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A magnetically driven piston pump for xenon gas recirculation is presented. The pump is designed to satisfy extreme purity and containment requirements, as is appropriate for the recirculation of isotopically enriched xenon through the purification system and large liquid xenon time projection chamber of EXO-200. The pump, using sprung polymer gaskets, is capable of pumping more than 16 standard liters per minute of xenon gas with 750 Torr differential pressure.

Supercooled liquids demonstrate stretched exponential relaxations consistent with the presence of spatially heterogeneous dynamics. Many experimental results are consistent with this picture, but differences in experimental approach may lead to different conclusions about the degree of heterogeneity in a given system. Here, we investigate whether observables accessible with single molecule (SM) approaches are consistent with each other and with ensemble measurements. In particular, the distribution of rotational relaxation times, τ(c), obtained from SM measurements is compared with the stretching exponent determined from a quasi-ensemble treatment of the same data. It is shown that the time-limited trajectories typical of SM experiments can lead to a stretching exponent that suggests homogeneous dynamics even in the presence of heterogeneous dynamics. After correction for the time-limited trajectories, additional discrepancy remains between stretching exponents measured via SM experiments and ensemble techniques. The remaining difference is attributed to the limited dynamic range of the SM experiments.

Spatially heterogeneous dynamics in supercooled glycerol over the temperature range 198 K (1.04T(g))-212 K (1.12T(g)) is investigated using widefield single molecule (SM) fluorescence microscopy. Measurements are performed using three different perylenedicarboximide probes to investigate whether probe size and probe-host interactions affect breadth of heterogeneity reported in the glassy host by such SM experiments. Rotational relaxation times of single probe molecules are measured, and for all probes, log-normal distributions of relaxation times are found. No significant change in relaxation time distribution as a function of temperature is evident for a given probe. However, across probes, probe rotational relaxation time is correlated with breadth of heterogeneous dynamics reported. Molecules that undergo changes in dynamics are identified using two complementary approaches that interrogate time scales between 10(3) and 10(6) τ(α), with τ(α) the structural relaxation time of glycerol. Exchange is found on the shortest time scales probed (~30 τ(c), with τ(c) the rotational correlation time of the probe) and is relatively temperature and probe independent. No evidence is found for additional exchange occurring on the longest time scales interrogated. Taken together with the fact that probes that rotate the fastest report the greatest breadth of spatially heterogeneous dynamics in the system, this indicates that exchange times reported from analysis of SM linear dichroism trajectories as described here are upper bounds on the average exchange time in the system.

The electric form factor of the neutron was determined from studies of the reaction 3He(e,e'n)pp in quasielastic kinematics in Hall A at Jefferson Lab. Longitudinally polarized electrons were scattered off a polarized target in which the nuclear polarization was oriented perpendicular to the momentum transfer. The scattered electrons were detected in a magnetic spectrometer in coincidence with neutrons that were registered in a large-solid-angle detector. More than doubling the Q2 range over which it is known, we find G(E)(n)=0.0236±0.0017(stat)±0.0026(syst), 0.0208±0.0024±0.0019, and 0.0147±0.0020±0.0014 for Q(2)=1.72, 2.48, and 3.41 GeV2, respectively.

We describe a source capable of producing single barium ions through nuclear recoils in radioactive decay. The source is fabricated by electroplating (148)Gd onto a silicon α-particle detector and vapor depositing a layer of BaF(2) over it. (144)Sm recoils from the alpha decay of (148)Gd are used to dislodge Ba(+) ions from the BaF(2) layer and emit them in the surrounding environment. The simultaneous detection of an α particle in the substrate detector allows for tagging of the nuclear decay and of the Ba(+) emission. The source is simple, durable, and can be manipulated and used in different environments. We discuss the fabrication process, which can be easily adapted to emit most other chemical species, and the performance of the source.

Gelation temperatures from 22 degrees C to 37 degrees C were used to control the pore size of collagen matrices independent of collagen concentration. To limit cell exposure to temperatures lower than physiological temperature, the putative nucleation and growth mechanism of collagen was investigated to determine the time at which gel fibril and network structure becomes independent of temperature. It was found that the temperature dependent portion of collagen gelation ends close to the time at which fibrils first form a network spanning structure. These findings were then exploited to prepare cell-embedded gels nucleated at 22, 27, or 32 degrees C and then incubated at 37 degrees C. This achieves fibrillar and network structure characteristic of gels formed solely at the nucleation temperature. Proof of principle studies of glioma invasion in these gels suggested pore size is a key determinant of glioma invasive speed in collagen gels., (Copyright (c) 2010 Elsevier Ltd. All rights reserved.)

