Further study on the one-pot synthesis of (E)-2-nonenal from castor oil

A one-step procedure is described for the synthesis of (E)-2-nonenal from commercial castor oil by ozonolysis in methanol, followed by reduction of the ozonide products with dimethyl sulfide and exposure of the resulting intermediate product to dilute sulfuric acid. The developed process allows the production of the aldehyde with a yield of 80% at a purity of 95%. The method has advantages over all those reported earlier, because of inexpensive raw material and reducing agent, recycling of the solvent and its unusual simplicity.     

A method for speeding up beam-tracing simulation using thread-level parallelization

In recent years, the computational power of modern processors has been increasing mainly because of the increase in the number of processor cores. Computationally intensive applications can gain from this trend only if they employ parallelism, such as thread-level parallelization. Geometric simulations can employ thread-level parallelization because the main part of a geometric simulation can be divided into a subset of mutually independent tasks. This approach is especially interesting for acoustic beam tracing because it is an intensive computing task. This paper presents the parallelization of an existing beam-tracing simulation composed of three algorithms. Two of them are iterative algorithms, and they are parallelized with an already known technique. The most novel method is the parallelization of the third algorithm, the recursive octree generation. To check the performance of the multi-threaded parallelization, several tests are performed using three different computer platforms. On all of the platforms, the multi-threaded octree generation algorithm shows a significant speedup, which is linear when all of the threads are executed on the same processor.     

Crystallization behavior of poly(N‐methyldodecano‐12‐lactam). IV. Nonisothermal crystallization

Nonisothermal crystallization of poly(N‐methyldodecano‐12‐lactam) (MPA) was investigated using DSC method at cooling rates of 2–40 K/min. With increasing cooling rate, crystallization exotherms decreased in magnitude and shifted toward lower temperatures. Subsequent heating runs (10 K/min) showed an exotherm just above T_g, which increased in magnitude with the rate of preceding cooling run, corresponding to the continuation of primary crystallization interrupted as the system crossed T_g on cooling. Kinetic evaluation by the Avrami method gave values of exponent n close to 2.0, suggesting two‐dimensional crystal growth combined with heterogeneous nucleation. The Tobin method, covering the intermediate range of relative crystallinities, provided n ? 2.20, suggesting possible partial involvement of homogeneous nucleation at later stages of nonisothermal crystallization. The crystallization rate parameter k^1/n showed a linear dependency on cooling rate for both methods, the Tobin values being slightly higher. The Ozawa approach failed to provide reasonable values of the kinetic exponent m of MPA. The Augis–Bennet method was used to determine the effective activation energy of the entire nonisothermal crystallization process of MPA. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 564–572, 2005     

Work function variations of incandescent filaments during self-cooling in vacuum

A novel method of dynamic measurement of work function (WF) variations of hot metal filaments is described. It is essential in this method that electron emission current (I_e) is recorded during filament self-cooling when no heating power is supplied, thereby I_e is not disturbed by the potential gradient along the filament. WF shift due to the presence of a low-pressure gas, where the main active compounds are O₂ and H₂O, is calculated from an equation derived on the basis of the Richardson formula. The relative increase of WF found by this method was 5 times larger for tungsten than that for tantalum over the entire temperature range from 900 to 1800 K. Our method may be used in research studies of adsorption-related phenomena on metallic surfaces at high temperatures.     

The Importance of Platelets Response during Antiplatelet Treatment after Ischemic Stroke—Between Benefit and Risk: A Systematic Review

Ischemic stroke is a disease related to abnormal blood flow that leads to brain dysfunction. The early and late phases of the disease are distinguished. A distinction is made between the early and late stages of the disease, and the best effect in treating an ischemic stroke is usually achieved within the first hours after the onset of symptoms. This review looked at studies platelet activity monitoring studies to determine the risks and benefits of various approaches including antiplatelet therapy. A study was conducted on recently published literature based on PRISMA. This review includes 32 research articles directly addressing the importance of monitoring platelet function during antiplatelet therapy (dual or monotherapy) after ischemic stroke. In patients with transient ischemic attack or ischemic stroke, antiplatelet therapy can reduce the risk of stroke by 11–15%, assuming that patients respond well. Secondary prevention results are dependent on platelet reactivity, meaning that patients do not respond equally to antiplatelet therapy. It is very important that aspirin-resistant patients can benefit from the use of dual antiplatelet therapy. The individualized approach to secondary stroke prevention is to administer the most appropriate drug at the correct dose and apply the optimal therapeutic procedure to the individual patient.     

Long-term storage stability of selected potato starch – Non-starchy hydrocolloid binary gels

All 3, 4 and 5% potato starch gels containing either κ-carrageenan, guar gum or xanthan gum were prepared and their stability in terms of rheological and textural properties was checked on 30 day storage. It was shown that rheology of these binary potato starch – non-starchy hydrocolloid mixtures could be controlled by anionic character of the admixed hydrocolloid. Depending on the hydrocolloid added, gels made of the tuber starch can either retain their pattern typical for tuber starches or turn into that typical for gels of cereal starches. Hydrocolloids added plasticity to the binary gels but it was lost to a significant extent within the first day of storage. Resulting gels with dominating elastic character are rheologically and texturally fairly stable for subsequent 30 days of storage. Generally, hydrocolloids stabilized potato starch gel on long-time storage to the extent dependent on the gel concentration.     

Dynamic mechanical behaviour of random copolymers of a LC-methacrylate and octyl methacrylate

The dynamic mechanical behaviour of random copolymers of LC monomer-1-(hexyloxycarbonyl)ethyl 4-[4-(methacryloyloxy)benzoyloxy]benzoate (HB) and octyl methacrylate (OMA) was studied in the main transition and flow regions. Even though the aliphatic end groups of the side chain of HB and OMA are roughly the same, the T _g temperature of poly(HB) is ∼ 80 K higher than that of poly(OMA); this fact is due to the presence of the stiff phenyl benzoate mesogenic group in the side chain of HB. With increasing content of OMA in the copolymer the superimposed curves of the storage G′ _p and loss G′′ _p moduli at a constant temperature shift towards shorter frequencies. It has been shown that this shift is mainly due to an increase of the free volume in the copolymers with increasing content of OMA. While HB monomer shows liquid crystalline (LC) properties, its polymer (poly(HB)) and random copolymers with OMA show only isotropic thermal behaviour because no flexible spacer is present in the side chain of HB which would decouple the main chain and mesogenic group motions. This means that neither the homopolymer of HB, nor its copolymers with a flexible comonomer retain the LC properties of the starting LC monomer, HB. Received: 26 September 1996/Revised: 7 November 1996/Accepted: 7 November 1996