bluuebunny/crossref_metadata_2025_split huggingface dataset:
Compressive Evaluation of Polyethylene (Glycol) Diacrylate (PEGDA) for Scaffold Fabrication
Authors: Yasar Ozlem , Inceoglu Serkan 
Published: September 2016

In the field of tissue engineering, scaffold is the foundation structure that provides the desired mechanical support for the tissue being engineered, surface for cells to attach and spread, and access for nutrient transport crucial for cell viability. The scaffolds are 3D building blocks which are designed and fabricated precisely prior to its implantation to the host tissue. When scaffolds with desired shape and size are fabricated, they can be seeded with cells and appropriate growth factors. After cells show healthy growth within the scaffold, they are implanted into the body with the scaffold to allow full-scale tissue regeneration.
In this research, photolithography is adapted as a fabrication method to generate PEGDA-based structures. In this method, ultra-violet (UV) light is reflected on PEGDA and as a result of the interaction between UV light and precursor solution, PEGDA turns into solid form.
Despite the potential of PEGDA in scaffold applications, the mechanical properties have not been studied in a great extent. Therefore, in this project, the mechanical characterization of PEGDA was conducted for various polymer concentrations. Specimens with 20%, 40%, 60%, 80% and 100% PEGDA to water ratio were prepared for compression tests. Our preliminary experimental data results show that, mechanical properties of PEGDA can be controlled by changing the PEGDA to water ratio. Stronger and stiffer structures can be obtained with high PEGDA concentrations while softer structures can be fabricated with reduced PEGDA concentrations.
Selective Laser Melting of Graphene Reinforced Inconel 718 Superalloy: Evaluation of Microstructure and Tensile Performance
Authors: Wang Yachao , Shi Jing , Lu Shiqiang , Wang Yun 
Published: September 2016

Graphene nanoplatelets (GNPs) have many outstanding properties, such as high mechanical strengths, light weight, and high electric conductivity. These unique properties make it an ideal reinforcement used for metal matrix composite (MMCs). In the past few years, many studies have been performed to incorporate GNPs into metal matrix and investigate the properties of obtained metal matrix composites. Meanwhile, fabrication of MMCs through laser assisted additive manufacturing (LAAM) has attracted much attention in recent years due to the advantages of low waste, high precision, short production lead time, and high workpiece complexity capability. In this study, the two attractive features are combined to produce GNPs reinforced MMC using selective laser melting (SLM) process, one of the LAAM processes.
The target metal matrix material is Inconel 718, a nickel-based Ni-Cr-Fe austenitic superalloy that possesses excellent workability and mechanical performance and has wide applications in industries. Inconel 718 holds outstanding mechanical performance, corrosion, oxidation, and wear performance over a wide range of temperatures, making it an attractive superalloy used for high temperature service components. In the experiment, pure Inconel 718 and GNPs reinforced Inconel 718 composites with two levels of GNPs content (i.e., 0.25 and 1 wt.%) are obtained by SLM. Note that the SLM process, a novel powder mixture procedure is adopted to ensure the even dispersion of GNPs in the Inconel 718 powders. Room temperature tensile tests are conducted to evaluate the tensile properties. Scanning electron microscopy (SEM) observations are conducted to analyze the fracture surface of materials and to understand the reinforcing mechanism. It is found that fabrication of GNPs reinforced MMC using SLM is a viable approach. The obtained composite possesses dense microstructure and significantly enhanced tensile strength. The ultimate tensile strengths (UTS) are 997.8, 1296.3 and 1511.6 MPa, and the Young’s moduli are 475, 536, and 675 GPa, for 0 wt.% (pure Inconel 718), 0.25 wt.%, and 1 wt.% GNP additions, respectively. The bonding between GNPs and matrix material appears to be strong, and GNPs are well retained during the SLM process. The strengthening effect and mechanisms involved in the composites are discussed. Load transfer, thermal expansion coefficient mismatch, and dislocation hindering are believed to be the three main reinforcing mechanisms involved.
It should be noted that more work needs to be conducted in the future to obtain more comprehensive information regarding other static and dynamic properties, and the high temperature performances of the GNP reinforced MMCs produced by SLM. Process parameter optimization should also be investigated.
Influence of Preheating Temperature on Mechanical Properties of Laser Cladding Layer
Authors: Jiang Jibin , Lian Guofu , Xu Mingsan , Li Chunyu , Chen Bingsan , Li Bingbing 
Published: September 2016