High grade gliomas are aggressive cancers that are not well addressed by current chemotherapies, in large measure because these drugs do not curtail the diffuse invasion of glioma cells into brain tissue surrounding the tumor. Here, we investigate the effects of suberoylanilide hydroxamic acid (SAHA) on glioma cells in 2D and 3D in vitro assays, as SAHA has previously been shown to significantly increase apoptosis, decrease proliferation, and interfere with migration in other cell lines. We find that SAHA has significant independent effects on proliferation, migration, and invasion. These effects are seen in both 2D and 3D culture. In 3D culture, with glioma spheroids embedded in collagen I matrices, SAHA independently limits both glioma invasion and the reorganization of the tumor surroundings that usually proceeds such invasion. The decreased matrix reorganization and invasion is not accompanied by decreased production or activity of matrix-metalloproteases but instead may be related to increased cell-cell adhesion., (Copyright 2009 Elsevier Ireland Ltd. All rights reserved.)

We quantify spatial and temporal heterogeneity in supercooled glycerol at T=T(g)+14 K employing a widefield detection scheme and using rubrene as the probe molecule. We describe how microscopy configuration affects measured intensity, linear dichroism, and the resulting autocorrelation function. Rotational relaxation times tau(c) of 241 probe molecules are measured, and we find spatial heterogeneity over almost three orders of magnitude present at this temperature. An approach for detecting temporally heterogeneous molecules and quantifying exchange times is introduced. Of molecules that can be assessed, approximately 15% display evidence of temporal heterogeneity-changes of tau(c) during the measurement-that are detected with the analysis technique employed. Exchanges between dynamically disparate environments occur rarely but in the proportion expected given the rarity of very slowly rotating molecules present. Heterogeneous molecules are characterized by persistence and exchange times. Median exchange and persistence times of the molecules identified as heterogeneous relative to glycerol's structural relaxation time tau(alpha) are found to be tau(ex)/tau(alpha)=202 and tau(pers)/tau(alpha)=405, respectively. These results are discussed in the context of values of exchange times that have been determined in other experiments.

An experimental study of the (16)O(e,e'K(+))(Lambda)(16)N reaction has been performed at Jefferson Lab. A thin film of falling water was used as a target. This permitted a simultaneous measurement of the p(e,e'K(+))Lambda, Sigma(0) exclusive reactions and a precise calibration of the energy scale. A ground-state binding energy of 13.76+/-0.16 MeV was obtained for (Lambda)(16)N with better precision than previous measurements on the mirror hypernucleus (Lambda)(16)O. Precise energies have been determined for peaks arising from a Lambda in s and p orbits coupled to the p(1/2) and p(3/2) hole states of the (15)N core nucleus.

We quantitatively compare data obtained from imaging two-dimensional slices of three-dimensional unlabeled and fluorescently labeled collagen gels with confocal reflectance microscopy (CRM) and/or confocal fluorescence microscopy (CFM). Different network structures are obtained by assembling the gels over a range of concentrations at various temperatures. Comparison between CRM and CFM shows that the techniques are not equally sensitive to details of network structure, with CFM displaying higher fidelity in imaging fibers parallel to the optical axis. Comparison of CRM of plain and labeled collagen gels shows that labeling itself induces changes in gel structure, chiefly through inhibition of fibril bundling. Despite these differences, image analyses carried out on two-dimensional CFM and CRM slices of collagen gels reveal identical trends in structural parameters as a function of collagen concentration and gelation temperature. Fibril diameter approximated from either CRM or CFM is in good accord with that determined via electron microscopy. Two-dimensional CRM images are used to show that semiflexible polymer theory can relate network structural properties to elastic modulus successfully. For networks containing bundled fibrils, it is shown that average structural diameter, rather than fibril diameter, is the length scale that sets the magnitude of the gel elastic modulus.

