bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluating earthquake-induced rockfall hazard near the Dead Sea Transform
Authors: Kanari Mor , Katz Oded , Weinberger Ram , Porat Naomi , Marco Shmuel
Published: April 2019

Abstract. We address an approach for rockfall hazard evaluation where the study area
resides below a cliff in an a priori exposure to rockfall hazard, but no
historical documentation of rockfall events is available and hence
important rockfall hazard parameters like triggering mechanism and
recurrence interval are unknown. We study the rockfall hazard for the town of Qiryat Shemona, northern Israel,
situated alongside the Dead Sea Transform, at the foot of the Ramim
escarpment. Numerous boulders are scattered on the slopes above the town,
while pre-town historical aerial photos reveal that boulders had reached
the location that is now within town limits. We use field observations and optically
stimulated luminescence dating of past rockfall events combined with computer
modeling to evaluate the rockfall hazard. For the analysis, we first mapped
the rockfall source and final downslope stop sites and compiled the boulder
size distribution. We then simulated the possible rockfall trajectories using
the field observed data to calibrate the simulation software by comparing
simulated and mapped boulder stop sites along selected slopes, while
adjusting model input parameters for best fit. The analysis reveals areas of
high rockfall hazard at the southwestern quarters of the town and also
indicates that in the studied slopes falling blocks would stop where the
slope angle decreases below 5–10∘. Age determination suggests that
the rockfalls were triggered by large (M>6) historical earthquakes.
Nevertheless, not all large historical earthquakes triggered rockfalls.
Considering the size distribution of the past rockfalls in the study area and
the recurrence time of large earthquakes in the region, we estimate a
probability of less than 5 % to be affected by a destructive rockfall
within a 50-year time window. Here we suggest a comprehensive method to evaluate rockfall hazard where
only past rockfall evidence exists in the field. We show the importance of
integrating spatial and temporal field observations to assess the extent of
rockfall hazard, the potential block size distribution and the rockfall
recurrence interval.
Impact of airborne cloud radar reflectivity data assimilation on kilometre-scale numerical weather prediction analyses and forecasts of heavy precipitation events
Authors: Borderies Mary , Caumont Olivier , Delanoë Julien , Ducrocq Véronique , Fourrié Nadia , Marquet Pascal
Published: April 2019

Abstract. This article investigates the potential of W-band radar reflectivity to
improve the quality of analyses and forecasts of heavy precipitation events
in the Mediterranean area. The “1D+3DVar” assimilation method,
operationally employed to assimilate ground-based precipitation radar data in
the Météo-France kilometre-scale numerical weather prediction (NWP)
model AROME, has been adapted to assimilate the W-band reflectivity measured
by the airborne cloud radar RASTA (Radar Airborne System Tool for Atmosphere)
during a 2-month period over the Mediterranean area. After applying a bias
correction, vertical profiles of relative humidity are first derived via a
1-D Bayesian retrieval, and
then used as relative humidity pseudo-observations in the 3DVar assimilation
system of AROME. The efficiency of the 1-D Bayesian method in retrieving
humidity fields is assessed using independent in-flight humidity
measurements. To complement this study, the benefit brought by consistent
thermodynamic and dynamic cloud conditions has been investigated by
separately and jointly assimilating the W-band reflectivity and horizontal
wind measurements collected by RASTA in the 3 h 3DVar assimilation system of
AROME. The data assimilation experiments are conducted for a single heavy precipitation event
and then also for 32 cases. Results indicate that the W-band reflectivity has a larger
impact on the humidity, temperature and pressure fields in the analyses compared to the
assimilation of RASTA wind data alone. Besides, the analyses get closer to independent
humidity observations if the W-band reflectivity is assimilated alone or jointly with
RASTA wind data. Nonetheless, the impact of the W-band reflectivity decreases more
rapidly as the forecast range increases when compared to the assimilation of RASTA wind
data alone. Generally, the joint assimilation of the W-band reflectivity with wind data
results in the best improvement in the rainfall precipitation forecasts. Consequently,
results of this study indicate that consistent thermodynamic and dynamic cloud conditions
in the analysis leads to an improvement of both model initial conditions and forecasts.
Even though to a lesser extent, the assimilation of the W-band reflectivity alone also
results in a slight improvement of the rainfall precipitation forecasts.
Is Colobus guereza gallarum a valid endemic Ethiopian taxon?
Authors: Zinner Dietmar , Tesfaye Dereje , Stenseth Nils C. , Bekele Afework , Mekonnen Aemro , Doeschner Steve , Atickem Anagaw , Roos Christian
Published: April 2019

