bluuebunny/crossref_metadata_2025 huggingface dataset:
The Microchemical Analysis of Rubber
Authors: Wyatt G. H.
Published: February 2011

While those who profess to be microchemists have a number of specialized techniques, it is surprising how often microchemistry is used without appreciation that this is being done. As examples in the analysis of rubber, two qualitative color tests may be mentioned that are both applicable to small samples. The first was described by Weber in 1900, but interest in it has been revised recently by Stern and by Parker and Wake. In this test the rubber is treated with bromine and then with phenol; natural rubber gives a violet color and so may be distinguished from synthetic elastomers. In the second test, due to Kirchhof, natural rubber is detected by the yellow-to-red color which it gives with trichloroacetic acid. Other reactions carried out with small quantities of rubber for identification purposes include the well known Beilstein test for halogens, in which the organic substance when heated on a copper wire imparts a green color to a Bunsen flame. This method was suggested by Newton for the detection of chloroprenes, and has been applied by Shaw in a systematic procedure for the identification of plastics in general. Spot tests have also been devised that depend on the reactions of the vapors produced by destructive distillation of the rubber being examined; for example, Neoprene gives vapors which bleach paper impregnated with potassium chromate, or the density and pH value of the distillate may be determined. The rates of reaction of natural rubber and various synthetic elastomers with mixed nitric and sulfuric acids has been shown to be characteristic and may be determined with small samples. In contrast with the above, some procedures have been called micromethods by their advocates merely because the samples used are smaller than usual. Microchemistry was clearly defined by Emich as covering the range 2 to 10 mg. of substance, and the present author's work described below should properly be termed semimicroanalysis.
Relation between Stress Relaxation and Aging Resistance of Rubber Vulcanizates. II. Effect of Copper in Various Accelerated Stocks
Authors: Pedersen H. Leth
Published: February 2011

As was shown in a previous paper, a definite relation exists between aging and relaxation rates for rubber vulcanizates. Gee has shown that the modulus of stocks with the same “compound” viscosity determines the average molecular weight between bonded units. We shall, therefore, expect to find a constant sulfur-bond distribution in related vulcanizates with the same niveau of moduli and Mooney plasticity and, hence, the same free energy for the process of oxidation. If various retarding agents such as antioxidants are added, measurement of the rate of relaxation of the stress at constant elongation will conform with the rate of aging expressed in terms of tensile strengths. For vulcanizates with the same system of accelerators but containing different fillers, the moduli will vary widely, and interpretation of the stress relaxation measurements (abbrev. SR) will become difficult. The same will hold for systems with boosted accelerator complexes. Plain accelerator/sulfur stocks seem, on the contrary, to give approximately the same range of stability whether tested in aging or relaxation. Thus the merit of the relaxation method is the rapid evaluation of the catalytic effect of compounds which does not interfere with the state of cure. By a proper choice of the temperature, the SR measurement can be completed in minutes, and it is possible to select the active compounds for the more tedious control in aging. Especially for work with the antioxidant effect in thiuram vulcanizates without addition of sulfur where the shelf aging in air at 95° C lasts for 50–60 days, the use of the stress relaxations measurement at temperatures of 130–150° C represents a very convenient method of information. The copper effect described in the following was actually stated with the SR method. Since the method easily might be conducted half or fully automatically, it is very suited for research work or even for control.
Abrasion of Automotive Tires
Authors: Kern Walter
Published: February 2011

This paper is intended to show that tire engineering is not concerned merely with improvement of quality, but also is concerned, on the part of engineers, with information on the friction phenomena in the boundary layer between the tire tread and the road surface. For a tire to have good abrasion properties, the resistance of the tread should be high and the work of friction should be as low as possible. Methods for measuring the work of friction are described, with some examples of influences which have control over it. While at the present stage of progress in technical developments, improvement of the resistance to abrasion of tire treads and in the design of treads is limited to small percentages, external conditions in service may increase the work of friction several fold. This accounts for common wide differences in the life of similar tires on the road. It is hoped that this paper may lead to further cooperative research on phenomena at the boundary surface between the surface of a tire and of the road. Such studies would be in the interest of the rubber industry, the automotive industry, and the consumer.
A Study of Electrostatic Charge Conditions in Automobile Tires
Authors: Giese O. , Stein H. , Lauer F. J.
Published: February 2011

If the test results for the various systems considered are interpreted with respect to the generation of flexure voltages, the following generalization can be made. A flexure voltage is produced in the case of opposite polarity between casing and tube. This is true unless stationary charges on the tread surface prevent generation of the potential. Another result of interpretation of Table 1 is the statement that the following voltage observations are to be regarded as determining the character of a tire system: (see PDF for table) It is believed that the foregoing has shown that there is reason to regard tires as a self-contained unit, as a system, with respect to their static behavior. The results plainly illustrate the interaction between inner tube and casing. A merit factor for the rating of tire systems has accordingly been derived, to take adequate account of practical considerations. This merit factor is taken as the sum of the voltages for the characteristic terms as enumerated above, namely : GZ=AP/E+AD/AS+AP/AD/E+AS/AD/E+AD/AS/E The resulting merit factors GZ have been assembled in Table 3. Summarizing, it may be said that, for a satisfactory solution of the problem of static charges on vehicles according to the experimental results reported, the following conditions should be met. The tire system should not generate any high tread-voltages and no flexure voltages should be generated. Both conditions are satisfied by the use of conductive inner tubes. Conductive inner tubes, in all cases tested, reduced flexure voltage to zero and the tread potential to such an extent that no undesirable effects could arise.
Chain-Length Distribution Functions of Polymers after Random Degradation and Cross-Linking, with Particular Reference to Elastomers
Authors: Watson W. F.
Published: February 2011

