Axion Wind Detection with the Homogeneous Precession Domain of Superfluid Helium-3.

Axions and axionlike particles may couple to nuclear spins like a weak oscillating effective magnetic field, the "axion wind." Existing proposals for detecting the axion wind sourced by dark matter exploit analogies to nuclear magnetic resonance (NMR) and aim to detect the small transverse field generated when the axion wind resonantly tips the precessing spins in a polarized sample of material. We describe a new proposal using the homogeneous precession domain of superfluid ^{3}He as the detection medium, where the effect of the axion wind is a small shift in the precession frequency of a large-amplitude NMR signal. We argue that this setup can provide broadband detection of multiple axion masses simultaneously and has competitive sensitivity to other axion wind experiments such as CASPEr-Wind at masses below 10^{-7} eV by exploiting precision frequency metrology in the readout stage.

Ionic Strength and Solution Composition Dictate the Adsorption of Cell-Penetrating Peptides onto Phosphatidylcholine Membranes.

Adsorption of arginine-rich positively charged peptides onto neutral zwitterionic phosphocholine (PC) bilayers is a key step in the translocation of those potent cell-penetrating peptides into the cell interior. In the past, we have shown both theoretically and experimentally that polyarginines adsorb to the neutral PC-supported lipid bilayers in contrast to polylysines. However, comparing our results with previous studies showed that the results often do not match even at the qualitative level. The adsorption of arginine-rich peptides onto 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) may qualitatively depend on the actual experimental conditions where binding experiments have been performed. In this work, we systematically studied the adsorption of R9 and K9 peptides onto the POPC bilayer, aided by molecular dynamics (MD) simulations and fluorescence cross-correlation spectroscopy (FCCS) experiments. Using MD simulations, we tested a series of increasing peptide concentrations, in parallel with increasing Na+ and Ca2+ salt concentrations, showing that the apparent strength of adsorption of R9 decreases upon the increase of peptide or salt concentration in the system. The key result from the simulations is that the salt concentrations used experimentally can alter the picture of peptide adsorption qualitatively. Using FCCS experiments with fluorescently labeled R9 and K9, we first demonstrated that the binding of R9 to POPC is tighter by almost 2 orders of magnitude compared to that of K9. Finally, upon the addition of an excess of either Na+ or Ca2+ ions with R9, the total fluorescence correlation signal is lost, which implies the unbinding of R9 from the PC bilayer, in agreement with our predictions from MD simulations.

Quantitative Ultrasound Assessment of Hepatic Steatosis.

Background/Aims: Non-alcoholic fatty liver disease (NAFLD) is widespread chronic disease of the live in humans with the prevalence of 30% of the United States population.1,2 The goal of the study is to validate the performance of quantitative ultrasound algorithms in the assessment of hepatic steatosis in patients with suspected NAFLD. Methods: This prospective study enrolled a total of 31 patients with clinical suspicion of NAFLD to receive liver fat measurements by quantitative ultrasound and reference MRI measurements (proton density fat-fraction, PDFF). The following ultrasound (US) parameters based on both raw ultrasound RF (Radio Frequency) data and 2D B-mode images of the liver were analyzed with subsequent correlation with MRI-PDFF: hepatorenal index, acoustic attenuation coefficient, Nakagami coefficient parameter, shear wave viscosity, shear wave dispersion and shear wave elasticity. Ultrasound parameters were also correlated with the presence of hypertension and diabetes. Results: The mean (± SD) age and body mass index of the patients were 49.03 (± 12.49) and 30.12 (± 6.15), respectively. Of the aforementioned ultrasound parameters, the hepatorenal index and acoustic attenuation coefficient showed a strong correlation with MRI-PDFF derivations of hepatic steatosis, with r-values of 0.829 and 0.765, respectively. None of the remaining US parameters showed strong correlations with PDFF. Significant differences in Nakagami parameters and acoustic attenuation coefficients were found in those patients with and without hypertension. Conclusions: Hepatorenal index and acoustic attenuation coefficient correlate well with MRI-PDFF-derived measurements of hepatic steatosis. Quantitative ultrasound is a promising tool for the diagnosis and assessment of patients with NAFLD.