Physical and chemical changes always occur in the process of laser cladding, and the cladding quality is directly affected by processing parameters. This paper mainly focused on effects of temperature field of preheating substrate on the cladding quality. Laser cladding process has the following experimental parameters: laser power, powder feeding rate and rotational speed. Three types of cladding powders were used: Ni60A, Cr12MoV and WC-Co. Experiments were conducted by using different substrate preheating temperatures and cladding materials, which affect the quality of cladding layers. Comparison and analysis of the three types of powders showed that under different preheating temperatures, the cladding layer is mainly affected by tensile stress. Besides that, the residual stress of cladding layer is always higher than that of heat affected zone and substrates.
The best preheating temperature to test the residual stress for three types of powders are: 600°C, 400°C and 300°C. For all three types of powders under different preheating temperatures, cladding layer and substrate have compact and uniform structures. However, when substrate is overheated the cracking will occur in the substrate. Under different preheating temperatures, the Vickers hardness is higher than that of heat affected zone and the substrate for all three materials. The preheating temperatures for getting the maximum hardness are respectively 300°C, 600°C and 400°C.
Gaps Analysis of Integrating Product Design, Manufacturing, and Quality Data in the Supply Chain Using Model-Based Defintion
Authors: Trainer Asa , Hedberg Thomas , Barnard Feeney Allison , Fischer Kevin , Rosche Phil 
Published: September 2016

Advances in information technology triggered a digital revolution that holds promise of reduced costs, improved productivity, and higher quality. To ride this wave of innovation, manufacturing enterprises are changing how product definitions are communicated — from paper to models. To achieve industry’s vision of the Model-Based Enterprise (MBE), the MBE strategy must include model-based data interoperability from design to manufacturing and quality in the supply chain. The Model-Based Definition (MBD) is created by the original equipment manufacturer (OEM) using Computer-Aided Design (CAD) tools. This information is then shared with the supplier so that they can manufacture and inspect the physical parts. Today, suppliers predominantly use Computer-Aided Manufacturing (CAM) and Coordinate Measuring Machine (CMM) models for these tasks. Traditionally, the OEM has provided design data to the supplier in the form of two-dimensional (2D) drawings, but may also include a three-dimensional (3D)-shape-geometry model, often in a standards-based format such as ISO 10303-203:2011 (STEP AP203). The supplier then creates the respective CAM and CMM models and machine programs to produce and inspect the parts. In the MBE vision for model-based data exchange, the CAD model must include product-and-manufacturing information (PMI) in addition to the shape geometry. Today’s CAD tools can generate models with embedded PMI. And, with the emergence of STEP AP242, a standards-based model with embedded PMI can now be shared downstream.
The on-going research detailed in this paper seeks to investigate three concepts. First, that the ability to utilize a STEP AP242 model with embedded PMI for CAD-to-CAM and CAD-to-CMM data exchange is possible and valuable to the overall goal of a more efficient process. Second, the research identifies gaps in tools, standards, and processes that inhibit industry’s ability to cost-effectively achieve model-based-data interoperability in the pursuit of the MBE vision. Finally, it also seeks to explore the interaction between CAD and CMM processes and determine if the concept of feedback from CAM and CMM back to CAD is feasible. The main goal of our study is to test the hypothesis that model-based-data interoperability from CAD-to-CAM and CAD-to-CMM is feasible through standards-based integration. This paper presents several barriers to model-based-data interoperability. Overall, the project team demonstrated the exchange of product definition data between CAD, CAM, and CMM systems using standards-based methods. While gaps in standards coverage were identified, the gaps should not stop industry’s progress toward MBE. The results of our study provide evidence in support of an open-standards method to model-based-data interoperability, which would provide maximum value and impact to industry.
On the Effect of Screw Preload on the Stress Distribution of Mandibles During Segmental Defect Treatment Using an Additively Manufactured Hardware
Authors: Amerinatanzi Amirhesam , Shayesteh Moghaddam Narges , Jahadakbar Ahmadreza , Dean David , Elahinia Mohammad 
Published: September 2016

