Sökresultat

Filtyp

Din sökning på "*" gav 529815 sökträffar

Experimental evidence for evaporation/condensation nonuniform flow in a horizontal aerosol generator

The formation of deposition patterns in the cooling zone during operation of a horizontal evaporation/condensation nanoparticle generator was studied to obtain information about flow conditions during particle formation. Quartz reactor tubes were used together with a simple light attenuation measurement to characterize deposition as a function of axial location. Results for the onset and pattern o

Twilight orientation to polarised light in the crepuscular dung beetle Scarabaeus zambesianus

The polarisation pattern of skylight offers many arthropods a reference for visual compass orientation. The dung beetle Scarabaeus zambesianus starts foraging at around sunset. After locating a source of fresh droppings, it forms a ball of dung and rolls it off at high speed to escape competition at and around the dung pile. Using behavioural experiments in the field and in the laboratory, we show

Short gamma-ray bursts in old populations: magnetars from white dwarf-white dwarf mergers

Recent progress on the nature of short-duration gamma-ray bursts has shown that a fraction of them originate in the local Universe. These systems may well be the result of giant flares from soft gamma-repeaters (highly magnetized neutron stars commonly known as magnetars). However, if these neutron stars are formed via the core collapse of massive stars then it would be expected that the bursts sh

Properties of RF bandpass amplifier topology with Q-enhancing

This paper describes a bandpass amplifier topology for the GHz range using Q-enhancing that allows a systematic design approach to be used to control linearity, noise and power consumption. Frequency selectivity is achieved by a negative feedback network using a LC tank and a positive feedback networks using a resistor to achieve Q-enhancing. The feedback networks are fully passive in order to min

Results of hip revision using the Exeter stem, impacted allograft bone, and cement

The Exeter stem and impacted, morselized allograft bone and cement were used in the revisions of 18 consecutive femoral components (17 patients). The primary arthroplasty had been done because of osteoarthritis. All of the femoral components were revised for the first time because of aseptic loosening. The migration pattern of the Exeter stem after revision was studied using roentgen stereophotogr

Physics based on electron beam ion traps

A brief description of the operational principles of an Electron Beam Ion Trap is given with specific reference to the currently under development/construction Shanghai EBIT. This is followed by an introduction to some of the frontier physics problems of highly charged ions that can be studied with such devices. Also a discussion of the use of EBITs as a powerful tool in hot-plasma diagnostics is

Accurate QM/MM free energy calculations of enzyme reactions: Methylation by catechol O-methyltransferase

We recently described a method to compute accurate quantum mechanical free energies [Rod, T. H.; Ryde, U. Phys. Rev. Lett. 2005, 94, `138302]. The method, which we term quantum mechanical thermodynamic cycle perturbation (QTCP), employs a molecular mechanics force field to sample phase space and, subsequently, a thermodynamic cycle to estimate QM/MM free energy changes. Here, we discuss the method

Effect of feed supplementation with phytohaemagglutinin in combination with alpha-ketoglutarate on growth and nitrogen elimination pathways in rats with acute renal failure induced by nephrectomy

Introduction: Phytohaemagglutinin (PHA) and alpha-ketoglutaric acid (AKG) in growing rats stimulate a change in the proportion of N excretion via urine and faeces, in favour of faecal excretion. The aim of the study was to investigate the effect of oral supplementation of PHA and AKG on pathways of nitrogen excretion and serum levels of urea in uraemic conditions induced by nephrectomy. Material a

Band Crossing Phenomena in N = Z Nuclei - A Probe to T=0 Pairing Correlations?

