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Results for “phase variation”

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PubMed2005

Preventing renal failure in patients with severe lupus nephritis.

BACKGROUND AND METHODS: Advances in immunosuppressive treatment regimens, with increased efficacy, while minimizing the treatment-related toxicities, and better prevention and treatment of complications, have resulted in improved patient and renal survival in subjects with severe proliferative lupus nephritis over the past few decades. This review discusses the issues that are pertinent to the preservation of renal function in these patients. RESULTS AND CONCLUSION: Treatment of severe proliferative lupus nephritis can be divided into an initial phase of induction followed by a prolonged maintenance phase, both of which impact upon the long-term renal and patient survival. The immunosuppressive potency of the treatment required for disease control varies according to the disease activity during the different phases. Despite variations in the choice, duration, and route of administration of antiproliferative agents, data to date suggest that immunosuppressive treatments combining cyclophosphamide or mycophenolate mofetil with corticosteroid appear to have similar efficacy in terms of inducing immunologic remission. In this regard, the immunologic efficacy of treatment is prerequisite to the prevention of irreversible loss of nephrons, but long-term renal outcome is also dependent on factors other than treatment efficacy, such as preexisting renal parenchymal damage and blood pressure control. Prompt diagnosis, early effective therapy, and reducing the risk of relapses are the disease specific measures that are essential to long-term renal preservation and the prevention of renal failure in subjects with severe proliferative lupus nephritis.

Humans↗

PubMed1996

Sequential measurements of human decidua-associated protein (hDP) 200 in the uterine fluid during the menstrual cycle.

PROBLEM: To examine the relationship between the concentration of uterine fluid human decidua-associated protein (hDP) 200, identified as a monoclonal rheumatoid factor, and different phases of the menstrual cycle. METHODS: Sequential measurements of hDP 200 concentration in uterine fluid were performed in 11 normal ovulatory women, aged 22-36 years. The samples were collected in early proliferative phase, late proliferative phase, periovulatory period, early secretory phase, and late secretory phase. RESULTS: Consistent fluctuations of hDP 200 levels in uterine fluid were found throughout the menstrual cycle. High levels were found during early proliferative phase and periovulatory period related to significantly lower levels during late proliferative and early luteal phases. CONCLUSION: There is menstrual phase dependent variation in the uterine fluid levels of hDP 200.

Adult↗

PubMed1996

Regulation of ram scrotal temperature during heat exposure, cold exposure, fever and exercise.

1. We measured body core and scrotal temperatures (Tbody and Tscrotum, respectively) of rams during 5 h of hot (40 degrees C) and cold (6 degrees C) exposure, for 6 h following intravenous injections of saline (0.9% NaCl) or 0.4 micrograms kg-1 of the purified lipopolysaccharide endotoxin of Salmonella typhosa (LPS), during 40 min of treadmill exercise, and for several days in their pens. 2. At 20-23 degrees C ambient temperature there were significant, but out of phase, circadian variations in Tbody and Tscrotum. Tscrotum was 3.30 +/- 0.03 degrees C lower than Tbody on average. 3. During cold exposure the tunica dartos muscles contracted, nevertheless Tscrotum fell and Tbody-Tscrotum increased. During heat exposure the tunica dartos muscle relaxed and scrotal sweat glands were activated, nevertheless Tscrotum rose and Tbody-Tscrotum decreased. There was no change in Tscrotum after LPS injection or during exercise, but Tbody increased in both cases. 4. We suggested that Tscrotum is regulated independently of Tbody via a feedback circuit involving scrotal thermoreceptors and effectors in the form of tunica dartos muscle activity and scrotal sweat gland activity. This local circuit is not affected by adjustments to the general thermo-regulatory control system during fever. The effector mechanisms were insufficient to maintain Tscrotum during the extremes of heat and cold exposure.

Animals↗

PubMedDate not supplied

Quantification of the wound healing using polarization-sensitive optical coherence tomography.

