bluuebunny/crossref_metadata_2025 huggingface dataset:
Unexpected Term Neonatal Intensive Care Unit Admissions and a Potential Role for Centralized Remote Fetal Monitoring
Authors: Martin Jane K. , Price-Haywood Eboni G. , Gastanaduy Mariella M. , Fort Daniel G. , Ford Mary K. , Peterson Sydney P. , Biggio Joseph R.
Published: April 2021

Objective Centralized remote fetal monitoring (CRFM) has been proposed as a method to improve the performance of intrapartum fetal heart rate (FHR) monitoring and perinatal outcomes. The purpose of this study is to determine whether CRFM was associated with a reduction in unexpected term neonatal intensive care unit (NICU) admissions.

Study Design A pre–post design was used to examine the effectiveness of CRFM which was implemented in stages across five hospitals. The exposure group was all women who underwent intrapartum monitoring via CRFM. The unexposed group was of women who delivered at the same hospitals prior to implementation of CRFM. Pregnancies with expected NICU admissions, gestational age <37 weeks, birth weight <2,500 g, or major fetal anomalies detected prenatally were excluded. The primary outcome was unexpected term NICU admission; secondary outcomes were cesarean and operative vaginal delivery (OVD), and 5-minute Apgar's score of <7 rates. Maternal and delivery characteristics were examined with Student's t, Wilcoxon's, Chi-square, and Fisher's exact tests. Multivariable logistic regression was performed to control for potential confounders.

Results There were 19,392 live births included in this analysis. In the univariable analysis, the odds of unexpected term NICU admission was lower among the CRFM exposed group compared with the unexposed group (odds ratio [OR] = 0.86, 95% confidence interval [CI]: 0.75–0.99; p = 0.038). In multivariable analysis, this did not reach statistical significance (OR = 0.92, 95% CI: 0.79–1.06; p = 0.24). Cesarean and OVD were less likely in the exposed group (OR = 0.91, 95% CI: 0.85–0.97; p = 0.008) and (OR = 0.70, 95% CI: 0.59–0.83, p < 0.001), respectively, in univariable analysis. When adjusted for potential confounders, the effect remained statistically significant for cesarean delivery (OR = 0.92, 95% CI: 0.85–0.98; p = 0.012). When adjusted for hospital, OVD rate was lower at the highest volume and highest acuity site (OR = 0.48, 95% CI: 0.36–0.65, p < 0.001).

Conclusion In some practice settings, utilization of a CRFM system may decrease the risk of unexpected term NICU admission, cesarean, and OVD rate.

Key Points
Aspirin Responsiveness at a Dose of 80 mg and Its Impact on Birth Weight when Used in Twin Pregnancies: The GAP Pilot Randomized Trial
Authors: Carpentier Caroline , Guerby Paul , Camiré Bruno , Tapp Sylvie , Boutin Amélie , Bujold Emmanuel
Published: April 2021

Objective Daily aspirin, started in the first trimester of pregnancy, is commonly used for the prevention of preeclampsia and fetal growth restriction in multiple gestation. However, the optimal dose remains controversial and the evidence for the use of aspirin in multiple pregnancies is scarce. We aimed to estimate the impact of 80 mg of aspirin in twin pregnancies.

Study Design We performed a pilot double-blind randomized trial of women with twin pregnancies recruited between 8 and 14 weeks of gestation. Fifty participants (25 in each group) were randomized to 80 mg of aspirin daily at bedtime or a placebo from randomization until 36 weeks of gestation. Primary and secondary outcomes included the birth weight of live infants, preeclampsia, and aspirin responsiveness evaluated by a platelet aggregation test (platelet function assay [PFA]-100).

Results All participants were followed until birth, including 48 and 47 live newborns in the aspirin and the placebo groups, respectively. The mean birth weight difference between the aspirin (2,385 ± 529 g) and placebo (2,224 ± 706 g) groups was of 179 g (95% confidence interval [CI]: −172–531 g, p = 0.32). We observed two (8%) cases of preeclampsia in the aspirin group and no case with placebo (p = 0.49). Most importantly,16 of 24 participants who received aspirin (67%; 95% CI: 45–84%) had a normal PFA-100 test at 22 to 23 weeks, including the two cases of preeclampsia, suggesting that the majority of the participants were nonresponsive to 80 mg of aspirin.

Conclusion Our results suggest that the majority of women with twin pregnancies showed a lack of response to a daily dose of 80 mg of aspirin according to the PFA-100 test, compared with the expected 29% of nonresponsiveness in singleton pregnancies. A daily dose of 80 mg of aspirin is likely to be insufficient for the prevention of preeclampsia and other placenta-mediated complications in twin pregnancies.

Key Points
Asthma Medication Regimens in Pregnancy: Longitudinal Changes in Asthma Status
Authors: Rohn Matthew C.H. , Stevens Danielle R. , Kanner Jenna , Nobles Carrie , Chen Zhen , Grantz Katherine L. , Sherman Seth , Grobman William A. , Kumar Rajesh , Biggio Joseph , Mendola Pauline
Published: April 2021

Objective This study aimed to assess the impact of common asthma medication regimens on asthma symptoms, exacerbations, lung function, and inflammation during pregnancy.

