Little Change In Shape Research Articles

Evolution of equilibrium particle beams in plasma under external wakefields

A beam of ultrarelativistic charged particles in a plasma can reach equilibrium with its own radial wakefield and then propagate with little change in shape. If some co-moving perturbation appears ahead of the beam, it may or may not destroy the beam with its wakefield, depending on the phase and amplitude of the wakefield. We numerically study which perturbations can destroy a single short bunch or a train of many short bunches at the parameters of interest for plasma wakefield acceleration in an axisymmetric configuration, and how fast. We find that there are particularly dangerous wakefield phases in which the beam can be destroyed by perturbations of very low amplitude. We also find that perturbations with an amplitude larger than the wakefield of a single bunch in the train are always destructive.

Projected changes in extreme warm and cold temperatures in China from 1.5 to 5°C global warming

AbstractLinking regional extreme temperature changes to global warming levels is important for understanding the impacts of global emission targets on regional climate. Here, we investigate how the temperature extremes in China change with different global warming levels using large ensemble runs from Canadian Earth System Model version 2. With the global mean near‐surface temperature increasing from 1.5 to 5°C above the preindustrial level, the absolute intensity of the warmest and coldest temperatures in China will change linearly, while the percentile‐based frequency of warm and cold temperatures will change nonlinearly. All the changes in the intensity and the frequency show clear regional differences, with the most obvious changes observed in northeastern China. The probability distribution functions (PDFs) for the intensity indices show clear shifts but with little change in shape, while the PDFs for the frequency indices show changes in both position and shape. Quantified analyses of risk ratio show that the risk changes in the frequency of temperature extremes will be larger than those for the intensity indices. The changes in the nighttime extremes are faster than those in the daytime extremes. The rarer the event is, the larger the change in the risk ratio. At the 2°C warming level, the cold days and nights with return periods of 5, 10, and 50 years in the current climate will become almost disappeared. At the 3°C level and beyond, the once‐in‐5‐year, 10‐year and 50‐year warm events in the current climate will occur every year.

Wave packet dynamics for Gross–Pitaevskii equation in one dimension: Dependence on initial conditions

The propagation of an initially Gaussian wave packet of width [Formula: see text] in Gross–Pitaevskii equation is extensively studied both for attractive and repulsive interactions. It is predicted analytically and verified numerically that for a free particle with attractive interaction, the dynamics of the width is governed by an effective potential which is sensitive to initial conditions. If [Formula: see text] is equal to a corresponding critical width [Formula: see text], then the packet will propagate in time with very little change in shape. These are in essence like coherent states. Whereas, if [Formula: see text], depending on the nature of the effective potential for chosen [Formula: see text] and the interaction strength [Formula: see text], the width of the packet in course of time, either oscillates with bounded width or will spread like a free particle. For a simple harmonic oscillator (SHO) also, we find that for [Formula: see text] smaller than a critical value, there always exists a coupling strength for which the packet simply oscillates about the mean position without changing its shape, once again providing a resemblance to a coherent state. We also consider the Morse potential, which interpolates between the free particle and the oscillator. For large attractive interactions, the two limiting dynamics (free and simple harmonic) are indeed observed but in the intermediate form of the potential where the nonlinear terms dominate in the dynamics, an initial Gaussian wave packet does not retain its shape. For repulsive interaction, the Gaussian packet always changes shape no matter what the system parameters are.

Preparation and Characterization of Novel Self-Cleaning Glasses with TiO2 Coatings

