bluuebunny/crossref_metadata_2025 huggingface dataset:
Study of Physical Properties and Shock Absorption Abilities of Starch Polymer Foam as Cushioning Material for Packaging
Authors: Amir N. , Hisham Mohamed Syakir Mohamed , Abidin Kamal Ariff Zainal
Published: November 2018

Lack of information about the formulation and fabrication process of starch polymer foam and lack of study in the shock absorption ability of starch polymer foam were the reasons this research was executed. In this project starch polymer foam was produced to be used as cushioning material for packaging. Starch polymer foam were developed from starch, polyvinyl alcohol (PVA), urea, citric acid, and deionised water. Water amount with drying and curing process were the variables manipulated to produce the best starch polymer foam. It was determined then, that the optimized ratio of starch:PVA:citric acid was 1:1:4. The amount of water used was 10 ml/gram of starch/PVA weight. The suitable foaming mixing was done at a speed of 1500 rpm for 40 minutes. Drying process was done at 70°C for 24 hours, followed by curing process at 100°C for 1 hour to produce closed-cell foam. While for the open-cell foam, the foam was dried and cured at 100ºC for 6 hours. The open-cell and closed-cell foams produced were cut to 6 cm height x 6 cm width x 0.5 cm thick. The average density was calculated and then the foams were subjected to weight drop destructive test. The test was done by placing a foam on top of a piece of mirror, and a weight is dropped onto the foam, with increasing height until the mirror break. Three weights were used with mass of 50 g, 100 g and 200 g. The starch foams were compared to polyurethane and polystyrene foams in terms of the minimum height that can cause the mirror to break. The results showed that starch closed-cell foam absorbed the highest impact energy followed by polystyrene foam, starch open-cell foam and polyurethane foam.
Finite Element Analysis of Impact Energy on Spur Gear
Authors: Aziz Ismail Ali Bin Abdul , Idris Daing Mohamad Nafiz Bin Daing , Hassan Mohd Hasnun Arif Bin , Basrawi Mohamad Firdaus Bin
Published: November 2018

In high-speed gear drive and power transmission, system impact failure mode always occurs due to the sudden impact and shock loading during the system in running. Therefore, study on the amount of impact energy that can be absorbed by a gear is vital. Impact test equipment has been designed and modelled for the purpose to study the impact energy on gear tooth. This paper mainly focused on Finite Element Analysis (FEA) of impact energy that occurred during simulation involving the impact test equipment modelling. The simulation was conducted using Abaqus software on critical parts of the test equipment to simulate the impact event and generate impact data for analysis. The load cell in the model was assumed to be free fall at a certain height which gives impact load to the test gear. Three different type of material for the test gear were set up in this simulation. Results from the simulation show that each material possesses different impact energy characteristic. Impact energy values increased along with the height of load drop. AISI 1040 were found to be the toughest material at 3.0m drop that could withstand up to 44.87N.m of impact energy. These data will be used to validate data in physical experiments in further study.
Gate Location and Injection Analysis of a Spur Gear
Authors: Ghazali Wafiuddin Md , Idris Daing Mohamad Nafiz Daing , Sofian Azizul Helmi , Siregar Januar Parlaungan , Basrawi Mohamad Firdaus
Published: November 2018

Injection moulding process is one of the common processes to produce plastic parts from simple to complicated parts. This paper focuses on the injection process analysis of a 25 tooth spur gear. Three runner system are proposed for the gear and each system will be analysed using Autodesk Simulation Moldflow Advisor. The most suitable design will then be chosen based on the results obtained from the simulation. The design undergoes cooling quality, sink mark, fill + pack, and warp analysis. Based on these analyses, Design 1 gave the better results compared to Design 2 and 3. From there, Design 1 runner system is chosen for the injection moulding mould which will be fabricated later in the research.
Environmental Assessment on Hybrid Solar Air Conditioning System in Tropical Region
Authors: Noor D.N. , Ibrahim H. , Basrawi F.
Published: November 2018

Vapour compression systems are widely used in large scale of cooling application in industrial, commercial and institutional buildings. This conventional system did contribute to environmental problem; thus to overcome this issue nowadays, exploitation of solar energy for cooling purpose been studied. This paper presents a hybrid solar air conditioning system through appropriate solution for current problem of vapour compression system. However, solar air conditioning have major issue regarding an intermittence input due to unstable of daily solar radiation. Thus, introduction of thermal energy storage (TES) such as chilled water storage (CWS) foreseen to be the best solution and more economical compared to other types of storage. Through appropriate practicality in design and application, variation on solar collector area was analysed to determine optimum sizing which best suit with environmental factor. Surprisingly, the smallest collector area (150 m2) did shown highest saving on greenhouse gasses emission to environment.
The Need of Computer Modelling and Simulation (CMS) Competency among Employers in Malaysia
Authors: Ismadi Mohd Zulhilmi P. , Kurnia Jundika C. , Sulaiman Shaharin A. , Hassan Suhaimi , Awang Mokhtar , Yusoff Puteri S.M.M. , Urquia Alfonso
Published: November 2018

