Genomic analysis of human brain metastases treated with stereotactic radiosurgery reveals unique signature based on treatment failure

Stereotactic radiosurgery (SRS) has been shown to be efficacious for the treatment of limited brain metastasis (BM); however, the effects of SRS on human brain metastases have yet to be studied. We performed genomic analysis on resected brain metastases from patients whose resected lesion was previously treated with SRS. Our analyses demonstrated for the first time that patients possess a distinct genomic signature based on type of treatment failure including local failure, leptomeningeal spread, and radio-necrosis. Examination of the center and peripheral edge of the tumors treated with SRS indicated differential DNA damage distribution and an enrichment for tumor suppressor mutations and DNA damage repair pathways along the peripheral edge. Furthermore, the two clinical modalities used to deliver SRS, LINAC and GK, demonstrated differential effects on the tumor landscape even between controlled primary sites. Our study provides, in human, biological evidence of differential effects of SRS across BM's.

Strong protective effect of the APOL1 p.N264K variant against G2-associated focal segmental glomerulosclerosis and kidney disease

African Americans have a significantly higher risk of developing chronic kidney disease, especially focal segmental glomerulosclerosis -, than European Americans. Two coding variants (G1 and G2) in the APOL1 gene play a major role in this disparity. While 13% of African Americans carry the high-risk recessive genotypes, only a fraction of these individuals develops FSGS or kidney failure, indicating the involvement of additional disease modifiers. Here, we show that the presence of the APOL1 p.N264K missense variant, when co-inherited with the G2 APOL1 risk allele, substantially reduces the penetrance of the G1G2 and G2G2 high-risk genotypes by rendering these genotypes low-risk. These results align with prior functional evidence showing that the p.N264K variant reduces the toxicity of the APOL1 high-risk alleles. These findings have important implications for our understanding of the mechanisms of APOL1-associated nephropathy, as well as for the clinical management of individuals with high-risk genotypes that include the G2 allele.

Strong protective effect of the APOL1 p.N264K variant against G2-associated focal segmental glomerulosclerosis and kidney disease

Black Americans have a significantly higher risk of developing chronic kidney disease (CKD), especially focal segmental glomerulosclerosis (FSGS), than European Americans. Two coding variants (G1 and G2) in the APOL1 gene play a major role in this disparity. While 13% of Black Americans carry the high-risk recessive genotypes, only a fraction of these individuals develops FSGS or kidney failure, indicating the involvement of additional disease modifiers. Here, we show that the presence of the APOL1 p.N264K missense variant, when co-inherited with the G2 APOL1 risk allele, substantially reduces the penetrance of the G1G2 and G2G2 high-risk genotypes by rendering these genotypes low-risk. These results align with prior functional evidence showing that the p.N264K variant reduces the toxicity of the APOL1 high-risk alleles. These findings have important implications for our understanding of the mechanisms of APOL1 -associated nephropathy, as well as for the clinical management of individuals with high-risk genotypes that include the G2 allele.

Inaxaplin for the treatment of APOL1-associated kidney disease

Chronic kidney disease (CKD) is highly prevalent World-Wide and it is an important cause of morbidity and mortality. In 2010, variants in apolipoprotein type 1 (APOL1) gene was identified as a major risk factor for higher prevalence of CKD in individuals of African ancestry. The mechanisms by which toxic gain of function APOL1 variants cause disease are the subjects of current investigations, and there is currently no effective targeted therapy for APOL1 associated kidney disease. Egbuna and others recently reported that an orally administered small molecule compound inaxaplin (VX-147) that binds APOL1 may be useful in the treatment of APOL1 associated kidney disease. This is a groundbreaking study, if confirmed in randomized control studies it may turn out to be one of the major advances in the therapy of proteinuric CKD this decade, and may also represent precision therapy for addressing health disparity in CKD. However, there is a need for a larger randomized control studies with stable eGFR and complete remission of proteinuria as end point, such studies should also be carried out in a more geographically diverse population.

Genomic Analysis of Human Brain Metastases Treated with Stereotactic Radiosurgery Under the Phase-II Clinical Trial (NCT03398694) Reveals DNA Damage Repair at the Peripheral Tumor Edge

Stereotactic Radiosurgery (SRS) is one of the leading treatment modalities for oligo brain metastasis (BM), however no comprehensive genomic data assessing the effect of radiation on BM in humans exist. Leveraging a unique opportunity, as part of the clinical trial (NCT03398694), we collected post-SRS, delivered via Gamma-knife or LINAC, tumor samples from core and peripheral-edges of the resected tumor to characterize the genomic effects of overall SRS as well as the SRS delivery modality. Using these rare patient samples, we show that SRS results in significant genomic changes at DNA and RNA levels throughout the tumor. Mutations and expression profiles of peripheral tumor samples indicated interaction with surrounding brain tissue as well as elevated DNA damage repair. Central samples show GSEA enrichment for cellular apoptosis while peripheral samples carried an increase in tumor suppressor mutations. There are significant differences in the transcriptomic profile at the periphery between Gamma-knife vs LINAC.

