333 research outputs found
Mean Curvature Flow of High Codimension in Complex Projective Space
We study the mean curvature flow of smooth -dimensional compact
submanifolds with quadratic pinching in the Riemannian manifold
. Our main focus is on the case of high codimension, .
We establish a codimension estimate that shows in regions of high curvature,
the submanifold becomes approximately codimension one in a quantifiable way.
This estimate enables us to prove at a singular time of the flow, there exists
a rescaling that converges to a smooth codimension-one limiting flow in
Euclidean space. Under a cylindrical type pinching, we show that this limiting
flow is weakly convex and moves by translation. These estimates allow us to
analyse the behaviour of the flow near singularities and establish the
existence of the limiting flow. Lastly, we prove a decay estimate that shows
that the rescaling converges smoothly to a totally geodesic limit in infinite
time. This behaviour is only possible if the dimension of the submanifold is
even. Our approach relies on the preservation of the quadratic pinching
condition along the flow and a gradient estimate that controls the mean
curvature in regions of high curvature. This result generalises the work of
Pipoli and Sinestrari on the mean curvature flow of submanifolds of the complex
projective space
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Cryopreservation of winter-dormant apple: III Bud water status and survival after cooling to -30°c and during recovery from cryopreservation
Abstract
In a continuing study to improve the efficiency of dormant bud cryopreservation for
tissues hardened in maritime climates, the water status of dormant buds was monitored
between -4°C and recovery from liquid nitrogen (LN). Measurement of water content, simple
thermal analysis and differential scanning calorimetry were employed. Buds did not lose
water during cooling to, or holding at -30°C indicating that cryodehydration and/or other
adaptive responses contributed during this essential step. A bud exotherm that was an artefact
of warming was detected due to necessary handling at -4°C before cooling to -30°C. There
were no significant differences between cultivars with respect to water status at -30°C or
immediately upon rewarming from LN despite significant differences in post-LN survival.
Buds rehydrated in 5 days, but up to 14 days may be needed for recovery for some cultivars.
In some instances buds could be grafted without rehydration, taking up water across the early
graft union
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Cryopreservation of winter-dormant apple buds: II - tissue water status after desiccation at -4°c and before further cooling
Abstract
The established protocol for the cryopreservation of winter-dormant Malus buds requires
that stem explants, containing a single, dormant bud are desiccated at -4°C, for up to 14 days,
to reduce their water content to 25-30% of fresh weight. Using three apple cultivars, with
known differences in response to cryopreservation, the pattern of evaporative water loss has
been characterised, including early freezing events in the bud and cortical tissues that allow
further desiccation by water migration to extracellular ice. There were no significant
differences between cultivars in this respect or in the proportions of tissue water lost during
the desiccation process. Differential Scanning Calorimetry (to -90°C) of intact buds indicated
that bud tissues of the cultivar with the poorest response to cryopreservation had the highest
residual water content at the end of the desiccation process and froze at the highest
temperature
Keywords: Malus, cryopreservation, dormant bud, dehydratio
Reply to Pallotti et al. Comment on "Boitrelle et al. The Sixth Edition of the WHO Manual for Human Semen Analysis: A Critical Review and SWOT Analysis. Life 2021, 11, 1368"
We would like to thank F. Pallotti and his colleagues for their positive comments [...
