1,488 research outputs found
Training Support Vector Machines Using Frank-Wolfe Optimization Methods
Training a Support Vector Machine (SVM) requires the solution of a quadratic
programming problem (QP) whose computational complexity becomes prohibitively
expensive for large scale datasets. Traditional optimization methods cannot be
directly applied in these cases, mainly due to memory restrictions.
By adopting a slightly different objective function and under mild conditions
on the kernel used within the model, efficient algorithms to train SVMs have
been devised under the name of Core Vector Machines (CVMs). This framework
exploits the equivalence of the resulting learning problem with the task of
building a Minimal Enclosing Ball (MEB) problem in a feature space, where data
is implicitly embedded by a kernel function.
In this paper, we improve on the CVM approach by proposing two novel methods
to build SVMs based on the Frank-Wolfe algorithm, recently revisited as a fast
method to approximate the solution of a MEB problem. In contrast to CVMs, our
algorithms do not require to compute the solutions of a sequence of
increasingly complex QPs and are defined by using only analytic optimization
steps. Experiments on a large collection of datasets show that our methods
scale better than CVMs in most cases, sometimes at the price of a slightly
lower accuracy. As CVMs, the proposed methods can be easily extended to machine
learning problems other than binary classification. However, effective
classifiers are also obtained using kernels which do not satisfy the condition
required by CVMs and can thus be used for a wider set of problems
Continental degassing of helium in an active tectonic setting (northern Italy): the role of seismicity
In order to investigate the variability of helium degassing in continental regions, its release from rocks and emission into the atmosphere, here we studied the degassing of volatiles in a seismically active region of northern Italy (MwMAX = 6) at the Nirano-Regnano mud volcanic system. The emitted gases in the study area are CH4–dominated and it is the carrier for helium (He) transfer through the crust. Carbon and He isotopes unequivocally indicate that crustal-derived fluids dominate these systems. An high-resolution 3-dimensional reconstruction of the gas reservoirs feeding the observed gas emissions at the surface permits to estimate the amount of He stored in the natural reservoirs. Our study demonstrated that the in-situ production of 4He in the crust and a long-lasting diffusion through the crust are not the main processes that rule the He degassing in the region. Furthermore, we demonstrated that micro-fracturation due to the field of stress that generates the local seismicity increases the release of He from the rocks and can sustain the excess of He in the natural reservoirs respect to the steady-state diffusive degassing. These results prove that (1) the transport of volatiles through the crust can be episodic as function of rock deformation and seismicity and (2) He can be used to highlight changes in the stress field and related earthquakes
Using high-resolution stratigraphy and structural analysis to constrain a “polyphase” tectonics in wedge-top basins. Inferences from the Late Tortonian Scillato Basin (central-northern Sicily).
The present paper aims to show, both from a stratigraphic and structural points of view, the main features of
a wedge-top syntectonic basin which evolved recording polyphase and non-coaxial tectonics. The study area
is the Scillato Basin (SB), a roughly N–S-oriented structural depression located in the central-northern sector
of the Sicililian Maghrebides. There, an approximately 1300 m-thick upper Serravallian to upper Tortonian
succession of clastic units outcrops as a portion of the Neogene syntectonic covers of the Sicilian fold and
thrust belt. Within the outcropping succession the upper Tortonian Terravecchia Fm represents the main
topic of this paper. A multidisciplinary approach was carried out through an integration of sedimentology, facies,
stratal pattern and structural analyses; this was applied to the formation enabling one to recognize in
the Scillato Basin afining to coarsening upward succession, deposited recording an early transgressive and
a late regressive depositional stage. In our model these two main depositional stages developed and are directly
relatable to a two-step structural evolution of the basin. During thefirst step, a NW–SE-oriented structural
depression existed, enclosed between structural highs and accommodating the lower and middle
portion of the upper Tortonian succession. Subsequently, during the second step, the NW–SE depression
was non-coaxially deformed by superimposition of high-angle transpressive faults (many of which were
SE-dipping), developed in response to the upward propagation of structures enucleated at deeper structural
levels. This step was recorded in the basin by development of both depositional and structural interferences
recognizable along the upper portion of the Scillato Basin succession. A comparison betweenfield data and
deep geophysical data interpreted at the preliminary stage, raises questions about the late Miocene geological
evolution of this sector of the Sicilian chain, including: (i) the syn-tectonic deposition of the Terravecchia
Fm. in the Scillato Basin clearly recorded the interference of two main and non-coaxial tectonic events;
(ii) the younger of these two events has a clear tranpressional character and was active during the very
late Tortonian; (iii) as also indicated by many authors in neighboring orogenic wedges, the main control
on the location, geometry and depositional evolution of the Scillato wedge-top Basin was carried out by compressional
and transpressional structures developed at a deeper structural level. Their deformation propagated
upward both into the shallow structural level and sedimentary covers; therefore (iv) the late Miocene
structural scenario here depicted is not consistent either with the back-arc-related extension or with the
late orogenic gravitational collapse models previously invoked by other authors with regard to this sector
of the Sicilian thrust belt
An outdoor activity to learn operations with integers
This article describes an example of research-informed teaching to help students to understand the operations with integers. The approach used is that of Inquiry and Embodied cognition in outdoor context, with the help of sagittal axis. The activity involved 15, eight grades (aged 13/14), students from a middle school in Trieste, Italy. The results were tested by proposing to the same students’ different types of exercises and problems. 73% have obtained positive results with 72% of which very good. Finally, we investigated through Mentimeter the students’ appreciation of the outdoor activity. 100% of students found the activity fun and helpful
Partially Updated Switching-Method for systems of nonlinear equations
AbstractA hybrid method for solving systems of n nonlinear equations is given. The method does not use derivative information and is especially attractive when good starting points are not available and the given system is expensive to evaluate. It is shown that, after a few steps, each iteration requires (2k + 1) function evaluations where k, 1 ⩽ k ⩽ n, is chosen so as to have an efficient algorithm. Global convergence results are given and superlinear convergence is established. Some numerical results show the numerical performance of the proposed method
A Jurassic-Cretaceous intraplatform basin in the Panormide Southern Tethyan margin (NW Sicily, Italy), reaveled by integrating facies and structural analyses with subsidence history
We illustrate the tectono-sedimentary evolution of a Jurassic-Cretaceous intraplatform basin in a fold and thrust belt present setting (Cala Rossa basin).