The most common method for mandibular reconstructive surgery is the use of a Ti-6Al-4V fixation device and a fibular double barrel graft. This highly stiff fixation hardware (E = 112 GPa) often shields the bone graft (E = 20 GPa) from carrying the load, which may result in bone resorption. Highly stiff Ti-6Al-4V fixation hardware is also likely to concentrate stress in the fixation plate or at screw threads, possibly leading to hardware cracking or screw pull-out. As a solution for that, we have proposed and studied the effect of using a low stiffness, porous NiTi fixation device [1–4]. Although the stress in the fixation device is increased, using such low stiffness fixation hardware, is preferable to have an even higher stress on the graft in order to minimize the risk of resorption or hardware failure. We assume that preloading screws allows them to better engage the fixation hardware with the plate and the surrounding bone and causes an increased von Mises stress. The fixation device can be patient-specific and additively manufactured, such that the shape would match the outer surface of the cortical bone.
In this study, we modeled a healthy cadaver mandible via CT-derived 3D surface data. The mandible was virtually resected in the molar region (M1−3). The model simulated the result of reconstructive surgery under the highest chewing loading regime (i.e., 526 N on first right molar tooth [5, 6]) where reconstruction was done with either Ti-6Al-4V fixation hardware or patient specific, stiffness-matched, porous NiTi fixation hardware. The calibration of the material properties for this simulation was done using experimentally obtained data (DSC and compression tests) of Ni-rich NiTi bulk samples. The analyzed term in the finite element analysis was stress distribution in the cortical and cancellous bone. Porous NiTi fixation devices were also produced using Selective Laser Melting (SLM) using the geometry of the aforementioned cadaver mandible.
In this paper we have studied the effect of additional torque or preload on the performance of the fixation plates. The finite element analysis demonstrated that applying a preload to the screws increased the stress on the bone. Under similar levels of applied preload, the porous NiTi fixation device showed an increased level of von Mises stress in the bone, particularly in the graft. Additionally, the analysis indicated the higher level of stress on the bone surrounding the screws for the case of using NiTi, which could contribute to increasing screw stability. The fabricated patient-specific fixation hardware not only matched the shape of cortical bone but also contained the level of porosity that defines the appropriate modulus of elasticity.
Fabrication of Right Triangular Prism Retroreflectors Through Ultraprecise Single Point Inverted Cutting
Authors: Hamilton Benjamin W. , Hussein Sama , Tutunea-Fatan O. Remus , Bordatchev Evgueni V. 
Published: September 2016

Retroreflectors (RR) represent optical elements whose primary functionality is to return to the incident light back to its originating source. While inverted cube-corner (ICC) geometry constitutes de facto standard in automotive lighting applications, other RR designs exist. Among them, right triangular prism (RTP) constitutes a viable alternative and therefore, the main intention of the present study was to demonstrate a fabrication means other than the ineffective conventional pin-bundling technology are possible.
To address this, a new ultraprecise single point inverted cutting (SPIC) technology — envisioned as a virtual combination between diamond turning and five-axis machining — was introduced as a viable manufacturing option for the fabrication of the RTP RR arrays. While simulation results seem to suggest a slight optical superiority of the RTP RR arrays produced through conventional, rather than SPIC approaches, experimental results have demonstrated that fabricating RTP RR prototypes is not only possible, but it can yield better retroreflective efficiencies when compared to state-of-the-art ICC-based automotive retroreflectors.
Evaluation of the dose calculation accuracy for small fields defined by jaw or MLC for AAA and Acuros XB algorithms
Authors: Fogliata Antonella , Lobefalo Francesca , Reggiori Giacomo , Stravato Antonella , Tomatis Stefano , Scorsetti Marta , Cozzi Luca 
Published: September 2016