Study Design A total of 311 women with asthma were enrolled in a prospective pregnancy cohort. Asthma medication regimen was categorized into short-acting β agonist (SABA) alone, SABA + inhaled corticosteroid (ICS), SABA + ICS + long-acting β agonist (LABA), and no asthma medications (reference). We evaluated asthma control at enrollment (< 15 weeks' gestation) and its change into trimesters 2 and 3, including per cent predicted forced expiratory volume in 1 second (%FEV1) and peak expiratory flow (%PEF), pulse oximetry, fractional exhaled nitric oxide (FeNO), asthma symptoms (asthma attacks/month, night symptoms/week), and severe exacerbations. Linear mixed models adjusted for site, age, race, annual income, gestational age, body mass index, and smoking, and propensity scores accounted for asthma control status at baseline.

Results Women taking SABA + ICS and SABA + ICS + LABA had better first trimester %PEF (83.5% [75.7–91.3] and 84.6% [76.9–92.3], respectively) compared with women taking no asthma medications (72.7% [66.0–79.3]). Women taking SABA + ICS + LABA also experienced improvements in %FEV1 (+11.1%, p < 0.01) in the third trimester and FeNO in the second (−12.3 parts per billion [ppb], p < 0.01) and third (−11.0 ppb, p < 0.01) trimesters as compared with the trajectory of women taking no medications. SABA + ICS use was associated with increased odds of severe exacerbations in the first (odds ratio [OR]: 2.22 [1.10–4.46]) and second (OR: 3.15 [1.11–8.96]) trimesters, and SABA + ICS + LABA use in the second trimester (OR: 7.89 [2.75–21.47]). Women taking SABA alone were similar to those taking no medication.

Conclusion Pregnant women taking SABA + ICS and SABA + ICS + LABA had better lung function in the first trimester. SABA + ICS + LABA was associated with improvements in lung function and inflammation across gestation. However, both the SABA + ICS and SABA + ICS + LABA groups had a higher risk of severe exacerbation during early to mid-pregnancy.

Key Points
Opposition behaviour against the third wave of autocratisation: Hungary and Poland compared
Authors: Ilonszki Gabriella , Dudzińska Agnieszka
Published: April 2021

Hungary and Poland are often placed in the same analytical framework from the period of their ‘negotiated revolutions’ to their autocratic turn. This article aims to look behind this apparent similarity focusing on opposition behaviour. The analysis demonstrates that the executive–parliament power structure, the vigour of the extra-parliamentary actors, and the opposition party frame have the strongest influence on opposition behaviour, and they provide the sources of difference between the two country cases: in Hungary an enforced power game and in Poland a political game constrain opposition opportunities and opposition strategic behaviour.
Thermoelectric improvement of the figure of merit of zinc phosphate glass composites by a likely tunnel percolation mechanism
Authors: Radouane Nassima , Depriester Michael , Hadj Sahraoui Abdelhak , Ouaki Bennaceur , Escorne Benoit , Duponchel Benoît , Pratap Singh Dharmendra , Maaroufi Abdelkrim
Published: April 2021

Zinc phosphate glasses (ZPG) have emerged as new energy materials due to their femtosecond response and chemical durability. The present investigation renders the methodology to enhance the thermoelectric properties of ZPG by adding external guest graphitic particles. Herein, transport parameters, Seebeck coefficient, and thermal and electrical conductivities of zinc phosphate glass composites were measured as a function of graphite concentration, followed by the calculation of the thermoelectric figure of merit (ZT). It is observed that the thermoelectric properties of the ZPG/graphite composites are superior to that of the pristine ZPG matrix and significantly depend on the volume concentration of graphite filler. ZPG/graphite composite exhibiting with 5 vol. % graphite content imparts the best thermoelectric performance with a power factor of PF≈0.98μWm−1K−2 and ZT≈2.6×10−4.
A quantum Langevin equation approach for two-dimensional electronic spectra of coupled vibrational and electronic dynamics
Authors: Wong Man Tou , Cheng Yuan-Chung
Published: April 2021

We present an efficient method to simulate two-dimensional (2D) electronic spectra of condensed-phase systems with an emphasis on treating quantum nuclear wave packet dynamics explicitly. To this end, we combine a quantum Langevin equation (QLE) approach for dissipation and a perturbative scheme to calculate three-pulse photon-echo polarizations based on wave packet dynamics under the influence of external fields. The proposed dynamical approach provides a consistent description of nuclear quantum dynamics, pulse-overlap effects, and vibrational relaxation, enabling simulations of 2D electronic spectra with explicit and non-perturbative treatment of coupled electronic–nuclear dynamics. We apply the method to simulate 2D electronic spectra of a displaced-oscillator model in the condensed phase and discuss the spectral and temporal evolutions of 2D signals. Our results show that the proposed QLE approach is capable of describing vibrational relaxation, decoherence, and vibrational coherence transfer, as well as their manifestations in spectroscopic signals. Furthermore, vibrational quantum beats specific for excited-state vs ground-state nuclear wave packet dynamics can also be identified. We anticipate that this method will provide a useful tool to conduct theoretical studies of 2D spectroscopy for strong vibronically coupled systems and to elucidate intricate vibronic couplings in complex molecular systems.
A new criterion of coalescence-induced microbubble detachment in three-dimensional microfluidic channel
Authors: Chen Rou , Zhou Shuiyi , Zhu Likun , Zhu Luoding , Yan Weiwei , Yu Huidan
Published: April 2021

