Free Disk Research Articles

Hands-on parallel & distributed computing with Raspberry Pi devices and clusters

Parallel and distributed computing (PDC) concepts are now required topics for accredited undergraduate computer science programs. However, introducing PDC into the CS curriculum is challenging for several reasons, including an instructor's lack of PDC knowledge and difficulties in accessing PDC hardware. This paper addresses both of these challenges by presenting free, interactive, web-based PDC teaching modules using inexpensive Raspberry Pi single board computers (SBCs). Our materials include a free disk image that makes it possible for instructors to build Raspberry Pi clusters in minutes and use our software in a variety of curricular contexts. Our multi-year assessment of these materials on students and faculty members indicates that: (i) our materials increased students' confidence regarding important PDC concepts and motivated them to study PDC further; and (ii) our materials increased faculty members' confidence and preparedness in teaching key PDC concepts at their own institutions.

Drip-Dry Strategy Assisted Blu-Ray Disc Biosensor for Fast Point of Care Testing.

Discs and numerous other consumer products have been developed for point of care testing (POCT) to replace traditional large and expensive biochemical devices in certain scenarios. Herein, we propose a drip-dry strategy (2D strategy) assisted Blu-ray disc (BD) biosensor, termed BDB, for rapid and portable POCT within 30 min with the cost of a single test < $1. The platform utilizes the covered area formed by the deposition of the substance to be measured on the activated BD surface after the evaporation of water and realizes the quantitative detection of the target through the error readout of free disc quality diagnosis software. As a proof of concept, we first demonstrated the feasibility of direct quantitative detection of substances in solution in a single system through the detection of pure proteins avoiding colorimetric reagent used in traditional optical detection. For the complex mixed systems, we then innovatively utilize the principle that soluble targets promote/inhibit the dissolution of insoluble precipitates to achieve specific detection of targets and successfully apply BDB to the indirect quantitative detection of glutathione (GSH) with LOD of 0.447 mM in the range of 2-16 mM and organophosphorus pesticides (OPs) with LOD of 2.122 × 10-7 M in the range of 1.289 × 10-7-1.289 × 10-4 M. The BDB is widely applicable, easy to operate, and less time-consuming, which is anticipated to provide an alternative method for early, on-site detection or screening.

Existence of free boundary disks with constant mean curvature in [formula omitted]

Given a surface Σ in R3 diffeomorphic to S2, Struwe [38] proved that for almost every H below the mean curvature of the smallest sphere enclosing Σ, there exists a branched immersed disk which has constant mean curvature H and boundary meeting Σ orthogonally. We reproduce this result using a different approach and improve it under additional convexity assumptions on Σ. Specifically, when Σ itself is convex and has mean curvature bounded below by H0, we obtain existence for all H∈(0,H0). Instead of the heat flow in [38], we use a Sacks-Uhlenbeck type perturbation. As in previous joint work with Zhou [7], a key ingredient for extending existence across the measure zero set of H's is a Morse index upper bound.

Numerical Investigation of Flow Structure and Pressure Drop Prediction for Radial Inflow between Co-Rotating Discs with Negative Effective Inlet Swirl Ratio

Abstract This paper presents a numerical simulation of the flow structure of radial inflow between co-rotating discs with a negative ceff (effective inlet swirl ratio), which may occur in a vortex reducer equipped with deswirl nozzles. When the value of ceff approaches zero, asymmetric flow structure is observed in the cavity, possibly as a result of the ‘Coanda effect’. Besides this, the flow structure inside the disc cavity at ceff &amp;lt; 0 can be divided into a source region, a sink region, an interior core region, and two Ekman layers, which is identical to the situation when 0 &amp;lt; ceff = 1. However, there exist two distinct patterns: the stagnation point on the disc and on the peripheral. According to a theoretical analysis, ceff = -1/8 is used to distinguish between these two patterns. Based on flow structure partitioning, a theoretical model for predicting the swirl ratio radial distribution and pressure drop in a disc cavity with ceff &amp;lt; 0 was established. The model employs the turbulent boundary layer integral method, and von Karman's assumption of velocity profile and wall shear stress for a free disc. The calculation results of the swirl ratio in the cavity are in good agreement with the CFD results except when the negative ceff approaches zero because of the deviation of the radial velocity profile from the ‘1/7’ power law. Furthermore, pressure drop prediction across the cavity by the model has been verified through comparison with public experimental results.