We use polarization-sensitive optical coherence tomography (PS-OCT) to monitor the wound healing process in vitro and in vivo, which are affected by various drugs. Five rabbit subjects are used for in vitro studies and another five are used for in vivo studies. The in vitro studies are conducted to compare the PS-OCT images with histopathology. For each subject, three biopsy lesions are created on each ear: one site is not treated (control); the second site is treated with sphingosylphosphorylcholine, which is expected to promote healing; and the last is administered with tetraacetylphytosphingosine, which negatively affects the healing process. Each site is examined with a PS-OCT system at 1, 4, 7, 10, and 14- days after wound generation. The variations of phase retardation values caused by the collagen morphology changes on wound sites are quantified for all cases. Our results suggest that PS-OCT may be a useful tool for visualization of collagen fiber regeneration and for quantification of various drug effects during the wound healing process.

Animals↗

PubMed2004

Correlation of ultrasonic scatterer size estimates for the statistical analysis and optimization of angular compounding.

Ultrasonic scatterer size estimates generally have large variances due to the inherent noise of spectral estimates used to calculate size. Compounding partially correlated size estimates associated with the same tissue, but produced with data acquired from different angles of incidence, is an effective way to reduce the variance without making dramatic sacrifices in spatial resolution. This work derives theoretical approximations for the correlation between these size estimates, and the coherence between their associated spectral estimates, as functions of ultrasonic system parameters. A Gaussian spatial autocorrelation function is assumed to adequately model scatterer shape. Both approximations compare favorably with simulation results, which consider validation near the focus. Utilization of the correlation/coherence expressions for statistical analysis and optimization is discussed. Approximations, such as the invariance of phase and amplitude terms with angle, are made to obtain closed-form solutions to the derived spectral coherence near the focus and permit analytical optimization analysis. Results indicate that recommended parameter adjustments for performance improvement generally depend upon whether, for the system under consideration, the primary source of change in total coherence with rotation is phase term variation due to the change in the relative position of scattering sites, or field amplitude term variation due to beam movement.

Analysis of Variance↗

PubMed2004

Polymorphism in presolar Al2O3 grains from asymptotic giant branch stars.

We report microstructural and isotopic analyses of two presolar Al2O3 grains. Aluminum oxide is important cosmically, because its presence has been detected in the infrared spectra of the circumstellar envelopes of O-rich asymptotic giant branch stars and because it is predicted to be the first solid to condense in these stellar environments. The two grain structures, one corundum and the other amorphous, confirm that asymptotic giant branch stars produce both phases. The variation in structure and Ti content demonstrates that Al2O3 can condense in the absence of TiO2 seed clusters but that Ti may be important in determining the crystal structure.

Aluminum Oxide↗

PubMed1999

Controlling the morphology of amorphous solid water

The morphology of amorphous solid water grown by vapor deposition was found to depend strongly on the angular distribution of the water molecules incident from the gas phase. Systematic variation of the incident angle during deposition using a collimated beam of water led to the growth of nonporous to highly porous amorphous solid water. The physical and chemical properties of amorphous solid water are of interest because of its presence in astrophysical environments. The ability to control its properties in the laboratory may shed light on some of the outstanding conflicts related to this important material.

Journal Article↗

PubMed2002

Differential expression of virulence-related genes in Enterococcus faecalis in response to biological cues in serum and urine.

Enterococci rank among leading causes of nosocomial bacteremia and urinary tract infection and are also a leading cause of community acquired subacute endocarditis. Limited evidence suggests that biological cues in serum and urine may play an important role in modulating enterococcal virulence at sites of infection. To determine the extent to which biological cues affect enterococcal virulence-associated gene expression, we used quantitative real-time PCR to compare mRNA levels in Enterococcus faecalis cultures grown in serum or urine to that achieved in laboratory medium. Both environment- and growth phase-specific variations were observed, demonstrating the occurrence of as-yet-uncharacterized mechanisms for control of gene expression in E. faecalis that may play an important role in vivo.

Enterococcus faecalis↗

PubMed1985

Effects of cisapride, a new gastrointestinal prokinetic substance, on interdigestive and postprandial motor activity of the distal oesophagus in man.