Common glass for architecture had only one function, i.e., transparency and the requirement for indoor health made “environmental protection type” novel glass necessary. In the present study, a novel self-cleaning glass was prepared by sol-gel method. To form self-cleaning glass, common glass was adopted as the foundation base and TiO2 coatings were cover its outside surfaces. The novel glass had little change in shape but alteration to slightly white compared to common glass, thanks to white TiO2. The self-cleaning glass could reduce formaldehyde concentration of air from more than 160 mg•m3 to 0.4 mg•m3 within 60 h, while the common glass could cut down to ca. 30 mg•m3 and reaching equilibrium before 24 h. The removal of formaldehyde by common glass could be owing to adsorption action and slightly gradation by ultraviolet light, and the removal by self-cleaning glass could be mostly assigned to photodegradation by TiO2 when ultraviolet light irradiation. Besides, the self-cleaning glass exhibit 74.99% and 91.60% anti-bacteria rate to Escherichia coli and Staphylococcus aureus, respectively, when common glass was chosen as control. In brief, the self-cleaning glass was proved excellent to remove formaldehyde and inhibit bacteria. As a result of the non-preference of the photodegradtion and anti-bacteria by TiO2, it was believed the self-cleaning glass could remove almost all the kinds of indoor organic gases and inhibit almost all the kinds of bacteria, including some pathogens. The self-cleaning glass had great potential in interior finish application meeting the challenge for environmental protection.

The evolution of free wave packets

We discuss four general features of the force-free evolution of wave packets: (1) The spatial spread of a packet changes with time in a simple way. (2) For sufficiently short durations (related to the spread in the momentum of the packet) the probability distribution will move with uniform speed and little change in shape. (3) After a sufficiently long time (related to the initial spatial spread) the wave function converges to a simple form that is simply related to the momentum distribution of the packet. In this asymptotic regime the shape of the probability distribution no longer changes, and its scale increases linearly with the time. (4) There is an infinite denumerable set of simple wave packets (the Hermite-Gauss packets) that do not change shape at any time during their evolution.

Latitudinal Variation of the Solar Photospheric Intensity

We have examined images from the Precision Solar Photometric Telescope (PSPT) at the Mauna Loa Solar Observatory (MLSO) in search of latitudinal variation in the solar photospheric intensity. Along with the expected brightening of the solar activity belts, we have found a weak enhancement of the mean continuum intensity at polar latitudes (continuum intensity enhancement $\sim0.1 - 0.2%$ corresponding to a brightness temperature enhancement of $\sim2.5{\rm K}$). This appears to be thermal in origin and not due to a polar accumulation of weak magnetic elements, with both the continuum and CaIIK intensity distributions shifted towards higher values with little change in shape from their mid-latitude distributions. Since the enhancement is of low spatial frequency and of very small amplitude it is difficult to separate from systematic instrumental and processing errors. We provide a thorough discussion of these and conclude that the measurement captures real solar latitudinal intensity variations.

The shape of the triangular fibrocartilage during pronation–supination

We studied the changes in the shape of the triangular fibrocatilage (TFC: disc proper) which occur during forearm rotation in disarticulated and articulated wrists. The influence of artificial 3 mm ulnar lengthening on distortion of the disc was also examined. In the disarticulated wrists, slight distortion of the central and radial portions of the TFC was observed in the ulnar neutral variance specimens. More distortion was noted in the radial and central portions of the TFC in specimens with positive ulnar variance or with the ulna lengthened. However, in the articulated wrist, the TFC demonstrated little change in shape during pronosupination even in the ulnar positive variance wrists or with the ulna lengthened. There was no significant change in palmar and dorsal peripheral lengths of the TFC in ulnar neutral, ulnar positive or ulna-lengthened specimens at three rotatory positions of the forearm. These findings suggest that changes in ulnar variance which occur during forearm rotation can produce distortion on the TFC, but the carpus helps to maintain the shape of the TFC during pronation–supination, even with positive ulnar variance.

Auditory filter nonlinearity in mild/moderate hearing impairment.

Sensorineural hearing loss has frequently been shown to result in a loss of frequency selectivity. Less is known about its effects on the level dependence of selectivity that is so prominent a feature of normal hearing. The aim of the present study is to characterize such changes in nonlinearity as manifested in the auditory filter shapes of listeners with mild/moderate hearing impairment. Notched-noise masked thresholds at 2 kHz were measured over a range of stimulus levels in hearing-impaired listeners with losses of 20-50 dB. Growth-of-masking functions for different notch widths are more parallel for hearing-impaired than for normal-hearing listeners, indicating a more linear filter. Level-dependent filter shapes estimated from the data show relatively little change in shape across level. The loss of nonlinearity is also evident in the input/output functions derived from the fitted filter shapes. Reductions in nonlinearity are clearly evident even in a listener with only 20-dB hearing loss.