Rigidity of Free Boundary Minimal Disks in Mean Convex Three-Manifolds

Rigidity of Free Boundary Minimal Disks in Mean Convex Three-Manifolds

Nymphanthus namkadingensis, a new species of Phyllanthaceae from Laos

A new species of Nymphanthus (Phyllanthaceae), N. namkadingensis from Bolikhamxai Province, central Laos, is described and illustrated, along with its vernacular name and preliminary conservation status. The new species is similar to N. rubescens, but distinguished by having larger stipules, longer pedicels, and connate annular disc glands (vs. free disc glands) of pistillate flowers.

Posterior epidural migration of huge free lumbar disc herniation with space occupying of vertebral canal:a case report and literature review

Posterior epidural migration of huge free lumbar disc herniation with space occupying of vertebral canal:a case report and literature review

Rational Cuntz states peak on the free disk algebra

AbstractWe apply realization theory of noncommutative (NC) rational multipliers of the Fock space, or free Hardy space of square–summable power series in several noncommuting variables to the convex analysis of states on the Cuntz algebra. We show, in particular, that a large class of Cuntz states that arise as the “NC Clark measures” of isometric NC rational multipliers are peak states for Popescu's free disk algebra in the sense of Clouâtre and Thompson.

First eigenvalues of free boundary hypersurfaces in the unit ball along the inverse mean curvature flow

In this note, we consider the first nonzero eigenvalue λp,1 of the p-Laplacian on free boundary proper hypersurfaces in the unit ball evolving along the inverse mean curvature flow. We show that λp,1 is monotone decreasing along the flow. Using the convergence of free boundary disks in the unit ball, we give a lower bound of λp,1 of a free boundary disk type hypersurface in the unit ball.

A Morphometric Study Analyzing the Anterior Epidural Space Volume Throughout Childhood

BACKGROUND: Following disc herniations, fragments migrate into the anterior epidural space within the lumbar spine. Although the volume of this area has been previously described in the adult population, the volume is relatively unknown within children. OBJECTIVES: Investigate the relative volume in the lumbar anterior epidural space within the growing spine by using imaging studies. STUDY DESIGN: Retrospective chart review. SETTING: University Medical Center in Lubbock Texas. A teaching hospital affiliated with Texas Tech University Health Sciences Center. METHODS: We conducted a retrospective review of the charts of pediatric patients seen at our institution from 2018 through 2020. Charts chosen for our investigation contained computed tomography imaging of the lumber spine, showing no deformities. Thirty patients were stratified equally among 3 age groups, 2-5 years old, 10-12 years old, and 16-18 years old. The anterior epidural space was measured in each patient 3 times using the previously reported method used by Teske et al (1). Results were compared with a combination of analysis of variance (ANOVA) and single tail paired t test. RESULTS: There was a statistically significant difference in the anterior epidural space size among age groups at all levels of the lumbar spine. When comparing only 2 groups together, the younger age group had anterior epidural space sizes significantly smaller than the other age group for all levels of the lumbar spine. The 10-12 age group had a significantly smaller space in the anterior epidural space than the 16–18-year olds only at the level of L2, L4, and L5 (P = 0.048,0.039, and 0.031, respectively). Within the 16–18-year age group, the anterior epidural space was significantly different between L4 and L3 and L2 and L3 (P &lt; 0.001 and P = 0.019, respectively). LIMITATIONS: Our study is limited by its retrospective nature and the sample size of the patient groups. Furthermore, the use of computed tomography imaging and not making physical measurements limits our accuracy. CONCLUSION: The volume of the anterior epidural space is smaller in the pediatric population than the adult population. The inability of herniated discs to fit within the epidural space in children and adolescents could potentially be the cause of the increased failure of conservative treatment for pediatric lumbar disc herniations. KEY WORDS: Anterior epidural space, lumbar herniated disc, low back pain, fossa corporis vertebralis dorsalis, free disc fragment, lumbar spine anatomy

Exploring therapeutic potential of Woodfordia fruticosa (L.) Kurz leaf and bark focusing on antioxidant, antithrombotic, antimicrobial, anti-inflammatory, analgesic, and antidiarrheal properties.

