The influence of artificially increased hip and trunk stiffness on balance control in man

Lightweight corsets were used to produce mid-body stiffening, rendering the hip and trunk joints practically inflexible. To examine the effect of this artificially increased stiffness on balance control, we perturbed the upright stance of young subjects (20-34years of age) while they wore one of two types of corset or no corset at all. One type, the "half-corset”, only increased hip stiffness, and the other, the "full-corset”, increased stiffness of the hips and trunk. The perturbations consisted of combined roll and pitch rotations of the support surface (7.5deg, 60deg/s) in one of six different directions. Outcome measures were biomechanical responses of the legs, trunk, arms and head, and electromyographic (EMG) responses from leg, trunk, and upper arm muscles. With the full-corset, a decrease in forward stabilising trunk pitch rotation compared to the no-corset condition occurred for backward pitch tilts of the support surface. In contrast, the half-corset condition yielded increased forward trunk motion. Trunk backward pitch motion after forwards support-surface perturbations was the same for all corset conditions. Ankle torques and lower leg angle changes in the pitch direction were decreased for both corset conditions for forward pitch tilts of the support-surface but unaltered for backward tilts. Changes in trunk roll motion with increased stiffness were profound. After onset of a roll support-surface perturbation, the trunk rolled in the opposite direction to the support-surface tilt for the no-corset and half-corset conditions, but in the same direction as the tilt for the full-corset condition. Initial head roll angular accelerations (at 100ms) were larger for the full-corset condition but in the same direction (opposite platform tilt) for all conditions. Arm roll movements were initially in the same direction as trunk movements, and were followed by large compensatory arm movements only for the full-corset condition. Leg muscle (soleus, peroneus longus, but not tibialis anterior) balance-correcting responses were reduced for roll and pitch tilts under both corset conditions. Responses in paraspinals were also reduced. These results indicate that young healthy normals cannot rapidly modify movement strategies sufficiently to account for changes in link flexibility following increases in hip and trunk stiffness. The changes in leg and trunk muscle responses failed to achieve a normal roll or pitch trunk end position at 700ms (except for forward tilt rotations), even though head accelerations and trunk joint proprioception seemed to provide information on changed trunk movement profiles over the first 300ms following the perturbation. The major adaptation to stiffness involved increased use of arm movements to regain stability. The major differences in trunk motion for the no-corset, half-corset and full-corset conditions support the concept of a multi-link pendulum with different control dynamics in the pitch and roll planes as a model of human stance. Stiffening of the hip and trunk increases the likelihood of a loss of balance laterally and/or backwards. Thus, these results may have implications for the elderly and others, with and without disease states, who stiffen for a variety of reason

Vacuum distillation/vapor filtration water recovery

The development and evaluation of a vacuum distillation/vapor filtration (VD/VF) water recovery system are considered. As a functional model, the system converts urine and condensates waste water from six men to potable water on a steady-state basis. The system is designed for 180-day operating durations and for function on the ground, on zero-g aircraft, and in orbit. Preparatory tasks are summarized for conducting low gravity tests of a vacuum distillation/vapor filtration system for recovering water from urine

A high-precision polarimeter

We have built a polarimeter in order to measure the electron beam polarization in hall C at JLAB. Using a superconducting solenoid to drive the pure-iron target foil into saturation, and a symmetrical setup to detect the Moller electrons in coincidence, we achieve an accuracy of <1%. This sets a new standard for Moller polarimeters.Comment: 17 pages, 9 figures, submitted to N.I.

Local control of intestinal stem cell homeostasis by enteroendocrine cells in the adult <i>Drosophila</i> midgut

Background: Enteroendocrine cells populate gastrointestinal tissues and are known to translate local cues into systemic responses through the release of hormones into the bloodstream.&lt;p&gt;&lt;/p&gt; Results: Here we report a novel function of enteroendocrine cells acting as local regulators of intestinal stem cell (ISC) proliferation through modulation of the mesenchymal stem cell niche in the &lt;i&gt;Drosophila&lt;/i&gt; midgut. This paracrine signaling acts to constrain ISC proliferation within the epithelial compartment. Mechanistically, midgut enteroendocrine cells secrete the neuroendocrine hormone Bursicon, which acts—beyond its known roles in development—as a paracrine factor on the visceral muscle (VM). Bursicon binding to its receptor, DLGR2, the ortholog of mammalian leucine-rich repeat-containing G protein-coupled receptors (LGR4-6), represses the production of the VM-derived EGF-like growth factor Vein through activation of cAMP.&lt;p&gt;&lt;/p&gt; Conclusions: We therefore identify a novel paradigm in the regulation of ISC quiescence involving the conserved ligand/receptor Bursicon/DLGR2 and a previously unrecognized tissue-intrinsic role of enteroendocrine cells.&lt;p&gt;&lt;/p&gt