Reinforced Elastomer Roller for Toner Transfer

In commercial electrophotographic copiers and printers, roll fusing, media handling, and toner transfer are technologies that incorporate friction drive with elastomer-coated rollers. When two rollers form a pressure nip and at least one roller is deformable, the surface strain of the deformed roller defines the length of the nip contact area and the speed of the frictionally driven roller. To insure high levels of performance from sub-systems that utilize friction drive, it is important to maintain consistent surface speeds of rollers forming a nip, under a variety of external noises, such as manufacturer tolerances, lack of roller parallelism, media thickness, media tension, and variable toner stack heights. These noises cause variations in surface strains and subsequently surface speeds, adversely impacting image quality, for example, image-to-page registration, color registration, and fusing nip dwell times.For an application that utilizes friction drive for toner transfer, an intermediate image-holding roller has been designed to conform radially with little change in shape circumferentially. The presence of a reinforcing layer just below the surface of an elastomer-coated roller enables sufficient nip contact area for electrostatic toner transfer with minimized drive variations due to external noises. The geometry and material properties of the composite roller is optimized with finite element analysis (FEA). Data from overdrive measurements confirm a reduction in speed variation, and results from a toner transfer experiment show suitable performance for high quality color printing.

Doppler spectra of laboratory wind waves at low grazing angle

Eight radar frequencies over a range from 3 GHz to 94 GHz have been used to measure Doppler spectra of wind waves in a laboratory wind-wave tank, at low grazing angle. The VV spectra show relatively little change in shape at different frequencies. The HH spectra show significant trends in the lower radar frequencies, some of which are probably artefacts of the experiment. A new model, the ‘fish model’ is developed empirically from measurements of the peak Doppler spectra for both vertical and horizontal polarization. This model indicates that the H-pol, not just the V-pol, peak Doppler shift is dependent on the radar frequency.

Transplantation of RPE in Age-related Macular Degeneration

• A study was carried out to investigate whether human RPE allografts are tolerated or rejected in the subretinal space and to determine the feasibility of RPE transplantation in subjects with age-related macular degeneration (AMD). • Methods: Patches of human fetal RPE (13–20 weeks of gestational age) were transplanted into the subretinal space of five patients after surgical removal of subfoveal fibrovascular membranes, and to four subjects with dry geographic atrophy. Suspensions of RPE cells were transplanted to four other patients with nonexudative AMD. Results were evaluated with clinical ophthalmological examination, SLO microperimetry and fluorescein angiography over 8–20 months. • Results: In disciform lesions, RPE transplants developed macular edema and fluorescein leakage concomitant with gradual reduction of visual acuity, implying host-graft rejection, over 1–6 months. In geographic atrophy, three of four transplants showed little change in shape and size after 12 months (one transplant was slowly rejected). In non-exudative AMD, RPE suspension transplants showed no evidence of rejection and were associated with the disappearance of drusen; visual acuity remained stable and SLO microperimetry confirmed retinal function over the transplanted area. • Conclusion: Human RPE allografts are not invariably rejected in the subretinal space without immunosuppression. The rejection rate is lower in nonexudative than in neovascular AMD. An intact blood-retinal barrier is likely to protect against rejection. It is technically feasible to transplant human RPE into the submacular space without adversely affecting visual function in nonexudative AMD over relatively long periods of time

擬二元系化合物Ｓｍ１−ｘＲｘＡｌ２の熱磁気特性

The thermomagnetic behavior of ferromagnetic pseudo-binary compounds Sm1-xRxAl2 (R = Sc, Y, La, Nd, Gd) was studied. For R = Sc, Y, La, the ordering temperature gently decreased in proportion to x, and little change in shape was observed in their thermomagnetic curves. The magnetic substituents Nd and Gd, on the other hand, had a considerable influence on the thermomagnetic properties. Due to the negative contribution of the spin moments to the magnetization in SmAl2 and ferromagnetic coupling between the spins of Sm and the substituent, Nd increased the resultant magnetization and a small amount of Gd decreased it. In the latter case, compensation between the partial magnetization arising from the spin moments and that arising from the orbital ones was observed at 81 K and 64 K for x = 1.8% and 2.6%, respectively.

