Normal Vacuum Research Articles

Subvacuum effects of the quantum field on the dynamics of a test particle

We study the effects of the electromagnetic subvacuum fluctuations on the dynamics of a nonrelativistic charged particle in a wavepacket. The influence from the quantum field is expected to give an additional effect to the velocity uncertainty of the particle. In the case of a static wavepacket, the observed velocity dispersion is smaller in the electromagnetic squeezed vacuum background than in the normal vacuum background. This leads to the subvacuum effect. The extent of reduction in velocity dispersion associated with this subvacuum effect is further studied by introducing a switching function. It is shown that the slow switching process may make this subvacuum effect insignificant. We also point out that when the center of the wavepacket undergoes non-inertial motion, reduction in the velocity dispersion becomes less effective with its evolution, no matter how we manipulate the nonstationary quantum noise via the choice of the squeeze parameters. The role of the underlying fluctuation–dissipation relation is discussed.

Antiangiogenic activity of extracts and fractions from an endemic plant Ardisia pyramidalis (Cav.) Pers. From Bataan, Philippines using Duck in ovo chorioallantoic membrane assay

Using bioassay directed fractionation, the angiosuppressive activity of leaf extracts ofArdisia pyramidalis (Myrsinaceae) was determined using the duck in ovo chorioallantoic membrane (CAM) assay. The methanol extract was antiangiogenic as indicated by the statistically significant lower blood vessel count compared with the negative control and the untreated eggs. The hexane partition was observed to be more angiosuppressive compared to the ethyl acetate counterpart. Fractionation by normal phase vacuum column chromatography revealed that the angiosuppressive agents were relatively non-polar. Hexane fraction 4 was the most potent. Further fractionation into subfractions 4.4.2 - 4.4.9 showed decreasing potency which was not comparable to the positive control. Subfractionation showed loss of antiangiogenic activity which may indicate synergistic effects in the parent fraction. Immunohistochemical assays and transmission electron microscopy results support the findings of the CAM assay. Key words: Antiangiogenic, Ardisia pyramidalis crude extracts, Ardisia pyramidalisfractions.

Chilling Resistance in Pomegranate Fruits with Spermidine and Calcium Chloride Treatments

Pomegranate fruits were treated with 2% calcium chloride in combination with 2 mM of spermidine by either normal dip or vacuum infiltration for 4 min and then stored at 2°C for 4 months. After 0, 30, 60, 90, and 120 days, 12 fruits were taken from each treatment and stored at 20°C for an additional 3 days. Compared with control fruits, significantly higher activities in catalase and superoxide dismutase and a lower activity in peroxidase were noted in treated fruits. It was found that antioxidant enzymes are responsible for inducing chilling tolerance in pomegranate fruits and spermidine in combination with calcium chloride can improve these enzymatic activities.

A new pseudo rubrene analogue with excellent film forming ability

A novel pseudo rubrene analogue, 6,11-di(thiophen-2-yl)-tetracene-5,12-dione (DTTDO) was synthesized, in which two thienyl groups and two carbonyl groups replacing four phenyl groups in the rubrene molecule were connected to the backbone of tetracene. This compound was characterized by single crystal X-ray structure analysis, thermogravimetric analysis, absorption spectra and electrochemical measurements. Unlike rubrene, DTTDO exhibited excellent film forming ability by normal vacuum deposition, indicating its promising applications in organic thin film transistors.

Time dependence and freezing-in of the electrode oxygen plasma-induced work function enhancement in polymer semiconductor heterostructures

Indium tin oxide (ITO), Au and Pt are materials of interest as high work function contacts for organic semiconductor devices. In this paper the relative energy level line-up of these materials is investigated both as bare surfaces or part of a polymer/conductor interface. Kelvin probe (KP) measurements show that the estimated work function for Au and Pt surfaces, evaporated under normal high vacuum (HV) fabrication conditions and measured in air, can be significantly lower (by ∼0.2 to 0.9 eV) than those of clean surfaces evaporated and measured in the more demanding and clean ultra high vacuum (UHV), that are often used as reference values. The work function of all surfaces increases significantly (from ∼0.4 to >1 eV) after an oxygen plasma, but then decreases upon air exposure, with different rates for different materials. The effect of the plasma wears off most rapidly for Au whilst it is more resilient for ITO. Most interestingly, via KP and electroabsorption measurements of the built-in potential on polymer/conductor and conductor/polymer/conductor structures, we demonstrate that a plasma-induced enhancement of the work function is “frozen in” by the application of a polymer semiconductor layer over the plasma-treated surfaces and can be made to last for years by proper device encapsulation. These results have strong implications on the understanding, fabrication, design and stability of organic semiconductor devices.