Microcapsules fabricated by layer-by-layer self-assembly have unique physicochemical properties that make them attractive for drug delivery applications. This study chiefly investigated the biocompatibility of one of the most stable types of microcapsules, those composed of poly-(sodium 4-styrene sulfonate) [PSS] and poly-(allylamine hydrochloride) [PAH], with cells cultured on two-dimensional (2D) substrates and in three-dimensional (3D) matrices. C6 glioma and 3T3 fibroblast cell morphology was observed after 24h of co-culture with PSS/PAH microcapsules on a 2D substrate. Cells were also cultured with four other types of microcapsules, each composed of at least one naturally occurring polyelectrolyte. At microcapsule to cell ratios up to 100:1, it was found that PSS/PAH microcapsules do not affect number of viable cells more substantially than do the other microcapsules investigated. However, differences in number of viable cells were found as a function of microcapsule composition, and our results suggest particular biochemical interactions between cells and internalized microcapsules, rather than mechanical effects, are responsible for these differences. We then investigated the effects of PSS/PAH microcapsules on cells embedded in 3D collagen matrices, which more closely approximate the tumor environments in which microcapsules may be useful drug delivery agents. Matrix structure, cell invasion, and volumetric spheroid growth were investigated, and we show that these microcapsules have a negligible effect on cell invasion and tumor spheroid growth even at high concentration. Taken together, this work suggests that PSS/PAH microcapsules have sufficiently high biocompatibility with at least some cell lines for use as proof of principle drug delivery agents in in vitro studies.

In this work, the gelation of three-dimensional collagen and collagen/hyaluronan (HA) composites is studied by time sweep rheology and time lapse confocal reflectance microscopy (CRM). To investigate the complementary nature of these techniques, first collagen gel formation is investigated at concentrations of 0.5, 1.0, and 1.5 mg/mL at 37 degrees C and 32 degrees C. The following parameters are used to describe the self-assembly process in all gels: the crossover time (t(c)), the slope of the growth phase (k(g)), and the arrest time (t(a)). The first two measures are determined by rheology, and the third by CRM. A frequency-independent rheological measure of gelation, t(g), is also measured at 37 degrees C. However, this quantity cannot be straightforwardly determined for gels formed at 32 degrees C, indicating that percolation theory does not fully capture the dynamics of collagen network formation. The effects of collagen concentration and gelation temperature on k(g), t(c), and t(a) as well as on the mechanical properties and structure of these gels both during gelation and at equilibrium are elucidated. Composite collagen/HA gels are also prepared, and their properties are monitored at equilibrium and during gelation at 37 degrees C and 32 degrees C. We show that addition of HA subtly alters mechanical properties and structure of these systems both during the gelation process and at equilibrium. This occurs in a temperature-dependent manner, with the ratio of HA deposited on collagen fibers versus that distributed homogeneously between fibers increasing with decreasing gelation temperature. In addition to providing information on collagen and collagen/HA structure and mechanical properties during gelation, this work shows new ways in which rheology and microscopy can be used complementarily to reveal details of gelation processes.

Single molecule fluorescence experiments, with their associated low signals, require very low background fluorescence in the sample. Even high purity liquids will often possess large numbers of fluorescent impurities that are difficult to completely remove through standard purification techniques such as distillation and recrystallization. We have constructed a simple setup in which such impurities can be photobleached before final sample preparation. The instrument consists of high power light emitting diodes, and it delivers almost 10 W of light to the sample without the heating associated with more conventional light sources or the cost and safety concerns associated with a high power laser.

In this work, a cellular Potts model based on the differential adhesion hypothesis is employed to analyze the relative importance of select cell-cell and cell-extracellular matrix (ECM) contacts in glioma invasion. To perform these simulations, three types of cells and two ECM components are included. The inclusion of explicit ECM with an inhomogeneous fibrous component and a homogeneously dispersed afibrous component allows exploration of the importance of relative energies of cell-cell and cell-ECM contacts in a variety of environments relevant to in vitro and in vivo experimental investigations of glioma invasion. Simulations performed here focus chiefly on reproducing findings of in vitro experiments on glioma spheroids embedded in collagen I gels. For a given range and set ordering of energies associated with key cell-cell and cell-ECM interactions, our model qualitatively reproduces the dispersed glioma invasion patterns found for most glioma cell lines embedded as spheroids in collagen I gels of moderate concentration. In our model, we find that invasion is maximized at intermediate collagen concentrations, as occurs experimentally. This effect is seen more strongly in model gels composed of short collagen fibers than in those composed of long fibers, which retain significant connectivity even at low density. Additional simulations in aligned model matrices further elucidate how matrix structure dictates invasive patterns. Finally, simulations that allow invading cells to both dissolve and deposit ECM components demonstrate how Q-Potts models may be elaborated to allow active cell alteration of their surroundings. The model employed here provides a quantitative framework with which to bound the relative values of cell-cell and cell-ECM interactions and investigate how varying the magnitude and type of these interactions, as well as ECM structure, could potentially curtail glioma invasion.

