. Database entries list: supporting information for PrionOme classifications, prion-determinant areas (where relevant), and disordered and compositionally-biased regions. Also included are original references for the PrionOme classifications, transcripts and genomic coordinates, and structural data (including comparative models). We provide database usage examples for both vertebrate and fungal prion contexts. As development of this resource is on-going...

‣ Weight, Length, and Growth in Cutbow Trout (Oncorhynchus mykiss x clarkii)

David Parker; Thomas Avers; Michael Courtney
Fonte: Nature Preceedings Publicador: Nature Preceedings
Tipo: Manuscript
Português
Background: The cutbow trout (Oncorhynchus mykiss x clarkii) is a fertile hybrid of rainbow and cutthroat trout. Little published length-weight data is available for this hybrid, and a standard weight curve is not established. Eleven Mile Reservoir is a clear mountain reservior in Colorado with a surface area of 13.4 square kilometers, an average depth of 10 m, and a maximum depth of 41 m. 80,000 cutbow trout were stocked through the ice in late winter before samples were taken. Materials and Methods: Angling provided 171 samples which were weighed and measured (total length and fork length). Dressed weight was also determined with the scales, head, and entrails removed. Estimates of parameters a and b in the model, W(L) = aLb, were obtained by both linear least-squares (LLS) regression (log(W) = log(a) + b log(L)) and non-linear least-squares (NLLS) regression, where W is weight in kg and L is length in cm. Parameter estimates of an improved model, W(L) = (L/L1)b, were also determined by NLLS regression; the parameter L1 is the typical length of a fish weighing 1 kg. The resulting best-fit parameters, parameter standard errors, and covariances are compared between the two models. Average weight and length are considered for each month from June through October to estimate growth rates for fish stocked over the winter. Standard weights (relative to the rainbow trout and cutthroat trout standard weight curves) are also determined...

‣ Comment on "Embryological evidence identifies wing digits in birds as digits 1, 2, and 3."

Xing Xu; Jonah Choiniere; Corwin Sullivan; Fenglu Han
Fonte: Nature Preceedings Publicador: Nature Preceedings
Tipo: Manuscript
Português
Tamura et al. (Science, 11 Febuary 2011, p. 753) claim that the three avian wing digits should be identified as digits I-III based on new embryological data and suggest that these identifications help to remove the conflict between the paleontological data and developmental data concerning the homology of the avian digits. However, their results are not novel, and the authors fail to address the critical problems relating to this interesting issue.

‣ ChemTextMiner: An open source tool kit for mining medical literature abstracts

Muthukumarasamy Karthikeyan; Yogesh Pandit; Deepak Pandit; Ganesh Nainaru; Sunil Nalwade; Renu Vyas; Esha Jain
Fonte: Nature Preceedings Publicador: Nature Preceedings
Tipo: Poster
Português
Text mining involves recognizing patterns from a wealth of information hidden latent in unstructured text and deducing explicit relationships among data entities by using data mining tools. Text mining of Biomedical literature is essential for building biological network connecting genes, proteins, drugs, therapeutic categories, side effects etc. related to diseases of interest. We present an approach for textmining biomedical literature mostly in terms of not so obvious hidden relationships and build biological network applied for the textmining of important human diseases like MTB, Malaria, Alzheimer and Diabetes. The methods, tools and data used for building biological networks using a distributed computing environment previously used for ChemXtreme[1] and ChemStar[2] applications are also described.

‣ BioSharing: Standards, Policies and Communication in Bioscience

Dawn Field; Susanna-Assunta Sansone; Philippe Rocca-Serra
Fonte: Nature Preceedings Publicador: Nature Preceedings
Tipo: Conferência ou Objeto de Conferência
Português
BioSharing works at the global level to build stable linkages between journals, funders, implementing data sharing policies, and well-constituted standardization efforts in the biosciences domain, to expedite the communication and the production of an integrated standards-based framework for the capture and sharing of high-throughput genomics and functional genomic bioscience data.

‣ Berberine induces caspase-independent cell death in colon tumor cells through activation of apoptosis-inducing factor

Lihong Wang; Liping Liu; Yan Shi; Hamwei Cao; Rupesh Chaturvedi; Tianhui Hu; Keith Wilson; D. Brent Polk; Fang Yan
Fonte: Nature Preceedings Publicador: Nature Preceedings
Tipo: Manuscript
Português
Berberine, an isoquinoline alkaloid derived from plants, is a traditional medicine for treating bacterial diarrhea and intestinal parasite infections. Although berberine has recently been shown to suppress growth of several tumor cell lines, information regarding the effect of berberine on colon tumor growth is limited. Here, we investigated the mechanisms underlying the effects of berberine on regulating the fate of colon tumor cells, specifically the immorto Min mouse colonic epithelial (IMCE) cells carrying the Apcmin mutation, and of normal colon epithelial cells, namely young adult mouse colon (YAMC) epithelial cells. Berberine decreased colon tumor colony formation in agar, and induced cell death and LDH release in a time- and concentration-dependent manner in IMCE cells. In contrast, YAMC cells were not sensitive to berberine-induced cell death. Berberine did not stimulate caspase activation, and PARP cleavage and berberine-induced cell death were not affected by a caspase inhibitor in IMCE cells. Rather, berberine stimulated a caspase-independent cell death mediator, apoptosis-inducing factor (AIF) release from mitochondria and nuclear translocation in a ROS production-dependent manner. Amelioration of berberine-stimulated ROS production or suppression of AIF expression blocked berberine-induced cell death and LDH release in IMCE cells. Furthermore...

