The Fundamental Plane of Spiral Galaxies: Theoretical Expectations

Current theory of disk galaxy formation is used to study fundamental-plane (FP) type of relations for disk galaxies. We examine how the changes in model parameters affect these relations and explore the possibility of using such relations to constrain theoretical models. The distribution of galaxy disks in the space of their fundamental properties are predicted to be concentrated in a plane, with the Tully-Fisher (TF) relation (a relation between luminosity $L$ and maximum rotation velocity $V_m$) being an almost edge-on view. Using rotation velocities at larger radii generally leads to larger TF scatter. In searching for a third parameter, we find that both the disk scale-length $R_d$ (or surface brightness) and the rotation-curve shape are correlated with the TF scatter. The FP relation in the (\Log L, \Log V_m, \Log R_d)-space obtained from the theory is $L\propto R_d^{\alpha'} V_m^{\beta'}$, with ${\alpha'}\sim 0.50$ and ${\beta'}\sim 2.60$, consistent with the preliminary result we obtain from observational data. Among the model parameters we probe, variation in any of them can generate significant scatter in the TF relation, but the effects of the spin parameter and halo concentration can be reduced significantly by introducing $R_d$ while the scatter caused by varying $m_d$ (the ratio between disk mass and halo mass) is most effectively reduced by introducing the parameters which describes the rotation-curve shape. The TF and FP relations combined should therefore provide useful constraints on models of galaxy formation.Comment: 25 pages, 11 figures, 4 tables; submitted to MNRA

INFLUENCES ANALYSIS OF CONFIGURATIONS ON THE PERFORMANCE OF PARALLEL TYPE SIX-AXIS ACCELEROMETERS

The development of parallel type six-axis accelerometers was hindered for their complicated forward kinematics and dynamics algorithms which make it difficult to decouple the six acceleration components timely, accurately and stably. This paper applies four parallel configurations with 6-DOF and a closed-form solution of the forward kinematics to six-axis accelerometers as the elastic bodies, where the piezoelectric ceramics act as the sensitive elements and play the role of prismatic pairs. An efficient decoupling algorithm was derived to calculate the six acceleration components completely by the use of Kane’s dynamics method in configuration space. Considering the differences in sensing properties of the four six-axis accelerometers, a quantitative comparison was conducted to reveal the configurations’ direct influences on some static characteristics, including accuracy, efficiency, sensitivity, isotropy, and working frequency range, which makes a theoretical foundation for the subsequent design of a reconfigurable prototype

INFLUENCES ANALYSIS OF CONFIGURATIONS ON THE PERFORMANCE OF PARALLEL TYPE SIX-AXIS ACCELEROMETERS

The development of parallel type six-axis accelerometers was hindered for their complicated forward kinematics and dynamics algorithms which make it difficult to decouple the six acceleration components timely, accurately and stably. This paper applies four parallel configurations with 6-DOF and a closed-form solution of the forward kinematics to six-axis accelerometers as the elastic bodies, where the piezoelectric ceramics act as the sensitive elements and play the role of prismatic pairs. An efficient decoupling algorithm was derived to calculate the six acceleration components completely by the use of Kane’s dynamics method in configuration space. Considering the differences in sensing properties of the four six-axis accelerometers, a quantitative comparison was conducted to reveal the configurations’ direct influences on some static characteristics, including accuracy, efficiency, sensitivity, isotropy, and working frequency range, which makes a theoretical foundation for the subsequent design of a reconfigurable prototype

The morphological dependent Tully-Fisher relation of spiral galaxies

The Tully-Fisher relation of spiral galaxies shows notable dependence on morphological types, with earlier type spirals having systematically lower luminosity at fixed maximum rotation velocity $V_{max}$. This decrement of luminosity is more significant in shorter wavelengths. By modeling the rotation curve and stellar population of different morphological type spiral galaxies in combination, we find the $V_{max}$ of spiral galaxies is weakly dependent on the morphological type, whereas the difference of the stellar population originating from the bulge disk composition effect mainly account for the morphological type dependence of the Tully-Fisher relation.Comment: 8 pages, 3 figures, ApJ accepte

MPprimer: a program for reliable multiplex PCR primer design

<p>Abstract</p> <p>Background</p> <p>Multiplex PCR, defined as the simultaneous amplification of multiple regions of a DNA template or multiple DNA templates using more than one primer set (comprising a forward primer and a reverse primer) in one tube, has been widely used in diagnostic applications of clinical and environmental microbiology studies. However, primer design for multiplex PCR is still a challenging problem and several factors need to be considered. These problems include mis-priming due to nonspecific binding to non-target DNA templates, primer dimerization, and the inability to separate and purify DNA amplicons with similar electrophoretic mobility.</p> <p>Results</p> <p>A program named MPprimer was developed to help users for reliable multiplex PCR primer design. It employs the widely used primer design program Primer3 and the primer specificity evaluation program MFEprimer to design and evaluate the candidate primers based on genomic or transcript DNA database, followed by careful examination to avoid primer dimerization. The graph-expanding algorithm derived from the greedy algorithm was used to determine the optimal primer set combinations (PSCs) for multiplex PCR assay. In addition, MPprimer provides a virtual electrophotogram to help users choose the best PSC. The experimental validation from 2× to 5× plex PCR demonstrates the reliability of MPprimer. As another example, MPprimer is able to design the multiplex PCR primers for DMD (dystrophin gene which caused Duchenne Muscular Dystrophy), which has 79 exons, for 20×, 20×, 20×, 14×, and 5× plex PCR reactions in five tubes to detect underlying exon deletions.</p> <p>Conclusions</p> <p>MPprimer is a valuable tool for designing specific, non-dimerizing primer set combinations with constrained amplicons size for multiplex PCR assays.</p

