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A non-invasive, in-situ calibration method for Total Internal Reflection Microscopy (TIRM) based on optical tweezing is presented which greatly expands the capabilities of this technique. We show that by making only simple modifications to the basic TIRM sensing setup and procedure, a probe particle's absolute position relative to a dielectric interface may be known with better than 10 nm precision out to a distance greater than 1 $\mu$m from the surface. This represents an approximate 10x improvement in error and 3x improvement in measurement range over conventional TIRM methods. The technique's advantage is in the direct measurement of the probe particle's scattering intensity vs. height profile in-situ, rather than relying on calculations or inexact system analogs for calibration. To demonstrate the improved versatility of the TIRM method in terms of tunability, precision, and range, we show our results for the hindered near-wall diffusion coefficient for a spherical dielectric particle., Comment: 10 pages. Submitted for peer review 8/20/2014

Assessing validity and reliability of end points used in docosahexanoic and arachidonic acids (DHA and ARA) infant formula supplementation trials as an example for addressing the impact of end-point selection and critical need for well-defined, reliable and validated clinical outcome assessments for neurocognitive assessment in neonates and infants. We searched eight electronic databases and reviewed all randomized, controlled human trials using DHA/ARA supplements with neurodevelopment clinical outcomes. We systematically evaluated the validity and reliability of end-point measures based on the criteria for studying nutritional additives recommended by the Institute of Medicine, criteria described in the Food and Drug Administration guidance for clinical outcome assessment, development and literature review. We identified 29 articles that met the selection criteria. The end points that were used for neurodevelopment measures in 23 out of 29 original short-term studies included the Bayley Scale of Infant Development (BSID)-I and -II (n=12), Brunet-Lezine test (n=2), videotape infant's movements (n=1), record time to milestones including sitting, crawling, standing and walking (n=1), problem-solving test (n=2), brainstem auditory-evoked potential (n=1), Touwen examination (n=1), Fagan test of infant intelligence (n=2) and visual habituation protocol (n=1). None of these end points have a long-term predictive property for neurocognitive assessment. Compared with standard infant formula, the beneficial effects of DHA/ARA supplementation on neurodevelopment were reported in 2 out of 12 studies using BSID vs 8 out of 11 studies using other end-point measures. In addition, 6 out of 29 long-term follow-up studies used the end points including Stanford–Binet IQ test (n=1), Wechsler Preschool and Primary Scale of Intelligence (n=4) and Bracken Basic Concept Scale (n=1), which are generally scales of intellectual ability and typically do not change substantively in the short term. None of these long-term follow-up studies demonstrated beneficial effects of DHA/ARA supplementation on neurodevelopment. The choice of end-point measures affects the outcomes of DHA/ARA-supplemented infant formula trials. Available data are currently inadequate to conclude that DHA/ARA supplementation has a clinically meaningful beneficial effect upon neurological development. Although BSID is validated to assess early developmental delays, it is not designed to predict long-term neurocognitive outcome. A well-defined, valid and reliable clinical outcome assessment that measures neurocognitive function in neonates and infants is essential to provide the scientific evidence required for future clinical trials.

We present simple and stable formulas for computing power (including absorbed/radiated, scattered and extinction power) in current-based volume integral equation formulations. The proposed formulas are given in terms of vector-matrix-vector products of quantities found solely in the associated linear system. In addition to their efficiency, the derived expressions can guarantee the positivity of the computed power. We also discuss the application of Poynting's theorem for the case of sources immersed in dissipative materials. The formulas are validated against results obtained both with analytical and numerical methods for scattering and radiation benchmark cases., Singapore-MIT Alliance for Research and Technology, MIT Skoltech Initiative, Massachusetts Institute of Technology. Institute for Soldier Nanotechnologies (Contract W911NF-07-D0004)

International audience; We study the nonlinear stationary waves propagating in metal slot waveguides with a Kerr-type dielectric core. We develop two independent semi-analytical models to describe these waves in such waveguides. Using those models we compute the dispersion curves for the first ten modes of a nonlinear slot waveguide. For symmetric waveguides we find symmetric, antisymmetric, and asymmetric higher order modes which are grouped in two families. In addition, we study the influence of the slot width on the first symmetric and asymmetric modes. We also show that the dispersion curve of the first asymmetric mode is invariant with respect to the slot width for high propagation constant values and we provide analytical approximations of this curve. Using realistic values for the optogeometric parameters of the structure, we are able to obtain the bifurcation at a realistic power.

The Casimir force originates from quantum fluctuations. While this force is too weak to have any measurable effects between objects at separations larger than ~ 10 μm it dominates the interaction between electrically neutral surfaces at the nanoscale. By fabricating a doubly clamped microbeam for sensing the force and a comb actuator to control the distance, we demonstrate that the Casimir force can become the dominant interaction between components within the same silicon chip.

