Comparison of averages of flows and maps

It is shown that in transient chaos there is no direct relation between averages in a continuos time dynamical system (flow) and averages using the analogous discrete system defined by the corresponding Poincare map. In contrast to permanent chaos, results obtained from the Poincare map can even be qualitatively incorrect. The reason is that the return time between intersections on the Poincare surface becomes relevant. However, after introducing a true-time Poincare map, quantities known from the usual Poincare map, such as conditionally invariant measure and natural measure, can be generalized to this case. Escape rates and averages, e.g. Liapunov exponents and drifts can be determined correctly using these novel measures. Significant differences become evident when we compare with results obtained from the usual Poincare map.Comment: 4 pages in Revtex with 2 included postscript figures, submitted to Phys. Rev.

Immune Reconstitution in HIV-Infected Patients

The prognosis of patients infected with human immunodeficiency virus (HIV) type 1 has dramatically improved since the advent of potent antiretroviral therapies (ARTs), which have enabled sustained suppression of HIV replication and recovery of CD4 T cell counts. Knowledge of the function of CD4 T cells in immune reconstitution was derived from large clinical studies demonstrating that primary and secondary prophylaxis against infectious agents, such as Pneumocystis jirovecii (Pneumocystis carinii), Mycobacterium avium complex, cytomegalovirus, and other pathogens, can be discontinued safely once CD4 T cell counts have increased beyond pathogen-specific threshold levels (usually >200 CD4 T cells/mm3) for 3-6 months. The downside of immune reconstitution is an inflammatory syndrome occurring days to months after the start of ART, with outcomes ranging from minimal morbidity to fatal progression. This syndrome can be elicited by infectious and noninfectious antigens. Microbiologically, the possible pathogenic pathways involve recognition of antigens associated with ongoing infection or recognition of persisting antigens associated with past (nonreplicating) infection. Specific antimicrobial therapy, nonsteroidal anti-inflammatory drugs, and/or steroids for managing immune reconstitution syndrome should be considere

Prospectus, November 15, 1989

https://spark.parkland.edu/prospectus_1989/1028/thumbnail.jp

Osteoporosis case finding in the general practice: phalangeal radiographic absorptiometry with and without risk factors for osteoporosis to select postmenopausal women eligible for lumbar spine and hip densitometry

Mass screening for osteoporosis using DXA measurements at the spine and hip is presently not recommended by health authorities. Instead, risk factor questionnaires and peripheral bone measurements may facilitate the selection of women eligible for axial bone densitometry. The aim of this study was to validate a case finding strategy for postmenopausal women who would benefit most from subsequent DXA measurement by using phalangeal radiographic absorptiometry (RA) alone or in combination with risk factors in a general practice setting. The sensitivity and specificity of this strategy in detecting osteoporosis (T-score ≤2.5SD at the spine and/or the hip) were compared with those of the current reimbursement criteria for DXA measurements in Switzerland. Four hundred and twenty-three postmenopausal women with one or more risk factors for osteoporosis were recruited by 90 primary care physicians who also performed the phalangeal RA measurements. All women underwent subsequent DXA measurement of the spine and the hip at the Osteoporosis Policlinic of the University Hospital of Berne. They were allocated to one of two groups depending on whether they matched with the Swiss reimbursement conditions for DXA measurement or not. Logistic regression models were used to predict the likelihood of osteoporosis versus "no osteoporosis” and to derive ROC curves for the various strategies. Differences in the areas under the ROC curves (AUC) were tested for significance. In women lacking reimbursement criteria, RA achieved a significantly larger AUC (0.81; 95% CI 0.72-0.89) than the risk factors associated with patients' age, height and weight (0.71; 95% C.I. 0.62-0.80). Furthermore, in this study, RA provided a better sensitivity and specificity in identifying women with underlying osteoporosis than the currently accepted criteria for reimbursement of DXA measurement. In the Swiss environment, RA is a valid case finding tool for patients with risk factors for osteoporosis, especially for those who do not qualify for DXA reimbursemen

CD4+ T Cell Count Recovery in HIV Type 1-Infected Patients Is Independent of Class of Antiretroviral Therapy

Background. In recent years, treatment options for human immunodeficiency virus type 1 (HIV-1) infection have changed from nonboosted protease inhibitors (PIs) to nonnucleoside reverse-transcriptase inhibitors (NNRTIs) and boosted PI-based antiretroviral drug regimens, but the impact on immunological recovery remains uncertain. Methods. During January 1996 through May 2007, all patients in the Swiss HIV Cohort were included if they received the first combination antiretroviral therapy (cART) and had known baseline CD4+ T cell counts and HIV-1 RNA values (n=3293). The mean (±SD) duration of follow-up was 26.8±20.5 months. The follow-up time was limited to the duration of the first cART. CD4+ T cell recovery was analyzed in 3 different treatment groups: nonboosted PI, NNRTI, or boosted PI. The end point was the absolute increase of CD4+ T cell count in the 3 treatment groups after the initiation of cART. Results. Two thousand five hundred ninety individuals (78.7%) initiated a nonboosted-PI regimen, 452 (13.7%) initiated an NNRTI regimen, and 251 (7.6%) initiated a boosted-PI regimen. Absolute CD4+ T cell count increases at 48 months were as follows: in the nonboosted-PI group, from 210 to 520 cells/µL; in the NNRTI group, from 220 to 475 cells/µL; and in the boosted-PI group, from 168 to 511 cells/µL. In a multivariate analysis, the treatment group did not affect the response of CD4+ T cells; however, increased age, pretreatment with nucleoside reverse-transcriptase inhibitors, serological tests positive for hepatitis C virus, Centers for Disease Control and Prevention stage C infection, lower baseline CD4+ T cell count, and lower baseline HIV-1 RNA level were risk factors for smaller increases in CD4+ T cell count. Conclusion. CD4+ T cell recovery was similar in patients receiving nonboosted PI-, NNRTI-, and boosted PI-based cAR