The protons and neutrons in a nucleus can form strongly correlated nucleon pairs. Scattering experiments, in which a proton is knocked out of the nucleus with high-momentum transfer and high missing momentum, show that in carbon-12 the neutron-proton pairs are nearly 20 times as prevalent as proton-proton pairs and, by inference, neutron-neutron pairs. This difference between the types of pairs is due to the nature of the strong force and has implications for understanding cold dense nuclear systems such as neutron stars.

We report the observation of imaging beyond the diffraction limit due to bound surface states in negative refraction photonic crystals. We achieve an effective negative index figure of merit [-Re(n)/Im(n)] of at least 380, approximately 125x improvement over recent efforts in the near-infrared range, with a 0.4 THz bandwidth. Supported by numerical and theoretical analyses, the observed near-field resolution is 0.47lambda, clearly smaller than the diffraction limit of 0.61lambda. Importantly, we show this subdiffraction imaging is due to the resonant excitation of surface slab modes.

The present experiment exploits the interference between the deeply virtual Compton scattering (DVCS) and the Bethe-Heitler processes to extract the imaginary part of DVCS amplitudes on the neutron and on the deuteron from the helicity-dependent D(e,e'gamma)X cross section measured at Q2=1.9 GeV2 and xB=0.36. We extract a linear combination of generalized parton distributions (GPDs) particularly sensitive to E_{q}, the least constrained GPD. A model dependent constraint on the contribution of the up and down quarks to the nucleon spin is deduced.

An experiment measuring electroproduction of hypernuclei has been performed in hall A at Jefferson Lab on a 12C target. In order to increase counting rates and provide unambiguous kaon identification two superconducting septum magnets and a ring imaging Cherenkov detector were added to the hall A standard equipment. An unprecedented energy resolution of less than 700 keV FWHM has been achieved. Thus, the observed (Lambda)(12)B spectrum shows for the first time identifiable strength in the core-excited region between the ground-state s-wave Lambda peak and the 11 MeV p-wave Lambda peak.

We measured the angular dependence of the three recoil-proton polarization components in two-body photodisintegration of the deuteron at a photon energy of 2 GeV. These new data provide a benchmark for calculations based on quantum chromodynamics. Two of the five existing models have made predictions of polarization observables. Both explain the longitudinal polarization transfer satisfactorily. Transverse polarizations are not well described, but suggest isovector dominance.

We investigate by molecular dynamics simulations the validity of the frequency-dependent Stokes-Einstein (SE) relation in supercooled liquids at different temperatures. The results indicate that the SE relation holds at intermediate frequencies that correspond to the beta -relaxation and the onset of the alpha -relaxation regimes. Large deviations, which increase as the temperature decreases, are observed at frequencies well below the frequency at which the non-Gaussian parameter alpha2 is maximum. We argue that the breakdown of the SE relation in supercooled liquids arises from underestimation of the diffusion coefficient due to neglect of correlated motions.

Thrombocytopenia commonly occurs in hospitalized patients, particularly critically ill patients. We present an exemplifying case of severe heparin-induced thrombocytopenia (HIT) in an effort to solidify its high priority in the differential diagnosis of thrombocytopenia. A 75-year-old female underwent cardiac surgery with intraaortic balloon pump (IABP) placement. A platelet count drop to 25 x 10(9)/L by the third postoperative day was attributed to the IABP, which was removed. Her thrombocytopenia remained refractory to multiple platelet transfusions over several days. Right hand cyanosis then developed, attributed to a right radial arterial catheter, which was removed. All toes and fingers then showed severe ischemic changes. Ten days after the initial platelet count drop, a critical care specialist new to the treating team suspected HIT. Heparin exposure was stopped and argatroban was initiated. A HIT antibody test was subsequently strongly positive. The patients thrombocytopenia gradually resolved. No additional thromboses occurred during a 27-day intensive care unit stay. This case underscores the need for vigilance in suspecting HIT in patients with thrombocytopenia and recent heparin exposure. To avoid catastrophic outcomes in such patients, heparin should be stopped and alternative anticoagulation should be initiated, at least until HIT is excluded.

