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PubMed1997

A revised assessment of the HIV/AIDS incubation period, assuming a very short early period of high infectivity and using only San Francisco public health data on prevalence and incidence.

A revised assessment of the HIV/AIDS incubation period has been made, based on an updated operational model that includes a very short early period of high infectivity, following recent work by Jacquez et al. and using AIDS incidence data from the San Francisco Department of Public Health, plus data on AIDS incidence and HIV prevalence in a specially recruited cohort from the San Francisco City Clinic. The incubation period has, approximately, a suitably scaled gamma distribution with 14 degrees of freedom and mean 12.8 (SE 0.2) years. This information is essential in interpreting data from other areas and regions where AIDS incidence figures only are available, and is in particular intended for applications to several countries in Europe.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Periodic solutions of population models in a periodically fluctuating environment.

A periodically fluctuating environment is assumed in a population-modeling process that generates nonautonomous difference equations. The existence and uniqueness of periodic solutions are studied. A sufficient condition for existence and a necessary condition for uniqueness are obtained. Stability of the periodic solutions is investigated. Several numerical examples are given to illustrate the basic results, and a brief discussion is presented.

Environment↗
PubMed2005

Wenckebach's periods or alternating Wenckebach's periods during 4:1 atrioventricular block?

This article deals with the tracings of a patient having episodes of atrial flutter with 4:1 atrioventricular (AV) block increasing to 8:1 AV block. This phenomenon was attributed to the coexistence of 3-level block due to transverse dissociation with 2:1 AV block in the most proximal level, or first level as well as in the second level coexisting with a Wenckebach's period in the most distal, or third level. It is suggested that perhaps the term Wenckebach's periods during progression of 4:1 AV block best describes this arrhythmia so as to maintain the term alternating Wenckebach's periods only to those occurring when 2:1 block increases to higher degrees of AV block.

Aged↗
PubMed1997

Light Cycles Given During Development Affect Freerunning Period of Circadian Locomotor Rhythm of period Mutants in Drosophila melanogaster.

We reared wild type (Canton-S) and period mutant flies, i.e., per(S) and per(L), of Drosophila melanogaster in constant darkness, constant light or 24h light dark cycles with various light to dark ratios throughout the development from embryo to early adult. The locomotor activity rhythms of newly eclosed individuals were subsequently monitored in the lighting conditions, in which they had been reared, for several days and then in constant darkness. Circadian rhythms were clearly exhibited in constant darkness even in flies reared in constant light and constant darkness as well as flies reared in light-dark cycles, but the freerunning period differed among groups. The results suggest that the circadian clock is assembled without any cyclical photic information, and that the light influences the developing circadian clock of Drosophila to alter the freerunning period. The effects of light on the rhythm differed in some aspects between per(L) flies and the other two strains. Possible mechanisms through which light affects the developing circadian clock are discussed. Copyright 1997 Elsevier Science Ltd. All rights reserved

Journal Article↗
PubMedDate not supplied

[Monitoring the impact on international literature of scientific production of Italian researchers, in the disciplines of "psychiatry" and "psychology." The period of 1995-1999 compared with the period of 1985-1989].

AIM: The aim of this paper is to present the results of a citation analysis concerned with the impact on the international literature of Italian researchers in psychiatry and psychology and of sub-fields, within these two disciplines, in 1995-1999 compared to 1985-1989. METHOD: We used a database prepared by the Institute for Scientific Information (ISI) that included all papers, with at least one Italian author, working in Italy, which appeared in two periods (1995-1999 and 1985-1989) in psychiatric or psychological journals listed in Current Contents. A citation analysis concerning the following years, up to 1999, was performed. RESULTS: In 1995-1999 the most cited researchers were those involved in clinical psychology, psychiatry and psychopharmacology research. Neuropsychology, which dominated the period 1985-1989, underwent a clear-cut decline. CONCLUSIONS: Citation analysis, concerning relatively short periods of time (five years), appears to be a very helpful tool for monitoring the development of scientific research in specific disciplines and the trend of the scientific production of researchers.

Bibliometrics↗
PubMedDate not supplied

Periodic systems of molecules as elements of Shchukarev's "supermatrix", i.e. the chemical element periodic system.