This work is motivated by an experiment of microbubble transport in a polymer microfluidic gas generation device where coalescence-induced detachment exhibits. We numerically study three-dimensional microbubble coalescence using the graphics processing unit accelerating free energy lattice Boltzmann method with cubic polynomial boundary conditions. The focus is on the coalescence-induced microbubble detachment (CIMD) in microfluidics. From the experimental observation, we identified that size inequality between two-parent bubbles and the size of the father (large) bubble are key factors to determine if a CIMD will occur. First, the analytical relationship between equilibrium contact angle and dimensionless wetting potential and experimental results of coalescence with and without CIMD are employed for the verification and validation, respectively. From eighteen experimental and computational cases, we derive a new criterion for CIMD: CIMD occurs when the two-parent bubbles are (nearly) equal with a relatively large radius. The underlying mechanism behind this criterion is explored by the time evolution of the velocity vector field, vorticity field, and kinetic energy in the entire coalescence. It is found that the symmetric capillary force drives the formation of vertical flow stream to the horizontal alignment of parent bubbles and the blockage of the downward stream due to the solid interface promotes the intensity of the upward stream. Meanwhile, large-sized parent bubbles transfer a large amount of kinetic energy from the initial free surface energy, which is essential to lead a CIMD in the post-coalescence stage. Such a new criterion is expected to impact the design and optimization of microfluidics in various applications.
Water dynamics within nanostructured amphiphilic statistical copolymers from quasielastic neutron scattering
Authors: Sepulveda-Medina Pablo I. , Tyagi Madhusudan , Wang Chao , Vogt Bryan D.
Published: April 2021

Understanding the properties of water under either soft or hard confinement has been an area of great interest, but nanostructured amphiphilic polymers that provide a secondary confinement have garnered significantly less attention. Here, a series of statistical copolymers of 2-hydroxyethyl acrylate (HEA) and 2-(N-ethylperfluorooctane sulfonamido)ethyl methacrylate (FOSM) are swollen to equilibrium in water to form nanostructured physically cross-linked hydrogels to probe the effect of soft confinement on the dynamics of water. Changing the composition of the copolymer from 10 to 21 mol. % FOSM decreases the average size of the assembled FOSM cross-link, but also the spacing between the cross-links in the hydrogels with the mean distance between the FOSM aggregates decreasing from 3.9 to 2.7 nm. The dynamics of water within the hydrogels were assessed with quasielastic neutron scattering. These hydrogels exhibit superior performance for inhibition of water crystallization on supercooling in comparison to analogous hydrogels with different hydrophilic copolymer chemistries. Despite the lower water crystallinity, the self-diffusion coefficient for these hydrogels from the copolymers of HEA and FOSM decreases precipitously below 260 K, which is a counter to the nearly temperature invariant water dynamics reported previously with an analogous hydrogel [Wiener et al., J. Phys. Chem. B 120, 5543 (2016)] that exhibits nearly temperature invariant dynamics to 220 K. These results point to chemistry dependent dynamics of water that is confined within amphiphilic hydrogels, where the interactions of water with the hydrophilic segments can qualitatively alter the temperature dependent dynamics of water in the supercooled state.
Vortex ordering and dynamics on Santa Fe artificial ice pinning arrays
Authors: Li Wenzhao , Reichhardt C. J. O. , Jankó B. , Reichhardt C.
Published: April 2021

We numerically examine the ordering, pinning, and flow of superconducting vortices interacting with a Santa Fe artificial ice pinning array. We find that as a function of magnetic field and pinning density, a wide variety of vortex states occur, including ice rule obeying states and labyrinthine patterns. In contrast to square pinning arrays, we find no sharp peaks in the critical current due to the inherent frustration effect imposed by the Santa Fe ice geometry; however, there are some smoothed peaks when the number of vortices matches the number of pinning sites. For some fillings, the Santa Fe array exhibits stronger pinning than the square array due to the suppression of one-dimensional flow channels when the vortex motion in the Santa Fe lattice occurs through the formation of both longitudinal and transverse flow channels.
The utilization of boron nitride (BN) for granular L1-FePt HAMR media fabrication
Authors: Zhou Bing , Laughlin David E. , Zhu Jian-gang (Jimmy)
Published: April 2021

In this experimental study, we present a dual-layer structure of FePt-boron nitride (BN)/FePt-SiOx granular media for the heat-assisted magnetic recording. The boron nitride (BN) was deposited together with FePt at 700 °C for the first 2.5 nm in the initial film growth. After the initial growth, SiOx was used to replace the BN to serve as the grain boundary material for the rest of film growth process. The transmission electron microscopy study on the fully grown FePt-BN/FePt-SiOx film shows well-isolated FePt grains that are fully encircled by the well-defined grain boundaries. The areal density of FePt grains is distinctively higher than that of the conventional granular FePt-C-based film at similar film thickness. The FePt-BN/FePt-SiOx bilayer granular media also demonstrate excellent magnetic properties, which are comparable to that of FePt-C-SiOx granular media in terms of the hysteresis characteristics.
Enhancement of ferroelectricity and orientation in solution-derived hafnia thin films through heterogeneous grain nucleation
Authors: Schenk Tony , Bencan Andreja , Drazic Goran , Condurache Oana , Valle Nathalie , Adib Brahime El , Aruchamy Naveen , Granzow Torsten , Defay Emmanuel , Glinsek Sebastjan
Published: April 2021