The distribution of chain lengths of polymers on formation, random degradation and random cross-linking, have been derived by a simple statistical treatment. Chain-length distribution functions for all cases are represented by special forms of the expression : Nx/N=(α+β+γ)exp[−(α+β+γ)x] where β is the reciprocal of the average chain length on polymer formation, α is the degree of random degradation, and γ is the degree of cross-linking.
The Structure of Neoprene. VI. Crystallization
Authors: Maynard J. T. , Mochel W. E.
Published: February 2011

This study of the crystalization behavior of chloroprene polymers has shown for the first time that the melting point of the crystalline phase of these polymers is an inverse linear function of the polymerization temperature. This relationship causes the previously unaccounted for decreased rate and degree of crystallization in polychloroprenes prepared at higher temperatures, and presumably is the reason for the similar behavior of polybutadienes. The melting point of crystalline polychloroprene is depressed by the introduction of monomeric diluents, as well as by the introduction of irregularities in the polymer chain by copolymerization with other monomers. It is very likely, therefore, that the lowering of the melting point in polychloroprenes by raising polymerization temperatures is the result of introducing an increasing proportion of structural irregularities by modes of polymerization other than trans-1,4. The branched units resulting from 1,2- and 3,4-polymerization may make a significant contribution, although ozonolysis has indicated that 40° C Neoprenes do not contain more than about 5 per cent of such branched structures. It is likely that 1,4-units in the cis-configuration are most important, and calculations based on the observed melting-point depressions in polychloroprenes suggest that, in 40° C polychloroprenes, cis-l,4-units could account for another 10–15 per cent irregularities. The question of the occurrence of head-to-head, tail-to-tail polymerization remains moot, although this is unlikely to be an important factor because of the polar nature of the chloroprene molecule. Regardless of these questions, it has been clearly demonstrated that Neoprenes have the most regular structure of any diene polymer so far characterized. Information about the degree of crystallization of polychloroprenes gained from dilatometric measurements has made it possible to calibrate the crystallization sensitive bands which appear in infrared absorption spectra, and these bands can now be used for rapid determination of the degree of crystallinity of Neoprene films. The heat of fusion of the crystalline phase of polychloroprenes has been determined. Copolymer data give the value 15.3 calories per gram, and diluent data indicate the value to be 22.7 ± 2 calories per gram. The latter value is probably the more reliable. It has been found that variations of molecular weight and degree of cross-linking have no apparent effect on the rate of crystallization of polychloroprenes made at a given temperature.
The Proton Magnetic Resonance in Natural Rubber
Authors: Gutowsky H. S. , Meyers L. H.
Published: February 2011

The proton magnetic resonance has been observed in natural rubber from liquid nitrogen temperature to room temperature. The absorption line widths show two regions of change. With rising temperature, the first change in width starts at about 155° K, and we assign it to the onset of CH3 group rotation. The second, larger change to a narrow line, starts at about 225° K and is assigned to the onset of segmental motions. The latter change coincides with the second-order transitions observed in various physical properties and provides a direct confirmation of the cause of the transition. Samples cured 30, 60, and 90 minutes were investigated, and it was found that curing has a larger effect on the line width changes at lower temperature than at higher temperature. The inferred greater effect of curing on CH3 group motions than on segmental motions suggests that cross-linking is not the primary mechanism of vulcanization. Rubber stretched 70 per cent was found to have the same resonance absorption as unstretched samples.
Phosphatides of Hevea Latex
Authors: Smith R. H.
Published: February 2011

Phosphatides, together with other lipin substances, were extracted from fresh latex in the form believed to be that in which they naturally occur. Analysis, after removal of water-soluble impurities, gave evidence that the total lipin contained approximately 51 per cent lecithin, 10.5 per cent inositol phosphatide, 3 per cent phosphatidyl ethanolamine, 20 per cent triglycerides and 15.5 per cent unsaponifiables. An enzyme was found to be present in latex, which is capable of liberating choline from the lecithin component after coagulation by adding to alcohol below 40° C, by adding to formic acid, or by freezing, but inactive in untreated latex. The enzyme was destroyed slowly on storing fresh latex and rapidly on adding ammonia or formaldehyde. The implications of these findings on the properties of commercially prepared rubber are discussed. Destruction of the phosphatide during storage of some untreated latexes was observed, but the effect was insufficiently consistent to account for the universal property of spontaneous coagulation.
The Plasticization of Rubber on Roll Mills
Authors: Stalinsky Eugene
Published: February 2011

