An approximate model for cancellous bone screw fixation

This is the author's accepted manuscript. The final published article is available from the link below. Copyright @ 2013 Taylor & Francis.This paper presents a finite element (FE) model to identify parameters that affect the performance of an improved cancellous bone screw fixation technique, and hence potentially improve fracture treatment. In cancellous bone of low apparent density, it can be difficult to achieve adequate screw fixation and hence provide stable fracture fixation that enables bone healing. Data from predictive FE models indicate that cements can have a significant potential to improve screw holding power in cancellous bone. These FE models are used to demonstrate the key parameters that determine pull-out strength in a variety of screw, bone and cement set-ups, and to compare the effectiveness of different configurations. The paper concludes that significant advantages, up to an order of magnitude, in screw pull-out strength in cancellous bone might be gained by the appropriate use of a currently approved calcium phosphate cement

LUBAC assembles a ubiquitin signaling platform at mitochondria for signal amplification and transport of NF-κB to the nucleus

Mitochondria are increasingly recognized as cellular hubs to orchestrate signaling pathways that regulate metabolism, redox homeostasis, and cell fate decisions. Recent research revealed a role of mitochondria also in innate immune signaling; however, the mechanisms of how mitochondria affect signal transduction are poorly understood. Here, we show that the NF-κB pathway activated by TNF employs mitochondria as a platform for signal amplification and shuttling of activated NF-κB to the nucleus. TNF treatment induces the recruitment of HOIP, the catalytic component of the linear ubiquitin chain assembly complex (LUBAC), and its substrate NEMO to the outer mitochondrial membrane, where M1- and K63-linked ubiquitin chains are generated. NF-κB is locally activated and transported to the nucleus by mitochondria, leading to an increase in mitochondria-nucleus contact sites in a HOIP-dependent manner. Notably, TNF-induced stabilization of the mitochondrial kinase PINK1 furthermore contributes to signal amplification by antagonizing the M1-ubiquitin-specific deubiquitinase OTULIN. Overall, our study reveals a role for mitochondria in amplifying TNF-mediated NF-κB activation, both serving as a signaling platform, as well as a transport mode for activated NF-κB to the nuclear

A Political Winner’s Curse: Why Preventive Policies Pass Parliament so Narrowly

Preventive policy measures such as bailouts often pass parliament very narrowly. We present a model of asymmetric information between politicians and voters which rationalizes this narrow parliamentary outcome. A successful preventive policy impedes the verification of its own necessity. When policy intervention is necessary but voters disagree ex-ante, individual politicians have an incentive to loose the vote in parliament in order to be rewarded by voters ex-post. Comfortable vote margins induce incentives to move to the loosing fraction to avoid this winner's curse. In equilibrium, parliamentary elections over preventive policies are thus likely to end at very narrow margins.Politikmaßnahmen zur Prävention einer drohenden Krise wie Bankenrettungen oder Finanzhilfen an notleidende Staaten erhalten häufig nur eine knappe Mehrheit im Parlament. Im vorliegenden Beitrag wird ein polit-ökonomisches Modell asymmetrischer Informationen zwischen Politikern und Wählern vorgestellt, aus dem sich diese knappen Parlamentsabstimmungen erklären lassen. Annahmegemäß haben die Politiker im Vorfeld der Parlamentsabstimmung (ex-ante) einen Informationsvorsprung gegenüber den Wählern was die Notwendigkeit der präventiven Politikmaßnahme betrifft. Selbst nach der Entscheidung über die Durchsetzung der Maßnahme (ex-post) erfahren die Wähler nur dann, ob die Maßnahme notwendig war, wenn sie nicht durchgesetzt wurde und die Folgen der ausbleibenden Krisenprävention sichtbar werden. Sofern die präventive Politik tatsächlich notwendig ist, um Schaden abzuwenden, die Wähler dies ex-ante aber nicht glauben, ergibt sich eine interessante Konstellation: Folgen die Politiker dem ex-ante-Willen der Wähler und wird dementsprechend die Politik nicht umgesetzt, tritt der volkswirtschaftliche Schaden auf. Dies wird ex-post offenkundig und die Wähler strafen die Politiker für ihre fehlerhafte Politik bei der nachfolgendenden Wahl ab. Entscheiden sich die Politiker hingegen dafür, die Politik zur Krisenprävention durchzusetzen, kann der Schaden abgewendet werden. Allerdings bleiben die Wähler ex-post im Unklaren darüber, ob die Politikmaßnahme tatsächlich notwendig war und somit bei ihrer ex-ante-Einstellung. Auch dann werden die Politiker für ihre als fehlerhaft erachtete Politik abgestraft. Hieraus ergibt sich für einen einzelnen Politiker im Parlament eine Situation, die im Aufsatz als Winner's Curse bezeichnet wird: Er erhält nur dann die Zustimmung der Wähler, wenn die Politik im Parlament durchgesetzt wird, er aber dagegen gestimmt hat, oder die Politik keine Mehrheit im Parlament erhält, er aber dafür gestimmt hat. Im Falle eines eindeutigen Mehrheitsverhältnisses entstehen somit individuelle Anreize, zur Minderheit abzuweichen. Die Wahrscheinlichkeit eines knappen Wahlausgangs steigt durch diese Anreize zur Abweichung