In this work, we demonstrate an approach for improving ferroelectric properties of La:HfO2 thin films by shifting the grain growth regime toward heterogeneous nucleation. A dilute 0.083 M instead of a 0.25 M solution together with an annealing step after every spin-coating cycle film gives rise to a significant improvement of ferroelectric properties. While a remanent polarization of 7 μC/cm2 was found for randomly oriented conventional films, the value of 15 μC/cm2 for the dilute solution is a result of a mixed 111 and 002 preferential orientation. A more than 50% improved breakdown voltage stems from a global density improvement from 8.0 to 8.4 g/cm3 as obtained from x-ray reflectivity (XRR). We also find superstructure peaks in XRR hinting on periodic alternations of the local density throughout the film thickness. Scanning transmission electron microscopy and secondary ion mass spectrometry confirm this periodicity. The sensitivity of XRR for this periodicity was leveraged to gain further insights in the origin of this superstructure with additional experiments. We conclude that both orientation and the superstructure are caused by a “layered structure” according to Schuler's microstructural zone model. However, our data also provide evidence for parallel chemical effects of cap formation in each stacked sub-layer. While this work shows a significant enhancement of ferroelectric properties, it also provides insights into further optimization potential of solution deposition of HfO2/ZrO2 thin films. Our XRR-based approach supplemented with suitable additional analysis can be of great value for the optimization of other solution-derived thin films beyond the material class studied here.
AlGaN-based UV-B laser diode with a high optical confinement factor
Authors: Tanaka Shunya , Ogino Yuya , Yamada Kazuki , Omori Tomoya , Ogura Reo , Teramura Shohei , Shimokawa Moe , Ishizuka Sayaka , Yabutani Ayumu , Iwayama Sho , Sato Kosuke , Miyake Hideto , Iwaya Motoaki , Takeuchi Tetsuya , Kamiyama Satoshi , Akasaki Isamu
Published: April 2021

To reduce the threshold current density (Jth) of ultraviolet (UV)-B AlGaN-based laser diodes, we investigated the critical parameters aiming to increase the injection efficiency ηi and the optical confinement factor Γ. Optimization of the thickness of the waveguide layer, the average Al content of the p-type AlGaN cladding layer, and the film thickness of the cladding layer demonstrated that the device characteristics can be improved. This optimization achieved a reduction in Jth to 13.3 kA cm−2 at a lasing wavelength of 300 nm, thus offering the lowest Jth value yet achieved for a UV-B laser diode.
Revealing the atomic-scale origin of simultaneously enhanced hardness and crack resistance in a single phase material
Authors: Tao Yunhang , Wang Xiaoli
Published: April 2021

Overcoming the brittleness of glass materials has always been one of the most important scientific questions in the field of materials physics. Herein, we selected a silica (SiO2) crystal, a silica glass, a sapphire (Al2O3) crystal, an amorphous alumina film, and a CaO⋅Al2O3 (CA) glass as the research objects. Detailed characterization was performed on two kinds of macromechanical properties, i.e., hardness and crack resistance. Combined with their density, bond density, bond energy density, and other structural features, we systematically investigated the structural origin and physics mechanism of hardness and crack resistance in a single phase material. The structural origin of the inverse relationship between hardness and crack resistance is ascribed to the facts that the bond density in a single phase material is generally positively correlated with the hardness while usually negatively correlated with the crack resistance. The discovery of simultaneously high hardness and high crack resistance in a CA glass revealed the key way to break through the inverse relationship between hardness and crack resistance, i.e., to develop the materials with the capability of self-adaptive structural adjustment, thus dissipating as much energy as possible upon external impact. These findings pave the way to the development of “scratchproof” and “unbreakable” transparent window materials such as a mobile phone screen glass.
Recovery of damage in electron-irradiated ceria
Authors: Costantini Jean-Marc , Lelong Gérald , Guillaumet Maxime , Gourier Didier
Published: April 2021

The damage recovery of an electron-irradiated CeO2 single crystal was studied by in situ UV–visible absorption spectroscopy during isochronal thermal annealing up to 873 K. The spectrum of the as-irradiated crystal shows band tailing below the fundamental absorption edge for photon energy near 3.2 eV. Two broad Gaussian bands centered at about 0.9 and 1.4 eV are also recorded. The edge region is treated by including the Urbach edge contribution. The variation of bandgap energy and Urbach energy is followed as a function of the annealing temperature. The absorption edge was red-shifted with annealing temperature then returned to the starting value after cooling back to room temperature. The disorder contribution to the Urbach edge is deduced by subtracting the temperature contribution. It shows a decay of the disorder contribution following a first-order kinetics process with an onset of recovery at 373 K and activation energy of about 0.15 eV. Full recovery is achieved at 873 K, whereas a partial recovery of the two absorption bands (at 0.9 and 1.4 eV) is found. The low activation energy is interpreted in reference to the available literature data on the energy barriers for point defect migration, and assigned to the migration of oxygen interstitials associated to electronic levels near the top of the valence band edge. A recombination mechanism is suggested, involving both electron hopping and interstitial oxygen diffusion.
Darcy–Carreau–Yasuda rheological model and onset of inelastic non-Newtonian mixed convection in porous media
Authors: Brandão P. V. , Ouarzazi M. N. , Hirata S. C. , Barletta A.
Published: April 2021