The study aimed to evaluate the pharmacological properties of methanolic extracts of leaves and barks of Woodfordia fruticosa (L.) Kurz (family: Lythraceae) focusing on antioxidant, thrombolytic, anti-inflammatory, antibacterial, analgesic, and antidiarrheal effects. 1,1-Diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging assay, clot lysis, disc diffusion, and membrane stabilizing methods were employed to assess in vitro antioxidant, thrombolytic, antibacterial, and anti-inflammatory properties of the leaf and bark methanolic extracts (ME) of W. fruticosa and different organic solvents, that is, petroleum ether (PE), dichloromethane (DCM), chloroform (CL), and aqueous (AQ) fractions. In addition, in vivo central and peripheral analgesic and antidiarrheal activities of both crude extracts were evaluated at two doses (200 and 400 mg/kg of body weight [bw]). All the extracts and fractions showed promising antioxidant properties by scavenging DDPH free radicals with IC50 of 6.11-20.79 μg/mL. AQ fraction (41.24%) of leaves and ME (44.90%) of bark exerted notable in vitro thrombolytic activity. The CL fraction of leaves and AQ fraction of the bark showed 43.16% and 45.37% inhibition of RBC hemolysis, respectively, compared to the inhibition of RBC hemolysis by aspirin in a hypotonic-induced membrane stabilizing assay. Besides, both extracts were observed to provide significant (p < 0.001) central and peripheral analgesic responses at both doses of 200 and 400 mg/kg bw. Furthermore, both doses of bark extract (p < 0.001) and the 400 mg/kg bw of leaf extract (p < 0.05) were observed to possess statistically significant antidiarrheal activity. Additionally, in an in vivo acute toxicity investigation, both extracts had a median lethal dose (LD50) greater than 5000 mg/kg bw, indicating their safety level. The current study proves the ethnomedicinal uses of W. fruticosa; however, further studies are required for phytochemical screening to isolate the responsible bioactive compounds and discover the lead molecules from the plant species.

Investigating the biocompatibility, flexural strength, and surface roughness of denture base resin containing copper oxide nanoparticles: An in vitro study

AimThis study aimed to evaluate the biocompatibility, flexural strength, and surface roughness of polymethyl methacrylate (PMMA) containing Copper Oxide Nanoparticles (CuO NPs) at different concentrations. Methods25 heat-polymerized PMMA wax patterns fabricated in 5 groups containing 0.5, 5, 50, and 500 μg/ml CuO NPs and nanoparticle (NP)-free PMMA discs were prepared. 5 growth mediums (DMEM with 10% FBS and 1% penicillin-streptomycin) without disks were also incubated similarly to serve as the control groups. The cytotoxicity of the discs was measured by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay on cultured Human Gingival Fibroblasts. The number of 1.3 × 104 cells were seeded in each well of 96-well plates (5 wells for the extract of each specimen). Days 1, 3, 5, and 7 were the intervals that the culture media were in direct contact with the PMMA discs for either 24 or 72 h. After that, a total of 40 specimens with 65 × 10 × 2.5 mm dimensions were prepared in five groups (n = 8). The specimens were subjected to a rugosimeter for the evaluation of surface roughness. The flexural strength test was performed using a universal testing machine. Microscopic evaluation was performed for the dispersion of the NPs. Non-parametric Kruskal-Wallis test and parametric one-way ANOVA test were used for data analysis. ResultsThe samples containing 500 μg/ml NPs showed the lowest percentage of cell viability at all incubation periods, while the highest cell viability was observed in NP-free PMMA 24 h after the seventh day of incubation. NPs at 50 and 500 μg/ml concentrations showed strongly significant differences in cytotoxicity compared to the 0 concentration and the control group (p < 0.001). Although all the samples demonstrated an increasing pattern of cell viability on the third, fifth, and seventh days, the percentage of cell viability was significantly lower after 72 h than after 24 h in all incubation periods (p < 0.001). NPs significantly increased flexural strength (p = 0.005) but did not affect the surface roughness of the PMMA discs (p = 0.396). SignificanceThe CuO NPs were cytotoxic only when applied in high concentrations, but presented a descending trend over time. No cytotoxic effect was observed in the experimental groups after seven days of incubation. Furthermore, CuO NPs increased flexural strength, but the surface roughness of the PMMA discs was not affected.