The root meristem is shaped by brassinosteroid control of cell geometry

Growth extent and direction determine cell and whole-organ architecture. How they are spatio-temporally modulated to control size and shape is not well known. Here we tackled this question by studying the effect of brassinosteroid (BR) signalling on the structure of the root meristem. Quantification of the three-dimensional geometry of thousands of individual meristematic cells across different tissue types showed that the modulation of BR signalling yields distinct changes in growth rate and anisotropy, which affects the time that cells spend in the meristem and has a strong impact on the final root form. By contrast, the hormone effect on cell volume was minor, establishing cell volume as invariant to the effect of BR. Thus, BR has the highest effect on cell shape and growth anisotropy, regulating the overall longitudinal and radial growth of the meristem, while maintaining a coherent distribution of cell sizes. Moving from single-cell quantification to the whole organ, we developed a computational model of radial growth. The simulation demonstrates how differential BR-regulated growth between the inner and outer tissues shapes the meristem and thus explains the non-intuitive outcomes of tissue-specific perturbation of BR signalling. The combined experimental data and simulation suggest that the inner and outer tissues have distinct but coordinated roles in growth regulation.

Measurement Uncertainty of Surface Temperature Distributions for Laser Powder Bed Fusion Processes

This paper describes advances in measuring the characteristic spatial distribution of surface temperature and emissivity during laser-metal interaction under conditions relevant for laser powder bed fusion (LPBF) additive manufacturing processes. Detailed descriptions of the measurement process, results, and approaches to determining uncertainties are provided. Measurement uncertainties have complex dependencies on multiple process parameters, so the methodology is demonstrated on one set of process parameters and one material. Well-established literature values for high-purity nickel solidification temperature and emissivity at the solidification temperature were used to evaluate the predicted uncertainty of the measurements. The standard temperature measurement uncertainty is found to be approximately 0.9% of the absolute temperature (16 AC), and the standard relative emissivity measurement uncertainty is found to be approximately 8% at the solidification point of high-purity nickel, both of which are satisfactory. This paper also outlines several potential sources of test uncertainties, which may require additional experimental evaluation. The largest of these are the metal vapor and ejecta that are produced as process by-products, which can potentially affect the imaging quality, reflectometry results, and thermal signature of the process, while also affecting the process of laser power delivery. Furthermore, the current paper focuses strictly on the uncertainties of the emissivity and temperature measurement approach and therefore does not detail a variety of uncertainties associated with experimental controls that must be evaluated for future generation of reference data.

Transient Laser Energy Absorption, Co-axial Melt Pool Monitoring, and Relationship to Melt Pool Morphology

Melt pool monitoring (MPM) is a technique used in laser powder bed fusion (LPBF) to extract features from insitu sensor signals that correlate to defect formation or general part fabrication quality. Various melt pool phenomena have been shown to relate to measured transient absorption of the laser energy, which in turn, can be relatable to the melt pool emission measured in MPM systems. This paper describes use of a reflectometer-based instrument to measure the dynamic laser energy absorption during single-line laser scans. Scans are conducted on bare metal and single powder layer of nickel alloy 625 (IN625) at a range of laser powers. In addition, a photodetector aligned co-axially with the laser, often found in commercial LPBF monitoring systems, synchronously measured of the incandescent emission from the melt pool with the dynamic laser absorption. Relationships between the dynamic laser absorption, co-axial MPM, and surface features on the tracks are observed, providing illustration of the melt pool dynamics that formed these features. Time-integrated measurements of laser absorption are shown to correlate well with MPM signal, as well as indicate the transition between conduction and keyhole mode. This transition is corroborated by metallographic cross-section measurement, as well as topographic measurements of the solidified tracks. Ultimately, this paper exemplifies the utility of dynamic laser absorption measurements to inform both the physical nature of the melt pool dynamics, as well as interpretation of process monitoring signals.

Common risk variants in NPHS1 and TNFSF15 are associated with childhood steroid-sensitive nephrotic syndrome

To understand the genetics of steroid-sensitive nephrotic syndrome (SSNS), we conducted a genome-wide association study in 987 childhood SSNS patients and 3,206 healthy controls with Japanese ancestry. Beyond known associations in the HLA-DR/DQ region, common variants in NPHS1-KIRREL2 (rs56117924, P=4.94E-20, odds ratio (OR) =1.90) and TNFSF15 (rs6478109, P=2.54E-8, OR=0.72) regions achieved genome-wide significance and were replicated in Korean, South Asian and African populations. Trans-ethnic meta-analyses including Japanese, Korean, South Asian, African, European, Hispanic and Maghrebian populations confirmed the significant associations of variants in NPHS1-KIRREL2 (P_meta=6.71E-28, OR=1.88) and TNFSF15 (P_meta=5.40E-11, OR=1.33) loci. Analysis of the NPHS1 risk alleles with glomerular NPHS1 mRNA expression from the same person revealed allele specific expression with significantly lower expression of the transcript derived from the risk haplotype (Wilcox test p=9.3E-4). Because rare pathogenic variants in NPHS1 cause congenital nephrotic syndrome of the Finnish type (CNSF), the present study provides further evidence that variation along the allele frequency spectrum in the same gene can cause or contribute to both a rare monogenic disease (CNSF) and a more complex, polygenic disease (SSNS).

In Situ Thermography of the Metal Bridge Structures Fabricated for the 2018 Additive Manufacturing Benchmark Test Series (AM-Bench 2018)

This document provides details on the files available for download in the data set “In situ thermography of the metal bridge structures fabricated for the 2018 Additive Manufacturing Benchmark Test Series (AM-Bench 2018).” The experiments were performed to support the 2018 AM-Bench1 Class 01 experiments consisting of metal three-dimensional (3D) builds. The modeling community was invited to predict the following: (1) part deflection, (2) residual elastic strains, (3) microstructure, (4) phase fractions, and (5) phase evolution. Details for these proposed challenges and the postprocess measurement results can be found at their respective links on the AM-Bench website.