Generations of Soviet scientists contributed invaluable insights into molecular classification. Unfortunately, this research is little appreciated in much of the world. Among these workers S. A. Shchukarev was of great importance. His and his followers' legacy includes a host of graphical displays showing enthalpies of formation of gaseous molecules from free atoms DeltaH(a) and standard enthalpies of formation of substances plotted on the atomic number of the central elements, on their oxidation states, their internuclear separations, and other variables for a wide range of molecules. These graphs serve as databases, from which data can be extracted, to moderate precision, visually. We discuss graphs for one very limited set, or "pleiade" (gas-phase oxides of nitrogen), and for three much broader sets, or subsystems (gas-phase fluorides of all main subgroup atoms and oxides of transition-metal atoms in gas-phase and in STP conditions). When dissolved in water, molecules lose their identities but periodicity is echoed in the acids and aquocations that are formed. We show, as an example in tabular form, that redox potentials of high-oxygen acids containing S, Se, and Te change concomitantly with DeltaH(a ) and DeltaH(f) of their hexafluorides. We present graphical evidence that three properties for cations of groups 1-3 (in the short version of the periodic chart) behave similarly and share the periodicity of the elements. One of the properties is related to the ionization potential, which is shown in a tabular example to vary concomitantly with energy of hydration. It was the ultimate goal of S. A. Shchukarev that the transformation of any one graphical database into any other, having different molecules under different conditions, would be made mathematically.

Journal Article↗
PubMed1998

Nucleosome positioning and periodicity of satellite DNA in the liver of aging rats. Nucleosome positioning and periodicity of satellite DNA.

The positioning of nucleosomes has been analysed by comparing the pattern of cutting sites of a probing reagent on chromatin and naked DNA. For this purpose, high molecular weight DNA and nuclei from the liver of young (18 +/- 2 weeks) and old (100 +/- 5 weeks) Wistar male rats were digested with micrococcal nuclease (MNase) and hybridized with 32P-labelled rat satellite DNA probe. A comparison of the ladder generated by MNase with chromatin and nuclei indicates long range organization of the satellite chromatin fiber with distinct non-random positioning of nucleosomes. However, the positioning of nucleosomes on satellite DNA does not vary with age. For studying the periodicity and subunit structure of satellite DNA, high molecular weight DNA from the liver of young and old rats were digested with different restriction enzymes. Surprisingly, no noteworthy age-related change is visible in the periodicity and subunit structural organization of the satellite DNA. These results suggest that the nucleosome positioning and the periodicity of liver satellite DNA do not vary with age.

Aging↗
PubMed1980

[Investigations of anemia of male rearing calves. 4. Relations between weight at birth, duration of keeping and increase of the ive weight in the period of the calves being fed on colostrum as well as the count erythrocytes in the weaning period of the calves].

With 195 male rearing calves which received concentrates ad libitum beside fluid feed with milk from their 5th day of life onward, investigations were made if and how far the characteristics of the development of the calves while they are fed on colostrum (body weight at birth, live weight increase and duration of keeping or stalling age) correlate with the hemoglobin content (Hb), the hematocrit (Hc) and the average corpuscular hemoglobin concentration (MCHC) of the animals on the 3rd, 28th resp. 56th day of keeping in the weaning period. There was a significant simple dependence particularly between body weight at birth, live weight increase and stalling age on the one hand and the hematologic values on the 3rd day of keeping in the weaning period on the other. A partial correlation analysis showed that the live weight increase while the calves were fed on colostrum was the main variable for all three hematologic parameters at the beginning of the weaning period of the calves. With increasing live weight, Hb, Hc and MCHC were diminished. This analysis was supplemented by the results of a cross--section investigation of the development of the milk and concentrate consumption and the Fe-intake of the calves fed on colostrum. The calculation of the Fe-balance showed that the mere ad libitum supply with feed supplements rich in Fe cannot prevent Fe-deficiency. Anaemia developing in the first month of the calves' lives is not a physiologic one but essentially caused by Fe-deficiency.

Anemia↗
PubMed1972

Circadian corticosteroid periodicity: critical period for abolition by neonatal injection of corticosteroid.

