Síntesis de ésteres de acetato hexilo, mediante transesterificación química a partir de palma como base sintética de fluidos para sondeos

In the present study the synthesis of a palm based ethylhexyl ester was examined through a transesterification reaction of palm oil methyl ester (POME) with 2-ethylhexanol (EH). A sodium methoxide in methanol solution was used as a catalyst. The reaction was carried out at a fixed pressure of 1.5 mbar by varying the temperature (80–140 °C), POME/2EH molar ratio (1:1.5–1:2.2), reaction time (0.5–4 h) and catalyst concentration (1–2% w/w). The reaction with 2-ethylhexanol involved a single step reversible reaction, thus, the reaction was completed in a very short time. The optimum conditions were obtained in less than 30 minutes with 1.5 mbar pressure, 70 °C, and 1:2 molar ratio of POME to 2EH. The analysis of the final product (ethylhexyl ester) was performed using gas chromatography which exhibited 98% of ethyl hexyl ester yield. The gas chromatography analysis of ethyl hexyl ester revealed two major esters peaks i.e. ethyl hexyl palmitate and ethylhexyl oleate.En el presente estudio se analizó la síntesis de ésteres de acetato de hexilo de palma mediante reacción de transesterificación de los ésteres metílicos de aceite de palma (PME) con 2-etilhexanol (EH). Como catalizador se utiliza una solución de metóxido de sodio en metanol. La reacción se lleva a cabo a presión fija de 1,5 mbar mediante la variación de temperatura (80–140 °C), relación molar POME/2EH (1:1.5–1:2.2), tiempo de reacción (0,5–4 h) y concentración de catalizador (1–2% w / w). La reacción con 2-etilhexanol implica un solo paso de una reacción reversible, por lo tanto, ésta se completa en un tiempo muy corto. Las condiciones óptimas se obtuvieron en menos de 30 min a 1,5 mbar, 70 °C y una relación molar de 1:2 de POME al 2EH. El análisis del producto final se realizó usando cromatografía de gases que mostró un rendimiento del 98% del etilhexil éster. El análisis de la cromatografía de gases del etilhexil éster muestra dos grandes picos correspondientes a los ésteres palmitato y oleato de etilhexilo

HIV testing in re-education through labour camps in Guangxi Autonomous Region, China (a cross-sectional survey)

Objective: HIV testing is mandatory in re-education-through-labour camps (laojiaosuo) in China yet no studies have reported on the process. Methods: The survey response rate was 100% although 29 detainees were excluded because they were under 18 years of age. A cross-sectional face-to-face survey was conducted in three labour camps in Guangxi, located in the south-western region of China. Results: Of the 755 detainees surveyed, 725 (96%) reported having a blood test in the labour camps of whom 493 (68%) thought this included an HIV test. 61 detainees self-reported they were HIV infected, their status confirmed by medical records, if available. Of these, 53 (87%) recalled receiving post-test HIV education, and 15 (25%) were currently receiving HIV antiretroviral therapy. Pretest education on HIV was provided to 233/725 (32%) detainees. The study further reports on detainees’ reactions and feelings towards non-disclosure and disclosure of their HIV test results in the labour camps. Conclusions: Mandatory testing is almost universal in the labour camps although a proportion of detainees were unaware that this included an HIV test. HIV test results should be disclosed to all labour camp detainees to reduce their distress of not knowing and prevent misconceptions about their HIV status. Labour camps provide another opportunity to implement universal treatment (‘Test and Treat’) to prevent the spread of HIV

Roll motion compensation by active marine gyrostabiliser

Unmanned Surface Vehicle (USV) has been gaining more marine applications nowadays. However, the USV is vulnerable to excessive rolling motions induced by water waves, and this phenomenon may cause significant downtime to the operations of USV and engender detrimental effects to the on-board instrument and sensors. Active control system had been proposed to compensate the rolling stability issue but most of the proposed devices were expensive. This paper developed a gyrostabiliser on USV model to compensate the excessive rolling motion. Gyrostabiliser consists of rotor, gimbal and spinning axes, which commonly used for measuring or maintaining orientations and angular velocities. The gyrostabiliser was mounted vertically inside the USV model. Experiments were conducted to obtain the ideal gains of gyrostabiliser’s controller, to investigate the differences between active- and passive-gyrostabiliser, and to identify the induced pitch effect of the vertical gyrostabiliser to the USV model. The roll angle of the USV was measured by gyro sensor, whereas the precession motor and flywheel motor were controlled by a non-encoder Direct-Current (DC) motor. A proportional controller of the gyrostabiliser was implemented through Arduino Integrated Development Environment (IDE) to ensure optimal performance of gyrostabiliser in precession speed and direction control. The results showed that both active- and passive-gyrostabiliser managed to mitigate the roll angle of USV from +/- 15° back to less than 1° and reached steady state within 2.32 seconds and 2.60 seconds, respectively. The active gyrostabiliser had advantage to return to zero precession angle while the passive gyrostabiliser accumulated 30° precession angle in the experiment. The induced pitch angle by the gyrostabiliser had been found in an insignificant magnitude for the case study. The outcomes of this paper lead to an alternative for improving the robustness of USV in rolling reduction. 

