Lateral forces determine dimensional accuracy of the narrow-kerf sawing of wood

The shrinking global forest area limits the supply of industrially usable raw resources. This, in combination with the ever-increasing consumption of timber due to population growth can lead to the lack of a positive balance between the annual volumetric growth and consumption of wood. An important innovation toward increasing environmental and economic sustainability of timber production is to reduce the volume of wood residues by minimizing the sawing kerf. It results in higher material yield but may impact the dimensional accuracy of derived products. Therefore, the cutting tool geometry as well as the sawing process as a whole must be carefully optimized to assure optimal use of resources. The goal of this study is to better understand the causes of machining errors that occur when sawing wood with saws of varying thickness of kerf, with a special focus on re-sawing thin lamellae performed on the gang saw. Numerical simulations were tested against experimental results, considering influence of diverse components of cutting forces, in addition to the initial and operating stiffness coefficients of the saw blade. It has been demonstrated that asymmetric loads from the cutting process for the scraper saw blade can cause sawing inaccuracies. The simulation methodology developed in this research can be straightforwardly extended towards determination of optimal geometry of other cutting tools, particularly with the reduced sawing kerf. This may lead to more sustainable use of natural resources as well as an increase in economic gain for the wood processing industries.

Stress generation, relaxation and size control in confined tumor growth

Experiments on tumor spheroids have shown that compressive stress from their environment can reversibly decrease tumor expansion rates and final sizes. Stress release experiments show that nonuniform anisotropic elastic stresses can be distributed throughout. The elastic stresses are maintained by structural proteins and adhesive molecules, and can be actively relaxed by a variety of biophysical processes. In this paper, we present a new continuum model to investigate how the growth-induced elastic stresses and active stress relaxation, in conjunction with cell size control feedback machinery, regulate the cell density and stress distributions within growing tumors as well as the tumor sizes in the presence of external physical confinement and gradients of growth-promoting chemical fields. We introduce an adaptive reference map that relates the current position with the reference position but adapts to the current position in the Eulerian frame (lab coordinates) via relaxation. This type of stress relaxation is similar to but simpler than the classical Maxwell model of viscoelasticity in its formulation. By fitting the model to experimental data from two independent studies of tumor spheroid growth and their cell density distributions, treating the tumors as incompressible, neo-Hookean elastic materials, we find that the rates of stress relaxation of tumor tissues can be comparable to volumetric growth rates. Our study provides insight on how the biophysical properties of the tumor and host microenvironment, mechanical feedback control and diffusion-limited differential growth act in concert to regulate spatial patterns of stress and growth. When the tumor is stiffer than the host, our model predicts tumors are more able to change their size and mechanical state autonomously, which may help to explain why increased tumor stiffness is an established hallmark of malignant tumors.

A daily basin-wide sea ice thickness retrieval methodology: Stefan's Law Integrated Conducted Energy (SLICE)

As changes to Earth’s polar climate accelerate, the need for robust, long–term sea ice thickness observation datasets for monitoring those changes and for verification of global climate models is clear. By coupling a recently developed algorithm for retrieving snow–ice interface temperature from passive microwave satellite data to a thermodynamic sea ice energy balance relation known as Stefan's Law, we have developed a new retrieval method for estimating thermodynamic sea ice thickness growth from space: Stefan’s Law Integrated Conducted Energy (SLICE). The advantages of the SLICE retrieval method include daily basin-wide coverage and a potential for use beginning in 1987. The method requires an initial condition at the beginning of the sea ice growth season in order to produce absolute sea ice thickness and cannot as yet capture dynamic sea ice thickness changes. Validation of the method against ten ice mass balance buoys using the ice mass balance buoy thickness as the initial condition show a mean correlation of 0.991 and a mean bias of 0.008 m over the course of an entire sea ice growth season. Estimated Arctic basin-wide sea ice thickness from SLICE for the sea ice growth seasons beginning between 2012 through 2019 capture a mean of 12.0 % less volumetric growth than a CryoSat-2 and Soil Moisture and Ocean Salinity (SMOS) merged sea ice thickness product (CS2SMOS) and a mean of 8.3 % more volumetric growth than the Pan-Arctic Ice–Ocean Modeling and Assimilation System (PIOMAS). The spatial distribution of the sea ice thickness differences between the retrieval results and those reference datasets show patterns consistent with expected sea ice thickness changes due to dynamic effects. This new retrieval method is a viable basis for a long–term sea ice thickness climatology, especially if dynamic effects can be captured through inclusion of an ice motion dataset.