Consider two mills with rolls of the same diameter, and assume that the rolls rotate n and n′, respectively, turns per minute, between 12 and 30. Let t and t′ be the times in minutes necessary to bring the same standard amount of rubber to the same degree of plasticity on each mill. It can be shown experimentally that the times t and t′, expressed in minutes, are related in the following way:
Possibilities in the Use of Sodium Chlorite in Latex
Authors: Tournier Josette
Published: February 2011

The oxidation of rubber by sodium chlorite can be accomplished either with rubber in the solid form or with rubber in aqueous suspension. The first process gives highly oxidized and very sticky rubbers. By the second process, the oxidation can be controlled so that all the sodium chlorite is decomposed in the latex, i.e., before coagulation and drying. The decomposition reaction is carried out either in neutral medium in the presence of an activator of decomposition of the sodium chlorite, e.g., formaldehyde, or in an acid medium with pH between 3 and 4. The oxidation process, which requires only small percentages of sodium chlorite, can be adapted to the manufacture of adhesive from latex and the preparation of rubbers plasticized directly without mastication. These degraded latexes react easily with various reactive agents of normal rubber, in particular with halogens.
Rubber Hydrocarbon in Freshly Tapped Latex
Authors: Bloomfield G. F.
Published: February 2011

Investigations carried out in Malaya have shown that rubber hydrocarbon in fresh latex is already a high molecular material but of considerable heterogeneity. Latex is separable into non-rubber constituents and rubber hydrocarbon, which is itself separable into microgel, soluble fractions covering a wide range of molecular weight, and low-molecular oxygenated fractions. The molecular weight distribution of the soluble hydrocarbon material is weighted heavily in the higher molecular weight range of half million to five million, with an average around one million. Coagulated rubber contains macrogel in addition to the microgel component of the latex. The microgel component of latex hydrocarbon has been used as a “marker” to indicate from what regions of a tree rubber is withdrawn on tapping.
Dispersion of Fillers in Rubber
Authors: Ecker Ruprecht
Published: February 2011

The activity of a filler in rubber depends on the size and geometrical shape of the particles, and on their chemical constitution. The smaller a particle is, the larger is the total surface area of the filler per unit weight. If, for example, the diameter of a particle of an active carbon black is 30 mµ, the total surface area is about 100 sq. m. per gram. If the particle diverges from spherical shape and has a crystalline form, the surface area is greater, as the relation of the area of a sphere to that of a cube of equal volume clearly shows (surface area of sphere: surface area of cube = 12.5:15.6). Furthermore, corners and edges are present on a particle of crystalline shape, which are particularly active according to the experimental results of interface physics. By means of this phenomenon, the differing activity of various fillers of equal particle diameter can be explained.
Polymerization Phenomena in the Vulcanization Process
Authors: Dogadkin B. , Feldstein M. , Dobromyslova A. , Shkurina V. , Kalpunov M.
Published: February 2011

According to theories developed by the authors, vulcanization consists essentially in the formation of local chemical van der Waals bonds (polarization, orientation bonds) and hydrogen bonds between the molecular chains of rubber. These bonds are formed as a result of the chemical reaction of the rubber with the vulcanizing agent, oxygen, and accelerators, and with other components of the vulcanizing system which contain functional groups. The essential type of chemical bonds consists of atomic groups of the vulcanizing agent (in the case of sulfur vulcanizates, “bridge” sulfur). Hypotheses were advanced concerning the course during vulcanization of the polymerization processes, initiated by the free radicals which are formed by the vulcanizing agent, and leading to the formation of —C — C—bonds between the molecular chains of the rubber. However, no proof of the existence of such processes has been obtained ; furthermore, certain data, for example, data obtained by spectral analysis, contradict such an assumption. The present paper is devoted to a description of experiments which show the existence of polymerization processes involving free radicals in vulcanized systems which contain accelerators of the disulfide and sulfenamide type.
Effect of the Molecular Weight of Rubber on the Kinetics of Vulcanization and on the Formation of a Spatial Network
Authors: Novikov A. S. , Bartenev G. M. , Galil-Ogly F. A.
Published: February 2011

From scientific literature it is known that the rate of vulcanization and the mechanical properties of rubbers depend on the value of the initial molecular weight of the rubber. However, the cause of the slow vulcanization of olw molecular rubbers and the effect of the molecular weight of the rubber on the formation of a spatial network and the structure of the vulcanizate remain unclear. In the present work the kinetics of vulcanization of separate fractions of butadiene rubber SKS-30A of molecular weight from 100,000 to 1,170,000 was studied by measurements of the equilibrium modulus and the proportion of combined sulfur. The SKS-30A rubber was divided into five fractions of molecular weights: I 1,170,000; II 700,000; III 500,000; IV 140,000; and V 100,000. The molecular weights were calculated from viscometric data according to the formula previously established for this rubber by the authors: [η]=2.96×10−4 M0.71. In order to keep the molecular weight of the rubber constant, sheets for vulcanization were prepared from a dispersion of the ingredients in a benzene-rubber solution. The composition of the mixture was the same for all the fractions, i.e., 100 parts by weight of rubber, 3 parts of sulfur, 1 part of mercapto-benzothiazole, 5 parts of zinc oxide, 2 parts of stearic acid, and 1 part of phenyl-β-naphthylamine. The sheets were vulcanized in a hydraulic press at 143° C for various periods. The amount of sulfur combined with the rubber was determined by Bolotnikov's method, specially adapted to small batches of vulcanizate. The rubber specimens, weighing 0.2–0.3 gram, were extracted in 50 cc. of sodium sulfide, and titrated with 0.01N iodine solution.
Dependence of the Fundamental Properties of Unvulcanized and Vulcanized Butadiene-Styrene Rubber Mixtures on the Initial Molecular Weight
Authors: Novikov A. S. , Khaikina M. B. , Dorokhina T. V. , Arkhangelskaya M. I.
Published: February 2011

