186 research outputs found
Ecumenical modal logic
The discussion about how to put together Gentzen's systems for classical and
intuitionistic logic in a single unified system is back in fashion. Indeed,
recently Prawitz and others have been discussing the so called Ecumenical
Systems, where connectives from these logics can co-exist in peace. In Prawitz'
system, the classical logician and the intuitionistic logician would share the
universal quantifier, conjunction, negation, and the constant for the absurd,
but they would each have their own existential quantifier, disjunction, and
implication, with different meanings. Prawitz' main idea is that these
different meanings are given by a semantical framework that can be accepted by
both parties. In a recent work, Ecumenical sequent calculi and a nested system
were presented, and some very interesting proof theoretical properties of the
systems were established. In this work we extend Prawitz' Ecumenical idea to
alethic K-modalities
Increased thromboxane biosynthesis is associated with poststroke dementia
BACKGROUND AND PURPOSE: It has been suggested that daily intake of aspirin
is associated with a reduction of cognitive decline, both in normal and in
demented subjects, but the mechanism is unclear. We have therefore studied
the relationship between thromboxane (TX) A(2) biosynthesis, as reflected
by the urinary excretion of 11-dehydro-TXB(2), and the presence of
dementia in patients after acute stroke. METHODS: Patients from the
Rotterdam Stroke Databank were screened for dementia between 3 and 9
months after stroke. Patients had a full neurological examination,
neuropsychological screening, and, if indicated, extensive
neuropsychological examination. Criteria used for the diagnosis of
dementia were from the Diagnostic and Statistical Manual of Mental
Disorders, Third Edition (Revised). Urine samples were taken at the time
of screening. Urinary 11-dehydro-TXB(2) was measured by means of a
previously validated radioimmunoassay. RESULTS: Dementia was diagnosed in
71 patients, and urine samples were available for 62. Median value (range)
of 11-dehydro-TXB(2) was 399 (89 to 2105) pmol/mmol creatinine for
demented patients versus 273 (80 to 1957) for 69 controls with stroke but
without dementia (P=0.013). No difference was found between 44 patients
with vascular dementia, 404 (89 to 2105) pmol/mmol creatinine, and 18
patients with Alzheimer's disease plus cerebrovascular disease, 399 (96 to
1467) pmol/mmol creatinine (P=0.68). In a stepwise logistic regression
analysis, in which possible confounders such as use of antiplatelet
medication, cardiovascular risk factors, and type of stroke were taken
into account, increased urinary excretion of 11-dehydro-TXB(2) remained
independently related to the presence of dementia (OR 1.12, 95% CI 1.03 to
1.22 per 100 pmol/mmol creatinine). The difference in metabolite excretion
rates between demented and nondemented patients was most prominent within
the subgroup of ischemic stroke patients who received aspirin (P<0.01).
CONCLUSIONS: Increased thromboxane biosynthesis in the chronic phase after
stroke is associated with the presence of but not the type of poststroke
dementia. It is particularly apparent in patients on aspirin, thereby
suggesting the involvement of extraplatelet sources of TXA(2) production
in this setting
Platelet activation and lipid peroxidation in patients with acute ischemic stroke
BACKGROUND AND PURPOSE: Both platelet activation and lipid peroxidation are potential sources of vasoactive eicosanoids that can be produced via the cyclooxygenase pathway, ie, thromboxane (TX) A2, or by free radical-catalyzed peroxidation of arachidonic acid, ie, isoprostanes. We investigated the biosynthesis of TXA2 and F2-isoprostanes, as reflected by the urinary excretion of 11-dehydro-TXB2 and 8-epi-prostaglandin (PG) F2 alpha respectively, in 62 consecutive patients (30 men, 32 women; mean age, 67 +/- 14 years) with acute ischemic stroke.
METHODS: At least two consecutive 6-hour urine samples were obtained during the first 72 hours after onset of symptoms. Urinary eicosanoids were measured by previously described radioimmunoassays.
RESULTS: Repeated periods of enhanced thromboxane biosynthesis were found in 52% of patients. Urinary 11-dehydro-TXB2 averaged 221 +/- 207 (mean +/- SD; n = 197; range, 13 to 967) pmol/mmol creatinine in 30 patients treated with cyclooxygenase inhibitors (mostly aspirin) at the time of study versus 392 +/- 392 (n = 186; range, 26 to 2533) in 32 untreated patients (P .05). The correlation between the two metabolites was moderate in both untreated patients (r = .41, P < .001) and patients with cyclooxygenase inhibitors (r = .31, P < .001). In a multiple regression analysis, increased thromboxane production was independently associated with severity of stroke on admission, atrial fibrillation, and treatment with cyclooxygenase-inhibiting drugs.
CONCLUSIONS: We conclude that during the first few days after an acute ischemic stroke (1) platelet activation occurs repeatedly in a cyclooxygenase-dependent fashion; (2) platelet activation is not associated with concurrent changes in isoprostane biosynthesis; (3) platelet activation is independently associated with stroke severity and atrial fibrillation; and (4) isoprostane biosynthesis is largely independent of platelet cyclooxygenase activity
Generic Modal Cut Elimination Applied to Conditional Logics
We develop a general criterion for cut elimination in sequent calculi for
propositional modal logics, which rests on absorption of cut, contraction,
weakening and inversion by the purely modal part of the rule system. Our
criterion applies also to a wide variety of logics outside the realm of normal
modal logic. We give extensive example instantiations of our framework to
various conditional logics. For these, we obtain fully internalised calculi
which are substantially simpler than those known in the literature, along with
leaner proofs of cut elimination and complexity. In one case, conditional logic
with modus ponens and conditional excluded middle, cut elimination and
complexity were explicitly stated as open in the literature
Towards a Proof Theory of G\"odel Modal Logics
Analytic proof calculi are introduced for box and diamond fragments of basic
modal fuzzy logics that combine the Kripke semantics of modal logic K with the
many-valued semantics of G\"odel logic. The calculi are used to establish
completeness and complexity results for these fragments
OC-0473: Intraoperative radiotherapy (IORT) in breast cancer: analysis of 6,816 cases from ISIORT database
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