Volumetric metamaterials versus impedance surfaces in scattering applications

Artificially created media allow employing material parameters as additional valuable degrees of freedom in tailoring electromagnetic scattering. In particular, metamaterials with either negative permeability or permittivity allow creating deeply subwavelength resonant structures with relatively high scattering cross-sections. However, the equivalence principle allows replacing volumetric structures with properly designed curved impedance surfaces, ensuring the same electromagnetic properties. Here, we examine this statement from a practical standpoint, considering two structures, having a dipolar electric resonance at the same frequency. The first realization is based on arrays of inductively loaded electric dipoles printed on stacked circuit boards (a volumetric metamaterial), while the second structure utilizes a 4-wire spiral on a spherical surface (surface impedance realization). An intermediate conclusion is that the surface implementation tends to outperform the volumetric counterparts in the scenario when a single resonance is involved. However, in the case where multiple resonances are overlapping and lossy materials are involved, volumetric realization can have an advantage. The discussed structures are of significant importance to the field of electrically small antennas, superdirective antennas, and superscatterers, which find use in wireless communications and radar applications, to name just a few.

Complications associated with bone marrow sampling in dogs and cats

OBJECTIVES

To evaluate the prevalence of complications during bone marrow sampling and associated patient and procedural factors in dogs and cats.

MATERIALS AND METHODS

Retrospective cohort study, records were evaluated to identify dogs and cats that had bone marrow sampling between 2012 and 2019. Data including signalment, the presence of specific clinicopathological findings, anatomical site of bone marrow sampling, number of attempts, diagnostic quality of sampling, analgesia protocol and complications postprocedure were recorded.

RESULTS

A total of 131 dogs and 29 cats were included in the study. Complications were recorded in 22 of 160 (14%) of cases. Pain was the most common complication of bone marrow sampling in 20 of 22 (91%) of cases with bruising reported in the remaining patients. A local anaesthetic block was used in 98 of 160 (61%) of patients.

CLINICAL SIGNIFICANCE

Excluding pain, complications associated with bone marrow sampling were rare and no clear association were detected between patient or procedural variables. Haemorrhage and infection are rare complications in dogs and cats when thrombocytopenia and neutropenia are present. Peri-procedure analgesia is strongly recommended to minimise complications.

Meta-hologram-based authentication scheme employing a speckle pattern fingerprint

A concept for an optical holographic security tag is proposed and demonstrated. When illuminated with a laser beam, the image scattered from the tag projects a Quick Response code which encodes identifying information. The image also carries pseudorandom speckle noise, from which a unique speckle pattern "fingerprint" is derived. We show numerically that the tag is unclonable without access to a secret key - the starting conditions of the design algorithm. However, given the key, it is straightforward to reproduce a tag exhibiting the expected fingerprint. Several tags have been realized, implemented as plasmonic meta-holograms, and characterized experimentally. The robustness of the tag to fabrication error and its resilience to counterfeiting are studied in detail and demonstrated experimentally.

Quantum noise radar: superresolution with quantum antennas by accessing spatiotemporal correlations

We suggest overcoming the "Rayleigh catastrophe" and reaching superresolution for imaging with both spatially and temporally correlated field of a superradiant quantum antenna. Considering far-field radiation of two interacting spontaneously emitting two-level systems, we show that for the measurement of the temporally delayed second-order correlation function of the scattered field, the Fisher information does not tend to zero with diminishing the distance between a pair of scatterers even for non-sharp time-averaged detection. For position estimation of more scatterers, the measurement of the time-delayed function is able to provide a considerable accuracy gain over the zero-delayed function. We also show that the superresolution with the considered quantum antenna can be achieved for both near-field imaging and for estimating the antenna parameters.

Epidemiology of road traffic accidents in cats attending emergency-care practices in the UK

OBJECTIVES

To estimate the incidence proportion of road traffic accidents in cats attending emergency out-of-hours clinics in the UK, identify major risk factors for road traffic accident occurrence and for survival to discharge.

MATERIALS AND METHODS

A retrospective study of a cohort of 33,053 cats in the VetCompass database attending emergency-care practice between January 1, 2012 and February 15, 2014. Incidence proportion was calculated and logistic regression was used to identify risk factors for road traffic accident and survival to discharge following road traffic accident.

