19,849 research outputs found
Feasibility Of OneâDedicatedâLane Bus Rapid Transit âLightâRail Systems And Their Expansion To TwoâDedicatedâLane Systems: A Focus On Geometric Configuration And Performance Planning, MTI Report 08-01
This report consists primarily of two parts, the first on feasibility and the next on space minimization. In the section on feasibility, we propose the concept of a Bus Rapid Transit (BRT) or lightârail system that effectively requires only one dedicated but reversible lane throughout the system to support two-way traffic in the median of a busy commute corridor with regular provision of leftâturn lanes. Based on key ideas proposed in that section, the section on space minimization first addresses how to implement a twoâdedicatedâlane BRT or lightârail system with minimum rightâofâway width and then proposes ways to expand a oneâdedicatedâlane system to two dedicated lanes. In a oneâdedicatedâlane system, traffic crossing is accommodated on the otherwise unused or underused median space resulting from provision of the leftâturn lanes. Although not necessary, some leftâturn lanes can be sacrificed for bus stops. Conceptual design options and geometric configuration sketches for the bus stop and crossing space are provided in the section on feasibility, which also discusses system performance in terms of travel speed, headway of operations, distance between two neighboring crossing spaces, and number of crossing spaces. To ensure practicality, we study implementation of such a system on an existing corridor. Such a system is also useful as an intermediate step toward a twoâdedicatedâlane system because of its potential for facilitating transitâoriented development. In typical existing or planned BRT or lightârail systems implemented with two dedicated traffic lanes, a space equivalent to four traffic lanes is dedicated for a bus stop. In the section on space minimization, we propose implementations requiring only three lanes at a bus stop, based on two key ideas proposed for a oneâdedicatedâlane system. That section also discusses ways to expand a oneâdedicatedâlane system to its corresponding twoâdedicatedâlane system
The potential role of genetic markers in talent identification and athlete assessment in elite sport
In elite sporting codes, the identification and promotion of future athletes into specialized talent pathways is heavily reliant upon objective physical, technical, and tactical characteristics, in addition to subjective coach assessments. Despite the availability of a plethora of assessments, the dependence on subjective forms of identification remain commonplace in most sporting codes. More recently, genetic markers, including several single nucleotide polymorphisms (SNPs), have been correlated with enhanced aerobic capacity, strength, and an overall increase in athletic ability. In this review, we discuss the effects of a number of candidate genes on athletic performance, across single-skilled and multifaceted sporting codes, and propose additional markers for the identification of motor skill acquisition and learning. While displaying some inconsistencies, both the ACE and ACTN3 polymorphisms appear to be more prevalent in strength and endurance sporting teams, and have been found to correlate to physical assessments. More recently, a number of polymorphisms reportedly correlating to athlete performance have gained attention, however inconsistent research design and varying sports make it difficult to ascertain the relevance to the wider sporting population. In elucidating the role of genetic markers in athleticism, existing talent identification protocols may significantly improveâand ultimately enableâtargeted resourcing in junior talent pathways
Do Newton's G and Milgrom's a_0 vary with cosmological epoch ?
In the scalar tensor gravitational theories Newton's constant G_N evolves in
the expanding universe. Likewise, it has been speculated that the acceleration
scale a_0 in Milgrom's modified Newtonian dynamics (MOND) is tied to the scale
of the cosmos, and must thus evolve. With the advent of relativistic
implementations of the modified dynamics, one can address the issue of
variability of the two gravitational ''constants'' with some confidence. Using
TeVeS, the Tensor-Vector-Scalar gravitational theory, as an implementation of
MOND, we calculate the dependence of G_N and a_0 on the TeVeS parameters and
the coeval cosmological value of its scalar field, \phi_c. We find that G_N,
when expressed in atomic units, is strictly nonevolving, a result fully
consistent with recent empirical limits on the variation of G_N. By contrast,
we find that a_0 depends on \phi_c and may thus vary with cosmological epoch.
However, for the brand of TeVeS which seems most promising, a_0 variation
occurs on a timescale much longer than Hubble's, and should be imperceptible
back to redshift unity or even beyond it. This is consistent with emergent data
on the rotation curves of disk galaxies at significants redshifts.Comment: 9 pages, RevTe
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Management of Noncatastrophic Internal Carotid Artery Injury in Endoscopic Skull Base Surgery.
Arterial injuries are the most feared complication of endoscopic skull base surgery. During resection of the middle fossa component of a large ventral skull base chondrosarcoma, arterial bleeding was encountered near the right internal carotid artery (ICA). Durable hemostasis could not be achieved with packing and the patient was taken for an emergent angiogram that revealed a pseudoaneurysm of the proximal intradural ICA. Given the presence of good collateral flow through the anterior and posterior communicating arteries, the right ICA was sacrificed by coil embolization. The patient was taken back to the operating room for closure then transferred to the intensive care unit and maintained on vasopressors for five days to ensure adequate perfusion. The right ICA was coil embolized and the patient was taken back to the operating room for closure. The patient recovered without complication. Arterial injuries, although serious, are not always catastrophic. Critical steps are immediate recognition of bleeding, vascular imaging, and vessel sacrifice if necessary
Topological Transitions in Metamaterials
The ideas of mathematical topology play an important role in many aspects of
modern physics - from phase transitions to field theory to nonlinear dynamics
(Nakahara M (2003) in Geometry, Topology and Physics, ed Brewer DF (IOP
Publishing Ltd, Bristol and Philadelphia), Monastryskiy M (1987) in Riemann
Topology and Physics, (Birkhauser Verlag AG)). An important example of this is
the Lifshitz transition (Lifshitz IM (1960) Anomalies of electron
characteristics of a metal in the high-pressure region, Sov Phys JETP 11:
1130-1135), where the transformation of the Fermi surface of a metal from a
closed to an open geometry (due to e.g. external pressure) leads to a dramatic
effect on the electron magneto-transport (Kosevich AM (2004) Topology and
solid-state physics. Low Temp Phys 30: 97-118). Here, we present the optical
equivalent of the Lifshitz transition in strongly anisotropic metamaterials.
