Modelling structural colour from helicoidal multi-layer thin films with natural disorder

A coupled mode theory based on Takagi-Taupin equations describing electromagnetic scattering from distorted periodic arrays is applied to the problem of light scattering from beetles. We extend the method to include perturbations in the permittivity tensor to helicoidal arrays seen in many species of scarab beetle and optically anisotropic layered materials more generally. This extension permits analysis of typical dislocations arising from the biological assembly process and the presence of other structures in the elytra. We show that by extracting structural information from transmission electron microscopy data, including characteristic disorder parameters, good agreement with spectral specular and non-specular reflectance measurements is obtained.

Addressing Missing Data in GC × GC Metabolomics: Identifying Missingness Type and Evaluating the Impact of Imputation Methods on Experimental Replication

Missing data is a significant issue in metabolomics that is often neglected when conducting data preprocessing, particularly when it comes to imputation. This can have serious implications for downstream statistical analyses and lead to misleading or uninterpretable inferences. In this study, we aim to identify the primary types of missingness that affect untargeted metabolomics data and compare strategies for imputation using two real-world comprehensive two-dimensional gas chromatography (GC × GC) data sets. We also present these goals in the context of experimental replication whereby imputation is conducted in a within-replicate-based fashion─the first description and evaluation of this strategy─and introduce an R package MetabImpute to carry out these analyses. Our results conclude that, in these two GC × GC data sets, missingness was most likely of the missing at-random (MAR) and missing not-at-random (MNAR) types as opposed to missing completely at-random (MCAR). Gibbs sampler imputation and Random Forest gave the best results when imputing MAR and MNAR compared against single-value imputation (zero, minimum, mean, median, and half-minimum) and other more sophisticated approaches (Bayesian principal component analysis and quantile regression imputation for left-censored data). When samples are replicated, within-replicate imputation approaches led to an increase in the reproducibility of peak quantification compared to imputation that ignores replication, suggesting that imputing with respect to replication may preserve potentially important features in downstream analyses for biomarker discovery.

Spaceflight Analogue Culture Enhances the Host-Pathogen Interaction Between Salmonella and a 3-D Biomimetic Intestinal Co-Culture Model

Physical forces associated with spaceflight and spaceflight analogue culture regulate a wide range of physiological responses by both bacterial and mammalian cells that can impact infection. However, our mechanistic understanding of how these environments regulate host-pathogen interactions in humans is poorly understood. Using a spaceflight analogue low fluid shear culture system, we investigated the effect of Low Shear Modeled Microgravity (LSMMG) culture on the colonization of Salmonella Typhimurium in a 3-D biomimetic model of human colonic epithelium containing macrophages. RNA-seq profiling of stationary phase wild type and Δhfq mutant bacteria alone indicated that LSMMG culture induced global changes in gene expression in both strains and that the RNA binding protein Hfq played a significant role in regulating the transcriptional response of the pathogen to LSMMG culture. However, a core set of genes important for adhesion, invasion, and motility were commonly induced in both strains. LSMMG culture enhanced the colonization (adherence, invasion and intracellular survival) of Salmonella in this advanced model of intestinal epithelium using a mechanism that was independent of Hfq. Although S. Typhimurium Δhfq mutants are normally defective for invasion when grown as conventional shaking cultures, LSMMG conditions unexpectedly enabled high levels of colonization by an isogenic Δhfq mutant. In response to infection with either the wild type or mutant, host cells upregulated transcripts involved in inflammation, tissue remodeling, and wound healing during intracellular survival. Interestingly, infection by the Δhfq mutant led to fewer transcriptional differences between LSMMG- and control-infected host cells relative to infection with the wild type strain. This is the first study to investigate the effect of LSMMG culture on the interaction between S. Typhimurium and a 3-D model of human intestinal tissue. These findings advance our understanding of how physical forces can impact the early stages of human enteric salmonellosis.

