Constraining dark matter halo profiles and galaxy formation models using spiral arm morphology. II. Dark and stellar mass concentrations for 13 nearby face-on galaxies

We investigate the use of spiral arm pitch angles as a probe of disk galaxy mass profiles. We confirm our previous result that spiral arm pitch angles (P) are well correlated with the rate of shear (S) in disk galaxy rotation curves. We use this correlation to argue that imaging data alone can provide a powerful probe of galactic mass distributions out to large look-back times. We then use a sample of 13 galaxies, with Spitzer 3.6-$\mu$m imaging data and observed H$\alpha$ rotation curves, to demonstrate how an inferred shear rate coupled with a bulge-disk decomposition model and a Tully-Fisher-derived velocity normalization can be used to place constraints on a galaxy's baryon fraction and dark matter halo profile. Finally we show that there appears to be a trend (albeit a weak correlation) between spiral arm pitch angle and halo concentration. We discuss implications for the suggested link between supermassive black hole (SMBH) mass and dark halo concentration, using pitch angle as a proxy for SMBH mass.Comment: 14 pages, 6 figures. Accepted for publication in the Astrophysical Journa

The Limits of Regulation by Insurance

Insurance is an enormously powerful and beneficial method of spreading risk and compensating for loss. But even insurance has its limits. A new and misleading aspiration for insurance—that it also can and often does substitute for or significantly complement health and safety regulation—is increasingly in vogue. This vision starts from the uncontroversial recognition that insurers typically adopt measures designed to counteract “moral hazard,” the tendency of insurance to blunt policyholders’ incentives to take care. But proponents of this vision go on to contend that the risk-reducing potential of insurance is significantly more extensive than is traditionally imagined, because insurers are strategically positioned to induce their policyholders to embrace precautions, procedures, policies, or training regimens that decrease the incidence of loss. Proponents of this new “regulation thesis” often dramatically summarize these points by describing insurance as a form of private “regulation” or “loss prevention,” attempting to trade on the positive optics of these notions. Enamored with this idea, commentators, activists, and lawmakers have advanced various proposals to mandate the purchase of insurance or otherwise intervene in insurance markets to address a broad range of modern social ills, including police misconduct, gun violence, cyberattacks, and harms caused by artificial intelligence. Building on emerging criticism of this regulation thesis as well as increasing empirical evidence questioning its accuracy, this Article argues that these regulatory aspirations for insurance are over-optimistic. Creating less loss than insurance otherwise might have created is not regulation or loss prevention. Rather, it is damage-control, and that is what insurance devices designed to combat moral hazard almost always involve. Insurers face a daunting set of obstacles to further reducing policyholder risk below what it would be in the absence of insurance. In short, insurance has substantial limits as a solution for the failures of regulation

Angiotensin II blockade and aortic-root dilation in Marfan's syndrome

Background: Progressive enlargement of the aortic root, leading to dissection, is the main cause of premature death in patients with Marfan's syndrome. Recent data from mouse models of Marfan's syndrome suggest that aortic-root enlargement is caused by excessive signaling by transforming growth factor (beta) (TGF-(beta)) that can be mitigated by treatment with TGF-(beta) antagonists, including angiotensin II-receptor blockers (ARBs). We evaluated the clinical response to ARBs in pediatric patients with Marfan's syndrome who had severe aortic-root enlargement. Methods: We identified 18 pediatric patients with Marfan's syndrome who had been followed during 12 to 47 months of therapy with ARBs after other medical therapy had failed to prevent progressive aortic-root enlargement. The ARB was losartan in 17 patients and irbesartan in 1 patient. We evaluated the efficacy of ARB therapy by comparing the rates of change in aortic-root diameter before and after the initiation of treatment with ARBs. Results: The mean (+/-SD) rate of change in aortic-root diameter decreased significantly from 3.54+/-2.87 mm per year during previous medical therapy to 0.46+/-0.62 mm per year during ARB therapy (P<0.001). The deviation of aortic-root enlargement from normal, as expressed by the rate of change in z scores, was reduced by a mean difference of 1.47 z scores per year (95% confidence interval, 0.70 to 2.24; P<0.001) after the initiation of ARB therapy. The sinotubular junction, which is prone to dilation in Marfan's syndrome as well, also showed a reduced rate of change in diameter during ARB therapy (P<0.05), whereas the distal ascending aorta, which does not normally become dilated in Marfan's syndrome, was not affected by ARB therapy. Conclusions: In a small cohort study, the use of ARB therapy in patients with Marfan's syndrome significantly slowed the rate of progressive aortic-root dilation. These findings require confirmation in a randomized trial

Vulnerabilities in first-generation RFID-enabled credit cards

Credit cards ; Radio frequency identification systems