We show that the near-field functionality of hyperbolic metamaterials (HMM), typically proposed for increasing the photonic local density of states (LDOS), can be achieved with thin metal films. Although HMMs have an infinite density of internally-propagating plane-wave states, the external coupling to nearby emitters is severely restricted. We show analytically that properly designed thin films, of thicknesses comparable to the metal size of a hyperbolic metamaterial, yield a LDOS as high as (if not higher than) that of HMMs. We illustrate these ideas by performing exact numerical computations of the LDOS of multilayer HMMs, along with their application to the problem of maximizing near-field heat transfer, to show that thin films are suitable replacements in both cases., Comment: 5 pages, 3 figures

We sought to explore the relationship between the diagnosis of hypertension and obstructive sleep apnea (OSA) in a Hispanic population, describe the effect of continuous positive airway pressure (CPAP) on blood pressure regulation, and assess the effect of CPAP on quality of life.A retrospective, recall interview study.Patients enrolled at the Home Oxygen Program of the San Juan V.A. Medical Center with the diagnosis of OSA and treatment with CPAP.The Calgary Sleep Apnea Quality of Life Index was administered to all patients after informed consent. Information regarding co-morbid conditions and fluctuations in blood pressure and anthropometric variables were obtained on a follow-up evaluation.After excluding for the use of antihypertensive medications, weight, and age, a 10% decrease in mean arterial pressure (MAP) from 100 mm Hg to 92 mm Hg was observed in an average of 40 months of therapy (p0.05). With the Calgary Quality of Life Index, 67% of the patients reported an extreme improvement in their quality of life. Compliance with CPAP therapy correlated with improved quality of life (r = 0.33, p0.015).In this pilot study, there appears to be a correlation between our intervention and decline of blood pressure, independent of body weight, age, or medication usage. CPAP treatment is an effective modality in improving symptoms and quality of life.

The estimation of real sucrose concentration, its accumulation, and differentiation from the rest of sugarcane juice carbohydrates is still an unsolved problem in sugarcane industry. Different techniques and analytical sequences have been used persistently with an objective to evaluate different types of carbohydrates with an acceptable minimum of interference. This paper puts forward results obtained during the evaluation of sugarcane juices from 10 months old cultivar My 5514. The immaturity of stalks allowed to study sucrose accumulation levels in different stalk sections. Low pressure liquid chromatography in a continuous flow combined with laser polarimetric detection is an effective tool to evaluate the behaviour of each carbohydrate in juice cultivars. Besides, this combination makes it possible to exclude from sucrose estimation those optically active non-sucrose compounds having high and medium molecular mass which could alter its real value in sugarcane juice when traditional methods are used.

Childhood cancer has been increasing significantly over the past two decades in the United States, suggesting that environmental exposures may be playing a causative role. One such cause may be maternal smoking during pregnancy. Suspected carcinogens in cigarette smoke and environmental pollution include N-nitrosamines and polycyclic aromatic hydrocarbons, which may be several micrograms per exposure. Previously, we have shown that mouse progeny of mothers exposed to benzo[a]pyrene (B[a]P) during midpregnancy had abnormalities in their humoral and cell-mediated immune response. Immunodeficiency was detectable during gestation, at one week after birth and persisted for 18 months. Tumor incidences in progeny were eight to 10-fold higher than in controls. The present study compared frequencies of CD4+, CD8+, V gamma 2+, and V beta 8+ T cells in progeny following in utero exposure to B[a]P. The significant reduction in newborn CD4+CD8+, CD4+CD8+V beta 8+ thymocytes and CD4+ splenocytes from 1-week-old progeny, suggests that B[a]P induces abnormal changes in developing T cells. These early alterations may lead to postnatal T cell suppression, thus providing a more suitable environment for the growth of tumors later in life. These results suggest that developmental immunosuppression mediated by B[a]P may play a critical role in the relationship between maternal exposures and childhood carcinogenesis.

Two different pools of glycoproteins, tentatively described as high and mid-molecular mass polymers, are currently separated by conventional gel filtration. Anion-exchange chromatography on DEAE-Sephadex A-60 discriminates between neutral or cationic, and anionic polymers composing both fractions. The occurrence of both cationic and anionic glycoproteins has been corroborated after separation by capillary electrophoresis. Total or partial digestion of the glycosidic moiety of these glycoproteins using β-1,2-fructofuranosidase reveals that cationic species from the mid molecular mass glycoproteins move to the neutral or anionic zone of the electropherogram whereas only one cationic form from high molecular mass polymers remains unchanged after enzymatic hydrolysis of the glycosidic moiety. This indicates that this moiety is able to modify the net charge of some of the mid-molecular mass glycoproteins whereas the net charge of cationic high molecular mass polymer can be due to the own protein moiety or, probably, to some polycationic polyamines bound on this moiety.