With the continuous improvement in Computer Modelling and Simulation Environment (CMSE) applications being made, computer modelling and simulation (CMS) is proven a better alternative as opposed to conventional physical modelling. The advancement of computing hardware allows accurate results to be obtained faster, safer and at a fraction of its original cost. Despite the proven advantages, CMSE adoption among companies may be fairly new in Malaysia. This study is aimed at quantifying the demand of CMSE specialists in Malaysia as well as gaining insights in the companies’ requirements of specialists’ knowledge, competencies and skills. Thus, a survey, consisted of 3 main parts, was conducted among industries in Malaysia as a tool of measurement of the demand. The survey included questions related to the general information of the organization, specialists’ competencies relation to the job scope, and finally the professional and educational standards among specialists. In general, it was found that practically-competent specialists in CMSE are in high demand among engineering companies. Furthermore, professional courses through distance learning would be of high interest among companies to send their employees to gain practical competency in CMSE.
Visualization Terrain Data Using Cubic Ball Triangular Patches
Authors: Karim Samsul Ariffin Bin Abdul , Saaban Azizan
Published: November 2018

Scattered data technique is important to visualize the geometrical images of the surface data especially for terrain, earthquake, geochemical distribution, rainfall etc. The main objective of this study is to visualize the terrain data by using cubic Ball triangular patches. First step, the terrain data is triangulated by using Delaunay triangulation. Then partial derivative will be estimated at the data points. Sufficient condition for C1 continuity will be derived for each triangle. Finally, a convex combination comprising three rational local scheme is used to construct the surface. The scheme is tested to visualize the terrain data collected at central region of Malaysia.
Sparse recovery from extreme eigenvalues deviation inequalities
Authors: Dallaporta Sandrine , De Castro Yohann
Published: November 2018

This article provides a new toolbox to derive sparse recovery guarantees – that is referred to as “stable and robust sparse regression” (SRSR) – from deviations on extreme singular values or extreme eigenvalues obtained in Random Matrix Theory. This work is based on Restricted Isometry Constants (RICs) which are a pivotal notion in Compressed Sensing and High-Dimensional Statistics as these constants finely assess how a linear operator is conditioned on the set of sparse vectors and hence how it performs in SRSR. While it is an open problem to construct deterministic matrices with apposite RICs, one can prove that such matrices exist using random matrices models. In this paper, we show upper bounds on RICs for Gaussian and Rademacher matrices using state-of-the-art deviation estimates on their extreme eigenvalues. This allows us to derive a lower bound on the probability of getting SRSR. One benefit of this paper is a direct and explicit derivation of upper bounds on RICs and lower bounds on SRSR from deviations on the extreme eigenvalues given by Random Matrix theory.
Unusual indication of Cell therapy for hip osteonecrosis after pregnancy
Authors: Hernigou Philippe , Rigoulot Guillaume , Auregan Jean Charles , Housset Victor , Bastard Claire , Dubory Arnaud , Lachaniette Charles Henri Flouzat
Published: November 2018

Purpose: Osteonecrosis is a rare event during or after pregnancy. Due to the low number of cases, there is no report of long-term results after conservative surgery in this population.

Method: From 1992 to 2010, 145 consecutive female patients with unilateral symptomatic (94 stage I and 51 stage II) left hip osteonecrosis (ON) related to pregnancy were treated between 4 and 16 months after delivery with percutaneous mesenchymal stem cell (MSC) injection obtained from bone marrow concentration. The average total number of MSCs (counted as number of colonies forming units-fibroblast) injected in the hip was 185 000 ± 65 000 cells (range 95 000–240 000 cells).

Results: At the most recent follow-up (average 15 years after hip surgery, range 8–25 years), among the 145 hips included in the study, 4 hips (2.7%) had collapsed and were treated with total hip arthroplasty (THA). Thirty-two of the 94 stage I had progressed to stage II; and 4 of the 51 stage II had progressed to stage III and collapse. The other 141 hips (97.3%) were without collapse and pain free. On MRI, as percentage of the volume of the femoral head, the osteonecrosis had decreased from 34.5% pre-operatively to 6% at the most recent follow-up. For women who had other children after treatment, a subsequent pregnancy was not associated with osteonecrosis.

Conclusion: Patients with hip osteonecrosis following pregnancy had a low conversion rate to THA when treated early with cell therapy.
Effektive Einarbeitung
Authors: Weiß Claudia , Zoller Richard
Published: November 2018

Die Digitalisierung von Informationssystemen macht auch vor Kliniken nicht Halt.
Die Einarbeitung der Pflegefachkräfte in die Funktionsweise und Anwendung eines
Patientendatenmanagementsystems verläuft in aller Regel parallel zum
Stationsalltag. Am Beispiel des Universitätsklinikums Bonn schildern die beiden
Autoren, wie den Mitarbeitern der Einstieg erleichtert und der Umgang mit dem
System effektiv gestaltet werden kann.
Normocalcemic Primary Hyperparathyroidism: A Comparison with the Hypercalcemic Form in a Tertiary Referral Population
Authors: Pierreux Jan , Bravenboer Bert
Published: November 2018

Normocalcemic primary hyperparathyroidism (NPHPT) is a formally recognized variant of primary hyperparathyroidism (PHPT), characterized by normal total and ionized serum calcium concentrations and elevated parathyroid hormone (PTH) levels, in the absence of secondary causes for hyperparathyroidism. NPHPT has been studied previously, but data are limited and confounded. We aimed to compare the clinical and biochemical data of normocalcemic and hypercalcemic subjects in a hospital-based population.

