Mixing and transient interface condensation of a liquid hydrogen tank

Experiments were conducted to investigate the effect of axial jet-induced mixing on the pressure reduction of a thermally stratified liquid hydrogen tank. The tank was nearly cylindrical, having a volume of about 0.144 cu m with 0.559 m in diameter and 0.711 m long. A mixer/pump unit, which had a jet nozzle outlet of 0.0221 m in diameter was located 0.178 m from the tank bottom and was installed inside the tank to generate the axial jet mixing and tank fluid circulation. The liquid fill and jet flow rate ranged from 42 to 85 percent (by volume) and 0.409 to 2.43 cu m/hr, respectively. Mixing tests began with the tank pressure ranging from 187.5 to 238.5 kPa at which the thermal stratification results in 4.9 to 6.2 K liquid sub cooling. The mixing time and transient vapor condensation rate at the liquid-vapor interface are determined. Two mixing time correlations, based on the thermal equilibrium and pressure equilibrium, are developed. Both mixing time correlations are expressed as functions of system and buoyancy parameters and compared well with other experimental data. The steady state condensation rate correlation of Sonin et al. based on steam-water data is modified and expressed as a function of jet subcooling. The limited liquid hydrogen data of the present study shows that the modified steady state condensation rate correlation may be used to predict the transient condensation rate in a mixing process if the instantaneous values of jet sub cooling and turbulence intensity at the interface are employed

Characterization of novel beta-galactosidase activity that contributes to glycoprotein degradation and virulence in Streptococcus pneumoniae.

The pneumococcus obtains its energy from the metabolism of host glycosides. Therefore, efficient degradation of host glycoproteins is integral to pneumococcal virulence. In search of novel pneumococcal glycosidases, we characterized the Streptococcus pneumoniae strain D39 protein encoded by SPD_0065 and found that this gene encodes a beta-galactosidase. The SPD_0065 recombinant protein released galactose from desialylated fetuin, which was used here as a model of glycoproteins found in vivo. A pneumococcal mutant with a mutation in SPD_0065 showed diminished beta-galactosidase activity, exhibited an extended lag period in mucin-containing defined medium, and cleaved significantly less galactose than the parental strain during growth on mucin. As pneumococcal beta-galactosidase activity had been previously attributed solely to SPD_0562 (bgaA), we evaluated the contribution of SPD_0065 and SPD_0562 to total beta-galactosidase activity. Mutation of either gene significantly reduced enzymatic activity, but beta-galactosidase activity in the double mutant, although significantly less than that in either of the single mutants, was not completely abolished. The expression of SPD_0065 in S. pneumoniae grown in mucin-containing medium or tissues harvested from infected animals was significantly upregulated compared to that in pneumococci from glucose-containing medium. The SPD_0065 mutant strain was found to be attenuated in virulence in a manner specific to the host tissue

Gamma Radiation Shielding Properties of Slag and Fly Ash-based Geopolymers

Industrial waste-based geopolymer cement is a greener alternative to Ordinary Portland Cement (OPC) for radiation shielding with comparable mechanical properties without the production of CO2 during synthesis. In this paper, the linear attenuation coefficient of slag and fly ash-based geopolymers, unmodified by aggregates, is measured and used to calculate the mass attenuation coefficients, half-value layer (HVL), and tenth-value layer (TVL) of the geopolymers. Narrow Beam Gamma Spectrometry with gamma energy of 0.662 MeV, 1.173 MeV, and 1.332 MeV was used to irradiate a series of slag and fly ash-based geopolymer paste of cylindrical shape with a diameter of 7.5 cm and height of 9.5 cm. Slag geopolymer has linear attenuation coefficient of 0.1642/cm, 0.1237/cm, 0.1150/cm, mass attenuation coefficient of 0.0782 cm2/g, 0.0589 cm2/g, 0.0548 cm2/g, the HVL of 4.222 cm, 5.609 cm, 6.056 cm, and TVL of 14.025 cm, 18.633 cm, 20.118 cm, respectively. Fly ash geopolymer has linear attenuation coefficient of 0.1387/cm, 0.1075/cm, and 0.0964/cm, mass attenuation coefficient of 0.0761 cm2/g, 0.0589 cm2/g, 0.0529 cm2/g, HVL of 4.998 cm, 6.453 cm, 7.202 cm, and TVL of 16.603 cm, 21.437 cm, 23.926 cm, respectively. Test samples made from slag-based geopolymers have a better shielding capability compared to fly ash-based geopolymers due to having higher attenuation coefficients as well as lower HVL and TVL, thus requiring less material to absorb radiation of the same energy level

Hubungan Keberadaan Jentik Aedes Aegypti dan Pelaksanaan 3m Plus dengan Kejadian Penyakit Dbd di Lingkungan XVIII Kelurahan Binjai Kota Medan Tahun 2012