We have performed a phase II study to evaluate the activity and toxicity of ifosfamide and cisplatin as first-line treatment for advanced ovarian cancer. Patients were treated with cisplatin 100 mg/m 2 on day 1 and ifosfamide 5 g/m 2 in 18-hr continuous infusion on day 1 or 1.5 g/m 2 bolus on days 1–5. Between August 1988 and March 1990, 30 women were entered in the trial, 26 of them with measurable disease. The overall clinical response rate was 69% (95% CI: 48–85%), including 34.6% complete responses (95% CI:17–55%). Reassessment laparotomy was performed in 12 cases, and 4 (33%) exhibited a pathologic complete response. For all patients, the median duration of progression-free survival was 14 months, and the median overall survival was 25 months. There were no major differences in the response rate or survival between the two ifosfamide administration modalities. Relevant toxicities were grade IV hematologic toxicity in 11/30 patients and grade IV renal toxicity in 2/30 patients. A patient with grade IV encephalopathy developed a trauma-related cerebral hemorrhage and died 2 months later. The combination of ifosfamide and cisplatin is active in first-line therapy in advanced ovarian cancer, although it does not seem to improve the efficacy or toxicity profile of conventional combinations.

Using a combination of temporal coupled-mode theory and nonlinear finite-difference time-domain (FDTD) simulations, we study the nonlinear dynamics of all-resonant four-wave mixing processes and demonstrate the possibility of achieving high-efficiency limit cycles and steady states that lead to $\ensuremath{\approx}100%$ depletion of the incident light at low input (critical) powers. Our analysis extends previous predictions to capture important effects associated with losses, self- and cross-phase modulation, and imperfect frequency matching (detuning) of the cavity frequencies. We find that maximum steady-state conversion is hypersensitive to frequency mismatch, resulting in high-efficiency limit cycles that arise from the presence of a homoclinic bifurcation in the solution phase space, but that a judicious choice of incident frequencies and input powers, in conjuction with self-phase and cross-phase modulation, can restore high-efficiency steady-state conversion even for large frequency mismatch. Assuming operation in the telecom range, we predict close to perfect quantum efficiencies at reasonably low $\ensuremath{\sim}50\phantom{\rule{0.16em}{0ex}}\mathrm{m}\mathrm{W}$ input powers in silicon micrometer-scale PhC nanobeam cavities.

We predict that a low-permittivity oblate body (disk-shaped object) above a thin metal substrate (plate with a hole) immersed in a fluidof intermediate permittivity will experience a meta-stable equilibrium (restoring force) near the center of the hole. Stability is the result of a geometry-induced transition in the sign of the force, from repulsive to attractive, that occurs as the disk approaches the hole---in planar or nearly-planar geometries, the same material combination yields a repulsive force at all separations in accordance with the Dzyaloshinskii--Lifshitz--Pitaevskii condition of fluid-induced repulsion between planar bodies. We explore the stability of the system with respect to rotations and lateral translations of the disks, and demonstrate interesting transitions (bifurcations) in the rotational stability of the disks as a function of their size. Finally, we consider the reciprocal situation in which the disk--plate materials are interchanged, and find that in this case the system also exhibits meta-stability. The forces in the system are sufficiently large to be observed in experiments and should enable measurements based on the diffusion dynamics of the suspended bodies.

Photonic crystals provide superb opportunities for tailoring of the photonic density of states. This ability can in turn be explored to control radiation into far-field, enhance fluorescent light emission, as well as optimize laser emission. In order to make these phenomena useful for large macroscopic devices, large-area nano-fabrication techniques have to be successfully implemented. In this talk, I will present some of our recent theoretical and experimental progress in exploring these opportunities.

We describe a novel fluctuating-surface current formulation of radiative heat transfer between bodies of arbitrary shape that exploits efficient and sophisticated techniques from the surface-integral-equation formulation of classical electromagnetic scattering. Unlike previous approaches to non-equilibrium fluctuations that involve scattering matrices---relating "incoming" and "outgoing" waves from each body---our approach is formulated in terms of "unknown" surface currents, laying at the surfaces of the bodies, that need not satisfy any wave equation. We show that our formulation can be applied as a spectral method to obtain fast-converging semi-analytical formulas in high-symmetry geometries using specialized spectral bases that conform to the surfaces of the bodies (e.g. Fourier series for planar bodies or spherical harmonics for spherical bodies), and can also be employed as a numerical method by exploiting the generality of surface meshes/grids to obtain results in more complicated geometries (e.g. interleaved bodies as well as bodies with sharp corners). In particular, our formalism allows direct application of the boundary-element method, a robust and powerful numerical implementation of the surface-integral formulation of classical electromagnetism, which we use to obtain results in new geometries, including the heat transfer between finite slabs, cylinders, and cones.

The ability of the polycyclic aromatic hydrocarbon (PAH), benzo[a]pyrene (BP) and its metabolites to be immunosuppressive has been well documented by many investigators. The arylamine, 2-aminofluorene (AF) and its metabolic intermediates have not been as widely studied in this regard. Here, we investigate the effect of BP, 3-hydroxy-BP (3-OH-BP), AF, N-hydroxy-AF (N-OH-AF) and acetyl-AF (AAF) on T-cell proliferation using the T-cell mitogen, Concanavalin A (ConA). These compounds as well as BP-7, 8-diol-9, 10-epoxide (BPDE) were also used to determine their effect on T-cell-mitogen binding. Both AF and BP are substrates for the P-450 and flavin-containing monooxygenase enzyme system, which can be induced with beta-naphthoflavone (beta NF). We incubated beta nF with BP and AF to determine the effect of a P-450 inducer on BP and AF mediated-ConA suppression. Here we demonstrate that BP, 3-OH-BP, AF, and AAF are able to suppress the proliferative response to ConA, while N-OH-AF cannot. Further, we show that BP, 3-OH-BP, BPDE, AF and N-OH-AF do not alter the ability of ConA to bind the mitogen receptor of splenic T-cells, indicating an intracellular mechanism for suppression. Studies with beta NF indicate that this P-450 inducer enhances the anti-proliferative effect of BP, while it abolishes this effect of AF.

