Thermal Stability of Potassium-Promoted Cobalt Molybdenum Nitride Catalysts for Ammonia Synthesis

The application of cobalt molybdenum nitrides as ammonia synthesis catalysts requires further development of the optimal promoter system, which enhances not only the activity but also the stability of the catalysts. To do so, elucidating the influence of the addition of alkali metals on the structural properties of the catalysts is essential. In this study, potassium-promoted cobalt molybdenum nitrides were synthesized by impregnation of the precursor CoMoO4·3/4H2O with aqueous KNO3 solution followed by ammonolysis. The catalysts were characterized with the use of XRD and BET methods, under two conditions: as obtained and after the thermal stability test. The catalytic activity in the synthesis of ammonia was examined at 450 °C, under 10 MPa. The thermal stability test was carried out by heating at 650 °C in the same apparatus. As a result of ammonolysis, mixtures of two phases: Co3Mo3N and Co2Mo3N were obtained. The phase concentrations were affected by potassium admixture. The catalytical activity increased for the most active catalyst by approximately 50% compared to non-promoted cobalt molybdenum nitrides. The thermal stability test resulted in a loss of activity, on average, of 30%. Deactivation was caused by the collapse of the porous structure, which is attributed to the conversion of the Co2Mo3N phase to the Co3Mo3N phase.

Preparation of Pt electrocatalyst supported by novel, Ti(1−x)MoxO2-C type of composites containing multi-layer graphene

Ball milling is a relative simple and promising technique for preparation of inorganic oxide–carbon type of composites. Novel TiO2-C and Ti0.8Mo2O2-C type of composites containing multi-layer graphene were prepared by ball milling of graphite in order to get electrocatalyst supports for polymer electrolyte membrane fuel cells. Starting rutile TiO2 was obtained from P25 by heat treatment. Carbon-free Ti0.8Mo2O2 mixed oxide, prepared using our previously developed multistep sol–gel method, does not meet the requirements for materials of electrocatalyst support, therefore parent composites with Ti0.8Mo2O2/C = 75/25, 90/10 and 95/5 mass ratio were prepared using Black Pearls 2000. XRD study of parent composites proved that the oxide part existed in rutile phase which is prerequisite of the incorporation of oxophilic metals providing CO tolerance for the electrocatalyst. Ball milling of TiO2 or parent composites with graphite resulted in catalyst supports with enhanced carbon content and with appropriate specific surface areas. XRD and Raman spectroscopic measurements indicated the changes of graphite during the ball milling procedure while the oxide part remained intact. TEM images proved that platinum existed in the form of highly dispersed nanoparticles on the surface of both the Mo-free and of Mo-containing electrocatalyst. Electrocatalytic performance of the catalysts loaded with 20 wt% Pt was studied by cyclic voltammetry, COads-stripping voltammetry done before and after the 500-cycle stability test, as well as by the long-term stability test involving 10,000 polarization cycles. Enhanced CO tolerance and slightly lower stability comparing to Pt/TiO2-C was demonstrated for Pt/Ti0.8Mo2O2-C catalysts.

Stability Testing of Pharmaceutical Products

Stability studies must be carried out according to the guidelines provided by the International Conference of Harmonization, World Health Organization, and other agencies in a scheduled manner. The pharmaceutical product’s stability can be defined as the ability, within its physical, chemical, microbiological, toxicology, protective, and informational requirements of a particular formulation in a specific container-closure system. It also guarantees that the performance, safety, and efficacy are maintained throughout the shelf life of any pharmaceutical product which is considered as pre-requisite for acceptance and approval. Different stability test methods have originated with the need for constant monitoring of drugs and products for their quality and purity. In this review, we have included the types of stability of drugs substances, the relevance of different methods used to test the stability of the pharmaceutical product, guidelines issued to test the stability of pharmaceuticals, stability testing protocols which describes the main components of a well-controlled and regulated stability test and other aspects of stability.

