Abstract 4592: In vivo efficacy evaluation of anti-human VEGFR2 antibodies in humanized B-hVEGFR2 mice

Angiogenesis, vascular development, vascular permeability, and embryonic hematopoiesis is partly regulated by VEGF binding to VEGFR2, which forms receptor dimers and activates downstream signaling pathways. In addition to developmental cues, VEGFR2 is also associated with disease progression for psoriasis, rheumatoid arthritis, diabetic retinopathy, and more significantly, tumor growth and drug resistance. Given this, inhibition of VEGFR2 signaling is actively being studied, and multiple VEGFR2 inhibitors have entered various phases of clinical studies and have shown promising results. To evaluate in vivo efficacy of anti-human VEGFR2 antibodies, we generated a human VEGFR2 knock-in (B-hVEGFR2) mouse model by replacing the murine Vegfr2 extracellular domain sequence with the corresponding human sequence. We validated human VEGFR2 gene and protein expression in B-hVEGFR2 mice by RT-PCR and flow cytometry, respectively. Furthermore, we observed an anti-tumor effect with anti-human VEGFR2 antibodies in homozygous B-hVEGFR2 mice subcutaneously implanted with MC38 colon cancer cells. Taken together, we established a novel preclinical B-hVEGFR2 mouse model for evaluation of VEGFR2-targeted immunotherapy.

Citation Format: Lei Zhao, Chengzhang Shang, Rebecca Soto, Chonghui Liu, Zhaoxue Yu. In vivo efficacy evaluation of anti-human VEGFR2 antibodies in humanized B-hVEGFR2 mice. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4592.

Abstract 1649: Humanized PVRIG mice: A novel tool for evaluating anti-PVRIG immunotherapies

The use of humanized mouse models provides a promising platform for preclinical studies aimed at developing novel immunotherapies. While current checkpoint inhibitors have improved patient outcomes, combination therapy targeting additional checkpoint receptors may heighten the immune response. Specifically, previous reports have shown that high expression of the immune checkpoint poliovirus receptor-related immunoglobulin domain-containing (PVRIG) protein leads to T-cell exhaustion. Furthermore, in vitro blockade of human PVRIG enabled T-cell activation. To explore the translational potential of inhibiting PVRIG, we evaluated the efficacy of PVRIG antibodies by generating a humanized B-hPVRIG mouse model. In this model, the mouse Pvrig gene was replaced by the human counterpart, and expression of the human PVRIG protein was confirmed in homozygous B-hPVRIG mice. Additionally, flow cytometry analysis showed similar distribution of T-cell subtypes within the blood, spleen, and lymph nodes of B-hPVRIG mice compared to wild-type C57BL/6. Lastly, our in vivo efficacy studies showed that homozygous B-hPVRIG mice that were subcutaneously implanted with murine colon cancer (MC38) cells and treated with 30 mg/kg of the human PVRIG antibody, reached a tumor growth inhibition (TGI) of approximately 40%. This data suggests that human PVRIG antibodies significantly inhibit tumor growth in homozygous B-hPVRIG mice. Altogether, our humanized B-hPVRIG mouse model is an effective tool for in vivo efficacy studies aimed at the development of novel PVRIG immunotherapies.

Citation Format: Yifu Zhang, Jiawei Yao, Rebecca Soto, Chonghui Liu, Qingcong Lin. Humanized PVRIG mice: A novel tool for evaluating anti-PVRIG immunotherapies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1649.

Abstract 1648: Evaluation of therapeutic drug candidates using a novel humanized B-hCSF1/hCSF1R mouse model

An often rate-limiting step for cancer immunotherapy is drug development. The generation of humanized mouse models can be used to assess the clinical utility of new drugs earlier in the discovery process. Tumor-associated macrophages (TAMs) represent an emerging therapeutic target, specifically high expression of the colony-stimulating factor 1 receptor (CSF1R) protein on tumors and TAMs facilitate a tumor permissive environment. Previous reports have demonstrated that blockade of the CSF1/CSF1R pathway reduced and reprogrammed intra-tumoral CSF1R+ TAMs, altogether alleviating immune suppression. To evaluate preclinical efficacy and toxicity of CSF1R targeted therapeutic candidates, Biocytogen has successfully generated a double humanized B-hCSF1/hCSF1R mouse model. The full-length encoding sequence of mouse Csf1 and the extracellular domain of Csf1r were replaced by human CSF1 and CSF1R genes, respectively. Evaluation of CSF1 and CSF1R protein expression in homozygous B-hCSF1/hCSF1R mice (H/H) was confirmed by ELISA and flow cytometry analysis. We next performed an in vivo efficacy screening study using genetically modified hCSF1 or wild-type MC38 cells inoculated into B-hCSF1/hCSF1R (H/H) mice and observed that anti-human CSF1R antibodies or combination therapy of anti-mouse PD-L1 and anti-human CSF1R antibodies were effective in controlling tumor growth. Our combined studies illustrate that Biocytogen’s novel B-hCSF1/hCSF1R mice offer a promising model for in vivo validation of CSF1 and CSF1R antibody therapeutics.