Circadian variation of corticosteroid concentrations in rat plasma is suppressed if corticosteroids are administered between days 2 to 4 of neonatal life, but not if they are given between days 12 to 14 of neonatal life. This indicates a critical period for the effect of corticosteroid administration on the central nervous system pathways regulating such periodicity. Circadian periodicity of corticosteroids is not affected by neonatal administration of testosterone or reserpine.

Adrenal Cortex Hormones↗
PubMed1982

Analysis of trends in cancer mortality in England and Wales during 1951-80 separating changes associated with period of birth and period of death.

Cancer mortality rates in England and Wales were analysed so to describe simultaneously changes affecting successive generations--that is, associated with period of birth--as well as changes associated with the period of which the deaths took place. When mortality from all cancers was considered the analysis implied that, contrary to a widely held view, the rate of death from cancer had been declining in each sex in successive generations. For men the decline had occurred in generations born since 1900, whereas for women the peak came in the 1925 birth group. On the other hand, there had been little decline in the rates associated with period of death. Five examples of cancers of specific organs for which the trends contrasted are shown.

Adolescent↗
PubMed1999

Provisional QTL for circadian period of wheel running in laboratory mice: quantitative genetics of period in RI mice.

Wheel running was monitored in B x D recombinant inbred (RI) mice under dark-dark (DD) conditions, and the mean circadian period was calculated for each strain. There were significant differences for this trait among B x D recombinant inbred strains (p < .0001) and a narrow-sense heritability of 21%. Analysis of strain means and variances indicates that at least four segregating loci contribute to the genetic variance for the free-running circadian period in this population. Correlation of the strain means for the circadian period of wheel running for each RI strain against the distribution of markers at over 1500 loci along the mouse genome identified a number of provisional quantitative trait loci (QTL). There were provisional QTL for wheel running at p < .001 on chromosome 11 and at p < .01 on chromosomes 1, 6, 9, 17, and 19. Most were in agreement with a second analysis done under similar conditions.

Animals↗
PubMed1999

Effect of overfeeding during the dry period on the rate of esterification in adipose tissue of dairy cows during the periparturient period.

The in vitro rate of esterification of fatty acids in adipose tissue was compared between cows that were fed at restricted energy intake and cows that were overfed during the dry period. Subcutaneous adipose tissue was biopsied at -1, 0.5, 1, and 3 wk from parturition. The basal in vitro rate of esterification was quantified, as well as the rate of esterification after the addition of glucose or glucose plus insulin. The basal rate in adipose tissue from overfed cows at -1 wk was higher than in adipose tissue from cows that were fed at restricted energy intake and indicated enhanced storage of triacylglycerols in adipose tissue of overfed cows at that time. The rate of esterification after the addition of glucose or glucose plus insulin was increased in both groups at each sampling time, but the mean rates, expressed as a percentage of the basal rates, were lower for overfed cows than for cows that were fed at restricted energy intake at 0.5 and 1 wk. Although the addition of glucose or glucose plus insulin increased esterification rates in adipose tissue from both groups of cows, adipose tissue from overfed cows was less sensitive to the addition of these compounds. In conclusion, overfeeding during the dry period predisposed cows to accumulate fat in adipose tissue during the prepartum period. The smaller increase in esterification rate after the addition of glucose or glucose plus insulin in adipose tissue of overfed cows indicates a lower ability of the adipose tissue to esterify circulating fatty acids or to reesterify mobilized fatty acids, which, combined with higher rates of lipolysis postpartum, contributes to continuously elevated concentrations of circulating nonesterified fatty acids postpartum, leading to a more severe hepatic lipidosis in overfed cows.

Adipose Tissue↗
PubMed1998

Medicare program; schedule of per-beneficiary limitations on home health agency costs for cost reporting periods beginning on or after October 1, 1997--HCFA. Final rule with comment period.

This final rule with comment period sets forth, in accordance with section 4602 of the Balanced Budget Act of 1997, a new schedule of limitations on home health agency costs that may be paid under the Medicare program for cost reporting periods beginning on or after October 1, 1997. These limitations are in addition to the per-visit limitations that were set forth in our January 2, 1998 notice with comment period.