We retrospectively analysed the medical records of 131 subjects diagnosed with PHPT at the university hospital Brussels (UZ Brussel) between January 1st 2007 and December 31st 2016, including 25 normocalcemic and 106 hypercalcemic subjects.

The mean values of age, BMI, sex, serum 25-OH vitamin D levels and urinary phosphate excretion were comparable between both groups. Subjects diagnosed with NPHPT had significantly lower plasma PTH levels, lower urinary calcium excretion and lower serum creatinine levels compared to the hypercalcemic subjects with PHPT. Corresponding eGFR values were higher in the normocalcemic group. Normocalcemic subjects (NPHPT) presented with a high prevalence of nephrolithiasis (36%), fragility fractures (12%) and osteoporosis (25%). Clinical manifestations and BMD measurements revealed no statistically significant differences between both groups.

Our data show a relative prevalence of 19% NPHPT in PHPT. NPHPT may present the earliest form of PHPT with an extension in time, but is not an indolent disease state. Normocalcemic subjects should be managed as hypercalcemic subjects with PHPT. Further research regarding the pathophysiology and natural course of NPHPT is required.
Association Between Plasma Concentration of Klotho Protein, Osteocalcin, Leptin, Adiponectin, and Bone Mineral Density in Patients with Chronic Kidney Disease
Authors: Marchelek-Mysliwiec Małgorzata , Wisniewska Magda , Nowosiad-Magda Monika , Safranow Krzysztof , Kwiatkowska Ewa , Banach Bolesław , Dołegowska Barbara , Dołegowska Katarzyna , Stepniewska Joanna , Domanski Leszek , Pawlik Andrzej , Ciechanowski Kazimierz
Published: November 2018

Patients with early-stage chronic kidney disease (CKD) are susceptible to changes in metabolic processes. Partial loss of kidney function leads to homoeostatic disturbances in bone and fatty tissue. The aim of this study was to investigate the association between plasma concentrations of Klotho protein, FGF23, leptin, adiponectin, osteocalcin, and bone mineral density (BMD) in patients with CKD in the pre-dialysis period. The study involved 52 patients with CKD and 23 patients with no kidney disease. In both groups, BMD, body mass index and serum or plasma concentrations of lipids, glucose, creatinine, calcium, phosphorus, parathormone, leptin, adiponectin, osteocalcin, Klotho, and FGF23 were measured. The group with CKD had statistically significant higher concentrations of leptin (p<0.001), parathormone (p<0.001), and osteocalcin (p<0.001) in comparison with the control group. Patients with CKD also had statistically significant lower BMD in the femoral neck in comparison with the control group. Osteocalcin correlated negatively with BMD. The results of our study suggest that elevated osteocalcin is the most sensitive marker of decreased bone mass in patients with CKD. Osteocalcin correlated negatively with BMD and GFR. The loss of bone mass in CKD patients was greatest in the femoral neck.
The Effects of Melatonin Supplementation on Glycemic Control: A Systematic Review and Meta-Analysis of Randomized Controlled Trials
Authors: Doosti-Irani Amin , Ostadmohammadi Vahidreza , Mirhosseini Naghmeh , Mansournia MohammadAli , Reiter Russel , Kashanian Maryam , Rahimi Maryam , Razavi Maryamalsadat , Asemi Zatollah
Published: November 2018

This systematic review and meta-analysis of randomized controlled trials (RCTs) was conducted to clarify the effect of melatonin supplementation on glycemic control. Databases including PubMed, MEDLINE, EMBASE, Web of Science, and Cochrane Central Register of Controlled Trials were searched until July 30th, 2018. Two reviewers independently assessed study eligibility, extracted data, and evaluated the risk of bias for included trials. Heterogeneity among included studies was assessed using Cochran’s Q test and I-square (I2) statistic. Data were pooled using random-effect models and standardized mean difference (SMD) was considered as the overall effect size. Twelve trials out of 292 selected reports were identified eligible to be included in current meta-analysis. The pooled findings indicated that melatonin supplementation significantly reduced fasting glucose (SMD=–6.34; 95% CI, –12.28, –0.40; p=0.04; I2: 65.0) and increased the quantitative insulin sensitivity check index (QUICKI) (SMD=0.01; 95% CI, 0.00, 0.02; p=0.01; I2: 0.0). However, melatonin administration did not significantly influence insulin levels (SMD=–1.03; 95% CI, –3.82, 1.77; p=0.47; I2: 0.53), homeostasis model assessment of insulin resistance (HOMA-IR) (SMD=–0.34; 95% CI, –1.25, 0.58; p=0.37; I2: 0.37) or HbA1c levels (SMD=–0.22; 95% CI, –0.47, 0.03; p=0.08; I2: 0.0). In summary, the current meta-analysis showed a promising effect of melatonin supplementation on glycemic control through reducing fasting glucose and increasing QUICKI, yet additional prospective studies are recommended, using higher supplementation doses and longer intervention period, to confirm the impact of melatonin on insulin levels, HOMA-IR and HbA1c.
Central Tolerance Mechanisms to TSHR in Graves’ Disease: Contributions to Understand the Genetic Association
Authors: Pujol-Borrell Ricardo , Álvarez-Sierra Daniel , Jaraquemada Dolores , Marín-Sánchez Ana , Colobran Roger
Published: November 2018

