Spectral narrowing of Yb:YAG waveguide lasers through hybrid integration with ultrafast laser written Bragg gratings

Laser written waveguides in crystalline materials can be used to make highly efficient, high gain lasers. The bi-directional emission from such lasers however is typically broadband with poor spectral control. Hybridizing a tapered, mode matched laser written Bragg grating with a broadband Yb:YAG crystalline waveguide laser, we demonstrate single longitudinal mode output from one end of the device. Careful control of the grating characteristics led to laser thresholds below 90 mW, slope efficiencies greater than 42% and output powers greater than 20 mW.

Competition of Faraday rotation and birefringence in femtosecond laser direct written waveguides in magneto-optical glass

We consider the process of Faraday rotation in femtosecond laser direct-write waveguides. The birefringence commonly associated with such waveguides may be expected to impact the observable Faraday rotation. Here, we theoretically calculate and experimentally verify the competition between Faraday rotation and birefringence in two waveguides created by laser writing in a commercial magneto-optic glass. The magnetic field applied to induce Faraday rotation is nonuniform, and as a result, we find that the two effects can be clearly separated and used to accurately determine even weak birefringence. The birefringence in the waveguides was determined to be on the scale of Δn = 10(-6) to 10(-5). The reduction in Faraday rotation caused by birefringence of order Δn = 10(-6) was moderate and we obtained approximately 9° rotation in an 11 mm waveguide. In contrast, for birefringence of order 10(-5), a significant reduction in the polarization azimuth change was found and only 6° rotation was observed.

Annealing dynamics of waveguide Bragg gratings: evidence of femtosecond laser induced colour centres

There is still significant speculation regarding the nature of femtosecond laser induced index change in bulk glasses with colour centre formation and densification the main candidates. In the work presented here, we fabricated waveguide Bragg gratings in doped and undoped phosphate glasses and use these as a diagnostic for monitoring subtle changes in the induced refractive index during photo- and thermal annealing experiments. Reductions in grating strengths during such experiments were attributed to the annihilation of colour centres.

High efficiency, multi-Watt CW yellow emission from an intracavity-doubled self-Raman laser using Nd:GdVO4

Efficient multi-Watt continuous-wave (CW) yellow emission at 586.5 nm is demonstrated through intracavity frequency-doubling of a Nd:GdVO(4) self-Raman laser pumped at 880 nm. 2.51 W of CW yellow emission with an overall diode-to-yellow conversion efficiency of 12.2% is achieved through the use of a 20 mm long Nd:GdVO(4) self-Raman crystal and an intracavity mirror which facilitates collection of yellow emission generated within the resonator, and reduces thermal loading of the laser crystal.

A patient with dizziness, tachycardia and a DDDR pacemaker

An 84-year-old female patient presented to the coronary care unit with dizziness. A DDD-R minute ventilation sensor pacemaker had been implanted eight years previously. The ECG showed an atrial and ventricular paced rhythm of 140 beats/min. After disconnecting the patient from the cardiac monitor the pacemaker rate dropped gradually to 90 beats/min. The cardiac rhythm monitoring system applies low-amplitude electrical pulses in order to measure respiration rate by transthoracic impedance (TTI) measurement. The minute ventilation pacemaker sensor is driven by the same TTI measurement for rate response. Inappropriate interference between these two systems caused a sensor-driven high pacemaker rate. The dizziness was not related to the sensor-driven high rate.

Passive mode locking of a self-frequency-doubling Yb:YAl(3) (BO(3))(4) laser

We report passive mode-locking experiments with a novel self-doubling laser crystal Yb:YAl(3)(BO(3))(4) (Yb:YAB). The diode-pumped laser was mode locked by an ion-implanted semiconductor saturable absorber mirror. Far off phase matching, soliton mode locking produced pulse widths of 198 fs to 1.4 ps, with up to 660-mW output and optical efficiency of 24% at 1040 nm. The shortest pulses had a peak power of 28 kW with 440-mW average power and 16% efficiency. A few degrees off phase matching, a total of 60 mW of green femtosecond pulses was generated simultaneously. Close to phase matching, the laser produced picosecond pulses and, without infrared output, a total of 270 mW of green output, corresponding to 10% conversion efficiency (absorbed pump to green output).

