26,703 research outputs found
External control and red tape: the mediating effects of client and organizational feedback
Bozeman’s (1993, 2000) external control model of red tape posits that organizations with higher degrees of external control will have higher levels of red tape. According to the model, this is compounded by entropy affecting the communication of rules and their results, limited discretion over rules and procedures, and non-ownership of rules. However, the model predicts that red tape will be mediated by communication from clients and within the organization. Bozeman’s model is often cited in the literature, but it has not been subjected to empirical verification. This study tests the model using data from a multiple informant survey of 136 upper tier English local governments conducted in 2004 and several secondary sources. Statistical results show that external control does indeed lead to higher levels of red tape. We then test a number of organizational feedback mediators and find that client feedback does little to mediate the effects of red tape; the major factor is trust between politicians and officers. We discuss these findings and propose some changes to the model.postprin
Sea-level responses to rapid sediment erosion and deposition in Taiwan
Numerous studies have shown that sediment deposition can perturb sea level by several meters over millennial timescales by modifying the gravity field, crustal elevation, and sediment thickness. Relatively few studies have focused on the complementary role of erosion on sea-level change despite its effects on the same quantities, partly because many rapidly eroding mountains are too far from shorelines to strongly perturb sea level at the coast. Taiwan, a mountainous island eroding rapidly within tens of km of the coast, offers an opportunity to investigate the joint influences of rapid onshore erosion and rapid offshore deposition on sea-level change. Here we develop a sediment loading history for Taiwan since the previous interglacial (∼120 ka) by compiling published erosion and deposition rate measurements and by applying a geometric marine sediment deposition and compaction model for sites without deposition rate measurements. We use the resulting sediment redistribution history to drive sea-level responses in a gravitationally self-consistent sea-level model. Our simulations show that the effects of rapid onshore erosion outweigh the effects of rapid offshore deposition along Taiwan's east coast. Along the east coast of Taiwan, sediment redistribution induces rapid sea-level fall, a response that differs in sign from the coastal sea-level rise induced by rapid sediment redistribution in many other river systems around the world. The spatial extent of the modeled sea-level fall is sensitive to the Earth model, particularly the effective elastic thickness of the lithosphere, a sensitivity that we describe in further detail in the Discussion. These results suggest that sediment redistribution could have generated sea-level changes of >10m on the east coast of Taiwan since 10 ka and >100m since 120 ka. This can account for some of the discrepancy between observed and modeled paleo-sea-level marker elevations, which reduces estimates of tectonically driven rock uplift rates inferred from the elevation differences between paleo-sea-level markers and modeled sea level. This highlights the importance of accounting for erosional unloading in interpretations of paleo-sea-level reconstructions and associated estimates of tectonically driven uplift rates
Contribution of Matrix Metalloproteinase-9 to Cerebral Edema and Functional Outcome following Experimental Subarachnoid Hemorrhage
Background: Cerebral edema is an important risk factor for death and poor outcome following subarachnoid hemorrhage (SAH). However, underlying mechanisms are still poorly understood. Matrix metalloproteinase (MMP)-9 is held responsible for the degradation of microvascular basal lamina proteins leading to blood-brain barrier dysfunction and, thus, formation of vasogenic cerebral edema. The current study was conducted to clarify the role of MMP-9 for the development of cerebral edema and for functional outcome after SAH. Methods: SAH was induced in FVB/N wild-type (WT) or MMP-9 knockout (MMP-9(-/-)) mice by endovascular puncture. Intracranial pressure (ICP), regional cerebral blood flow (rCBF), and mean arterial blood pressure (MABP) were continuously monitored up to 30 min after SAH. Mortality was quantified for 7 days after SAH. In an additional series neurological function and body weight were assessed for 3 days after SAH. Subsequently, ICP and brain water content were quantified. Results: Acute ICP, rCBF, and MABP did not differ between WT and MMP-9(-/-) mice, while 7 days' mortality was lower in MMP-9(-/-) mice (p = 0.03; 20 vs. 60%). MMP-9(-/-) mice also exhibited better neurological recovery, less brain edema formation, and lower chronic ICP. Conclusions: The results of the current study suggest that MMP-9 contributes to the development of early brain damage after SAH by promoting cerebral edema formation. Hence, MMP-9 may represent a novel molecular target for the treatment of SAH. Copyright (C) 2011 S. Karger AG, Base
Compressibility effects on the scalar mixing in reacting homogeneous turbulence
The compressibility and heat of reaction influence on the scalar mixing in
decaying isotropic turbulence and homogeneous shear flow are examined via data
generated by direct numerical simulations (DNS). The reaction is modeled as
one-step, exothermic, irreversible and Arrhenius type. For the shear flow
simulations, the scalar dissipation rate, as well as the time scale ratio of
mechanical to scalar dissipation, are affected by compressibility and reaction.