Contributions to the biodiversity of Vietnam - Results of VIETBIO inventory work and field training in Cuc Phuong National Park.

VIETBIO [Innovative approaches to biodiversity discovery and characterisation in Vietnam] is a bilateral German-Vietnamese research and capacity building project focusing on the development and transfer of new methods and technology towards an integrated biodiversity discovery and monitoring system for Vietnam. Dedicated field training and testing of innovative methodologies were undertaken in Cuc Phuong National Park as part and with support of the project, which led to the new biodiversity data and records made available in this article collection. VIETBIO is a collaboration between the Museum für Naturkunde Berlin - Leibniz Institute for Evolution and Biodiversity Science (MfN), the Botanic Garden and Botanical Museum, Freie Universität Berlin (BGBM) and the Vietnam National Museum of Nature (VNMN), the Institute of Ecology and Biological Resources (IEBR), the Southern Institute of Ecology (SIE), as well as the Institute of Tropical Biology (ITB); all Vietnamese institutions belong to the Vietnam Academy of Science and Technology (VAST). The article collection "VIETBIO" (https://doi.org/10.3897/bdj.coll.63) reports original results of recent biodiversity recording and survey work undertaken in Cuc Phuong National Park, northern Vietnam, under the framework of the VIETBIO project. The collection consist of this "main" cover paper - characterising the study area, the general project approaches and activities, while also giving an extensive overview on previous studies from this area - followed by individual papers for higher taxa as studied during the project. The main purpose is to make primary biodiversity records openly available, including several new and interesting findings for this biodiversity-rich conservation area. All individual data papers with their respective primary records are expected to provide useful baselines for further taxonomic, phylogenetic, ecological and conservation-related studies on the respective taxa and, thus, will be maintained as separate datasets, including separate GUIDs also for further updating.

Gated Transmit and Fresnel-Based Receive Beamforming With a Phased Array for Low-Cost Ultrasound Imaging.

Low-cost ultrasound imaging systems are desired for many applications outside of radiology and cardiology departments. By making ultrasound systems smaller and lower cost, the use of ultrasound has spread from these mainstays to other areas of the hospital such as emergency departments and critical care. To further miniaturize and reduce the cost of ultrasound systems, we have investigated novel Fresnel-based beamforming methods to reduce front-end hardware requirements. Previous studies with linear and curvilinear arrays demonstrated comparable imaging performance using Fresnel-based beamforming versus delay-and-sum (DAS) beamforming. In this work, we extend Fresnel-based beamforming to phased arrays with beam steering. To accomplish this in transmit mode, we introduce a technique called a gated transmit beamformer where multicycle bursts are gated using multiplexers. In receive mode, a 64-element 2.5-MHz phased array is broken up into four 16-element subapertures, and each subaperture performs Fresnel beamforming before a final beamforming step is done. Timing errors are inevitable with Fresnel-based beamforming leading to higher sidelobe and clutter levels. To suppress sidelobe and clutter contributions, we also combine this with our previous technique, dual apodization with cross correlation (DAX) to improve contrast. Field II simulations are performed to evaluate spatial resolution and contrast-to-noise ratio and compared to standard DAS beamforming. Fresnel-based and gated transmit beamforming is also implemented using synthetic aperture data from tissue-mimicking phantoms. Lastly, a hardware proof-of-concept (PoC) Fresnel beamformer was designed, assembled, and evaluated with images from tissue-mimicking phantoms and initial in vivo images.

Resolving the Equal Number Density Puzzle: Molecular Picture from Simulations of LiCl(aq) and NaCl(aq).