Efficient continuous-wave self-frequency-doubling green diode-pumped Yb:YAl(3)(BO(3))(4) lasers

Efficient cw self-frequency-doubled green laser output of 160 mW has been obtained from Yb:YAl(3)(BO(3))(4) crystal pumped by 1.4-W incident power from a fiber-coupled 976-nm laser diode. The incident-pump-power-green-output-power conversion efficiency is greater than 11.3%, and the electrical-input-green conversion efficiency is 3.9%. Tunable green output from 513.0 to 545.8 nm is also demonstrated with a quartz birefringent filter.

Physical interaction between Wilms tumor 1 and p73 proteins modulates their functions

The WT1 gene, which is heterozygously mutated or deleted in congenital anomaly syndromes and homozygously mutated in about 15% of all Wilms tumors, encodes tissue-specific developmental regulators. Through alternative mRNA splicing, four main WT1 protein isoforms are synthesized. All isoforms can bind to DNA via their zinc fingers, albeit with different affinities and specificities, and thereby modulate the transcriptional activity of their target genes. Several proteins bind to and alter the transcription regulatory properties of the WT1 proteins, including the product of the tumor suppressor gene p53. Interaction between WT1 and p53 was shown to modulate their ability to regulate the transcription of their respective target genes. Here, we report that all four isoforms of WT1 bind to p73, a recently cloned homologue of p53. p73 binds to the zinc finger region of WT1 and thereby inhibits DNA binding and transcription activation by WT1. Similarly, WT1 inhibits p73-induced transcription activation in reporter assays and counteracts p73-induced expression of endogenous Mdm2. This, taken together with our finding that WT1 also interacts with p63/KET, another p53 homologue, suggests that association between WT1 and the members of the p53 family of proteins may be an important determinant of their functions in cell growth and differentiation.

Sutureless microvascular anastomoses by a biodegradable laser-activated solid protein solder

A new sutureless technique to successfully anastomose the abdominal aorta of rats (1.3 mm in diameter) by using a fully biodegradable, laser-activated protein solder is presented. A total of 90 rats were divided into two groups randomly. In group one, the anastomoses were performed by using conventional microsuturing technique, whereas in group two, the anastomoses were performed by using a new laser welding technique. In addition, each of the two groups were divided into five subgroups and evaluated at different follow-up periods (10 minutes, 1 hour, 1 day, 1 week, and 6 weeks). At these intervals, the anastomoses were evaluated for patency and tensile strength. Three anastomoses in each subgroup were processed for light and electron microscopy. All anastomoses were found to be patent. The mean clamp time of the anastomoses performed with conventional suturing was 20.6 minutes compared with 7.2 minutes for the laser-activated welded anastomoses (p < 0.001). The strain measurements showed a stronger mechanical bond of the sutured anastomoses in the initial phase. However, at 6 weeks the tensile strength of the laser-welded anastomoses was higher compared with the conventional suture technique. Histologic evaluations revealed a near complete resorption of the solder after 6 weeks. The junction site of the vessel ends cannot be determined on the luminal side of the artery. In conclusion, a resorbable protein used as a solder, activated by a diode laser, can provide a reliable, safe, and rapid arterial anastomosis, which could be performed by any microsurgeon faster than conventional suturing after a short learning curve.

