A De Garengeot Hernia masquerading as a strangulated femoral hernia.

INTRODUCTION: De Garengeot hernia is a rare occurrence whereby an appendix is found in a femoral hernia sac. It is rarer still to find an acutely inflamed appendix manifesting itself as a strangulated femoral hernia. This case is important to report as it highlights the diagnostic difficulty this particular condition presents to an emergency surgeon. PRESENTATION OF CASE: We report the case of an 86 year old female who was found to have a De Garengeot hernia containing a necrotic appendix. A retrograde appendicectomy was performed to prevent peritoneal contamination. The hernia defect was repaired using a standard repair with non-absorbable suture. DISCUSSION: De Garengeot's hernia is a rare occurrence, is often unexpected and tends to be diagnosed intra-operatively. Pre-operative diagnosis remains difficult and it will often masquerade as a strangulated femoral hernia. In stable patients, where there is a diagnostic uncertainty CT scanning is a useful adjunct and may allow a laparoscopic approach to be undertaken in the absence of appendicitis. CONCLUSION: A De Garengeot's hernia should be considered as a differential diagnosis in patients presenting with clinical signs of a strangulated femoral hernia. It is often an incidental finding during an emergency operation. Although mesh repairs in the presence of appendicitis have been reported, the safest approach remains a primary suture repair.

Optical transmission of nematic liquid crystal 5CB doped by single-walled and multi-walled carbon nanotubes.

Comparative studies of optical transmission of single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs), dispersed in nematic liquid crystal matrix 5CB, were carried out. The data evidence violations of Beer-Lambert-Bouguer (BLB) law both in cell thickness and concentration dependencies. The most striking is the fact that optical transmission dependencies for SWCNTs and MWCNTs were quite different in the nematic phase, but they were practically indistinguishable in the isotropic phase. Monte Carlo simulations of the impact of aggregation on direct transmission and violation of BLB law were also done. The results were discussed accounting for the tortuous shape of CNTs, their physical properties and aggregation, as well as strong impact of perturbations of the nematic 5CB structure inside coils and in the vicinity of CNT aggregates.

Dynamic space shaping of intense ultrashort laser light with blazed-type gratings.

A beam shaper for dynamic transversal shaping of broadband laser pulses that utilizes a blazed ruled grating and a blazed-type grating simulated on Spatial Light Modulator was demonstrated. The introduced shaper scheme is an extension of 2f-2f scheme [Mariyenko, et al., Opt. Express 13, 7599 (2005)] where the two thin holograms with matched grating constants performed light shaping. The new scheme utilizes the diffraction gratings with different grating constants. Dispersion-free light shaping is achieved by means of the intermediate transversal light beam magnification. The magnification balances the mismatch in the grating constants resulting in total residual angular dispersion compensation. In turn, the magnified beam covers a greater area on the modulator matrix thus reducing the incident light power density by a value equal to square of the magnification factor. It translates to the safe-operation threshold extension of the modulator allowing shaping pulses that are powerful enough to be used in the applications. With a proper components selection, the throughput efficiency of the shaper can be well above 40%. A proper shaper operation was demonstrated with the 140-fs Ti:Sapphire oscillator. Theoretical calculations support the conclusions.

Observation of superluminal wave-front propagation at the shadow area behind an opaque disk.

We demonstrate in theory and experiment superluminal properties of optical field propagation in the shadow area behind an opaque disk (Poisson's spot). The wave front of the field in the shadow zone is initially delayed with respect to the unperturbed field. This phase shift gradually diminishes along the optical path and therefore ensures variation of the phase velocity of the field at the axis. A resulting excess of about cx10(-5) was detected.

Centrifugal transformation of the transverse structure of freely propagating paraxial light beams.

Superpositions of coaxial Laguerre-Gaussian modes with common waists and the same Gaussian envelopes are known to form beams whose transverse structures experience the self-similar transformation during free beam propagation: the beam shape remains the same except for the divergence and rotation around the propagation axis. We show that under certain conditions this transformation can be represented as if every point of the beam cross section performs a centrifugal straight-line fly off.

Optical vortex symmetry breakdown and decomposition of the orbital angular momentum of light beams.

Two forms of the transverse energy circulation within plane-polarized paraxial light beams are specified: one inherent in wave-front singularities (optical vortices) and the other peculiar to astigmatism and asymmetry of beams with a smooth wave front. As quantitative measures of these energy flow components, the concepts of vortex and asymmetry parts of a beam's orbital angular momentum are introduced and their definitions are proposed on the basis of beam intensity moments. The properties and physical meaning of these concepts are analyzed, and their use for the study of transformations of optical vortices is demonstrated.