Well-Being in Germany: GDP and Unemployment Still Matter

This paper examines regional differences in subjective well-being (SWB) in Germany. Inferential statistics indicate a diminishing but still significant gap between East and West Germany, but also differing levels of SWB within both parts. The observed regional pattern of life satisfaction reflects macroeconomic fundamentals, where labor market conditions play a dominant role. Differing levels of GDP and economic growth have contributed rather indirectly to regional well-being such that the years since the German reunification can be considered as a period of joyless growth. Approximately half of the satisfaction gap between East and West Germany can be attributed to differing macroeconomic conditions. Moreover, we argue that it is advisable for governments to collect more data on aspects that presumably influence the well-being of society. For example, it is highly probable that reliable data on regional income inequality would lead to several important and influential studies. This, in turn, can help to design indicators for those characteristics which are known for affecting SWB. In total, we do not perceive any fundamental caveat for using data on SWB in order to measure welfare directly, at least within culturally and linguistically homogenous regions. To reduce statistical uncertainty, however, it would be helpful to include subjective information of this kind into larger cross-sectional surveys such as common census data

Default Rates in the Loan Market for SMEs: Evidence from Slovakia

The current crisis raises the question whether loans to SMEs in emerging markets areinherently more risky. We use a unique unbalanced panel of nearly 700 loans made toSMEs in Slovakia between 2000 and 2005. Several probit and panel probit models showthat liquidity and profitability factors are important determinants of SME defaults.Moreover, we find that indebtedness significantly increases the probability of default.Finally, liability as proxied by the legal form of SMEs has important incentive effects.In sum, default rates and factors converged to values found in developed financialmarkets

Vertebroplasty and kyphoplasty: a comparative review of efficacy and adverse events

Vertebroplasty and kyphoplasty have become common surgical techniques for the treatment of vertebral compression fractures. Vertebroplasty involves the percutaneous injection of bone cement into the cancellous bone of a vertebral body with the goals of pain alleviation and preventing further loss of vertebral body height. Kyphoplasty utilizes an inflatable balloon to create a cavity for the cement with the additional potential goals of restoring height and reducing kyphosis. Vertebroplasty and kyphoplasty are effective treatment options for the reduction of pain associated with vertebral body compression fractures. Biomechanical studies demonstrate that kyphoplasty is initially superior for increasing vertebral body height and reducing kyphosis, but these gains are lost with repetitive loading. Complications secondary to extravasation of cement include compression of neural elements and venous embolism. These complications are rare but more common with vertebroplasty. Vertebroplasty and kyphoplasty are both safe and effective procedures for the treatment of vertebral body compression fractures

Unraveling Short- and Farsightedness in Politics

The absence of the deselection threat in incumbents’ last term in office can be negative or positive for society. Some politicians may reduce their efforts, while others may pursue beneficial long-term policies that may be unpopular in the short term. We propose a novel pension system that solves the effort problem while preserving willingness to implement long-term policies. The idea is to give politicians the option to choose between a flexible pension scheme and a fixed pension scheme. In a flexible pension scheme, the pension increases with short term performance as measured by the vote share of the officeholder’s party in the next election. This system increases social welfare by letting officeholders self-select into those activities that most benefit society. We analyze the properties and consequences of such a system and assess its robustness. Finally, we extend the pension system with choice to non-last-term situations and derive a general welfare result