In the last 3 years, the association of thyrotropin receptor gene (TSHR) variations to Graves’ disease (GD) has been confirmed. It is now well established that a 30 Kb region of intron 1 of the TSHR gene is linked to GD predisposition. Elucidating the mechanism(s) by which these polymorphisms confer susceptibility is difficult but would constitute an important advance in endocrine autoimmunity in general. Two hypotheses, both postulating TSHR gene regulatory mechanisms, are discussed. One postulates differential level of expression in the thymus, involving central tolerance. The other postulates a shift in TSHR differential splicing leading to the production of soluble proteins that will have easy access to antigen presenting cells, so it is focused in peripheral tolerance. A combination of the 2 hypothesis is feasible, especially under the light of recent evidence that have identified epigenetic factors acting on TSHR intron 1.
Steigerung von Effizienz und Sicherheit: Quo vadis, Digitalisierung?
Authors: Gocke Peter
Published: November 2018

Alle Jahre im November ist MEDICA-Zeit. Und auch auf der diesjährigen MEDICA werden wieder Themen rund um die Digitalisierung des Gesundheitswesens einen breiten Raum einnehmen. Hier werden unverändert hohe Erwartungen geweckt: In diesem Jahr sind es vor allem Themen um die Schlagworte Big Data und künstliche Intelligenz, die wahre Wunder in Bezug auf Effizienzsteigerung und Sicherheit versprechen. Beschäftigt man sich näher mit diesen Lösungen, so stellt man schnell fest, dass die hierfür benötigten Daten in den meisten Einrichtungen nicht wirklich verfügbar sind: Klinische Daten liegen oftmals wenig strukturiert in voneinander separierten Abteilungssystemen, sind nicht selten nur als PDFs verfügbar – und somit für algorithmische Auswertungen nutzlos.
Spracherkennung: Schnell dokumentiert
Authors: Lang Michael
Published: November 2018

Das Projekt MoreCare befindet sich im Feldversuch. Wissenschaftler gehen der Frage nach, wie sich der Therapieerfolg einer mobilen Reha mithilfe von Technologie verbessern lässt. Patienten und Therapeuten erhalten dazu ein Tablet mit modernster Spracherkennungstechnologie.
Compamed 2018: Smarte Technologien der Medizintechnik Zulieferer
Authors: Jopp Klaus
Published: November 2018

Zwei wesentliche Trends prägen den Bereich der Medizintechnik schon seit geraumer Zeit und sorgen für kurze Innovationszyklen: die Dematerialisierung und die Digitalisierung. Produkte werden demnach immer kompakter bei unveränderter oder besserer Leistungsfähigkeit, sie sind immer leichter zu bedienen und Neuerungen sind insgesamt eher software- und weniger hardwaregetrieben.
Medizinische Wearables: Intelligente Pflaster auf dem Vormarsch
Authors: Lang Michael
Published: November 2018

Tragbare Sensoren haben sich im Heimbereich zur Selbstvermessung längst etabliert. In den deutschen Krankenhäusern hingegen sind medizinische Wearables noch rar. Christian Stammel, CEO von Wearable Technologies, erklärt die Hintergründe.
Sepsisdiagnostik: Erfolgreich im Kampf gegen die Blutvergiftung
Authors: Steinke Constanze
Published: November 2018

Das Projekt „Sepsisdialog“ der Universitätsmedizin Greifwald will die Sterblichkeit bei einer Blutvergiftung reduzieren – mit Erfolg! Neben zahlreichen Schulungs- und Aufklärungsmaßnahmen setzt das Netzwerk vor allem auf eine Optimierung der mikrobiologischen Diagnostik und des Sepsis-Notfallmanagements.
Moderne Wundheilung: Chronischen Schwachstellen auf der Spur
Authors: Reisinger Kathrin
Published: November 2018

Bei der Versorgung von Patienten mit großen oder gar chronischen Wunden ist eine Behandlung oft langwierig und teuer. Doch jetzt gibt es Unterstützung aus der digitalen Welt.
Neuroradiologie: Modernste Technik mit neuer Zwei-Ebenen-Angiografieanlage
Authors: Paar Anja
Published: November 2018

Um lebensgefährliche Schlaganfälle und andere Erkrankungen der Blutgefäße – speziell des Kopfes – noch schneller, präziser und schonender behandeln zu können, hat das Helios Klinikum Bad Saarow in eine hochmoderne Zwei-Ebenen-Angiografieanlage investiert.
Livedatenplattform: Betten aufbereiten per Echtzeitanalyse
Authors: Kucera Martin
Published: November 2018

Digitale Innovationen können eine große Arbeitserleichterung für das Pflege- und Servicepersonal sein. Die Livedatenplattform für Prozess- und Ressourcenoptimierung von simplinic ist ein gutes Beispiel dafür, denn sie ermöglicht Steuerung und Lokalisierung in Echtzeit. Im Gespräch mit kma erklärt Steffen Geyer, Gründer und Geschäftsführer des Berliner Unternehmens, wie das funktioniert.
Populationsmodelle: „Wir brauchen mehr Flexibilität vor Ort“
Authors: Mau Jens
Published: November 2018

Populationsmodelle haben in der Gesundheitsbranche Hochkonjunktur. Allerdings nur in Vorträgen, auf Podien und anderen Diskussionsveranstaltungen. Im kma-Interview erklärt der Versorgungsforscher Wolfgang Hoffmann, wie man die Weichen für neue Bezahlmodelle stellen könnte.
Ultrasound-Guided Surgery for Carpal Tunnel Syndrome: A New Interventional Procedure
Authors: Hakime Antoine , Silvera Jonathan , Richette Pascal , Nizard Rémy , Petrover David
Published: November 2018

