Converting non-Mesogenic to Mesogenic Stacking of Amino-s-Triazine-Based Dendrons with p-CN Phenyl Unit by Eliminating Peripheral Dipole

Three new amino-s-triazine-based dendrons, 1a, 1b, and 1c, containing an aryl-CN moiety in the dendritic skeleton were prepared in 72–81% yields (1a: R1 = − N(n-C8H17)2, R2 = n-OC8H17, 1b: R1 = R2 = − N(n-C8H17)2, 1c: R1 = − N(n-C8H17)2, R2 = − N(n-C4H9)2). Dendrons 1a with N(n-C8H17)2 and n-OC8H17 peripheral substituents, surprisingly, did not show any mesogenic phase during the thermal process. However, non-mesogenic 1a can be converted to mesogenic 1b or 1c by eliminating the peripheral dipole arising from the alkoxy substituent; dendron 1b only comprising the same N(n-C8H17)2 peripheral groups showed a ~25 °C mesogenic range on heating and ~108 °C mesogenic range on cooling. In contrast, dendron 1c possessing different N(n-CmH2m+1)2 (m = 8 versus m = 4) peripheral units, having similar stacking as 1b, exhibited a columnar phase on thermal treatment, but its mesogenic range (~9 and ~66 °C on heating and cooling, respectively) was much narrower than that of 1b, attributed to 1c’s less flexible alkyl chains in the peripheral part of dendron. Dendron 1a with the alkoxy substituent in the peripheral skeleton, creating additional dipole correspondingly, thus, leads to the dendritic molecules having a non-mesogenic stacking. Without the peripheral dipole for intermolecular side-by-side interaction, dendrons 1b and 1c exhibit a columnar phase on thermal treatment because of the vibration from the peripheral alkyl chain.

Novel Approach for the Synthesis of Chlorophosphazene Cycles with a Defined Size via Controlled Cyclization of Linear Oligodichlorophosphazenes [Cl(PCl2=N)n–PCl3]+[PCl6]−

Despite a significant number of investigations in the field of phosphazene chemistry, the formation mechanism of this class of cyclic compounds is still poorly studied. At the same time, a thorough understanding of this process is necessary, both for the direct production of phosphazene rings of a given size and for the controlled cyclization reaction when it is secondary and undesirable. We synthesized a series of short linear phosphazene oligomers with the general formula Cl[PCl2=N]n–PCl3+PCl6– and studied their tendency to form cyclic structures under the influence of elevated temperatures or in the presence of nitrogen-containing agents, such as hexamethyldisilazane (HMDS) or ammonium chloride. It was established that linear oligophosphazenes are inert when heated in the absence of the mentioned cyclization agents, and the formation of cyclic products occurs only when these agents are involved in the process. The ability to obtain the desired size phosphazene cycle from corresponding linear chains is shown for the first time. Known obstacles, such as side interaction with the PCl6– counterion and a tendency of longer chains to undergo crosslinking elongation instead of cyclization are still relevant, and ways to overcome them are being discussed.

Novel Approach for the Synthesis of Chlorophosphazene Cycles with a Defined Size via Controlled Cyclization of Linear Oligodichlorophosphazenes [Cl(PCl2=N)n–PCl3]+[PCl]6–

Despite a significant number of investigations in the field of phosphazene chemistry, the mechanism of this class cyclic compounds formation is still poorly studied. At the same time, a thorough understanding of this process is necessary both for the direct production of phosphazene rings with a given size, and for the controlled cyclization reaction when it is secondary and undesirable. Here we have synthesized a series of short linear phosphazene oligomers with the general formula Cl[PCl2=N]n–PCl3+PCl6– and studied their tendency to form cyclic structures under the influence of elevated temperature or in the presence of nitrogen-containing agents, such as hexamethyldisilazane (HMDS) or ammonium chloride. It was established that linear oligophosphazenes are inert when heated in the absence of the mentioned cyclization agents, and the formation of cyclic products occurs only when these agents are involved in the process. It is for the first time shown the ability to obtain the desired size phosphazene cycle from corresponding linear chain. Known obstacles like side interaction with the PCl6– counterion and a tendency of longer chains to undergo crosslinking elongation instead of cyclization are still relevant and ways to overcome them are being discussed.