Citation Format: Ruili Lyu, Shujin Zhang, Rebecca Soto, Suman Zhao, Chonghui Liu, Luke (Zhaoxue) Yu. Evaluation of therapeutic drug candidates using a novel humanized B-hCSF1/hCSF1R mouse model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1648.

RenMice™ HiTS platform enables identification of novel therapeutic antibodies

Despite an increase in approved cancer-targeting antibody drugs over the last decade, the process of identifying novel therapeutic antibodies is routinely hampered by limitations in the discovery process. Such barriers include immune tolerance of highly homologous genes, antibody sequence humanization, clone selection and models for drug efficacy/safety evaluation. To overcome these challenges and increase the diversity of antibody paratopes and sequences that recognize functional epitopes, we developed the RenMice™ HiTS (Hyperimmune Target Specific) Platform, which consists of chromosome engineered mice with fully human immunoglobulin variable domains replacing the mouse loci, each with a specific target gene knocked out. Immunization of target-specific RenMice™ generates a sizeable diversity of antibodies, including those that recognize conserved regions between the antigen and the endogenous proteins of the immunized species. The platform is ideal for challenging targets, such as proteins with high homology across species, or multi-pass transmembrane proteins, such as GPCRs/ion channels, and can be used to generate antibodies that cross-react with human, monkey, dog, and mouse targets using a hybrid immunization strategy with both human and mouse/dog antigen. Generation of these species cross-reactive antibodies can be used for high-throughput in vivo efficacy screening in wild-type mice, and the preliminary response and toxicity can be assessed in dogs. Altogether, the RenMice™ HiTS platform facilitates the generation of antibodies that recognize novel epitopes and challenging targets while simultaneously allowing for a streamlined and successful preclinical phase based on in vivo efficacy and safety.

AT III Barcelona: A Familial Quantitative-Qualitative AT III Deficiency

A quantitative and qualitative deficiency of antithrombin III (AT III) was found in four members of a Spanish family with thrombotic tendency. In all affected members, levels of AT III antigen and activity (heparin cofactor activity) were reduced to 50% of the normal range. When crossed immunoelectrophoresis (CIE) was performed in the presence of heparin, an abnormal slow-moving peak was found. Crossed immunoelectrofocusing (CIEF) from normal and affected individuals showed that normal AT III migrated between pH 4.9–5.3 while the AT III under study was asymetrically distributed between two pH ranges: 4.9–5.3 and 4.6–4.8. Affinity adsorption of affected members’ plasma to heparin-sepharose beads revealed one population of AT III in the supernatant corresponding to the abnormal AT III, devoid of heparin cofactor activity and showing a peak between pH range: 4.6–4.8 in CIEF.

Our data supports the view that a quantitative-qualitative deficiency was present in the heterozygous state in all the affected family members. Both normal and abnormal ATIII were present in plasma of the affected individuals. This abnormal ATIII was characterized by a lack of affinity for heparin. This familial ATIII deficiency was named ATIII Barcelona.

Catalytic activity dependence on morphological properties of acidic ion-exchange resins for the simultaneous ETBE and TAEE liquid-phase synthesis

Resin acid capacity and specific volume of the swollen polymer are the key properties that determine its catalytic activity.

Kinematics and Dynamics of a New 16 DOF Humanoid Biped Robot with Active Toe Joint

Humanoid biped robots are typically complex in design, having numerous Degrees-of-Freedom (DOF) due to the ambitious goal of mimicking the human gait. The paper proposes a new architecture for a biped robot with seven DOF per each leg and one DOF corresponding to the toe joint. Furthermore, this work presents close equations for the forward and inverse kinematics by dividing the walking gait into the Sagittal and Frontal planes. This paper explains the mathematical model of the dynamics equations for the legs into the Sagittal and Frontal planes by further applying the principle of Lagrangian dynamics. Finally, a control approach using a PD control law with gravity compensation was recurred in order to control the desired trajectories and finding the required torque by the joints. The paper contains several simulations and numerical examples to prove the analytical results, using SimMechanics of MATLAB toolbox and SolidWorks to verify the analytical results.

Erratum to: Antimicrobials: a global alliance for optimizing their rational use in intra-abdominal infections (AGORA)

[This corrects the article DOI: 10.1186/s13017-016-0089-y.].