The change in number densities of aqueous solutions of alkali chlorides should be qualitatively predictable. Typically, as cations get larger, the number density of the solution decreases. However, aqueous solutions of lithium and sodium chloride exhibit at ambient conditions practically identical number densities at equal molalities despite different ionic sizes. Here, we provide an atomistic interpretation of this experimentally observed anomalous behavior using molecular dynamics simulations. The obtained results show that the rigidity of the Li+ first and second solvation shells and the associated compromised hydrogen bonding result in practically equal average water densities in the local hydration regions for Li+ and Na+ despite different sizes of the cations. In addition, in more distant regions from the cations, the water densities of these two solutions also coincide. These findings thus provide an atomistic interpretation for matching number densities of LiCl and NaCl solutions. In contrast, the number density differences between NaCl and KCl solutions as well as between LiCl and KCl solutions behave in a regular fashion with lower number densities of solutions observed for larger cations.

Multi-Focus Beamforming for Thermal Strain Imaging Using a Single Ultrasound Linear Array Transducer.

Ultrasound-induced thermal strain imaging (TSI) has been used successfully to identify lipid- and water-based tissues in atherosclerotic plaques in some research settings. However, TSI faces several challenges to be realized in clinics. These challenges include motion artifacts and displacement tracking accuracy, as well as limited heating capability, which contributes to low thermal strain signal-to-noise ratio, and a limited field of view. Our goal was to address the challenge in heating tissue in TSI. Current TSI systems use separate heating and imaging transducers, which require physical alignment of the heating and imaging beams and result in a bulky setup that limits in vivo operation. We evaluated a new design for heating beams that can be implemented on a linear array imaging transducer and can provide improved heating area and efficiency as compared with previous implementations. The heating beams designed were implemented with a clinical linear array imaging transducer connected to a research ultrasound platform. In vitro experiments using tissue-mimicking phantoms with no blood flow revealed that the new design resulted in an effective heating area of approximately 0.85 cm2 and a 0.3°C temperature rise in 2 s of heating, which compared well with in silico finite-element simulations. With the new heating beams, TSI was found to be able to detect a lipid-mimicking rubber inclusion with a diameter of 1 cm from the water-based gelatin background, with a strain contrast of 2.3 (+0.14% strain in the rubber inclusion and -0.06% strain in the gelatin background). Lastly, lipid-based tissue in a 1-cm-diameter human carotid endarterectomy (CEA) sample was identified in good agreement with histology.

A systematic review on the global occurrence of Taenia hydatigena in pigs and cattle.

Taenia hydatigena, a non-zoonotic tapeworm species shares the same intermediate hosts with other Taenia zoonotic species, such as Taenia solium in pigs and Taenia saginata in cattle. The occurrence of T. hydatigena in pigs and cattle may cause cross-reactions in immunodiagnostic tests and therefore, complicate the diagnosis of the zoonotic species. This study was conducted to systematically review the data on the prevalence of T. hydatigena in pigs and cattle, with the aim to assess the potential interference in serological diagnosis of zoonotic Taenia spp. due to T. hydatigena infection. We searched PubMed, Web of Science, Africa Journal Online, website http://www.google.com and article reference lists in English, French and Vietnamese with no restriction on research time and publication status. Eligible studies included observational studies that showed the occurrence of T. hydatigena. Twenty-six studies, divided into two animal groups, i.e. pigs and cattle, met the eligibility criteria for qualitative synthesis and 17 studies were included for the meta-analysis in three continents. T. hydatigena was found by necropsy in all included studies, which mostly were abattoir surveys. Overall, results showed the worldwide occurrence of T. hydatigena cysticercosis in pigs and cattle. In pigs, there was a marked higher prevalence in Asia and South America that was 17.2% (95% CI: 10.6-26.8%) and 27.5% (CI: 20.8-35.3%), respectively, compared to a low prevalence of 3.9% (95% CI: 1.9-7.9%) in Africa. Overall, the prevalence of T. hydatigena in cattle was low with a mean of 1.1% (95% CI: 0.2-5.2%). These results show that interpretation of results of sero-diagnostic tests for zoonotic Taenia species in pigs and cattle has to take into account the prevalence of T. hydatigena infections in different settings.

Improved Estimation of Ultrasound Thermal Strain Using Pulse Inversion Harmonic Imaging.