Abstract. Black-and-white colobus (Colobus guereza Rüppell,
1835) are arboreal
Old World monkeys inhabiting large parts of the deciduous and evergreen
forests of sub-Saharan Africa. Two of the eight subspecies of Colobus guereza are endemic to Ethiopia: C. g. gallarum and C. g. guereza.
However, the validity of the Ethiopian taxa is debated and observed
morphological differences were attributed to clinal variation within
C. g. guereza. To date, no molecular phylogeny of the Ethiopian
guerezas is available to facilitate their taxonomic classification. We used
mitochondrial DNA markers from 94 samples collected across Ethiopia to
reconstruct a phylogeny of respective mitochondrial lineages. In our
phylogenetic reconstruction, augmented by orthologous sequence information of
non-Ethiopian black-and-white colobus from GenBank, we found two major
Ethiopian mitochondrial clades, with one being largely congruent with the distribution
of C. g. guereza. The second clade was found only at two locations
in the eastern part of the putative range of C. g. gallarum. This
second lineage clustered with the lowland form, C. g. occidentalis, from central Africa, whereas the
C. g. guereza lineages clustered with C. g. caudatus and C. g. kikuyuensis
from Kenya and northern Tanzania. These two
guereza lineages diverged around 0.7 million years ago. In addition,
mitochondrial sequence information does not support unequivocally a distinction
of C. g. caudatus and C. g. kikuyuensis. Our findings
indicate a previous biogeographic connection between the ranges of C. g. occidentalis
and C. g. gallarum and a possible secondary
invasion of Ethiopia by members of the C. g. guereza–C. g. caudatus–C. g. kikuyuensis clade. Given these phylogenetic
relationships, our study supports the two-taxa hypothesis, making C. g. gallarum
an Ethiopian endemic, and, in combination with the taxon's very
restricted range, makes it one of the most endangered subspecies of
black-and-white colobus.
A revised map of volcanic units in the Oman ophiolite: insights into the architecture of an oceanic proto-arc volcanic sequence
Authors: Belgrano Thomas M. , Diamond Larryn W. , Vogt Yves , Biedermann Andrea R. , Gilgen Samuel A. , Al-Tobi Khalid
Published: April 2019

Abstract. Recent studies have revealed genetic similarities between Tethyan ophiolites and oceanic proto-arc sequences formed above nascent subduction zones. The Semail ophiolite (Oman–U.A.E.) in particular can be viewed as an analogue for this proto-arc crust. Though proto-arc magmatism and the mechanisms of subduction-initiation are of great interest, insight is difficult to gain from drilling and limited surface outcrops in submarine fore-arcs. In contrast, the Semail ophiolite, in which the 3–5 km thick upper-crustal succession is exposed in an oblique cross-section, presents an opportunity to assess the architecture and volumes of different volcanic rocks that form during the protoarc stage. To determine the distribution of the volcanic rocks and to aid exploration for the volcanogenic massive sulphide (VMS) deposits that they host, we have re-mapped the volcanic units of the Semail ophiolite by integrating new field observations, geochemical analyses and geophysical interpretations with pre-existing geological maps. By linking the major element compositions of the volcanic units to rock magnetic properties, we were able to use aeromagnetic data to infer the extension of each outcropping unit below sedimentary cover, resulting in in a new map showing 2100 km2 of upper-crustal bedrock. Whereas earlier maps distinguished two main volcanostratigraphic units, we have distinguished four, recording the progression from early spreading-axis basalts (Geotimes) through to axial to off-axial depleted basalts (Lasail), to post-axial tholeiites (Tholeiitic Alley) and finally boninites (Boninitic Alley). Geotimes (Phase 1) axial dykes and lavas make up ~55 vol% of the Semail upper crust, whereas post-axial (Phase 2) lavas constitute the remaining ~ 45 vol % and ubiquitously cover the underlying axial crust. The Semail boninites occur as discontinuous accumulations up to 2 km thick at the top of the sequence and constitute ~ 15 vol % of the upper crust. The new map provides a basis for targeted exploration of the gold-bearing VMS deposits hosted by these boninites. The thickest boninite accumulations occur in the Fizh block, where magma ascent occurred along crustal-scale faults that are connected to shear zones in the underlying mantle rocks, which in turn are associated with economic chromitite deposits. Locating major boninite feeder zones may thus be an indirect means to explore for chromitites in the underlying mantle.
The Influence of Political Costs on Income Smoothing: Evidence From Listed Egyptian Firms
Authors: Soliman Walid Shehata
Published: April 2019

Income smoothing is affected by some factors, one of these factors is political costs (PCs) which firms may pay to get information, trading, and negotiation which is imposed by the decision making and legislating authorities. Hence, the association between PCs and income smoothing is tested by focusing on Egyptian Stock Exchange (EGX), especially EGX 30, which included the most active firms, for a ten-year period from 2006 to 2015 for 63 firms, including 417 completed observations, the sample represented 10 different sectors. Two main hypotheses were formulated and tested, the first hypothesis consists of four sub-hypotheses, it was tested using multiple regression analysis, and the second hypothesis tested by testing the moderating effect of Egyptian revolution 2011 on the association between PCs and income smoothing. The findings are; first, PCs proxies have a positive and significant effect on income smoothing, second, there is a negative and significant moderating effect of Egyptian revolution 2011 on the association between firm size only and income smoothing.
E-Learning and Transformative Learning in Adult Training
Authors: Pavlakou Evgenia , Kalachanis Konstantinos , Kefali Sophia , Tsiouni Eleni
Published: April 2019

Transformative learning refers to the process of transforming frameworks through which adults interpret the experiences, values, feelings, and shape their actions and living conditions, combined with the cultural context in which they are socialized. In this process the adult re-evaluates the experiences he has gained since his childhood, resulting in a new knowledge through critical thinking. Transformative learning is applied to adult education where the aim is to acquire new professional skills based on the needs of learners. The ability to apply distance learning asynchronously releases it from spatial or temporal constraints, making it suitable for the implementation of transformative learning. The trainer can take advantage of the technological applications (video, presentations, etc. asynchronous communication, and e mail) and authoritative scientific sources of the internet. This activates the trainee in a heuristic course towards the knowledge that will move his interest and will change his / her perceptual systems by leading him / herself into self-realization. Therefore, the use of distance learning in adult education is fully in line with the principles of transforming learning.
The effectiveness of a psycho-educational nursing intervention on illness perception, knowledge and expressed emotion of caregivers of patients with first episode psychosis
Authors: Abo Shereda Hanaa Mohamed , Shattla Safaa Ibrahim , Amer Hemat Mostafa , Kasemy Zeinab Abdel Aziz
Published: April 2019