Feasibility of enlarging the ventral space by using a drill under spinal endoscopy in the treatment of severe free lumbar disc herniation

To evaluate the clinical efficacy of spinal endoscopy in the treatment of severe free lumbar disc herniation and explore the feasibility and application of microscopic drills to expand ventral space. Thirty patients with severe free lumbar intervertebral disc herniation treated by spinal endoscopic technique from April 2019 to March 2021 were collected, including 19 males and 11 females;aged from 19 to 76 years with an average of (44.03±16.92) years old. All patients had a single segmental lesion with prolapse of the nucleus pulposus. Among them, there were 3 cases on L2,3, 3 cases on L3,4, 15 cases on L4,5, and 9 cases on L5S1. During operation, posterior bone of vertebral body and pedicle notch were removed by a drill under the endoscope to enlarge the ventral space. And the free nucleus pulposus was exposed and completely removed. The intraoperative blood loss, operation time, hospital stay and postoperative neurological complications were recorded, and Japanese Orthopaedic Association (JOA) score, Oswestry Disability Index (ODI) and visual analogue scale (VAS) were compared before operation, 2 days, 3 months and 1 year after operation, and Macnab standard was used to evaluate clinical efficacy. All operations were successful and the free nucleus pulposus was completely removed. Pain in the lower back and legs was significantly relieved on the day after operation. Two patients experienced transient pain and numbness in lower limbs after operation, and no serious nerve injury complications occurred. ODI and VAS at each time point after surgery were significantly lower than those before surgery (P<0.01), and JOA score was significantly higher than before surgery (P<0.01). The excellent and good rates of Macnab were 66.67% (20/30), 83.33% (25/30) and 90.00% (27/30) on 2 days, 3 months and 1 year after operation, respectively. For severe free lumbar intervertebral disc herniation, using of a drill under endoscope to expand the ventral space can smoothly remove the free nucleus pulposus and avoid nerve damage.

84. Does interbody fusion change ASD in the disc next to the fusion? 10 years of MRI follow-up on a randomized controlled study

<h3>BACKGROUND CONTEXT</h3> Due to the increasing number of spinal procedures performed worldwide, adjacent degenerative disease has become a new focus area. Whether adjacent segment disease is a matter of normal degenerative development in the disc over time or a result of increased stiffness and stress due to the fusion is still debated. Nowadays TLIF is the most widely used interbody fusion method. The use of interbody fusion has been claimed to reduce degenerative changes in the spared free disc over time due to better sagittal balance and restoration of the lost lumbar lordosis. <h3>PURPOSE</h3> To compare degenerative changes on MRI between PLF and TLIF 10 years postsurgery in an RCT cohort. <h3>STUDY DESIGN/SETTING</h3> Randomized clinical trial (RCT). Long-term follow-up. <h3>PATIENT SAMPLE</h3> Out of a primary cohort of 100 patients included in a prospective RCT between inter-body fusion and instrumented posterolateral fusion, 79 were available for follow-up 10 years after inclusion in the RCT. Patients were seen in the outpatient clinic and offered MRI at long-term follow-up. <h3>OUTCOME MEASURES</h3> Changes over time in Modic, Pfirmann, Schizas, and Fardon and Milette. <h3>METHODS</h3> All MRI were classified according to degree of Modic changes, Pfirmann classification, Schizas classification, and Fardon and Milette classification in order to show the degree of degeneration of the discs above and below the fusion. The grading was done by independent observers without any contact to the patient. In patients who underwent secondary surgery, the immediately previous MRI was used and the degenerative changes measured according to the above-mentioned classifications. <h3>RESULTS</h3> The groups were equal regarding sex, age, diagnosis and number operated levels. The follow-up was 9.6 years. The Modic change found at the first upper level was none in (85%/68%), mostly grade 2 (12%TLIF/26%PLF). There was no significant difference between the two groups p=0.274. Nearly all patients did not show any sign of treatment needs regarding spinal stenosis according to Schizas classification 92%/92%; only 8/8% had type C and D at the first proximal level 9.6 years after surgery. Interestingly, the amount of spinal stenosis grade C and D was higher at second proximal disc. No difference between groups could be detected p = 0.930 & p = 0.500. The Pfirmann grading at the first proximal level did not show any difference between groups p = 0.952. <h3>CONCLUSIONS</h3> In an RCT, the use of interbody fusion (TLIF) does not reduce the degenerative changes in the first proximal disc next to the fusion in a long-term observational study period in comparison to a normal posterolateral instrumented fusion (PLF). Thus, degenerative changes in the first proximal level are not influenced by intercorporal devices. The incidence of spinal stenosis grade C and D, 10 years after lumbar fusion surgery are 8% at first proximal disc, 13 % at second proximal disc and 8% at first distal level. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