1. The relation of the basic properties of unvulcanized and vulcanized SKS-30A rubber-carbon black mixtures to the initial molecular weight of the rubber was studied. 2. Fractions having molecular weights up to 300,000 possess the best technical properties in their behavior during mill mixing. However, the best dispersion of carbon black is found in the still higher molecular fractions. 3. In the mill mixing of rubber with carbon black, it is principally the highest molecular fractions of the rubber which become bound, with the formation of an insoluble carbon black-rubber gel. It is shown that the thermoplastic properties of rubber-carbon black mixtures depend basically on the molecular weight and, probably, on the structure and quantity of carbon black-rubber gel formed. 4. The basic properties of vulcanizates, viz., tensile strength, relative elongation, heat resistance, and resistance to repeated deformations increase with increase of the molecular weight up to 300,000, but change little with further increase of the molecular weight. 5. The greatest reduction of the properties of vulcanizates is observed at a molecular weight of 80,000 and lower. Addition of a low-molecular fraction to a high-molecular fraction in the proportion of 1:1 greatly decreases the tensile strength and resistance to repeated deformation. 6. The range of molecular weights from 100,000 to 300,000 is, for SKS-30A rubber, the most satisfactory from the viewpoint of obtaining, throughout this range, satisfactory technical properties of mixtures before vulcanization and physical and mechanical properties after vulcanization. 7. The relation which has been established of the basic properties of a vulcanizate to its molecular weight is explained: (1) by the formation of a more regularly constructed network in a vulcanizate of the high-molecular fractions of rubber, which is distinguished from that of the low-molecular fractions by a smaller number of terminal groups not entering into the chain ; and (2) by the different nature of the reaction between carbon black and the high-molecular fractions, resulting in the latter case in a higher value of the energy of inter-molecular reaction.
The Microstructure of Diene Polymers. II. Polyisoprenes and Polybutadienes Prepared at High Pressures
Authors: Richardson W. S.
Published: February 2011

The rapid bulk polymerization of isoprene at room temperature under high hydrostatic pressure was apparently first observed by Bridgman and Conant. A more extensive investigation by Conant and Tongberg established the free radical nature of the polymerization (peroxide catalysis and hydroquinone inhibition). The latter workers also noted the solubility and elasticity of polymers made to moderate conversion and the insoluble crumbly nature (gelation) of the polymers made to very high conversion. In view of the well known effect of increased pressure in driving chemical reactions in the direction of the products of least specific volume, it is of interest to consider the possibility that diene polymers made at high pressures may be different in microstructure from polymers made at comparable temperatures but near atmospheric pressure.
The Effect of Masterbatching, Compounding, and Testing Variables on Constant-Slip Abrasion Results
Authors: Howland L. H. , White W. W. , Messer W. E.
Published: February 2011

A study of factors which affect the results obtained with the constant slip abrader in evaluation of abrasion resistance properties of GR-S vulcanizates has revealed the following : 1. As might be expected, abrasion losses decrease with increase in 300 per cent modulus. 2. Losses increase approximately logarithmically as the amount of slip between the test and abrasive wheels increases. 3. The abrasion losses decrease with increase in talcing rate, due to “lubrication” of the abrasive wheel by the talc as long as the rate is sufficient to keep the wheel free of loose abraded material. 4. Indications are that abrasion losses may increase with increase of coefficients of friction of test wheels against the abrasion wheel. 5. In a study of the effect of ambient temperature on constant slip abrasion losses, the losses increased as the temperature was raised from −10 to 30° C for GR-S 1500, GR-S 1503, and for high Mooney-viscosity GR-S 1500 extended with a naphthenic extender oil, and the losses remained essentially constant for the Resin-731 extended high Mooney viscosity GR-S 1500. The Resin-731 extended stock changed only slightly with temperature and, consequently, its comparative rating increased rapidly with rise of temperature. It was noted in photomicrographs of the wheel surfaces that the abrasion pattern which was evident at normal temperatures was absent or at best poorly defined at the lower temperatures, indicating a possible difference in kind of abrasion at low temperatures than at normal temperatures. 6. Latex masterbatches of oil and black that had been premixed by several different methods gave vulcanizates with constant-slip abrasion resistance superior to similar masterbatches prepared in the usual manner. 7. The constant-slip abrader was found to be useful in evaluating new SAF blacks and in the evaluation of the effect of using dispersing agents in carbon black and extender-carbon black masterbatching by the latex procedure.
Air Permeability of Elastomers by Diffusion Tests
Authors: Czuha M.
Published: February 2011