Thermal (temporal) strain imaging (TSI) is being developed to detect the lipid-rich core of atherosclerotic plaques and presence of fatty liver disease. However, the effects of ultrasonic clutter on TSI have not been considered. In this study, we evaluated whether pulse inversion harmonic imaging (PIHI) could be used to improve estimates of thermal (temporal) strain. Using mixed castor oil-gelatin phantoms of different concentrations and artificially introduced clutter, we found that PIHI improved the signal-to-noise ratio of TSI by an average of 213% or 52.1% relative to 3.3- and 6.6-MHz imaging, respectively. In a phantom constructed using human liposuction fat in the presence of clutter, the contrast-to-noise ratio was degraded by 35.1% for PIHI compared with 62.4% and 43.7% for 3.3- and 6.6-MHz imaging, respectively. These findings were further validated using an ex vivo carotid endarterectomy sample. PIHI can be used to improve estimates of thermal (temporal) strain in the presence of clutter.

Harmonic imaging with fresnel beamforming in the presence of phase aberration.

Fresnel beamforming is a beamforming method with a delay profile similar in shape to a physical Fresnel lens. The advantage of Fresnel beamforming is the reduced channel count, which consists of four to eight transmit and two analog-to-digital receive channels. Fresnel beamforming was found to perform comparably to conventional delay-and-sum beamforming. However, the performance of Fresnel beamforming is highly dependent on focal errors. These focal errors result in high side-lobe levels and further reduce the performance of Fresnel beamforming in the presence of phase aberration. With the advantages of lower side-lobe levels and suppression of aberration effects, harmonic imaging offers an effective solution to the limitations of Fresnel beamforming. We describe the implementation of tissue harmonic imaging and pulse inversion harmonic imaging in Fresnel beamforming, followed by dual apodization with cross-correlation, to improve image quality. Compared with conventional delay-and-sum beamforming, experimental results indicated contrast-to-noise ratio improvements of 10%, 49% and 264% for Fresnel beamforming using tissue harmonic imaging in the cases of no aberrator, 5-mm pork aberrator and 12-mm pork aberrator, respectively. These improvements were 22%, 57% and 352% for Fresnel beamforming using pulse inversion harmonic imaging. Moreover, dual apodization with cross-correlation was found to further improve the contrast-to-noise ratios in all cases. Harmonic imaging was also found to narrow the lateral beamwidth and shorten the axial pulse length by at least 25% and 21%, respectively, for Fresnel beamforming at different aberration levels. These results suggest the effectiveness of harmonic imaging in improving image quality for Fresnel beamforming, especially in the presence of phase aberration. Even though this combination of Fresnel beamforming and harmonic imaging does not outperform delay-and-sum beamforming combined with harmonic imaging, it provides the benefits of reduced channel count and potentially reduced cost and size of ultrasound systems.

Development of oil-in-gelatin phantoms for viscoelasticity measurement in ultrasound shear wave elastography.

Because tissues consist of solid and fluid materials, their mechanical properties should be characterized in terms of both elasticity and viscosity. Although the elastic properties of tissue-mimicking phantoms have been extensively studied and well characterized in commercially available phantoms, their viscous properties have not been fully investigated. In this article, a set of 14 tissue-mimicking phantoms with different concentrations of gelatin and castor oil were fabricated and characterized in terms of acoustic and viscoelastic properties. The results indicate that adding castor oil to gelatin phantoms decreases shear modulus, but increases shear wave dispersion. For 3% gelatin phantoms containing 0%, 10%, 20% and 40% oil, the measured shear moduli are 2.01 ± 0.26, 1.68 ± 0.25, 1.10 ± 0.22 and 0.88 ± 0.17 kPa, and the Voigt-model coupled shear viscosities are 0.60 ± 0.11, 0.89 ± 0.07, 1.05 ± 0.11 and 1.06 ± 0.13 Pa·s, respectively. The results also confirm that increasing the gelatin concentration increases shear modulus. For phantoms containing 3%, 4%, 5%, 6% and 7% gelatin, the measured shear moduli are 2.01 ± 0.26, 3.10 ± 0.34, 4.18 ± 0.84, 8.05 ± 1.00 and 10.24 ± 1.80 kPa at 0% oil and 1.10 ± 0.22, 1.97 ± 0.20, 3.13 ± 0.63, 4.60 ± 0.60 and 8.43 ± 1.39 kPa at 20% oil, respectively. The phantom recipe developed in this study can be used in validating ultrasound shear wave elastography techniques for soft tissues.