Simulating the activation, contraction and movement of skeletal muscles using the bidomain model

A simulation of the muscle activation, contraction and movement is here presented. This system was developed based on the Bidomain mathematical model of the electrical propagation in muscles. This study shows an electrical stimuli input to a muscle and how this behave. The comparison between healthy subject and patient with muscle activation impairment is depicted, depending on whether the signal reaches a threshold. A 3D model of a bicep muscle and a forearm bone connected was constructed using OpenGL. This platform could be used for development of controllers for biomechatronic systems in future works. This kind of bioinspired model could be used for a better understanding of the neuromotor system.

Novel compliant actuator for wearable robotics applications

In the growing fields of wearable robotics, rehabilitation robotics, prosthetics, and walking robots, variable impedance and force actuators are being designed and implemented because of their ability to dynamically modulate the intrinsic viscoelastic properties such as stiffness and damping. This modulation is crucial to achieve an efficient and safe human-robot interaction that could lead to electronically generate useful emergent dynamical behaviors. In this work we propose a novel actuation system in which is implemented a control scheme based on equilibrium forces for an active joint capable to provide assistance/resistance as needed and also achieve minimal mechanical impedance when tracking the movement of the user limbs. The actuation system comprises a DC motor with a built in speed reducer, two force-sensing resistors (FSR), a mechanism which transmits to the FSRs the torque developed in the joint and a controller which regulate the amount of energy that is delivered to the DC motor. The proposed system showed more impedance reduction, by the effect of the controlled contact forces, compared with the ones in the reviewed literature.

Isotopic and hydrogeochemical characterization of high-altitude karst aquifers in complex geological settings. The Ordesa and Monte Perdido National Park (Northern Spain) case study

The Ordesa and Monte Perdido National Park, located in the Southern Pyrenees, constitutes the highest karst system in Western Europe. No previous studies regarding its geochemical and isotopic groundwater characterization are available in this area. This work presents the results of field and sampling campaigns carried out between July 2007 and September 2013. The groundwater presents high calcium bicarbonate contents due to the occurrence of upper Cretaceous and lower Paleocene-Eocene carbonate materials in the studied area. Other relevant processes include dissolution of anhydrite and/or gypsum and incongruent dissolution of Mg-limestone and dolomite. The water stable isotopes (δ(18)O, δ(2)H) show that the oceanic fronts from the Atlantic Ocean are responsible for the high levels of precipitation. In autumn, winter, and spring, a deuterium excess is found in the recharge water, which could be related to local atmospheric transport of low-altitude snow sublimation vapour and its later condensation on the snow surface at higher altitude, where recharge is mostly produced. The recharge zones are mainly between 2500m and 3200ma.s.l. The tritium content of the water suggests short groundwater transit times. The isotopic composition of dissolved sulphate points to the existence of regional fluxes mixed with local discharge in some of the springs. This work highlights the major role played by the altitude difference between the recharge and discharge zones in controlling the chemistry and the vertical variability of the isotopic composition in high-altitude karst aquifers.

Assessing carbon and nitrogen removal in a novel anoxic-aerobic cyanobacterial-bacterial photobioreactor configuration with enhanced biomass sedimentation

The carbon and nitrogen removal potential of an innovative anoxic-aerobic photobioreactor configuration operated with both internal and external recyclings was evaluated under different cyanobacterial-bacterial sludge residence times (9-31 days) during the treatment of wastewaters with low C/N ratios. Under optimal operating conditions, the two-stage photobioreactor was capable of providing organic carbon and nitrogen removals over 95% and 90%, respectively. The continuous biomass recycling from the settler resulted in the enrichment and predominance of rapidly-settling cyanobacterial-bacterial flocs and effluent suspended solid concentrations lower than 35 mg VSS L(-1). These flocs exhibited sedimentation rates of 0.28-0.42 m h(-1) but sludge volumetric indexes of 333-430 ml/g. The decoupling between the hydraulic retention time and sludge retention time mediated by the external recycling also avoided the washout of nitrifying bacteria and supported process operation at biomass concentrations of 1000-1500 mg VSS L(-1). The addition of additional NaHCO3 to the process overcame the CO2 limitation resulting from the intense competition for inorganic carbon between cyanobacteria and nitrifying bacteria in the photobioreactor, which supported the successful implementation of a nitrification-denitrification process. Unexpectedly, this nitrification-denitrification process occurred both simultaneously in the photobioreactor alone (as a result of the negligible dissolved oxygen concentrations) and sequentially in the two-stage anoxic-aerobic configuration with internal NO3(-)/NO2(-) recycling.