This effect is explained by considering the transport equation for the
normalized mixture fraction gradient variance and the relative orientation
between the mixture fraction gradient and the eigenvectors of the solenoidal
strain rate tensor.Comment: In Turbulent Mixing and Combustion, eds. A. Pollard and S. Candel,
Kluwer, 200
Keystroke Inference Using Smartphone Kinematics
The use of smartphones is becoming ubiquitous in modern society, these very personal devices store large amounts of personal information and we use these devices to access everything from our bank to our social networks, we communicate using these devices in both open one-to-many communications and in more closed, private one-to-one communications. In this paper we have created a method to infer what is typed on a device purely from how the device moves in the user’s hand. With very small amounts of training data (less than the size of a tweet) we are able to predict the text typed on a device with accuracies of up to 90%. We found no effect on this accuracy from how fast users type, how comfortable they are using smartphone keyboards or how the device was held in the hand. It is trivial to create an application that can access the motion data of a phone whilst a user is engaged in other applications, the accessing of motion data does not require any permission to be granted by the user and hence represents a tangible threat to smartphone users
Aerothermodynamic Analysis of a Reentry Brazilian Satellite
This work deals with a computational investigation on the small ballistic
reentry Brazilian vehicle SARA (acronyms for SAt\'elite de Reentrada
Atmosf\'erica). Hypersonic flows over the vehicle SARA at zero-degree angle of
attack in a chemical equilibrium and thermal non-equilibrium are modeled by the
Direct Simulation Monte Carlo (DSMC) method, which has become the main
technique for studying complex multidimensional rarefied flows, and that
properly accounts for the non-equilibrium aspects of the flows. The emphasis of
this paper is to examine the behavior of the primary properties during the high
altitude portion of SARA reentry. In this way, velocity, density, pressure and
temperature field are investigated for altitudes of 100, 95, 90, 85 and 80 km.
In addition, comparisons based on geometry are made between axisymmetric and
planar two-dimensional configurations. Some significant differences between
these configurations were noted on the flowfield structure in the reentry
trajectory. The analysis showed that the flow disturbances have different
influence on velocity, density, pressure and temperature along the stagnation
streamline ahead of the capsule nose. It was found that the stagnation region
is a thermally stressed zone. It was also found that the stagnation region is a
zone of strong compression, high wall pressure. Wall pressure distributions are
compared with those of available experimental data and good agreement is found
along the spherical nose for the altitude range investigated.Comment: The paper will be published in Vol. 42 of the Brazilian Journal of
Physic
Diagnostic and Prognostic Utility of Procalcitonin in Patients Presenting to the Emergency Department with Dyspnea
Background Among patients in the emergency department, dyspnea is a common complaint and can pose a diagnostic challenge. Biomarkers are used increasingly to improve diagnostic accuracy and aid with prognostication in dyspneic patients. The purpose of this study was to examine the clinical utility of serum procalcitonin (PCT) for the diagnosis of pneumonia in patients presenting to the emergency department with dyspnea. A secondary objective was to evaluate the prognostic value of PCT for death to 1 year. Methods This study pooled the patient populations of 2 prospective cohorts that previously enrolled patients presenting to 2 urban emergency departments with dyspnea. A total of 453 patients had serum samples available for biomarker analysis. Clinician certainty for the diagnosis of acutely decompensated heart failure was reviewed. Discrimination, calibration, and net reclassification improvement for the diagnosis of pneumonia as well as fatal outcomes were considered. The main outcome was accuracy of PCT for diagnostic categorization of pneumonia. The prognostic value of PCT for survival to 1 year was a secondary outcome. Results Pneumonia alone was diagnosed in 30 patients (6.6%), heart failure without pneumonia in 212 patients (47%), and both diagnoses in 30 patients (6.6%). Procalcitonin concentrations were higher in subjects with pneumonia (0.38 vs 0.06 ng/mL; P < .001). Area under the receiver operating characteristic curve for the diagnosis of pneumonia based on PCT was 0.84 (95% confidence interval [CI], 0.77-0.91; P < .001). Across all levels of clinician-based estimates of heart failure, PCT was sensitive and specific; notably, in patients judged with diagnostic uncertainty (n = 70), a PCT value of 0.10 ng/mL had the optimal balance of sensitivity and specificity (80% and 77%, respectively) for pneumonia. Adding PCT results to variables predictive of pneumonia resulted in a net reclassification improvement of 0.54 (95% CI, 0.24-0.83; P < .001) for both up- and down-reclassifying events. In adjusted analyses, elevated PCT was a predictor of 1-year mortality (hazard ratio 1.8; 95% CI, 1.4-2.3; P < .001) and was additive when elevated in conjunction with natriuretic peptides for this application. Conclusion In emergency department patients with acute dyspnea, PCT is an accurate diagnostic marker for pneumonia and adds independent prognostic information for 1-year mortality
ForestHash: Semantic Hashing With Shallow Random Forests and Tiny Convolutional Networks
Hash codes are efficient data representations for coping with the ever
growing amounts of data. In this paper, we introduce a random forest semantic
hashing scheme that embeds tiny convolutional neural networks (CNN) into
shallow random forests, with near-optimal information-theoretic code
aggregation among trees. We start with a simple hashing scheme, where random
trees in a forest act as hashing functions by setting `1' for the visited tree
leaf, and `0' for the rest. We show that traditional random forests fail to
generate hashes that preserve the underlying similarity between the trees,
rendering the random forests approach to hashing challenging. To address this,
we propose to first randomly group arriving classes at each tree split node
into two groups, obtaining a significantly simplified two-class classification
problem, which can be handled using a light-weight CNN weak learner. Such
random class grouping scheme enables code uniqueness by enforcing each class to
share its code with different classes in different trees. A non-conventional
low-rank loss is further adopted for the CNN weak learners to encourage code
consistency by minimizing intra-class variations and maximizing inter-class
distance for the two random class groups. Finally, we introduce an
information-theoretic approach for aggregating codes of individual trees into a
single hash code, producing a near-optimal unique hash for each class. The
proposed approach significantly outperforms state-of-the-art hashing methods
for image retrieval tasks on large-scale public datasets, while performing at
the level of other state-of-the-art image classification techniques while
utilizing a more compact and efficient scalable representation. This work
proposes a principled and robust procedure to train and deploy in parallel an
ensemble of light-weight CNNs, instead of simply going deeper.Comment: Accepted to ECCV 201
On CPT Symmetry: Cosmological, Quantum-Gravitational and other possible violations and their phenomenology
I discuss various ways in which CPT symmetry may be violated, and their
phenomenology in current or immediate future experimental facilities, both
terrestrial and astrophysical. Specifically, I discuss first violations of CPT
symmetry due to the impossibility of defining a scattering matrix as a
consequence of the existence of microscopic or macroscopic space-time
boundaries, such as Planck-scale Black-Hole (event) horizons, or cosmological
horizons due to the presence of a (positive) cosmological constant in the
Universe. Second, I discuss CPT violation due to breaking of Lorentz symmetry,
which may characterize certain approaches to quantum gravity, and third, I
describe models of CPT non invariance due to violations of locality of
interactions. In each of the above categories I discuss experimental
sensitivities. I argue that the majority of Lorentz-violating cases of CPT
breaking, with minimal (linear) suppression by the Planck-mass scale, are
already excluded by current experimental tests. There are however some
(stringy) models which can evade these constraints.Comment: 27 pages latex, Conference talk Beyond the Desert 200
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