Performance improvement of Fresnel beamforming using dual apodization with cross-correlation.

Fresnel beamforming is a beamforming method that has a delay profile with a shape similar to a physical Fresnel lens. With 4 to 8 transmit channels, 2 receive channels, and a network of single-pole/single-throw switches, Fresnel beamforming can reduce the size, cost, and complexity of a beamformer. The performance of Fresnel beamforming is highly dependent on focal errors resulting from phase wraparound and quantization of its delay profile. Previously, we demonstrated that the performance of Fresnel beamforming relative to delayand- sum (DAS) beamforming is comparable for linear arrays at f-number = 2 and 50% bandwidth. However, focal errors for Fresnel beamforming are larger because of larger path length differences between elements, as in the case of curvilinear arrays compared with linear arrays. In this paper, we present the concept and performance evaluation of Fresnel beamforming combined with a novel clutter suppression method called dual apodization with cross-correlation (DAX) for curvilinear arrays. The contrast-to-noise ratios (CNRs) of Fresnel beamforming followed by DAX are highest at f-number = 3. At f-number = 3, the experimental results show that using DAX, the CNR for Fresnel beamforming improves from 3.7 to 10.6, compared with a CNR of 5.2 for DAS beamforming. Spatial resolution is shown to be unaffected by DAX. At f-number = 3, the lateral beamwidth and axial pulse length for Fresnel beamforming with DAX are 1.44 and 1.00 mm larger than those for DAS beamforming (about 14% and 21% larger), respectively. These experimental results are in good agreement with simulation results.

A 5-MHz cylindrical dual-layer transducer array for 3-D transrectal ultrasound imaging.

Two-dimensional transrectal ultrasound (TRUS) is being used in guiding prostate biopsies and treatments. In many cases, the TRUS probes are moved manually or mechanically to acquire volumetric information, making the imaging slow, user dependent, and unreliable. A real-time three-dimensional (3-D) TRUS system could improve reliability and volume rates of imaging during these procedures. In this article, the authors present a 5-MHz cylindrical dual-layer transducer array capable of real-time 3-D transrectal ultrasound without any mechanically moving parts. Compared with fully sampled 2-D arrays, this design substantially reduces the channel count and fabrication complexity. This dual-layer transducer uses PZT elements for transmit and P[VDF-TrFE] copolymer elements for receive, respectively. The mechanical flexibility of both diced PZT and copolymer makes it practical for transrectal applications. Full synthetic aperture 3-D data sets were acquired by interfacing the transducer with a Verasonics Data Acquisition System. Offline 3-D beamforming was then performed to obtain volumes of two wire phantoms and a cyst phantom. Generalized coherence factor was applied to improve the contrast of images. The measured -6-dB fractional bandwidth of the transducer was 62% with a center frequency of 5.66 MHz. The measured lateral beamwidths were 1.28 mm and 0.91 mm in transverse and longitudinal directions, respectively, compared with a simulated beamwidth of 0.92 mm and 0.74 mm.