When one of the components of the dielectric permittivity tensor of such a
composite changes sign, the corresponding iso-frequency surface transforms from
an ellipsoid to a hyperboloid. Since the photonic density of states can be
related to the volume enclosed by the iso-frequency surface, such a topological
transition in a metamaterial leads to a dramatic change in the photonic density
of states, with a resulting effect on every single physical parameter related
to the metamaterial - from thermodynamic quantities such as its equilibrium
electromagnetic energy to the nonlinear optical response to
quantum-electrodynamic effects such as spontaneous emission. In the present
paper, we demonstrate the modification of spontaneous light emission from
quantum dots placed near the surface of the metamaterial undergoing the
topological Lifshitz transition, and present the theoretical description of the
effect
Muscle protein and glycogen responses to recovery from hypogravity and unloading by tail-cast suspension
Previous studies in this laboratory using the tail-bast hindlimb suspension model have shown that there are specific changes in protein and carbohydrate metabolism in the soleus muscle due to unloading. For example, 6 days of unloading caused a 27% decrease in mass and a 60% increase in glycogen content in the soleus muscle, while the extensor digitorum longus muscle was unaffected. Also, fresh tissue tyrosine and its in vitro release from the muscle are increased in the unloaded soleus, indicating that this condition causes a more negative protein balance. With these results in mind, studies to investigate the effect of hypogravity on protein and carbohydrate metabolism in a number of rat hindlimb muscles were carried out
Malawiâs Maize Marketing System
National food security in Malawi depends on improving the performance of maize markets. Ensuring that grain is consistently available at tolerable prices is crucial for consumersâ food security. At the same time, surplus producing farmers need to receive farm-gate prices consistently above production costs to intensify the use of fertilizer and other productivity enhancing technologies in a sustainable manner. These concerns give rise to the classic food price dilemma for policy makers in Malawi: how to keep prices low enough to ensure low income consumersâ access to food while keeping prices high enough to promote farm production incentives. These tensions cannot be avoided but they can be relieved through reducing food marketing margins, which shrink the wedge between producer and consumer prices. Moreover, Malawi faces major political and economic problems associated with food price instability especially given its dependence on rain fed agriculture in a region prone to drought. These issues show that improving the performance of maize markets is at the core of achieving sustainable food security and poverty reduction in Malawi.food security, Malawi, maize, marketing, food policy, Agricultural and Food Policy, Community/Rural/Urban Development, Food Security and Poverty, International Development, Marketing, q12, q18,
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Aberrant activity in conceptual networks underlies N400 deficits and unusual thoughts in schizophrenia.
BackgroundThe N400 event-related potential (ERP) is triggered by meaningful stimuli that are incongruous, or unmatched, with their semantic context. Functional magnetic resonance imaging (fMRI) studies have identified brain regions activated by semantic incongruity, but their precise links to the N400 ERP are unclear. In schizophrenia (SZ), N400 amplitude reduction is thought to reflect overly broad associations in semantic networks, but the abnormalities in brain networks underlying deficient N400 remain unknown. We utilized joint independent component analysis (JICA) to link temporal patterns in ERPs to neuroanatomical patterns from fMRI and investigate relationships between N400 amplitude and neuroanatomical activation in SZ patients and healthy controls (HC).MethodsSZ patients (nâŻ=âŻ24) and HC participants (nâŻ=âŻ25) performed a picture-word matching task, in which words were either matched (APPLEâapple) by preceding pictures, or were unmatched by semantically related (in-category; IC, APPLEâlemon) or unrelated (out of category; OC, APPLEâcow) pictures, in separate ERP and fMRI sessions. A JICA "data fusion" analysis was conducted to identify the fMRI brain regions specifically associated with the ERP N400 component. SZ and HC loading weights were compared and correlations with clinical symptoms were assessed.ResultsJICA identified an ERP-fMRI "fused" component that captured the N400, with loading weights that were reduced in SZ. The JICA map for the IC condition showed peaks of activation in the cingulate, precuneus, bilateral temporal poles and cerebellum, whereas the JICA map from the OC condition was linked primarily to visual cortical activation and the left temporal pole. Among SZ patients, fMRI activity from the IC condition was inversely correlated with unusual thought content.ConclusionsThe neural networks associated with the N400 ERP response to semantic violations depends on conceptual relatedness. These findings are consistent with a distributed network underlying neural responses to semantic incongruity including unimodal visual areas as well as integrative, transmodal areas. Unusual thoughts in SZ may reflect impaired processing in transmodal hub regions such as the precuneus, leading to overly broad semantic associations
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