Background: Psycho educational nursing intervention to families of patients with first-episode psychosis is highly recommended to assist families to overcome feelings of stress, guilt, stigma, loss of control and to promote recovery of patients. The aim of the study was to evaluate the effect of psych educational nursing intervention on illness perception, level of knowledge and level of expressed emotion of caregivers of patients with first episode psychosis.Methods: Research design: a quasi-experimental research design (one group pre-posttest) was used to achieve the aim of the study. The study was conducted at three psychiatric and mental health governmental outpatient clinics. A convenience sample of 50 caregivers was used. Data was collected using socio demographic data questionnaire, family questionnaire, knowledge questionnaire, and illness perception questionnaire.Results: There were clinically significant improvement among the caregivers' level of knowledge and illness perception at post test of psycho educational nursing intervention than before intervention, while level of expressed emotion was improved post the psycho educational nursing intervention but without obvious significant difference.Conclusions & Recommendation: Psycho educational nursing intervention was effective in improving caregivers' level of knowledge, illness perception and expressed emotion. The study recommended to urgently utilize psycho educational nursing intervention to all caregivers of patient with first episode psychosis in all psychiatric hospitals.
Intrasite Antibiotic Powder for the Prevention of Surgical Site Infection in Extremity Surgery: A Systematic Review
Authors: Fernicola Stephen D. , Elsenbeck Michael J. , Grimm Patrick D. , Pisano Alfred J. , Wagner Scott C.
Published: April 2019

Introduction:

Although the role of intrasite antibiotic powder in preventing surgical site infections (SSIs) has been extensively explored in spinal surgery, it remains underevaluated in the other orthopaedic subspecialties. This systematic review examines the utilization of intrawound antibiotic powder as a prophylactic measure against SSIs in orthopaedic procedures.

Methods:

Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, electronic searches were conducted on Ovid MEDLINE, and PubMed. Only English language, nonspine clinical studies published before May 2018 were included.

Results:

The initial search identified 179 individual citations, and 11 studies met the eligibility criteria. All included studies were level III retrospective studies. Represented subspecialties included total joint arthroplasty, upper extremity, foot and ankle, and trauma. Eight studies demonstrated a statistically significant decrease in SSIs with the use of intrasite antibiotic powder.

Discussion:

There are no current guidelines for the use of intrasite antibiotic powder for the prevention of SSIs in orthopaedic procedures. Despite the lack of high-quality evidence available in the literature, published smaller studies do suggest a significant protective effect. However, recommendations with regard to this technique after common orthopaedic procedures cannot yet be made.
Continuous Time Markov Chain Model for Cholera Epidemic Transmission Dynamics
Authors: Marwa Yohana Maiga , Mbalawata Isambi Sailon , Mwalili Samuel
Published: April 2019

This paper is concern with modeling cholera epidemic. Despite the advances made in understanding this disease and its treatment, cholera continues to be a major public health problem in many countries. Deterministic and stochastic models emerged in modeling of cholera epidemic, in order to understand the mechanism by which cholera disease spread, conditions for cholera disease to have minor and large outbreaks. We formulate a continuous time Markov chain model for cholera epidemic transmission from the deterministic model. The basic reproduction number (R0) and the extinction thresholds of corresponding cholera continuous time Markov chain model are derived under certain assumptions. We find that, the probability of extinction (no outbreak) is 1 if R0 < 1, but less than 1 if R0 > 1. We also carry out numerical simulations using Gillespie algorithm and Runge–Kutta method to generate the sample path of cholera continuous time Markov chain model and the solution of ordinary differential equation respectively. The results show that the sample path of continuous time Markov chain model fluctuates within the solution of the ordinary differential equation.
Eksperymentalna weryfikacja metody wykonywania otworów strzałowych technologią wybuchową z zastosowaniem głowic kumulacyjnych
w warunkach podziemnych
Authors: Magier Mariusz , Zielenkiewicz Mariusz , Hildebrandt Robert , Pytlik Mateusz , Sobala Jacek , Szastok Michał , Burian Wojciech , Kulasa Joanna , Juszczyk Barbara , Janiszewski Jacek , Lachmajer Jerzy
Published: April 2019

Głównym sposobem urabiania skał w górnictwie podziemnym i odkrywkowym jest wykorzystanie materiałów wybuchowych. Optymalnym sposobem urobienia skały jest w tym przypadku wprowadzenie ładunku do otworu strzałowego. Proces wiercenia otworów w po-równaniu do załadunku i detonacji materiału wybuchowego jest najbardziej czasochłonną operacją. Dodatkowo względy techniczne mogą utrudniać lub uniemożliwiać wykonanie otworów strzałowych. Wyeliminowanie proce-su wiercenia poprzez zastosowanie ładunków kumulacyjnych może znacząco wpływać na zwiększenie postępów drążenia. Niniejsza praca ma na celu określenie możliwości wykonywania otworów strzałowych wykorzystując głowice kumulacyjne amunicji przeciw-pancernej. Wyniki przeprowadzonych badań będą służyły do opracowania, wykonania i wprowadzenia do górnictwa nowego typu ładunków kumulacyjnych, które w przyszłości umożliwią zwiększenie efektywności górnictwa przy utrzymaniu lub obniżeniu kosztów.
Reduction of threading dislocation density and suppression of cracking in sputter-deposited AlN templates annealed at high temperatures
Authors: Uesugi Kenjiro , Hayashi Yusuke , Shojiki Kanako , Miyake Hideto
Published: April 2019