The authors present results from molecular dynamics simulations on the effect of smooth and rough probes on the dynamics of a supercooled Lennard-Jones (LJ) mixture. The probe diameter was systematically varied from one to seven times the diameter of the large particles of the LJ mixture. Mean square displacements show that in the presence of a large smooth probe the supercooled liquid speeds up, while in the presence of a large rough probe, the supercooled liquid slows down. Non-Gaussian parameters indicate that with both smooth and rough probes, the heterogeneity of the supercooled system increases. From the analysis of local Debye-Waller factors, it is evident that the change in the dynamics of the LJ system is heterogeneous, with the largest perturbations close to the probes. Large smooth and rough probes appear to set up heterogeneities in these supercooled systems that would otherwise not occur, and these heterogeneities persist for long times.

A straightforward technique to align thin collagen gels is presented. This technique requires only collagen solution, surface-modified magnetic beads, a small magnet, and an incubator. As such, this is the only collagen alignment technique that requires no specialized equipment. The collagen gels are imaged with confocal reflectance microscopy, and degree of alignment is quantitatively assessed using image analysis techniques that allow for identification of fiber position and angular distribution. A series of experiments shows that magnetic beads coated with streptavidin lead to the most highly aligned gels. Rheology and microscopy experiments suggest that alignment results from bead coupling to, and entrainment and entrapment in, collagen fibrils during their assembly into fibers that form a sample-spanning gel. The timescales of gelation and bead motion to the poles of the external magnet must be similar to effect good alignment over large areas with this technique. It is also demonstrated that alignment can be attained in both plain and cell-bearing gels that are several millimeters thick.

We report new measurements of the parity-violating asymmetry A(PV) in elastic scattering of 3 GeV electrons off hydrogen and 4He targets with approximately 6.0 degrees . The 4He result is A(PV)=(+6.40+/-0.23(stat)+/-0.12(syst))x10(-6). The hydrogen result is A(PV)=(-1.58+/-0.12(stat)+/-0.04(syst))x10(-6). These results significantly improve constraints on the electric and magnetic strange form factors G(E)(s) and G(M)(s). We extract G(E)(s)=0.002+/-0.014+/-0.007 at =0.077 GeV2, and G(E)(s)+0.09G(M)(s)=0.007+/-0.011+/-0.006 at =0.109 GeV2, providing new limits on the role of strange quarks in the nucleon charge and magnetization distributions.

We present the first measurements of the e[over -->]p-->epgamma cross section in the deeply virtual Compton scattering (DVCS) regime and the valence quark region. The Q(2) dependence (from 1.5 to 2.3 GeV(2)) of the helicity-dependent cross section indicates the twist-2 dominance of DVCS, proving that generalized parton distributions (GPDs) are accessible to experiment at moderate Q(2). The helicity-independent cross section is also measured at Q(2)=2.3 GeV(2). We present the first model-independent measurement of linear combinations of GPDs and GPD integrals up to the twist-3 approximation.

Coherent anti-Stokes Raman scattering microscopy is performed on glassy systems of poly(methylmethacrylate) colloidal particles in density- and refractive-index-matched solvents. Samples are prepared with varying amounts of linear polystyrene, which induces a depletion driven attraction between the nearly hard-sphere particles. Images collected over several hours confirm the existence of a reentrant glass transition. The images also reveal that the dynamics of repulsive and attractive glasses are qualitatively different. Colloidal particles in repulsive glasses exhibit cage rattling and escape, while those in attractive glasses are nearly static while caged but exhibit large displacements upon (infrequent) cage escape.

We have measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from 4He at an average scattering angle = 5.7 degrees and a four-momentum transfer Q2 = 0.091 GeV2 . From these data, for the first time, the strange electric form factor of the nucleon G(E)s can be isolated. The measured asymmetry of A(PV) = (6.72 +/- 0.84(stat) +/- 0.21(syst) x 10(-6) yields a value of G(E)s = -0.038 +/- 0.042(stat) +/- 0.010(syst), consistent with zero.