Internal translation initiation generates novel WT1 protein isoforms with distinct biological properties

The Wilms' tumor 1 gene, WT1, is homozygously mutated in a subset of Wilms' tumors. Heterozygous mutations in WT1 give rise to congenital anomalies. During embryogenesis, WT1 is expressed mainly in the kidneys, uterus, and testes. Alternative splicing of the WT1 mRNA results in synthesis of four main WT1 protein isoforms with molecular masses of 52-54 kDa. In addition, translation initiation at a CUG upstream of the initiator AUG generates four larger WT1 proteins of 60-62 kDa. We describe here the existence of novel WT1 isoforms and demonstrate that they are derived from translation initiation at the second in-frame AUG of the WT1 mRNA. These N-terminally truncated WT1 proteins of 36-38 kDa can be detected in several cell lines, mouse testes, and Wilms' tumor specimens. They can bind to DNA and direct transcription from reporter constructs. The shorter WT1 protein lacking the two splice inserts has a greater transcription activation potential than the corresponding main WT1 protein isoform but shows no transcription repression potential. Overexpression of full-length or N-terminally truncated WT1 efficiently induces apoptosis. These data show that additional WT1 isoforms with distinct transcription-regulatory properties exist, which further increases the complexity of WT1 expression and activity.

[Pressure-reducing effect of latanoprost 0.005%]

BACKGROUND

Earlier studies in monkeys have shown that latanoprost 0.005% lowers the IOP by improving the uveoscleral Outflow. We wanted to know if this is also the case in the human eye.

PATIENTS AND METHODS

We used our new aqueous humor outflow test with 2-nitrophenyl-acetate in 9 healthy human volunteers, mean age 32 +/- 8.3 years. They were measured before and 12 h after receiving one drop of latanoprost 0.005% in one eye, randomly chosen. The ocular Photometer was used to quantify the disappearance of the dye out of the anterior chamber.

RESULTS

The half-life time of the dye is shortened after latanoprost 0.005%. It is significantly correlated to the pressure lowering effect of latanoprost 0.005% (r2 = 0.5968).

CONCLUSION

The dye-dilution technique proves that latanoprost 0.005% influences the outflow of the human eye. The better the outflow, the greater the pressure drop in the eye. The experiment nicely shows that photometric quantification of 2-nitrophenyl-acetate is a simple, reliable test for the knowledge of the aqueous humor outflow.

Isolation and identification of the human homolog of a new p53-binding protein, Mdmx

We recently reported the identification of a mouse cDNA encoding a new p53-associating protein that we called Mdmx because of its structural similarity to Mdm2, a well-known p53-binding protein. Here we report the isolation of a cDNA encoding the human homolog of Mdmx. The ORF of the cDNA encodes a protein of 490 amino acids, 90% similar to mouse Mdmx. The homology between Mdmx and Mdm2 is most prominent in the p53-binding domain and the putative metal-binding domains. The Mdmx protein, which, based on SDS-PAGE, has a MW of 80 kDa, can bind p53 in vitro. The human MDMX gene is transcribed in all tissues tested, with high levels in thymus. By fluorescence in situ hybridization analysis we mapped the mouse mdmx gene to chromosome 1 (region F-G) and the human MDMX gene to chromosome 1q32.

Primary non-Hodgkin's lymphoma of the cranial vault

We present a case of primary B-cell, large-cell, lymphoma of the skull vault in a 50-year-old HIV-positive male, who presented with a history of unilateral headache and a swelling on the scalp. Primary non-Hodgkin's lymphoma of the skull is rare, with only ten such cases in adults previously described. We suggest that this is the second reported case in an HIV-positive individual.

[Contact glass tonometer]

This paper present a tonometer incorporated in a contact lens, which allows simultaneous measurement of intraocular pressure and performance ophthalmoscopy. The tonometer can record the pulse curve continuously, which can give us an indication of any circulatory problem. The device is therefore expected to yield additional information useful for the diagnosis of early glaucoma. Te device has three force sensors built in, which allow continuous measurement of the force exerted on the eye surface by the contact lens. The force of the contact lens on the eye can be altered and makes the adjustment of different eye pressures possible. These induced changes of the eye pressure and their influence on the fundus can be checked. We have taken some measurements on enucleated human eyes to compare our device with a Statham tansducer in the vitreous. We found a good correlation. We are currently taking measurements in volunteers. The clinical relevance of these observations and measurements will be examined in a future study.