RESULTS

Incidence proportion was estimated at 4∙2% (95% confidence interval: 4∙0 to 4∙4%). Cats aged 6 months to 2 years were at increased odds of road traffic accident, as were male cats and crossbred cats. Odds of road traffic accident were highest in the autumn. Spinal injury, abdominal injury and increasing count of injuries were associated with increased odds of death.

CLINICAL SIGNIFICANCE

Road traffic accident is a frequent presentation in emergency-care practice. Identification of risk factors for death within the first 24 hours following a road traffic accident can aid veterinarian and owner decision-making for treatment of cats involved in a road traffic accident.

Coagulation status in dogs with naturally occurring Angiostrongylus vasorum infection

OBJECTIVES

Angiostrongylus vasorum infection is associated with bleeding tendencies in approximately one-third of clinical cases. The cause of the coagulopathy is poorly understood but may be related to disseminated intravascular coagulation. Thromboelastography is a global evaluation of coagulation and has not been described in a cohort of dogs with this disease.

MATERIALS AND METHODS

Thromboelastography in association with other measures of coagulation including prothrombin and activated partial thromboplastin times, antithrombin percentage activity and D-dimer and von Willebrand factor concentrations was evaluated in a group of 30 dogs with A. varosum infection.

RESULTS

A total of 18 dogs had signs of bleeding on physical examination. Thromboelastography was consistent with hypocoagulation in 17 of these dogs. There was no association between any of the other measures and hypocoagulation on thromboelastography. Abnormal coagulation times were not significantly associated with bleeding. Only fibrinogen concentration was significantly lower in dogs that were bleeding compared with those that were not (P = 0 · 026). D-dimer concentrations were increased in 22/25 cases in the study; however, other coagulation parameters were more variable.

CLINICAL SIGNIFICANCE

Although the changes identified in this study were not consistent, there is activation of coagulation within this population, possibly consistent with an intravascular disseminated coagulopathy.

Reconstruction of surface potential from Kelvin probe force microscopy images

We present an algorithm for reconstructing a sample surface potential from its Kelvin probe force microscopy (KPFM) image. The measured KPFM image is a weighted average of the surface potential underneath the tip apex due to the long-range electrostatic forces. We model the KPFM measurement by a linear shift-invariant system where the impulse response is the point spread function (PSF). By calculating the PSF of the KPFM probe (tip+cantilever) and using the measured noise statistics, we deconvolve the measured KPFM image to obtain the surface potential of the sample.The reconstruction algorithm is applied to measurements of CdS-PbS nanorods measured in amplitude modulation KPFM (AM-KPFM) and to graphene layers measured in frequency modulation KPFM (FM-KPFM). We show that in the AM-KPFM measurements the averaging effect is substantial, whereas in the FM-KPFM measurements the averaging effect is negligible.

Direct measurement of individual deep traps in single silicon nanowires

The potential of the metal nanocatalyst to contaminate vapor-liquid-solid (VLS) grown semiconductor nanowires has been a long-standing concern, since the most common catalyst material, Au, is known to induce deep gap states in several semiconductors. Here we use Kelvin probe force microscopy to image individual deep acceptor type trapping centers in single undoped Si nanowires grown with an Au catalyst. The switching between occupied and empty trap states is reversibly controlled by the back-gate potential in a nanowire transistor. The trap energy level, i.e., E(C) - E(T) = 0.65 ± 0.1 eV was extracted and the concentration was estimated to be ∼2 × 10(16) cm(-3). The energy and concentration are consistent with traps resulting from the unintentional incorporation of Au atoms during the VLS growth.

Evaluation of surface contamination with staphylococci in a veterinary hospital using a quantitative microbiological method

OBJECTIVES

To evaluate microbial contamination of the environment in a veterinary hospital using standards recommended for human hospitals and to provide a baseline against which further investigations can be compared.

METHODS

Surfaces were sampled twice daily for five consecutive days using a contact-based counting method to measure the levels of staphylococci in colony forming units (cfu) per cm².

RESULTS

Current recommendations for human hospitals were applied in this study; all samples with <2.5 cfu/cm² staphylococci were considered to have passed and those with ≥2.5 cfu/cm² to have failed. Of all the samples, 55.9% failed. The ICU did not have significantly higher failure rates than other areas of the hospital. The floor as a surface was associated with greater than a threefold increase in odds of elevated cfu concentrations relative to the door handle.