Electromagnetically induced transparency in squeezed vacuum

We studied the electromagnetically induced transparency, where the three-level atom of Λ-type is put in two statistically independent squeezed vacuums. We start from the master equation containing the decay of the atom to the squeezed vacuums, and solve the non-diagonal density matrix element analytically, finding that it is strongly dependent on the squeezing degree and the phase of the squeezed vacuum. There is also a dependence on the intensity and phase of the probe beam, which would not appear in the normal vacuum case. By coupling with squeezed vacuums, the atom would not only experience electromagnetically induced transparency and slow group velocity, but also induce a fast group velocity,backward group velocity and a gain in the probe light field. Besides, the absorption and gain can be modulated by the intensity of probe light.

Intrapartum risk factors for levator trauma

To determine intrapartum risk factors associated with levator trauma as identified by ultrasound imaging. A prospective observational study. Antenatal clinic of a tertiary hospital between May 2005 and February 2008. Nulliparous women (n=488) in their first ongoing pregnancy. An interview and four-dimensional translabial ultrasound was carried out between 36 and 38 weeks and again 3-4 months after delivery. Obstetric data were collected from the hospital database and/or participants' records. Levator macrotrauma ('avulsion') and microtrauma (irreversible overdistension). A total of 367 women (75%) returned for the postpartum assessment after normal vaginal delivery (n=187, 51%), vacuum (n=34, 9%), forceps (n=20, 5%) and caesarean section (n=126, 34%). Median follow up was 4.08 months (interquartile range 3.68-5.03 months). Levator avulsion was diagnosed in 32 (13%) of the women who delivered vaginally and in none of the caesarean section group regardless of indication. On multivariable regression forceps delivery was significantly associated with avulsion (P=0.01; OR 3.83; 95% CI 1.34-10.94). Using >20% peripartum increase in hiatal area on Valsalva as the cutoff, 28.5% of vaginally parous women were shown to have suffered irreversible overdistension. This was positively associated with the length of second stage (P=0.001; OR 1.01 per minute; 95% CI 1.0-1.02). Intrapartum epidural appeared to have a protective effect (P=0.03; OR 0.42; 95% CI 0.19-0.93). Levator trauma at the time of first delivery is associated with vaginal delivery, forceps and a longer second stage. Epidural pain relief may exert a protective effect.

Aligning electronic energy levels at theTiO2/H2Ointerface

The electronic energy levels of a model titanium dioxide water interface computed using the Perdew-Burke-Ernzerhof (PBE) density functional are positioned relative to the normal hydrogen electrode and vacuum. As energy reference we use the solvation free energy of the ${\text{H}}^{+}$ ion computed by reversible insertion of a proton in the aqueous part of the model system. The interaction with water raises the energy levels bringing the conduction-band edge in fair alignment with experiment. The error in the PBE band gap must therefore be largely attributed to underestimation of the ionization potential.

The ameliorative effects of spermidine and calcium chloride on chilling injury in pomegranate fruits after long-term storage

Introduction . Pomegranate fruits (Punica granatum L.) are chilling-sensitive crops. Materials and methods . Pomegranate fruits were treated with calcium chloride and spermidine, alone or in combination, by normal dip and vacuum infiltration methods. The treated fruits were stored at 2 °C for 4 months. At the end of the storage period, samples were held for 3 days at 20 °C, then the qualitative constituents were evaluated. Results and discussion . Treated fruits exhibited less weight loss and higher juice content than control fruits. Non-treated fruits developed chilling injury manifested as an increase in K+ leakage and polyphenol oxidase activity. Calcium chloride and spermidine treatments resulted in lower soluble solid content, but some fruits showed higher titratable acidity. All treatments significantly increased ascorbic acid content. The pH of aril juice in treated fruits was lower than that of non-treated fruits, probably due to higher titratable acidity. Total antioxidant activity and total phenolic content increased in treated fruits. In our study, a correlation was observed between total phenolic content and total antioxidant activity. Conclusion . The treatments applied in our experiments maintained overall quality of pomegranate fruits during long-term storage. Postharvest application of calcium and spermidine either alone or in combination could ameliorate adverse effects of low temperature on pomegranate fruit quality during cold storage. Vacuum infiltration was as effective as the normal dip method. However, normal dip is a simpler and faster treatment method.

