Crida manada fer per la... ciutat de Valencia, de la concessio, y capitols, en que sa Magestat li ha fet gracia, y mercè, del Port de Transit...

Crida publicada el 22 de noviembre de 1679

Recovery of Disruptions in Rapid Transit Networks

This paper studies the disruption management problem of rapid transit rail networks. Besides optimizing the timetable and the rolling stock schedules, we explicitly deal with the effects of the disruption on the passenger demand. We propose a two-step approach that combines an integrated optimization model (for the timetable and rolling stock) with a model for the passengers’ behavior. We report our computational tests on realistic problem instances of the Spanish rail operator RENFE. The proposed approach is able to find solutions with a very good balance between various managerial goals within a few minutes. Se estudia la gestión de las incidencias en redes de metro y cercanías. Se optimizan los horarios y la asignación del material rodante, teniendo en cuenta el comportamiento de los pasajeros. Se reallizan pruebas en varias líneas de la red de cercanías de Madrid, con resultados satisfactorios.

A model for setting services on auxiliary bus lines under congestion

In this paper, a mathematical programming model and a heuristically derived solution is described to assist with the efficient planning of services for a set of auxiliary bus lines (a bus-bridging system) during disruptions of metro and rapid transit lines. The model can be considered static and takes into account the average flows of passengers over a given period of time (i.e., the peak morning traffic hour) Auxiliary bus services must accommodate very high demand levels, and the model presented is able to take into account the operation of a bus-bridging system under congested conditions. A general analysis of the congestion in public transportation lines is presented, and the results are applied to the design of a bus-bridging system. A nonlinear integer mathematical programming model and a suitable approximation of this model are then formulated. This approximated model can be solved by a heuristic procedure that has been shown to be computationally viable. The output of the model is as follows: (a) the number of bus units to assign to each of the candidate lines of the bus-bridging system; (b) the routes to be followed by users passengers of each of the origin–destination pairs; (c) the operational conditions of the components of the bus-bridging system, including the passenger load of each of the line segments, the degree of saturation of the bus stops relative to their bus input flows, the bus service times at bus stops and the passenger waiting times at bus stops. The model is able to take into account bounds with regard to the maximum number of passengers waiting at bus stops and the space available at bus stops for the queueing of bus units. This paper demonstrates the applicability of the model with two realistic test cases: a railway corridor in Madrid and a metro line in Barcelona Planificación de los servicios de lineas auxiliares de autobuses durante las incidencias de las redes de metro y cercanías. El modelo estudia el problema bajo condiciones de alta demanda y condiciones de congestión. El modelo no lineal resultante es resuelto mediante heurísticas que demuestran su utilidad. Se demuestran los resultados en dos corredores de las ciudades de Barcelona y Madrid.

The relationship between young people's transit use and their perceptions of equity concepts in transit service provision

This study investigates the effect of price and travel mode fairness and spatial equity in transit provision on the perceived transit service quality, willingness to pay, and habitual frequency of use. Based on the theory of planned behavior, we developed a web-based questionnaire for revealed preferences data collection. The survey was administered among young people in Copenhagen and Lisbon to explore the transit perceptions and use under different economic and transit provision conditions. The survey yielded 499 questionnaires, analyzed by means of structural equation models. Results show that higher perceived fairness relates positively to higher perceived quality of transit service and higher perceived ease of paying for transit use. Higher perceived spatial equity in service provision is associated with higher perceived service quality. Higher perceived service quality relates to higher perceived ease of payment, which links to higher frequency of transit use.

Transit Use by Young People in Times of Financial Austerity: A Cause of Equity Concern?

This study investigates the effect of price and travel time fairness and spatial equity in transit provision on the perceived transit service quality, willingness to pay, and habitual frequency of use. Based on the theory of planned behavior, we developed a web-based questionnaire for revealed preferences data collection. The survey was administered among young people in Copenhagen and Lisbon to explore the transit perceptions and use under different economic and transit provision conditions. The survey yielded 499 questionnaires, analyzed by means of structural equation models. Results show that higher perceived fairness relates positively to higher perceived quality of transit service and higher perceived ease of paying for transit use. Higher perceived spatial equity in service provision is associated with higher perceived service quality. Higher perceived service quality relates to higher perceived ease of payment, which links to higher frequency of transit use.