The permeability of various tread compounds to air was measured in a modified Warburg diffusion apparatus. Measurements were made at 30° C, with air applied at 48 psi. pressure, on molded disks approximately 0.025 inch thick and an area of 12.57 sq. in. The tests were reproducible within 4 per cent on control specimens. The compounds investigated showed permeabilities intermediate between the low values for Butyl and the high values for natural rubber. The permeability decreased with increasing combined styrene contents and with a decrease of temperature of polymerization for polybutadiene and low-styrene copolymers. It was unaffected by variation over a large range in polymer Mooney viscosity, gel content, and dilute-solution viscosity. A slight and almost linear decrease of permeability was found with increases in time of cure and carbon black loading for the stocks. In terms of the 300 per cent modulus, an increase of 100 psi. was accompanied by a 2 per cent decrease in permeability. Processing oil in the polymer had only a slight effect on permeability, when compared to the effects of compositional and structural modifications. Alfin and sodium, 75/25 BD/S, copolymers showed the lowest air permeability of the tread type of compounds that were studied.
The Role of Molecular Forces in the Mechanism of Swelling of High Polymers. II. Kinetics of Swelling
Authors: Gul V. E.
Published: February 2011

1. The rate of swelling of high-molecular compounds is a function of the chemical nature and geometric structure of the components of the mixture. 2. In an investigation of the molecular mechanism of swelling of high polymers having highly developed spatial structures, theoretical variations of the rate of swelling with the degree of swelling and molecular characteristics of the components of the mixture were derived for cases where the limiting rate is that of three-dimensional deformation of the specimen in the swelling process, and for the case where the slowest process is the diffusion penetration of the solvent. 3. It is shown that, in both the above-mentioned cases, the rate of swelling depends essentially on the values of the specific cohesion energies of the components of the mixture.
Approximation Formula for Easy Calculation of Signal-to-Noise Ratio of Sigma-Delta Modulators
Authors: Mladenov Valeri , Karampelas Panagiotis , Tsenov Georgi , Vita Vassiliki
Published: February 2011

The signal-to-noise ratio (SNR) is one of the most significant measures of performance of the sigma-delta modulators. An approximate formula for calculation of signal-to-noise ratio of an arbitrary sigma-delta modulator (SDM) has been proposed. Our approach for signal-to-noise ratio computation does not require modulator modeling and simulation. The proposed formula is compared with SNR calculations based on output bitstream obtained by simulations, and the reasons for small discrepancies are explained. The proposed approach is suitable for fast and precise signal-to-noise ratio computation. It is very useful in the modulator design stage, where multiple performance estimates are required.
Characteristics of Patients With Cancer and COVID-19 Who Discontinued Cancer Treatment
Authors: Islam Jessica Y. , Hathaway Cassandra A. , Hume Emma , Turner Kea , Hallanger-Johnson Julie , Tworoger Shelley S. , Camacho-Rivera Marlene
Published: May 2024

This cross-sectional study evaluates the prevalence of and characteristics associated with discontinuation of cancer treatment among patients who received a diagnosis of COVID-19 during their treatment planning.
Effect of Low-Dose Aspirin on the Course of Age-Related Macular Degeneration
Authors: Robman Liubov D. , Wolfe Rory , Woods Robyn L. , Thao Le Thi Phuong , Makeyeva Galina A. , Hodgson Lauren A. B. , Lepham Y-Anh , Jachno Kim , Phung James , Maguire Emily , Luong Henry , Trevaks Ruth E. , Ward Stephanie A. , Fitzgerald Sharyn M. , Orchard Suzanne G. , Lacaze Paul , Storey Elsdon , Abhayaratna Walter P. , Nelson Mark R. , Guymer Robyn H. , McNeil John J.
Published: May 2024

Importance

Age-related macular degeneration (AMD) is the leading cause of irreversible vision loss in old age. There is no proven intervention to prevent AMD and, apart from lifestyle, nutritional, and supplement advice, there is no intervention to delay its progression.

Objective

To determine the impact of long-term low-dose aspirin on the incidence and progression of AMD.

Design, Setting and Participants

The Aspirin in Reducing Events in the Elderly–AMD (ASPREE-AMD) study was an Australian-based substudy of the ASPREE trial, a multicenter, international, randomized, double-masked, placebo-clinical trial investigating the efficacy of low-dose aspirin in prolonging disability-free survival among older individuals. Retinal photography was conducted at baseline from March 2010 to January 2015, then 3 and 5 years after randomization. AMD status was determined using color retinal images and treatment records. Australian participants in ASPREE aged 70 years and older without dementia, independence-limiting physical disability, cardiovascular disease, or chronic illness limiting 5-year survival and with gradable retinal images at baseline were included. Data were analyzed from December 2022 to December 2023.

Interventions

Aspirin (100 mg daily, enteric coated) or placebo.

Main Outcomes and Measures

Incidence of AMD and progression from early/intermediate to late AMD. Outcomes were analyzed by modified intention-to-treat analysis.

