Restoration of blood pressure by choline treatment in rats made hypotensive by haemorrhage

1. Intracerebroventricular (i.c.v.) injection of choline (25-150 micrograms) increased blood pressure in rats made acutely hypotensive by haemorrhage. Intraperitoneal administration of choline (60 mg kg-1) also increased blood pressure, but to a lesser extent. Following i.c.v. injection of 25 micrograms or 50 micrograms of choline, heart rate did not change, while 100 micrograms or 150 micrograms i.c.v. choline produced a slight and short lasting bradycardia. Choline (150 micrograms) failed to alter the circulating residual volume of blood in haemorrhaged rats. 2. The pressor response to i.c.v. choline (50 micrograms) in haemorrhaged rats was abolished by pretreatment with mecamylamine (50 micrograms, i.c.v.) but not atropine (10 micrograms, i.c.v.). The pressor response to choline was blocked by pretreatment with hemicholinium-3 (20 micrograms, i.c.v.). 3. The pressor response to i.c.v. choline (150 micrograms) was associated with a several fold increase in plasma levels of vasopressin and adrenaline but not of noradrenaline and plasma renin. 4. The pressor response to i.c.v. choline (150 micrograms) was not altered by bilateral adrenalectomy, but was attenuated by systemic administration of either phentolamine (10 mg kg-1) or the vasopressin antagonist [beta-mercapto-beta,beta-cyclopenta-methylenepropionyl1, O-Me-Tyr2,Arg8]-vasopressin (10 micrograms kg-1). 5. It is concluded that the precursor of acetylcholine, choline, can increase and restore blood pressure in acutely haemorrhaged rats by increasing central cholinergic neurotransmission. Nicotinic receptor activation and an increase in plasma vasopressin and adrenaline level appear to be involved in this effect of choline.     

Phase transition of LCP fluids confined in nanochannels through MD simulation

Manipulation of molecular orientation alignment in MCTLCPs (main-chain thermotropic liquid crystalline polymers) by pure shear at nano scale has been investigated for the first time using molecular dynamics (MD) simulation. Results indicate that high planar shear induces long-range uniform orientation ordering (liquid crystalline phase) of initially randomly orientated molecules of MCTLCP fluid confined in a nanochannel, which is confirmed by analyzing the orientation order parameter and the snapshots of MCTLCP liquid in a nanochannel under different shear rates. Insights into the origin of the phase transition phenomena are given at molecular level through investigating the thermodynamic density distribution of MCTLCP molecules in the nanochannel, suggesting that the energy shift due to a radical jump of system density affects both the magnitude and the orientation of the molecular ordering. Simulation results also show that there is a critical shear rate for transforming isotropic phase into liquid crystalline phase. The critical shear rate is dependent on the temperature of the MCTLCP system. Findings in this paper may present useful information for processing TLCP molecules at nano scale and the understanding of nanoflow.     

Traveling-wave piezoelectric linear motor Part I: the stator design.

A new type of piezoelectric linear motor incorporating a traveling wave has been developed. The linear motor is comprised of a stator and a carriage. The stator design, which consists of a meander-line structure and gear teeth mounted on the meander-line structure, is the focus of this article. The meander-line structure is constructed with bimorph actuators arranged in a line. These actuators are driven by two phased sets of alternating current (ac) in order to generate a traveling wave. The traveling wave is transferred to the gear teeth, by which the carriage is driven. Modeling of the stator is derived by use of a strain energy method. The performance of various materials is evaluated by analytical and experimental methods. The analytical and the experimental results are quite approximate. Modal analysis is investigated using ANSYS. Appropriate modes associated with ultrasonic levels of resonant frequency are selected to obtain desired motion and to enhance the output performance. Surface speed for various applied input voltage are studied and indicate a nearly linear relationship. The stator in combination with the carriage makes up the linear motor.     

FluNet: A hybrid internet simulator for fast queue regimes

Motivated by the scale and complexity of simulating large-scale networks, recent research has focused on hybrid fluid/packet simulators, where fluid models are combined with packet models in order to reduce simulation complexity as well as to track dynamics of end-sources accurately. However, these simulators still need to track the queuing dynamics of network routers, leading to considerable simulation complexity in a large-scale network model. In this paper, we propose a new hybrid simulator – FluNet – where queueing dynamics are not tracked, but instead, an equivalent rate-based model is used. The FluNet simulator is predicated on a fast-queueing regime at bottleneck routers, where the queue length fluctuates on a faster time-scale than end systems. This allows us to simulate large-scale systems, where the simulation “time step-size” is governed only by the time-scale of the end-systems, and not by that of the intermediate routers; whereas a queue-tracking based fluid simulator would require decreasingly smaller step-sizes as the system scale size increases. We validate our model using a ns-2 based implementation. Our results indicate a good match between packet systems and the associated FluNet system.     