Transplantation of RPE in age-related macular degeneration: Observations in disciform lesions and dry RPE atrophy

A study was carried out to investigate whether human RPE allografts are tolerated or rejected in the subretinal space and to determine the feasibility of RPE transplantation in subjects with age-related macular degeneration (AMD). Patches of human fetal RPE (13-20 weeks of gestational age) were transplanted into the subretinal space of five patients after surgical removal of subfoveal fibrovascular membranes, and to four subjects with dry geographic atrophy. Suspensions of RPE cells were transplanted to four other patients with nonexudative AMD. Results were evaluated with clinical ophthalmological examination, SLO microperimetry and fluorescein angiography over 8-20 months. In disciform lesions, RPE transplants developed macular edema and fluorescein leakage concomitant with gradual reduction of visual acuity, implying host-graft rejection, over 1-6 months. In geographic atrophy, three of four transplants showed little change in shape and size after 12 months (one transplant was slowly rejected). In non-exudative AMD, RPE suspension transplants showed no evidence of rejection and were associated with the disappearance of drusen; visual acuity remained stable and SLO microperimetry confirmed retinal function over the transplanted area. Human RPE allografts are not invariably rejected in the subretinal space without immunosuppression. The rejection rate is lower in nonexudative than in neovascular AMD. An intact blood-retinal barrier is likely to protect against rejection. It is technically feasible to transplant human RPE into the submacular space without adversely affecting visual function in nonexudative AMD over relatively long periods of time.

Fluorescence anisotropy decay of ethidium bound to nucleosome core particles. 1. Rotational diffusion indicates an extended structure at low ionic strength

The fluorescence decay of ethidium intercalated into the DNA of nucleosome core particles increases in average lifetime from about 22 ns in H2O to about 39 ns in D2O. This increase, combined with the acquisition of large amounts of data (on the order of 10(8) counts per decay), allows measurement of anisotropy decays out to more than 350 ns. The overall slow rotational motions of the core particle may thereby be more clearly distinguished from the faster torsional motions of the DNA. In 10 mM NaCl at 20 degrees C, we recover a long correlation time of 198 ns in D2O (159 ns when corrected to a viscosity of 1.002 cP), in agreement with the value of 164 ns obtained in H2O. These values are consistent with hydrodynamic calculations based on the expected size and shape of the hydrated particle. To support our conclusion that this long correlation time derives from Brownian rotational diffusion, we show that the value is directly proportional to the viscosity and inversely proportional to the temperature. No significant changes in the rotational correlation time are observed between 1 and 500 mM ionic strength. Below 1 mM, the particle undergoes the "low-salt transition" as measured by steady-state tyrosine fluorescence anisotropy. However, we observe little change in shape until the ionic strength is decreased below approximately 0.2 mM, where the correlation time increases nearly 2-fold, indicating that the particle has opened up into an extended form. We have previously shown that the transition becomes nonreversible below 0.2 mM salt.

Bulk diffusion of metal particles on ceramic substrates

THE dynamical behaviour of metal particles or films deposited on ceramic surfaces is of great importance in heterogeneous catalysis, metal brazing of ceramics and microelectronics. The existing understanding of, for example, metal particle sintering or dispersion has tended to be based on static, room-temperature ex situ studies, which have considered only surface spreading of the metal1–3. Here we present evidence from in situ electron microscopy for the diffusion of metal particles through the bulk of a ceramic substrate. We have studied the dynamics of small copper particles on the surface of amorphous alumina in various oxidizing and reducing atmospheres (hydrogen, oxygen and carbon monoxide). Under oxygen, particles first diffuse through the substrate with little change in shape, but at later times particles spread laterally (by surface or sub-surface diffusion) to a configuration of lower surface energy. We suggest that these diffusion processes may be important in electronics applications, which involve similar combinations of materials.