Tumor Doubling Time Using CT Volumetric Segmentation in Metastatic Adrenocortical Carcinoma

Adrenocortical carcinoma (ACC) is a rare malignancy with an overall unfavorable prognosis. Clinicians treating patients with ACC have noted accelerated growth in metastatic liver lesions that requires rapid intervention compared to other metastatic locations. This study measured and compared the growth rates of metastatic ACC lesions in the lungs, liver, and lymph nodes using volumetric segmentation. A total of 12 patients with metastatic ACC (six male; six female) were selected based on their medical history. Computer tomography (CT) exams were retrospectively reviewed and a sampling of ≤5 metastatic lesions per organ were selected for evaluation. Lesions in the liver, lung, and lymph nodes were measured and evaluated by volumetric segmentation. Statistical analyses were performed to compare the volumetric growth rates of the lesions in each organ system. In this cohort, 5/12 had liver lesions, 7/12 had lung lesions, and 5/12 had lymph node lesions. A total of 92 lesions were evaluated and segmented for lesion volumetry. The volume doubling time per organ system was 27 days in the liver, 90 days in the lungs, and 95 days in the lymph nodes. In this series of 12 patients with metastatic ACC, liver lesions showed a faster growth rate than lung or lymph node lesions.

3D Microenvironment-Specific Mechanosensing Regulates Neural Stem Cell Lineage Commitment

While extracellular matrix (ECM) mechanics strongly regulate stem cell commitment, the field′s mechanistic understanding of this phenomenon largely derives from simplified two–dimensional (2D) culture substrates. Here we found a three-dimensional (3D) matrix–specific mechanoresponsive mechanism for neural stem cell (NSC) differentiation. NSC lineage commitment in 3D is maximally stiffness-sensitive in the range of 0.1–1.2 kPa, a narrower and more brain-mimetic range than we had previously identified in 2D (0.75–75 kPa). Transcriptomics revealed stiffness-dependent upregulation of early growth response 1 (Egr1) in 3D but not in 2D. Egr1 knockdown enhanced neurogenesis in stiff ECMs by driving β–catenin nuclear localization and activity in 3D, but not in 2D. Mechanical modeling and experimental studies under osmotic pressure indicate that stiff 3D ECMs are likely to stimulate Egr1 via increases in confining stress during cell volumetric growth. To our knowledge, Egr1 represents the first 3D–specific stem cell mechanoregulatory factor.

P14.02 The Natural History of a Residual Intracranial Meningioma- Volumetric Growth and Predictors of Progression

BACKGROUND Resection of meningioma leaves residual solid tumour in ~25% of patients. Selection for further treatment and follow-up strategy may benefit from knowledge of volumetric growth and associated prognostic factors. MATERIAL AND METHODS Growth rates were assessed using a linear mixed effects model, in a retrospective adult cohort that underwent subtotal resection of meningioma (2004–2018). Endpoints were re-treatment, end of follow-up or death. Cox regression analysis was used to identify prognostic factors for progression, defined using the Response Assessment in Neuro-Oncology (RANO) volumetric criteria. RESULTS 236 patients were included. Mean age at surgery was 56.3 years (SD=13.7) and 73.7% were female. WHO grades were 1 (n=195, 82.6%), 2 (n=40, 16.9%) and 3 (n=1, 0.5%). Adjuvant fractionated radiotherapy (fRT) was administered to 34 patients (14.4%), with no propensity towards higher WHO grade or residual volume. Median pre-operative meningioma and post-operative residual volumes were 34.0cm3 (IQR 16.0–63.0) and 2.0cm3 (IQR 0.8–5.2), respectively. Median follow-up was 64 months (IQR 42–104). Median absolute growth rate (AGR) and relative growth rate (RGR) were 0.1cm3/year and 4.3%/year, respectively. According to RANO criteria, 132 (55.9%) patients progressed, of which 13 (9.8%) developed symptoms. Median progression-free survival was 56 months (95% CI 43.1–69.0). Multivariable analysis identified adjuvant fRT (HR 1.7, [95% CI 1.0–2.8], P=0.046), skull base location (HR 1.5, [95% CI 1.0–2.4], P=0.047) and Ki-67 index (HR 3.7 [95% CI 1.3–10.8], P=0.017) as prognostic factors for volumetric progression. WHO grade was not significant (HR 1.0, [95% CI 0.5–1.7], P=0.905). Forty-nine patients who progressed (37.1%) underwent further treatment: fRT (n=19), re-operation (n=15), Stereotactic radiosurgery (SRS) (n=10) and surgery+adjuvant fRT (n=5). Of those, 8 (16.3%) progressed further (after re-operation [n=6] and SRS [n=2]). Seven were treated with a 2nd re-operation (n=3), fRT (n=3), and SRS (n=1). One patient progressed after a 2nd reoperation and was treated with SRS, after which they remained stable. Median survival was not reached. 5- and 10-year overall survival (OS) was 96% and 86% respectively. CONCLUSION Growth rates of a residual meningioma vary with a dichotomy observed in progression rates. Half of patients with a residual meningioma showed radiological progression requiring multiple treatment to control the tumour. The other half demonstrate a more indolent course. Skull base location and higher Ki67 are important prognostic factors for progression and therefore, should be considered to stratify patients for adjuvant radiotherapy.