We predict that the near-field radiative heat-transfer rate between a cylinder and a perforated surface depends nonmonotonically on their separation. This anomalous behavior, which arises due to evanescent-wave effects, is explained using a heuristic model based on the interaction of a dipole with a plate. We show that nonmonotonicity depends not only on geometry and temperature but also on material dispersion---for micron and submicron objects, nonmonotonicity is present in polar dielectrics but absent in metals with small skin depths.

Author's final manuscript July 19, 2012, The famous Johnson-Nyquist formula relating noise current to conductance has a microscopic generalization relating noise current density to microscopic conductivity, with corollary relations governing noise in the components of the electromagnetic fields. These relations, known collectively in physics as fluctuation-dissipation relations, form the basis of the modern understanding of fluctuation-induced phenomena, a field of burgeoning importance in experimental physics and nanotechnology. In this review, we survey recent progress in computational techniques for modeling fluctuation-induced phenomena, focusing on two cases of particular interest: near-field radiative heat transfer and Casimir forces. In each case we review the basic physics of the phenomenon, discuss semianalytical and numerical algorithms for theoretical analysis, and present recent predictions for novel phenomena in complex material and geometric configurations., United States. Defense Advanced Research Projects Agency (Grant N66001-09-1-2070-DOD), Massachusetts Institute of Technology. Institute for Soldier Nanotechnologies (Grant W911NF-07-D-0004), United States. Air Force Office of Scientific Research. Multidisciplinary University Research Initiative (Complex and Robust On-chip Nanophotonics Grant FA9550-09-1-0704)

We describe a novel approach based on topology optimization that enables automatic discovery of wavelength-scale photonic structures for achieving high-efficiency second-harmonic generation (SHG). A key distinction from previous formulation and designs that seek to maximize Purcell factors at individual frequencies is that our method aims to not only achieve frequency matching (across an entire octave) and large radiative lifetimes, but also optimizes the equally important nonlinear-coupling figure of merit [bar over β], involving a complicated spatial overlap-integral between modes. We apply this method to the particular problem of optimizing micropost and grating-slab cavities (one-dimensional multilayered structures) and demonstrate that a variety of material platforms can support modes with the requisite frequencies, large lifetimes 𝑄 > 10[superscript 4], small modal volumes ∼(𝜆/𝑛)[superscript 3], and extremely large [bar over β] ≳ 10−2, leading to orders of magnitude enhancements in SHG efficiency compared to state-of-the-art photonic designs. Such giant [bar over β] alleviate the need for ultranarrow linewidths and thus pave the way for wavelength-scale SHG devices with faster operating timescales and higher tolerance to fabrication imperfections., Optical Society of America

We describe a fluctuating-surface-current formulation of radiative heat transfer, applicable to arbitrary geometries in both the near and far field, that directly exploits efficient and sophisticated techniques from the boundary-element method. We validate as well as extend previous results for spheres and cylinders, and also compute the heat transfer in a more complicated geometry consisting of two interlocked rings. Finally, we demonstrate how this method can be adapted to compute the spatial distribution of heat flux on the surfaces of the bodies.

Quantum fluctuations give rise to van der Waals and Casimir forces that dominate the interaction between electrically neutral objects at sub-micron separations. Under the trend of miniaturization, such quantum electrodynamical effects are expected to play an important role in micro- and nano-mechanical devices. Nevertheless, utilization of Casimir forces on the chip level remains a major challenge because all experiments so far require an external object to be manually positioned close to the mechanical element. Here by integrating a force-sensing micromechanical beam and an electrostatic actuator on a single chip, we demonstrate the Casimir effect between two micromachined silicon components on the same substrate. A high degree of parallelism between the two near-planar interacting surfaces can be achieved because they are defined in a single lithographic step. Apart from providing a compact platform for Casimir force measurements, this scheme also opens the possibility of tailoring the Casimir force using lithographically defined components of non-conventional shapes., United States. Defense Advanced Research Projects Agency (contract N66001-09-1-2070- DOD), Singapore-MIT Alliance. Program in Computational Engineering

The fastest self-sustained chemical reactions in nature occur during detonation of energetic materials where reactions are thought to occur on nanosecond or longer time scales in carbon-containing materials. Here we perform the first atomistic simulation of an azide energetic material, ${\mathrm{HN}}_{3}$, from the beginning to the end of the chemical evolution and find that the time scale for complete decomposition is a mere 10 ps, orders of magnitude shorter than that of secondary explosives and approaching the fundamental limiting time scale for chemistry; i.e., vibrational time scale. We study several consequences of the short time scale including a state of vibrational disequilibrium induced by the fast transformations.