The structure of the N = Z nuclei Zn-60, Ga-62, Ge-64 and Kr-72 has been investigated at GASP. Total Routhian surface (TRS) calculations have been performed for the N = 36, 38 and 40 Kr isotones. In the case of Kr-72 the four quasi-particle g(9/2) alignment is observed to be significantly delayed in rotational frequency with respect to the heavier Kr isotopes. Such a delay contradicts the predicti

Cramer-Rao lower bounds for inverse scattering problems of multilayer structures

In this paper, the inverse scattering problem of amultilayer structure is analysed with the Fisher information matrix and the Cramer-Rao lower bound (CRLB). The CRLB quantifies the ill-posedness of the inverse scattering problem in terms of resolution versus estimation accuracy based on the observation of noisy data. The limit for feasible inversion is identified by an asymptotic eigenvalue analys

Monte Carlo study of TLD measurements in air cavities

Thermoluminescent dosimeters (TLDs) are used for verification of the delivered dose during IMRT treatment of head and neck carcinomas. The TLDs are put into a plastic tube, which is placed in the nasal cavities through the treated volume. In this study, the dose distribution to a phantom having a cylindrical air cavity containing a tube was calculated by Monte Carlo methods and the results were co

Deposition of HfO2 on InAs by atomic-layer deposition

Metal-oxide-semiconductor (MOS) capacitors are formed on bulk InAs substrates by atomic-layer deposition (ALD) of HfO2. Prior to film growth, InAs substrates receive a wet-chemical treatment of HCl, buffered HF (BHF), or (NH4)(2)S. Hafnium dioxide films are grown using 75 ALD cycles with substrate temperatures of 100, 200, and 300 degrees C. Substrate temperature is found to have a significant inf

Dynamics of FtsZ assembly during sporulation in Streptomyces coelicolor A3(2)

FtsZ, the bacterial tubulin homologue, is the main player in at least two distinct processes of cell division during the development of Streptomyces coelicolor A3(2). It forms cytokinetic rings and is required for the formation of both the widely spaced hyphal cross walls in the substrate mycelium and the specialized septation that converts sporogenic aerial hyphae into spores. The latter developm

Solar activity during the last 1000 yr inferred from radionuclide records

Identification of the causes of past climate change requires detailed knowledge of one of the most important natural factors—solar forcing. Prior to the period of direct solar observations, radionuclide abundances in natural archives provide the best-known proxies for changes in solar activity. Here we present two independent reconstructions of changes in solar activity during the last 1000 yr, wh

Neutralizing activity and cellular immune responses induced in mice after immunization with apoptotic HIV-1/murine leukemia virus infected cells

Dendritic cells present microbial antigens to T cells after uptake of apoptotic vesicles from infected cells. We previously reported that immunizations with apoptotic HIV-1/murine leukemia virus (MuLV) infected cells lead to induction of both cellular and humoral immune responses as well as resistance to mucosal challenge with live HIV-1/MuLV infected cells. Here we extended those studies and inve

Palaeomagnetism of Mesoproterozoic dykes from the Protogine Zone, southern Sweden and the enigmatic Sveconorwegian Loop

A palaeomagnetic study of samples from dykes in the Protogine Zone (PZ) south of Lake Vattern has yielded two characteristic magnetic components, A and B. A comparison with previous data and the Sveconorwegian Loop of the Fennoscandian Apparent Polar Wander Path (APWP) make it possible to estimate the age of the corresponding palaeomagnetic poles. They are situated close to the "Loop", which indic

Results of the first WHO international collaborative study on the standardization of the detection of antibodies to human papillomaviruses

Detection of genotype-specific human papillomavirus (HPV) capsid antibody in serum suggests past HPV infection. Also, these antibodies appear to correlate with vaccine-induced protection against infection, at least in animal models. However, each laboratory defines a reactive result differently and there is no agreed definition of what level of response indicates sero-reactivity. Standardization o

Camera Resectioning from a Box

In this paper we describe how we can do camera resectioning from a box with unknown dimensions, i.e. determine the camera model, assuming that image pixels are square. This assumption is equivalent to assuming that the camera as an aspect ratio of one and zero skew, and holds for most - if not all - digital cameras. Our proposed method works by first deriving 9 linear constraints on the projective