An extension of Carreau and Carreau–Yasuda rheological models to porous media is proposed to study the onset of mixed convection of both pseudoplastic fluids (PF) and dilatant fluids (DF) in a porous layer heated from below in the presence of a horizontal throughflow. In comparison with Newtonian fluids, three more dimensionless parameters are introduced, namely, the Darcy–Weissenberg number Wi, the power–law index n, and the Yasuda parameter a. Temporal stability analysis of the basic state showed that in the absence of a throughflow (Wi = 0), the critical Rayleigh number and the critical wavenumber at the onset of convection are the same as for Newtonian fluids, namely, Rac=4π2 and kc=π, respectively. When the throughflow is added (Wi > 0), it is found that moving transverse rolls (stationary longitudinal rolls) are the dominant mode of the instability for PF (for DF). Furthermore, depending on Wi, two regimes of instability were identified. In the weakly non-Newtonian regime (i.e., Wi<Wit≈1), a destabilizing effect is observed for PF, while the reverse occurs for DF. These effects are more intense by reducing (increasing) the index n for PF (for DF). In this regime, a significant qualitative difference is found between the Darcy–Carreau model and the power–law model. However, in the strongly non-Newtonian regime, the two models lead to similar results. A mechanical energy budget analysis is performed to understand the physical effects of the interaction between the basic throughflow and the disturbances. It is also shown that the intrinsic macroscale properties of the porous medium may play a key role in the stabilizing/destabilizing effect. Finally, a comparison is made between the present theoretical predictions and recent mixed convection experiments in a Hele–Shaw cell.
Numerical investigation of the impacting and freezing process of a single supercooled water droplet
Authors: Wang Yongkui , Ju Lei , Han Duanfeng , Wang Qing
Published: April 2021

In order to study the mechanism of ice formation after water droplets produced by splashing waves attach to ship superstructure in cold ocean regions, a numerical framework that considers the effect of supercooling degree on the meso-scale water droplet freezing is developed to explore the freezing mechanism of water droplets after impacting. This model can track the solid–liquid and air–liquid interface together using a coupled volume-of-fluid and level set multiphase method and Enthalpy-Porosity phase change method. The model introduces a mixed fraction to describe the problem of three-phase unification. The simulation results of the center freezing height and droplet spreading factor in this paper are consistent with the experimental results in related literature, which verifies the accuracy of the framework. The study includes a detailed description of the dynamic and thermodynamics mechanism of the water droplet. The influence factors of droplet impacting and freezing process are analyzed. The analysis results show that the surface wettability, supercooling degree, and impact velocity have a great influence on the freezing behavior of droplets. This model can deepen the understanding of icing mechanism on ship superstructure surface, provide an indication for engineers to develop an accurate prediction method of ice accretion on ship superstructure surface.
Knudsen diffusion differs from Fickian diffusion
Authors: Li Jun , Cai Chunpei , Li Zhi-Hui
Published: April 2021

We investigate the gas transport enhancement through nanotubes, relative to the prediction by the prevailing century-old Knudsen diffusion model. This enhancement is usually attributed to the partly specular molecular reflections at the smooth nanotube surface, which break the model assumption of completely diffusive reflections. However, an oversighted cause of the discrepancy between the measurement and theory that we found is that even for the gas transport with completely diffusive reflections, the Knudsen diffusion model based on Fick's first law is accurate only for long nanotubes. Additionally, for smooth nanotubes with partly specular reflections, the Knudsen diffusion model is also invalid even if the diffusion coefficient is corrected to account for the atomic-scale surface smoothness. On the other hand, the Knudsen diffusion model might be used for interpretations instead of predictions, and then the diffusion coefficient inferred from the measured mass flow rate could be completely different from the actual value. All those discrepancies and confusions stem from the implementation of Fick's first law can be avoided by using the molecular transmission probability obtained by the kinetic theory to quantify the flow rate of the Knudsen diffusion process. This work provides the correction to the Knudsen diffusion model for accurate predictions of gas diffusion through nanotubes and better interpretations of experimental measurements.
Broadband acoustic focusing via binary rectangular cavity/Helmholtz resonator metasurface
Authors: Tang Shuai , Ren Bin , Feng Yuxin , Song Jie , Jiang Yongyuan
Published: April 2021

In this work, we numerically and experimentally demonstrate that broadband acoustic focusing can be realized using a sub-wavelength binary metasurface. Rectangular cavities and Helmholtz resonators are utilized to construct a coding system, which brings the desired transmittance and phase difference in a wide range of wavelengths. The apparent acoustic focusing is validated in a bandwidth of 0.8f0–1.6f0 by experimental measurements, which agrees well with the numerical simulations and offers a degree of freedom to manipulate the focal length actively. This work provides a solution to design a sub-wavelength planar lens with broadband and robustness properties, which may have promising applications in numerous acoustic engineering procedures, including biomedical diagnosis and non-destructive testing.
The development of small-scale freshwater aquaculture in Mozambique.
Authors: Mapfumo Blessing
Published: April 2021