A Metabolomic Approach for Predicting Diurnal Changes in Cortisol

Introduction: The dysregulation of cortisol secretion has been associated with a number of mental health and mood disorders. However, diagnostics for mental health and mood disorders are behavioral and lack biological contexts. Objectives: The goal of this work is to identify volatile metabolites capable of predicting changes in total urinary cortisol across the diurnal cycle for long-term stress monitoring in psychological disorders. Methods: We applied comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry to sample the urinary volatile metabolome using an untargeted approach across three time points in a single day for 60 subjects. Results: The finalized multiple regression model includes 14 volatile metabolites and 7 interaction terms. A review of the selected metabolites suggests pyrrole, 6-methyl-5-hepten-2-one and 1-iodo-2-methylundecane may originate from endogenous metabolic mechanisms influenced by glucocorticoid signaling mechanisms. Conclusion: This analysis demonstrated the feasibility of using specific volatile metabolites for the prediction of secreted cortisol across time.

Longitudinal Associations of the Cystic Fibrosis Airway Microbiome and Volatile Metabolites: A Case Study

The identification of 16S rDNA biomarkers from respiratory samples to describe the continuum of clinical disease states within persons having cystic fibrosis (CF) has remained elusive. We sought to combine 16S, metagenomics, and metabolomics data to describe multiple transitions between clinical disease states in 14 samples collected over a 12-month period in a single person with CF. We hypothesized that each clinical disease state would have a unique combination of bacterial genera and volatile metabolites as a potential signature that could be utilized as a biomarker of clinical disease state. Taxonomy identified by 16S sequencing corroborated clinical culture results, with the majority of the 109 PCR amplicons belonging to the bacteria grown in clinical cultures (Escherichia coli and Staphylococcus aureus). While alpha diversity measures fluctuated across disease states, no significant trends were present. Principle coordinates analysis showed that treatment samples trended toward a different community composition than baseline and exacerbation samples. This was driven by the phylum Bacteroidetes (less abundant in treatment, log₂ fold difference -3.29, p = 0.015) and the genus Stenotrophomonas (more abundant in treatment, log₂ fold difference 6.26, p = 0.003). Across all sputum samples, 466 distinct volatile metabolites were identified with total intensity varying across clinical disease state. Baseline and exacerbation samples were rather uniform in chemical composition and similar to one another, while treatment samples were highly variable and differed from the other two disease states. When utilizing a combination of the microbiome and metabolome data, we observed associations between samples dominated Staphylococcus and Escherichia and higher relative abundances of alcohols, while samples dominated by Achromobacter correlated with a metabolomics shift toward more oxidized volatiles. However, the microbiome and metabolome data were not tightly correlated; examining both the metagenomics and metabolomics allows for more context to examine changes across clinical disease states. In our study, combining the sputum microbiome and metabolome data revealed stability in the sputum composition through the first exacerbation and treatment episode, and into the second exacerbation. However, the second treatment ushered in a prolonged period of instability, which after three additional exacerbations and treatments culminated in a new lung microbiome and metabolome.

Metasurfaces with Asymmetric Optical Transfer Functions for Optical Signal Processing

Metasurface thin films created from arrays of structured optical elements have been shown to perform spatial filtering of optical signals. To extend their usefulness it is important that the symmetry of their response with changes to the in-plane wave vector k_{p}→-k_{p} can be tailored or even dynamically tuned. In this Letter we use a general theory of metasurfaces constructed from nondiffracting arrays of coupled metal particles to derive the optical transfer function and identify the physical properties essential for asymmetry. We validate our theory experimentally showing how the asymmetric response of a two-dimensional (planar) metasurface can be optically tuned. Our results set the direction for future developments of metasurfaces for optical signal processing.

Advances in the application of comprehensive two-dimensional gas chromatography in metabolomics

Due to excellent separation capacity for complex mixtures of chemicals, comprehensive two-dimensional gas chromatography (GC × GC) is being utilized with increasing frequency for metabolomics analyses. This review describes recent advances in GC × GC method development for metabolomics, organismal sampling techniques compatible with GC × GC, metabolomic discoveries made using GC × GC, and recommendations and best practices for collecting and reporting GC × GC metabolomics data.