The effects of gas adsorption on particle shapes in supported platinum catalysts

Previous work has shown that the shapes of the metal particles in a supported platinum catalyst are substantially altered when the catalyst is treated in an appropriate adgas. However, at present it is unclear why the shape changes occur. In the work here, simple first-order calculations were done to examine the effects of hydrogen, nitrogen, and carbon monoxide on the equilibrium crystal shape of the platinum particles in a supported platinum catalyst. The calculations assumed that the main effect of the gaseous environment was to change the surface free energy of the facets on the platinum particles. The results of the calculations showed that when a clean platinum particle is equilibrated in nitrogen, the shape should not change significantly. However, Pt(l00) facets should grow in hydrogen while Pt(210) facets should grow in carbon monoxide. By comparison, previous experiments have shown that Pt(l00) facets do grow in hydrogen. Little change in shape is observed in nitrogen. Thus, it seems that changes in the surface free energy of the facets in the metal particles on a supported metal catalyst due to the presence of an adgas play an important role in the shape changes which are observed.

Sodium and gating current time shifts resulting from changes in initial conditions.

The sodium and gating currents of the squid giant axon elicited by a depolarizing pulse are delayed, with little change in shape, as a result of a hyperpolarizing prepulse. The delays are almost completely saturated, at approximately 45 microseconds, for prepulses to -140 mV. At 8 degrees C they develop with time constants of between 60 and 180 microseconds for prepulses in the -130- to -150-mV range. There is a correlation between the extra charge moved during the gating current and the increase in the time delay of the sodium current as the magnitude of the hyperpolarizing prepulse is increased. These results strengthen the conclusion that the gating current is indeed closely associated with the process of sodium channel opening and provide information concerning the kinetics of the early steps, which are hidden in ionic current measurements. The main features of the gating and sodium current time shifts and the correlation between charge movement and time shifts are duplicated by a sequential six-state model for sodium activation.

Cross-sectional shape of the child's trachea by computed tomography.

Computed tomographic scanning was used to investigate the shape in cross section of the lumen of the pediatric trachea. Seven children up to age 10 (mostly age 6 or older), six girls aged 10-19, and six boys aged 10-19 had scans of their tracheas, mostly during breath-holding not far from total lung capacity. At these ages and under these circumstances, the trachea may be slightly narrow just below the larynx, and it broadens just above its bifurcation. At other levels, it is only mildly or moderately off-circular although there are variations from patient to patient and from level to level. The severely off-circular shapes found by others during autopsies and computed tomography of the middle-aged and elderly were not detected in these children and adolescents. Under the circumstances of the study, there was little change in shape or size as the trachea passed from the neck into the chest, nor was there a consistent difference in tracheal shape between girls and boys.

Invariance of ankle dynamic stiffness during fatiguing muscle contractions

Our objective was to determine the effect of muscle fatigue on the dynamic stiffness of the human ankle. Four subjects were required to maintain constant-force contractions of tibialis anterior until the required force could no longer be maintained. Repeated pseudo-random displacements of ankle angular position were applied throughout each contraction. The dynamic relation between ankle angular position and ankle torque was identified by determining non-parametric compliance impulse response functions (CIRFs). The CIRFs were redetermined every 2.55s throughout the sustained contractions to provide a quantitative measure of changes in ankle stiffness dynamics. Inspection of these CIRFs revealed little change in shape or magnitude throughout the contractions, despite large increases in tibialis anterior EMG. The dynamics were further quantified by estimating the equivalent joint inertia, viscosity and elasticity associated with each CIRF. As each contraction progressed, the inertial and elastic terms remained constant whereas the viscous term decreased slightly. These findings demonstrate that fatigue of tibialis anterior during sustained constant mean force contractions results in little change in the mechanical dynamics of the human ankle.

Local buckling of universal beam flanges

To study fatigue of defective welds, beam-column joints were cyclically loaded at MWD Central Laboratories. However, local buckling occurred in the beam flanges during the first few cycles at displacement ductilities 2.25-2.6. Despite the buckling, the peak resisted load had a maximum of 15% reduction after 10 cycles at these ductilities, and the hysteresis loops showed little change in shape. Nevertheless, because steel frame structures can be expected to sustain a ductility demand of about 4/SM or 6, there is clearly some doubt as to whether the strength of a system already buckling at a DF < 3 would be maintained under the design earthquake. The 310 UB 40 beam tested complied with the current NZ Steel Code, which required no stiffeners in this case.