Nuclear matter and finite nuclei in an effective chiral model

We systematically investigate the vacuum stability and nuclear properties in the effective chiral model with higher-order terms in $\ensuremath{\sigma}$. We evaluate the model parameters by considering the saturation properties of nuclear matter as well as the normal vacuum to be globally stable at zero and finite baryon densities. We find parameter sets giving moderate equations of state and apply these models to finite nuclei.

Rate modeling of CO 2 stripping from potassium carbonate promoted by piperazine

This work presents results from a rate-based model of strippers at normal pressure (160 kPa) and vacuum (30 kPa) in Aspen Custom Modeler ® (ACM) for the desorption of CO 2 from 5 m K +/2.5 m piperazine (PZ). The model solves the material, equilibrium, summation and enthalpy (MESH) equations, the heat and mass transfer rate equations, and computes the reboiler duty and equivalent work for the stripping process. Simulations were performed with IMTP #40 random packing and a temperature approach on the hot side of the cross-exchanger of 5 °C and 10 °C. A “short and fat” stripper requires 7–15% less total equivalent work than a “tall and skinny” one because of the reduced pressure drop. The vacuum and normal pressure strippers require 230 s and 115 s of liquid retention time to get an equivalent work 4% greater than the minimum work. Stripping at 30 kPa was controlled by mass transfer with reaction in the boundary layer and diffusion of reactants and products (88% resistance at the rich end and 71% resistance at the lean end). Stripping at 160 kPa was controlled by mass transfer with equilibrium reactions (84% resistance at the rich end and 74% resistance at the lean end) at 80% flood. The typical predicted energy requirement for stripping and compression to 10 MPa to achieve 90% CO 2 removal was 37 kJ/gmol CO 2. This is about 25% of the net output of a 500 MW power plant with 90% CO 2 removal.

Squeezed vacuum, coherent and dc field effects on optical multistability via decay-induced quantum beats

Effect of the relative control phase as well as the squeezed phase parameter on the optical switching process of the optical bi-multistable behaviour are investigated in detail for a four-level Y-type atomic system; in the presence of a control field (coherent + dc fields) with squeezed vacuum field and quantum interference from spontaneous emission. The results indicated that (a) the quantum interference assists to decrease the rate of switching via the relative phase of the control field and makes the switching on/off points more rapid in squeezed vacuum compared to a normal vacuum case, and (b) the phase switching effects between the output field and the relative control phase increases the switching on/off processes in normal vacuum more than the squeezed vacuum case. In addition, we have demonstrated the possibility of displaying quantum beats with a novel type of bi-multistable behaviour in the cooperative switching diagram.

Tunnelling cooling by a normal–vacuum–superconductor junction

Photoabsorption properties of green and red fluorescent protein chromophore anions in vacuo were investigated theoretically, based on the experimental results in gas phase [Phys. Rev. Lett. 2001, 87, 228102; Phys. Rev. Lett. 2003, 90, 118103]. Their calculated transition energies in absorption with TD-DFT and ZINDO methods are directly compared to the experimental reports in gas phase, and the calculations with ZINDO method can correctly reproduce the absorption spectra. The orientation and strength of their transition dipole moments were revealed with transition density. We also showed the orientation and result of their intramolecular charge transfer with transition difference density. The calculated results show that with the increase of the extended conjugated system, the orientation of transition dipole moments and the orientation of charge transfer can be reversed. They are the linear responds with the external electric fields. These theoretical results reveal the insight understanding of the photoinduced dynamics of green and red fluorescent protein chromophore anions and cations in vacuo. (c) 2007 Elsevier B.V. All rights reserved.