A Systematic Review of the Stability of Extemporaneous Pediatric Oral Formulations

Background. Extemporaneous compounding is a pharmacy practice to produce suitable pharmaceutical preparations when there are no commercially available, licensed, and age-specific dosage forms. Compared to the use of authorized drugs, these preparations have significant risks. Stability issues are one of the major concerns during the preparation of extemporaneous formulations. Aim. The aim of this work was to study the stability of pediatric extemporaneous formulations of commercially available conventional solid dosage forms by reviewing systematically the currently available stability studies. Method. Articles were searched in the databases of the Web of Science, PubMed, Scopus, EMBASE, Cochrane Library, and Google Scholar. From all the searched articles, a total of 28 experimental studies reporting the stability of oral pediatric extemporaneous formulations were included based on the inclusion criteria. Oral extemporaneous formulations from commercially available dosage forms and pure drugs were considered. According to the United States and British Pharmacopeia (USP and BP), most extemporaneous formulations are accepted as chemically stable if they maintain ≥90% of the original drug amount, physically stable if there is no apparent change in physical property, and microbiologically stable if there is no growth of microorganisms in prepared formulations. Finding. In this study, most extemporaneous pediatric oral formulations were chemically, physically, and microbiologically stable and retained more than 90% of the initial content. Very few studies did not include either a physical stability test or a microbiological stability test. Conclusion. According to this systematic review, the chemical and physical instabilities as well as microbial growth on pediatric oral extemporaneous formulations are very rare in published experimental studies. Most studies show that extemporaneous preparations are stable at the ICH recommended storage conditions and duration. Generally, extemporaneously prepared oral formulations will be the promising option for child medications.

PATCHES FOR ACNE TREATMENT: AN UPDATE ON THE FORMULATION AND STABILITY TEST

The purpose of this article review was to find out more about acne patch formulations and test stability. The method used is searching data from various articles based on Google Scholar, Elsevier, and Molecules with the keywords "Acne vulgaris, acne treatment, acne patches, and types of acne patches” and with a range of years between 2011 and 2021. Based on the type of acne, acne patches are divided into several types, namely microneedle patches, acne medicine patches, and hydrocolloid patches. The results obtained in this review show that the most commonly used acne patch is the medicated acne patch (hydrogel patches), because of its waterproof property to protect acne from secondary infection, it can absorb liquid inside and flatten acne and is cheaper compared to microneedles. The hydrogel patch is also stable at a temperature of 40±2 °C and a relative humidity (RH) of 75±5% for 6 mo of storage.

Uji Aktivitas Antioksidan Sediaan Masker Hidrogel Ekstrak Etanol Teh Hijau (Camellia sinensis) Dengan Metode BCB

Green tea is a plant that contains antioxidants. The content of green tea compounds that act as antioxidants are polyphenols. The addition of natural antioxidants in hydrogel masks has the potential as an alternative to synthetic antioxidants. The purpose of this study was to determine the antioxidant activity of the hydrogel mask preparation of green tea (Camellia sinensis L.) ethanol extract. The method of determining antioxidant activity was carried out by the -Carotene Bleaching (BCB) method. The stability test of the preparation using the cycling test method was carried out for 6 cycles including organoleptic, viscosity, pH, homogeneity tests. The data obtained from the antioxidant activity test is the IC50 value. The IC50 results of the green tea ethanol extract were 27,162 ppm, while the IC50 values for the formulations 1, 2 and 3 were 40,893 ppm, respectively; 35,348 ppm; and 32,270 ppm. The results of the stability test showed that the preparation was stable from the parameters of viscosity, pH and homogeneity but not stable from the organoleptic parameters because there was a color change in the preparation containing the extract after the cycling test process. In conclusion, both extracts and hydrogel mask preparations contain high antioxidants with relatively stable dosage forms.Keywords: Green Tea, Antioxidants, Hydrogel Mask, -Carotene Bleaching (BCB), IC50. AbstrakTeh hijau merupakan salah satu tanaman yang mengandung antioksidan. Kandungan senyawa teh hijau yang berperan sebagai antioksidan adalah polifenol. Penambahan antioksidan alami pada masker hidrogel berpotensi sebagai alternatif pengganti antioksidan sintetis. Tujuan penelitian ini adalah mengetahui aktivitas antioksidan sediaan masker hidrogel ekstrak etanol teh hijau (Camellia sinensis L.). Metode penentuan aktivitas antioksidan dilakukan dengan metode β-Carotene Bleaching (BCB). Pengujian stabilitas sediaan dengan metode cycling test dilakukan sebanyak 6 siklus meliputi uji organoleptik, viskositas, pH, homogenitas. Data yang diperoleh dari uji aktivitas antioksidan berupa nilai IC50. Hasil IC50 ekstrak etanol teh hijau sebesar 27,162 ppm, sedangkan pada sediaan menunjukan nilai IC50 berturut-turut dari formulasi 1, 2 dan 3 sebesar 40,893 ppm; 35,348 ppm; dan 32,270 ppm. Hasil uji stabilitas menunjukkan sediaan stabil dari parameter viskositas, pH dan homogenitas tetapi tidak stabil dari parameter organoleptik karena terjadi perubahan warna pada sediaan yang mengandung ekstrak setelah proses cycling test. Kesimpulannya ekstrak maupun sediaan masker hidrogel mengandung antioksidan tinggi dengan bentuk sediaan relatif stabil.Kata kunci:Teh Hijau; Antioksidan; Masker Hidrogel; β-Carotene Bleaching (BCB);IC50.