Transcription and splicing regulation in human umbilical vein endothelial cells under hypoxic stress conditions by exon array

<p>Abstract</p> <p>Background</p> <p>The balance between endothelial cell survival and apoptosis during stress is an important cellular process for vessel integrity and vascular homeostasis, and it is also pivotal in angiogenesis during the development of many vascular diseases. However, the underlying molecular mechanisms remain largely unknown. Although both transcription and alternative splicing are important in regulating gene expression in endothelial cells under stress, the regulatory mechanisms underlying this state and their interactions have not yet been studied on a genome-wide basis.</p> <p>Results</p> <p>Human umbilical vein endothelial cells (HUVECs) were treated with cobalt chloride (CoCl₂) both to mimic hypoxia and to induce cell apoptosis and alternative splicing responses. Cell apoptosis rate analysis indicated that HUVECs exposed to 300 μM CoCl₂for 24 hrs were initially counterbalancing apoptosis with cell survival. We therefore used the Affymetrix exon array system to determine genome-wide transcript- and exon-level differential expression. Other than 1583 differentially expressed transcripts, 342 alternatively spliced exons were detected and classified by different splicing types. Sixteen alternatively spliced exons were validated by RT-PCR. Furthermore, direct evidence for the ongoing balance between HUVEC survival and apoptosis was provided by Gene Ontology (GO) and protein function, as well as protein domain and pathway enrichment analyses of the differentially expressed transcripts. Importantly, a novel molecular module, in which the heat shock protein (HSP) families play a significant role, was found to be activated under mimicked hypoxia conditions. In addition, 46% of the transcripts containing stress-modulated exons were differentially expressed, indicating the possibility of combinatorial regulation of transcription and splicing.</p> <p>Conclusion</p> <p>The exon array system effectively profiles gene expression and splicing on the genome-wide scale. Based on this approach, our data suggest that transcription and splicing not only regulate gene expression, but also carry out combinational regulation of the balance between survival and apoptosis of HUVECs under mimicked hypoxia conditions. Since cell survival following the apoptotic challenge is pivotal in angiogenesis during the development of many vascular diseases, our results may advance the knowledge of multilevel gene regulation in endothelial cells under physiological and pathological conditions.</p

Insights into lignocellulose degradation: comparative genomics of anaerobic and cellulolytic Ruminiclostridium-type species

Mesophilic, anaerobic, and cellulolytic Ruminiclostridium-type bacterial species can secrete an extracellular, multi-enzyme machinery cellulosome, which efficiently degrades cellulose. In this study, we first reported the complete genome of Ruminiclostridium papyrosolvens DSM2782, a single circular 5,027,861-bp chromosome with 37.1% G + C content, and compared it with other Ruminiclostridium-type species. Pan-genome analysis showed that Ruminiclostridium-type species share a large number of core genes to conserve basic functions, although they have a high level of intraspecific genetic diversity. Especially, KEGG mapping revealed that Ruminiclostridium-type species mainly use ABC transporters regulated by two-component systems (TCSs) to absorb extracellular sugars but not phosphotransferase systems (PTSs) that are employed by solventogenic clostridia, such as Clostridium acetobutylicum. Furthermore, we performed comparative analyses of the species-specific repertoire of CAZymes for each of the Ruminiclostridium-type species. The high similarity of their cohesins suggests a common ancestor and potential cross-species recognition. Additionally, both differences between the C-terminal cohesins and other cohesins of scaffoldins and between the dockerins linking with cellulases and other catalytic domains indicate a preference for the location of cellulosomal catalytic subunits at scaffoldins. The information gained in this study may be utilized directly or developed further by genetic engineering and optimizing enzyme systems or cell factories for enhanced biotechnological biomass deconstruction and biofuel production

Objective method for localization of cortical asymmetries using positron emission tomography to aid surgical resection of epileptic foci

We designed a semiautomated method for the objective detection of abnormal regions of tracer accumulation in the brain. The purpose of the present study was to examine the diagnostic performance of this method by applying it to patients with clinically intractable epilepsy of unilateral origin; they underwent [F-18] deoxyglucose positron emission tomography (PET) prior to surgical resection of epileptic foci. A semiautomated method for assessment of asymmetries in the brain cortex was developed that compares activity concentrations in homotopic cortical areas. When these differences exceeded a predefined threshold, the areas with lower activity were marked and 3-dimensional surface rendered images were created to guide placement of intracranial electrodes (ECoG) followed by surgical resection. The normal amount of asymmetry between small (0.5–0.7 cm 2 ) homotopic cortical regions was determined as 5.9 ± 4.0% (mean ± SD). The false-positive fraction was determined for cutoff thresholds of 1 SD (10%), 1.5 SD (12%), and 2 SD (15%) outside the mean and was found to be 89, 44, and 0%, respectively. The obtained sensitivity-specificity pairs for correct localization of epileptogenic lobes based on the ECoG results were best for the 15% threshold (80/94%, accuracy 0.90). This objective PET method allows the accurate determination of cortical asymmetries, and it proved to be highly efficient in guiding epilepsy surgery. Comp Aid Surg 74–82 (1998). © 1998 Wiley-Liss, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/35224/1/4_ftp.pd