Casimir effect in swimmer suspensions

We show that the Casimir effect can emerge in microswimmer suspensions. In principle, two effects conspire against the development of Casimir effects in swimmer suspensions. First, at low Reynolds number, the force on any closed volume vanishes, but here the relevant effect is the drag by the flow produced by the swimmers, which can be finite. Second, the fluid velocity and the pressure are linear on the swimmer force dipoles, and averaging over the swimmer orientations would lead to a vanishing effect. However, being that the suspension is a discrete system, the noise terms of the coarse-grained equations depend on the density, which itself fluctuates, resulting in effective nonlinear dynamics. Applying the tools developed for other nonequilibrium systems to general coarse-grained equations for swimmer suspensions, the Casimir drag is computed on immersed objects, and it is found to depend on the correlation function between the rescaled density and dipolar density fields. By introducing a model correlation function with medium-range order, explicit expressions are obtained for the Casimir drag on a body. When the correlation length is much larger than the microscopic cutoff, the average drag is independent of the correlation length, with a range that depends only on the size of the immersed bodies.

Active temperature and velocity correlations produced by a swimmer suspension

The agitation produced in a fluid by a suspension of microswimmers in the low Reynolds number limit is studied. In this limit, swimmers are modeled as force dipoles all with equal strength. The agitation is characterized by the active temperature defined, as in kinetic theory, as the mean square velocity, and by the equal-time spatial correlations. Considering the phase in which the swimmers are homogeneously and isotropically distributed in the fluid, it is shown that the active temperature and velocity correlations depend on a single scalar correlation function of the dipole-dipole correlation function. By making a simple medium-range order model, in which the dipole-dipole correlation function is characterized by a single correlation length k(0)(-1) it is possible to make quantitative predictions. It is found that the active temperature depends on the system size, scaling as L(4-d) at large correlation lengths L<<k(0)(-1), while in the opposite limit it saturates in three dimensions and diverges logarithmically with the system size in two dimensions. In three dimensions the velocity correlations decay as 1/r for small correlation lengths, while at large correlation lengths the transverse correlation function becomes negative at maximum separation r~L/2, an effect that disappears as the system increases in size.

Dynamical approach to the Casimir effect

Casimir forces can appear between intrusions placed in different media driven by several fluctuation mechanisms, either in equilibrium or out of it. Herein, we develop a general formalism to obtain such forces from the dynamical equations of the fluctuating medium, the statistical properties of the driving noise, and the boundary conditions of the intrusions (which simulate the interaction between the intrusions and the medium). As a result, an explicit formula for the Casimir force over the intrusions is derived. This formalism contains the thermal Casimir effect as a particular limit and generalizes the study of the Casimir effect to such systems through their dynamical equations, with no appeal to their Hamiltonian, if any exists. In particular, we study the Casimir force between two infinite parallel plates with Dirichlet or Neumann boundary conditions, immersed in several media with finite correlation lengths (reaction-diffusion system, liquid crystals, and two coupled fields with non-Hermitian evolution equations). The driving Gaussian noises have vanishing or finite spatial or temporal correlation lengths; in the first case, equilibrium is reobtained and finite correlations produce nonequilibrium dynamics. The results obtained show that, generally, nonequilibrium dynamics leads to Casimir forces, whereas Casimir forces are obtained in equilibrium dynamics if the stress tensor is anisotropic.

Cutaneous facial sinus tract of dental origin

Cutaneous sinus tract on the head and neck area in a child may originate from dental disease. A high degree of clinical suspicion and complementary tests are often needed, as the diagnosis is usually not straight forward. Anatomical correlation is also useful in tracing the affected tooth or teeth. We present the case of a boy with a facial sinus tract that originated from periapical abscesses of maxillary molars.

Segregation induced by inelasticity in a vibrofluidized granular mixture

We investigate the segregation of a dense binary mixture of granular particles that only differ in their restitution coefficient. The mixture is vertically vibrated in the presence of gravity. We find a partial segregation of the species, where most dissipative particles submerge in the less dissipative ones. The segregation occurs even if one type of the particles is elastic. In order to have a complete description of the system, we study the structure of the fluid at microscopic scale (few particle diameters). The density and temperature pair distribution functions show strong enhancements with respect to the equilibrium ones at the same density. In particular, there is an increase in the probability that the more inelastic particles group together in pairs (microsegregation). Microscopically the segregation is buoyancy driven, by the appearance of a dense and cold region around the more inelastic particles.

[Major closed-space bleeding in patients on anticoagulation with acenocoumarol (TAO) or non-fractionned heparin(HS): a case-control study]

OBJECTIVE

To study the characteristics of major bleeding episodes into a closed space (BCS) of patients under chronic anticoagulation with either unfractionated heparin (HS) or coumadin (CM), and to determine the relationship, if any, of anticoagulation parameters (INR, PT and PTT) values at the time of bleeding with the episode. Finally, to determine risk factors for BCS and mortality in this population.