This case study is based on information collected by the author during a visit to Mozambique in November 2008 and May 2009 as part of a scoping study by INFOSA for the Mozambique Small-scale Aquaculture Development Plan. The work involved collaboration with the Institute of Aquaculture Development in Mozambique (INAQUA). INFOSA currently has training and capacity building programmes for small-scale fisheries and aquaculture in Mozambique. Although aquaculture in Mozambique is in its infancy, the cultivation of freshwater species such as tilapias has been in existence for many years. The country has over 60 major rivers in addition to lakes, dams and freshwater lagoons and is dominated by a tropical climate. Potential for mariculture along the Indian Ocean has also been investigated for many years. Small-scale freshwater aquaculture in Mozambique is dominated by many fish farmers with small ponds averaging about 200 m2 in area. Production is generally low, subsistence oriented, and integrated with some form of agriculture. During the author's visit to many parts of the country in 2008, it was noted that there is generally huge interest amongst many farmers in taking aquaculture more seriously by operating it as a small business for income generation as well as for household food production. Assistance from the government has often come in various forms, but mainly through training and extension services offered by the Ministry of Agriculture and the Institute of Aquaculture Development in Mozambique (INAQUA), which falls under the Ministry of Fisheries. A few organized fish farmers have received direct financial support for the construction and management of fish ponds from the government. Non-governmental organizations and intergovernmental organizations such as the Food and Agriculture Organization (FAO) have been of great assistance in the past. Now that the regulatory framework for the development of aquaculture in Mozambique is in place, the government, through INAQUA is concentrating much on building strategies to improve production, especially among smallholder farmers. Part of the strategy involves organizing the individually scattered farmers, by district, into clusters and then trying to create larger, central farms that will act as drivers to these smallholder farmers. In addition, the government has accelerated its efforts to lure potential investors into supporting the developing aquaculture sector. This is in line with the FAO's Special Programme for Aquaculture Development in Africa (SPADA). A number of constraints to the development of aquaculture in Mozambique have been identified; poor infrastructure, and the requirements for training and capacity building, access to finance, and research and development. Other factors include poor coordination between the institutions, market access and a lack of planning strategies.
La pisciculture dans le centre-ouest et le Sud-ouest de la Côte d'Ivoire: situation actuelle et enjeux de l'encadrement technique par l'ONG APDRACI.
Authors: Blé Célestin M.
Published: April 2021

Fish farming in the center and south-west of Côte d'Ivoire is enjoying undeniable success. The high proportion of new installations (272 fish farmers for a total water surface of 211 hectares) and the improvement in production (this increased from 125 tonnes to 243 tonnes from 1998 to 2003) which continues to grow reflects the adoption of the extensive model by fish farmers. The Association Pisciculture et Développement Rural en Afrique Tropical Humid, France (APDRA-F), with the support of the Catholic Committee against Hunger and for Development (CCFD) and the Association Française des Volontaires du Progrès (AFVP) will have contributed, thanks to the Center-Ouest Piscicole Project (PPCO), to this development. This dynamic is now supported by the Association Pisciculture et Développement Rural en Afrique Tropical Humid, Côte d'Ivoire (APDRA-CI), whose major challenge remains the promotion and development of fish farming through efficient technical supervision in all regions of the Ivory Coast.
A case study of Hangere integrated agriculture-aquaculture farm in Malawi.
Authors: Kamtambe Kingsley M , Kang'ombe Jeremiah , Kaunda Emmanuel Kw
Published: April 2021

The case study was undertaken to assess performance and sustainability of Hangere Agriculture-Aquaculture Integrated Farm. Data was collected during a seven-day visit at the farm (carried out on 7-14 June 2009), using a semi-structured questionnaire with open ended questions and a study of farm records and cash flows. Direct observations of farm operations were also reported. Hangere integrated agriculture-aquaculture farm is located in Mzuzu City, Mzimba District, Malawi and belongs to 37-year-old Mrs Liness Chavula. The farm has a total land holding of approximately 13 ha. Of this area, only 2.2 ha are used for aquaculture with three drainable ponds with a total area of 1804 m2. Of the remaining area, 4 ha are used for maize cultivation, 1.5 ha for growing sweet potatoes, and 1 ha is used for vegetables, including cassava and Rhodes grass Chloris gayana. The farm holds Tilapia rendalli and Oreochromis karongae in polyculture and Clarias gariepinus in monoculture. The fish are fed formulated diets and the ponds are fertilized with livestock manure. The fish are harvested three times yearly and are sold to wholesalers and retail with prices of K450/kg (US $3.21) and K500/kg (US $3.5), respectively. Pigs, goats and a dairy cow are also kept on the farm. In 2008 the farm made a profit of K289,000 (US $2,064), from the sale of field crops, livestock and fish. Of the K289,000 of profit, K100,000 (US $714) came from fish sales while K70,000 (US $500) came from maize sales, K28,000 (US $200) from pig sales and K50,000 (US $357) from sweet potatoes. The farm faces several challenges including labour shortages, absence of a hatchery facility for fingerling production and lack of available extension services. The farm experiences low water levels during the hot-dry season and pest infestation in the pond vicinity, both of which lower production. Hangere farm operates at a semi-intensive level, being integrated with other on-farm agriculture activities, and is a typical example of a small scale fish farm in Malawi. The farm has also begun cultivating new crops, mainly coffee and wheat, both of which are highly priced cash crops in Malawi. C. gariepinus (catfish) has also been introduced in ponds at the farm with the potential to reach 1 kg in body weight in 6 months.
Ecological and economic assessment of the role of seaweeds in abalone integrated multi-trophic aquaculture - a South African case study.
Authors: Nobre Ana M , Robertson-Andersson Deborah , Neori Amir , Sankar Kishan
Published: April 2021