Measurements of melt pool geometry and cooling rates of individual laser traces on IN625 bare plates

The complex physical nature of the laser powder bed fusion (LPBF) process warrants use of multiphysics computational simulations to predict or design optimal operating parameters or resultant part qualities such as microstructure or defect concentration. Many of these simulations rely on tuning based on characteristics of the laser-induced melt pool, such as the melt pool geometry (length, width, and depth). Additionally, many of numerous interacting variables that make LPBF process so complex can be reduced and controlled by performing simple, single track experiments on bare (no powder) substrates, yet still produce important and applicable physical results. The 2018 Additive Manufacturing Benchmark (AM Bench) tests and measurements were designed for this application. This paper describes the experiment design for the tests conducted using LPBF on bare metal surfaces, and the measurement results for the melt pool geometry and melt pool cooling rate performed on two LPBF systems. Several factors, such as accurate laser spot size, were determined after the 2018 AM Bench conference, with results of those additional tests reported here.

A residual heat compensation based scan strategy for powder bed fusion additive manufacturing

Typical scan strategies for laser powder bed fusion (LPBF) additive manufacturing systems apply a constant laser power and scan speed. Localized preheating from adjacent scan paths (residual heat) result in inconsistent melt-pool morphology. A new control approach is proposed which compensates the residual heat through laser power adjustment. A model called residual heat factor (RHF) is developed to 'quantify' the residual heat effect, and laser power is controlled proportional to this RHF. Experiments are conducted on a custom-controlled LPBF testbed on nickel-alloy (IN625) bare plate, and the effects of this unique scan strategy are investigated by in-situ melt-pool monitoring.

Accurate determination of laser spot position during laser powder bed fusion process thermography

High-speed thermography is useful tool for researching the laser powder bed fusion process by providing thermal information in heat affected zone. However, it is not directly possible to ascertain the position of the laser spot with respect to the melt pool, which could provide key information regarding how laser energy is distributed and absorbed. In this paper, we demonstrate a procedure for registering the laser spot position with the melt pool using a bright illumination source co-axially aligned with the laser to project a sharp spot on the build plane. This spot is fixed to the laser position and used as a reference frame for registering the laser spot with the melt pool radiance temperature distribution. Measurement results demonstrate the effect of varying process parameters (laser power and scan speed) on the melt pool thermal field and respective position of the laser spot.

Part geometry and conduction-based laser power control for powder bed fusion additive manufacturing

Laser powder bed fusion (LPBF) uses a focused, high power laser to repeatedly scan geometric patterns on thin layers of metal powder, which build up to a final, solid three-dimensional (3D) part. This process is somewhat limited in that the parts tend to have poorer surface finish (compared to machining or grinding) and distortion due to residual stress, as well as multiple other deficiencies. Typical laser scan strategies are relatively simple and use constant laser power levels. This elicits local variations in the melt pool size, shape, or temperature, particularly near sharp geometric features or overhang structures due to the relatively higher thermal conductivity of solid metal compared to metal powder. In this paper, we present a new laser power control algorithm, which scales the laser power to a value called the geometric conductance factor (GCF). The GCF is calculated based on the amount of solid vs. powder material near the melt pool. The algorithm for calculating GCF is presented along with some basic examples for clarification. Then, we detail the hardware and software implementation on the National Institute of Standards and Technology (NIST) additive manufacturing metrology testbed (AMMT), which includes co-axial melt pool monitoring using a high-speed camera. Six parts were fabricated out of nickel superalloy 625 (IN625) with the same nominal laser power, but with varying GCF algorithm parameters. We demonstrate the effect of tailored laser power on reducing the variability of melt pool intensity measured throughout the 3D build. Finally, we contrast the difference between the 'optimized' part vs. the standard build parameters, including the deflection of the final part top surface near the overhang and the variation of surface finish on the down-facing surfaces. Ultimately, the improvements to the in-situ process monitoring and part qualities demonstrate the utility and future potential tuning and optimizing more complex laser scan strategies.

Process Monitoring Dataset from the Additive Manufacturing Metrology Testbed (AMMT): "Three-Dimensional Scan Strategies"

This document provides details on the files available in the dataset "20180708-HY-3D Scan Strategies" pertaining to a 3D additive manufacturing build performed on the Additive Manufacturing Metrology Testbed (AMMT)by Ho Yeung on July 8, 2018. The files include the input command files and in-situ process monitoring data, and metadata. This data is the first of future planned "AMMT Process Monitoring Reference Datasets," as part of the Metrology for Real-Time Monitoring of Additive Manufacturing project.

Identical and Nonidentical Twins: Risk and Factors Involved in Development of Islet Autoimmunity and Type 1 Diabetes

OBJECTIVE

There are variable reports of risk of concordance for progression to islet autoantibodies and type 1 diabetes in identical twins after one twin is diagnosed. We examined development of positive autoantibodies and type 1 diabetes and the effects of genetic factors and common environment on autoantibody positivity in identical twins, nonidentical twins, and full siblings.