Hearing loss and volumetric growth rate in untreated vestibular schwannoma

OBJECTIVE In this study, the authors aimed to clarify the relationship between hearing loss and tumor volumetric growth rates in patients with untreated vestibular schwannoma (VS). METHODS Records of 128 treatment-naive patients diagnosed with unilateral VS between 2012 and 2018 with serial audiometric assessment and MRI were reviewed. Tumor growth rates were determined from initial and final tumor volumes, with a median follow-up of 24.3 months (IQR 8.5–48.8 months). Hearing changes were based on pure tone averages, speech discrimination scores, and American Academy of Otolaryngology–Head and Neck Surgery hearing class. Primary outcomes were the loss of class A hearing and loss of serviceable hearing, estimated using the Kaplan-Meier method and with associations estimated from Cox proportional hazards models and reported as hazard ratios. RESULTS Larger initial tumor size was associated with an increased risk of losing class A (HR 1.5 for a 1-cm3 increase; p = 0.047) and serviceable (HR 1.3; p < 0.001) hearing. Additionally, increasing volumetric tumor growth rate was associated with elevated risk of loss of class A hearing (HR 1.2 for increase of 100% per year; p = 0.031) and serviceable hearing (HR 1.2; p = 0.014). Hazard ratios increased linearly with increasing growth rates, without any evident threshold growth rate that resulted in a large, sudden increased risk of hearing loss. CONCLUSIONS Larger initial tumor size and faster tumor growth rates were associated with an elevated risk of loss of class A and serviceable hearing.

Volumetric growth rates of untreated cavernous sinus meningiomas

OBJECTIVE Meningiomas that arise primarily within the cavernous sinus are often believed to be more indolent in their growth pattern. Despite this perceived growth pattern, disabling symptoms can arise even with small tumors. While research has been done on cavernous sinus meningiomas (CSMs) and their treatment, very little is known about their natural growth rates. With a better understanding of the growth rate of CSM, patient treatment and guidance can be can optimized and individualized. The goal of this study was to determine volumetric growth rates of untreated CSMs. METHODS Thirty-seven patients with 166 MR images obtained between May 2004 and September 2019 were reviewed, with a range of 2–13 MR images per patient (average of 4.5 MR images per patient). These scans were obtained over an average follow-up period of 45.9 months (median 33.8, range 2.8–136.9 months). All imaging prior to any intervention was included in this analysis. Volumetric measurements were performed and assessed over time. RESULTS The estimated volumetric growth rate was 23.3% per year (95% CI 10.2%–38.0%, p < 0.001), which is equivalent to an estimated volume doubling time (VDT) of 3.3 years (95% CI 2.1–7.1 years). There was no significant relationship between growth rate and patient age (p = 0.09) or between growth rate and patient sex (p = 0.78). The median absolute growth rate was 41% with a range of −1% to 1793%. With a definition of “growth” as an increase of greater than 20% during the observed period, 65% of tumors demonstrated growth within their observation interval. Growth rates for each tumor were calculated and tumors were segmented based on growth rate. Of 37 patients, 22% (8) demonstrated no growth (< 5% annual growth, equivalent to a VDT > 13.9 years), 32% (12) were designated as slow growth (annual growth rate 5%–20%, VDT 3.5–13.9 years), 38% (14) were found to have medium growth (annual growth rate 20%–100%, VDT 0.7–3.5 years), and 8% were considered fast growing (annual growth rate > 100%, VDT < 0.7 years). CONCLUSIONS This study evaluated CSM volumetric growth rates. A deeper understanding of the natural history of untreated CSMs allows for better counseling and management of patients.