METHODS

Descriptive epidemiology of all cases of BCS seen in our hospital from 1995 to 2000 was obtained through the records and follow up visits of all patients under anticoagulation (HS or CM) during this period. A matched case-control study to determine risk factors for BCS was carried out. Cases and controls (1:2) were matched for age, gender, anticoagulant treatment and indication for anticoagulation. Cases were patients with a BCS while on anticoagulation (HS OR CM). Controls were patients under anticoagulation (HS or CM) without any bleeding episode during the study period that had anticoagulation parameter values (INR, PT or PTT) determined the very same day than the cases.

RESULTS

During the study period, 225 patients under anticoagulation were prospectively followed (75 cases and 150 controls) amid a total of 1650 patients under anticoagulation, for a 4.5% prevalence of BCS. Reasons for anticoagulation were: atrial fibrillation in 79 (35.3%), valvular heart disease in 59 (25.9%), pulmonary embolism or deep venous thrombosis in 48 (21.4%), dilated cardiomyopathy in 26 (11.6%) and vascular cerebral stroke in 13 (5.8%). Mean age of cases was 70.5 (SD 9.5) years and 41 (55%) were women, values similar to the controls. At the time of BCS 39 patients were on CM and 36 on HS. The mean INR value in the CM group at the time of the episode of BCS was 5.3 (SD + 7.5) while the PTT value was 2,25 (SD 0.95) in the HS group. There was previous antecedent bleeding in 24 (32%) cases. The most common sites of BCS were: muscular (40%), CNS (30.6%), retroperitoneal (18,6%) and articular (10.6%). Muscular (abdominal or thoracic wall) and retroperitoneal BCS were higher in the HS group (10 and 12 in the HS group versus 5 and 2 in the CM group, respectively; p < 0.0001). In contrast, CNS bleeding was commoner in the CM group (20 in CM versus 3 in HS; p < 0.001). BCS related mortality rate was 14.6% (11/75) and higher in the CM group (p = 0.04). Comparative analysis of the case-control study revealed that anticoagulation values in the CM group at the time of bleeding were within the recommended range in 38.5% of cases vs. 75% of the controls (p < 0.001). Also, there were significant differences in mean INR values between cases and controls (5.3 + 7.5 vs. 2.6 + 0.9, p < 0.029) In the HS group no differences were present in PTT values at the time of bleeding between cases and controls. In BCS cases, a previous bleeding episode was more frequent than in the control group (32% versus 1.3%, p < 0.001). Likewise, mortality was higher in cases (18,6%) than in controls (11.4%), p = 0.01.

CONCLUSIONS

In our study, the majority of patients under anticoagulation with CM had INR values above the recommended range at the time of BCS, in contrast with those on HS that had a PTT within the therapeutic range at the time of the BCS. A previous bleeding episode was an independent risk factor for a BCS episode. Bleeding was a late complication in the CM group and frequently in the CNS, while BCS was more frequently associated with muscular or retroperitoneal sites in the HS treated group. BCS related mortality was 15%. Close monitoring of INR is crucial to minimize bleeding complications.

Generalized Casimir forces in nonequilibrium systems

In the present work, we propose a method to determine fluctuation-induced forces in nonequilibrium systems. These forces are the analog of the well-known Casimir forces, which were originally introduced in quantum field theory and later extended to the area of critical phenomena. The procedure starts from the observation that many nonequilibrium systems exhibit fluctuations with macroscopic correlation lengths, and the associated structure factors strongly depend on the wave vectors for long wavelengths; in some cases the correlations become long range, and the structure factors show algebraic divergences in the long-wavelength limit. The introduction of external bodies into such systems in general modifies the spectrum of these fluctuations, changing the value of the renormalized pressure, which becomes inhomogeneous. This inhomogeneous pressure leads to the appearance of a net force between the external bodies. It is shown that the force can be obtained from the knowledge of the structure factor of the homogeneous system. The mechanism is illustrated by means of a simple example: a reaction-diffusion equation, where the correlation function has a characteristic length. The role of this length in the Casimir force is elucidated.