Free Surface Double Actuator Disc Theory and Double Multiple Streamtube model for in-stream Darrieus hydrokinetic turbines

According to the literature, the last improvement to the Actuator Disc Theory for hydrokinetic turbines in channel flows included blockage ratio and Froude number as independent variables in a single-disc formulation. The authors attempted to solve these equations in a Blade Element Momentum model for axial-flow turbines, ensuring satisfactory results.To our best knowledge, no Blade Element Momentum code was developed for Darrieus rotors including an extended double-disc theory so far. In this perspective, a Free Surface double-disc LMADT is implemented to solve the governing equations in a Double Multiple Streamtube model, facilitating the assessment of In-Stream Darrieus hydrokinetic turbines. Rigid Lid equations, derived for higher-depth applications, are included for completeness. A further numerical procedure allows to set up the channel flow from downstream and update the inflow data due to the resistance induced by the turbine operation in a subcritical flow.In addition to corrections for flow curvature, shading of the downstream flow due to the shaft, and losses due to the mechanical struts, this work encloses an effective sub-model accounting for the turbine installation depth. The Double Multiple Streamtube model is finally validated with previous experimental data of a Darrieus turbine deployed in a narrow channel.

Comprehensive evaluations of heat transfer performance with conjugate heat dissipation effect in high-speed rotating free-disk system of aero-engines

Thermal boundary conditions of the turbine disk cavity system are of great importance in the design of secondary air systems in aero-engines. This study aims to investigate the complex heat transfer mechanisms of a rotating turbine disk under high-speed conditions. A high-speed rotating free-disk model with Dorfman empirical solutions is developed to evaluate the heat transfer performance considering various factors. Specifically, the influence of compressibility, variable properties, and heat dissipation is determined using theoretical and numerical analyses. In particular, a novel combined solution method is proposed to simplify the complex heat transfer problem. The results indicate that the heat transfer performance of a free disk is primarily influenced by the rotating Mach number, rotating Reynolds number, Rossby number, and wall temperature ratio. The heat transfer temperature and Nusselt number of the free disk are strongly correlated with the rotating Mach number and rotating Reynolds number. Analysis reveals that heat dissipation is a critical factor affecting the accurate evaluation of the heat transfer performance of the turbine disk. Thus, the combined solution method can serve as a reference for future investigations of flow and heat transfer in high-speed rotating turbine disk cavity systems in aero-engines.

The Role of Bending Films in the Lowest Instrumented Vertebra Selection in Adolescent Idiopathic Scoliosis Lenke Type 1A,B Based on Asymmetrical Disc Loading and Decompensation

Patients with severe adolescent idiopathic scoliosis (AIS) require instrumented spinal fusion surgery. The range of instrumented vertebra is still questioned, especially the selection of the lowest instrumented vertebra (LIV). This single institution retrospective consecutive study is to provide real-world data on outcomes. The study aims to assess whether bending films can determine the LIV. The method of determination of the lower tilted vertebra (LTV) is presented. The selection of the LTV was identified on standing PA (LTVs) and on bending X-rays (LTVb). Group A is a reference group, with less flexible curves. Groups B and C contained patients with more flexible curves. Group B covered patients with instrumentation ending at the LTVs and group C with shorter instrumentation ending at LTVb. The disc angle below the LIV was monitored for postoperative decompensation. Sixty-eight subjects with AIS Lenke 1A and 1B types underwent selective fusion. The decompensation criteria of the unfused disc below the fusion were determined as a wedging disk of &gt;5° of the Cobb angle. The patients were monitored during the postoperative period with 5.8 years average followup (minimum of 2 years). The rate of decompensation was comparable in groups A and B (31% and 33%, respectively). In contrast, the rate of decompensation was doubled in group C (60%). Caudal fusion shortening in more flexible curves according to bending films is associated with the first free disc asymmetry, which leads to decompensation below the fusion. This method should be considered in addition to other LIV selection criteria.