Carpal tunnel syndrome (CTS) may be treated surgically if medical treatment fails. The classical approach involves release of the flexor retinaculum by endoscopic or open surgery. Meta-analyses have shown that the risk of nerve injury may be higher with endoscopic treatment. The recent contribution of ultrasound to the diagnosis and therapeutic management of CTS opens new perspectives. Ultrasound-guided carpal tunnel release via a minimally invasive approach enables the whole operation to be performed as a percutaneous radiological procedure. The advantages are a smaller incision compared with classical techniques; great safety during the procedure by visualization of anatomic structures, particularly variations in the median nerve; and realization of the procedure under local anesthesia. These advantages lead to a reduction in postsurgical sequelae and more rapid resumption of daily activities and work. Dressings are removed by the third day postsurgery. Recent studies seem to confirm the medical, economic, and aesthetic benefits of this new approach.
Percutaneous Vertebral Augmentation Techniques in Osteoporotic and Traumatic Fractures
Authors: Hamze Bassam , Odri Guillaume , Funck-Brentano Thomas , Orcel Philippe , Laredo Jean-Denis , Bousson Valérie
Published: November 2018

Percutaneous vertebral augmentation/consolidation techniques are varied. These are vertebroplasty, kyphoplasty, and several methods with percutaneous introduction of an implant (associated or not with cement injection). They are proposed in painful osteoporotic vertebral fractures and traumatic fractures. The objectives are to consolidate the fracture and, if possible, to restore the height of the vertebral body to reduce vertebral and regional kyphosis. Stabilization of the fracture leads to a reduction in pain and thus restores the spinal support function as quickly as possible, which is particularly important in the elderly. The effectiveness of these interventions on fracture pain was challenged once by two randomized trials comparing vertebroplasty to a sham intervention. Since then, many other randomized studies in support of vertebroplasty efficacy have been published. International recommendations reserve vertebroplasty for medical treatment failures on pain, but earlier positioning may be debatable if the objective is to limit kyphotic deformity or even reexpand the vertebral body. Recent data suggest that in osteoporotic fracture, the degree of kyphosis reduction achieved by kyphoplasty and percutaneous implant techniques, compared with vertebroplasty, is not sufficient to justify the additional cost and the use of a somewhat longer and traumatic procedure. In young patients with acute traumatic fractures and a significant kyphotic angle, kyphoplasty and percutaneous implant techniques are preferred to vertebroplasty, as in these cases a deformity reduction has a significant positive impact on the clinical outcome.
Plasma centrifuge with axial circulation for calcium isotope separation
Authors: Borisevich V. D. , Potanin E. P. , Whichello J.
Published: November 2018

A method for calcium isotope separation in a plasma centrifuge, with a hot wall and axial circulation, is examined. The rotation of the weakly ionized calcium plasma is provided by a rotating magnetic field. An increase in the radial separation effect in the axial direction is achieved by the incorporation of axial circulation, which is induced by a traveling magnetic field. The product and waste flows are induced by means of cooled discs at both ends of a column. The operation of the plasma centrifuge with a product flow is considered. The dependence of the separation factor on the product flow rate and an axial flow is calculated.
Laser-based setup for simultaneous measurement of the Seebeck coefficient and electrical conductivity for bulk and thin film thermoelectrics
Authors: Melhem Amer , Rogé Vincent , Huynh T. T. Dai , Stolz Arnaud , Talbi Abderazek , Tchiffo-Tameko Cyril , Lecas Thomas , Boulmer-Leborgne Chantal , Millon Eric , Semmar Nadjib
Published: November 2018

In this paper, an original homemade system is presented in detail for the electrical and thermoelectrical characterizations of several types of materials from bulk to thin films. This setup was built using a modulated CO2 laser beam to probe the thermoelectric properties at different depths below the surface. It allows a simultaneous measurement of the electrical conductivity (σ) and the Seebeck coefficient (S), from room temperature up to 250 °C. A commercial sample of Bi2Te3 was first used to validate the Seebeck coefficient measurement. Single crystalline silicon (sc-Si) was used for the uncertainty quantification during the simultaneous measurement of the Seebeck coefficient and the electrical conductivity. At the micrometer scale, thermoelectric characterization of the mesoporous Si (50 μm thickness) was achieved and results gave very promising values (S ≈ 700 μV K−1) for micro-thermo-generator fabrication. In the case of thin film materials, metals (copper and constantan) and oxide thin films (titanium oxide) were also characterized in the in-plane configuration in order to determine the metrology limits of our thermoelectric setup. In this case, a typical sensitivity of about 2μV K−1 was achieved.
Numerical study and optimization of the formation and sustainment of a coaxial helicity injection spheromak
Authors: O'Bryan J. B. , Romero-Talamás C. A. , Woodruff S.
Published: November 2018