In this paper we describe a general method to avoid stress-induced buckling of thin and large freestanding membranes. We show that using properly designed supports, in the form of microbeams, we can reduce the out-of-plane deflection of the membrane while maintaining its stiffness. As a proof of principle, we used a silicon-on-insulator (SOI) platform to fabricate 30 µm wide, 220 nm thick, free-standing Si membranes, supported by four 15 µm long and 3 µm wide microbeams. Using our approach, we are able to achieve an out-of-plane deformation of the membrane smaller than 50 nm in spite of 39 MPa of compressive internal stress. Our method is general, and can be applied to different material systems with compressive or tensile internal stress., United States. Defense Advanced Research Projects Agency. (Contract N66001-09-1-2070-DOD)

By engineering supporting beams of a thin opto-mechanical membrane, we are able to reduce the stress-induced deflection, and realize devices that feature strong optical force for probing the Casimir force.

We show how to compute Casimir forces at nonzero temperatures with time-domain electromagnetic simulations, for example using a finite-difference time-domain (FDTD) method. Compared to our previous zero-temperature time-domain method, only a small modification is required, but we explain that some care is required to properly capture the zero-frequency contribution. We validate the method against analytical and numerical frequency-domain calculations, and show a surprising high-temperature disappearance of a non-monotonic behavior previously demonstrated in a piston-like geometry., 5 pages, 2 figures, submitted to Physical Review A Rapid Communication

We demonstrate the possibility of achieving enhanced frequency-selective near-field radiative heat transfer between patterned (photonic-crystal) slabs at designable frequencies and separations, exploiting a general numerical approach for computing heat transfer in arbitrary geometries and materials based on the finite-difference time-domain method. Our simulations reveal a tradeoff between selectivity and near-field enhancement as the slab-slab separation decreases, with the patterned heat transfer eventually reducing to the unpatterned result multiplied by a fill factor (described by a standard proximity approximation). We also find that heat transfer can be further enhanced at selective frequencies when the slabs are brought into a glide-symmetric configuration, a consequence of the degeneracies associated with the nonsymmorphic symmetry group.

We demonstrate theoretical conditions for highly-efficient degenerate four-wave mixing in triply-resonant nonlinear (Kerr) cavities. We employ a general and accurate temporal coupled-mode analysis in which the interaction of light in arbitrary microcavities is expressed in terms a set of coupling coefficients that we rigorously derive from the full Maxwell equations. Using the coupled-mode theory, we show that light consisting of an input signal of frequency $\omega_0-\Delta \omega$ can, in the presence of pump light at $\omega_0$, be converted with quantum-limited efficiency into an output shifted signal of frequency $\omega_0 + \Delta \omega$, and we derive expressions for the critical input powers at which this occurs. We find that critical powers in the order of 10mW assuming very conservative cavity parameters (modal volumes $\sim10$ cubic wavelengths and quality factors $\sim1000$. The standard Manley-Rowe efficiency limits are obtained from the solution of the classical coupled-mode equations, although we also derive them from simple photon-counting "quantum" arguments. Finally, using a linear stability analysis, we demonstrate that maximal conversion efficiency can be retained even in the presence of self- and cross-phase modulation effects that generally act to disrupt the resonance condition., Comment: 13 pages, 8 figures. To appear in Physical Review A

Drawing inspiration from social interactions in nature, swarm intelligence has presented a promising approach to the design of complex systems consisting of numerous, simple parts, to solve a wide variety of problems. Swarm intelligence systems involve highly parallel computations across space, based heavily on the emergence of global behavior through local interactions of components. This has a disadvantage as the desired behavior of a system becomes hard to predict or design. Here we describe how to provide greater control over swarm intelligence systems, and potentially more useful goal-oriented behavior, by introducing hierarchical controllers in the components. This allows each particle-like controller to extend its reactive behavior in a more goal-oriented style, while keeping the locality of the interactions. We present three systems designed using this approach: a competitive foraging system, a system for the collective transport and distribution of goods, and a self-assembly system capable of creating complex 3D structures. Our results show that it is possible to guide the self-organization process at different levels of the designated task, suggesting that self-organizing behavior may be extensible to support problem solving in various contexts.

We have batch fabricated suspended nanochannel resonators (SNRs) to improve the mass resolution of suspended microchannel resonators (SMRs). The SNR consists of a cantilever that is 50 µm long, 10 µm wide, and 1.3 µm thick, with an embedded nanochannel that is 2 µm wide and 700 nm tall. The SNR has a resonance frequency near 640 kHz and exhibits the maximum quality factor of approximately 16,000 when dry and when filled with water. Using the SNRs, we demonstrated mass measurements of various nanoparticles down to 20 nm in diameter and viruses in solution with a resolution of 27 ag in a 1 kHz bandwidth, which represents a 100-fold improvement over existing SMRs and, to our knowledge, is the most precise mass measurement in liquid today.