Excitation of bound plasmons along nanoscale stripe waveguides: a comparison of end and grating coupling techniques

In this paper we excite bound long range stripe plasmon modes with a highly focused laser beam. We demonstrate highly confined plasmons propagating along a 50 µm long silver stripe 750 nm wide and 30 nm thick. Two excitation techniques were studied: focusing the laser spot onto the waveguide end and focusing the laser spot onto a silver grating. By comparing the intensity of the out-coupling photons at the end of the stripe for both grating and end excitation we are able to show that gratings provide an increase of a factor of two in the output intensity and thus out-coupling of plasmons excited by this technique are easier to detect. Authors expect that the outcome of this paper will prove beneficial for the development of passive nano-optical devices based on stripe waveguides, by providing insight into the different excitation techniques available and the advantages of each technique.

Material effects on V-nanoantenna performance

There is great interest in aluminum based plasmonic devices due to the relatively high plasma frequency of this material as well as its low cost and self-passivating oxide layer. The passivation layer provides aluminum plasmonics with the long-term stability required for practical applications. While several studies have investigated the impact of this oxide layer on the plasmon resonances of aluminum nanostructures on glass substrates, little is known about the effect of high-refractive index substrates on these resonances. Here we present an investigation of aluminum V-shaped antennas resonant in the visible on a silicon substrate. Through comparison between numerical and experimental results, we show that the aluminium passivation layer has little effect on the antenna resonances by comparing numerical simulations both with and without. We show, however, that inclusion of the native oxide layer of the silicon substrate in numerical models is critical for achieving good agreement with experimental data. Furthermore, we computationally explore the influence of the 1.5 eV interband transition of aluminum on plasmon resonances, and find that its effect on the material properties of the resonant structures results in narrower resonances in the blue part of the spectrum than if it was not present.

The dark side of plasmonics

Plasmonic dark modes are pure near-field modes that can arise from the plasmon hybridization in a set of interacting nanoparticles. When compared to bright modes, dark modes have longer lifetimes due to their lack of a net dipole moment, making them attractive for a number of applications. We demonstrate the excitation and optical detection of a collective dark plasmonic mode from individual plasmonic trimers. The trimers consist of triangular arrangements of gold nanorods, and due to this symmetry, the lowest-energy dark plasmonic mode can interact with radially polarized light. The experimental data presented confirm the excitation of this mode, and its assignment is supported with an electrostatic approximation wherein these dark modes are described in terms of plasmon hybridization. The strong confinement of energy in these modes and their associated near fields hold great promise for achieving strong coupling to single photon emitters.

Frequency-dependent optical steering from subwavelength plasmonic structures

We show theoretically and with numerical simulations that the direction of the in-plane scattering from a subwavelength optical antenna system can be controlled by the frequency of the incident light. This optical steering effect does not rely on propagation phase shifts or diffraction but arises from phase shifts in the localized surface plasmon modes of the antenna. An analytical model is developed to optimize the parameters for the configuration, showing good agreement with a rigorous numerical simulation. The simulation predicts a 25° angular shift in the direction of the light scattered from two gold nanorods for a wavelength change of 12 nm.

Chiral electromagnetic fields generated by arrays of nanoslits

Using a modal matching theory, we demonstrate the generation of short-range, chiral electromagnetic fields via the excitation of arrays of staggered nanoslits that are chiral in two dimensions. The electromagnetic near fields, which exhibit a chiral density greater than that of circularly polarized light, can enhance the chiroptical interactions in the vicinity of the nanoslits. We discuss the features of nanostructure symmetry required to obtain the chiral fields and explicitly show how these structures can give rise to detection and characterization of materials with chiral symmetry.

Simple model for the hybridization of surface plasmon resonances in metallic nanoparticles

An "electrostatic" eigenmode method based on the coupling of evanescent electric fields is presented for modeling the hybridization of localized surface plasmon resonances in metallic nanoparticles of arbitrary shape. The method yields simple analytical expressions for the hybridized energies and excitation amplitudes of nanoparticle ensembles. Because of its ease of applicability and simple conceptual basis, we anticipate that the method will be of value in understanding and predicting the effects of interacting plasmonic nanoparticles.