Combination of sputter deposition and high-temperature annealing is a promising technique for preparing AlN templates with a low threading dislocation density (TDD) at a lower film thickness compared to those prepared by the conventional metalorganic vapor phase epitaxy. However, cracking of AlN films during annealing is a critical issue. In this study, we controlled the residual stress of the sputter-deposited AlN films by modifying the sputtering conditions. Consequently, the occurrence of cracking was effectively suppressed. By optimizing the fabricating conditions, a TDD of 2.07 × 108 cm−2 was achieved for the AlN template with a thickness of 480 nm.
Evaluation of the extent of damage to the esophageal wall caused by press-through package ingestion
Authors: Tamura Takuya , Okamoto Hajime , Suzuki Toyoaki , Nakanishi Yoichi , Sugiyama Daisuke
Published: April 2019

Press-through package (PTP) is the most common accidentally ingested foreign body in Japan. Accidental ingestion of PTP can result in esophageal damage. An approach for evaluating the risk of esophageal injury has not been established. Therefore, we used porcine esophageal tissue and silicone sheets to establish a method for assessing the risk of esophageal damage on accidental PTP ingestion. We pathologically evaluated porcine lower esophageal tissue using a scratch tester. Using porcine esophageal tissue, scratch tests were performed with 4 test objects and pathological damage was compared. It was assumed that each object was accidentally ingested. The objects were polyvinylidene chloride (PVDC)-coated polyvinyl chloride (PVC) PTP, soft PThPa, round PTP, and a disposable scalpel. The porcine esophagus was replaced with a silicon sheet, and an automatic friction machine was used for quantitative evaluation. The silicon sheet was scratched using HHS 2000 with 750-g load at 50 mm/min. We investigated the frictional force exerted on the surface for each of the objects. The degree of damage (depth) was the highest for the disposable scalpel, followed by PVDC-coated PVC PTP, while the degree of damage (depth) was the lowest for soft PThPa and round PTP. The mean frictional forces on the silicon sheet were 524.0 gf with PVDC-coated PTP, 323.5 gf with soft PThPa, 288.7 gf with round PTP, and 922.7 gf with the disposable scalpel. We developed approaches to qualitatively and quantitatively evaluate the risk of esophageal damage after accidental PTP ingestion. Our findings indicate that the risk of gastrointestinal damage after accidental PTP ingestion is low with soft PTP and round PTP.
Prevalence of Hepatitis B amgonst Asymptomatic Persons Visiting Braithwait Memorial Specialist Hospital (BMSH), Nigeria
Authors: Fajoyomi B. U. , Onwukwe C. D. , Alukara G.
Published: April 2019

Hepatitis B virus infection is a major public health problem; it infects more than 400 million people worldwide. In recent years, the overall prevalence of this virus has declined due to its vaccine that is now in circulation. Hepatitis B virus causes liver injury by an immune response against the virus-infected liver cells but it’s not directly cytopathic, but immunosuppression enhances replication and can lead to direct cytotoxicity. In this study, A survey was conducted amongst 200 randomly selected general out-patients within the ages of 10-80 years with pregnant women inclusive who are attending the Braithwait Memorial Specialist Hospital (BMSH) Nigeria, in order to ascertain the prevalence of Hepatitis B virus infection among patients attending Braithwait Memorial Specialist Hospital in Rivers State, Nigeria and the general knowledge of the people about this highly infectious disease. Sera collected were screened for the presence of Hepatitis B surface antigen () using Labacon Diagnostic Test Strip (Hangzhou Biotest Biotech Co., Ltd China) and a total of 32 out of the 200 respondents tested positive of Hepatitis B surface antigen, giving a percentage of 16% (32/200).Questionnaires were distributed to the subjects in order to ascertain their perceptions about the disease, and to obtain useful socio-demographic information. There was a poor management and prevention control of the disease and this may have accounted for the prevalence of 16% in the study population.
Wavelet Entropy Based Probabilistic Neural Network for Classification
Authors: Daqrouq Khaled , Chen Sheng , Khalaf Emad , Morfeqa Ali , Sheikha Muntasir , Qatawneh Abdulrohman , AL-Khateeb Abdulhameed
Published: April 2019

Recently, wavelet transform (WT) has been enormously effectual in various scientific fields. As a matter of fact, WT has overcome the FFT in the difficult nature data tackling. A wavelet entropy based probabilistic neural network (PNN) for classification applications is proposed. Specifically, wavelet transform is performed on the original input feature data, and the entropy values of the wavelet decomposition signals are then extracted to use as the input to the PNN classifier. Two benchmark data sets, Breast Cancer and Diabetes, are used to demonstrate the efficiency of our proposed wavelet entropy based PNN (WEPNN) classifier. The test classification rates of 80.3% and 77.0% are achieved respectively for the two data sets using the WEPNN with Shannon entropy. Other published methods are used for comparison. The method is promising. For results accuracy enhancement, large data set might be utilized in the future work.
Food Attractants Used in the Fruit Fly Monitoring (Diptera: Tephritidae) in a Commercial Orchard of Psidium guajava
Authors: Alves Júlio César G. , De Brito Carlos Henrique , Oliveira Robério De , Corsato Clarice D. A. , Silva Jakellyne F. da , Barbosa Vinícius De O. , Batista Jacinto De L.
Published: April 2019