Black hole spin measurements based on a thin disc model with finite thickness – I. An example study of MCG−06-30-15

ABSTRACT We present a re-analysis of the XMM–Newton and NuSTAR observing campaigns for the well-studied, X-ray-bright AGN MCG−06-30-15. In particular, we consider a disc model with finite thickness. By fitting the disc reflection spectra in the data, we obtain a black hole spin of 0.87–0.99 (90 per cent confidence range) after taking the thickness of the disc into consideration. Spectral models with a grid of mass accretion rate from 0 to $30{{\,\rm per\,cent}}\,\dot{M}_{\rm Edd}$ are calculated for MCG−06-30-15. This result is obtained by considering a free disc reflection fraction parameter frefl and is consistent with previous measurements based on razor-thin disc models. Besides, an isotropic, point-like geometry, i.e. the ‘lamppost’ geometry, is assumed for the corona in our model. We find that such a geometry overestimates frefl in the data. Therefore, thin disc models with consistent ‘lamppost’ values of frefl provide a worse fit than ones with a free frefl parameter. We discuss possible reasons for the discrepancy between the observed and theoretical values of frefl at the end of the paper. Modifications for the over-simplified lamppost model might be needed when the thickness of the thin disc is considered in future work.

A low-cost spectrometer to analyse the purity of honey

Light spectrum dispersion is an exciting subjectin science because of its beautiful atmospheric colour phenomenon which attracts students. However, to see the phenomenon is not easy since it needs a spectrometer, which is commonly expensive. Therefore, the present study aims to describe a low-cost spectrometer for investigating lighting spectrum and analysing the purity of honey as a pedagogical students’ project. The spectrometer was constructed from a webcam connected to a laptop, a free spectrometer software, DVD disk, and black cardboard. The calibration of the developed spectrometer used an Argon (Ar) lamp. Afterwards, measurement tests were carried out by using Neon (Ne) and Xenon (Xe) lamps. A white light-emitting diode was used as a light source to measure several types of honey wavelengths. The results from the experiment show that the wavelength of Ar, Ne, and Xe are (503 ± 4) nm, (463 ± 3) nm, and (451 ± 3) nm respectively. The measurement accuracy of the spectrometer is 99.5%. In addition, the commercial honey characterisations show that pure honey tends to have an excellent and smooth spectrum with one peak. On the contrary, the adulteries honeys show a rough wave with many peaks representing the inhomogeneous ingredients. It is found that the average accuracy for honey spectrum is 99.8%. Moreover, the low-cost spectrometer can be built and used easily by students for educational purposes.

Many-Objective Quantum-Inspired Particle Swarm Optimization Algorithm for Placement of Virtual Machines in Smart Computing Cloud.

Particle swarm optimization algorithm (PSO) is an effective metaheuristic that can determine Pareto-optimal solutions. We propose an extended PSO by introducing quantum gates in order to ensure the diversity of particle populations that are looking for efficient alternatives. The quality of solutions was verified in the issue of assignment of resources in the computing cloud to improve the live migration of virtual machines. We consider the multi-criteria optimization problem of deep learning-based models embedded into virtual machines. Computing clouds with deep learning agents can support several areas of education, smart city or economy. Because deep learning agents require lots of computer resources, seven criteria are studied such as electric power of hosts, reliability of cloud, CPU workload of the bottleneck host, communication capacity of the critical node, a free RAM capacity of the most loaded memory, a free disc memory capacity of the most busy storage, and overall computer costs. Quantum gates modify an accepted position for the current location of a particle. To verify the above concept, various simulations have been carried out on the laboratory cloud based on the OpenStack platform. Numerical experiments have confirmed that multi-objective quantum-inspired particle swarm optimization algorithm provides better solutions than the other metaheuristics.