Microbial Validation of Dry Aged Beef Trim for Incorporation into Premium Ground Beef

ObjectivesDry aging treatments impart unique flavors desirable by a segment of the population. Ground beef offers flexibility of use at a lower price point. There is potential to add value to lower priced beef cuts by dry aging them and incorporating them into premium grinds. However, the long dry aging period could allow growth of key pathogens. To determine the risk, the prevalence and potential for growth must be assessed. The effect of a dry aging treatment on the population of Salmonella and Listeria monocytogenes was studied.Materials and MethodsAn in-plant assessment of E. coli O157:H7, Salmonella, and Listeria monocytogenes was conducted by swabbing both the fat and lean sides of 25 ribeye rolls or striploins before direct plating and finally enriching samples. Beef shoulder clods were purchased and used to simulate dry aging. The product was cut into 10 cm × 10 cm blocks before inoculating both fat and lean surfaces with a cocktail mixture containing two strains of Listeria monocytogenes and five strains of Salmonella at a rate of 103 CFU/cm2. Blocks were allowed to dry for 15 min between inoculation of sides and before suspension in a refrigerator (4°C) with a circulating fan and 70–80% humidity. Surfaces were removed at a depth < 5mm for collection and plating on selective media at 0, 1, 7, 14, 21, and 28 d post inoculation. Two sides of six blocks were used at each time point; the experiment was replicated a second time. Data were analyzed to test the effect of time, side, and their interaction for each pathogen; replication was a random variable.ResultsSamples collected in a commercial facility showed no occurrence of E. coli O157:H7 or Salmonella, but three presumptive Listeria monocytogenes colonies were found in the quantitative analysis. The plant does not process ready-to-eat products, the main concern with Listeria monocytogenes. Since all product will be trimmed and cooked prior to consumption, and with the low amount of Listeria monocytogenes, the risk associated with Listeria monocytogenes is relatively low. To validate use of the dry aging treatment on sub-primals to be used for ground beef, the microbial population of the key pathogens used during inoculation must not increase over the treatment period. Salmonella levels on d 1 and 14 were similar (P = 0.53), but numerically less than d 0, and lower (P = 0.0028) on d 1, 21, and 28. There was an effect of side of inoculation; the fat side had significantly higher (P = 0.046) Salmonella levels over the duration of the study. This suggests that Salmonella may have had slightly better attachment to fat at inoculation, but it had no bearing on growth dynamics thereafter. There was no day by side interaction detected (P = 0.51). Listeria monocytogenes showed a similar overall trend; counts were similar on d 7, 14, and 21 (P = 0.079), and numerically less than d 0, whereas counts were lower (P = 0.014) on d 1 and 28. No effect of side (P = 0.21) or a day by side interaction (P = 0.66) were observed.ConclusionOverall, Salmonella and Listeria monocytogenes did not increase during the 28d aging period, indicating that dry-aged beef trim is not higher risk than fresh beef trim. Thus, additional risk mitigation steps may not be necessary during processing of dry aged versus fresh ground beef.

Hak Pilih (Khiyar) Dalam Transaksi Jual Beli Di Media Sosial Menurut Perspektif Hukum Islam

Islam has taken into account the right to select (khiyar) in buying and selling transaction with the aim of avoiding possible fraud, forgery and so on so as to create a willingness between each party. Khiyar could be conducted when sellers and buyers meet directly physically as that in any buying and selling transaction. While in the modern buying and selling process done in cyberspace, especially in social media such transaction raises the question "what is the khiyar in the cyberspace transaction?" Although the transaction occurs two-side interaction, between the seller and the buyer both do not meet directly in one place and goods traded could not be held or reversed. Buyers could only see photos or video of goods to be purchased along with its prices. Based on the writer's study, it could be concluded that the buying and selling transaction in social media which although between the seller and the buyer both do not meet directly physically—only in the virtual world—the transaction is still considered in one majlis so the khiyar is still considered adequate and valid. Because the so-called one majlis should not be interpreted that both the seller and buyer are equally present in one place. But what is meant by one majlis is, the so-called ijab qabul is done within the time in a contract, in the sense that after the ijab is pronounced followed with the so-called qabul in a transaction or when pronouncing ijab qabul is not interspersed with other words which according to custom is assumed to be capable of interrupting it

Mentoring Girls in Science

Content area specialists (scientists) are often recruited as mentors of students to address issues in science education. These scientists are frequently recruited to help with the teaching of science, however, quite often do not have the pedagogy skills needed to be role models for young children. Guidance in the selection appropriate mentors would help maximize the potential influence on students understanding of who does science, where science is done and what scientists do. This study illustrates six case studies of scientists as they worked with middle school girls and identifies five characteristics educators should look for in selecting science mentors successful in broadening students' perceptions of scientists. The data was collected during ‘Side-by-Side' interaction with scientists/mentors during a summer camp experience and has implications for classroom practice as the use of mentors can be structured to support the infusion of Science as a Human Endeavor. As the students' experiences with mentor scientists helped to shape their perception of those who pursue careers in science and what it is that scientists do, careful consideration and preparation of mentors were critical to the success of the program, and so this paper also provides suggestions to help highly trained and highly educated scientists in these mentorship roles.