Fruit flies are considered an important fruit pest for world fruit production because they cause significant losses to the production and limit fruit free transport due to quarantine restrictions imposed by importing countries. Fruit flies population dynamics knowledge of a particular region is an important factor in the management of this pest. Traps are devices created to attract and capture flies by sexual attraction or food attraction, both put inside the trap. It reduces fruit flies population in the orchard, decreasing the pressure and chances of an infestation. This research aimed to evaluate the efficiency of food baits in the fruit flies capture on guava plant culture, in order to establish an adequate program for this pest in the municipality of Nova Floresta – PB. Monitoring of the adult fruit-fly was performed with aid of plastic traps of the type PET bottle 330 mL of Bio Anastrepha® 5.0%, 440 mL of sugarcane molasses diluted to 10.0% and 520 mL of 30.0% fruit juice (guava). The traps were installed in the central part of the trees, approximately 1.50 m above ground. Every 15 days adult fruit flies were caught, the occasion that food baits were replaced. From these data were evaluated: efficiency of food baits, MAD index (flies/trap/day) and food baits cost-benefit analysis. The best food attractant at the lowest cost was Bio Anastrepha® at 5.0%, with a catch margin of 63.83%, followed by fruit juice at 30.0% and sugarcane molasses at 10.0%, with 34.04% and 2.13%, respectively.
Use of Tannery Sludge and Urban Compost as a Substrate for Sweet Pepper Seedlings
Authors: Berilli Sávio da Silva , Valadares Fernanda Vargas , Sales Ramon Amaro de , Ulisses Alessandra De Fatima , Pereira Rodrigo Martins , Dutra Geraldo José Alves , Da Silva Matheus Wandermurem , Gabriel Berilli Ana Paula Cândido , Salles Rodrigo Amaro de , Almeida Rafael Nunes de
Published: April 2019

There are many commercial substrates available in the market of vegetables nowadays. However, a growing pressure turned for sustainability in farming, promotes a line of utilization of waste with agricultural potential, such as the use of urban waste compost and tannery sludge, which, when available, can be used as sources of compost and alternative organic matter. The objective of this study was to evaluate the potential of tannery sludge associated with the urban waste compost in the substrate composition of sweet pepper seedlings, especially regarding emergence, development, and quality of seedlings. The experimental design was a randomized block design with six replications and eight treatments. The treatments consisted of mixtures of the residue of dehydrated tannery sludge and urban waste compost, varying in the proportions of 10%, 30%, 50%, 70%, 90% and 100% of each, as well as the use of a commercial substrate as a conventional treatment for the comparisons. Graphs were performed through linear regression analysis for the treatment of statistical data. The percentage of emergence, development, and quality of seedlings were evaluated 54 days after planting. The alternative substrates showed high potential in the production of seedlings, in which all the combinations used in the study were superior to the conventional treatment, except the germination, which did not present difference. The range for the use of tannery sludge in the preparation of substrates for sweet pepper seedlings is between 32.7 and 48.2% in a mixture with urban waste compost. The plants presented better quality with the use of 46.0% of tannery sludge and 54.0% of urban compost in the preparation of the substrate.
Microporous Drug‐Eluting Large Silk Particles Through Cryo‐Granulation
Authors: Rodionov ILia , Abdullah Nadia , Kaplan David L.
Published: April 2019

A facile method for the preparation of large, microporous, drug‐loaded particles is presented. High shear bollus injections of silk with cross‐linker and drug colloids into super‐cooled hexane are utilized to trigger phase separation of silk droplets, followed by immediate freezing at –60 °C. A subsequent –20 °C freeze‐thaw of the frozen droplets resulted in self‐assembly (crystallization) of the silk. The silk particles developed an internal interconnected microporous morphology with 0.1–10 μm in diameter pores. The silk particles ranged in diameter from 100 to 1300 μm, with particle mean diameter and polydispersity controlled by the starting concentration of the cross‐linking agent and silk, the rheology of the reaction mixture, and the injection pressure (80–300 kPa). Cryogranulation provided a one‐step process to produce microporous meso‐scale silk particles with encapsulated drugs, such as doxorubicin chloride (DoxR), tobramycin sulfate (TS), kanamycin sulfate (KS), or gentamicin sulfate (GS). Almost 100% drug encapsulation efficiency is achieved in the process, and subsequent release profiles depended on the starting concentration of both the drug, silk, and pH of the elution medium. Kirby–Bauer tests and bioluminescent imaging confirmed the retention of anti‐bacterial potency of the antibiotics pre‐encapsulated in the cryo‐particles, and macroparticles cytocompatibility toward human fibroblast and kidney cells.
Room‐Temperature Meniscus Coating of >20% Perovskite Solar Cells: A Film Formation Mechanism Investigation
Authors: Hu Hanlin , Ren Zhiwei , Fong Patrick W. K. , Qin Minchao , Liu Danjun , Lei Dangyuan , Lu Xinhui , Li Gang
Published: April 2019

Perovskite solar cells (PSCs) are ideally fabricated entirely via a scalable solution process at low temperatures to realize the promise of simple manufacturing, low‐cost processing, compatibility with flexible substrates, and perovskite‐based tandem solar cells. However, high‐quality photoactive perovskite thin films under those processing conditions is a challenge. Here, a laminar air‐knife‐assisted room‐temperature meniscus coating approach that enables one to control the drying kinetics during the solidification process and achieve high‐quality perovskite films and solar cells is devised. Moreover, this approach offers a solid model platform for in situ UV–vis and microscopic investigation of the perovskite film drying kinetics, which provide rich insights correlating the degree of supersaturation, the nucleation, and growth rate during the kinetic drying process, and ultimately, the film morphology and performance of the solar cell devices. Manufacturing friendly, antisolvent‐free room‐temperature coating of hysteresis‐free PSCs with a power conversion efficiency of 20.26% for 0.06 cm2 and 18.76% for 1 cm2 devices is demonstrated.
Efficient and Stable CsPbI3 Solar Cells via Regulating Lattice Distortion with Surface Organic Terminal Groups
Authors: Wu Tianhao , Wang Yanbo , Dai Zhensheng , Cui Danyu , Wang Tao , Meng Xiangyue , Bi Enbing , Yang Xudong , Han Liyuan
Published: April 2019