‣ Formal Systems Architectures for Biology

Bradly Alicea
Fonte: Nature Preceedings Publicador: Nature Preceedings
Tipo: Conferência ou Objeto de Conferência
Português
When the word "systems" is used in systems biology, it invokes a variety of assumptions about what defines the subject under investigation, which in turn can lead to divergent research outcomes. We will take the position that systems are defined by their potential organizing and "control" mechanisms, which distinguishes complex, living systems from a primordial soup. This will be accomplished by defining and investigating three interesting control motifs in biological systems: dominoes and clocks, futile cycles, and complex feedforward regulation. Additional mechanisms that combine feedback and feedforward mechanisms will also be briefly elaborated upon. Throughout these examples, our focus will be on the connection between top-down control mechanisms and bottom-up self-organizing mechanisms.

‣ SBGN-ED – working with the Systems Biology Graphical Notation

Tobias Czauderna; Falk Schreiber
Fonte: Nature Preceedings Publicador: Nature Preceedings
Tipo: Conferência ou Objeto de Conferência
Português
The Systems Biology Graphical Notation - SBGN [1] provides a standard for the visual representation of biochemical and cellular processes. SBGN aims to improve information exchange and to support the collaborative creation of large maps based on individual modules. The language contains three views of biological processes covering different levels of detail: (1) Process Description (PD): this sublanguage provides a detailed presentation of the temporal dependencies of biological interactions in a network; (2) Entity Relationship (ER): this sublanguage displays the relationships in which a given entity can participate in a network; and (3) Activity Flow (AF): this sublanguage shows the flow of information between biological entities in an abstract way. SBGN aims to support a more efficient and accurate communication of biological knowledge between different research communities. However, to increase its usage, tools for editing, validating, layouting and translating SBGN maps are desirable. We present novel developments in SBGN-ED [2], a tool which allows the creation of all three types of SBGN maps from scratch or the editing of existing maps...

‣ Positive Darwinian Selection And The Birth Of An Olfactory Receptor Clade In Teleost Fish

Ashiq Hussain; Luis Saraiva; Sigrun Korsching
Fonte: Nature Preceedings Publicador: Nature Preceedings
Tipo: Poster
Português
Trace amine-associated receptors (TAARs) in mammals recently have been shown to function as olfactory receptors. We have delineated the taar gene family in jawless, cartilaginous and bony fish (zero, two, and more than hundred genes, respectively). We conclude that taar genes are evolutionary much younger than the related OR and ORA/V1R olfactory receptor families, which are present already in lamprey, a jawless vertebrate. The two cartilaginous fish genes appear to be ancestral for two taar classes, each with mammalian and bony fish (teleost) representatives. Unexpectedly, a whole new clade, class III, of taar genes originated even later, within the teleost lineage. Taar genes from all three classes are expressed in subsets of zebrafish olfactory receptor neurons, supporting their function as olfactory receptors. Expression of most TAAR genes in 5dpf zebrafish is found restricted to olfactory epithelium (OE). The highly conserved TAAR1 (shark, mammalian and teleost orthologs) is not expressed in the olfactory epithelium and may constitute the sole remnant of a primordial, non-olfactory function of this family. Class III comprises three-fourths of all teleost taar genes, and is characterized by the complete loss of the aminergic ligand-binding motif...

‣ Singlet-triplet excitation energies of substituted benzenes: A G4 theoretical study

Sierra Rayne; Kaya Forest
Fonte: Nature Preceedings Publicador: Nature Preceedings
Tipo: Manuscript
Português
Singlet-triplet adiabatic (AE~S-T~) and well-to-well (WWE~S-T~) excitation energies of variously substituted phenyl cations were calculated at the G4 level of theory. The G4 E~S-T~ estimates range from 19 to 40 kJ/mol higher than prior density functional theory based predictions for these cations, and suggest that E~S-T~ and ground state multiplicity structure-property trends for phenyl cations previously proposed in the literature may be incorrect. Among the substituents considered, meta-substituted phenyl cations with electron donating groups have singlet ground states, and are not isoenergetic with the corresponding triplet states as previously claimed. Depending on the functional group, ortho- or para- substituted phenyl cations may also be ground state singlets despite the presence of an electron donating moiety.

‣ A G4MP2 theoretical study on the gas phase enthalpies of formation for various polycyclic aromatic hydrocarbons (PAHs) and other C~10~ through C~20~ unsaturated hydrocarbons

Sierra Rayne; Kaya Forest
Fonte: Nature Preceedings Publicador: Nature Preceedings
Tipo: Manuscript
Português
Gas phase enthalpies of formation at 298.15 and 1 atm (Δ~f~H~(g),298K~) were calculated using the atomization approach at the G4MP2 composite method level of theory for 86 polyaromatic hydrocarbons (PAHs) and other C~10~ through C~20~ unsaturated hydrocarbons. Where available, good agreement with prior experimental data and/or high level theoretical estimates was obtained. Linear regressions between semiempirical MNDO, MNDO-d, AM1, PM3, RM1, and PM6 estimated Δ~f~H~(g),298K~ and the corresponding G4MP2 values were employed to obtain G4MP2 corrected semiempirical Δ~f~H~(g),298K~ for a suite of 156 C~11~ through C~42~ unsaturated hydrocarbons and PAHs.