Manifestation of the rotational Doppler effect by use of an off-axis optical vortex beam.

We report what is to our knowledge the first all-optical detection of the frequency beats between Gaussian and Laguerre-Gaussian LG0(1) modes in their axial superposition, caused by the rotational Doppler effect. The relation between the observable off-axis optical vortex rotation and the rotational frequency shift of the Laguerre-Gaussian component is ascertained. The results can be used as a physical basis for recognition of Laguerre-Gaussian mode spectra along their orbital angular momenta.

Stokes singularity relations.

Polarization singularities in paraxial vector optical fields are analyzed in terms of the phase singularities of complex Stokes scalar fields. Six independent relationships are obtained that connect the topological charges of these singularities on special closed contours with the charges of singularities that are enclosed by these contours. These relationships, which have been confirmed by experimental data and computer simulations, imply topological polarization correlations of an infinite range.

Elliptic critical points: C-points, a-lines, and the sign rule.

The critical points of generic paraxial ellipse fields consist of singular points of circular polarization, called C -points, and azimuthal stationary points, i.e., maxima, minima, and saddle points. We define these stationary points here and review their properties. The sign rule for ellipse fields requires that the sign of the singularity indices I(C)=+/-1/2 of the C -points on non-self-intersecting lines of constant azimuthal ellipse orientation (modulo pi/2), i.e., a -lines, alternate along the line. We verify this rule experimentally, using a newly developed interferometric technique to measure C -points and a -lines in an elliptically polarized random optical field.

Small is mighty: EmrE, a multidrug transporter as an experimental paradigm.

EmrE is a multidrug transporter from Escherichia coli that functions as a homooligomer and is unique in its small size. In each monomer there are four tightly packed transmembrane segments and one membrane-embedded charged residue. This residue provides the basis for the coupling mechanism as part of a binding site "time shared" by substrates and protons.

Precious things come in little packages.

The 110-amino acid multidrug transporter from E. coli, EmrE, is a member of the family of MiniTexan or Smr drug transporters. EmrE can transport acriflavine, ethidium bromide, tetraphenylphosphonium (TPP+), benzalkonium and several other drugs with relatively high affinities. EmrE is an H+/drug antiporter, utilizing the proton electrochemical gradient generated across the bacterial cytoplasmic membrane by exchanging two protons with one substrate molecule. The EmrE multidrug transporter is unique in its small size and hydrophobic nature. Hydropathic analysis of the EmrE sequence predicts four alpha-helical transmembrane segments. This model is experimentally supported by FTIR studies that confirm the high alpha-helicity of the protein and by high-resolution heteronuclear NMR analysis of the protein structure. The TMS of EmrE are tightly packed in the membrane without any continuous aqueous domain, as was shown by Cysteine scanning experiments. These results suggest the existence of a hydrophobic pathway through which the substrates are translocated. EmrE is functional as a homo-oligomer as suggested by several lines of evidence, including co-reconstitution experiments of wild-type protein with inactive mutants in which negative dominance has been observed. EmrE has only one membrane embedded charged residue, Glu-14, that is conserved in more than fifty homologous proteins and it is a simple model system to study the role of carboxylic residues in ion-coupled transporters. We have used mutagenesis and chemical modification to show that Glu-14 is part of the substrate-binding site. Its role in proton binding and translocation was shown by a study of the effect of pH on ligand binding, uptake, efflux and exchange reactions. We conclude that Glu-14 is an essential part of a binding site, common to substrates and protons. The occupancy of this site is mutually exclusive and provides the basis of the simplest coupling of two fluxes. Because of some of its properties and its size, EmrE provides a unique system to understand mechanisms of substrate recognition and translocation.

Structure of an edge-dislocation wave originating in plane-wave diffraction by a half-plane.

A new treatment of the well-known Sommerfeld solution of the problem of plane-wave diffraction from a perfectly conducting half-plane is reported. We show, in both theory and experiment, that the diffraction field (E-polarization) can be represented as a superposition of real physically existing waves, in contrast to geometrical and boundary waves postulated in Sommerfeld's representation. Our representation includes two pairs of wave components: one pair propagates along the direction of the incident wave, and the other in a mirror-reflected direction. Each wave pair consists of a plane-wave component with an amplitude half that of the incident wave and a nearly plane-wave component with an infinitely extended edge dislocation. On the basis of the proposed interpretation, all features of the half-plane diffraction are explained.

Nonlinear optical catastrophe from a smooth initial beam.

We observed an optical cusp diffraction catastrophe with an initially smooth but elongated Gaussian beam with an aspect ratio of 2:1. Nonlinear and linear diffraction regimes account for the near-field elliptical annulus and the far-field spatially complex astroid.