All‐inorganic cesium lead iodide perovskites (CsPbI3) are promising wide‐bandgap materials for use in the perovskite/silicon tandem solar cells, but they easily undergo a phase transition from a cubic black phase to an orthorhombic yellow phase under ambient conditions. It is shown that this phase transition is triggered by moisture that causes distortion of the corner‐sharing octahedral framework ([PbI6]4−). Here, a novel strategy to suppress the octahedral tilting of [PbI6]4− units in cubic CsPbI3 by systematically controlling the steric hindrance of surface organic terminal groups is provided. This steric hindrance effectively prevents the lattice distortion and thus increases the energy barrier for phase transition. This mechanism is verified by X‐ray diffraction measurements and density functional theory calculations. Meanwhile, the formation of an organic capping layer can also passivate the surface electronic trap states of perovskite absorber. These modifications contribute to a stable power conversion efficiency (PCE) of 13.2% for the inverted planar perovskite solar cells (PSCs), which is the highest efficiency achieved by the inverted‐structure inorganic PSCs. More importantly, the optimized devices retained 85% of their initial PCE after aging under ambient conditions for 30 days.
Anti‐Ambipolar Transport with Large Electrical Modulation in 2D Heterostructured Devices
Authors: Cheng Ruiqing , Yin Lei , Wang Feng , Wang Zhenxing , Wang Junjun , Wen Yao , Huang Wenhao , Sendeku Marshet Getaye , Feng Liping , Liu Yufang , He Jun
Published: April 2019

Van der Waals materials and their heterostructures provide a versatile platform to explore new device architectures and functionalities beyond conventional semiconductors. Of particular interest is anti‐ambipolar behavior, which holds potentials for various digital electronic applications. However, most of the previously conducted studies are focused on hetero‐ or homo‐ p–n junctions, which suffer from a weak electrical modulation. Here, the anti‐ambipolar transport behavior and negative transconductance of MoTe2 transistors are reported using a graphene/h‐BN floating‐gate structure to dynamically modulate the conduction polarity. Due to the asymmetric electrical field regulating effect on the recombination and diffusion currents, the anti‐ambipolar transport and negative transconductance feature can be systematically controlled. Consequently, the device shows an unprecedented peak resistance modulation factor (≈5 × 103), and effective photoexcitation modulation with distinct threshold voltage shift and large photo on/off ratio (≈104). Utilizing this large modulation effect, the voltage‐transfer characteristics of an inverter circuit variant are further studied and its applications in Schmitt triggers and multivalue output are further explored. These properties, in addition to their proven nonvolatile storage, suggest that such 2D heterostructured devices display promising perspectives toward future logic applications.
Quasicrystal Photonic Metasurfaces for Radiation Controlling of Second Harmonic Generation
Authors: Tang Yutao , Deng Junhong , Li King Fai , Jin Mingke , Ng Jack , Li Guixin
Published: April 2019

Photonic metasurfaces, a kind of 2D structured medium, represent a novel platform to manipulate the propagation of light at subwavelength scale. In linear optical regime, many interesting topics such as planar meta‐lenses, metasurface optical holography, and so on have been widely investigated. Recently, metasurfaces have gone into the nonlinear optical regime. While it is recognized that the local symmetry of the meta‐atoms plays a vital role in determining the polarization, phase, and intensity of the nonlinear waves, much less attention has been paid to the global symmetry of the nonlinear metasurfaces. According to the Penrose tiling and the newly proposed hexagonal quasicrystalline tiling, nonlinear optical quasicrystal metasurfaces are designed and fabricated based on the geometric‐phase‐controlled plasmonic meta‐atoms with local rotational symmetry. It is found that the far‐field radiation behavior of second harmonic generation waves are determined by both the tiling schemes of quasicrystal metasurfaces and the local symmetry of meta‐atoms they consist of. The proposed concept may open new avenues for designing nonlinear optical sources with metasurface crystals.
Graphitic Carbon Nitride (g‐C3N4)‐Derived N‐Rich Graphene with Tuneable Interlayer Distance as a High‐Rate Anode for Sodium‐Ion Batteries
Authors: Liu Jinlong , Zhang Yaqian , Zhang Lei , Xie Fangxi , Vasileff Anthony , Qiao Shi‐Zhang
Published: April 2019