The influence of radiotherapy technique and dose on the patterns of failure for mesothelioma patients following extrapleural pneumonectomy

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Background: Extrapleural pneumonectomy (EPP) is an effective treatment of pleural mesothelioma(MPM). We present a comparison of moderate-dose hemithoracic radiation (MDRT) to high-dose hemithoracic radiation (HDRT) following EPP for MPM. Methods: From 7/94 to 4/04, 39 pts underwent EPP and adjuvant radiotherapy (RT) at DFCI/BWH. From 1994–2002, MDRT, 30Gy to the hemithorax with boosts to the mediastinum or chest wall to 40–54 Gy was given, generally with concurrent chemotherapy (CT). Beginning in 2003, HDRT to 54 Gy as published by Yajnik et al (IJROBP 03’) was given with sequential CT. Results: Thirty-nine pts received RT following EPP. Median age was 59 yrs (range 44–77). Histology was epithelial in 25 (64%) pts and mixed/sarcomatoid in 14 (46%) pts. Twenty-four pts were treated with MDRT. 19 pts received concurrent platinum-based CT with MDRT. Three received cyclophosphomide, adriamycin and cisplatin (CDDP) CT prior to radiotherapy and 2 did not receive CT. 14 pts (39%) were treated with HDRT. 10/14 received sequential CDDP/gemcitabine, 4 received CDDP/pemetrexed and 1 patient received intraoperative CDDP. The median follow-up was 20 mos (range, 6–73 mos). Overall survival (OS) was 19 mos (95% CI, 14–24 mos). The median times to distant failure (DF) and local recurrence (LR) were 20 mos (95% CI, 14–26 mos) and 26 mos (95% CI, 16–36 mos), respectively. No significant differences in outcome between the two radiotherapy regimens were seen. One patient died of radiation-induced liver disease, one of pneumonitis and one of an MI. Four pts who received HDRT are alive and NED. On univariate and multivariate analysis mixed histology was predictive of DF and OS (p < .006; p < .004). Neither RT technique nor type of CT were predictive of LF, DF, or OS. The patterns of failure are in the table below. Conclusions: HDRT appears to limit in field local failures as compared to MDRT. Distant failure remains a significant challenge, with half of the patients experiencing distant failure.

[Table: see text]

No significant financial relationships to disclose.

Fluctuation-induced casimir forces in granular fluids

We numerically investigate the behavior of driven noncohesive granular media and find that two fixed large intruder particles, immersed in a sea of small particles, experience, in addition to a short-range depletion force, a long-range repulsive force. The observed long-range interaction is fluctuation-induced and we propose a mechanism similar to the Casimir effect that generates it: The hydrodynamic fluctuations are geometrically confined between the intruders, producing an unbalanced renormalized pressure. An estimation based on computing the possible Fourier modes explains the repulsive force and is in qualitative agreement with the simulations.

van der Waals normal form for a one-dimensional hydrodynamic model

Phase separation in a fluidized granular system is studied. We consider a one-dimensional hydrodynamic model that mimics a two-dimensional fluidized granular system with a vibrating wall and without gravity, which exhibits a phase separation. Close to the critical point, by means of an adiabatic elimination of the temperature, we deduce the van der Waals normal form, which is the equation that describes the slow dynamics of the system and predicts the qualitative behavior in different regions of parameters. This allows us to understand the origin of the effective viscosity and the spatial saturation at the onset of the bifurcation. The hydrodynamic model and van der Waals normal form exhibit a behavior similar to the one observed in molecular dynamics simulations.

van der Waals-like transition in fluidized granular matter

A phase separation of fluidized granular matter is presented. Molecular dynamics simulations of a system of grains in two spatial dimensions, with a vibrating wall and without gravity, exhibit the appearance, coalescence, and disappearance of bubbles. By identifying the mechanism responsible for the phase separation, we show that the phenomenon is analogous to the spinodal decomposition of the gas-liquid transition of the van der Waals model. We have deduced a macroscopic model for the onset of phase separation which agrees quite well with molecular dynamics simulations.

[Mangrove characterization of Central America with remote sensors]

Satellite images were used to study the mangrove distribution patterns in two different climatic regions of Central America: Gulf of Fonseca in Honduras-El Salvador and Sierpe-Térraba in Costa Rica. The Gulf of Fonseca has higher temperature and solar radiation, and lower precipitation, which can explain the higher structural development and species mixing of the Sierpe-Térraba mangrove. In the latter the transition between species or between heights in the same species is clear. The automatic classification made by the Geographic Information System (IDRISI) fits well the field mangrove distribution, but it was necessary to regroup some subdivisions that represent the same land use as identified by transects and an aerial video. Mixed species and clouds produced less satisfactory results in Sierpe-Térraba indicating a need for better satellite image resolution.