Surface plasmon mediated strong exciton-photon coupling in semiconductor nanocrystals

We present an experimental demonstration of strong coupling between a surface plasmon propagating on a planar silver thin film and the lowest excited state of CdSe nanocrystals. Attenuated total reflection measurements demonstrate the formation of plasmon-exciton mixed states, characterized by a Rabi splitting of approximately 112 meV at room temperature. Such a coherent interaction has the potential for the development of nonlinear plasmonic devices, and furthermore, this system is akin to those studied in cavity quantum electrodynamics, thus offering the possibility to study the regime of strong light-matter coupling in semiconductor nanocrystals under easily accessible experimental conditions.

Dual resonance mechanisms facilitating enhanced optical transmission in coaxial waveguide arrays

We experimentally and computationally demonstrate high transmission through arrays of coaxial apertures with different geometries and arrangements in silver films. By studying both periodic and random arrangements of apertures, we were able to isolate transmission enhancement phenomena owing to surface plasmon effects from those owing to the excitation of cylindrical surface plasmons within the apertures themselves.

A hand-held surface plasmon resonance biosensor for the detection of ricin and other biological agents

There is an ongoing need for field-deployable biosensor devices. We have constructed a fully self-contained, hand-held biosensor, based on the surface plasmon resonance technique. The dimensions of the sensor unit are 15 x 8 cm, the weight is 600 g and it is powered by a 9 V battery. We have characterised the responsiveness of the sensor using calibrated sucrose solutions and were able to measure changes as small as 3.3 x 10(-6) refractive index units. To demonstrate functionality of the sensor, we have prepared surfaces with an antibody fragment specific for the biological toxin ricin. We were able to detect ricin at 200 ng/mL in 10 min, which is approximately 2500 times less than the minimum lethal dose. We were also able to verify positive binding within a second 10 min window. This sensor demonstrates important steps required for the development of fully integrated, hand-held sensor devices and will form the basis of a multi-analyte system, to be developed in the near future. It also represents the first completely hand-held SPR device, not requiring external power or a computer connection to operate.

Brownian diffusion of nano-particles in optical traps

The effect of thermal-induced motion on nano-particles in optical traps is examined theoretically. We derive the steady-state probability density for particles trapped by evanescent waves above a surface. In particular we investigate the enhancement of the gradient force by surface plasmon resonance in a gold film and its application to trapping nano-particles in solution. An expression is derived for the lifetime of nano-particles in the trap in terms of the ratio of the trap energy to the thermal energy. It is shown that this ratio should be 10 or greater for the nano-particles to remain in the trap.

Quantitative X-ray projection microscopy: phase-contrast and multi-spectral imaging

We outline a new approach to X-ray projection microscopy in a scanning electron microscope (SEM), which exploits phase contrast to boost the quality and information content of images. These developments have been made possible by the combination of a high-brightness field-emission gun (FEG)-based SEM, direct detection CCD technology and new phase retrieval algorithms. Using this approach we have been able to obtain spatial resolution of < 0.2 micro m and have demonstrated novel features such as: (i) phase-contrast enhanced visibility of high spatial frequency image features (e.g. edges and boundaries) over a wide energy range; (ii) energy-resolved imaging to simultaneously produce multiple quasi-monochromatic images using broad-band polychromatic illumination; (iii) easy implementation of microtomography; (iv) rapid and robust phase/amplitude-retrieval algorithms to enable new real-time and quantitative modes of microscopic imaging. These algorithms can also be applied successfully to recover object-plane information from intermediate-field images, unlocking the potentially greater contrast and resolution of the intermediate-field regime. Widespread applications are envisaged for fields such as materials science, biological and biomedical research and microelectronics device inspection. Some illustrative examples are presented. The quantitative methods described here are also very relevant to projection microscopy using other sources of radiation, such as visible light and electrons.