Cisapride is a newly developed substance that stimulates gastrointestinal motility, possibly enhancing acetylcholine release in the gut wall. The aim of our study was to investigate the effect of cisapride on oesophageal motor function in man. In a blind fashion and in random order six healthy volunteers received cisapride (0.5 mg/h intravenously, preceded by a three day oral loading at 10 mg tid) and matching placebo. Oesophageal contractions and lower oesophageal sphincter pressure were constantly recorded during a complete cycle of the interdigestive migrating motor complex and during two and half hours after a mixed test meal. Cisapride did not disturb the interdigestive migrating motor complex. In the fasting state the lower oesophageal sphincter pressure showed considerable interdigestive migrating motor complex phase-related variations, whereas amplitude and duration of the oesophageal contractions did not. In the dosis used cisapride was found to increase lower oesophageal sphincter pressure in the interdigestive and in the late postprandial state, but to have no effect in the early postprandial period. Amplitude and duration of oesophageal contractions were not affected by cisapride.

Adult↗

PubMed1996

Serum lipoperoxide level variations in normal and luteal phase defect cycles.

A luteal phase defect (LPD) is a clinical problem leading to infertility and is characterized by reduced progesterone levels during the luteal phase. Serum lipoperoxidation is an expression of cellular hypoxic damage occurring under all stress-oxidative conditions. Forty-eight consecutive infertility patients, according to the infertility class II of the WHO classification, underwent clinical observation. Twenty-five patients ovulated constantly with a normal luteal phase, while the other 23 had a LPD, hormonally and histologically assessed. The luteal phase was monitored biochemically by titration of progesterone, oestradiol, and serum lipid peroxides during the ovulatory period and 6-12 days after ovulation. The mean plasmatic concentration of oestradiol was not statistically different between the LPD and the normal-cycle groups, while a statistically significant difference was found for progesterone plasmatic concentrations between the LPD and the normal-cycle groups (p < 0.05); a greater statistical difference was also found in the mean serum lipoperoxide titration (p < 0.001). These findings suggest that serum lipoperoxidation titration may be a useful tool in the study of the interactions between hormonal milieu and sympathetic activity.

Estradiol↗

PubMedDate not supplied

Assessing the health of adult daughter former caregivers for elders with Alzheimer's disease.

Past research is varied in assessing the effect of caregiving on health, particularly caregivers in the postcaregiving phase. The variation may be due, in part, to methodological issues, including the use of health measures not psychometrically tested. The study examines the Medical Outcomes Study Short Form 36 (SF-36) health survey with 102 former caregivers whose family member was deceased for at least one year at the time of the study and had been identified as having Alzheimer's disease or a related disorder. The SF-36 measures eight dimensions of physical and mental health and has been tested on a variety of populations, though not with former daughter caregivers. Confirmatory Factor Analysis supported the factorial validity of the SF-36 for this population, indicating it is a promising tool for understanding postcaregiver health.

Alzheimer Disease↗

PubMed1999

Running, breathing and visceral motion in the domestic rabbit (Oryctolagus cuniculus): testing visceral displacement hypotheses.

The relative motion of the visceral mass may be important to ventilation during running. A visceral piston hypothesis predicts that, during galloping, cranial motion of the liver during expiration and caudal motion of the liver during inspiration may characterize efficient quadrupedal mammalian locomotion. Although a theoretical model based on vibration mechanics casts doubt on this prediction, only limited direct measurements of visceral mass motion during galloping have been reported. In the present study, mechanical interactions between running, breathing and liver oscillations in the domestic rabbit are recorded using synchronized videographic, cineradiographic and pneumotachographic techniques. The analysis focuses on the variation in locomotor-respiratory coupling (LRC) and on the relative position of the liver. Results from running rabbits show (1) variation in phase angle between the locomotor and respiratory periods that is inconsistent with the 1:1 LRC ratio that has been reported for other galloping mammals; (2) a tendency towards a 1:1 LRC ratio at higher speeds and stride frequencies; and (3) that the relative motion of the liver is caudal during expiration and cranial during inspiration, which is inconsistent with the visceral piston hypothesis. The data presented here are generally consistent with the theoretical vibration mechanics model for liver motion and with a pneumatic stabilization hypothesis that the lungs serve an important role in the stabilization of the thorax during locomotion.

Animals↗

PubMed1990

Analysis of the diagnostic process in sialography.