Heteroatom‐doped carbon materials with expanded interlayer distance have been widely studied as anodes for sodium‐ion batteries (SIBs). However, it remains unexplored to further enlarge the interlayer spacing and reveal the influence of heteroatom doping on carbon nanostructures for developing more efficient SIB anode materials. Here, a series of N‐rich few‐layer graphene (N‐FLG) with tuneable interlayer distance ranging from 0.45 to 0.51 nm is successfully synthesized by annealing graphitic carbon nitride (g‐C3N4) under zinc catalysis and selected temperature (T = 700, 800, and 900 °C). More significantly, the correlation between N dopants and interlayer distance of resultant N‐FLG‐T highlights the effect of pyrrolic N on the enlargement of graphene interlayer spacing, due to its stronger electrostatic repulsion. As a consequence, N‐FLG‐800 achieves the optimal properties in terms of interlayer spacing, nitrogen configuration and electronic conductivity. When used as an anode for SIBs, N‐FLG‐800 shows remarkable Na+ storage performance with ultrahigh rate capability (56.6 mAh g−1 at 40 A g−1) and excellent long‐term stability (211.3 mAh g−1 at 0.5 A g−1 after 2000 cycles), demonstrating the effectiveness of material design.
Seed‐Layer‐Free Atomic Layer Deposition of Highly Uniform Al2O3 Thin Films onto Monolayer Epitaxial Graphene on Silicon Carbide
Authors: Schilirò Emanuela , Lo Nigro Raffaella , Roccaforte Fabrizio , Deretzis Ioannis , La Magna Antonino , Armano Angelo , Agnello Simonpietro , Pecz Bela , Ivanov Ivan G. , Yakimova Rositsa , Giannazzo Filippo
Published: April 2019

Atomic layer deposition (ALD) is the method of choice to obtain uniform insulating films on graphene for device applications. Owing to the lack of out‐of‐plane bonds in the sp2 lattice of graphene, nucleation of ALD layers is typically promoted by functionalization treatments or predeposition of a seed layer, which, in turn, can adversely affect graphene electrical properties. Hence, ALD of dielectrics on graphene without prefunctionalization and seed layers would be highly desirable. In this work, uniform Al2O3 films are obtained by seed‐layer‐free thermal ALD at 250 °C on highly homogeneous monolayer (1L) epitaxial graphene (EG) (>98% 1L coverage) grown on on‐axis 4H‐SiC(0001). The enhanced nucleation behavior on 1L graphene is not related to the SiC substrate, but it is peculiar of the EG/SiC interface. Ab initio calculations show an enhanced adsorption energy for water molecules on highly n‐type doped 1L graphene, indicating the high doping of EG induced by the underlying buffer layer as the origin of the excellent Al2O3 nucleation. Nanoscale current mapping by conductive atomic force microscopy shows excellent insulating properties of the Al2O3 thin films on 1L EG, with a breakdown field > 8 MV cm−1. These results will have important impact in graphene device technology.
Biocompatibility Considerations in the Design of Graphene Biomedical Materials
Authors: Bullock Christopher J. , Bussy Cyrill
Published: April 2019

Graphene‐based materials (GBM) have outstanding properties that have proven highly beneficial in several proof‐of‐concept investigations on their biomedical potential. They can be used as suspensions of nanosheets for nanomedicine purposes as well as components of macroscale products in medical devices or tissue engineering/regenerative medicine products. However, the clinical translation of these preclinical concepts is hampered by the incomplete understanding of the biocompatibility of GBM in general, and the limited or lack of safety considerations in most preclinical proof‐of‐concept studies. In this review, the main safety aspects to be considered for the design of biocompatible materials based on GBM that interface with the human body or its fluids are outlined. Guidance to overcome some of the unique challenges presented by graphene biomedical materials are provided, stressing the need to consider safety challenges as early as possible in the design phase of the candidate biomedical product to raise its chance for clinical translation.
Structurally Tunable Reduced Graphene Oxide Substrate Maintains Mouse Embryonic Stem Cell Pluripotency
Authors: Zhao Jinping , Tang Mingliang , Cao Jing , Ye Dan , Guo Xudong , Xi Jiajie , Zhou Yi , Xia Yuchen , Qiao Jing , Chai Renjie , Yang Xiaowei , Kang Jiuhong
Published: April 2019

Culturing embryonic stem cells (ESCs) in vitro usually requires animal‐derived trophoblast cells, which may cause pathogenic and immune reactions; moreover, the poor repeatability between batches hinders the clinical application of ESCs. Therefore, it is essential to synthesize a xenogeneic‐free and chemically well‐defined biomaterial substrate for maintaining ESC pluripotency. Herein, the effects of structurally tunable reduced graphene oxide (RGO) substrates with different physicochemical properties on ESC pluripotency are studied. Colony formation and CCK‐8 assays show that the RGO substrate with an average 30 µm pore size promotes cell survival and proliferation. The unannealed RGO substrate promotes ESC proliferation significantly better than the annealed substrate due to the interfacial hydrophilic groups. The RGO substrate can also maintain ESC for a long time. Additionally, immunofluorescence staining shows that ESCs cultured on an RGO substrate highly express E‐cadherin and β‐catenin, whereas after being modified by Dickkopf‐related protein 1, the RGO substrate is unable to sustain ESC pluripotency. Furthermore, the cell line that interferes with E‐cadherin is also unable to maintain pluripotency. These results confirm that the RGO substrate maintains ESC pluripotency by promoting E‐cadherin‐mediated cell–cell interaction and Wnt signaling.
Structural Engineering of Low‐Dimensional Metal–Organic Frameworks: Synthesis, Properties, and Applications
Authors: Liu Wenxian , Yin Ruilian , Xu Xilian , Zhang Lin , Shi Wenhui , Cao Xiehong
Published: April 2019