Detailed stratigraphy and facies analysis of Upper Triassic-Eocene successions outcropping in the Palermo Mts (NW Sicily), integrated with structural analysis, restoration and basin analysis, led to recognize and describe into the intraplatform basin the proximal and distal depositional areas respect to the bordered carbonate platform sectors.
Carbonate platform was characterized by a rimmed reef growing with progradational trends towards the basin, as suggested by the several reworked shallow-water materials interlayered into the deep-water succession. More, the occurrence of thick resedimented breccia levels into the deep-water succession suggests the time and the characters of synsedimentary tectonics occurred during the Late Jurassic.
The study sections, involved in the building processes of the Sicilian fold and thrust belt, were restored in order to obtain the original width of the Cala Rossa basin, useful to reconstruct the original geometries and opening mechanisms of the basin. Basin analysis allowed reconstructing the subsidence history of three sectors with different paleobathymetry, evidencing the role exerted by tectonics in the evolution of the narrow Cala Rossa basin.
In our interpretation, a transtensional dextral Lower Jurassic fault system, WNW-ESE (present-day) oriented, has activated a wedge shaped pull-apart basin. In the frame of the geodynamic evolution of the Southern Tethyan rifted continental margin, the Cala Rossa basin could have been affected by Jurassic transtensional faults related to the lateral westward motion of Africa relative to Europe
Seismically-induced soft-sediment deformation structures in Upper Triassic deepwater carbonates (Central Sicily)
We describe soft-sediment deformation structures into the Upper Triassic cherty limestone outcropping in the Pizzo
Lupo section (Central Sicily, Italy), pertaining to the deep-water palaeodomain of the Southern Tethyan margin.
In the study section, mainly consisting of thin-bedded mudstone/marl alternations with bedded chert intercalations,
some lithofacies have been separated on the basis of the abundance of the calcium carbonate/clay content and the overall
textural features.
The deformational structures, displaying different deformational styles as folded and faulted beds, disturbed layers,
clastic dikes, and slumps occur mainly in the deformed horizons that involve marl-dominated lithofacies. Small-scale
water-escape structures involve beds with nodular fabric. Synsedimentary faults affect the mud-limestone dominated
lithofacies, which are characterized by fault-rotating blocks producing lateral thinning. These bodies appear to have
moved coherently along an overall planar surface.
We relate these soft-sediment deformations to slump sheets, associated with down-slope sliding of sedimentary
masses. The deformation mechanism and driving force for these soft-sediment deformations are due essentially to
gravitational instability and dewatering.
Detailing, rotational (slump) and translational (glide) slides and water-escape are the main processes causing the
distinguished deformational styles.
The synsedimentary extensional tectonics that affected the Upper Triassic pelagic deposits was the triggering process
responsible for the instability of the seafloor inducing loss of coherence of the unconsolidated sediments on the sea
bottom, developing a large number of gravity-driven slides.
The analysis of both of these SSDSs and their relationships with the structural scenario allow us to hypothesise that
they are seismically-induced
K022: Effect of combination therapy (ANG II antagonist, valsartan and a calcium channel blocker) in a hypertensive model of diabetic nephropathy
Recently, it has been suggested that in the context of diabetes and hypertension, more aggressive blood pressure targets should be considered. To achieve these levels of blood pressure control, it is likely that combination therapy will need to be used. The present study has explored the role of the addition of either a dihydropyridine or a non-dihydropyridine calcium channel blocker (CCB) to Ang II antagonist based treatment in an experimental model of hypertension and diabetes. The doses chosen for the combination therapy groups were lower than those used with monotherapy in order to achieve similar antihypertensive efficacy. Diabetic (streptozotocin induced) SHR were randomised to no treatment, valsartan (30 mg/kg/day), the non-dihydropyridine CCB verapamil (20 mg/kg/day), the dihydropyridine CCB amlodipine (6 mg/kg/day), a combination of valsartan and amlodipine (20 mg + 4 mg/kg/day respectively) or valsartan and verapamil (20 mg + 15 mg/kg/day respectively). Serial measurements of systolic blood pressure (BP) and albumin excretion rate (AER) were performed monthly (data are shown at week 16 for AER and mean of wk 20-28 for BP). This model was associated with hypertension (control, 217 ± 8, diabetic, 200 ± 5 mmHg) which was reduced by most treatments to a similar degree (valsartan 165 ± 3, amlodipine 164 ± 2, verapamil 182 ± 4, valsartan + amlodipine 151 ± 3 and valsartan + verapamil 169 ± 5 mmHg). Diabetes was associated with a progressive increase in AER (control 1.5 vs diabetic 17 mg/24 hr). Valsartan retarded the increase in AER (11 mg/24 hr). Similar efficacy was observed in the valsartan + amlodipine combination (9 mg/24 hr) but not with amlodipine alone (16 mg/24 hr) despite similar effects on blood pressure. No advantage of verapamil versus amlodipine either as monotherapy or in combination with valsartan was observed. The present study indicates that the combination of an Ang II antagonist and a dihydropyridine CCB is an effective regimen at reducing blood pressure and albuminuria in the context of diabetes and hypertensio
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