Optimization of asymmetric catalysts using achiral ligands: metal geometry-induced ligand asymmetry

[reaction: see text] Traditionally, asymmetric catalysts have been optimized by modification of resolved chiral ligands. In this Letter, we optimize the asymmetric addition of diethylzinc to aldehydes by modification of achiral methylene bis(phenol) ligands. Upon coordination of the substrate, the achiral ligand becomes asymmetric, a concept termed Metal Geometry-Induced Ligand Asymmetry. The enantioselectivity of the catalyst formed from a single resolved ligand and several achiral ligands ranged from 9% (R) to 83% (S).

Location of Zn within the Mg12(LaxCe1-x) lattice by X-ray incoherent channelling patterns

Systematic electron diffraction studies on intermetallic precipitates formed within a lightweight Mg-RE-Zn alloy (RE = La or Ce) identify these to be of structural type Mn(12)Th (space group I4/mmm). Analytical electron microscopy yields an overall composition of Mg(12)(La(x)Ce(1-x)) with x ~ 0.43, with 1 at.% Zn incorporated within the lattice. Variations in characteristic X-ray emission rates, as an electron beam is rocked near zone-axis orientations, are used to form two-dimensional channelling patterns, termed X-ray incoherent channelling patterns. This channelling contrast enables a specific sublattice site that is occupied by Zn to be unambiguously identified within the Mg(12)RE lattice. The particular sublattice site is denoted by the Wyckoff letter f, and is one of the three different Mg sublattice sites f, i and j. Of these three sites, the Wigner-Seitz cell that is centred on the f sublattice site has the largest Mg-RE interatomic distance, and therefore the f site is expected to be favoured for accommodating the substitution of a larger Zn atom.

Snapshots of titanium BINOLate complexes with diverse solid state structures

[structure: see text]. Many important asymmetric reactions are catalyzed by (BINOLate)Ti species with unknown structures. Reported here are three structures of BINOLate titanium complexes that show an interesting aggregation of (BINOLate)Ti(OiPr)2 with itself and with titanium tetraisopropoxide. These complexes are potential intermediates in the asymmetric addition of alkyl groups to aldehydes.

Correlation of the intercondylar notch width of the femur to the width of the anterior and posterior cruciate ligaments

The purpose of this study was to determine if a correlation exists between the intercondylar notch width (NW) of the femur and the width of the anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL). A study group of 124 consecutive patients (mean age 36.6 +/- 15.2 years; 67 men, 57 women) underwent a magnetic resonance imaging evaluation for knee pain but did not have an ACL or PCL tear or arthrosis. A T2 weighted coronal cut was identified and was located at the middle of the tibial spine, which represented the plane where the ACL and PCL cross each other when the knee is in 10 degrees of flexion. The NW and the width of the ACL and PCL were measured at the level of the middle of the popliteal hiatus on a physician-independent console that allowed for digital measurements in millimeters. Our results showed a statistically significant correlation between NW and ACL width (r = 0.87; P < 0.001) and between NW and PCL width (r = 0.75; P < 0.001). The mean ACL width was 6.4 +/- 1.4 mm (range 3-10 mm). The mean PCL width was 10.2 +/- 2.0 mm (range 6-17 mm). The mean ACL width was 5.7 +/- 1.1 mm for women and 7.1 +/- 1.2 mm for men (P < 0.001). The mean PCL width was 9.5 +/- 1.7 mm for women and 10.9 +/- 2.0 for men (P < 0.001). Our results indicate that NW correlates with ACL and PCL width. In addition, ACL and PCL widths are narrower in women than men.

