193 research outputs found
Structural investigation and strain analysis of a polyphase flower structure in the Lower Saxony Basin, Germany
The Lower Saxony Basin (LSB) is a part
of the post-Variscan Central European
Basin System. We used a 3-D reflection
seismic dataset in the northern LSB,
provided by RWE-DEA AG, Hamburg
(c.f. Lohr et al. submitted) for our investigation,
which is concerned with the
detailed structural and kinematic analysis
of a flower structure within Mesozoic
strata. This data is used in turn
to determine input parameters for further
3-D geometrical retro-deformation.
The retro-deformation verifies our assumptions
about the structure and tectonic
processes, and gives further information
about sub-seismic strain distribution
with respect to the branch faults
of the flower structure.conferenc
Kinematics and Convergent Tectonics of the Northwestern South American Plate During the Cenozoic
The interaction of the northern Nazca and southwestern Caribbean oceanic plates with northwestern South America (NWSA) and the collision of the Panama-Choco arc (PCA) have significant implications on the evolution of the northern Andes. Based on a quantitative kinematic reconstruction of the Caribbean and Farallon/Farallon-derived plates, we reconstructed the subducting geometries beneath NWSA and the PCA accretion to the continent. The persistent northeastward migration of the Caribbean plate relative to NWSA in Cenozoic time caused the continuous northward advance of the Farallon-Caribbean plate boundary, which in turn resulted in its progressive concave trench bending against NWSA. The increasing complexity during the Paleogene included the onset of Caribbean shallow subduction, the PCA approaching the continent, and the forced shallow Farallon subduction that ended in the fragmentation of the Farallon Plate into the Nazca and Cocos plates and the Coiba and Malpelo microplates by the late Oligocene. The convergence tectonics after late Oligocene comprised the accretional process of the PCA to NWSA, which evolved from subduction erosion of the forearc to collisional tectonics by the middle Miocene, as well as changes of convergence angle and slab dip of the Farallon-derived plates, and the attachment of the Coiba and Malpelo microplates to the Nazca plate around 9 Ma, resulting in a change of convergence directions. During the Pliocene, the Nazca slab broke at 5.5°N, shaping the modern configuration. Overall, the proposed reconstruction is supported by geophysical data and is well correlated with the magmatic and deformation history of the northern Andes
Critical taper analysis reveals lithological control of variations in detachment strength: An analysis of the Alpine basal detachment (Swiss Alps)
Although evidence for weak detachments underlying foreland thrust belts exists, very little is known about the lateral variations in effective strength, as well as the geological nature of such variations. Using critical taper analysis, we show that a detailed and systematic measurement of surface slope of the Central European Alps reveals variations in strength parameter F along the detachment, based on the argument that the Alps are close to the critical state. We show that the basal detachment is very weak near the deformation front but strengthens toward the hinterland. Very low F (effective coefficient of friction plus normalized cohesion) values of 0.54) but may also require additional mechanisms of dynamic weakening
Seismic imaging of sandbox experiments – laboratory hardware setup and first reflection seismic sections
Abstract. With the study and technical development introduced here, we combine analogue sandbox simulation techniques with seismic physical modelling of sandbox models. For that purpose, we designed and developed a new mini-seismic facility for laboratory use, comprising a seismic tank, a PC-driven control unit, a positioning system, and piezo-electric transducers used here the first time in an array mode. To assess the possibilities and limits of seismic imaging of small-scale structures in sandbox models, different geometry setups were tested in the first experiments that also tested the proper functioning of the device and studied the seismo-elastic properties of the granular media used. Simple two-layer models of different materials and layer thicknesses as well as a more complex model comprising channels and shear zones were tested using different acquisition geometries and signal properties. We suggest using well sorted and well rounded grains with little surface roughness (glass beads). Source receiver-offsets less than 14 cm for imaging structures as small as 2.0–1.5 mm size have proven feasible. This is the best compromise between wide beam and high energy output, and being applicable with a consistent waveform. Resolution of the interfaces of layers of granular materials depends on the interface preparation rather than on the material itself. Flat grading of interfaces and powder coverage yields the clearest interface reflections. Finally, sandbox seismic sections provide images of very good quality showing constant thickness layers as well as predefined channel structures and fault traces from shear zones. Since these can be regarded in sandbox models as zones of decompaction, they behave as reflectors and can be imaged. The multiple-offset surveying introduced here improves the quality with respect to S/N-ratio and source signature even more; the maximum depth penetration in glass bead layers thereby amounts to 5 cm. Thus, the presented mini-seismic device is already able to resolve structures within simple models of saturated porous media, so that multiple-offset seismic imaging of shallow sandbox models, that are structurally evolving, is generally feasible.</jats:p
Kinematic 3D Retro-Deformation of Fault Blocks Picked from 3D Seismics
Movement on fault planes causes a large
amount of smaller-scale deformation,
ductile or brittle, in the area surrounding
the fault. Much of this deformation
is below the resolution of reflection
seismics (i.e. sub-seismic, <10m
displacement), but it is important to determine
this deformation, since it can
make up a large portion of the total bulk strain, for instance in a developing
sedimentary basin. Calculation of
the amount of sub-seismic strain around
a fault by 3-D geometrical kinematic
retro-deformation can also be used to
predict the orientation and magnitude
of these smaller-scale structures.