Nonlinear, numerical computation with the NIMROD code is used to explore magnetic self-organization during the formation, sustainment, and relaxation of a spheromak with coaxial helicity injection. The formation process is largely insensitive to the local current distribution in the annular current column and details of the injector current trace, instead depending on the peak injected current (specifically λinj/λeig) and the bias flux Ψbias. The injected flux Φinj needed to trigger the column mode instability, the resulting local poloidal flux amplification AΨ, the amount of injected energy retained in the plasma as magnetic energy ηM, and the magnetic helicity per unit of injected energy ηK all scale with λinj/λeig. Both Φinj and ηK scale with the bias flux Ψbias, and ηM and ηK scale inversely with the pre-fill density. Sustained relaxation occurs when the injector current is maintained between two threshold values, 0.8 < λinj/λeig < 1 for the geometry studied. Overall, our results suggest that the performance of the spheromak configuration is very robust and therefore allows for flexibility in the design and operation of a Proof-of-Principle spheromak concept.
Multi-scale study of the deformation mechanisms of thermoelectric p-type half-Heusler Hf0.44Zr0.44Ti0.12CoSb0.8Sn0.2
Authors: Aumand Matthieu , Amiard Guillaume , He Ran , Ren Zhifeng , White Ken W. , Thilly Ludovic
Published: November 2018

Increasing the figure of merit ZT of thermoelectric (TE) alloys is a challenge that is currently attempted through various metallurgy methods, including nanostructuring and dislocation engineering. Microstructures with such a level of complexity raise questions about the mechanical reliability of these new materials. Indeed, despite the values of hardness and elastic modulus known for the clear majority of TE materials, the data on deformation mechanisms are still rare. Focusing on the nanostructured p-type half-Heusler Hf0.44Zr0.44Ti0.12CoSb0.8Sn0.2, our multi-scale study aims to analyze the deformation mechanisms. Experiments conducted at macro-, meso-, and micro-scale are designed to trigger and assess plasticity mechanisms. Compression testing on bulk samples subject to a confining pressure environment and temperature leads to an exclusive brittle failure. The mixed-mode failure mechanisms involve switching between intra- and inter-granular crack propagation, depending on the grain size met by the crack tip. Cube-corner nanoindentation at meso-scale generates cracks and enables fracture toughness estimation, while TEM analysis of the crack tip area confirms no dislocation activity and 3D-Electron Back Scattered Diffraction technique confirms the mixed crack propagation behavior. At micro-scale, micro-pillar compression stress-strain curves and failure mechanisms are comparable with bulk samples testing analysis. These results can be used to provide design guidelines for more crack-resistant TE alloys.
Phase field modeling of grain boundary migration and preferential grain growth driven by electric current stressing
Authors: Liang S. B. , Ke C. B. , Wei C. , Zhou M. B. , Zhang X. P.
Published: November 2018

A phase field model incorporating the electrostatic free energy and the grain orientation effect is developed and employed to study the grain boundary migration and preferential grain growth in widely used beta-tin (β-Sn) under electric current stressing. The directional migration of grain boundaries and the preferential growth of the grain with its orientation having low electrical resistivity along the electric current direction are theoretically clarified. In a bicrystal system containing a circular grain, the shrinkage velocity and morphology changes of grains are dominated by the competition effect between the grain boundary energy and the electrostatic free energy; in particular, the high-density electric current can induce the instability of grain morphology evolution. Moreover, grain morphology evolution leads to the change of the voltage across the β-Sn system; it is found that the voltage decreases over time in a tricrystal system, while the variation of the voltage across the bicrystal system is related to the above-mentioned competition effect. The proposed model and results provide insights into the orientation-related microstructure evolution under electric current stressing.
High thermoelectric power factor of ytterbium silicon-germanium
Authors: Tanusilp Sora-at , Nishide Akinori , Ohishi Yuji , Muta Hiroaki , Hayakawa Jun , Kurosaki Ken
Published: November 2018

Metal silicide-based thermoelectric (TE) materials have attracted attention owing to low toxicity and high chemical stability. Here, we demonstrate that ytterbium silicon-germanium, Yb(Si1−xGex)2−δ, shows a large Seebeck coefficient (S) accompanied by metal-like high electrical conductivity (σ) attributed to the intermediate valence behavior of Yb (Yb2+/Yb3+). We revealed that x = 0.5, i.e., YbSiGe, is the best composition with the highest power factor (S2σ) of 3.6 mW m−1 K−2 at room temperature, which is comparable to those of conventional TE materials, such as Bi2Te3.
Double carrier transport in electron-doped region in black phosphorus FET
Authors: Hirose Kohei , Osada Toshihito , Uchida Kazuhito , Taen Toshihiro , Watanabe Kenji , Taniguchi Takashi , Akahama Yuichi
Published: November 2018

Double carrier transport has been observed in thin film black phosphorus (BP) field effect transistor devices in the highly electron-doped region. BP thin films with a typical thickness of 15 nm were encapsulated by hexagonal boron nitride thin films to avoid degradation by air exposure. Their Hall mobility reached 5300 cm2/V s and 5400 cm2/V s at 4.2 K in the hole- and electron-doped regions, respectively. The gate voltage dependence of conductivity exhibits an anomalous shoulder structure in the electron-doped region. In addition, at gate voltages above the shoulder, the magnetoresistance changes to positive, and there appears an additional slow Shubnikov-de Haas oscillation. These results strongly suggest the appearance of second carriers, which originate from the second subband with a localized band edge.
Ratchet-induced variations in bulk states of an active ideal gas
Authors: Rodenburg Jeroen , Paliwal Siddharth , de Jager Marjolein , Bolhuis Peter G. , Dijkstra Marjolein , van Roij René
Published: November 2018

