On the Existence of Shadow Prices

For utility maximization problems under proportional transaction costs, it has been observed that the original market with transaction costs can sometimes be replaced by a frictionless "shadow market" that yields the same optimal strategy and utility. However, the question of whether or not this indeed holds in generality has remained elusive so far. In this paper we present a counterexample which shows that shadow prices may fail to exist. On the other hand, we prove that short selling constraints are a sufficient condition to warrant their existence, even in very general multi-currency market models with possibly discontinuous bid-ask-spreads.Comment: 14 pages, 1 figure, to appear in "Finance and Stochastics

Body fat distribution and systolic blood pressure in 10,000 adults with whole‐body imaging: UK Biobank and Oxford BioBank

Objective This study aimed to quantify the associations of regional fat mass and fat‐free mass with systolic blood pressure. Methods This analysis combined individual participant data from two large‐scale imaging studies: UK Biobank and Oxford BioBank. In both studies, participants were interviewed and measured, and they underwent dual‐energy x‐ray absorptiometry imaging. Linear regression was used to relate systolic blood pressure to anthropometric measures of adiposity (BMI, waist circumference, and waist to hip ratio) and dual‐energy x‐ray absorptiometry–derived measures of body composition (visceral android fat, subcutaneous android fat, subcutaneous gynoid fat, and fat‐free mass). Results Among 10,260 participants (mean age 49; 96% white), systolic blood pressure was positively associated with visceral android fat (3.2 mmHg/SD in men; 2.8 mmHg/SD in women) and fat‐free mass (1.92 mmHg/SD in men; 1.64 mmHg/SD in women), but there was no evidence of an association with subcutaneous android or gynoid fat. Associations of systolic blood pressure with BMI were slightly steeper than those with waist circumference or waist to hip ratio; these associations remained unchanged following adjustment for fat‐free mass, but adjustment for visceral android fat eliminated associations with waist circumference and waist to hip ratio and more than halved associations with BMI. Conclusions This analysis indicates that visceral fat is the primary etiological component of excess adiposity underlying the development of adiposity‐related hypertension.</p

Deficits of reach-to-grasp coordination following stroke: Comparison of instructed and natural movements

The present work evaluates whether stroke-induced deficits of reach-to-grasp movements, established by typical laboratory paradigms, transfer unconditionally to more natural situations.Sixteen patients with a stroke to the motor-dominant left hemisphere and 16 age- and gender-matched healthy control subjects executed grasping movements with their left (ipsilesional, non-dominant) hand. All movements started in the same position, were aimed at the same object positioned in the same location, and were followed by forward displacement of that object along the same path. Twenty movements were performed as a repetitive, externally triggered task executed for their own sake (context L, as in typical laboratory tasks). Twenty movements were performed as part of a self-initiated action sequence aimed at winning a reward (context E, similar to many everyday situations). The kinematics and dynamics of the transport, grasp and manipulation component of each reach-to-grasp movement were quantified by 41 parameters.Analyses of variance yielded a significant effect of Context for 29 parameters, a significant effect of Group for 9 parameters (mostly related to the coupling of hand transport and grip aperture), and a significant interaction for 5 parameters (all related to the coupling of hand transport and grip aperture). The interaction reflected the fact that stroke patients' movement parameters were more abnormal in context E than in context L.Our data indicate that unilateral stroke degrades the grasp-transport coupling, and that stroke-related motor deficits may be more pronounced in a natural than in a laboratory context. Thus, for stroke patients, assessments and rehabilitation regimes should mainly use activities that are as natural as possible

Body fat distribution and systolic blood pressure in 10,000 adults with whole‐body imaging: UK Biobank and Oxford BioBank

Objective This study aimed to quantify the associations of regional fat mass and fat‐free mass with systolic blood pressure. Methods This analysis combined individual participant data from two large‐scale imaging studies: UK Biobank and Oxford BioBank. In both studies, participants were interviewed and measured, and they underwent dual‐energy x‐ray absorptiometry imaging. Linear regression was used to relate systolic blood pressure to anthropometric measures of adiposity (BMI, waist circumference, and waist to hip ratio) and dual‐energy x‐ray absorptiometryandndash;derived measures of body composition (visceral android fat, subcutaneous android fat, subcutaneous gynoid fat, and fat‐free mass). Results Among 10,260 participants (mean age 49; 96% white), systolic blood pressure was positively associated with visceral android fat (3.2 mmHg/SD in men; 2.8 mmHg/SD in women) and fat‐free mass (1.92 mmHg/SD in men; 1.64 mmHg/SD in women), but there was no evidence of an association with subcutaneous android or gynoid fat. Associations of systolic blood pressure with BMI were slightly steeper than those with waist circumference or waist to hip ratio; these associations remained unchanged following adjustment for fat‐free mass, but adjustment for visceral android fat eliminated associations with waist circumference and waist to hip ratio and more than halved associations with BMI. Conclusions This analysis indicates that visceral fat is the primary etiological component of excess adiposity underlying the development of adiposity‐related hypertension.</p

Effects of rTMS on grip force control following subcortical stroke

Within the concept of interhemispheric competition we tested the effect of inhibitory 1 Hz repetitive transcranial magnetic stimulation (rTMS), applied over the primary motor cortex of the unaffected hemisphere, upon dexterity of the affected hand in subcortical stroke patients. Subjects grasped, lifted and held an instrumented object between the index finger and thumb with both the affected and unaffected hand prior to (baseline) and following 1 Hz rTMS applied over (i) the vertex (control stimulation) and (ii) the primary motor cortex of the unaffected hemisphere. Compared to baseline, 1 Hz rTMS applied over the unaffected primary motor cortex, but not the vertex, improved the efficiency and timing of grasping and lifting with the affected hand. Our data support the interhemispheric competition concept and furthermore reinforce current efforts to implement rTMS in novel approaches to stroke rehabilitation