The natural history of acute, isolated, nonoperatively treated posterior cruciate ligament injuries. A prospective study

We sought to determine prospectively the natural history of acute, isolated, nonoperatively treated posterior cruciate ligament injuries in athletically active patients. The study population consisted of 133 patients (average age, 25.2 years at time of injury). All patients completed a subjective questionnaire each year for an average of 5.4 years (range, 2.3 to 11.4). Sixty-eight of the 133 patients returned to the clinic for long-term follow-up evaluation. Objectively, physical examination revealed no change in laxity from initial injury to follow-up. No correlation was found between radiographic joint space narrowing and grade of laxity. The mean modified Noyes knee score was 84.2 points, the mean Lysholm score was 83.4, and the mean Tegner activity score was 5.7. Patients with greater laxity did not have worse subjective scores. No correlation was found between subjective knee scores and time from injury. Regardless of the amount of laxity, half of the patients returned to the same sport at the same or higher level, one-third returned to the same sport at a lower level, and one-sixth did not return to the same sport. Results of this study suggest that athletically active patients with acute isolated posterior cruciate ligament tears treated nonoperatively achieved a level of objective and subjective knee function that was independent of the grade of laxity.

Evaluation of knee stability before and after participation in a functional sports agility program during rehabilitation after anterior cruciate ligament reconstruction

We sought to determine whether participation in a functional sports agility program as early as 4 weeks after anterior cruciate ligament reconstruction with autogenous patellar tendon graft would affect objective knee stability in 603 patients. The rehabilitation program prescribed a functional sports agility program at a mean of 5.1 +/- 1.0 weeks postoperatively when full knee hyperextension, knee flexion to 120 degrees, and quadriceps muscle strength of 60% of the normal leg had been achieved. The patients had KT-1000 arthrometer testing before beginning the program and at subsequent follow-up after they had performed the sport activity. The mean manual maximum KT-1000 arthrometer difference was 1.9 +/- 1.3 mm at initial testing and 1.9 +/- 1.2 mm at follow-up testing. The frequency distribution of the KT-1000 arthrometer scores revealed that 92.7% of patients at initial testing and 93.2% of patients at follow-up testing had displacement difference of 3 mm or less. The results of this study show that functional sports agility programs during the early rehabilitation period after anterior cruciate ligament reconstruction with a correctly placed autogenous patellar tendon graft do not cause a change in graft stability.

The relationship between intercondylar notch width of the femur and the incidence of anterior cruciate ligament tears. A prospective study

For 714 consecutive patients who underwent autogenous patellar tendon graft anterior cruciate ligament reconstructions we intraoperatively measured intercondylar notch width. We prospectively recorded height, weight, sex, and which patients subsequently tore their contralateral anterior cruciate ligament or the 10-mm autograft. The patients were divided into two groups based on notch width (group 1, < or = 15 mm; group 2, > or = 16mm. The mean notch width was 13.9 +/- 2.2 mm for women and 15.9 +/- 2.5 mm for men. There was no statistically significant difference in notch width between height groups for women or men. Analysis showed that, with height and weight as covariates, women had statistically significantly narrower notches than men. Twenty-three of 388 patients in group 1 and 4 of 326 patients in group 2 tore their contralateral anterior cruciate ligaments. Within groups, no statistically significant differences in contralateral tear rates existed between men and women. Once the men and women had reconstructions with equally sized 10-mm autografts, there was no difference in graft tear rate between groups or between men and women. Our results show that patients with narrower notches have a higher incidence of tearing their contralateral anterior cruciate ligament. After reconstruction with a 10-mm autograft, the incidence of graft rupture is the same for men and women.

Colonoscopy experience at a family practice residency: a comparison to gastroenterology and general surgery services

BACKGROUND AND OBJECTIVES

Colonoscopy training is receiving greater emphasis in family practice residencies. However, no standards have been established to measure the adequacy of this training. This study assessed the colonoscopy experience of family practice residents at Louisiana State University Medical Center at Shreveport (LSUMC-S).

METHODS

We included all colonoscopies performed by the family practice service between August 1992 and December 1994 and matched them by gender and age with cases from the gastroenterology (GI) and general surgery (GS) services performed during the same time period. Family practice and GI were compared using 143 cases from each service; 166 cases were used to compare family practice to GS.