Low‐dimensional metal–organic frameworks (LD MOFs) have attracted increasing attention in recent years, which successfully combine the unique properties of MOFs, e.g., large surface area, tailorable structure, and uniform cavity, with the distinctive physical and chemical properties of LD nanomaterials, e.g., high aspect ratio, abundant accessible active sites, and flexibility. Significant progress has been made in the morphological and structural regulation of LD MOFs in recent years. It is still of great significance to further explore the synthetic principles and dimensional‐dependent properties of LD MOFs. In this review, recent progress in the synthesis of LD MOF‐based materials and their applications are summarized, with an emphasis on the distinctive advantages of LD MOFs over their bulk counterparties. First, the unique physical and chemical properties of LD MOF‐based materials are briefly introduced. Synthetic strategies of various LD MOFs, including 1D MOFs, 2D MOFs, and LD MOF‐based composites, as well as their derivatives, are then summarized. Furthermore, the potential applications of LD MOF‐based materials in catalysis, energy storage, gas adsorption and separation, and sensing are introduced. Finally, challenges and opportunities of this fascinating research field are proposed.
Anchoring Pt Single Atoms on Te Nanowires for Plasmon‐Enhanced Dehydrogenation of Formic Acid at Room Temperature
Authors: Han Lei , Zhang Leijie , Wu Hong , Zu Hualu , Cui Peixin , Guo Jiasheng , Guo Ruihan , Ye Jian , Zhu Junfa , Zheng Xusheng , Yang Liuqing , Zhong Yici , Liang Shuquan , Wang Liangbing
Published: April 2019

Formic acid (HCOOH), as a promising hydrogen carrier, is renewable, safe, and nontoxic. However, the catalytic dehydrogenation of HCOOH is typically conducted at elevated temperature. Here, HCOOH decomposition is successfully achieved for hydrogen production on the developed Pt single atoms modified Te nanowires with the Pt mass loading of 1.1% (1.1%Pt/Te) at room temperature via a plasmon‐enhanced catalytic process. Impressively, 1.1%Pt/Te delivers 100% selectivity for hydrogen and the highest turnover frequency number of 3070 h−1 at 25 °C, which is significantly higher than that of Pt single atoms and Pt nanoclusters coloaded Te nanowires, Pt nanocrystals decorated Te nanowires, and commercial Pt/C. A plasmonic hot‐electron driven mechanism rather than photothermal effect domains the enhancement of catalytic activity for 1.1%Pt/Te under light. The transformation of HCOO* to CO2δ
−* on Pt atoms is proved to be the rate‐determining step by further mechanistic studies. 1.1%Pt/Te exhibits tremendous catalytic activity toward the decomposition of HCOOH owing to its plasmonic hot‐electron driven mechanism, which efficiently stimulates the rate‐determining step. In addition, hot electrons generated by the Te atoms nearby Pt single atoms are regarded to directly inject into the reactants adsorbed and activated on Pt single atoms.
A Magnesium‐Enriched 3D Culture System that Mimics the Bone Development Microenvironment for Vascularized Bone Regeneration
Authors: Lin Sihan , Yang Guangzheng , Jiang Fei , Zhou Mingliang , Yin Shi , Tang Yanmei , Tang Tingting , Zhang Zhiyuan , Zhang Wenjie , Jiang Xinquan
Published: April 2019

The redevelopment/regeneration pattern of amputated limbs from a blastema in salamander suggests that enhanced regeneration might be achieved by mimicking the developmental microenvironment. Inspired by the discovery that the expression of magnesium transporter‐1 (MagT1), a selective magnesium (Mg) transporter, is significantly upregulated in the endochondral ossification region of mouse embryos, a Mg‐enriched 3D culture system is proposed to provide an embryonic‐like environment for stem cells. First, the optimum concentration of Mg ions (Mg2+) for creating the osteogenic microenvironment is screened by evaluating MagT1 expression levels, which correspond to the osteogenic differentiation capacity of stem cells. The results reveal that Mg2+ selectively activates the mitogen‐activated protein kinase/extracellular regulated kinase (MAPK/ERK) pathway to stimulate osteogenic differentiation, and Mg2+ influx via MagT1 is profoundly involved in this process. Then, Mg‐enriched microspheres are fabricated at the appropriate size to ensure the viability of the encapsulated cells. A series of experiments show that the Mg‐enriched microenvironment not only stimulates the osteogenic differentiation of stem cells but also promotes neovascularization. Obvious vascularized bone regeneration is achieved in vivo using these Mg‐enriched cell delivery vehicles. The findings suggest that biomaterials mimicking the developmental microenvironment might be promising tools to enhance tissue regeneration.
Improving Performance of Hybrid Graphene–Perovskite Photodetector by a Scratch Channel
Authors: Chen Ziyu , Kang Zhe , Rao Chaoping , Cheng Yongfa , Liu Nishuang , Zhang Zhi , Li Luying , Gao Yihua
Published: April 2019

As a remarkable potential material for optoelectronics, perovskite has been widely studied in photodetectors. Here, a channel structure on graphene is introduced to achieve efficient separation of carriers in perovskites by suppressing the leakage current. The fabricated horizontal graphene/perovskite/graphene (GPG) structure detector with a graphene–perovskite hybrid channel and a secondary perovskite channel shows a good performance with a responsivity of 22 mA W−1, on/off switch ratio of 2.6 × 103, and detectivity of 3.55 × 109 Jones at a bias voltage of 2 V and an effective area of 3 × 5 mm2. The channel prepared by a simple probe drawing process forms a horizontal Schottky structure that is effective in generating photocurrent. It is proposed that minimizing the thickness of the perovskite without reducing the absorption rate and maintaining one channel are effective ways to further improve the performance of the GPG detector. The photoresponse characteristics of the devices under illumination of different wavelengths are measured, showing wide spectral response range and linear optical power response. Finally, a flexible GPG detector on polyethylene terephthalate substrate is fabricated. It almost retains the same performance and shows good reliability and bendability.