Results

A total of 4993 participants were enrolled in this substudy. Baseline characteristics were similar between groups. At the time of sponsor-determined trial termination, retinal follow-up data were available for 3208 participants, 3171 of whom were analyzed for AMD incidence and progression, with a median (IQR) age of 73.5 (71.5-76.4) years and even sex distribution (1619 [51%] female). Median (IQR) follow-up time was 3.1 (3.0-3.5) years. Cumulative AMD incidence was 195 of 1004 (19.4%) in the aspirin group and 187 of 979 (19.1%) in the placebo group (relative risk [RR], 1.02; 95% CI, 0.85-1.22; P = .86). Cumulative progression from early/intermediate AMD to late AMD was observed in 14 of 615 (2.3%) participants in the aspirin group and 18 of 573 (3.1%) in the placebo group (RR, 0.72; 95% CI, 0.36-1.44; P = .36).

Conclusions and Relevance

In this trial, low-dose aspirin administered for 3 years did not affect the incidence of AMD. The evidence was weaker for progression of AMD due to low number of progressed cases. Overall, these results do not support suggestion that low-dose daily aspirin prevents the development or progression of AMD.

Trial Registration

anzctr.org Identifier: ACTRN12613000755730
Accuracy of Salivary Circulating Tumor Human Papillomavirus DNA in Detecting Oropharyngeal Cancer
Authors: Lakshmipathy Deepak , Prasad Aman , Fritz Christian G. , Go Beatrice C. , Rajasekaran Karthik
Published: May 2024

Importance

Circulating tumor human papillomavirus DNA (ctHPV DNA) has shown potential as a biomarker capable of improving outcomes in patients with HPV-related oropharyngeal (OP) cancer. It can be isolated from plasma or saliva, with the latter offering reduced invasiveness and theoretic reduction of lead time.

Objective

To perform a systematic review and meta-analysis on the accuracy of salivary ctHPV DNA for detecting HPV-associated OP cancer.

Data Sources

Cochrane Library, Embase, PubMed, and Web of Science databases were searched from inception through October 2023.

Study Selection

All patients who underwent salivary ctHPV DNA testing at presentation for possible or diagnosed HPV-related OP cancer were included. Non-English and review publications were excluded. Two authors independently voted on article inclusion with a third resolving conflicting votes.

Data Extraction and Synthesis

Following Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) reporting guidelines, multiple authors independently abstracted data and assessed bias of included articles. Bivariate random-effects meta-analysis was performed with I2 to assess for study heterogeneity.

Main Outcomes and Measures

Sensitivities, specificities, positive likelihood ratios (PLR), negative likelihood ratios (NLR), and diagnostic odds ratios (DOR) with 95% CIs alongside area under the curve (AUC) of a summary receiver operating characteristic (SROC) curve were calculated. The initial analysis took place throughout December 2023.

Results

Of 440 initially identified articles, 6 met inclusion criteria and demonstrated moderate heterogeneity (I2 = 36%) with low risk of bias and low applicability concerns. Overall, 263 total patients were included with a median (range) age of 58 (39-86) years, and 228 (87%) were male patients. Per updated prognostic staging criteria, localized tumors (ie, stages 1 or 2) comprised most cancers at 139 (77%), whereas advanced ones (ie, stages 3 or 4) comprised the remaining 41 (23%). Pooled sensitivity, specificity, PLR, NLR, and DOR values were 64% (95% CI, 36%-85%), 89% (95% CI, 46%-99%), 11.70 (95% CI, 0.37-77.00), 1.21 (95% CI, 0.08-7.00), and 139.00 (95% CI, 0.05-837.00), respectively. The AUC of the SROC curve was 0.80.

Conclusions and Relevance

This study supports salivary ctHPV DNA as an acceptably specific test in detecting HPV-associated OP cancer that would benefit from testing in clinical trials prior to real-time implementation.
Relative cost of ginning cotton using saw, conventional roller, and high‐speed roller gins in the United States
Authors: Acharya Ram N. , Sapkota Sushil C. , Bhandari Pratima , Armijo Carlos , Whitelock Derek
Published: May 2024

The primary objective of this study was to investigate whether the cost of processing cotton using high‐speed roller gins is comparable to saw gins. The results from a “true” random effect model estimated using proprietary data voluntarily shared by cotton gins operating in Arizona and California showed that the average cost inefficiency for the sample gins analyzed in this study was 13.5%. Moreover, the cost of ginning using conventional roller gins and high‐speed roller gins was 24.42% and 14.18% higher than saw gins, respectively, and roller ginning costs were 10% lower for high‐speed roller gins than conventional roller gins. [EconLit Citations: D24; O14; Q16].
Anomalous Structural Transformation of Cu(I) Clusters into Multifunctional CuAg Nanoclusters
Authors: Yao Yuqing , Hao Wei , Tang Jin , Kirschbaum Kristin , Gianopoulos Christopher G. , Ren An , Ma Liang , Zheng Letian , Li Hanying , Li Qi
Published: May 2024