RESULTS

The cecum was intubated in 87% of patients on all services. The average time to complete the procedure was 35 minutes by the family practice service, 44 minutes by GI, and 25 minutes by GS. No significant differences were found between family practice and GI in the number of patients with polyp, normal colon, or biopsy performed. In comparison to GS, there were significantly fewer patients on the family practice service with normal colon and more with multiple polyps and biopsy performed. Significantly more cancers were found by the family practice service than by either GI or GS. There were no complications reported for any of the services. Results compared favorably with data in the current literature.

CONCLUSIONS

The colonoscopy experience available to family practice residents at LSUMC-S is acceptable within the parameters studied.

X-ray diffraction imaging using perfect crystals

The imaging properties of perfect crystals, used for controlling and directing x-ray beams in imaging systems, are analyzed using optical transfer functions. The optical transfer functions are related to the point-spread functions for the crystal imaging system and are derived from a one-dimensional Fourier transform of the Takagi-Taupin equations. Images obtained using diffracting crystals as optical elements are simulated for the Laue and Bragg geometries using a Fourier transform method and the imaging characteristics of each of these crystal configurations are analyzed. It is demonstrated that the perfect crystals act as spatial filters of the object wave.

External fixation of pediatric femoral fractures

Fifteen pediatric femoral fractures in 14 patients were treated with external fixation using the EBI Orthofix unilateral external fixator. The average patient age was 8.5 years (range, 3-13 years). There were 7 children with multiple injuries and 7 with isolated fractures. The average duration in the fixator was 63 days; average followup was 34 months. All 15 fractures healed without additional operative intervention. Average angulation at the fracture site was 4.4 degrees in the anteroposterior plane (range, 0 degrees-10 degrees) and 4.6 degrees in the lateral plane (range, 0 degrees-11 degrees). There were 5 pin tract infections, all of which resolved with systemic antibiotics. There was 1 case of refracture in a boy with muscular dystrophy. Ten patients had clinically equal leg lengths, 3 patients had < 1 cm of inequality, and 1 patient had a 1.5 cm discrepancy. External fixation is a well-proven technique for managing pediatric femoral fractures in the child with multiple injuries. It is also an effective means of treating isolated femoral fractures in the pediatric population.

Clinical evaluation of crossed-pin versus lateral-pin fixation in displaced supracondylar humerus fractures

The radiographs and patient charts of 47 children treated with closed reduction and percutaneous pin fixation of displaced supracondylar humerus fractures were reviewed. Twenty-seven fractures were fixed with crossed medial and lateral pins. Twenty fractures were treated with two parallel laterally placed pins. Baumann's angle on the anteroposterior elbow film and the humerocapitellar angle on the lateral elbow film were independently measured by the three authors on initial postoperative films and on films taken at the time of pin removal. No statistically significant differences regarding maintenance of reduction were found when comparing the two fixation groups. There were two complications in the medial pin group (one cubitus varus and one ulnar nerve injury) and none in the lateral-pin group. We conclude that crossed-pin fixation offers no clinically significant advantage over two laterally placed pins in the treatment of supracondylar humerus fractures.

Branches of the tibial nerve: anatomic variations

Anatomic variations in tibial nerve branches may help explain discrepancies between clinical examination and electrophysiologic tests as to the location of neuronal lesions. Dissection of 20 cadaveric feet (10 pair) along the course of the tibial nerve and its branches confirmed that it bifurcates within 2 cm of the medio-malleolar-calcaneal axis in 90% (18/20) and that it gives off frequent small branches with its accompanying vascular structures. Unlike other studies, however, we found that 60% had multiple calcaneal branches off the tibial nerve and that 20% evidenced previously undescribed accessory innervation to the abductor hallucis muscle from other than the medial plantar nerve.

A modified technique for bedside placement of nasoduodenal feeding tubes

A technique for bedside placement of NDT that was used in our ICU and allowed a significant percentage of feeding tubes to be placed in the duodenum without moving the patient from the ICU setting is reported. We believe that this modification for feeding tube placement is effective and safe and represents an improvement of the previous method.

