976 resultados para group delay


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Recent downward revisions in the climate response to rising CO2 levels, and opportunities for reducing non-CO2 climate warming, have both been cited as evidence that the case for reducing CO2 emissions is less urgent than previously thought. Evaluating the impact of delay is complicated by the fact that CO2 emissions accumulate over time, so what happens after they peak is as relevant for long-term warming as the size and timing of the peak itself. Previous discussions have focused on how the rate of reduction required to meet any given temperature target rises asymptotically the later the emissions peak. Here we focus on a complementary question: how fast is peak CO2-induced warming increasing while mitigation is delayed, assuming no increase in rates of reduction after the emissions peak? We show that this peak-committed warming is increasing at the same rate as cumulative CO2 emissions, about 2% per year, much faster than observed warming, independent of the climate response.

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OBJECTIVE The results of Interventional Management of Stroke (IMS) III, Magnetic Resonance and REcanalization of Stroke Clots Using Embolectomy (MR RESCUE), and SYNTHESIS EXPANSION trials are expected to affect the practice of endovascular treatment for acute ischemic stroke. The purpose of this report is to review the components of the designs and methods of these trials and to describe the influence of those components on the interpretation of trial results. METHODS A critical review of trial design and conduct of IMS III, MR RESCUE, and SYNTHESIS EXPANSION is performed with emphasis on patient selection, shortcomings in procedural aspects, and methodology of data ascertainment and analysis. The influence of each component is estimated based on published literature including multicenter clinical trials reporting on endovascular treatment for acute ischemic stroke and myocardial infarction. RESULTS We critically examined the time interval between symptom onset and treatment and rates of angiographic recanalization to differentiate between "endovascular treatment" and "parameter optimized endovascular treatment" as it relates to the IMS III, MR RESCUE, and SYNTHESIS EXPANSION trials. All the three trials failed to effectively test "parameter optimized endovascular treatment" due to the delay between symptom onset and treatment and less than optimal rates of recanalization. In all the three trials, the magnitude of benefit with endovascular treatment required to reject the null hypothesis was larger than could be expected based on previous studies. The IMS III and SYNTHESIS EXPANSION trials demonstrated that rates of symptomatic intracerebral hemorrhages subsequent to treatment are similar between IV thrombolytics and endovascular treatment in matched acute ischemic stroke patients. The trials also indirectly validated the superiority/equivalence of IV thrombolytics (compared with endovascular treatment) in patients with minor neurological deficits and those without large vessel occlusion on computed tomographic/magnetic resonance angiography. CONCLUSIONS The results do not support a large magnitude benefit of endovascular treatment in subjects randomized in all the three trials. The possibility that benefits of a smaller magnitude exist in certain patient populations cannot be excluded. Large magnitude benefits can be expected with implementation of "parameter optimized endovascular treatment" in patients with ischemic stroke who are candidates for IV thrombolytics.

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Low-grade gliomas (LGGs) are a group of primary brain tumours usually encountered in young patient populations. These tumours represent a difficult challenge because many patients survive a decade or more and may be at a higher risk for treatment-related complications. Specifically, radiation therapy is known to have a relevant effect on survival but in many cases it can be deferred to avoid side effects while maintaining its beneficial effect. However, a subset of LGGs manifests more aggressive clinical behaviour and requires earlier intervention. Moreover, the effectiveness of radiotherapy depends on the tumour characteristics. Recently Pallud et al. (2012. Neuro-Oncology, 14: , 1-10) studied patients with LGGs treated with radiation therapy as a first-line therapy and obtained the counterintuitive result that tumours with a fast response to the therapy had a worse prognosis than those responding late. In this paper, we construct a mathematical model describing the basic facts of glioma progression and response to radiotherapy. The model provides also an explanation to the observations of Pallud et al. Using the model, we propose radiation fractionation schemes that might be therapeutically useful by helping to evaluate tumour malignancy while at the same time reducing the toxicity associated to the treatment.