Colloid-polymer mixtures can undergo spinodal decomposition into colloid-rich and colloid-poor regions. Gelation results when interconnected colloid-rich regions solidify. We show that this occurs when these regions undergo a glass transition, leading to dynamic arrest of the spinodal decomposition. The characteristic length scale of the gel decreases with increasing quench depth, and the nonergodicity parameter exhibits a pronounced dependence on scattering vector. Mode coupling theory gives a good description of the dynamics, provided we use the full static structure as input.

We report on a precision measurement of the parity-violating asymmetry in fixed target electron-electron (Møller) scattering: A(PV) = [-131 +/- 14(stat) +/- 10(syst)] x 10(-9), leading to the determination of the weak mixing angle sin2(thetaW(eff) = 0.2397 +/- 0.0010(stat) +/- 0.0008(syst), evaluated at Q2 = 0.026 GeV2. Combining this result with the measurements of sin2(thetaW(eff) at the Z0 pole, the running of the weak mixing angle is observed with over 6sigma significance. The measurement sets constraints on new physics effects at the TeV scale.

We study the growth and invasion of glioblastoma multiforme (GBM) in three-dimensional collagen I matrices of varying collagen concentration. Phase-contrast microscopy studies of the entire GBM system show that invasiveness at early times is limited by available collagen fibers. At early times, high collagen concentration correlates with more effective invasion. Conversely, high collagen concentration correlates with inhibition in the growth of the central portion of GBM, the multicellular tumor spheroid. Analysis of confocal reflectance images of the collagen matrices quantifies how the collagen matrices differ as a function of concentration. Studying invasion on the length scale of individual invading cells with a combination of confocal and coherent anti-Stokes Raman scattering microscopy reveals that the invasive GBM cells rely heavily on cell-matrix interactions during invasion and remodeling.

We report a measurement of the parity-violating asymmetry in fixed target electron-electron (Møller) scattering: A(PV)=[-175+/-30(stat)+/-20(syst)] x 10(-9). This first direct observation of parity nonconservation in Møller scattering leads to a measurement of the electron's weak charge at low energy Q(e)(W)=-0.053+/-0.011. This is consistent with the standard model expectation at the current level of precision: sin((2)theta(W)(M(Z))((-)MS)=0.2293+/-0.0024(stat)+/-0.0016(syst)+/-0.0006(theory).

Purpose: Secure venous access with multiple lumens is necessary for the care of allogeneic hematopoietic stem cell transplant (HSCT) recipients. The outcomes associated with simultaneous bilateral tunneled internal jugular infusion catheter placement in the HSCT recipient population were investigated in an attempt to determine whether simultaneous introduction of these catheters compounds or magnifies the risks (infection, venous thrombosis) associated with tunneled catheters., Materials and Methods: Patients undergoing HSCT and receiving bilateral tunneled infusion catheters in a single procedure were identified using a quality assurance data base. Medical records for the duration of catheterization were reviewed; 43 patients were included in the study (mean age, 42 years; range, 22-56). Diagnoses included acute lymphocytic leukemia (n = 4), acute myelogenous leukemia (n = 8), aplastic anemia (n = 2), chronic myelogenous leukemia (n = 17), chronic lymphocytic leukemia (n = 1), Hodgkin lymphoma (n = 1), myelodysplasia (n = 4), myelofibrosis (n = 2), and non-Hodgkin lymphoma (n = 4). Cox proportional hazards regression analysis was performed to determine differences in infection rates between dual- and triple-lumen catheters., Results: Forty-three pairs of catheters were placed. All met venous access needs for HSCT recipient care. Complete follow-up was achieved for 77 of 87 (89%) catheters. The overall infection rate was 0.25 per 100 catheter-days. The rate was 0.19 and 0.33 for dual- and triple-lumen catheters, respectively (P =.15). Mechanical failure did not differ between catheter types (dual: 0.14 episodes per 100 days, triple: 0.05 per 100 days, P =.2)., Conclusions: Bilateral multilumen tunneled infusion catheter placement in a single procedure using imaging guidance is safe with acceptable outcomes and meets venous access needs for HSCT. There is a trend toward higher infection rates, with more lumens and more mechanical failure with dual-lumen catheters.