CLINICAL SIGNIFICANCE

This study provides information on the microbiological cleanliness of a veterinary teaching hospital using techniques and standards adopted by the food industry and recommended for human hospitals. This data can be used as a baseline for other hospitals, to evaluate the effectiveness in improvements in hygiene and cleaning measures and to design effective hospital cleaning protocols and assess ongoing hygiene standards.

Discrete Fourier analysis of ultrasound RF time series for detection of prostate cancer

In this paper, we demonstrate that a set of six features extracted from the discrete Fourier transform of ultrasound Radio-Frequency (RF) time series can be used to detect prostate cancer with high sensitivity and specificity. Ultrasound RF time series refer to a series of echoes received from one spatial location of tissue while the imaging probe and the tissue are fixed in position. Our previous investigations have shown that at least one feature, fractal dimension, of these signals demonstrates strong correlation with the tissue microstructure. In the current paper, six new features that represent the frequency spectrum of the RF time series have been used, in conjunction with a neural network classification approach, to detect prostate cancer in regions of tissue as small as 0.03 cm2. Based on pathology results used as gold standard, we have acquired mean accuracy of 91%, mean sensitivity of 92% and mean specificity of 90% on seven human prostates.

Thirteen cases of tetanus in dogs

The records of 13 dogs with tetanus were reviewed, 12 of the dogs survived and were discharged, but the other died as a result of the acute onset of hyperthermia. Long-term follow up was available for 10 of the survivors of which nine were reported to be normal. One case was euthanased after a cervical spine fracture four months after it was discharged. Complications encountered during management included aspiration pneumonia in three cases, urinary tract infection in two cases, and upper respiratory tract obstruction, hiatal hernia, coxofemoral luxation, seizures and respiratory arrest in one case each. None of the dogs required ventilatory support, and the complications were managed successfully. The dogs were nursed intensively and monitored carefully.

Brain and spinal cord haemorrhages associated with Angiostrongylus vasorum infection in four dogs

Multifocal haemorrhages associated with Angiostrongylus vasorum infection were observed in the central nervous system of four dogs with neurological signs including depression, seizures, spinal pain and paresis. In magnetic resonance images the majority of the lesions were isointense or slightly hyperintense in T1-weighted images, hyperintense in T2-weighted images and hypointense in T2*-weighted (gradient echo) images, compatible with haemorrhages more than seven days old. Lesions were found in the brain of three of the dogs and in the spinal cord of two. The cerebrospinal fluid contained high concentrations of protein and evidence of erythrophagia. All the dogs had coagulopathy and pulmonary haemorrhage of varying severity. A vasorum larvae were detected in the faeces of each of the dogs. Neural A vasorum was confirmed at postmortem examination in two dogs.

6-mercaptopurine and inflammatory bowel disease: hidden ground for the cytomegalovirus

6-mercaptopurine (6-MP) and azathioprine are important drugs for the treatment of inflammatory bowel disease (IBD) but their actions suppress host defense against infection. A challenging case of a 19-year-old female patient with quiescent Crohn's disease maintained with 6-MP presenting with dyspnea and a normal chest exam and x-ray is presented. She became ventilator-dependent and only after numerous investigations was diagnosed with cytomegalovirus (CMV) pneumonitis. A systematic literature review of CMV infections in IBD patients was performed. The present case is the first report of a patient with quiescent IBD maintained on 6-MP who developed CMV pneumonitis. Other reports have identified patients with active disease on multiple immunosuppressants who developed CMV pneumonitis and also highlight the risk of CMV colitis in refractory IBD. The authors review the approach to the diagnosis of CMV infections in IBD patients with atypical pneumonia and colitis and highlight the importance of considering CMV infection in these settings.

Narrow-band microcavity waveguides in photonic crystals

A novel device, formed by a widely spaced periodic array of defects in a photonic bandgap crystal, is studied with the goal of designing a waveguide with a prescribed narrow bandwidth. Tunneling of radiation between the defect sites allows wave propagation along the line of the defects. An analytical study based on the weakly coupled cavity model is performed, and the dispersion relation omega(beta) of the new waveguide is derived. The frequency shift and the band structure of the periodic defect waveguide are linked by an analytic relationship to the distance between the defect sites and therefore can be tuned by varying the latter. Sections of such waveguides can be employed as ultra-narrow-band filters in optical routing devices. Numerical simulations demonstrate the performances of this new device and support the analytical predictions.