South Africa (SA) is the world's third largest abalone producer. The industry is now challenged by restrictions on access to wild kelp, which is the natural food for abalone. Abalone farmers in SA have recently begun implementing integrated multi-trophic aquaculture (IMTA) with the seaweed Ulva lactuca L. and the abalone Haliotis midae L. The positive aspects include: (1) better abalone growth when fed with mixed algae diet, (2) farm effluent reduction, (3) avoidance of contaminated seawater during red tides/oil spills, (4) promoting employment in rural coastal communities. This case study presents a quantification exercise that compares the ecological-economic costs/benefits associated with the seaweed-culture integration into the abalone industry. Data from an abalone farm from the Western Cape with annual production of 240 metric tonnes (MT) was used. The ecological-economic performance of abalone production in monoculture using a water flow-thorough system was compared against two IMTA scenarios, with water recirculation through a seaweed culture unit that replaces part of the wild kelp consumption. The comparison of monoculture with IMTA scenarios indicates an overall economic gain of between 1.1-3.0 million US$ per year. This range of values reflects the effects of adopting IMTA on the farm's profit and the environmental gains, which represent 80% of the estimated overall benefits and includes: avoided kelp bed restoration, reduced nutrient discharge and avoided greenhouse gas emissions (due to energy savings). This analysis is particularly important in informing the SA industry and regulators about the value of the implementation by the abalone farmers of IMTA systems. For this particular case study the message is that the IMTA approach provides substantial economic incentives to the abalone farmers and even larger benefits to the public, compared with the abalone monoculture production.
Etude de cas: production de tilapia mono sexe á Maevatanana, Madagascar.
Authors: Rakotomamonjy Léon
Published: April 2021

Members of the Professional Association of Aquaculturists of Madagascar which has been promoting Tilapia farming in Madagascar since 2001, the project we are presenting is a follow-up to the implementation of this promotion. The project consists of setting up a tilapia production chain using monosex male fry. This project is being developed in the region of Maevatanana, a site chosen for its climatic characteristics favorable to fish farming. The objective of the project is first to produce and market male monosex Tilapia fry, then to participate in the popularization of fattening fish farming and finally to organize the collection of finished products to supply the large market of the capital Antananarivo. In a socio-economic context of entrepreneurship which is seeking its definition, the start-up and implementation of activities take place with difficulty and slowly.
The rise and demise of the commercial shrimp farm, Amatikulu Prawns (Pty) Ltd., 1989 to 2004 (Kwazulu Natal, South Africa).
Authors: Evans Laurence
Published: April 2021

Amatikulu Prawns (Pty) Ltd operated as a commercial shrimp farm from 1989 to 2004 when market forces made producing shrimp unviable and the farm closed. The farm established the technical requirements from the existing scientific literature, consultancy, training courses and visits to other commercial farms. The farm had two sites (10 ha and 24 ha), two hatcheries, a HACCP-certified processing plant and a feed mill.
Production commerciale de tilapia du Nil sur le Lac Kariba, Zimbabwe.
Authors: Pasipamire Watson
Published: April 2021

Lake Harvest Aquaculture (Pvt) Ltd developed freshwater tilapia production in 1996 on a location initially used by a freshwater shrimp farm set up by a Zimbabwean food company, La Cairn Food Ltd. The farm was established in 1997 and ten years later it produces 3000 tonnes of tilapia which, once harvested and processed, are exported to European and regional markets. The initial projections in terms of production and net farm income were made until 2001, the start of the economic recession. The decline in agricultural production due to insufficient resources and drought resulted in a lack of raw materials for food manufacturing companies. The continued downward trend in feed production affected the company so much that it could no longer support the growing stock of fish. Power and economic issues resulted in the decision by management to stop expanding the business in 2002. The cost of setting up Lake Harvest business is US$10,000,000. The company benefited from external financing from the Commonwealth Development Corporation (CDC) and Comafin, a private Pan-African company with equity capital, before the change in the mode of participation in the capital which took place in 2002. The main costs concerned installation and mooring of cages; and construction of a fish processing plant. Six sites were installed, each costing around US$350,000, including boats. The costs of the processing plant are estimated at around US$4,000,000. This case study aims to provide a technical itinerary and overview of Lake Harvest Aquaculture as a caged tilapia company in Lake Kariba, Zimbabwe; and provide a means of assessment and study for those interested in the development of cage aquaculture in Africa south of the Sahara. All major activities performed at Lake Harvest are described in the same sequence as on the farm: from production, management, to sale of the final product.
Polyculture de tilapia et Clarias en etang dans la commune de Pobè, sud-est du Benin.
Authors: Ondodje Kochikpa
Published: April 2021