Actively phase-locked heterodyne-detected fifth-order nonresonant Raman scattering from room temperature CS2 has been measured. The experimental signals have similar magnitudes, shapes, and sign changes as calculated responses obtained via molecular dynamics simulations [S. Saito and I. Ohmine, Phys. Rev. Lett. 88, 207401 (2002)]. The measured signals contain sign changes that appear to be associated with the coupling of rotational motions both to each other and to translational motions.

Today, the world of critical care medicine has given us the capabilities to accomplish things that were only dreamed of a few decades ago. When combined with the increasing importance of patient autonomy and economics in healthcare, these new capabilities have caused conflicts about what is too little, and what is too much. Medical futility becomes an issue whenever these conflicts arise. Understanding how to deal with issues surrounding futility begins with defining it. A firm definition is not possible or desirable, but revolves around the probability of being able to achieve a patient's goal with modern medicine. Establishing this understanding between the patient and their family (team), and the healthcare team, is dependent on trust between the two. It must be recognized that there are many reasons for families to not trust healthcare professionals and that these reasons need to be explored and dealt with. Sometimes conflicts regarding predictions and economics need to be addressed. Once trust is established a goal for a course of medical treatment should be discussed from the patient's perspective. This discussion should involve the physician's best judgement as to the chances of achieving this goal, and what type of discomfort or indignity, if any, the patient may experience. Only after these have been clearly discussed can decisions regarding medical futility be made. To date, the U. S. Courts have refused to grant physicians and hospitals the power to override the opinions of family members on matters of futility. However, with time, a consensus of public opinion should influence decisions regarding medical futility.

The influence of endogenous angiotensin II on the hemodynamic responses to electrical stimulation of the sympathetic outflow was assessed in pithed male normotensive Wistar rats fitted with aortic flow probes for continuous measurement of cardiac output (CO). The frequency-related increments (0.25-4.0 Hz) in blood pressure (BP) and total peripheral resistance (TPR) were significantly attenuated by treating animals with the angiotensin converting enzyme inhibitor captopril (5 mg/kg i.v.) or the angiotensin II receptor antagonist saralasin (10 micrograms/kg/min i.v.). However, the increments in CO and heart rate during neural stimulation were unaffected by blockade of the renin-angiotensin system. After captopril treatment, infusion of angiotensin II (40 ng/kg/min i.v.) to replace the loss of endogenous angiotensin II restored stimulation-induced TPR and BP responses toward precaptopril levels; CO and heart rate responses to stimulation were not altered. The hemodynamic responses to exogenous norepinephrine were affected by inhibition of the renin-angiotensin system with captopril and saralasin in a manner analogous to the neurally mediated responses. The results obtained with nerve stimulation and norepinephrine indicate that endogenous angiotensin II selectively interacted with sympathetic neural control of vascular resistance, whereas cardiac responsiveness to noradrenergic neurons was not altered. Moreover, in the absence of nerve stimulation, the antagonism of the renin-angiotensin system lowered base-line BP by reducing CO without measurably affecting TPR. Infusion of angiotensin II reversed these effects and restored BP toward precaptopril levels by increasing CO without measurably affecting TPR.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma and tissue (cardiac, vascular, renal, and adrenal) catecholamine concentrations were measured in pithed male Wistar rats maintained on low (10 mEq/kg diet), basal (115 mEq/kg diet), or high (1200 mEq/kg diet) sodium test diets for five weeks. Significant differences in catecholamine disposition were observed only in response to sodium restriction; responses to basal and high sodium intakes were consistently similar. Baseline plasma catecholamine levels (p less than 0.01) as well as those in response to stimulation of the entire sympathetic outflow at 4 Hz were markedly enhanced in low sodium rats (p less than 0.001). The facilitation of stimulation-induced increments in plasma norepinephrine levels in low sodium rats may be related to the finding that norepinephrine content was also elevated in noradrenergically innervated tissues (atria, ventricles, mesenteric artery, and kidneys) (p less than 0.01). Adrenal catecholamine levels, however, were not affected by dietary sodium restriction. Despite the peripheral catecholamine changes associated with a low sodium intake, pressor and tachycardic responses to sympathetic nerve stimulation were similar across dietary sodium groups. The results indicate that a low sodium intake enhances plasma and tissue catecholamine levels, adaptations that may be important in the maintenance of sympathetic responsiveness.