The relation of Aedes aegypti larva existence and 3M Plus implementation with DHF disease in Area XVIII Binjai District Medan. Medan is one of DHF endemic area and the most endemic subdistrict is Medan Denai Subdistrict. The most effective way to eradicate DHF disease is with eradicating mosquito nest or PSN DBD, so that is important to know the Aedes aegypti larva existence and effectiveness of 3M Plus implementation.This research aims to know the relation of Aedes aegypti larva existence and 3M Plus implementation with DHF disease. The research location is in Area XVIII Binjai District Medan Denai Subdistrict. This research samples are 100 housewive, that is taken by purposive sampling technique. This research is analytic survey with cross sectional design study using Exact Fisher test.Results showed that the House Index value is 5%, Container Index is 4%. 3M Plus implementation that includes to good category 78% and bad 22% . The relation of Aedes aegypti larva existence with DHF disease has p=0,002. The relation of 3M Plus implementation with DHF disease has p=0,047. From the results, it can be known that there is relation of Aedes aegypti larva existence and 3M Plus implementation with DHF disease in Area XVIII Binjai District. It is suggested to Medan Health Department and Desa Binjai Health Service Center to socialize to do eradicating Aedes aegypti mosquito nest or PSN DBD regularly to decrease the number of DHF disease in Binjai District especially in Area XVIII

Appetite for self-destruction: suicidal biting as a nest defense strategy in Trigona stingless bees

Self-sacrificial behavior represents an extreme and relatively uncommon form of altruism in worker insects. It can occur, however, when inclusive fitness benefits are high, such as when defending the nest. We studied nest defense behaviors in stingless bees, which live in eusocial colonies subject to predation. We introduced a target flag to nest entrances to elicit defensive responses and quantified four measures of defensivity in 12 stingless bee species in São Paulo State, Brazil. These included three Trigona species, which are locally known for their aggression. Species varied significantly in their attack probability (cross species range = 0–1, P < 0.001), attack latency (7.0–23.5 s, P = 0.002), biting duration of individual bees (3.5–508.7 s, P < 0.001), and number of attackers (1.0–10.8, P < 0.001). A “suicide” bioassay on the six most aggressive species determined the proportion of workers willing to suffer fatal damage rather than disengage from an intruder. All six species had at least some suicidal individuals (7–83 %, P < 0.001), reaching 83 % in Trigona hyalinata. Biting pain was positively correlated with an index of overall aggression (P = 0.002). Microscopic examination revealed that all three Trigona species had five sharp teeth per mandible, a possible defensive adaptation and cause of increased pain. Suicidal defense via biting is a new example of self-sacrificial altruism and has both parallels and differences with other self-sacrificial worker insects, such as the honey bee. Our results indicate that suicidal biting may be a widespread defense strategy in stingless bees, but it is not universal

Exciton energy transfer in nanotube bundles

Photoluminescence is commonly used to identify the electronic structure of individual nanotubes. But, nanotubes naturally occur in bundles. Thus, we investigate photoluminescence of nanotube bundles. We show that their complex spectra are simply explained by exciton energy transfer between adjacent tubes, whereby excitation of large gap tubes induces emission from smaller gap ones via Forster interaction between excitons. The consequent relaxation rate is faster than non-radiative recombination, leading to enhanced photoluminescence of acceptor tubes. This fingerprints bundles with different compositions and opens opportunities to optimize them for opto-electronics.Comment: 5 pages, 5 figure

Effects of Contact History and Family Income on The Risk of Pulmonary Tuberculosis in Padangsidimpuan, North Sumatera

Background: Tuberculosis (TB) remains one of the world’s deadliest communicable diseases. In 2016, 10.4 million people fell ill with TB, and 1.7 million died from the disease (including 0.4 million among people with HIV). Over 95% of TB deaths occur in low and middle-income countries. Seven countries account for 64% of the total, with India leading the count, followed by Indonesia, China, Philippines, Pakistan, Nigeria, and South Africa. Given that most deaths from TB are preventable, the death toll from the disease is still unacceptably high and efforts to combat it must be accelerated. This study aimed to determine the effects of con¬tact history and family income on the risk of pulmonary TB in Padangsidimpuan, North Sumatera. Subejcts and Method: This was a case control study conducted at several Puskesmas (Community Health Center) in Padangsidimpuan, North Sumatera. A total of 90 patients consisting of 45 TB cases and 45 controls were selected for this study. The dependent variable was pulmonary TB. The independent variables were contact history and family income. Pulmonary TB cases were determined by sputum acid fast tuberculosis (AFT) bacilli test. The other data were collected by questionnaire. The data were analyzed by a multiple logistic regression. Results: The risk of pulmonary TB increased with history of TB contact (OR= 4,01; 95% CI= 1.67 to 9.66; p= 0.002) and low family income (OR= 2.53; 95% CI= 1.07 to 5.9; p= 0.033). Conclusion: The risk of pulmonary TB increases with history of TB contact and low family income. Keywords: pulmonary tuberculosis, tuberculosis contact, family income