RESEARCH DESIGN AND METHODS

Subjects from the TrialNet Pathway to Prevention Study (N = 48,026) were screened from 2004 to 2015 for islet autoantibodies (GAD antibody [GADA], insulinoma-associated antigen 2 [IA-2A], and autoantibodies against insulin [IAA]). Of these subjects, 17,226 (157 identical twins, 283 nonidentical twins, and 16,786 full siblings) were followed for autoantibody positivity or type 1 diabetes for a median of 2.1 years.

RESULTS

At screening, identical twins were more likely to have positive GADA, IA-2A, and IAA than nonidentical twins or full siblings (all P < 0.0001). Younger age, male sex, and genetic factors were significant factors for expression of IA-2A, IAA, one or more positive autoantibodies, and two or more positive autoantibodies (all P ≤ 0.03). Initially autoantibody-positive identical twins had a 69% risk of diabetes by 3 years compared with 1.5% for initially autoantibody-negative identical twins. In nonidentical twins, type 1 diabetes risk by 3 years was 72% for initially multiple autoantibody-positive, 13% for single autoantibody-positive, and 0% for initially autoantibody-negative nonidentical twins. Full siblings had a 3-year type 1 diabetes risk of 47% for multiple autoantibody-positive, 12% for single autoantibody-positive, and 0.5% for initially autoantibody-negative subjects.

CONCLUSIONS

Risk of type 1 diabetes at 3 years is high for initially multiple and single autoantibody-positive identical twins and multiple autoantibody-positive nonidentical twins. Genetic predisposition, age, and male sex are significant risk factors for development of positive autoantibodies in twins.

On thermal properties of metallic powder in laser powder bed fusion additive manufacturing

Powder thermal properties play a critical role in laser powder-bed fusion (LPBF) additive manufacturing, specifically, the reduced effective thermal conductivity compared to that of the solid significantly affects heat conduction, which can influence the melt pool characteristics, and consequently, the part mechanical properties. This study intends to indirectly measure the thermal conductivity of metallic powder, nickel-based super alloy 625 (IN625) and Ti-6Al-4V (Ti64), in LPBF using a combined approach that consists of laser flash analysis, finite element (FE) heat transfer modeling and a multivariate inverse method. The test specimens were designed and fabricated by a LPBF system to encapsulate powder in a hollow disk to imitate powder-bed conditions. The as-built specimens were then subjected to laser flash testing to measure the transient thermal response. Next, an FE model replicate the hollow disk samples and laser flash testing was developed. A multi-point optimization algorithm was used to inversely extract the thermal conductivity of LPBF powder from the FE model based on the measured transient thermal response. The results indicate that the thermal conductivity of IN625 powder used in LPBF ranges from 0.65 W/(m·K) to 1.02 W/(m·K) at 100 °C and 500 °C, respectively, showing a linear relationship with the temperature. On the other hand, Ti64 powder has a lower thermal conductivity than IN625 powder, about 35% to 40% smaller. However, the thermal conductivity ratio of the powder to the respective solid counterpart is quite similar between the two materials, about 4.2% to 6.9% for IN625 and 3.4% to 5.2% for Ti64.

A Type 1 Diabetes Genetic Risk Score Predicts Progression of Islet Autoimmunity and Development of Type 1 Diabetes in Individuals at Risk

OBJECTIVE

We tested the ability of a type 1 diabetes (T1D) genetic risk score (GRS) to predict progression of islet autoimmunity and T1D in at-risk individuals.

RESEARCH DESIGN AND METHODS

We studied the 1,244 TrialNet Pathway to Prevention study participants (T1D patients' relatives without diabetes and with one or more positive autoantibodies) who were genotyped with Illumina ImmunoChip (median [range] age at initial autoantibody determination 11.1 years [1.2-51.8], 48% male, 80.5% non-Hispanic white, median follow-up 5.4 years). Of 291 participants with a single positive autoantibody at screening, 157 converted to multiple autoantibody positivity and 55 developed diabetes. Of 953 participants with multiple positive autoantibodies at screening, 419 developed diabetes. We calculated the T1D GRS from 30 T1D-associated single nucleotide polymorphisms. We used multivariable Cox regression models, time-dependent receiver operating characteristic curves, and area under the curve (AUC) measures to evaluate prognostic utility of T1D GRS, age, sex, Diabetes Prevention Trial-Type 1 (DPT-1) Risk Score, positive autoantibody number or type, HLA DR3/DR4-DQ8 status, and race/ethnicity. We used recursive partitioning analyses to identify cut points in continuous variables.

RESULTS

Higher T1D GRS significantly increased the rate of progression to T1D adjusting for DPT-1 Risk Score, age, number of positive autoantibodies, sex, and ethnicity (hazard ratio [HR] 1.29 for a 0.05 increase, 95% CI 1.06-1.6; P = 0.011). Progression to T1D was best predicted by a combined model with GRS, number of positive autoantibodies, DPT-1 Risk Score, and age (7-year time-integrated AUC = 0.79, 5-year AUC = 0.73). Higher GRS was significantly associated with increased progression rate from single to multiple positive autoantibodies after adjusting for age, autoantibody type, ethnicity, and sex (HR 2.27 for GRS >0.295, 95% CI 1.47-3.51; P = 0.0002).

CONCLUSIONS

The T1D GRS independently predicts progression to T1D and improves prediction along T1D stages in autoantibody-positive relatives.