A multilevel domain decomposition algorithm for fast O(N2logN) reprojection of tomographic images

A novel algorithm for fast computation of tomographic image projections is presented. The method comprises a decomposition of an image into subimages followed by an aggregation of projections computed for the subimages. The multilevel domain decomposition algorithm is formulated as a recursive procedure. The computational cost of the proposed algorithm is comparable to that of FFT-based techniques while it appears to be more flexible than the latter. Numerical results demonstrate the effectiveness of the method.

Coexpression of hepatocyte growth factor and receptor (Met) in human breast carcinoma

Expression of hepatocyte growth factor (HGF) and HGF receptor (HGFR, product of the met proto-oncogene) mRNA were examined by nonisotopic in situ hybridization in a spectrum of benign and malignant human breast tissues. mRNA for both HGFR and HGF was detected in benign ductal epithelium. Epithelial expression of HGF mRNA was particularly intense in regions of ductal epithelial hyperplasia. Positive expression of HGF (but not HGFR) mRNA was also found in adipocytes, endothelial cells, and to varying degrees in stromal fibroblasts. In 12 of 12 cases of ductal carcinoma in situ and infiltrating ductal carcinoma, carcinoma cells showed a heterogeneous pattern of expression for both HGFR and HGF mRNA. In infiltrating ductal carcinomas, intense expression of HGFR mRNA was not restricted to ductular structures but as also seen in non-duct-forming carcinoma cells. The same zones of the tumors (most commonly at the advancing margins) that expressed strongly HGFR mRNA often were also strongly positive for HGF mRNA, suggesting a possible autocrine effect. The expression pattern of HGFR protein in 25 cases including the same series of tissues used for in situ hybridization analysis was similar to that of HGFR mRNA, as determined by an immunoperoxidase technique. The finding that HGFR is expressed by both benign and malignant epithelium, and its not restricted to duct-forming structures, suggests that, although the potential for HGF/HGFR binding is maintained in malignancy, the response to ligand binding at the level of the receptor or the cellular response to receptor activation may change at some point during progression.

Analysis and optimization of waveguide multiapplicator hyperthermia systems

A method is proposed for determining the excitation coefficients of an antenna array operating in a large rectangular waveguide and used as a hyperthermia system. The excitation coefficients of the array elements are optimized for attaining an improved specific absorption rate (SAR) distribution around a deep-seated tumor. The method is applied to a two-dimensional problem of a piecewise homogeneous post in a waveguide representing a section of the human torso. The array is operating below the cutoff frequency of the dominant mode of the waveguide. Numerical simulations have been performed to check the effectiveness of this approach. The results show that by using the proposed optimization method, SAR distributions can be improved.

Optimal excitation of multiapplicator systems for deep regional hyperthermia

A method is proposed for determining the excitation amplitudes and phases of the elements of electromagnetic multiapplicator systems for optimizing the specific absorption rate (SAR) distribution around a deep-seated tumor. In this method, the ratio of the power dissipated in the tumor to a weighted summation of the powers supplied to the surrounding regions is optimized. The optimization procedure is combined with a recently proposed effective technique for analysis of various electromagnetic scattering and interaction problems. The general principle is applied to a two-dimensional problem of a piecewise homogeneous cylinder heated by an array of electric current filaments placed outside the cylinder. Numerical simulations are performed to check the effectiveness of the approach. The results demonstrate that using this optimization method, improved SAR distributions can be achieved. The extension to three-dimensional configurations is discussed.

Analysis of acoustic scattering from fluid bodies using a multipoint source model

A moment-method solution is presented for the problem of acoustic scattering from homogeneous fluid bodies. It uses fictitious isotropic point sources to simulate both the field scattered by the body and the field inside the body and, in turn, point-matches the continuity conditions for the normal component of the velocity and for the pressure across the surface of the body. The procedure is simple to execute and is general in that bodies of arbitrary smooth shape can be handled effectively. Perfectly rigid bodies are treated as reduced cases of the general procedure. Results are given and compared with available analytic solutions, which demonstrate the very good performance of the procedure.