Formulation and Stability Test of Lip Cream Preparation of Kenop Flower Ethanol Extract (Gomphrena globosa L.)

Kenop Flower (Gomphrena globosa L.) is used in the manufacture of lip cream because contains betacyanin pigments that function as color pigments. This study aims to determine the physical quality and stability of the lip cream preparation of the ethanol extract of kenop flower (Gomphrena globosa L.). This research was conducted experimentally, including the manufacture of lip cream formulations with ethanol extract of kenop flower (Gomphrena globosa L.) with a concentration of 10%. The results of the physical examination test for lip cream preparations for all preparations have a distinctive vanilla aroma with a semi-solid texture, F0 has ivory white color and F1-F3 has a brown color. The preparations had a homogeneous composition, average pH 6-7, had good greasing power, 5.0-5.8 average dispersion and 60.33-66.67 seconds average adhesion. The stability test carried out on day 28 found that all preparations were stable, had a distinctive vanilla aroma with a semi-solid texture, F0 had ivory white color and F1-F3 had a brown color. The preparation has a homogeneous composition; the average pH is 6-7. Where the lip cream formulas F1 and F3 decreased the pH value on the 28th day from 7 to 6 but tended to be stable and in the pH range that matched the lip pH. And there is no phase separation in all formulas.

Examining the effects of upper extremity function and arm sling type on balance, gait and fall risk in patients with hemiparesis

Background/aims Previous studies have reported conflicting results on the effects of arm slings on the balance and gait of patients with hemiparesis. These previous studies did not consider the ability to control the upper extremity on the affected side as a factor that could affect the patient's balance or gait when an arm sling was applied. Hence, the aim of this study was to investigate the effect of upper extremity function in the affected side and arm position according to the sling type on balance, gait and fall. Methods A total of 31 stroke patients participated in the study and were assigned to two groups according to upper extremity function (low-score group and high-score group). Under three conditions (no sling, forearm sling and shoulder sling), a fall risk test, postural stability test and limits of stability test were performed and speed, stride duration, step length and total time were measured. Results When the high-score group wore forearm slings, the static and dynamic balance ability decreased and the fall risk increased. When the low-score group wore forearm slings and shoulder slings, the static and dynamic balance ability increased and the fall risk decreased. The high-score group had a shorter gait time when wearing shoulder slings. When the low-score group wore forearm slings, the speed and step length increased and the total time decreased, enhancing the overall gait ability. Conclusions For stroke patients with better upper extremity control ability, shoulder slings are more appropriate. For patients with poor upper extremity control ability, forearm slings are more appropriate. Using the appropriate sling according to the upper extremity function can improve balance and gait ability and fall risk can be reduced.

Stability Test of Networked Systems with Multiple Delays

In this paper, we propose a sufficient stability condition for networked systems with multiple delays based on the 2-D polynomials and 2-D Hurwitz-Schur stability. The main advantage of the new stability condition is that it is applicable to the general case of networked systems with multiple, incommensurate delays yet numerically tractable. The characteristic polynomials of networked systems are mapping into 2-D hybrid polynomials, then to test the Hurwitz-Schur stability can. determine the networked systems, examples including system simulations verify the validity of the proposed test algorithms.