However, firstly a 3-D model of the fault
and its faulted horizons must be constructed
at a high enough resolution
to be able to preserve fault and horizon
morphology with a grid spacing of
less than 10 m. Secondly, the kinematics
of the fault need to be determined,
and thirdly a suitable deformation algorithm
chosen to fit the deformation
style. Then by restoring the faulted
horizons to their pre-deformation state
(a ‘regional’), the moved horizons can
be interrogated as to the strain they
underwent. Since strain is commutative,
the deformation demonstrated during
this retro-deformation is equivalent
to that during the natural, forward deformation...conferenc
Visual hallucinations associated with varenicline: a case report
<p>Abstract</p> <p>Introduction</p> <p>Varenicline is widely used for smoking cessation. It has shown efficacy over placebo and bupropion in manufacturer-sponsored trials. Those with mental illness were excluded from these trials. There are case reports of exacerbation of mental illness and development of psychiatric symptoms with varenicline use.</p> <p>Case presentation</p> <p>A 61-year-old male Caucasian being treated for post-traumatic stress disorder, depression not otherwise specified and alcohol dependence, was prescribed varenicline while he was in a post-traumatic stress disorder/alcohol dual diagnosis treatment program. He developed visual hallucinations, which became worse with titration of the medication. These symptoms resolved upon discontinuation of varenicline.</p> <p>Conclusion</p> <p>Patients with mental illness have a higher incidence of nicotine dependence, and attempts should be made for smoking cessation. Varenicline has not been widely tested in this population. There are reports of exacerbation of mental illness, and probable causation of psychiatric symptoms in the mentally ill. Providers should be aware of this possibility and advise their patients appropriately.</p
Comparison of nicotine exposure during pregnancy when smoking and abstinent with nicotine replacement therapy: systematic review and meta-analysis
Background and aims: Smoking during pregnancy is strongly associated with negative pregnancy and perinatal outcomes. Some guidelines recommend nicotine replacement therapy (NRT) for smoking cessation during pregnancy but adherence with NRT is generally poor and could be partially‐explained by nicotine‐related safety concerns. We compared pregnant women's cotinine and nicotine exposures from smoking with those when they were abstinent from smoking and using NRT.Design: Systematic review with meta‐analysis and narrative reporting. Twelve studies were included: in most only one type of NRT was used. Seven were quality‐assessed and judge of variable quality.Setting: Studies from any setting that reported nicotine or cotinine levels when smoking and later when abstinent and using NRTParticipants: Pregnant women who smoked and became abstinent but used NRT either in a cessation study or in a study investigating other impacts of NRTMeasurements: We quality‐assessed longitudinal cohort studies using a modified version of the Newcastle‐Ottawa scale. For meta‐analysis, we used mean within‐person differences in cotinine or nicotine levels when smoking and at later follow up when abstinent and using NRT. Where such data were not available, we calculated differences in group mean levels and reported these narratively, indicating where data were not completely longitudinal.Findings: Of the 12 included studies, four cotinine‐measuring studies (n = 83) were combined in a random effects meta‐analysis; the pooled estimate for the mean difference (95% confidence intervals) in cotinine levels between when women were smoking and abstinent but using NRT was 75.3 (57.1 to 93.4) ng/ml (I2 = 42.1%, p = 0.11). Of eight narratively‐described studies, six reported lower cotinine and/or nicotine levels when abstinent and using NRT; two had mixed findings with higher levels when abstinent but using NRT reported from at least one assay time point. Conclusions: Pregnant women who use nicotine replacement therapy instead of smoking reduce their nicotine exposure
Amphibious Seismic Survey Images Plate Interface at 1960 Chile Earthquake
The southern central Chilean margin at the site of the largest historically recorded earthquake in the Valdivia region, in 1960 (Mw = 9.5), is part of the 5000-km-long active subduction system whose geodynamic evolution is controversially debated and poorly understood. Covering the area between 36° and 40°S, the oceanic crust is segmented by prominent fracture zones. The offshore forearc and its onshore continuation show a complex image with segments of varying geophysical character, and several fault systems active during the past 24 m.y.
In autumn 2001, the project SPOC was organized to study the Subduction Processes Off Chile, with a focus on the seismogenic coupling zone and the forearc. The acquired seismic data crossing the Chilean subduction system were gathered in a combined offshore-onshore survey and provide new insights into the lithospheric structure and evolution of active margins with insignificant frontal accretion
Unmet needs of patients with chronic obstructive pulmonary disease (COPD): A qualitative study on patients and doctors
Background: Chronic Obstructive Pulmonary Disease (COPD) is a chronic disease with repeated exacerbations resulting in gradual debilitation. The quality of life has been shown to be poor in patients with COPD despite efforts to improve self-management. However, the evidence on the benefit of self-management in COPD is conflicting. Whether this could be due to other unmet needs of patients have not been investigated. Therefore, we aimed to explore unmet needs of patients from both patients and doctors managing COPD.
Methods: We conducted a qualitative study with doctors and patients in Malaysia. We used convenience sampling to recruit patients until data saturation. Eighteen patients and eighteen doctors consented and were interviewed using a semi-structured interview guide. The interviews were audio-recorded, transcribed verbatim and checked by the interviewers. Data were analysed using a thematic approach.
Results: The themes were similar for both the patients and doctors. Three main themes emerged: knowledge and awareness of COPD, psychosocial and physical impact of COPD and the utility of self-management. Knowledge about COPD was generally poor. Patients were not familiar with the term chronic obstructive pulmonary disease or COPD. The word ‘asthma’ was used synonymously with COPD by both patients and doctors. Most patients experienced difficulties in their psychosocial and physical functions such as breathlessness, fear and helplessness. Most patients were not confident in self-managing their illness and prefer a more passive role with doctors directing their care.
Conclusions: In conclusion, our study showed that knowledge of COPD is generally poor. There was mislabelling of COPD as asthma by both patients and physicians. This could have resulted in the lack of understanding of treatment options, outcomes, and prognosis of COPD. The misconception that cough due to COPD was contagious, and breathlessness that resulted from COPD, had important physical and psychosocial impact, and could lead to social isolation. Most patients and physicians did not favour self-management approaches, suggesting innovations based on self-management may be of limited benefit
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