MDMX: a novel p53-binding protein with some functional properties of MDM2

Here we report the isolation of a cDNA encoding a new p53-associating protein. This new protein has been called MDMX on the basis of its structural similarity to MDM2, which is especially notable in the p53-binding domain. In addition, the putative metal binding domains in the C-terminal part of MDM2 are completely conserved in MDMX. The middle part of the MDMX and MDM2 proteins shows a low degree of conservation. We can show by co-immunoprecipitation that the MDMX protein interacts specifically with p53 in vivo. This interaction probably occurs with the N-terminal part of p53, because the activity of the transcription activation domain of p53 was inhibited by co-transfection of MDMX. Northern blotting showed that MDMX, like MDM2, is expressed in all tissues tested, and that several mRNAs for MDMX can be detected. Interestingly, the level of MDMX mRNA is unchanged after UV irradiation, in contrast to MDM2 transcription. This observation suggests that MDMX may be a differently regulated modifier of p53 activity in comparison with MDM2. Our study indicates that at least one additional member of the MDM protein family exists which can modulate p53 function.

[Yellow discoloration of the lens in the diabetic patient]

BACKGROUND

The yellowing is a precursor of the cataract. In the diabetic patient this phenomenon is established earlier than in normal control groups. In the literature the yellowing is explained by elevated glucose levels. Does the duration of diabetes play a key role for this phenomenon?

MATERIALS AND METHODS

The yellowing of the lens can be very well detected by the ocular photometer. Using this device, 52 well regulated diabetics without retinopathy and 19 diabetics with mild background retinopathy were examined. We determined the contrast-transfer ratio of the lens, which has been correlated with the age, the duration of diabetes, the weight of the patient, the bodymass index and the hemoglobin a1c of the patient.

RESULTS

Without retinopathy none of the introduced correlations were significant. If the diabetes is well regulated, even a long duration of diabetes does not cause any yellowing of the lens. With mild retinopathy the yellowing of the lens could not be detected because of the sites of measurement, which were changing. A high correlation between the duration of diabetes and the intensity of the macula and the excavation has been found. The macula gets darker and the excavation gets brighter.

CONCLUSIONS

The yellowing of the lens does not depend on any of the presented parameters. In diabetics with mild background retinopathy the macula gets darker. This can be interpreted as an hyperemia of the choroid. Most probably this phenomenon is caused by the decline of sympathetic nerve fibers.

Oncocytic metaplasia of the nasopharynx or extra-parotid Warthin's tumour?

A case of oncocytic metaplasia obstructing the Eustachian tube in an elderly patient is described. Histologically, it was similar to Warthin's tumour of the parotid gland. The lymphocytes were predominantly T cell, unlike those of Warthin's tumour which are predominantly B cell. It is proposed that oncocytic metaplasia represents an early stage in the evolution of Warthin's tumour.

A 40 kd protein binds specifically to the 5′-untranslated regions of yeast mitochondrial mRNAs

Using a gel mobility shift assay we show that a 40 kd protein (p40), present in extracts of yeast mitochondria, binds specifically to the 5'-untranslated leader of cytochrome c oxidase subunit II mRNA. Binding of p40 to coxII RNA protects an 8-10 nucleotide segment from diethylpyocarbonate modification, indicating that the protein interacts with only a restricted region of the 5'-leader. This segment is located at position -12 with respect to the initiation AUG. Deletion of 10 nucleotides encompassing this site completely abolishes protein binding. Nevertheless, Bal31 deletion analysis within the coxII leader shows that a major part of the leader is essential for p40 binding, suggesting that binding of the protein is also dependent on secondary structural features. p40 binds to other mitochondrial leader mRNAs including those for coxI, coxIII and cyt b. p40 is present in a cytoplasmic (rho0) petite mutant lacking mitochondrial protein synthesis. It is therefore presumably nuclear encoded. The possible biological function of the protein is discussed.