The diagnostic process in sialography was evaluated using the mouse parotid gland as a model. The relative significance of each of the three diagnostic phases, psychophysical, psychological and nosological, was determined by analysing observer accuracy in detecting sialoadenitis and sialodochitis on digital and analogue microsialograms. Automated diagnosis based on parametric values of the digitized image was compared with the human system using ROC analysis. The overall accuracy of automated diagnosis was superior to that of an observer with analogue images. It is concluded that if observers were to be given the same quantitative information and informed of its diagnostic value in the psychological phase, then variation in the detection of the abnormalities could be reduced and the overall diagnostic accuracy in sialography improved.

Animals↗

PubMed2004

Instrument for measuring small angles by use of multiple total internal reflections in heterodyne interferometry.

A new instrument for measuring small angles by use of multiple total internal reflections in heterodyne interferometry is presented. With this instrument we can achieve a small rotation angle only by measuring the variation in phase difference between s- and p-polarization states. To improve its sensitivity we increase the number of total internal reflections by using two parallelogram prisms instead of two right-angle prisms. The angular resolution of the new instrument is better than 2.2 x 10(-6) rad over the measurement range -2.12 degrees < or = theta < or = 2.12 degrees for 20 total-internal reflections. The experimental results and the theoretical curve are in good agreement.

Journal Article↗

PubMed2006

Achromatic half-wave plate for submillimeter instruments in cosmic microwave background astronomy: modeling and simulation.

We adopted an existing formalism and modified it to simulate, with high precision, the transmission, reflection, and absorption of multiple-plate birefringent devices as a function of frequency. To validate the model, we use it to compare the measured properties of an achromatic five-plate device with a broadband antireflection coating to expectations derived from the material optical constants and its geometric configuration. The half-wave plate presented here is observed to perform well with a phase shift variation of < 2 degrees from the ideal 180 degrees over a bandwidth of Deltav/v approximately 1 at millimeter wavelengths. This formalism represents a powerful design tool for birefringent polarization modulators and enables its optical properties to be specified with high accuracy.

Journal Article↗

PubMed2003

Delay and dispersion characteristics of a frequency-domain optical delay line for scanning interferometry.

The reflective frequency-domain optical delay line employing a diffraction grating, a lens, and a tiltable mirror has emerged as a device particularly suitable for interferometry and optical coherence tomography. The device is comprehensively described, both theoretically and experimentally, in the context of interferometry. The variations of phase and group delay produced by the device as well as its dispersive properties are described and demonstrated experimentally.

Interferometry↗

PubMed2005

D-type fiber biosensor based on surface-plasmon resonance technology and heterodyne interferometry.

A D-type fiber biosensor based on surface-plasmon resonance (SPR) technology and heterodyne interferometry is presented. The sensing device is a single-mode optical fiber in which half the core is polished away and a thin-film layer of gold is deposited. We measure the phase-difference variations instead of the light intensity as in traditional SPR techniques. Therefore the accuracy and resolution of our method are very high. Its sensitivity can reach 2 x 10(-6) refractive-index units. The sensor has some merits, e.g., tunable high sensitivity, small size, lower cost, smaller sample volume, and suitability for in vivo testing. This novel method of a D-type fiber biosensor based on SPR technology and heterodyne interferometry is valuable for chemical, biological, and biochemical sensing, and the novel method of D-type fiber biosensing is a feasible means of study.

Alcohols↗

PubMed2005

A model for the Neurospora circadian clock.

Circadian clocks are important biological oscillators that generally involve two feedback loops. Here, we propose a new model for the Neurospora crassa circadian clock. First, we model its main negative feedback loop, including only experimentally well-documented reactions, the transcriptional activation of frequency (frq) by the white-collar complex (WCC), and the post-transcriptional dimerization of FRQ with WCC. This main loop is sufficient for oscillations and a similar one lies at the core of almost all known circadian clocks. Second, the model is refined to include the less characterized enhancement of white-collar 1 (WC-1) protein synthesis by FRQ, the positive second feedback loop. Numerical testing of different hypotheses led us to propose that the synthesis of WC-1 is enhanced by FRQ monomers and repressed by FRQ dimers. We demonstrate that this second loop contributes significantly to the robustness of the oscillator period against parameter variation. A phase response curve to light pulses is also computed and agrees well with experiments. On a general level, our results show that explicit time delays are not required for sustained oscillations but that it is crucial to take into account mRNA dynamics and protein-protein interactions.

Biological Clocks↗