Toward determining melt pool quality metrics via coaxial monitoring in laser powder bed fusion

The current industry trend in metal additive manufacturing is towards greater real time process monitoring capabilities during builds to ensure high quality parts. While the hardware implementations that allow for real time monitoring of the melt pool have advanced significantly, the knowledge required to correlate the generated data to useful metrics of interest are still lacking. This research presents promising results that aim to bridge this knowledge gap by determining a novel means to correlate easily obtainable sensor data (thermal emission) to key melt pool size metrics (e.g., melt pool cross sectional area).

Genetic Testing for Steroid-Resistant-Nephrotic Syndrome in an Outbred Population

Background: Steroid-resistant nephrotic syndrome (SRNS) is a leading cause of end-stage kidney disease in children and young adults. Despite advances in genomic science that have led to the discovery of >50 monogenic causes of SRNS, there are no clear guidelines for genetic testing in clinical practice. Methods: Using high throughput sequencing, we evaluated 492 individuals from 181 families for mutations in 40 known SRNS genes. Causative mutations were defined as missense, truncating, and obligatory splice site variants with a minor allele frequency <1% in controls. Non-synonymous variants were considered pathogenic if determined to be deleterious by at least two in silico models. We further evaluated for differences in age at disease onset, family history of SRNS or chronic kidney disease, race, sex, renal biopsy findings, and extra-renal manifestations in subgroups with and without disease causing variants. Results: We identified causative variants in 40 of 181 families (22.1%) with SRNS. Variants in INF2, COL4A3, and WT1 were the most common, accounting for over half of all causative variants. Causative variants were identified in 34 of 86 families (39.5%) with familial disease and 6 of 95 individuals (6.3%) with sporadic disease (χ² p < 0.00001). Family history was the only significant clinical predictor of genetic SRNS. Conclusion: We identified causative mutations in almost 40% of all families with hereditary SRNS and 6% of individuals with sporadic disease, making family history the single most important clinical predictors of monogenic SRNS. We recommend genetic testing in all patients with SRNS and a positive family history, but only selective testing in those with sporadic disease.

A Combined Experimental-Numerical Method to Evaluate Powder Thermal Properties in Laser Powder Bed Fusion

Powder bed metal additive manufacturing (AM) utilizes a high-energy heat source scanning at the surface of a powder layer in a predefined area to be melted and solidified to fabricate parts layer by layer. It is known that powder bed metal AM is primarily a thermal process, and further, heat conduction is the dominant heat transfer mode in the process. Hence, understanding the powder bed thermal conductivity is crucial to process temperature predictions, because powder thermal conductivity could be substantially different from its solid counterpart. On the other hand, measuring the powder thermal conductivity is a challenging task. The objective of this study is to investigate the powder thermal conductivity using a method that combines a thermal diffusivity measurement technique and a numerical heat transfer model. In the experimental aspect, disk-shaped samples, with powder inside, made by a laser powder bed fusion (LPBF) system, are measured using a laser flash system to obtain the thermal diffusivity and the normalized temperature history during testing. In parallel, a finite element (FE) model is developed to simulate the transient heat transfer of the laser flash process. The numerical model was first validated using reference material testing. Then, the model is extended to incorporate powder enclosed in an LPBF sample with thermal properties to be determined using an inverse method to approximate the simulation results to the thermal data from the experiments. In order to include the powder particles' contribution in the measurement, an improved model geometry, which improves the contact condition between powder particles and the sample solid shell, has been tested. A multipoint optimization inverse heat transfer method is used to calculate the powder thermal conductivity. From this study, the thermal conductivity of a nickel alloy 625 powder in powder bed conditions is estimated to be 1.01 W/m K at 500°C. [DOI: 10.1115/1.4040877].

Influence of scan strategy and process parameters on microstructure and its optimization in additively manufactured nickel alloy 625 via laser powder bed fusion

Laser powder bed fusion (L-PBF) as an additive manufacturing process produces nearly fully dense nickel alloy 625 (IN625) parts with complex features. L-PBF generates surfaces and microstructure through directional solidification that can be controlled by scan strategies and selection of process parameters. This study provides experimental investigations on microstructure formation including sizes of cellular grains and growth directions of columnar grains on the nickel alloy 625 test coupons. The effects of process parameters including laser power, scan velocity, hatch distance, and scan strategy that produce various solidification cooling rates and thermal gradients during the process, which also contribute to resultant microstructure, have been analyzed. Optimization studies are conducted on several objectives to improve the productivity while controlling the process effects on the resultant microstructure using response surface regression, desirability functions, and multi-objective genetic algorithm optimization.

Predictive modeling and optimization of multi-track processing for laser powder bed fusion of nickel alloy 625

This paper presents an integrated physics-based and statistical modeling approach to predict temperature field and meltpool geometry in multi-track processing of laser powder bed fusion (L-PBF) of nickel 625 alloy. Multi-track laser processing of powder material using L-PBF process has been studied using 2-D finite element simulations to calculate temperature fields along the scan and hatch directions for three consecutive tracks for a moving laser heat source to understand the heating and melting process. Based on the predicted temperature fields, width, depth and shape of the meltpool is determined. Designed experiments on L-PBF of nickel alloy 625 powder material are conducted to measure the relative density and meltpool geometry. Experimental work is reported on the measured density of built coupons and meltpool size. Statistically-based predictive models using response surface regression for relative density, meltpool geometry, peak temperature, and time above melting point are developed and multi-objective optimization studies are conducted by using genetic algorithm and swarm intelligence.