Asymmetrical limb reduction deformities--aetiological considerations

The clinical features of a newborn female infant with reduction deformities of three limbs and no additional major malformations are presented. Diagnostic precision is crucial for accurate prognostication since both genetic and non-genetic causes have to be considered in such instances. The main differential diagnosis in our patient included a number of specific inherited disorders of which limb reduction is a component, as well as the consequences of both early amniotic rupture and fetal vascular disruption. We favoured the latter and concluded that the risk of recurrence was minimal. The approach to limb reduction disorders should be individualized.

Acquired amegakaryocytic thrombocytopenic purpura: a syndrome of diverse etiologies

The possible pathogenetic mechanisms responsible for the production of acquired amegakaryocytic thrombocytopenic purpura (AATP) were investigated in a group of patients with this disorder. Absence of megakaryocytes and small platelet glycoprotein-bearing mononuclear cells, as determined by immunochemical staining of patient marrows with an antisera to platelet glycoproteins, suggested that the defect in AATP occurs in an early progenitor cell of the megakaryocytic lineage. Using an in vitro clonal assay system for negakaryocytic progenitor cells or megakaryocyte colony-forming units (CFU-M), the proliferative capacity of AATP marrow cells was then assessed. Bone marrow cells from three of four patients formed virtually no megakaryocyte colonies, suggesting that in these individuals the AATP was due to an intrinsic defect in the CFU-M. Bone marrow cells from an additional patient, however, formed 12% of the normal numbers of colonies, providing evidence for at least partial integrity of the CFU-M compartment in this patient. Serum specimens from all six patients were screened for their capacity to alter in vitro megakaryocyte colony formation. Five of six sera enhanced colony formation in a stepwise fashion, demonstrating appropriately elevated levels of megakaryocyte colony-stimulating activity. The serum of the patient with partial integrity of the CFU-M compartment, however, stimulated colony formation only at low concentrations. At higher concentrations, this patient's serum actually inhibited the number of colonies cloned, suggesting the presence of a humoral inhibitor to CFU-M. Serum samples from all patients were further screened for such humoral inhibitors of megakaryocyte colony formation using a cytotoxicity assay. The patient whose serum was inhibitory to CFU-M at high concentrations was indeed found to have a complement-dependent serum IgG inhibitor that was cytotoxic to allogeneic and autologous marrow CFU-M but did not alter erythroid colony formation. These-studies suggest that AATP can be due to at least two mechanisms: either an intrinsic effect at the level of the CFU-M or a circulating cytotoxic autoantibody directed against the CFU-M.

Paroxysmal nocturnal hemoglobinuria terminating as erythroleukemia

A case of a patient who developed erythroleukemia 3 years into the course of paroxysmal nocturnal hemoglobinuria (PNH) is presented. A case of erythroleukemia with a positive sucrose lysis test has been reported, but our case appears to be the first with a long clinical course of PNH evolving into erythroleukemia. The association between these two diseases, their possible clonal origin, and how they fit into the myelodysplastic syndromes are discussed.

Contributions to the Analysis of Rubber. IV. Determination of Manganese in Crude Rubber; in Rubber Mixtures and in Fillers

A scheme for the determination of manganese in mineral fillers, compounding ingredients, crude rubber, rubber mixtures and rubberized materials is described. It is shown that with this method the use of potassium persulfate and two drops of orthophosphoric acid, as proposed by Kehren for the oxidation of colorless manganese ions to red permanganate ions, is advisable. When potassium periodate is used, small quantities of manganese escape detection. It is further shown that there is no appreciable difference between concentration with nitric acid and evaporation with hydrochloric acid and a little sulfuric acid. If, however, the ash is decomposed by soda-potash mixture, the manganese contents are considerably higher. Doubtless these higher values can be accounted for by manganese compounds which are occluded in silicates, and which can be regarded as harmless. A reliable method for the decomposition of the manganese compounds is therefore desirable. The results of analyses of the manganese contents of a large number of various materials are tabulated, and the maximum manganese contents of various materials allowed by the Netherlands Government Rubber Institute are given.