The crystal structure of an Fe-superoxide dismutase from the hyperthermophile Aquifex pyrophilus at 1.9 A resolution: structural basis for thermostability

The incidence of stress fractures is increasing among competitive and recreational athletes as well as among children and the elderly. By understanding the continuum of bone's response to stress and maintaining an appropriate index of suspicion, the health care provider can diagnose these injuries appropriately. An accurate history and examination is essential and will differentiate stress fractures from other stress reactions. The more common stress fractures are discussed.     

Single-strand conformational polymorphism analysis of the M(r) 170,000 isozyme of DNA topoisomerase II in human tumor cells

Five cell lines selected for resistance to the cytotoxicity of inhibitors of DNA topoisomerase II have point mutations in the gene that codes for the M(r) 170,000 form of this enzyme. In each case, the mutation results in an amino acid change in or near an ATP binding sequence of the M(r) 170,000 isozyme of topoisomerase II. We used single-strand conformational polymorphism analysis to screen for similar mutations in other drug-resistant cell lines or in leukemic cells from patients previously treated with etoposide or teniposide. We also analyzed the region of the gene that codes for amino acids adjacent to the tyrosine at position 804 of topoisomerase II which binds covalently to DNA. CEM/VM-1, CEM/VM-1-5, and HL-60/AMSA human leukemic cell lines were used as controls; 3 of 3 known mutations were detected by migration differences of polymerase chain reaction products from the RNA extracted from these three lines. A previously unknown mutation was found in the tyrosine 804 region of the M(r) 170,000 topoisomerase II expressed by CEM/VM-1 and CEM/VM-1-5 cells. Sequence analysis showed that substitution of a T for a C at nucleotide 2404 resulted in an amino acid change of a serine for a proline at amino acid 802. No mutations in any of the ATP binding sequences or in the tyrosine 804 region were detected in polymerase chain reaction products from RNA extracted from human leukemia HL-60/MX2 or CEM/MX1 cells (both cell lines selected for resistance to mitoxantrone) or in human myeloma 8226/Dox1V cells (selected for resistance by simultaneous exposure to doxorubicin and verapamil). No mutations were detected in polymerase chain reaction products from RNA extracted from blasts of 15 patients with relapsed acute lymphocytic leukemia, previously treated with etoposide or teniposide. We conclude that: (a) single-strand conformational polymorphism analysis is useful for screening for mutations in topoisomerase II; (b) resistance to the cytotoxicity of inhibitors of DNA topoisomerase II is not always associated with mutations in ATP binding sequences or the active site tyrosine region of M(r) 170,000 topoisomerase II; and (c) mutations similar to those detected in drug resistant cells selected in culture have not been identified in blast cells from patients with relapsed acute lymphocytic leukemia, previously treated with etoposide or teniposide.     

Onset of gas self-induction and power consumption after gas induction in an agitated tank

The behavior of inducted gas from liquid surface and the; power requirements in an agitated tank using a mechanical agitator are studied in order to increase the amount of gas self-induction and the gas retention time for gas absorption. A 45° six-blade downward impeller turbine was utilized in this study. Air and water, air and 40 wt% 60 wt%, and 80 wt% of glycerin water, and air and 106 cP silicon oil were employed as gas and liquid phases. Variables which were studied included geometrical factors (immersed depth of impeller, baffle with and diameter of impeller) and the physical properties of the liquid (viscosity, density, and surface tension). The correlations for the onset speed of impeller and power consumption after gas induction in the agitated tank are established from our experimental results. The amount of gas self-induction from the liquid surface in the agitated tank increases with increasing impeller diameter and speed and decreases with increasing baffle width, depth of impeller and viscosity of liquid.     

Synthesis and characterization of novel copolymers with the trimethylsilyl group for deep‐UV photoresists

N‐(4‐Acetoxyphenyl) maleimide (APMI) and three kinds of comonomers bearing a trimethylsilyl group were copolymerized at 60°C in the presence of azobisisobutyronitrile (AIBN) as an initiator in 1,4‐dioxane to obtain the three IP, IIP, and IIIP copolymers. These copolymers were removed from the acetoxy group in a transesterification process into new IVP, VP, and VIP copolymers with a pendant hydroxyl group. Two modified processes were adopted to prepare photoresists using these copolymers. The first process involved mixing the dissolution inhibitor, o‐nitrobenzyl cholate, with the new copolymers. Second, o‐nitrobenzyl cholate was introduced into the copolymers using 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) in dimethylformamide (DMF). The cyclic maleimide structure is responsible for the high thermal stability of these copolymers. After irradiation using deep–UV light and development with aqueous Na₂CO₃ (0.01 wt %), the developed patterns showed positive images and exhibited good adhesion to the silicon wafer without using any adhesion promoter. The resolution of these resists was at least 0.8 μm and an oxygen‐plasma etching rate was 1/5.3 to that of hard‐baked HPR‐204. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2791–2798, 2002; DOI 10.1002/app.10255     

Annular slot-coupled dielectric resonator antenna

An annular slot-coupled dielectric resonator antenna is investigated experimentally. As compared with the previous rectangular-slot version, the new configuration offers a much wider bandwidth of 18%. The return loss, radiation patterns, and antenna gain of the configuration have been measured and are discussed