Effect of pre- and post-partum feed supplementation on the productive and reproductive performance of grazing primiparous Brahman cows

This experiment studied the combined effect of pre- and post-calving feed supplementation on the productive and reproductive performance of primiparous Brahman cows. The animals were 4 years old (420 kg live weight) and pregnant, and grazed rotationally on Stargrass (Cynodon nlemfuensis) pastures. Supplementation was given before and after (T1, n = 15), only before (T2, n = 15) or only after (T3, n = 16) calving, and there was an unsupplemented control (T4, n = 16). The supplement (1.5 kg/animal per day, 13.4 MJ digestible energy/kg dry matter and 20% crude protein) was given for 45 days before and/or after calving. Changes in body weight and body condition score and the productive behaviour of the calves were similar (p > 0.05) among treatments. The concentration of urea in the plasma was low in the control group (T4) before and after calving. The animals in all the groups had a poor reproductive performance. The percentage of cows in oestrus was higher (p < 0.05) in T1 (73.3%) than in T3 (37.5%). The interval from calving to conception (148.7 +/- 53.7 days) and the pregnancy rate (48.5%) were similar (p > 0.05) among the treatments. The level of supplementation offered before and/or after calving did not improve the pregnancy rate.

Precollisional velocity correlations in a hard-disk fluid with dissipative collisions

Velocity correlations are studied in granular fluids, modeled by the inelastic hard sphere gas. Making a density expansion of the Bogoliubov-Born-Green-Kirkwood-Yvon hierarchy for the evolution of the reduced distributions, we predict the presence of precollisional velocity correlations. They are created by the propagation through correlated sequences of collisions (ring events) of the velocity correlations generated after dissipative collisions. The correlations have their origin in the dissipative character of collisions, being always present in granular fluids. The correlations, that manifest microscopically as an alignment of the velocities of a colliding pair produce modifications of collisional averages, in particular, the virial pressure. The pressure shows a reduction with respect to the elastic case as a consequence of the velocity alignment. Good qualitative agreement is obtained for the comparison of the numerical evaluations of the obtained analytical expressions and molecular dynamics results that showed evidence of precollisional velocity correlations [R. Soto and M. Mareschal, Phys. Rev. E 63, 041303 (2001)].

A double-blind, randomized comparison of low-dose rocuronium and atracurium in a desflurane anesthetic

STUDY OBJECTIVES

To compare the neuromuscular and hemodynamic effects of rocuronium and atracurium when administered during a desflurane-based anesthetic.

DESIGN

Randomized, double-blind clinical trial.

PATIENTS

51 adult ASA physical status I and II patients scheduled for general surgical operations.

SETTING

University-based NCI-designated cancer center.

INTERVENTIONS

Patients received either 0.45 mg/kg rocuronium (n = 28) or atracurium 0.5 mg/kg (n = 23). Induction of anesthesia was accomplished by 2 microg/kg fentanyl intravenously (IV) and 1.5 mg/kg propofol IV and maintained by a nitrous oxide/oxygen desflurane anesthetic.

MEASUREMENTS AND MAIN RESULTS

A neuromuscular monitor was used at the adductor pollicis to monitor and record twitch response to train-of-four electrical stimulation. Baseline heart rate (HR) and blood pressure (BP) were measured and again at 2, 5, 10, and 15 minutes after muscle relaxant administration. Patients in the rocuronium group were found to have shorter times to 80%T(1)depression (109 +/- 53 vs. 135 +/- 47 sec), although those differences did not reach statistical significance (p = 0.07). Percent of the first twitch (T(1) ) was significantly lower in the patients receiving rocuronium at 60 seconds (53 +/- 24 vs. 73 +/- 27 sec; p = 0.006) and 90 seconds (25 +/- 22 vs. 47 +/- 29 sec; p = 0.003) than in the patients receiving atracurium. Duration was shorter in rocuronium-treated patients (25% T(1) recovery = 32 +/- 12 vs. 54 +/- 14 min; p < 0.001) than the patients receiving atracurium. Intubation scores were better at 60 seconds after muscle relaxant administration in the rocuronium group. No significant differences in HR or BP were seen between the patients in the two groups.

CONCLUSIONS

Rocuronium at a dose of 0.45 mg/kg possesses a fairly rapid onset of neuromuscular blockade and has short:intermediate duration of action when used with a desflurane anesthetic. This quality makes it a desirable drug for operations of relatively short duration. Rocuronium at a dose of 0.45 mg/kg has a faster onset and shorter duration than atracurium, at 0.5 mg/kg, when used with a desflurane anesthetic.

Statistical mechanics of fluidized granular media: short-range velocity correlations

A statistical mechanical study of fluidized granular media is presented. Using a special energy injection mechanism, homogeneous fluidized stationary states are obtained. Molecular dynamics simulations and theoretical analysis of the inelastic hard-disk model show that there is a large asymmetry in the two-particle distribution function between pairs that approach and separate. Large velocity correlations appear in the postcollisional states due to the dissipative character of the collision rule. These correlations can be well-characterized by a state dependent pair correlation function at contact. It is also found that velocity correlations are present for pairs that are about to collide. Particles arrive at collisions with a higher probability that their velocities are parallel rather than antiparallel. These dynamical correlations lead to a decrease of the pressure and of the collision frequency as compared to their Enskog values. A phenomenological modified equation of state is presented.