Do Empowered Front-Line Employees Perform Better? A Non-linear Approach and the Role of Service Complexity

This study re-examines the influence of front-line service employee empowerment on their performance, following a non-linear approach and integrating the role of service complexity. For that purpose, data were collected through a quantitative survey on 240 front-line employees in two major UK cities (London, Leeds). The study’s results indicate that empowerment has a significant impact on their performance and that this impact is non-linear (quadratic). Specifically, the relationship between empowerment and performance is negative for low-level empowerment and positive for high-level empowerment. In addition, the study’s results show that the nature of this relationship is different for different levels of service complexity. Specifically, for low-complexity services, the relationship between empowerment and performance was found quadratic, whereas for high-complexity services the relationship was found positive and linear. Based on the study’s main conclusions important implications for both academics and practitioners are presented

Coherent States of the q--Canonical Commutation Relations

For the $q$-deformed canonical commutation relations $a(f)a^\dagger(g) = (1-q)\,\langle f,g\rangle{\bf1}+q\,a^\dagger(g)a(f)$ for $f,g$ in some Hilbert space ${\cal H}$ we consider representations generated from a vector $\Omega$ satisfying $a(f)\Omega=\langle f,\phi\rangle\Omega$, where $\phi\in{\cal H}$. We show that such a representation exists if and only if $\Vert\phi\Vert\leq1$. Moreover, for $\Vert\phi\Vert<1$ these representations are unitarily equivalent to the Fock representation (obtained for $\phi=0$). On the other hand representations obtained for different unit vectors $\phi$ are disjoint. We show that the universal C*-algebra for the relations has a largest proper, closed, two-sided ideal. The quotient by this ideal is a natural $q$-analogue of the Cuntz algebra (obtained for $q=0$). We discuss the Conjecture that, for $d<\infty$, this analogue should, in fact, be equal to the Cuntz algebra itself. In the limiting cases $q=\pm1$ we determine all irreducible representations of the relations, and characterize those which can be obtained via coherent states.Comment: 19 pages, Plain Te

Water isotopes in desiccating lichens

The stable isotopic composition of water is routinely used as a tracer to study water exchange processes in vascular plants and ecosystems. To date, no study has focussed on isotope processes in non-vascular, poikilohydric organisms such as lichens and bryophytes. To understand basic isotope exchange processes of non-vascular plants, thallus water isotopic composition was studied in various green-algal lichens exposed to desiccation. The study indicates that lichens equilibrate with the isotopic composition of surrounding water vapour. A model was developed as a proof of concept that accounts for the specific water relations of these poikilohydric organisms. The approach incorporates first their variable thallus water potential and second a compartmentation of the thallus water into two isotopically distinct but connected water pools. Moreover, the results represent first steps towards the development of poikilohydric organisms as a recorder of ambient vapour isotopic composition

Inclusive Electron-Nucleus Scattering at Large Momentum Transfer

Inclusive electron scattering is measured with 4.045 GeV incident beam energy from C, Fe and Au targets. The measured energy transfers and angles correspond to a kinematic range for Bjorken $x > 1$ and momentum transfers from $Q^2 = 1 - 7 (GeV/c)^2$. When analyzed in terms of the y-scaling function the data show for the first time an approach to scaling for values of the initial nucleon momenta significantly greater than the nuclear matter Fermi-momentum (i.e. $> 0.3$ GeV/c).Comment: 5 pages TEX, 5 Postscript figures also available at http://www.krl.caltech.edu/preprints/OAP.htm

SoDA2: a Hidden Markov Model approach for identification of immunoglobulin rearrangements

Motivation: The inference of pre-mutation immunoglobulin (Ig) rearrangements is essential in the study of the antibody repertoires produced in response to infection, in B-cell neoplasms and in autoimmune disease. Often, there are several rearrangements that are nearly equivalent as candidates for a given Ig gene, but have different consequences in an analysis. Our aim in this article is to develop a probabilistic model of the rearrangement process and a Bayesian method for estimating posterior probabilities for the comparison of multiple plausible rearrangements