We report an anomalous structural transformation of a Cu(I) cluster into two different types of copper‐silver (CuAg) alloy nanoclusters. Different from previous reports, we demonstrate that under specifically designed reaction conditions, the Ag‐doping could induce a substantial growth of the starting Cu15 and a Ag13Cu20 nanocluster was obtained via the unexpected insertion of an Ag13 kernel inside the Cu(I)‐S shell. Ag13Cu20 demonstrates high activity to initiate the photopolymerization of previously hard‐to‐print inorganic polymers in 3D laser microprinting. Interestingly, a slight modification of the reaction condition leads to the formation of another Ag18‐xCuxS (8≤x) nanocluster templated by a central S2− anion, which possesses a unique electronic structure compared to conventional template‐free CuAg nanoclusters. Overall, this work unveils the intriguing doping chemistry of Cu clusters, as well as their capability to create different types of alloy nanoclusters with previously unobtainable structures and multifunctionality.
Redox Engineering of Myoglobin by Cofactor Substitution to Enhance Cyclopropanation Reactivity
Authors: Kagawa Yoshiyuki , Oohora Koji , Himiyama Tomoki , Suzuki Akihiro , Hayashi Takashi
Published: May 2024

Design of metal cofactor ligands is essential for controlling the reactivity of metalloenzymes. We investigated a carbene transfer reaction catalyzed by myoglobins containing iron porphyrin cofactors with one and two trifluoromethyl groups at peripheral sites (FePorCF3 and FePor(CF3)2, respectively), native heme and iron porphycene (FePc). These four myoglobins show a wide range of Fe(II)/Fe(III) redox potentials in the protein of +147 mV, +87 mV, +42 mV and −198 mV vs. NHE, respectively. Myoglobin reconstituted with FePor(CF3)2 has a more positive potential, which enhances the reactivity of a carbene intermediate with alkenes, and demonstrates superior cyclopropanation of inert alkenes, such as aliphatic and internal alkenes. In contrast, engineered myoglobin reconstituted with FePc has a more negative redox potential, which accelerates the formation of the intermediate, but has low reactivity for inert alkenes. Mechanistic studies indicate that myoglobin with FePor(CF3)2 generates an undetectable active intermediate with a radical character. In contrast, this reaction catalyzed by myoglobin with FePc includes a detectable iron–carbene species with electrophilic character. This finding highlights the importance of redox‐focused design of the iron porphyrinoid cofactor in hemoproteins to tune the reactivity of the carbene transfer reaction.
The association of preoperative hematologic parameters with short‐term clinical outcomes in rectal cancer: A feature importance analysis
Authors: Orafaie Ala , Shahabi Fatemeh , Mehri Ali , Ansari Majid , Kasraeifar Sajjad , Ghiyasi Mahdie , Saberi‐Karimian Maryam , Abdollahi Abbas , Tabatabaei Seyyed Mohammad
Published: May 2024

Background

Various hematologic parameters have been proposed as prognostic factors in rectal cancer management, but data are conflicting and unclear. This study is designed to investigate the prognostic factor capability of preoperative hematologic parameters with postoperative morbidities and mortality in rectal cancer patients undergoing curative resection.

Methods

All 200 consecutive rectal cancer patients diagnosed at Ghaem University Hospital from 2017 to 2022 were retrospectively evaluated. The receiver operating characteristic (ROC) curves and machine learning (ML) algorithms of Random Forest, Recursive Feature Elimination, simulated annealing, Support Vector Machine, Decision Tree, and eXtreme Gradient Boosting were administered to investigate the role of preoperative hematologic parameters accompanied by baseline characteristics on three clinical outcomes including surgical infectious complications, recurrence, and death.

Results

The frequency of infectious complications was correlated with the surgical procedure, while tumor recurrence was significantly influenced by T stage and N stage. In terms of mortality, alongside T and N stage, the status of resection margin involvement was significantly correlated. Based on the ROC analysis, the NLR >2.69, MPV ≤9 fL, and PDW ≤10.5 fL were more classified patients to mortality status. Likewise, the PLT >220 109/L, MPV ≤9 fL, PDW ≤10.4 fL, and PLR >13.6 were correlated with recurrence. However, all factors examined in this study were not significant classifiers for the outcome of surgical infectious complications. The results of ML algorithms were also in line with ROC analysis.

Conclusion

According to the results of both ROC analysis and ML models, preoperative hematologic parameters are considerable prognostic factors of postoperative outcomes in rectal cancer patients, and are recommended to be monitored by clinicians to prevent unfavorable outcomes.
Professional wisdom in counselor education: A consensual qualitative research
Authors: Zhu Peitao , Litherland Gideon , Bell Tamekia , Luke Melissa
Published: May 2024

Emerging evidence has suggested that practitioners who demonstrate professional wisdom, a multifaceted disposition, show superior judgment and clinical efficacy. In this consensual qualitative research study, we examined 16 peer‐nominated wise counselor educators’ perspectives on professional wisdom in the context of counselor education. We identified seven domains pertaining to the characteristics and interpersonal effects of professional wisdom, as well as perceptual factors. Our findings present an initial framework of professional wisdom specific to the field of counselor education and provide implications for counselor education, counseling practice, and future research.
Algorithms and throughput analysis of cognitive radio‐based MIMO‐NOMA for the next generation of wireless communications
Authors: Saeed Ahmed Abd , Ahmed Mohamad A.
Published: May 2024