PurposeSmall field measurements are challenging, due to the physical characteristics coming from the lack of charged particle equilibrium, the partial occlusion of the finite radiation source, and to the detector response. These characteristics can be modeled in the dose calculations in the treatment planning systems. Aim of the present work is to evaluate the MU calculation accuracy for small fields, defined by jaw or MLC, for anisotropic analytical algorithm (AAA) and Acuros XB algorithms, relative to output measurements on the beam central axis.MethodsSingle point output factor measurement was acquired with a PTW microDiamond detector for 6 MV, 6 and 10 MV unflattened beams generated by a Varian TrueBeam STx equipped with high definition‐MLC. Fields defined by jaw or MLC apertures were set; jaw‐defined: 0.6 × 0.6, 0.8 × 0.8, 1 × 1, 2 × 2, 3 × 3, 4 × 4, 5 × 5, and 10 × 10 cm2; MLC‐defined: 0.5 × 0.5 cm2 to the maximum field defined by the jaw, with 0.5 cm stepping, and jaws set to: 2 × 2, 3 × 3, 4 × 4, 5 × 5, and 10 × 10 cm2. MU calculation was obtained with 1 mm grid in a virtual water phantom for the same fields, for AAA and Acuros algorithms implemented in the Varian eclipse treatment planning system (version 13.6). Configuration parameters as the effective spot size (ESS) and the dosimetric leaf gap (DLG) were varied to find the best parameter setting. Differences between calculated and measured doses were analyzed.ResultsAgreement better than 0.5% was found for field sizes equal to or larger than 2 × 2 cm2 for both algorithms. A dose overestimation was present for smaller jaw‐defined fields, with the best agreement, averaged over all the energies, of 1.6% and 4.6% for a 1 × 1 cm2 field calculated by AAA and Acuros, respectively, for a configuration with ESS = 1 mm for both X and Y directions for AAA, and ESS = 1.5 and 0 mm for X and Y directions for Acuros. Conversely, a calculated dose underestimation was found for small MLC‐defined fields, with the best agreement averaged over all the energies, of −3.9% and 0.2% for a 1 × 1 cm2 field calculated by AAA and Acuros, respectively, for a configuration with ESS = 0 mm for both directions and both algorithms.ConclusionsFor optimal setting applied in the algorithm configuration phase, the agreement of Acuros calculations with measurements could achieve the 3% for MLC‐defined fields as small as 0.5 × 0.5 cm2. Similar agreement was found for AAA for fields as small as 1 × 1 cm2.
Association between
embB
Codon 306 Mutations, Phenotypic Resistance Profiles, and Genotypic Characterization in Clinical Mycobacterium tuberculosis Isolates from Hebei, China
Authors: Li Yanan , Wang Yuling , Zhang Zhi , Gao Huixia , Wang Haibin , Cao Jinfeng , Zhang Shumin , Liu Yuzhen , Lu Jianhua , Xu Zungui , Dai Erhei 
Published: September 2016

ABSTRACT

Ethambutol (EMB) is an essential first-line drug for tuberculosis (TB) treatment. Nucleotide substitutions at
embB
codon 306 (
embB
306) have been proposed to be a potential marker for EMB resistance and a predictor of broad drug resistance in clinical
Mycobacterium tuberculosis
isolates. However, discordant findings about the association between
embB
306 mutations and EMB resistance were reported. Hebei Province is located in the Beijing-Tianjin-Hebei integration region in China; however, little information about the genetic diversity of the
embB
locus in this area is available. In this study, we sequenced the region surrounding
embB
306 (codons 207 to 445) in 62 ethambutol-resistant (EMB
r
) isolates, 214 ethambutol-susceptible isolates resistant to other first-line drugs (EMB
s
isolates), and 100 pan-sensitive isolates. Our data indicated that none of the pan-sensitive isolates showed mutations at
embB
306 and 63 drug-resistant isolates harbored
embB
306 substitutions, with these substitutions being found in 56.5% (35/62) of EMB
r
isolates and 13.1% (28/214) of EMB
s
isolates. A significant association between the
embB
306 mutation and resistance to isoniazid, rifampin, EMB, and multiple drugs was observed, and the rate of mutation of
embB
306 increased with increasing numbers of first-line drugs to which the isolates were resistant. The
embB
306 mutation is not the sole causative factor for EMB resistance, and the poor sensitivity limits its utility as a marker for drug-resistant TB. However, it may be a potential marker for broad drug resistance, especially for multidrug resistance. The mycobacterial interspersed repetitive unit–variable-number tandem-repeat profiles may serve as markers for predicting the
embB
306 substitutions that may occur in drug-resistant
M. tuberculosis
isolates under antimicrobial selection pressure.
Topical Decolonization Does Not Eradicate the Skin Microbiota of Community-Dwelling or Hospitalized Adults
Authors: Burnham Carey-Ann D. , Hogan Patrick G. , Wallace Meghan A. , Deych Elena , Shannon William , Warren David K. , Fritz Stephanie A. 
Published: September 2016