The Oxidation Products of Rubber

In their summary of the aging of vulcanized rubber, Porritt and Scott state that three factors are responsible for the changes in mechanical properties of vulcanized rubber during aging, viz.: (a) oxidation of the rubber; (b) after-vulcanization; (c) some colloidal change of the rubber, sometimes termed aggregation. Of these factors, oxidation is by far the most important because it is responsible for the decrease in mechanical properties, which leads to the general deterioration of rubber from a technical standpoint. It was Marzetti who proved that the decrease of mechanical properties in accelerated aging is due to oxidation. Later, Kohman confirmed this in a more concise way and showed that even such small amounts as 0.5% of oxygen absorbed by vulcanized rubber are sufficient to decrease tensile properties to 50% of their original value. When studying aging, three ways of tackling this problem are possible, viz.: (1) Investigations of the mechanical properties, either under normal conditions, or under special conditions such as elevated temperature or high speed. (2) Determination of oxidation products, which are formed during oxidation of the rubber. (3) Direct determination of the amount of oxygen which is absorbed by the rubber. It is clear that any of these methods may be combined with accelerated aging tests.

Contributions to the Analysis of Rubber. III. Determination of Copper in Raw Rubber, in Mixtures, and in Fillers

It is already well known that copper compounds have an extremely harmful effect on rubber articles. Since, however, very small quantities of copper are always present in fillers, in fact, in compounding ingredients in general and even in ordinary plantation rubber itself, it is not possible to manufacture a rubber article which is free of copper. In view of this, one must be content in each case with keeping the copper content within a certain allowable limit. However, it has been found that not only is the quantity of copper of decisive importance, but that still other factors play a part in the harmful effects brought about by the copper. Attention has been called repeatedly in the literature to the fact that copper compounds which are injurious are those which dissolve in the rubber mixture. Nevertheless, it is certain that the harmful effects of copper depend not only on solubility but also on other factors. But since so little is known about this problem, nothing can be done for the time being except to regard any copper which may be found as injurious. In the Netherlands Government Rubber Institute the permissible quantity of copper in rubber articles has been set at 0.001 per cent. Although with this percentage harmlessness is not guaranteed, it may still be expected that, with such small percentages of copper compounds, aging is not affected unfavorably. The present work is concerned chiefly with methods for determining copper.

Contributions to the Analysis of Rubber. II. The Qualitative Determination of the Serum Components of Raw Rubber and of Vulcanized Rubber

The use of latex in the rubber industry has been increasing to a considerable extent, and in many cases where formerly solutions of ordinary plantation rubber were used exclusively, e. g., for impregnating fibres, spreading and adhering textiles, and manufacturing dipped goods, latex mixtures are now employed. Then again there is increasing interest in rubber prepared by evaporation or spraying of latex, especially for the production of powdered rubber. Consequently the time has come, as is evident from recent publications, when it may be an important problem whether in the preparation of a rubber mixture it is best to use ordinary plantation rubber, latex, or, perhaps, evaporated latex. Now the peculiarity of a rubber mixture prepared from latex or from evaporated latex is its relatively high precentage of serum substances from the latex. In the first Communication on the present subject, which dealt with the “Determination of the Water-Soluble Components of Rubber,” a method was described for determining the serum substances in vulcanized rubber. In view of the fact that with technical rubber mixtures, and in the presence of zinc, calcium, and magnesium compounds, this method is complicated and tedious, the present experiments were carried out with an aim to developing a procedure for determining qualitatively the serum substances. A method of this kind must naturally be restricted to the identification of some substance which originates in the serum and not in the curvatives or other compounding ingredients. Among the various substances which are present in latex serum, 1-methylinositol is one of the most important, and rubber mixtures prepared from latex or from evaporated latex contain a notable quantity of this substance. Consequently proof of the existence of 1-methylinositol in a mixture should be evidence of the presence of serum substances. The investigation to be described was therefore confined to the development of a characteristic reaction of 1-methylinositol.