Regulation of chloroplast protein import through a protochlorophyllide-responsive transit peptide

NADPH:protochlorophyllide (Pchlide) oxidoreductase (POR) is the key enzyme of chlorophyll biosynthesis in angiosperms. In barley, two POR enzymes, termed PORA and PORB, exist. Both are nucleus-encoded plastid proteins that must be imported posttranslationally from the cytosol. Whereas the import of the precursor of PORA, pPORA, previously has been shown to depend on Pchlide, the import of pPORB occurred constitutively. To study this striking difference, chimeric precursor proteins were constructed in which the transit sequences of the pPORA and pPORB were exchanged and fused to either their cognate polypeptides or to a cytosolic dihydrofolate reductase (DHFR) reporter protein of mouse. As shown here, the transit peptide of the pPORA (transA) conferred the Pchlide requirement of import onto both the mature PORB and the DHFR. By contrast, the transit peptide of the pPORB directed the reporter protein into both chloroplasts that contained or lacked translocation-active Pchlide. In vitro binding studies further demonstrated that the transit peptide of the pPORA, but not of the pPORB, is able to bind Pchlide. We conclude that the import of the authentic pPORA and that of the transA-PORB and transA-DHFR fusion proteins is regulated by a direct transit peptide-Pchlide interaction, which is likely to occur in the plastid envelope, a major site of porphyrin biosynthesis.

Characterization of the Golgi Complex Cleared of Proteins in Transit and Examination of Calcium Uptake Activities

To characterize endogenous molecules and activities of the Golgi complex, proteins in transit were >99% cleared from rat hepatocytes by using cycloheximide (CHX) treatment. The loss of proteins in transit resulted in condensation of the Golgi cisternae and stacks. Isolation of a stacked Golgi fraction is equally efficient with or without proteins in transit [control (CTL SGF1) and cycloheximide (CHX SGF1)]. Electron microscopy and morphometric analysis showed that >90% of the elements could be positively identified as Golgi stacks or cisternae. Biochemical analysis showed that the cis-, medial-, trans-, and TGN Golgi markers were enriched over the postnuclear supernatant 200- to 400-fold with and 400- to 700-fold without proteins in transit. To provide information on a mechanism for import of calcium required at the later stages of the secretory pathway, calcium uptake into CTL SGF1 and CHX SGF1 was examined. All calcium uptake into CTL SGF1 was dependent on a thapsigargin-resistant pump not resident to the Golgi complex and a thapsigargin-sensitive pump resident to the Golgi. Experiments using CHX SGF1 showed that the thapsigargin-resistant activity was a plasma membrane calcium ATPase isoform in transit to the plasma membrane and the thapsigargin-sensitive pump was a sarcoplasmic/endoplasmic reticulum calcium ATPase isoform. In vivo both of these calcium ATPases function to maintain millimolar levels of calcium within the Golgi lumen.

Domains of a Transit Sequence Required for in Vivo Import in Arabidopsis Chloroplasts1

Nuclear-encoded precursors of chloroplast proteins are synthesized with an amino-terminal cleavable transit sequence, which contains the information for chloroplastic targeting. To determine which regions of the transit sequence are most important for its function, the chloroplast uptake and processing of a full-length ferredoxin precursor and four mutants with deletions in adjacent regions of the transit sequence were analyzed. Arabidopsis was used as an experimental system for both in vitro and in vivo import. The full-length wild-type precursor translocated efficiently into isolated Arabidopsis chloroplasts, and upon expression in transgenic Arabidopsis plants only mature-sized protein was detected, which was localized inside the chloroplast. None of the deletion mutants was imported in vitro. By analyzing transgenic plants, more subtle effects on import were observed. The most N-terminal deletion resulted in a fully defective transit sequence. Two deletions in the middle region of the transit sequence allowed translocation into the chloroplast, although with reduced efficiencies. One deletion in this region strongly reduced mature protein accumulation in older plants. The most C-terminal deletion was translocated but resulted in defective processing. These results allow the dissection of the transit sequence into separate functional regions and give an in vivo basis for a domain-like structure of the ferredoxin transit sequence.

Transit Peptide Mutations That Impair in Vitro and in Vivo Chloroplast Protein Import Do Not Affect Accumulation of the γ-Subunit of Chloroplast ATPase1

We have begun to take a genetic approach to study chloroplast protein import in Chlamydomonas reinhardtii by creating deletions in the transit peptide of the γ-subunit of chloroplast ATPase-coupling factor 1 (CF1-γ, encoded by AtpC) and testing their effects in vivo by transforming the altered genes into an atpC mutant, and in vitro by importing mutant precursors into isolated C. reinhardtii chloroplasts. Deletions that removed 20 or 23 amino acid residues from the center of the transit peptide reduced in vitro import to an undetectable level but did not affect CF1-γ accumulation in vivo. The CF1-γ transit peptide does have an in vivo stroma-targeting function, since chimeric genes in which the stroma-targeting domain of the plastocyanin transit peptide was replaced by the AtpC transit peptide-coding region allowed plastocyanin to accumulate in vivo. To determine whether the transit peptide deletions were impaired in in vivo stroma targeting, mutant and wild-type AtpC transit peptide-coding regions were fused to the bacterial ble gene, which confers bleomycin resistance. Although 25% of the wild-type fusion protein was associated with chloroplasts, proteins with transit peptide deletions remained almost entirely cytosolic. These results suggest that even severely impaired in vivo chloroplast protein import probably does not limit the accumulation of CF1-γ.