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BACKGROUND Closed reduction and pinning is the accepted treatment choice for dislocated supracondylar humeral fractures in children (SCHF). Rates of open reduction, complications and outcome are reported to be dependent on delay of surgery. We investigated whether delay of surgery had influence on the incidence of open reduction, complications and outcome of surgical treatment of SCHFs in the authors' institution. METHODS Three hundred and forty-one children with 343 supracondylar humeral fractures (Gartland II: 144; Gartland III: 199) who underwent surgery between 2000 and 2009 were retrospectively analysed. The group consisted of 194 males and 149 females. The average age was 6.3 years. Mean follow-up was 6.2 months. Time interval between trauma and surgical intervention was determined using our institutional database. Clinical and radiographical data were collected for each group. Influence of delay of treatment on rates of open reduction, complications and outcome was calculated using logistic regression analysis. Furthermore, patients were grouped into 4 groups of delay (<6 h, n = 166; 6-12 h, n = 95; 12-24 h, n = 68; >24 h, n = 14) and the aforementioned variables were compared among these groups. RESULTS The incidence of open procedures in 343 supracondylar humeral fractures was 2.6 %. Complication rates were similar to the literature (10.8 %) primarily consisting of transient neurological impairments (9.0 %) which all were fully reversible by conservative treatment. Poor outcome was seen in 1.7 % of the patients. Delay of surgical treatment had no influence on rates of open surgery (p = 0.662), complications (p = 0.365) or poor outcome (p = 0.942). CONCLUSIONS In this retrospective study delay of treatment of SCHF did not have significant influence on the incidence of open reduction, complications, and outcome. Therefore, in SCHF with sufficient blood perfusion and nerve function, elective treatment is reasonable to avoid surgical interventions in the middle of the night which are stressful and wearing both for patients and for surgeons. LEVEL OF EVIDENCE III (retrospective comparative study).

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BACKGROUND L-serine plays an essential role in neuronal development and function. Although a non-essential amino acid, L-serine must be synthesised within the brain because of its poor permeability by the blood-brain barrier. Within the brain, its synthesis is confined to astrocytes, and its shuttle to neuronal cells is performed by a dedicated neutral amino acid transporter, ASCT1. METHODS AND RESULTS Using exome analysis we identified the recessive mutations, p.E256K, p.L315fs, and p.R457W, in SLC1A4, the gene encoding ASCT1, in patients with developmental delay, microcephaly and hypomyelination; seizure disorder was variably present. When expressed in a heterologous system, the mutations did not affect the protein level at the plasma membrane but abolished or markedly reduced L-serine transport for p.R457W and p.E256K mutations, respectively. Interestingly, p.E256K mutation displayed a lower L-serine and alanine affinity but the same substrate selectivity as wild-type ASCT1. CONCLUSIONS The clinical phenotype of ASCT1 deficiency is reminiscent of defects in L-serine biosynthesis. The data underscore that ASCT1 is essential in brain serine transport. The SLC1A4 p.E256K mutation has a carrier frequency of 0.7% in the Ashkenazi-Jewish population and should be added to the carrier screening panel in this community.

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Background: Malnutrition has a negative impact on optimal immune function, thus increasing susceptibility to morbidity and mortality among HIV positive patients. Evidence indicates that the prevalence of macro and micronutrient deficiencies (particularly magnesium, selenium, zinc, and vitamin C) has a negative impact on optimal immune function, through the progressive depletion of CD4 T-lymphocyte cells, which thereby increases susceptibility to morbidity and mortality among PLWH. Objective: To assess the short and long term effects of a nutrition sensitive intervention to delay the progression of human immune-deficiency virus (HIV) to AIDS among people living with HIV in Abuja, Nigeria. Methods: A randomized control trial was carried out on 400 PLWH (adult, male and female of different religious background) in Nigeria between January and December 2012. Out of these 400 participants, 100 were randomly selected for the pilot study, which took place over six months (January to June, 2012). The participants in the pilot study overlapped to form part of the scale-up participants (n 400) monitored from June to December 2012. The comparative effect of daily 354.92 kcal/d optimized meals consumed for six and twelve months was ascertained through the nutritional status and biochemical indices of the study participants (n=100 pilot interventions), who were and were not taking the intervention meal. The meal consisted of: Glycine max 50g (Soya bean); Pennisetum americanum 20g (Millet); Moringa oleifera 15g (Moringa); Daucus carota spp. sativa 15g (Carrot). Results: At the end of sixth month intervention, mean CD4 cell count (cell/mm3) for Pre-ART and ART Test groups increased by 6.31% and 12.12% respectively. Mean mid upper arm circumference (MUAC) for Pre-ART and ART Test groups increased by 2.72% and 2.52% within the same period (n 400). Comparatively, participants who overlapped from pilot to scale-up intervention (long term use, n 100) were assessed for 12 months. Mean CD4 cell count (cell/mm3) for Pre-ART and ART test groups increased by 2.21% and 12.14%. Mean MUAC for Pre-ART and ART test groups increased by 2.08% and 3.95% respectively. Moreover, student’s t-test analysis suggests a strong association between the intervention meal, MUAC, and CD4 count on long term use of optimized meal in the group of participants being treated with antiretroviral therapy (ART) (P<0.05). Conclusion: Although the achieved results take the form of specific technology, it suggests that a prolong consumption of the intervention meal will be suitable to sustain the gained improvements in the anthropometric and biochemical indices of PLWHIV in Nigeria.