Fueron examinados 11 pacientes adultos con el diagnostico presuntivo de neuro-cisticercosis, 8 de ellos provenientes de Bolivia y los restantes del interior de la Argentina. Como manifestacion clinica inicial el 82% de ellos mostro convulsiones y el 73% cefaleas. Ambas alteraciones podían estar combinadas en el mismo paciente o presentarse en forma independiente. La tomografia computada de cerebro evidencio calcificaciones y quistes en 5 enfermos, solo calcificaciones en 3, hidrocefalia en 2 y un unico quiste en 1. En 7 casos se efectuo ELISA en el LCR, de ellos 6 resultaron positivos. El tratamiento medico se hizo en base a la administración de praziquantel o albendazol con buena evolución de los pacientes en todos los casos. El tratamiento quirúrgico fue indicado solo en el caso en que una lesion actuase como masa ocupante con aumento de la presión endocraneana (1 caso) o produjera obstruccion de la circulacon del LCR llevando a una hidrocefalia (2 casos). El estudio presente pretende alertar sobre la posibilidad que nuevas regiones, como la Ciudad de Buenos Aires, puedan ingresar dentro del area endemica latinoamericana a consecuencia de los movimientos migratorios internos y externos y el asentamiento de portadores de la parasitosis en el perimetro urbano.

Polymorphic expression of arylamine N-acetyltransferase (EC 2.3.1.5) may be a differential risk factor in metabolic activation of arylamine carcinogens and susceptibility to cancers related to arylamine exposures. Human epidemiological studies suggest that rapid acetylator phenotype may be associated with higher incidences of colorectal cancer. We used restriction fragment length polymorphism analysis to determine acetylator genotypes of 44 subjects with colorectal cancer and 28 non-cancer subjects of similar ethnic background (i.e., approximately 25% Black and 75% White). The polymorphic N-acetyltransferase gene (NAT2) was amplified by the polymerase chain reaction from DNA templates derived from human colons of colorectal and non-cancer subjects. No significant differences inNAT2 allelic frequencies (i.e., WT, M1, M2, M3 alleles) or in acetylator genotypes were found between the colorectal cancer and non-cancer groups. No significant differences inNAT2 allelic frequencies were observed between Whites and Blacks or between males and females. Cytosolic preparations from the human colons were tested for expression of arylamine N-acetyltransferase activity. Although N-acetyltransferase activity was expressed for each of the arylamines tested (i.e., p-aminobenzoic acid, 4-aminobiphenyl, 2-aminofluorene, β-naphthylamine), no correlation was observed between acetylator genotype and expression of human colon arylamine N-acetyltransferase activity. Similarly, no correlation was observed between subject age and expression of human colon arylamine N-acetyltransferase activity. These results suggest that arylamine N-acetyltransferase activity expressed in human colon is catalyzed predominantly by NAT1, an arylamine N-acetyltransferase that is not regulated byNAT2 acetylator genotype. The ability to determine acetylator genotype from DNA derived from human surgical samples should facilitate further epidemiological studies to assess the role of acetylator genotype in various cancers.

Our previous article [Phys. Rev. Lett. 104, 060401 (2010)] predicted that Casimir forces induced by the material-dispersion properties of certain dielectrics can give rise to stable configurations of objects. This phenomenon was illustrated via a dicluster configuration of non-touching objects consisting of two spheres immersed in a fluid and suspended against gravity above a plate. Here, we examine these predictions from the perspective of a practical experiment and consider the influence of non-additive, three-body, and nonzero-temperature effects on the stability of the two spheres. We conclude that the presence of Brownian motion reduces the set of experimentally realizable silicon/teflon spherical diclusters to those consisting of layered micro-spheres, such as the hollow- core (spherical shells) considered here., 11 pages, 9 figures

In this work we theoretically consider the Casimir force between two periodic arrays of nanowires (both in vacuum, and on a substrate separated by a fluid) at separations comparable to the period. Specifically, we compute the dependence of the exact Casimir force between the arrays under both lateral translations and rotations. Although typically the force between such structures is well-characterized by the Proximity Force Approximation (PFA), we find that in the present case the microstructure modulates the force in a way qualitatively inconsistent with PFA. We find instead that effective-medium theory, in which the slabs are treated as homogeneous, anisotropic dielectrics, gives a surprisingly accurate picture of the force, down to separations of half the period. This includes a situation for identical, fluid-separated slabs in which the exact force changes sign with the orientation of the wire arrays, whereas PFA predicts attraction. We discuss the possibility of detecting these effects in experiments, concluding that this effect is strong enough to make detection possible in the near future., 12 pages, 9, figure. Published version with expanded discussion

Quantum dot (QD) luminescent solar concentrator (LSC) uses a sheet of highly transparent materials doped with luminescent QDs materials. Sunlight is absorbed by these quantum dots and emitted through down conversion process. The emitted light is trapped in the sheet and travels to the edges where it can be collected by photovoltaic solar cells. In this study, we investigate the performance of LSCs fabricated with near infrared QDs (lead sulfide) and compared with the performance of LSCs containing normal visible QDs (CdSe/ZnS), and LSCs containing organic dye (Rhodamine B). Effects of materials concentrations (related to re-absorption) on the power conversion efficiency are also analyzed. The results show that near infrared QDs LSCs can generate nearly twice as much as the output current from normal QDs and organic dye LSCs. This is due to their broad absorption spectra. If stability of QDs is further improved, the near infrared QDs will dramatically improve the efficiency of LSCs for solar energy conversion with lower cost per Wp.