Identifying uncertainty in laser powder bed fusion additive manufacturing models

As additive manufacturing (AM) matures, models are beginning to take a more prominent stage in design and process planning for AM. A limitation frequently encountered in AM models is a lack of indication about their precision and accuracy. Often overlooked, information on model uncertainty is required for validation of AM models, qualification of AM-produced parts, and uncertainty management. This paper presents a discussion on the origin and propagation of uncertainty in laser powder bed fusion (L-PBF) models. Four sources of uncertainty are identified: modeling assumptions, unknown simulation parameters, numerical approximations, and measurement error in calibration data. Techniques to quantify uncertainty in each source are presented briefly, along with estimation algorithms to diminish prediction uncertainty with the incorporation of online measurements. The methods are illustrated with a case study based on a transient, stochastic thermal model designed for melt pool width predictions. Model uncertainty is quantified for single track experiments and the effect of online estimation in overhanging structures is studied via simulation. The application of these concepts to estimation and control of the L-PBF process is suggested.

Optical design and Initial Results from The National Institute of Standards and Technology's AMMT/TEMPS Facility

The National Institute of Standards and Technology's (NIST) Physical Measurement and Engineering Laboratories are jointly developing the Additive Manufacturing Measurement Testbed (AMMT)/ Temperature and Emittance of Melts, Powders and Solids (TEMPS) facilities. These facilities will be co-located on an open architecture laser-based powder bed fusion system allowing users full access to the system's operation parameters. This will provide users with access to machine-independent monitoring and control of the powder bed fusion process. In this paper there will be emphasis on the AMMT, which incorporates in-line visible light collection optics for monitoring and feedback control of the powder bed fusion process. We shall present an overview of the AMMT/TEMPS program and its goals. The optical and mechanical design of the open architecture powder-bed fusion system and the AMMT will also be described. In addition, preliminary measurement results from the system along with the current status of the system will be described.

Thermographic Measurements of the Commercial Laser Powder Bed Fusion Process at NIST

Measurement of the high-temperature melt pool region in the laser powder bed fusion (L-PBF) process is a primary focus of researchers to further understand the dynamic physics of the heating, melting, adhesion, and cooling which define this commercially popular additive manufacturing process. This paper will detail the design, execution, and results of high speed, high magnification in-situ thermographic measurements conducted at the National Institute of Standards and Technology (NIST) focusing on the melt pool region of a commercial L-PBF process. Multiple phenomena are observed including plasma plume and hot particle ejection from the melt region. The thermographic measurement process will be detailed with emphasis on the 'measurability' of observed phenomena and the sources of measurement uncertainty. Further discussion will relate these thermographic results to other efforts at NIST towards L-PBF process finite element simulation and development of in-situ sensing and control methodologies.

Multiple Sensor Detection of Process Phenomena in Laser Powder Bed Fusion

Laser powder bed fusion (LPBF) is an additive manufacturing (AM) process in which a high power laser melts metal powder layers into complex, three-dimensional shapes. LPBF parts are known to exhibit relatively high residual stresses, anisotropic microstructure, and a variety of defects. To mitigate these issues, in-situ measurements of the melt-pool phenomena may illustrate relationships between part quality and process signatures. However, phenomena such as spatter, plume formation, laser modulation, and melt-pool oscillations may require data acquisition rates exceeding 10 kHz. This hinders use of relatively data-intensive, streaming imaging sensors in a real-time monitoring and feedback control system. Single-point sensors such as photodiodes provide the temporal bandwidth to capture process signatures, while providing little spatial information. This paper presents results from experiments conducted on a commercial LPBF machine which incorporated synchronized, in-situ acquisition of a thermal camera, high-speed visible camera, photodiode, and laser modulation signal during fabrication of a nickel alloy 625 AM part with an overhang geometry. Data from the thermal camera provides temperature information, the visible camera provides observation of spatter, and the photodiode signal provides high temporal bandwidth relative brightness stemming from the melt pool region. In addition, joint-time frequency analysis (JTFA) was performed on the photodiode signal. JTFA results indicate what digital filtering and signal processing are required to highlight particular signatures. Image fusion of the synchronized data obtained over multiple build layers allows visual comparison between the photodiode signal and relating phenomena observed in the imaging detectors.

Assessing the use of an infrared spectrum hyperpixel array imager to measure temperature during additive and subtractive manufacturing

Accurate non-contact temperature measurement is important to optimize manufacturing processes. This applies to both additive (3D printing) and subtractive (material removal by machining) manufacturing. Performing accurate single wavelength thermography suffers numerous challenges. A potential alternative is hyperpixel array hyperspectral imaging. Focusing on metals, this paper discusses issues involved such as unknown or changing emissivity, inaccurate greybody assumptions, motion blur, and size of source effects. The algorithm which converts measured thermal spectra to emissivity and temperature uses a customized multistep non-linear equation solver to determine the best-fit emission curve. Emissivity dependence on wavelength may be assumed uniform or have a relationship typical for metals. The custom software displays residuals for intensity, temperature, and emissivity to gauge the correctness of the greybody assumption. Initial results are shown from a laser powder-bed fusion additive process, as well as a machining process. In addition, the effects of motion blur are analyzed, which occurs in both additive and subtractive manufacturing processes. In a laser powder-bed fusion additive process, the scanning laser causes the melt pool to move rapidly, causing a motion blur-like effect. In machining, measuring temperature of the rapidly moving chip is a desirable goal to develop and validate simulations of the cutting process. A moving slit target is imaged to characterize how the measured temperature values are affected by motion of a measured target.