Effects of a squeezed-vacuum reservoir on geometric phase

Geometric phase, for a two-level atom in an electromagnetic field interacting with a squeezed-vacuum reservoir, is calculated by establishing connecting density matrices, describing an evolution of a quantum open system, with a nonunit vector ray in a complex projective Hilbert space. Because the geometric phase depends only on the smooth curve on this space, it is formulated entirely in terms of geometric structures. The results show that the geometric phase for the squeezed-vacuum reservoir has fully different behavior in comparison with one for the normal vacuum reservoir.

A TEST OF THE REFRACTIVE INDEX IN A STRONG ELECTROMAGNETIC FIELD

A strong electromagnetic field may modify the refractive index of the normal vacuum due to nonlinear effects caused by photon-photon interactions. In order to test the increase of the refractive index, Cherenkov radiations associated with relativistic electrons into the strong electromagnetic field can be utilized as an experimental probe. We will present a result of the experimental search for the Cherenkov emissions with a laser intensity of 1017W/cm2 with the wavelength of 800nm and the electron beam of 35.4MeV/c, where photons with kinematically expected Compton energies and a symptom of visible ray emissions were observed.

Stability of the normal vacuum in multi-Higgs-doublet models

We show that the vacuum structure of a generic multi-Higgs-doublet model shares several important features with the vacuum structure of the two and three Higgs-doublet model. In particular, one can still define the usual charge breaking, spontaneous $CP$ breaking, and normal (charge and $CP$ preserving) stationary points. We analyze the possibility of charge or spontaneous $CP$ breaking by studying the relative depth of the potential in each of the possible stationary points.

A Chiral Symmetric Relativistic Mean Field Model with a Logarithmic sigma Potential

We develop a chiral symmetric relativistic mean field model with a logarithmic sigma potential derived in the strong coupling limit of lattice QCD. We find that both nuclear matter and finite nuclei are accurately described by the present model. The normal vacuum is found to be globally stable at zero and finite baryon densities, and an equation of state with moderate stiffness (K � 280 MeV) is obtained. The binding energies and charge radii of Z closed even-even nuclei are accurately predicted over a wide mass range from C to Pb isotopes, except for underestimates of the binding energies for several jj closed nuclei.

Laboratory-scale experiments applied to the design of a two-stage submerged combustion evaporation system

To simulate a submerged combustion evaporation (SCE) process under laboratory conditions, this study conducted three kinds of indirect-heating evaporation experiments, including normal evaporation, vacuum evaporation, and gas-carrying evaporation experiments on mature municipal solid waste (MSW) landfill leachate. The results showed that the organic concentrations in terms of COD in condensates were always very high at the beginning, then decreased rapidly, and stabilized at a low level, which suggests that only the forepart of vapors need to be safely treated to control the discharge of organic pollutants. This study applied the process in developing a two-stage SCE system, which has been implemented for the treatment of biologically pretreated and concentrated leachate from Membrane Bioreactor (MBR) and Reverse Osmosis (RO) combined process in the Beishenshu MSW Landfill, Beijing, China. The result shows that the two-stage SCE system can successfully further concentrate refractory organic matter in concentrated leachate and remove volatile organics from the vapor.

Microstructure and mechanical properties of WC-20wt% Co/ZrO 2(3Y) cermet composites

The cermet composites WC-20wt%Co/ZrO 2(3Y) with four different contents of ZrO 2(3Y) were prepared by normal vacuum sinter processing; the optical microscope and SEM were used to characterize their microstructures. The hardness, bending strength and impact toughness of the specimens were determined. The experimental results show that ZrO 2(3Y) particles in WC-20wt%Co matrix are spherical particles in different sizes which are distributed uniformly in Co phases and WC phases, the bending strength and impact toughness of the WC-20wt%Co cermet composites added ZrO 2(3Y) improve remarkably, but the hardness values have little change.

Drying of Guava and Papaya: Impact of Different Drying Methods

Heat pump dryers (HPD) are known as high-energy-efficiency devices with low economic cost. As it is usually a closed system, the drying media can be substituted by inert gases. In this study, the effect of nitrogen and carbon dioxide on guava and papaya were investigated. Both drying kinetics and quality of these dried fruits resulting from the two methods were compared with normal air HPD, vacuum dryer, and freeze dryer. When using CO2, the effective diffusivity during the drying process was 44% higher in guava and 16.34% higher in papaya. There was less browning, faster rehydration, and more vitamin C retention in the final products. All these reveal the great potential of modified atmosphere heat pump dryer in the food drying industry.