We present two photonic crystal enabled platforms, exhibiting novel active optical phenomena. First, using a detailed theoretical and numerical analysis, we show how a Purcell-effect inspired nonlinear nanophotonic scheme could enable optimal and compact THz sources via optical difference frequency generation. Second, we show how electromagnetic one-way edge modes analogous to quantum Hall edge states, originally predicted by Raghu and Haldane in gyroelectric photonic crystals, can appear in more general settings. In gyromagnetic YIG photonic crystals operating at microwave frequencies, time-reversal breaking is strong enough that the effect is readily observable. We present our experimental results on this novel phenomenon.

In terrestrial free-space laser communication, aside from pointing issues, the major problem that have to be dealt with is the turbulent atmosphere that produces irradiance fluctuations in the received signal, greatly reducing the link performance. Aperture averaging is the standard method used to mitigate these irradiance fluctuations consisting in increasing the area of the detector, or effectively increasing it by using a collecting lens with a diameter as large as possible. Prediction of the aperture averaging factor for Gaussian beam with currently available theory is compared with data collected experimentally and simulations based in the beam propagation method, where the atmospheric turbulence is represented by linearly spaced random phase screens. Experiments were carried out using a collecting lens with two simultaneous detectors, one of them with a small aperture to emulate an effective point detector, while the other one was mounted with interchangeable diaphragms, hence measurements for different aperture diameters could be made. The testbed for the experiments consists of a nearly horizontal path of 1.2 km with the transmitter and receiver on either side of the optical link. The analysis of the experimental data is used to characterize the aperture averaging factor when different values of laser divergence are selected.

We propose a method of achieving large temperature sensitivity in the Casimir force that involves measuring the stable separation between dielectric objects immersed in fluid. We study the Casimir force between slabs and spheres using realistic material models, and find large > 2nm/K variations in their stable separations (hundreds of nanometers) near room temperature. In addition, we analyze the effects of Brownian motion on suspended objects, and show that the average separation is also sensitive to changes in temperature . Finally, this approach also leads to rich qualitative phenomena, such as irreversible transitions, from suspension to stiction, as the temperature is varied.

We examine a recent prediction for the chirality-dependence of the Casimir force in chiral metamaterials by numerical computation of the forces between the exact microstructures, rather than homogeneous approximations. We compute the exact force for a chiral bent-cross pattern, as well as forces for an idealized "omega"-particle medium in the dilute approximation and identify the effects of structural inhomogeneity (i.e. proximity forces and anisotropy). We find that these microstructure effects dominate the force for separations where chirality was predicted to have a strong influence. To get observations of chirality free from microstructure effects, one must go to large separations where the effect of chirality is at most $\sim10^{-4}$ of the total force., 5 pages, 4 figures

We derive a correspondence between the contour integration of the Casimir stress tensor in the complex-frequency plane and the electromagnetic response of a physical dissipative medium in a finite real-frequency bandwidth. The consequences of this correspondence are at least threefold: First, the correspondence makes it easier to understand Casimir systems from the perspective of conventional classical electromagnetism, based on real-frequency responses, in contrast to the standard imaginary-frequency point of view based on Wick rotations. Second, it forms the starting point of finite-difference time-domain numerical techniques for calculation of Casimir forces in arbitrary geometries. Finally, this correspondence is also key to a technique for computing quantum Casimir forces at micrometer scales using antenna measurements at tabletop (e.g., centimeter) scales, forming a type of analog computer for the Casimir force. Superficially, relationships between the Casimir force and the classical electromagnetic Green’s function are well known, so one might expect that any experimental measurement of the Green’s function would suffice to calculate the Casimir force. However, we show that the standard forms of this relationship lead to infeasible experiments involving infinite bandwidth or exponentially growing fields, and a fundamentally different formulation is therefore required.

