832 research outputs found
Jet pumps for thermoacoustic applications: design guidelines based on a numerical parameter study
The oscillatory flow through tapered cylindrical tube sections (jet pumps) is
characterized by a numerical parameter study. The shape of a jet pump results
in asymmetric hydrodynamic end effects which cause a time-averaged pressure
drop to occur under oscillatory flow conditions. Hence, jet pumps are used as
streaming suppressors in closed-loop thermoacoustic devices. A two-dimensional
axisymmetric computational fluid dynamics model is used to calculate the
performance of a large number of conical jet pump geometries in terms of
time-averaged pressure drop and acoustic power dissipation. The investigated
geometrical parameters include the jet pump length, taper angle, waist diameter
and waist curvature. In correspondence with previous work, four flow regimes
are observed which characterize the jet pump performance and dimensionless
parameters are introduced to scale the performance of the various jet pump
geometries. The simulation results are compared to an existing quasi-steady
theory and it is shown that this theory is only applicable in a small operation
region. Based on the scaling parameters, an optimum operation region is defined
and design guidelines are proposed which can be directly used for future jet
pump design.Comment: The following article has been accepted by the Journal of the
Acoustical Society of America. After it is published, it will be found at
http://scitation.aip.org/JAS
A numerical investigation on the vortex formation and flow separation of the oscillatory flow in jet pumps
A two-dimensional computational fluid dynamics model is used to predict the
oscillatory flow through a tapered cylindrical tube section (jet pump) placed
in a larger outer tube. Due to the shape of the jet pump, there will exist an
asymmetry in the hydrodynamic end effects which will cause a time-averaged
pressure drop to occur that can be used to cancel Gedeon streaming in a
closed-loop thermoacoustic device. The performance of two jet pump geometries
with different taper angles is investigated. A specific time-domain impedance
boundary condition is implemented in order to simulate traveling acoustic wave
conditions. It is shown that by scaling the acoustic displacement amplitude to
the jet pump dimensions, similar minor losses are observed independent of the
jet pump geometry. Four different flow regimes are distinguished and the
observed flow phenomena are related to the jet pump performance. The simulated
jet pump performance is compared to an existing quasi-steady approximation
which is shown to only be valid for small displacement amplitudes compared to
the jet pump length.Comment: The following article has been accepted by the Journal of the
Acoustical Society of America. After it is published, it will be found at:
http://scitation.aip.org/JAS
Robust process windows for Laser Induced Forward Transfer of thin film metal to create inter connects
Direct-write technologies can form a low-cost, alternative approach to create electrical interconnects by eliminating mask and etch costs. Also, direct-write is more efficient in creating complex structures as well as for producing small series. However, existing, industrially-mature direct-write technologies typically lack the resolution required for advanced IC packaging applications [1-4]. Laser Induced Forward Transfer (LIFT) is a direct write process which has been proven to be capable of patterning resolutions in the 1-5 μm range [5-8]. Thus far, a lack of deposition control resulting in contamination of the substrate has been a problem. The current paper shows an approach to come to a robust, contamination-free process window for LIFT of pure copper. Thus, we tackled a major roadblock towards the industrial feasibility of LIFT as a full metal direct-write technology that meets the current demands for IC packaging and integration
A Randomized Controlled Trial of Artemotil (Β-Arteether) in Zambian Children With Cerebral Malaria
The efficacy and safety of intramuscular artemotil (ARTECEF®) was compared to intravenous quinine in African children with cerebral malaria. This prospective block randomized open-label study was conducted at two centers in Zambia. Subjects were children aged 0 to 10 years of age with cerebral malaria and a Blantyre Coma Score of 2 or less. Ninety two children were studied; 48 received artemotil and 44 quinine. No significant differences in survival, coma resolution time, neurologic sequelae, parasite clearance time, and fever resolution time were seen between the two regimens. Rates for negative malaria smears one month after therapy were similar in both groups. Artemotil was a well-tolerated drug in the 48 patients in this study. It appears to be at least therapeutically equivalent to quinine for the treatment of pediatric cerebral malaria. It has the advantage of being able to be given intramuscularly once daily for only five days
Coamplification of DAD-R, SOX5, and EKI1 in human testicular seminomas, with specific overexpression of DAD-R, correlates with reduced levels of apoptosis and earlier clinical manifestation
Seminomas and nonseminomas represent the invasive stages of testicular
(TGCTs) of adolescents and adults. Although TGCTs are characterized by
extra copies of the short arm of chromosome 12, the genetic basis for gain
of 12p in the pathogenesis of this cancer is not yet understood. We have
demonstrated that gain of 12p is related to invasive growth and that
amplification of specific 12p sequences, i.e., 12p11.2-p12.1, correlates
with reduced apoptosis in the tumors. Here we show that three known genes
map within the newly determined shortest region of overlap of
amplification (SROA): DAD-R, SOX5, and EKI1. Whereas EKI1 maps close to
the telomeric region of the SROA, DAD-R is the first gene at the
centromeric region within the 12p amplicon. Although all three genes are
amplified to the same level within the SROA, expression of DAD-R is
significantly up-regulated in seminomas with the restricted 12p
amplification compared with seminomas without this amplicon. DAD-R is also
highly expressed in nonseminomas of various histologies and derived cell
lines, both lacking such amplification. This finding is of particular
interest because seminomas with the restricted 12p amplification and
nonseminomas are manifested clinically in the third decade of life and
show a low degree of apoptosis. In contrast, seminomas lacking a
restricted 12p amplification, showing significantly lower levels of DAD-R
with pronounced apoptosis, manifest clinically in the fourth decade of
life. A low level of DAD-R expression is also observed in normal
testicular parenchyma and in parenchyma containing the precursor cells of
this cancer, i.e., carcinoma in situ. Therefore, elevated DAD-R expression
in seminomas and nonseminomas correlates with invasive growth and a
reduced level of apoptosis associated with an earlier clinical
presentation. These data implicate DAD-R as a candidate gene responsible
in part for the pathological effects resulting from gain of 12p sequences
in TGCTs. In addition, our results also imply differences in expression
regulation of DAD-R between seminomas and nonseminomas
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