Characteristics, Determinants, and Clinical Relevance of CD4 T Cell Recovery to <500 Cells/µL in HIV Type 1—Infected Individuals Receiving Potent Antiretroviral Therapy

Background. The CD4 T cell count recovery in human immunodeficiency virus type 1 (HIV-1)—infected individuals receiving potent antiretroviral therapy (ART) shows high variability. We studied the determinants and the clinical relevance of incomplete CD4 T cell restoration. Methods. Longitudinal CD4 T cell count was analyzed in 293 participants of the Swiss HIV Cohort Study who had had a plasma HIV-1 RNA load .05). Older age (adjusted odds ratio [aOR], 1.71 per 10-year increase; 95% confidence interval [CI], 1.21-2.43), lower baseline CD4 T cell count (aOR, 0.37 per 100-cell increase; 95% CI, 0.28-0.49), and longer duration of HIV infection (aOR, 2.39 per 10-year increase; 95% CI, 1.19-4.81) were significantly associated with a CD4 T cell count <500 cells/µL at 5 years. The median increases in CD4 T cell count after 3-6 months of ART were smaller in incomplete responders (P < .001) and predicted, in conjunction with baseline CD4 T cell count and age, incomplete response with 80% sensitivity and 72% specificity. Conclusion. Individuals with incomplete CD4 T cell recovery to <500 cells/µL had more advanced HIV-1 infection at baseline. CD4 T cell changes during the first 3-6 months of ART already reflect the capacity of the immune system to replenish depleted CD4 T lymphocyte

Cmos Programmable Time Control Circuit Design For Phased Array Uwb Ground Penetrating Radar Antenna Beamforming

Phased array radar systems employ multiple antennas to create a radar beam that can be steered electronically. By manipulating the relative phase values of feeding signals among different antennas, the effective radiation pattern of the array can be synthesized to enhance the main lobe in a desired direction while suppressing the undesired side lobes in other directions. Hence the radar scanning angles can be electronically controlled without employing the bulky mechanical gimbal structure, which can significantly reduce radar system size, weight and power consumption. In recent years, phased array technologies have received great attentions and are explored in developing many new applications, such as smart communication systems, military radars, vehicular radar, etc. Most of these systems are narrow band systems, where the phase delays are realized with narrow band phase shifter circuits. For the impulse ground penetrating radar however, its operating frequency spans an ultrawide bandwidth. Therefore the traditional phase shifters are not applicable due to their narrow band nature. To resolve the issue, in this study, a true time delay approach is explored which can precisely control time delays for the feeding pulse signals among different antennas in the array. In the design, an on chip programmable delay generator is being developed using Global Foundry 0.18 µm 7 HV high voltage CMOS process. The time delay control is realized by designing a programmable phase locked loop (PLL) circuit which can generate true time delays ranging from 100 ps (picoseconds) to 500 ps with the step size of 25 ps. The PLL oscillator\u27s frequency is programmable from 100MHz to 500MHz through two reconfigurable frequency dividers in the feedback loop. As a result, the antenna beam angle can be synthesized to change from 9.59° to 56.4° with a step of 2.75°, and the 3dB beamwidth is 10°. The power consumption of the time delay circuit is very low, where the supply voltage is 1.8V and the average current is as low as 472uA

Relationship between casting modulus and grain size in cast A356 aluminium alloys

Microstructure of Al-Si alloy castings depends most generally on melt preparation and on the cooling rate imposed by the thermal modulus of the component. In the case of Al-Si alloys, emphasis is put during melt preparation on refinement of pro-eutectic (Al) grains and on modification of the Al-Si eutectic. Thermal analysis has been used since long to check melt preparation before casting, i.e. by analysis of the cooling curve during solidification of a sample cast in an instrumented cup. The conclusions drawn from such analysis are however valid for the particular cooling conditions of the cups. It thus appeared of interest to investigate how these conclusions could extrapolate to predict microstructure in complicated cast parts showing local changes in the solidification conditions. For that purpose, thermal analysis cups and instrumented sand and die castings with different thermal moduli and thus cooling rates have been made, and the whole set of cooling curves thus recorded has been analysed. A statistical analysis of the characteristic features of the cooling curves related to grain refinement in sand and die castings allowed determining the most significant parameters and expressing the cube of grain size as a polynomial of these parameters. After introduction of a further parameter quantifying melt refining an excellent correlation, with a R2 factor of 0.99 was obtained