Semiflexible Chains under Tension

A functional integral formalism is used to derive the extension of a stiff chain subject to an external force. The force versus extension curves are calculated using a meanfield approach in which the hard constraint $u^2(s)=1$ is replaced by a global constraint $= 1$ where $u(s)$ is the tangent vector describing the chain and $s$ is the arc length. The theory ``quantitatively'' reproduces the experimental results for DNA that is subject to a constant force. We also treat the problems of a semiflexible chain in a nematic field. In the limit of weak nematic field strength our treatment reproduces the exact results for chain expansion parallel to the director. When the strength of nematic field is large, a situation in which there are two equivalent minima in the free energy, the intrinsically meanfield approach yields incorrect results for the dependence of the persistence length on the nematic field.Comment: 14 pages, 1 figure available upon request, submitted to J. Chem. Phy

Small and Medium sized Enterprises’ Collaborative Buyer-Supplier Relationships: Boundary Spanning Individual Perspectives

Boundary-spanning individuals (BSIs) play a critical role in supply chain management, especially in small and medium sized enterprises (SMEs) where interactions with buyers and suppliers can depend heavily on just a few individuals. This study, utilizing data from Korean manufacturing-sector SMEs, explores whether cooperative social value orientations of SMEs’ BSIs influence the effects of collaborative buyer-supplier initiatives. The results suggested that the performance implication of decision-sharing initiative increases when BSIs have a high level of cooperative social value orientation. However, it also negatively moderates the relationship between risk/benefit sharing (involving financial losses or gains) and performance suggesting possible negative side-effects. However, we found that such orientation also negatively moderates the relationship between risk/benefit sharing (involving direct financial losses or gains) and relationship performance suggesting possible negative side-effects

L2L_2 boosting in kernel regression

In this paper, we investigate the theoretical and empirical properties of $L_2$ boosting with kernel regression estimates as weak learners. We show that each step of $L_2$ boosting reduces the bias of the estimate by two orders of magnitude, while it does not deteriorate the order of the variance. We illustrate the theoretical findings by some simulated examples. Also, we demonstrate that $L_2$ boosting is superior to the use of higher-order kernels, which is a well-known method of reducing the bias of the kernel estimate.Comment: Published in at http://dx.doi.org/10.3150/08-BEJ160 the Bernoulli (http://isi.cbs.nl/bernoulli/) by the International Statistical Institute/Bernoulli Society (http://isi.cbs.nl/BS/bshome.htm

Impact of use of optical surface imaging on initial patient setup for stereotactic body radiotherapy treatments

Purpose To evaluate the effectiveness of surface image guidance (SG) for pre‐imaging setup of stereotactic body radiotherapy (SBRT) patients, and to investigate the impact of SG reference surface selection on this process. Methods and materials 284 SBRT fractions (SG‐SBRT = 113, non‐SG‐SBRT = 171) were retrospectively evaluated. Differences between initial (pre‐imaging) and treatment couch positions were extracted from the record‐and‐verify system and compared for the two groups. Rotational setup discrepancies were also computed. The utility of orthogonal kVs in reducing CBCT shifts in the SG‐SBRT/non‐SG‐SBRT groups was also calculated. Additionally, the number of CBCTs acquired for setup was recorded and the average for each cohort was compared. These data served to evaluate the effectiveness of surface imaging in pre‐imaging patient positioning and its potential impact on the necessity of including orthogonal kVs for setup. Since reference surface selection can affect SG setup, daily surface reproducibility was estimated by comparing camera‐acquired surface references (VRT surface) at each fraction to the external surface of the planning CT (DICOM surface) and to the VRT surface from the previous fraction. Results The reduction in all initial‐to‐treatment translation/rotation differences when using SG‐SBRT was statistically significant (Rank‐Sum test, α = 0.05). Orthogonal kV imaging kept CBCT shifts below reimaging thresholds in 19%/51% of fractions for SG‐SBRT/non‐SG‐SBRT cohorts. Differences in average number of CBCTs acquired were not statistically significant. The reference surface study found no statistically significant differences between the use of DICOM or VRT surfaces. Conclusions SG‐SBRT improved pre‐imaging treatment setup compared to in‐room laser localization alone. It decreased the necessity of orthogonal kV imaging prior to CBCT but did not affect the average number of CBCTs acquired for setup. The selection of reference surface did not have a significant impact on initial patient positioning

First-Fit is Linear on Posets Excluding Two Long Incomparable Chains

A poset is (r + s)-free if it does not contain two incomparable chains of size r and s, respectively. We prove that when r and s are at least 2, the First-Fit algorithm partitions every (r + s)-free poset P into at most 8(r-1)(s-1)w chains, where w is the width of P. This solves an open problem of Bosek, Krawczyk, and Szczypka (SIAM J. Discrete Math., 23(4):1992--1999, 2010).Comment: v3: fixed some typo

Employer-Sponsored Health Insurance: Down, But Not Out

Presents findings from twelve metropolitan areas about employers' efforts to control employee healthcare costs in response to the recession and national healthcare reform by firm size. Projects employer trends through 2014, including greater cost sharing

Exact solution of DND_N type quantum Calogero model through a mapping to free harmonic oscillators

We solve the eigenvalue problem of the $D_N$ type of Calogero model by mapping it to a set of decoupled quantum harmonic oscillators through a similarity transformation. In particular, we construct the eigenfunctions of this Calogero model from those of bosonic harmonic oscillators having either all even parity or all odd parity. It turns out that the eigenfunctions of this model are orthogonal with respect to a nontrivial inner product, which can be derived from the quasi-Hermiticity property of the corresponding conserved quantities.Comment: 16 page