Centers for Medicare and Medicaid Services, U.S.↗
PubMed1998

Medicare program; prospective payment system and consolidated billing for skilled nursing facilities; extension of comment period--HCFA. Notice of extension of comment period for interim final rule.

This document extends the comment period for an interim final rule with comment period that was published in the Federal Register on May 12, 1998 (63 FR 26252). That interim final rule implements provisions in section 4432 of the Balanced Budget Act of 1997 related to Medicare payment for skilled nursing facility services. Those include the implementation of a Medicare prospective payment system for skilled nursing facilities, consolidated billing, and a number of related changes. The comment period is extended for 60 days.

Centers for Medicare and Medicaid Services, U.S.↗
PubMed1998

Medicare program; prospective payment system and consolidated billing for skilled nursing facilities; reopening of comment period--HCFA. Notice of reopening of comment period for interim final rule.

We published an interim final rule with comment period in the Federal Register on May 12, 1998 (63 FR 26252). That interim final rule implements provisions in section 4432 of the Balanced Budget Act of 1997 related to Medicare payment for skilled nursing facility services. Those include the implementation of a Medicare prospective payment system for skilled nursing facilities, consolidated billing, and a number of related changes. A document published on July 13, 1998 extended the comment period for the May 12, 1998 interim final rule until September 11, 1998. This document reopens and extends the comment period for an additional 30 days after the date of publication of this notice. The document also clarifies the explanation of the Federal rates.

Centers for Medicare and Medicaid Services, U.S.↗
PubMed2000

Effects of paced respiration on heart period and heart period variability.

The present study investigated psychophysiological responses to paced respiration of different frequencies. Twenty men and 20 women (mean age: 24.3 years) underwent five breathing conditions (paced with 0.15 Hz, 0.20 Hz, 0.25 Hz, 0.30 Hz, and unpaced), each lasting 5 min. As dependent physiological measures heart period, and different heart period variability (HPV) parameters were assessed. Psychological variables consisted of mood estimates as well as rated accuracy and effort to follow the pacing rhythm. HPV decreased with higher breathing frequencies, under paced and unpaced conditions, whereas mood ratings did not change. Subjects indicated more effort and less accuracy in following the pacing signal, the more its frequency differed from their spontaneous breathing frequency. The comparison of a spontaneous breathing condition with a frequency-matched paced condition revealed that pacing per se provoked a reduction in heart period. Because this decrease was not accompanied by changes in any of the HPV frequency components, their validity as measures of autonomic control needs to be questioned.

Adult↗
PubMed1975

Effects on radioimmunoassay of digoxin of varying incubation periods for antigen---antibody reaction and varying periods of absorption by dextran-coated charcoal.

In radioimmunoassay of digoxin by the dextran-coated charcoal method, duration of the incubation period for the antigen-antibody reaction and time allowed for dextran-coated charcoal to absorb the free antigen are critical factors. We compared effects of prolonged periods of absorption on results obtained with five commercial kits. In all cases, the digoxin concentrations increased linearly with absorption time, but the increase varied among kits. Kallestad and New England Nuclear 3h-kits and the Squibb 125I-kit showed less increase (i.e., gave relatively consistent results after various periods of absorption); the Schwarz/Mann 125i-kit and Clinical Assays 3h-kit showed greater increases. Precautionary steps are outlined for radioimmunoassays by this technique.

Adsorption↗
PubMed2006

[A Dutch family with the hereditary periodic fever or tumour necrosis factor receptor-associated periodic syndrome (TRAPS)].

A 9-month-old girl was referred to the paediatrician because of fever of unknown origin. Since the age of 4 years she had recurrent attacks of muscle, joint and abdominal pain, in addition to periodic fever. Her sister and her mother had similar symptoms. The tumour necrosis factor (TNF) receptor-associated periodic syndrome (TRAPS) was suspected and confirmed by DNA analysis. Several members of the extended family were carriers of the same mutation. In patients with recurrent unexplained periods offever in combination with myalgia, arthralgia and abdominal pain, and in whom these symptoms also occur in members of the family, TRAPS should be considered as the cause. Glucocorticosteroids and etanercept, a TNF-receptor antagonist, may be effective in the treatment of attacks. Early recognition of this syndrome is important because of the risk of developing amyloidosis.

Adult↗