We study the distribution of active, noninteracting particles over two bulk states separated by a ratchet potential. By solving the steady-state Smoluchowski equations in a flux-free setting, we show that the ratchet potential affects the distribution of particles over the bulks and thus exerts an influence of infinitely long range. As we show, an external potential that is nonlinear is crucial for having such a long-range influence. We characterize how the difference in bulk densities depends on activity and on the ratchet potential, and we identify power law dependencies on system parameters in several limiting cases. While weakly active systems are often understood in terms of an effective temperature, we present an analytical solution that explicitly shows that this is not possible in the current setting. Instead, we rationalize our results by a simple transition state model that presumes particles to cross the potential barrier by Arrhenius rates modified for activity. While this model does not quantitatively describe the difference in bulk densities for feasible parameter values, it does reproduce—in its regime of applicability—the complete power law behavior correctly.
Structural and electronic properties of III-nitride nanoribbons
Authors: Li Xiaobao , Wu Xiang , Zhou Huanlin , Mi Changwen
Published: November 2018

The structural and electronic properties of group III-nitride nanoribbons have been systematically investigated using density functional theory calculations. We computed the edge stresses and edge moduli for III-nitride nanoribbons with a variety of widths and edge terminations, including bare, fully as well as partially hydrogen-passivated edges. In addition, fluorine-passivated zigzag-terminated nanoribbons were also investigated. Our results show that all edges of III-nitride nanoribbons are subjected to compressive stresses. The magnitude of edge stresses strongly depends on the edge terminations. Compressive stress states of nanoribbon edges result in drastically different edge distortions and edge elastic moduli, depending again on the edge configurations. Finally, the electronic band structures are calculated for all zigzag-terminated nanoribbons. We found only fully-passivated nanoribbons are semiconductors with indirect bandgaps. These results suggest that edge terminations significantly affect the edge elastic properties as well as the electronic properties of group III-nitride nanoribbons and their applications.
Efficiency control of high-order harmonic generation in gases using driving pulse spectral features
Authors: Nefedova V. E. , Ciappina M. F. , Finke O. , Albrecht M. , Kozlová M. , Nejdl J.
Published: November 2018

The low conversion efficiency of high-order harmonic generation (HHG) in gases is an insurmountable limitation for many applications, where a considerable photon flux is an instrumental prerequisite. We present a study of the HHG conversion efficiency dependence on the driving laser intensity and analyze the conditions for optimal phase-matching in a loose focusing configuration and long generation medium using a Ti:Sapphire laser. Moreover, by determination of the influence of plasma effects on the driving laser pulse, we observe a correlation between the HHG conversion efficiency and the blueshift of the fundamental pulse. The maximal HHG conversion efficiency is achieved just before the driving laser spectrum is considerably affected by the plasma. Similar behavior is observed in HHG for different noble gases. In this respect, the appearance of a plasma-induced spectral shift in the driving laser might serve as an indication of a substantial loss of HHG conversion efficiency. Consequently, our findings can be exploited to obtain essential information about the laser-plasma interaction process during HHG and can pave the way for a more convenient control of optimal HHG conditions.
Dynamics of polar polarizable rotors acted upon by unipolar electromagnetic pulses: From the sudden to the adiabatic regime
Authors: Mirahmadi Marjan , Schmidt Burkhard , Karra Mallikarjun , Friedrich Bretislav
Published: November 2018

We study, analytically as well as numerically, the dynamics that arises from the interaction of a polar polarizable rigid rotor with single unipolar electromagnetic pulses of varying length, Δτ, with respect to the rotational period of the rotor, τr. In the sudden, non-adiabatic limit, Δτ ≪ τr, we derive analytic expressions for the rotor’s wavefunctions, kinetic energies, and field-free evolution of orientation and alignment. We verify the analytic results by solving the corresponding time-dependent Schrödinger equation numerically and extend the temporal range of the interactions considered all the way to the adiabatic limit, Δτ > τr, where general analytic solutions beyond the field-free case are no longer available. The effects of the orienting and aligning interactions as well as of their combination on the post-pulse populations of the rotational states are visualized as functions of the orienting and aligning kick strengths in terms of population quilts. Quantum carpets that encapsulate the evolution of the rotational wavepackets provide the space-time portraits of the resulting dynamics. The population quilts and quantum carpets reveal that purely orienting, purely aligning, or even-break combined interactions each exhibit sui generis dynamics. In the intermediate temporal regime, we find that the wavepackets as functions of the orienting and aligning kick strengths show resonances that correspond to diminished kinetic energies at particular values of the pulse duration.
An atmospheric pressure plasma jet operated by injecting natural air
Authors: Ghimire Bhagirath , Lamichhane Pradeep , Lim Jun Sup , Min Booki , Paneru Ramhari , Weltmann Klaus-Dieter , Choi Eun Ha
Published: November 2018

This work proposes an atmospheric pressure plasma jet operated by the injection of natural air. The conventional plasma jet has been modified by creating a small hole in the quartz tube. The small amount of argon gas flow inside the tube creates a pressure difference with the surrounding environment. By Bernoulli's principle, natural air is forced to penetrate inside the tube to equalize this difference. The operational range of this device exists for only low argon gas flow rates of 200–600 sccm at a specified value of applied voltage. Compared to the conventional plasma jet without a hole, the concentration of reactive nitrogen species is significantly increased due to the mixing of the surrounding air. In addition, the gas temperature of the device remains close to room temperature, suggesting its strong possibility for biomedical applications. This approach can be an initiation towards the commercialization of plasma jets by using natural air.
Multi-resonance interaction in rectangular waveguide grating structure
Authors: Zhao Ding
Published: November 2018