A prospective comparative study of microscope-integrated intraoperative fluorescein and indocyanine videoangiography for clip ligation of complex cerebral aneurysms

OBJECT

The authors prospectively analyzed 2 microscope-integrated videoangiography techniques using intravenous indocyanine green (ICG) and fluorescein for assessment of cerebral aneurysm obliteration and adjacent vessel patency.

METHODS

The authors prospectively enrolled 22 patients who underwent clip ligation of their aneurysm and used intraoperative videoangiography to assess obliteration of the aneurysmal sac and patency of the adjacent branching and perforating arteries. Patients underwent ICG videoangiography (ICG-VA) and the newly developed fluorescein videoangiography (FL-VA) using microscope-integrated fluorescence modules. Two independent observers compared the videoangiography recordings for value and quality to assess aneurysm exclusion and the patency of adjacent arteries.

RESULTS

All 22 patients first underwent FL-VA and then ICG-VA after clip application. In 7 cases (32%), FL-VA provided superior detail to assess perforating arteries (4 cases), distal branches (2 cases), and both (1 case); such detail was not readily available on ICG-VA. In 1 patient, ICG-VA offered better visualization of posterior communicating artery aneurysm occlusion than FL-VA because of staining artifact on the aneurysm dome from the adjacent tentorium. In 2 patients, FL-VA offered the needed advantage of real-time manipulation of the vessels and flow assessment by visualization through the operating microscope oculars. In 2 other cases, ICG-VA was more practical for repeat usage because of its more efficient clearance from the intravascular space. The ICG-VA image quality was often degraded at higher magnification in deep operative fields, partly due to chromatic aberration. Both ICG-VA and FL-VA afforded restricted views of vasculature based on the angle of surgical approach and obscuration by blood clot, aneurysm, or brain tissue.

CONCLUSIONS

Compared with ICG-VA, FL-VA can potentially provide an improved visualization of vasculature at high magnification in deep surgical fields. ICG-VA is more effective for repeated use during clip repositioning due to ICG's minimal vascular wall extravasation. Therefore, in certain cases, FL-VA may offer some advantages and play a complementary role along with ICG-VA in intraoperative fluorescence evaluation during microsurgical management of aneurysms.

Associations of baseline characteristics with evolution of eGFR in a referred chronic kidney disease cohort

BACKGROUND

Currently, most chronic kidney disease (CKD) classifications identify patients at different stages of CKD but do not identify risk of progression or adverse outcome. This analysis aims to describe associations between baseline characteristics and the evolution of estimated glomerular filtration rate (eGFR) and identify threshold values for clinical parameters that maximally discriminate progression to renal replacement therapy (RRT) in a referred cohort of patients with CKD stages 3-5.

DESIGN AND METHODS

A longitudinal mixed-effect model was used to determine annualized estimated change in eGFR and classification tree analysis to identify threshold values that maximally discriminate progression to RRT.

RESULTS

A total of 1316 patients were available for analysis with median follow-up of 33 months (interquartile range 20-60). Mixed model analysis suggested that the underlying diagnoses of autosomal dominant polycystic kidney disease and diabetic nephropathy exhibited on average a 2.7 (0.3) and 0.7 (0.3) ml/min/year faster rate of decline in eGFR, respectively, compared to those patients with biopsy-proven glomerulonephritis. In the regression tree analysis, we attempted to identify threshold values for clinical parameters that maximally discriminate progression to RRT. eGFR ≤24 ml/min was the first ranked discriminator, diastolic blood pressure appeared in the second and fourth rounds, eGFR appeared again in the third round together with cholesterol and systolic blood pressure, with basal metabolic index in the fourth.

CONCLUSION

This analysis highlights risk factors for progressive kidney disease and demonstrates the variability in evolution of eGFR across the cohort as well as the importance of underlying renal disease type on the progression of CKD.

The heparin-binding protein interactome in pancreatic diseases

BACKGROUND

The cellular microenvironment plays an important role in the regulation of homoeostasis and is a source of potential biomarkers and drug targets. In a genome-wide analysis the extracellular proteins that bind to heparin (HBPs) have been shown to form highly modular and interconnected extracellular protein regulatory networks. Using a systems biology approach, we have investigated the role of HBP networks in the normal pancreas and pancreatic digestive diseases.

METHODS

Lists of mRNAs encoding for HBPs associated with the normal pancreas (NP), acute pancreatitis (AP), chronic pancreatitis (CP) and pancreatic ductal adenocarcinoma (PDAC) were obtained using public databases and publications. Networks of the putative protein interactomes derived from mRNA expression data of HBPs were built and analysed using cluster analysis, gene ontology term enrichment and canonical pathways analysis.

RESULTS

The extracellular heparin-binding putative protein interactomes in the pancreas were better connected than their non heparin-binding counterparts, having higher clustering coefficients in the normal pancreas (0.273), acute pancreatitis (0.457), chronic pancreatitis (0.329) and pancreatic ductal adenocarcinoma (0.269). 'Hepatic Fibrosis/Hepatic Stellate Cell Activation' appears to be a significant canonical pathway in pancreatic homoeostasis in health and disease with a large number of important HBPs.