In this paper, multi‐users (MU) communications are considered based on the cognitive ratio (CR) technique. Multiple‐input multiple‐output (MIMO) and non‐orthogonal multiple access (NOMA) are proposed to be merged with CR for the sake of improving the achievable throughput and satisfying user fairness. Moreover, utilizing MIMO‐NOMA enables the CR users to be served in the coverage network without the need for spectral sensing. Three scenarios are assumed in this paper to investigate the performance of each CR secondary user (SU) in the presence of single or multiple primary users (PUs). Pairing algorithms are proposed and applied to obtain optimum throughputs and outage probabilities, in which the algorithms are employed to select a PU with an SU to be coupled in a pair, depending on allocating the required power for each user, taking into account that any PU has the priority to reach its required throughput. Moreover, mathematical expressions have been derived for each case to evaluate the required power allocation factor and the achievable throughput for each user. Furthermore, the proposed algorithms show successful and satisfactory achievable rates and outage probabilities.
AMPA and NMDA receptors in dentate gyrus mediate memory for sucrose in two port discrimination task
Authors: Sagarkar Sneha , Bhat Nagashree , Rotti Deepa , Subhedar Nishikant K.
Published: May 2024

Although the phenomenon of memory formation and recall associated with the use of psychotropic drugs has been extensively studied, mechanisms underlying memories for natural reward have not been clarified. Herein, we test the hypothesis that glutamatergic receptors in the dentate gyrus play a role in memories associated with sucrose. We used pellet self‐administration protocol to generate memories in two‐port nose‐poke discrimination task using male Wistar rats. During non‐rewarded probe trial, the conditioned animals readily discriminated the active port versus inactive port and showed massive increase in mRNA expression of AMPA receptor subunit genes (gria2, gria3) as well as c‐Fos protein in the DG. Access to sweet pellet further enhanced c‐Fos expression in the DG. However, animals pre‐treated with AMPA receptor antagonist CNQX (intra‐DG), on exposure to operant chamber (no pellet), showed decreased discrimination as well as c‐Fos expression. We suggest that AMPA receptors in DG mediate recall and consolidation of memories associated with sucrose consumption. CNQX pre‐treated animals, if presented with sweet pellet on nose poke, exhibited high discrimination index coupled with increased c‐Fos expression. In these CNQX treated rats, the DI was again decreased following administration of NMDA receptor antagonist AP5. We suggest that, although AMPA receptors are blocked, the access to sweet pellet may induce surge of glutamate in the DG, which in turn may reinstate memories via activation of erstwhile silent synapses in NMDA dependant manner.
Embedded theoretical quality option pricing in Treasury bond futures—Starting from the definition deviation of conversion factor
Authors: Yang Xiaofeng , Zhao Ling
Published: May 2024

Unlike ordinary futures, Treasury bond futures are a kind of complex financial derivatives with multiple Treasury bonds as the underlying, which can be settled on multiple dates. China's Treasury bond futures contract embeds a quality option, rolling timing option, and month end timing option, and these options restrict each other, making the pricing of Treasury bond futures extremely difficult. Quality option plays a dominant role in these three options. This article creatively divides quality options into theoretical quality option caused by the definition deviation of conversion factor and disturbance quality option caused by the market factors except for interest rate. Using the bond valuation method based on the yield to maturity curve, this article puts forward the embedded theoretical quality option and China's Treasury bond futures pricing models. For the empirical test, the dataset covers a 10‐year Treasury bond futures contract in 151 working days. The results show that the relative error between our model and the actual closing price of the Treasury bond futures is small compared with the cost of carry model, which excludes any embedded options. This research constructs a practical and straightforward pricing model of embedded theoretical quality option.
Quantification of Airborne Concentrations of Nanoscale Dusts by Particle Gravimetry Using Ionic‐Liquid Modified Polymeric Electrospun Fibers
Authors: Tok Zeki , Ertekin Kadriye
Published: May 2024

In this work, functional polymeric filters are prepared by electrospinning using four different non‐ionic polymers or their blends together with deliberately selected additives, and then tested for quantification of the nano‐sized powders. Particle gravimetry is used for the quantitative determination of the dusts. Validation studies are carried out using the ICP‐OES technique. The polymeric fibers prepared with different contents consist of PS/PMMA, PVDF/EC/PMMA, chitosan, chitosan/PMMA and PMMA/PVDF, respectively. The ionic liquids of tetra‐n‐butylammonium tetrafluoroborate, 1‐ethyl‐3‐methylimidazolium hexafluorophosphate and hexadecyltrimethylammonium bromide are used as additives for the preparation of the functional polymeric fibers. The prepared nanoscale dusts and electrospun fibers are characterized by SEM, XRD, XPS, and size distribution analysis techniques, respectively. Among them, the CTAB‐modified chitosan fibers exhibit the highest dust retention efficiency. This study introduces a new approach to the quantification of nano‐sized powders. In addition, it is concluded that the proposed method can be used in pre‐concentration before testing, cleaning powders from the working environment and quantitative analysis of nanoscale powders. The presented materials can also be used to improve indoor air quality and potential worker exposure in workplaces.
Addressing Inequality: How to Better Serve Community College Students Who Transfer for Bachelor's Degrees
Authors: May Rachel
Published: May 2024

Community colleges can offer access to “social mobility” via bachelor's degree “attainment for students and communities who have not had accessible and affordable pathways,” write the authors of two new companion studies, but, they find, these pathways are “ineffective, inequitable, and not improving fast enough.”