7.5 MHz dual-layer transducer array for 3-D rectilinear imaging.

The difficulties associated with fabrication and interconnection have limited the development of 2-D ultrasound transducer arrays with a large number ofelements (>5000). In previous work, we described a 5 MHz center frequency PZT-P[VDF-TrFE] dual-layer transducer that used two perpendicular 1-D arrays for 3-D rectilinear imaging. This design substantially reduces the channel count as well as fabrication complexity, which makes 3-D imaging more realizable. Higher frequencies (>5 MHz) are more commonly used in clinical applications or imaging targets near transducers, such as the breast, carotid and musculoskeletal tissue. In this paper, we present a 7.5 MHz dual-layer transducer array for 3-D rectilinear imaging. A modified acoustic stack model was designed and fabricated. PZT elements were sub-diced to eliminate lateral coupling. This sub-dicing process made the PZT into a 2-2 composite material, which could help improve transducer sensitivity and bandwidth. Full synthetic-aperture 3-D data sets were acquired by interfacing the transducer with a Verasonics data-acquisition system (VDAS). Offline 3-D beamforming was then performed to obtain volumes of a multiwire phantom and a cyst phantom. The generalized coherence factor (GCF) was applied to improve the contrast of cyst images. The measured -6 dB fractional bandwidth of the transducer was 71% with a center frequency of 7.5 MHz. The measured lateral beamwidths were 0.521 mm and 0.482 mm in azimuth and elevation, respectively, compared with a simulated beamwidth of 0.43 mm.

Fresnel-based beamforming for low-cost portable ultrasound.

In this paper, we propose a modified electronic Fresnel-based beamforming method for low-cost portable ultrasound systems. This method uses a unique combination of analog and digital beamforming methods. Two versions of Fresnel beamforming are presented in this paper: 4-phase (4 different time delays or phase shifts) and 8-phase (8 different time delays or phase shifts). The advantage of this method is that a system with 4 to 8 transmit channels and 2 receive channels with a network of switches can be used to focus an array with 64 to 128 elements. The simulation and experimental results show that Fresnel beamforming image quality is comparable to traditional delay-and-sum (DAS) beamforming in terms of spatial resolution and contrast-to-noise ratio (CNR) under certain system parameters. With an f-number of 2 and 50% signal bandwidth, the experimental lateral beamwidths are 0.54, 0.67, and 0.66 mm and the axial pulse lengths are 0.50, 0.51, and 0.50 mm for DAS, 8-phase, and 4-phase Fresnel beamforming, respectively. The experimental CNRs are 4.66, 4.42, and 3.98, respectively. These experimental results are in good agreement with simulation results.

Development and characterization of candidate rotavirus vaccine strains derived from children with diarrhoea in Vietnam.

In Vietnam, rotavirus infection accounts for more than one-half of all hospitalizations for diarrhoea among children less than 5 years of age. While new vaccines to prevent rotavirus diarrhoea have been developed and introduced into some countries by multinational manufacturers, the ability for developing countries such as Vietnam to introduce several new and important vaccines into the routine infant immunization schedule may be challenging. In order to be partially self-sufficient in vaccine production, Vietnam has pursued the development of several rotavirus strains as candidate vaccines using isolates obtained from Vietnamese children with diarrhoea. This paper describes the origin, isolation and characterization of 3 human rotavirus strains being considered for further vaccine development in Vietnam. The goal is to prepare a monovalent G1P [8] rotavirus vaccine using one of these strains obtained in Vietnam and naturally attenuated by multiple passages in cell culture. While this is an ambitious project that will require several years' work, we are using the lessons learned to improve the overall quality of vaccine production including the use of Vero cell techniques for the manufacture of other vaccines in Vietnam.

A lamin A/C beta-strand containing the site of lipodystrophy mutations is a major surface epitope for a new panel of monoclonal antibodies.

Using a phage-displayed peptide library, we have identified the epitope recognized by a new panel of five monoclonal antibodies (mAbs) raised against full-length recombinant human lamin A. The mAbs were found to recognize both lamin A and C by Western blotting and immunolocalization at the nuclear rim. A nine-amino acid consensus sequence PLLTYRFPP in the common immunoglobulin-like (Ig-like) domain of lamin A/C contains the binding site for all five mAbs. Three-dimensional structure of the Ig-like domain of lamin A/C shows this sequence is a complete beta-strand. This sequence includes arginine-482 (R482) which is mutated in most cases of Dunnigan-type familial partial lipodystrophy (FPLD). R482 may be part of an interaction site on the surface of lamin A/C for lamin-binding proteins associated with lipodystrophy.