Right coronary ostial atherectomy: a really close shave

Percutaneous transluminal coronary balloon angioplasty (PTCA) has had limited success with higher complication and restenosis rates in aorto-ostial lesions. Directional coronary atherectomy (DCA) has been advocated as an alternative to PTCA in such lesions. In this report, we describe a potential complication of DCA in right coronary ostial lesions.

DuMond Diagram Mappings for Multi Asymmetric Crystal Monochromators

A set of transformation equations is derived to map DuMond diagrams between crystal faces in a multi-crystal system. The equations are constructed from the Bragg equation linearized about some angle and include the effects of refraction and asymmetry of the crystal faces. The equations form the basis of a ray tracing program for x rays to aid in the design of monochromators.

Focusing and collimation of x rays using microchannel plates: an experimental investigation

Focusing and collimation of 8 keV x rays has been demonstrated using microchannel plate (MCP) blanks with cylindrical channels. The focusing effect arises from total external reflection of x rays at the interior surfaces of the channels of a MCP and has been described previously by the authors. Point to point focusing was observed with flat and curved MCPs, and collimation from a point source to a quasi-parallel beam was observed with a curved MCP. Intensity profiles at the image plane and at other planes behind a flat MCP were obtained for a 20 × 40 μm2 x-ray source, and agree well with theoretical predictions. The flux in a 40-μm-diameter collector in the image plane was compared with the flux in the same plane, but without a MCP. The relative gain in flux increases linearly with the source to MCP distance, as predicted. A maximum relative gain in flux of 18 ± 1 was observed for a source to detector distance of 50 cm.

Coarctation of the aorta from a mediastinal germ cell tumor: a case report

A 20-yr-old male had compression of the thoracic aorta by a large malignant mediastinal germinoma. The symptoms and signs that simulated coarctation of the aorta included hypertension, markedly decreased femoral pulses, and a systolic murmur that radiated to the back. Following X-ray therapy, the femoral pulses were palpable and the blood pressure became normal. To our knowledge, compression of the aorta by a malignant teratocarcinoma with manifestations mimicking coarctation of the aorta has not been reported.

Parasitic arterial supply to renal angiomyolipoma

A case of a large renal angiomyolipoma in a relatively asymptomatic female subject without tuberous sclerosis is presented. The case demonstrates a parasitized blood supply from a lumbar artery and the superior mesenteric artery, in addition to the characteristic angiographic features that have been reported previously. A parasitized blood supply to renal masses has been considered previously to be associated with malignant processes. It is emphasized that parasitization of a blood supply by a renal mass lesion is not definite evidence of malignancy.

Benign hepatic lesions in women taking oral contraceptives

Four previously unreported cases of benign hepatic cell lesions in young women taking oral contraceptives are described. A brief review of the literature is presented with emphasis on the clinical symptoms, the findings on angiography and radionuclide scan, and the relation of the lesions to oral contraceptives.

Immunoglobulin deficiency diseases of the intestine

Marshak has emphasized the role of the gastrointestinal tract as a major immunologic organ and described the radiologic findings of immunoglobulin deficiency diseases of the small intestine. According to his classification the radiologic findings include multiple nodular defects, edema and increased secretions associated with Giardiasis, a sprue-like pattern, and thickened folds. In this report, the role of the intestine in the immune response is briefly reviewed and several of the radiologic features of immune deficiency diseases and those of benign nodular lymphoid hyperplasia are illustrated.

Haemoglobin synthesis in fused cells

When primitive erythroid cells from 5-day-old chick embryos are exposed to inactivated Sendai virus they do not undergo haemolysis but fuse with other cells by the normal process of cytoplasmic coalescence. In this way cells actively engaged in the synthesis of haemoglobin may be fused with others that are not. In heterokaryons formed by the fusion of such erythroid cells with cells from established mouse or hamster lines, haemoglobin synthesis initially continues at a high level, but then declines and ceases altogether within a period of about 60 h. This decline affects the synthesis of both haem and globin and reflects the activity of specific regulatory mechanism, for under these conditions other chick proteins continue to be synthesized. The haemoglobin synthesized in the heterokaryons is entirely chick, and not mouse or hamster, haemoglobin.