Roll motion compensation by active marine gyrostabiliser

922-929Unmanned Surface Vehicle (USV) has been gaining more marine applications nowadays. However, the USV is vulnerable to excessive rolling motions induced by water waves, and this phenomenon may cause significant downtime to the operations of USV and engender detrimental effects to the on-board instrument and sensors. Active control system had been proposed to compensate the rolling stability issue but most of the proposed devices were expensive. This paper developed a gyrostabiliser on USV model to compensate the excessive rolling motion. Gyrostabiliser consists of rotor, gimbal and spinning axes, which commonly used for measuring or maintaining orientations and angular velocities. The gyrostabiliser was mounted vertically inside the USV model. Experiments were conducted to obtain the ideal gains of gyrostabiliser’s controller, to investigate the differences between active- and passive-gyrostabiliser, and to identify the induced pitch effect of the vertical gyrostabiliser to the USV model. The roll angle of the USV was measured by gyro sensor, whereas the precession motor and flywheel motor were controlled by a non-encoder Direct-Current (DC) motor. A proportional controller of the gyrostabiliser was implemented through Arduino Integrated Development Environment (IDE) to ensure optimal performance of gyrostabiliser in precession speed and direction control. The results showed that both active- and passive-gyrostabiliser managed to mitigate the roll angle of USV from +/- 15° back to less than 1° and reached steady state within 2.32 seconds and 2.60 seconds, respectively. The active gyrostabiliser had advantage to return to zero precession angle while the passive gyrostabiliser accumulated 30° precession angle in the experiment. The induced pitch angle by the gyrostabiliser had been found in an insignificant magnitude for the case study. The outcomes of this paper lead to an alternative for improving the robustness of USV in rolling reduction

Assisted evolution enables HIV-1 to overcome a high trim5α-imposed genetic barrier to rhesus macaque tropism

Diversification of antiretroviral factors during host evolution has erected formidable barriers to cross-species retrovirus transmission. This phenomenon likely protects humans from infection by many modern retroviruses, but it has also impaired the development of primate models of HIV-1 infection. Indeed, rhesus macaques are resistant to HIV-1, in part due to restriction imposed by the TRIM5α protein (rhTRIM5α). Initially, we attempted to derive rhTRIM5α-resistant HIV-1 strains using two strategies. First, HIV-1 was passaged in engineered human cells expressing rhTRIM5α. Second, a library of randomly mutagenized capsid protein (CA) sequences was screened for mutations that reduced rhTRIM5α sensitivity. Both approaches identified several individual mutations in CA that reduced rhTRIM5α sensitivity. However, neither approach yielded mutants that were fully resistant, perhaps because the locations of the mutations suggested that TRIM5α recognizes multiple determinants on the capsid surface. Moreover, even though additive effects of various CA mutations on HIV-1 resistance to rhTRIM5α were observed, combinations that gave full resistance were highly detrimental to fitness. Therefore, we employed an 'assisted evolution' approach in which individual CA mutations that reduced rhTRIM5α sensitivity without fitness penalties were randomly assorted in a library of viral clones containing synthetic CA sequences. Subsequent passage of the viral library in rhTRIM5α-expressing cells resulted in the selection of individual viral species that were fully fit and resistant to rhTRIM5α. These viruses encoded combinations of five mutations in CA that conferred complete or near complete resistance to the disruptive effects of rhTRIM5α on incoming viral cores, by abolishing recognition of the viral capsid. Importantly, HIV-1 variants encoding these CA substitutions and SIVmac239 Vif replicated efficiently in primary rhesus macaque lymphocytes. These findings demonstrate that rhTRIM5α is difficult to but not impossible to evade, and doing so should facilitate the development of primate models of HIV-1 infection

Novel Escape Mutants Suggest an Extensive TRIM5α Binding Site Spanning the Entire Outer Surface of the Murine Leukemia Virus Capsid Protein