For developing millimeter and sub-millimeter wave devices, the rectangular waveguide grating sheet beam system is a very promising way to realize a high power operation. To further improve the interaction efficiency, we can substitute the cyclotron beam for the rectilinear one and utilize the multi-resonance effect. In rectangular coordinates, we rigorously derive the formulae to describe the Lorentz forces acting on the electrons and the coupling coefficients of each concerned resonance. The theoretical calculation demonstrates that the combined gain is evidently enhanced when the multi-resonance condition is satisfied, the occurrence of which is always caused by the coupling of two major resonances. The results also show that the multi-resonance effect will rapidly disappear if the beam voltage and the magnetic field deviate from their exact values. Although the parameters should be carefully sustained, the multi-resonance can be excited by using the fundamental TEx10 hybrid mode, which is beneficial for the stable operation. So, as an available mechanism to upgrade the future device performance, it is worth being particularly studied.
Nanoplasmonic sensing of CH3NH3PbI3 perovskite formation in mimic of solar cell photoelectrodes
Authors: Rajab Fahd
Published: November 2018

Hybrid metal-halide perovskites have emerged as leading class of semiconductors for photovoltaic devices with remarkable light harvesting efficiencies. The formation of methylammonium lead iodide (CH3NH3PbI3) perovskite into mesoporous titania (TiO2) scaffold by a sequential deposition technique is known to offer better control over the perovskite morphology. The growth reactions at the mesoporous TiO2 film depend on reactants concentration in the host matrix and the reaction activation energy. Here, we are characterizing formation of CH3NH3PbI3 perovskite in mimic solar cell photoelectrodes utilizing the developed NanoPlasmonic Sensing (NPS) approach. Based on dielectric changes at the TiO2 mesoporous film interface, the technique provides time-resolved spectral shifts of the localized surface plasmon resonance that varies widely depending on the different operating temperatures and methylammonium iodide (CH3NH3I) concentrations. Analytical studies included Ellipsometry, Scanning Electron Microscopy, and X-ray diffraction. The results show that perovskite conversion can be obtained at lower CH3NH3I concentrations if reaction activation energy is lowered. A significant finding is that the NPS response at 350 nm mesoporous TiO2 can widely change from red shifts to blue shifts depending on extent of conversion and morphology of perovskite formed at given reaction conditions.
Effect of carbohydrates on lipid metabolism during porcine oocyte IVM
Authors: Lowe Jenna L. , Bathgate Roslyn , Grupen Christopher G.
Published: November 2018

Porcine oocytes contain a large amount of endogenous lipid, which is thought to function as an intracellular source of energy. The aim of this study was to determine the effects of stimulating or inhibiting lipid metabolism using l-carnitine or etomoxir respectively on the IVM of porcine oocytes cultured in media of varying carbohydrate composition. In the presence of pyruvate and lactate, exclusion of glucose inhibited oocyte nuclear and cytoplasmic maturation compared with oocytes matured in media containing low (1.5mM) and high (4.0mM) concentrations of glucose. In the absence of pyruvate and lactate in low-glucose medium only, a greater proportion of l-carnitine-treated oocytes progressed to the MII stage compared with untreated oocytes. The inclusion of pyruvate and lactate significantly altered the distribution of cytoplasmic lipid droplets and elevated the ATP content of oocytes, whereas the l-carnitine treatment did not. Further, the inhibitory effect of etomoxir on nuclear maturation was decreased in high- compared with low-glucose medium. The results indicate that carbohydrate substrates are absolutely necessary for effective porcine oocyte maturation, and that l-carnitine supplementation can only partially compensate for deficiencies in carbohydrate provision.
Learning from failures of protocol in cross-cultural research
Authors: Hruschka Daniel J. , Munira Shirajum , Jesmin Khaleda , Hackman Joseph , Tiokhin Leonid
Published: November 2018

The many tools that social and behavioral scientists use to gather data from their fellow humans have, in most cases, been honed on a rarefied subset of humanity: highly educated participants with unique capacities, experiences, motivations, and social expectations. Through this honing process, researchers have developed protocols that extract information from these participants with great efficiency. However, as researchers reach out to broader populations, it is unclear whether these highly refined protocols are robust to cultural differences in skills, motivations, and expected modes of social interaction. In this paper, we illustrate the kinds of mismatches that can arise when using these highly refined protocols with nontypical populations by describing our experience translating an apparently simple social discounting protocol to work in rural Bangladesh. Multiple rounds of piloting and revision revealed a number of tacit assumptions about how participants should perceive, understand, and respond to key elements of the protocol. These included facility with numbers, letters, abstract number lines, and 2D geometric shapes, and the treatment of decisions as a series of isolated events. Through on-the-ground observation and a collaborative refinement process, we developed a protocol that worked both in Bangladesh and among US college students. More systematic study of the process of adapting common protocols to new contexts will provide valuable information about the range of skills, motivations, and modes of interaction that participants bring to studies as we develop a more diverse and inclusive social and behavioral science.