Prevalence and intensity of infections of Ascaris lumbricoides and Trichuris trichiura and associated socio-demographic variables in four rural Honduran communities

Between January and March 1998, a cross-sectional survey was carried out in four rural communities in Honduras, Central America. We examined the prevalence and intensity of Ascaris lumbricoides and Trichuris trichiura infections among 240 fecal specimens, and the association between selected socio-demographic variables and infection for 62 households. The overall prevalence of A. lumbricoides and T. trichiura was 45% (95% CI 39.0-51.9) and 38% (95% CI 31.8-44.4) respectively. The most intense infections for Ascaris and Trichuris were found in children aged 2-12 years old. By univariate analysis variables associated with infections of A. lumbricoides were: number of children 2-5 years old (p=0.001), level of formal education of respondents (p=0.01), reported site of defecation of children in households (p=0.02), households with children who had a recent history of diarrhea (p=0.002), and the location of households (p=0.03). Variables associated with both A. lumbricoides and T. trichiura infection included: number of children 6-14 years old (p=0.01, p=0.04, respectively), ownership of a latrine (p=0.04, p=0.03, respectively) and coinfection with either helminth (p=0.001, p=0.001, respectively). By multivariate analysis the number of children 2-5 years living in the household, (p=0.01, odds ratio (OR)=22.2), children with a recent history of diarrhea (p=0.0, OR=39.8), and infection of household members with T. trichiura (p=0.02, OR=16.0) were associated with A. lumbricoides infection. The number of children 6-14 years old in the household was associated with both A. lumbricoides and T. trichiura infection (p=0.04, p=0.01, OR=19.2, OR=5.2, respectively).

Nonlinear analysis of the shearing instability in granular gases

It is known that a finite-size homogeneous granular fluid develops a hydrodynamiclike instability when dissipation crosses a threshold value. This instability is analyzed in terms of modified hydrodynamic equations: first, a source term is added to the energy equation which accounts for the energy dissipation at collisions and the phenomenological Fourier law is generalized according to previous results. Second, a rescaled time formalism is introduced that maps the homogeneous cooling state into a nonequilibrium steady state. A nonlinear stability analysis of the resulting equations is done which predicts the appearance of flow patterns. A stable modulation of density and temperature is produced that does not lead to clustering. Also a global decrease of the temperature is obtained, giving rise to a decrease of the collision frequency and dissipation rate. Good agreement with molecular dynamics simulations of inelastic hard disks is found for low dissipation.

Hydrodynamic theory for granular gases

A granular gas subjected to a permanent injection of energy is described by means of hydrodynamic equations derived from a moment expansion method. The method uses as reference function not a Maxwellian distribution f(M) but a distribution f(0)=Phif(M), such that Phi adds a fourth cumulant kappa to the velocity distribution. The formalism is applied to a stationary conductive case showing that the theory fits extraordinarily well the results coming from our Newtonian molecular dynamic simulations once we determine kappa as a function of the inelasticity of the particle-particle collisions. The shape of kappa is independent of the size N of the system.

[Hepatitis C virus and resulting diseases]

In 1989, the main agent causing non A non B hepatitis was identified as a RNA virus of the flavivirus family, with several serotypes, and was denominated virus C. At the present moment, the knowledge about the infection features and diseases that it causes has expanded thanks to the availability of reliable laboratory techniques to detect the antibody and the virus. The prevalence of infection and the frequency of serotypes varies in different regions of the world. Chile is a country with a low prevalence. The detection of infected blood in blood banks has reduced the spreading of the disease. Other means of infection such as the use of intravenous drugs, hemodialysis and transplantation have acquired greater importance. Sexual, maternal and familial transmission is exceptional. Infected people develop an acute hepatitis, generally asymptomatic. Eighty percent remain with a chronic hepatic disease, that can be mild or progressive, evolving to cirrhosis or hepatic carcinoma. Chronic hepatitis, closely resembling an autoimmune disease, can be caused by the virus. Alcohol intake increases viral activity causing severe hepatic diseases, refractory to treatments. Several non hepatic diseases are associated to hepatitis C virus infection such as essential mixed cryoglobulinemia, mesangiocapillary glomerulonephritis, porphyria cutanea tarda, dysglobulinemias and probably type 2 diabetes mellitus. The only available treatment is interferon, that is successful in a minority of patients, frequently causing a transient improvement. The use of Ribaravine associated to interferon improve the effectiveness of therapy. Liver transplantation is the only therapy for severe hepatic disease. The use of new antiviral drugs should improve the prognosis of the disease.