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We worked toward developing a core outcome set for clinical research studies in polymyalgia rheumatica (PMR) by conducting (1) patient consultations using modified nominal group technique; (2) a systematic literature review of outcome measures in PMR; (3) a pilot observational study of patients presenting with untreated PMR, and further discussion with patient research partners; and (4) a qualitative focus group study of patients with PMR on the meaning of stiffness, using thematic analysis. (1) Consultations included 104 patients at 4 centers. Symptoms of PMR included pain, stiffness, fatigue, and sleep disturbance. Function, anxiety, and depression were also often mentioned. Participants expressed concerns about diagnostic delay, adverse effects of glucocorticoids, and fear of relapse. (2) In the systematic review, outcome measures previously used for PMR include pain visual analog scores (VAS), morning stiffness, blood markers, function, and quality of life; standardized effect sizes posttreatment were large. (3) Findings from the observational study indicated that asking about symptom severity at 7 AM, or "on waking," appeared more relevant to disease activity than asking about symptom severity "now" (which depended on the time of assessment). (4) Preliminary results were presented from the focus group qualitative study, encompassing broad themes of stiffness, pain, and the effect of PMR on patients' lives. It was concluded that further validation work is required before a core outcome set in PMR can be recommended. Nevertheless, the large standardized effect sizes suggest that pain VAS is likely to be satisfactory as a primary outcome measure for assessing response to initial therapy of PMR. Dissection of between-patient heterogeneity in the subsequent treatment course may require attention to comorbidity as a potential confounding factor.

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We worked toward developing a core outcome set for clinical research studies in polymyalgia rheumatica (PMR) by conducting (1) patient consultations using modified nominal group technique; (2) a systematic literature review of outcome measures in PMR; (3) a pilot observational study of patients presenting with untreated PMR, and further discussion with patient research partners; and (4) a qualitative focus group study of patients with PMR on the meaning of stiffness, using thematic analysis. (1) Consultations included 104 patients at 4 centers. Symptoms of PMR included pain, stiffness, fatigue, and sleep disturbance. Function, anxiety, and depression were also often mentioned. Participants expressed concerns about diagnostic delay, adverse effects of glucocorticoids, and fear of relapse. (2) In the systematic review, outcome measures previously used for PMR include pain visual analog scores (VAS), morning stiffness, blood markers, function, and quality of life; standardized effect sizes posttreatment were large. (3) Findings from the observational study indicated that asking about symptom severity at 7 AM, or "on waking," appeared more relevant to disease activity than asking about symptom severity "now" (which depended on the time of assessment). (4) Preliminary results were presented from the focus group qualitative study, encompassing broad themes of stiffness, pain, and the effect of PMR on patients' lives. It was concluded that further validation work is required before a core outcome set in PMR can be recommended. Nevertheless, the large standardized effect sizes suggest that pain VAS is likely to be satisfactory as a primary outcome measure for assessing response to initial therapy of PMR. Dissection of between-patient heterogeneity in the subsequent treatment course may require attention to comorbidity as a potential confounding factor.

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We have investigated whether fetal exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) causes defects in the male reproductive system of the rat, using chronically exposed rats to ensure continuous exposure of the fetus. 5-6 week old rats were exposed to control diet, or diet containing TCDD, to attain an average dose of 2.4, 8 and 46 ng TCDD kg-1 day-1 for twelve weeks, whereupon the rats were mated, and allowed to litter; rats were switched to control diet after parturition. Male offspring were allowed to develop until kills on PND70 (25 per group), or PND120 (all remaining animals). Offspring from the high dose group showed an increase in total litter loss, and the number of animals alive on post-natal day (PND) 4 in the high dose group was ~26% less than control. The high and medium dose offspring showed decreased weights at various ages. Balano-preputial separation was significantly delayed in all three dose groups, compared to control. There were no significant effects of maternal treatment when the offspring were subjected to a functional observational battery, or learning tests, with the exception that the high dose group showed a deficit in motor activity. 20 rats per group were mated to females, and there were no significant effects of maternal treatment on the fertility of these rats, nor on the F1 or F2 sex ratio. Sperm parameters at PND70 and 120 showed no significant effect of maternal treatment, with the exception that there was an increase in the proportion of abnormal sperm in the high dose group at PND70; this is associated with the developmental delay in puberty in this dose group. There were no remarkable findings of maternal treatment on organ weights, with the exception that testis weights were reduced by ~10% at PND70 (but not PND120), and although the experiment was sufficiently powered to detect small changes, ventral prostate weight was not reduced. There were no significant effects of maternal treatment upon histopathological comparison of high dose and control group organs. These data confirm that developmental exposure to TCDD shows no potent effect on adult sperm parameters or accessory sexual organs, but show that delay in BPS occurs after exposure to low doses of TCDD, and this is dependent upon whether TCDD is administered acutely or chronically.