Contributions to the Analysis of Rubber. I. Determination of the Water-Soluble Components of Rubber

1. It is shown that the methods which are ordinarily used for determining water-soluble substances in raw rubber give low results, and are quite useless for vulcanized rubber. 2. New analytical procedures are developed for determining the water-soluble substances in raw rubber and in vulcanized rubber. These procedures are carried out in the following manner. (a) Raw Rubber.—Heat 2 grams of rubber in 80 cc. of xylene and 5 cc. of acetic acid on a water bath until the rubber is completely dissolved, add 5 cc. of acetic acid and 10 cc. of water, heat for 3–4 hours on the water bath with frequent agitation, transfer to a distilling flask (rinsing the first flask with 50 cc. of hot water), distill the xylene with steam, filter the residual solution, evaporate the filtrate on a water bath; and dry at 100° C. (b) Vulcanized Rubber and Rubber Mixtures.—First extract the sample with acetone, heat 2 grams of the acetone-extracted sample with 80 cc. of xylene on a water bath, add 5 cc. of acetic acid, reflux the mixture on an oil bath, after complete dissolution add 5 cc. of acetic acid and 10 cc. of water, heat the solution for 2 hours on an oil bath at 110–120° C., distill the xylene, as in the determination with raw rubber, filter the residue, evaporate the filtrate to dryness, take up the residue in 50 cc. of water, pass a current of hydrogen sulfide through the solution for 10 minutes to precipitate zinc as sulfide, filter, evaporate the filtrate, and dry the residue at 100° C. 3. In the presence of calcium compounds, magnesium compounds, glue and textiles, the method gives false results. Modifications of the method are therefore recommended, whereby these substances are eliminated.

Vulcanization with Benzoyl Peroxide. I. Contribution to the Knowledge of the Vulcanization Process

Three-quarters of a century have passed since the discovery of the vulcanization process by Charles Goodyear, Thomas Hancock, and Alexander Parks without the discovery of an essentially new process of vulcanization. In 1915 Ostromislenski reported the discovery of two new methods of vulcanization, namely, vulcanization with nitrocompounds and vulcanization with peroxides and peracids like benzoyl peroxide. Ostromislenski was of the opinion that vulcanization is a process which can be divided into two distinct phases, “Thus we arrive at the conclusion that the vulcanization of caoutchouc is divided sharply into two fundamental phases: 1, a chemical reaction affecting only an insignificant part of the caoutchouc and, 2, adsorption or swelling of the unchanged caoutchouc into the product of this chemical reaction.” a concept which was developed by van Iterson, Jr., in somewhat different form as a working hypothesis for the vulcanization process. It is noteworthy that only in 1929 did Ostromislenski publish a second communication on vulcanization with benzoyl peroxide, even then without offering any new theoretical points.

The Oxidation of Vulcanized Rubber

SINCE Kirchhof in June, 1927, gave to the first general meeting of the German Rubber Society in Essen a detailed review of work concerned with the oxidation of rubber, it seems superfluous to publish any extensive bibliography thereon. We prefer to limit ourselves, for the present, almost exclusively to a few experiments in this field. However, we may refer in a general way to the work of others. It is a notable fact that all investigations of the oxidation of vulcanized rubber have been always based on the kinetics of the oxygen combination, and, as far as isolation of the oxidation products is concerned, on a late stage of oxidation, the isolation of oxidation products during the early stages of oxidation being left out of consideration. Thus, for example, Kirchhof in his work published in 1913 studied the behavior of ground vulcanized rubber which had been heated for 100 hours in a current of air at 100° C. and thereby strongly oxidized, as indicated by the increase in weight (11–13%). Eaton and Day later in 1919 made experiments of a similar nature. Here, too, the kinetics principally were studied, and the samples were examined only after oxidation was far advanced. Again in Kirchhof's recent work already mentioned, the oxidation products were studied only after prolonged oxidation.