After entry into target cells, retroviruses encounter the host restriction factors such as Fv1 and TRIM5α. While it is clear that these factors target retrovirus capsid proteins (CA), recognition remains poorly defined in the absence of structural information. To better understand the binding interaction between TRIM5α and CA, we selected a panel of novel N-tropic murine leukaemia virus (N-MLV) escape mutants by a serial passage of replication competent N-MLV in rhesus macaque TRIM5α (rhTRIM5α)-positive cells using a small percentage of unrestricted cells to allow multiple rounds of virus replication. The newly identified mutations, many of which involve changes in charge, are distributed over the outer ‘top’ surface of N-MLV CA, including the N-terminal β-hairpin, and map up to 29 Ao apart. Biological characterisation with a number of restriction factors revealed that only one of the new mutations affects restriction by human TRIM5α, indicating significant differences in the binding interaction between N-MLV and the two TRIM5αs, whereas three of the mutations result in dual sensitivity to Fv1n and Fv1b. Structural studies of two mutants show that no major changes in the overall CA conformation are associated with escape from restriction. We conclude that interactions involving much, if not all, of the surface of CA are vital for TRIM5α binding

A two-stage ultrafiltration process for separating multiple components of Tetraselmis suecica after cell disruption

A two-stage ultrafiltration process was applied to the aqueous phase of Tetraselmis suecica after breaking its cell wall by high-pressure homogenization. Microscopic observation revealed that the cells were completely disrupted from 600 bar and cell fragmentation of the cells was also noticeable after 800 bar. In addition, the highest concentration of all the molecules of interest in the aqueous phase was observed at 1,000 bar and a temperature of 46 °C while preserving the integrity of the molecules of interest in the downstream process. After centrifugation, the aqueous phase was submitted to ultrafiltration through two consecutive membranes of different molecular weight cutoffs. Complete retention of starch was possible with a 100-kDa membrane and separation of sugars from proteins with a 10-kDa membrane on the remaining mixture. After testing the process with model solutions, the transmembrane pressure selected was 2.07 bar, which succeeded in retaining starch and pigments during the first part of the process, and proteins during the second part. A linear correlation between the permeate flux rate and the pressure was observed in both parts of the process

Conformational adaptation of Asian macaque TRIMCyp directs lineage specific antiviral activity

TRIMCyps are anti-retroviral proteins that have arisen independently in New World and Old World primates. All TRIMCyps comprise a CypA domain fused to the tripartite domains of TRIM5α but they have distinct lentiviral specificities, conferring HIV-1 restriction in New World owl monkeys and HIV-2 restriction in Old World rhesus macaques. Here we provide evidence that Asian macaque TRIMCyps have acquired changes that switch restriction specificity between different lentiviral lineages, resulting in species-specific alleles that target different viruses. Structural, thermodynamic and viral restriction analysis suggests that a single mutation in the Cyp domain, R69H, occurred early in macaque TRIMCyp evolution, expanding restriction specificity to the lentiviral lineages found in African green monkeys, sooty mangabeys and chimpanzees. Subsequent mutations have enhanced restriction to particular viruses but at the cost of broad specificity. We reveal how specificity is altered by a scaffold mutation, E143K, that modifies surface electrostatics and propagates conformational changes into the active site. Our results suggest that lentiviruses may have been important pathogens in Asian macaques despite the fact that there are no reported lentiviral infections in current macaque populations

Effects of anthropogenic activities on the heavy metal levels in the clams and sediments in a tropical river

The present study aimed to assess the effects of anthropogenic activities on the heavy metal levels in the Langat River by transplantation of Corbicula javanica. In addition, potential ecological risk indexes (PERI) of heavy metals in the surface sediments of the river were also investigated. The correlation analysis revealed that eight metals (As, Co, Cr, Fe, Mn, Ni, Pb and Zn) in total soft tissue (TST) while five metals (As, Cd, Cr, Fe and Mn) in shell have positively and significantly correlation with respective metal concentration in sediment, indicating the clams is a good biomonitor of the metal levels. Based on clustering patterns, the discharge of dam impoundment, agricultural activities and urban domestic waste were identified as three major contributors of the metals in Pangsun, Semenyih and Dusun Tua, and Kajang, respectively. Various geochemical indexes for a single metal pollutant (geoaccumulation index (I geo), enrichment factors (EF), contamination factor (C f) and ecological risk (Er)) all agreed that Cd, Co, Cr, Cu, Fe, Mn, Ni and Zn are not likely to cause adverse effect to the river ecosystem, but As and Pb could pose a potential ecological risk to the river ecosystem. All indexes (degree of contamination (C d), combined pollution index (CPI) and PERI) showed that overall metal concentrations in the tropical river are still within safe limit. River metal pollution was investigated. Anthropogenic activities were contributors of the metal pollution. Geochemical indexes showed that metals are within the safe limit