CONCLUSIONS

Our analyses clearly demonstrate that HBPs form disease-specific and highly connected networks that can be explored for potential biomarkers and as collective drug targets via the modification of heparin binding properties.

Major themes for 2011 in cardiovascular anesthesia and intensive care

The past year has witnessed major advances in of cardiovascular anesthesia and intensive care. Perioperative interventions such as anesthetic design, inotrope choice, glycemic therapy, blood management, and noninvasive ventilation have significant potential to enhance perioperative outcomes even further.The major theme for 2011 is the international consensus conference that focused on ancillary interventions likely to reduce mortality in cardiac anesthesia and intensive care. This landmark conference prioritized volatile anesthetics, levosimendan, and insulin therapy for their promising life-saving perioperative potential. Although extensive evidence has demonstrated the cardioprotective effects of volatile anesthetics, levosimendan as well as glucose, insulin and potassium therapy, the clinical relevance of these beneficial effects remains to be fully elucidated. Furthermore, controversy still persists about how tight perioperative glucose control should be in adult cardiac surgery because of the risk of hypoglycemia.A second major theme in 2011 has been perioperative hemostasis with the release of multispecialty guidelines. Furthermore, hemostatic agents such as recombinant factor VIIa and tranexamic acid have been studied intensively, even in the setting of major non-cardiac surgery. This review then highlights the remaining two major themes for 2011, namely the expanding role of noninvasive ventilation in our specialty and the formation of the Roland Hetzer International Cardiothoracic and Vascular Surgery Society.In conclusion, it is time for large adequately powered multicenter trials to test whether prioritized perioperative interventions truly reduce mortality and morbidity in cardiac surgical patients. This essential paradigm shift represents a major clinical opportunity for the global cardiovascular anesthesia and critical care community.

ReishiMax, mushroom based dietary supplement, inhibits adipocyte differentiation, stimulates glucose uptake and activates AMPK

Background

Obesity is a health hazard which is closely associated with various complications including insulin resistance, hypertension, dyslipidemia, atherosclerosis, type 2 diabetes and cancer. In spite of numerous preclinical and clinical interventions, the prevalence of obesity and its related disorders are on the rise demanding an urgent need for exploring novel therapeutic agents that can regulate adipogenesis. In the present study, we evaluated whether a dietary supplement ReishiMax (RM), containing triterpenes and polysaccharides extracted from medicinal mushroom Ganoderma lucidum, affects adipocyte differentiation and glucose uptake in 3T3-L1 cells.

Methods

3T3-L1 pre-adipocytes were differentiated into adipocytes and treated with RM (0-300 μg/ml). Adipocyte differentiation/lipid uptake was evaluated by oil red O staining and triglyceride and glycerol concentrations were determined. Gene expression was evaluated by semi-quantitative RT-PCR and Western blot analysis. Glucose uptake was determined with [³H]-glucose.

Results

RM inhibited adipocyte differentiation through the suppresion of expression of adipogenic transcription factors peroxisome proliferator-activated receptor-γ (PPAR-γ), sterol regulatory element binding element protein-1c (SREBP-1c) and CCAAT/enhancer binding protein-α (C/EBP-α). RM also suppressed expression of enzymes and proteins responsible for lipid synthesis, transport and storage: fatty acid synthase (FAS), acyl-CoA synthetase-1 (ACS1), fatty acid binding protein-4 (FABP4), fatty acid transport protein-1 (FATP1) and perilipin. RM induced AMP-activated protein kinase (AMPK) and increased glucose uptake by adipocytes.

Conclusion

Our study suggests that RM can control adipocyte differentiation and glucose uptake. The health benefits of ReishiMax warrant further clinical studies.

Risk factors associated with major cerebrovascular complications after intracranial stenting

BACKGROUND

There are limited data on the relationship between patient and site characteristics and clinical outcomes after intracranial stenting.

METHODS

We performed a multivariable analysis that correlated patient and site characteristics with the occurrence of the primary endpoint (any stroke or death within 30 days of stenting or stroke in the territory of the stented artery beyond 30 days) in 160 patients enrolled in this stenting registry. All patients presented with an ischemic stroke, TIA, or other cerebral ischemic event (e.g., vertebrobasilar insufficiency) in the territory of a suspected 50-99% stenosis of a major intracranial artery while on antithrombotic therapy.

RESULTS

Cerebral angiography confirmed that 99% (158/160) of patients had a 50-99% stenosis. In multivariable analysis, the primary endpoint was associated with posterior circulation stenosis (vs anterior circulation) (hazard ratio [HR] 3.4, 95% confidence interval [CI] 1.2-9.3, p = 0.018), stenting at low enrollment sites (< 10 patients each) (vs high enrollment site) (HR 2.8, 95% CI 1.1-7.6, p = 0.038), < or = 10 days from qualifying event to stenting (vs > or = 10 days) (HR 2.7, 95% CI 1.0-7.8, p = 0.058), and stroke as a qualifying event (vs TIA/other) (HR 3.2, 95% CI 0.9-11.2, p = 0.064). There was no significant difference in the primary endpoint based on age, gender, race, or percent stenosis (50-69% vs 70-99%).

CONCLUSIONS

Major cerebrovascular complications after intracranial stenting may be associated with posterior circulation stenosis, low volume sites, stenting soon after a qualifying event, and stroke as the qualifying event. These factors will need to be monitored in future trials of intracranial stenting.