We give an example of a geometry in which two metallic objects in vacuum experience a repulsive Casimir force. The geometry consists of an elongated metal particle centered above a metal plate with a hole. We prove that this geometry has a repulsive regime using a symmetry argument and confirm it with numerical calculations for both perfect and realistic metals. The system does not support stable levitation, as the particle is unstable to displacements away from the symmetry axis., 4 pages, 4 figures; added references, replaced Fig. 3

Purpose Patients with advanced gastric or gastroesophageal adenocarcinoma need more efficacious and safer treatments than established today. S-1, a contemporary oral fluoropyrimidine, can provide that advantage. Patients and Methods This study was conducted in 24 countries and 146 centers. One thousand fifty-three patients were stratified (center, number of metastatic sites, prior adjuvant therapy, and measurable cancer) and randomly assigned. Patients received either S-1 at 50 mg/m2 divided in two daily doses for 21 days and cisplatin at 75 mg/m2 intravenously on day 1, repeated every 28 days (527 patients) or infusional fluorouracil at 1,000 mg/m2/24 hours for 120 hours and cisplatin at 100 mg/m2 intravenously on day 1, repeated every 28 days (526 patients). The primary end point was superiority in overall survival (OS) from cisplatin/S-1 compared with cisplatin/infusional fluorouracil in patients with advanced, untreated gastric, or gastroesophageal adenocarcinoma. The secondary end points were response rate, progression-free survival, time to treatment failure, and safety. Results The median OS was 8.6 months in the cisplatin/S-1 arm and 7.9 months in the cisplatin/infusional fluorouracil arm (HR, 0.92; 95% CI, 0.80 to 1.05; P = .20). Significant safety advantages were observed in the cisplatin/S-1 arm compared with the cisplatin/infusional fluorouracil arm for the rates of grade 3/4 neutropenia (32.3% v 63.6%), complicated neutropenia (5.0% v 14.4%), stomatitis (1.3% v 13.6%), hypokalemia (3.6% v 10.8%), and treatment-related deaths (2.5% v 4.9%; P < .05). Conclusion Cisplatin/S-1 did not prolong OS of patients with advanced gastric or gastroesophageal adenocarcinoma compared with cisplatin/infusional fluorouracil, but it did result in a significantly improved safety profile.

We present a scheme for obtaining stable Casimir suspension of dielectric nontouching objects immersed in a fluid, validated here in various geometries consisting of ethanol-separated dielectric spheres and semi-infinite slabs. Stability is induced by the dispersion properties of real dielectric (monolithic) materials. A consequence of this effect is the possibility of stable configurations (clusters) of compact objects, which we illustrate via a "molecular" two-sphere dicluster geometry consiting of two bound spheres levitated above a gold slab. Our calculations also reveal a strong interplay between material and geometric dispersion, and this is exemplified by the qualitatively different stability behavior observed in planar versus spherical geometries.

We propose a scheme for efficient cavity-enhanced nonlinear THz generation via difference-frequency generation (DFG) processes using a triply resonant system based on photonic crystal cavities. We show that high nonlinear overlap can be achieved by coupling a THz cavity to a doubly-resonant, dual-polarization near-infrared (e.g. telecom band) photonic-crystal nanobeam cavity, allowing the mixing of three mutually orthogonal fundamental cavity modes through a chi(2) nonlinearity. We demonstrate through coupled-mode theory that complete depletion of the pump frequency - i.e., quantum-limited conversion - is possible in an experimentally feasible geometry, with the operating output power at the point of optimal total conversion efficiency adjustable by varying the mode quality (Q) factors.

Achieving efficient terahertz (THz) generation using compact turn-key sources operating at room temperature and modest power levels represents one of the critical challeges that must be overcome to realize truly practical applications based on THz. Up to now, the most efficient approaches to THz generation at room temperature -- relying mainly on optical rectification schemes -- require intricate phase-matching set-ups and powerful lasers. Here we show how the unique light-confining properties of triply-resonant photonic resonators can be tailored to enable dramatic enhancements of the conversion efficiency of THz generation via nonlinear frequency down-conversion processes. We predict that this approach can be used to reduce up to three orders of magnitude the pump powers required to reach quantum-limited conversion efficiency of THz generation in nonlinear optical material systems. Furthermore, we propose a realistic design readily accesible experimentally, both for fabrication and demonstration of optimal THz conversion efficiency at sub-W power levels.

We derive general conditions for 100% frequency conversion in any doubly resonant nonlinear cavity, for both second- and third-harmonic generation via Chi?((2))and Chi((3)) nonlinearities. We find that conversion efficiency is optimized for a certain "critical" power depending on the cavity parameters, and assuming reasonable parameters we predict 100% conversion using milliwatts of power or less. These results follow from a semi-analytical coupled-mode theory framework which is generalized from previous work to include both Chi((2))and Chi((3))?media as well as inhomogeneous (fully vectorial) cavities, analyzed in the high-efficiency limit where down-conversion processes lead to a maximum efficiency at the critical power, and which is verified by direct finite-difference time-domain (FDTD) simulations of the nonlinear Maxwell equations. Explicit formulas for the nonlinear coupling coefficients are derived in terms of the linear cavity eigenmodes, which can be used to design and evaluate cavities in arbitrary geometries.

We introduce an efficient technique for computing Casimir energies and forces between objects of arbitrarily complex 3D geometries. In contrast to other recently developed methods, our technique easily handles non-spheroidal, non-axisymmetric objects and objects with sharp corners. Using our new technique, we obtain the first predictions of Casimir interactions in a number of experimentally relevant geometries, including crossed cylinders and tetrahedral nanoparticles., Comment: 4 pages, 4 figures