ABSTRACT

Topical antimicrobials are often employed for decolonization and infection prevention and may alter the endogenous microbiota of the skin. The objective of this study was to compare the microbial communities and levels of richness and diversity in community-dwelling subjects and intensive care unit (ICU) patients before and after the use of topical decolonization protocols. We enrolled 15 adults at risk for
Staphylococcus aureus
infection. Community subjects (
n
= 8) underwent a 5-day decolonization protocol (twice daily intranasal mupirocin and daily dilute bleach-water baths), and ICU patients (
n
= 7) received daily chlorhexidine baths. Swab samples were collected from 5 anatomic sites immediately before and again after decolonization. A variety of culture media and incubation environments were used to recover bacteria and fungi; isolates were identified using matrix-assisted laser desorption ionization–time of flight mass spectrometry. Overall, 174 unique organisms were recovered. Unique communities of organisms were recovered from the community-dwelling and hospitalized cohorts. In the community-dwelling cohort, microbial richness and diversity did not differ significantly between collections across time points, although the number of body sites colonized with
S. aureus
decreased significantly over time (
P
= 0.004). Within the hospitalized cohort, richness and diversity decreased over time compared to those for the enrollment sampling (from enrollment to final sampling,
P
= 0.01 for both richness and diversity). Topical antimicrobials reduced the burden of
S. aureus
while preserving other components of the skin and nasal microbiota.
Pharmacodynamics of Ceftolozane Combined with Tazobactam against Enterobacteriaceae in a Neutropenic Mouse Thigh Model
Authors: Melchers M. J. , Mavridou E. , van Mil A. C. , Lagarde C. , Mouton J. W. 
Published: September 2016

ABSTRACT

Ceftolozane is a new broad-spectrum cephalosporin and is combined with tazobactam to broaden the activity of ceftolozane against strains producing extended-spectrum beta-lactamases (ESBLs). We determined the pharmacodynamics (PD) of the combination in the neutropenic mouse thigh model to determine the optimal exposure of tazobactam. Treatment of CD-1 neutropenic mice was started 2 h after infection with ceftolozane every 2 h (q2h) alone or in combination with tazobactam at different dosing frequencies for 24 h, and the number of CFU in the thighs was determined before and after treatment. The maximum effect model was fit to the dose-response and the pharmacokinetic/PD index (PDI)-response to determine the PDI values for ceftolozane alone and ceftolozane in combination with tazobactam resulting in a static effect and a 1-log kill. The effect of tazobactam was dependent on the percentage of time that the free drug concentration remained above the concentration threshold (percent

f
T

>C

T

), whereby dosing q2h was more efficacious than dosing every 8 h (q8h), reducing the tazobactam daily dose by a factor 6.9 to 59.0 (
n
= 3 strains) to obtain a static effect. Using
R
2
as an indicator of the best fit of the percent

f
T

>C

T

-response relationships, the concentration threshold best correlating with the response varied from 0.5 to 2 mg/liter, depending on the strain. A similar result was obtained when the q2h and q8h regimens were analyzed. For all isolates tested, the mean

f
T

>C

T

for 0.5 mg/liter tazobactam was 28.2% (range, 17.5 to 45.8%) and 44.4% (range, 26.6 to 54.7%) for a static effect and a 1-log kill, respectively, at ceftolozane exposures that produced a ceftolozane concentration of 4 mg/liter (a concentration greater than the MIC) for 33.9 to 63.3% of a 24-h period under steady-state pharmacokinetic conditions. The main PDI that correlated with the effect of tazobactam was the

f
T

>C

T

achieved with a

C
T

of 0.5 mg/liter tazobactam.