The SARL "Pobè Fish Farm" located in the South-East of Benin specializes in the production and sale of tilapia and Clarias. The farm has twenty two ponds of 200 m2 (10 m × 20 m) supplied with water by a pipe system from a natural and permanent stream. The water supply is via a concrete channel which did not allow the water to be renewed once the pond is full. Work has been carried out to allow a larger inflow of water and communication between the ponds. The operation of the farm is modeled on the types of agro-fish farms existing in Asia and encountered in Vietnam in particular; it aims to put theoretical knowledge into practice and on the other hand to contribute to the development of a sector still little known in Benin, despite the many hydroagricultural potentials with which this country is endowed. The species bred at national level are rustic and adapted to the environment and whose genetic performance has not been improved. In fact, only modern breeding following very precise technical standards can allow obtaining interesting results from the point of view of agronomic yield and financial profitability. Indeed, these fish from our ponds are very popular with the populations (the average wholesale price is 1000 FCFA/kg) and are already an integral part of eating habits both in rural areas and in cities.
Etat de la pisciculture périurbaine dans la ville province de Kinshasa dans le contexte post-conflits armés.
Authors: Mutala Simon , Fataki Michel Djoko , Beya Benoit
Published: April 2021

For four decades, fish farming has declined following the breakdown of bilateral cooperation resulting in the sudden departure of expatriate executives, inexperience, and insufficient local expertise. The looting and destruction of fish farming infrastructure led to the cessation of supervision, extension and the abandonment of fish farming activities by fish farmers. Added to this is the deterioration of the economic fabric reinforced by the war and the total insecurity of the city. From 2004 to 2008, the Congolese government benefited from the support of numerous partners for the revival of fish farming: more than 402 fish farmers and 18 NGOs benefited from the support of the World Bank, Belgian technical cooperation, the Bureau Central Coordination, and FAO. Interesting results have been obtained by these projects, but their perpetuation remains dependent on an intensification of the fish farming systems and the implementation of measures capable of enhancing local resources.
L'élevage en cage à faible niveau d'intrants: vers la sécurité alimentaire et L'amélioration du niveau de vie en zones rurales au Kenya.
Authors: Charo-Karisa Harrison , Munguti Jonathan M , Waidbacher Herwig , Liti David , Zollitsch Werner
Published: April 2021

Recent experiences and successes, including the decline in capture fisheries and the overall increase in aquaculture production, have sparked the development of commercial cage culture in Africa. This case study focuses on tilapia cage culture in the waters of Lake Victoria in Kenya and in secondary dams in the Lake Victoria basin. It highlights the challenges and innovations that Kenyan fish farmers and fishermen have demonstrated to achieve success. In particular, the study takes into account the public's ever-growing interest in and questioning of the sustainability of this farming system in the lake, both ecologically and environmentally. This study presents how fish farmers and researchers have successfully reared caged fish with low cost feed, to produce quality seeds, and to use locally available materials for the construction and safety of cages. Cage farming can be profitable in the Lake Victoria basin if the obstacles that arise as the process develops are gradually overcome.
Experiences and lessons learned from six years of government-led inland aquaculture development projects in northwest Namibia, 2004-2009.
Authors: Elago Panduleni Ndinelago
Published: April 2021

The Government of Namibia addresses food security and poverty reduction through the development of rural sectors, including fisheries and aquaculture. Freshwater aquaculture is recognized as a potential target for sustainable development. The Government of Namibia, together with the Government of Spain signed an agreement in 2003 to establish the Inland Aquaculture Centre (IAC), to demonstrate the possibilities of fish farming activities in the northwest of Namibia and in the country at large. Seven hundred new small-scale fish farms (SSFF's) were identified to participate in fish farming activities. Around 300+ farmers received an approximate total of 550,000 fingerlings over 5 years. With the extension of the project in 2007-2009 through strengthening of extension services on inland aquaculture development, under the 'Aquaculture in Northern Namibia' (ANN) Project umbrella, an extra 100 or more new farmers were identified. Results show that the extension services managed to assist in fish harvests for 114 SSFF's with 9560 kg of tilapia and 1556 kg of catfish harvested. The project's findings highlighted difficulties in accurately measuring fish production. Most fish farmers are located in a region where they only have enough water for fish culture during 5 months of the year. Also, many of the ponds they were using were incorrectly constructed and not suitable for fish farming. Farms in areas such as these, in hindsight, were unrealistic targets for aquaculture development, and it is the opinion of the author that it is important to re-direct effort and resources towards those able to farm with a good water supply for at least 10-12 months of the year. As of July 2010 the question remains unanswered; can fish farming in northwest Namibia be sustainable and economically viable with the current level of government extension, infrastructure and locally available resources? The author suggests that this will be possible in the next 5 years, once the government, together with the private sector and NGOs join to re-assess their current sets of objectives, which are, at present, too ambitious. Improvements could be made by implementing a better strategy, directing resources at a smaller number of sustainable, successful fish farmers rather than a larger number that include more inefficient farms. Large numbers of farms look good in policy documents, but spreading resources widely and inefficiently results in reduced net production and sustainability in the mid- to long-term.