Nucleus-associated pools of Rna1p, the Saccharomyces cerevisiae Ran/TC4 GTPse activating protein involved in nucleus/cytosol transit.

Rna1p is the GTPase activating enzyme for Ran/TC4, a Ras-like GTPase necessary for nuclear/cytosolic exchange. Although most wild-type Rna1p is located in the cytosol, we found that the vast majority of the mutant Rna1-1p and, under appropriate physiological conditions, a small portion of the wild-type Rna1p cofractionate with yeast nuclei. Subnuclear fractionation studies show that most of the Rna1p is tightly associated with nuclear components, and that a portion of the active protein can be solubilized by treatments that fail to solubilize inactive Rna1-1p. To learn the precise nuclear locations of the Rna1 proteins, we studied their subcellular distributions in HeLa cells. By indirect immuno-fluorescence we show that wild-type Rna1p has three subcellular locations. The majority of the protein is distributed throughout the cytosol, but a portion of the protein is nucleus-associated, located at both the cytosolic surface and within the nucleoplasm. Mutant Rna1-1p is found at the outer nuclear surface and in the cytosol. We propose that a small pool of the wild-type Rna1p is located in the nuclear interior, supporting the model that the same components of the Ran/TC4 GTPase cycle exist on both sides of the nuclear membrane.

Mobility and Aging in Denver, Colorado: Travel Behavior, Mobility Barriers, and Perceptions of Transit

The number of seniors in the U.S. today is growing rapidly because of longer life expectancies and the aging Baby Boomer generation. This age groups' travel behavior will have substantial impacts on transportation, economics, safety, and the environment. This research used a mixed-methods approach to address issues of mobility and aging in Denver, Colorado. A quantitative approach was used to answer broad questions about travel behavior and the effects of age, gender, work status, disability, residential location and socio-economic status on mobility. Qualitative interviews with seniors in the Denver metro area were conducted to identify barriers to mobility, decision-making processes and travel decisions, and seniors' perceptions of public transit. The results of the quantitative and qualitative analyses show that residential location is an important variable for determining seniors' travel behaviors and transportation options. Perceptions of public transit were positive, but accessibility and information barriers exist that prevent older adult from using transit. The findings of this study will help to provide transportation and service recommendations to policymakers and planners in the Denver area as well as to inform studies of other North American cities with large aging populations.

The Impact of Transit Oriented Development on the Travel Behaviors of Workers in Denver, Colorado

To combat unsustainable transportation systems characterized by reliance on petroleum, polluting emissions, traffic congestion and suburban sprawl, planners encourage mixed use, densely populated areas that provide individuals with opportunities to live, work, eat and shop without necessarily having to drive private automobiles to accommodate their needs. Despite these attempts, the frequency and duration of automobile trips has consistently increased in the United States throughout past decades. While many studies have focused on how residential proximity to transit influences travel behavior, the effect of workplace location has largely been ignored. This paper asks, does working near a TOD influence the travel behaviors of workers differently than workers living near a TOD? We examine the non-work travel behaviors of workers based upon their commuting mode and proximity to TODs. The data came from a 2009 travel behavior survey by the Denver Regional Council of Governments, which contains 8,000 households, 16,000 individuals, and nearly 80,000 trips. We measure sustainable travel behaviors as reduced mileage, reduced number of trips, and increased use of non-automobile transportation. The results of this study indicate that closer proximity of both households and workplaces to TODs decrease levels of car commuting and that non-car commuting leads to more sustainable personal travel behaviors characterized by more trips made with alternative modes.

Opportunities and Challenges for the Widespread Implementation of Battery Powered Electric Transit Buses

The need for more sustainable public transportation choices drives innovation and provides opportunity for improvement in options. Transit buses provide many advantages for efficient transportation and electric drive vehicles are anticipated to play an increasing role in future transportation systems. A lifecycle cost analysis of battery electric transit buses indicates rate structures and demand charges do not currently have a large impact on lifecycle cost for small fleets of battery electric buses. As fleets grow, policies and rate structures will need to adjust to avoid becoming a barrier to adoption. Battery electric transit buses are now being developed which promise to address the primary issues of high life cycle cost, low reliability, range, and flexibility.

RNA-Seq expression profile of genes related to neurodegenerative disorders affecting the human retina

Human neurodegenerative diseases, such as Parkinson’s disease (PD) and the neuromuscular disorders called dystroglycanopathies (DGPs), cause retinal impairments. We have used RNA-Seq technology to catalog all known genes linked to PD and DGPs expressed in the human retina and quantitate their mRNA levels in terms of FPKM. We have also characterized their expression profiles in the retina by determining their exonic, intronic and exon-intron junction expression levels, as well as the alternative splicing pattern of particular genes. We believe these data could pave the way toward understanding the molecular bases of sight deficiencies associated with neurodegenerative disorders.