Appropriate use criteria for transesophageal echocardiography in Greece: A single center experience
Introduction The American College of Cardiology Foundation (ACCF) along with the American Society of Echocardiography (ASE) have enabled an accurate and clinically oriented evaluation of echocardiography indications by introducing Appropriate Use Criteria (AUC). Aim This study was designed to evaluate the degree of implementation of AUC for transesophageal echocardiography (TEE) during daily clinical practice in a tertiary university hospital in Greece during the era of economic recession. Materials and Methods From November 2014 to May 2014, we prospectively enrolled 300 patients who were examined in the Echocardiography Laboratory of the First University Cardiology. We recorded the participants' demographic and clinical characteristics using questionnaires and followed a scoring process according to ACCF guidelines to classify patients into an appropriate, inappropriate or uncertain category. The primary endpoint was to assess the association between the class of appropriateness and abnormal TEE results. Results In 89.4% of patients labelled appropriate, TEE was abnormal and significantly higher compared to patients of uncertain eligibility (50%) and to patients for whom TEE was considered to be inappropriate (35%) (p < 0.001). Subgroup analysis revealed a positive association between AUC and an increased possibility for abnormal TEE in female subjects (p = 0.001) as well as in patients who were younger than 50 years old (p < 0.001). A significant association was finally established between AUC and abnormal findings in TEE in patients with no risk factors (p = 0.028) and in patients with more than 3 risk factors (p = 0.013). Conclusion TEE constitutes a medical practice with an optimal cost/effectiveness ratio and should be further encouraged in our country in accordance with the austerity policy as long as the AUC are generally applied
Adolescent polycystic ovary syndrome according to the international evidence-based guideline
BACKGROUND: Diagnosing polycystic ovary syndrome (PCOS) during adolescence is challenging because features of normal pubertal development overlap with adult diagnostic criteria. The international evidence-based PCOS Guideline aimed to promote accurate and timely diagnosis, to optimise consistent care, and to improve health outcomes for adolescents and women with PCOS. METHODS: International healthcare professionals, evidence synthesis teams and consumers informed the priorities, reviewed published data and synthesised the recommendations for the Guideline. The Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) framework was applied to appraise the evidence quality and the feasibility, acceptability, cost, implementation and strength of the recommendations. RESULTS: This paper focuses on the specific adolescent PCOS Guideline recommendations. Specific criteria to improve diagnostic accuracy and avoid over diagnosis include: (1) irregular menstrual cycles defined according to years post-menarche; > 90 days for any one cycle (> 1 year post-menarche), cycles 45 days (> 1 to  35 days (> 3 years post-menarche) and primary amenorrhea by age 15 or > 3 years post-thelarche. Irregular menstrual cycles (< 1 year post-menarche) represent normal pubertal transition. (2) Hyperandrogenism defined as hirsutism, severe acne and/or biochemical hyperandrogenaemia confirmed using validated high-quality assays. (3) Pelvic ultrasound not recommended for diagnosis of PCOS within 8 years post menarche. (4) Anti-Müllerian hormone levels not recommended for PCOS diagnosis; and (5) exclusion of other disorders that mimic PCOS. For adolescents who have features of PCOS but do not meet diagnostic criteria an 'at risk' label can be considered with appropriate symptomatic treatment and regular re-evaluations. Menstrual cycle re-evaluation can occur over 3 years post menarche and where only menstrual irregularity or hyperandrogenism are present initially, evaluation with ultrasound can occur after 8 years post menarche. Screening for anxiety and depression is required and assessment of eating disorders warrants consideration. Available data endorse the benefits of healthy lifestyle interventions to prevent excess weight gain and should be recommended. For symptom management, the combined oral contraceptive pill and/or metformin may be beneficial. CONCLUSIONS: Extensive international engagement accompanied by rigorous processes honed both diagnostic criteria and treatment recommendations for PCOS during adolescence.Alexia S. Peña, Selma F. Witchel, Kathleen M. Hoeger, Sharon E. Oberfield, Maria G. Vogiatzi, Marie Misso, Rhonda Garad, Preeti Dabadghao and Helena Teed
Did Clinical Trials in Which Erythropoietin Failed to Reduce Acute Myocardial Infarct Size Miss a Narrow Therapeutic Window?
Background: To test a hypothesis that in negative clinical trials of erythropoietin in patients with acute myocardial infarction (MI) the erythropoietin (rhEPO) could be administered outside narrow therapeutic window. Despite overwhelming evidence of cardioprotective properties of rhEPO in animal studies, the outcomes of recently concluded phase II clinical trials have failed to demonstrate the efficacy of rhEPO in patients with acute MI. However, the time between symptoms onset and rhEPO administration in negative clinical trials was much longer that in successful animal experiments. Methodology/Principal Findings: MI was induced in rats either by a permanent ligation of a descending coronary artery or by a 2-hr occlusion followed by a reperfusion. rhEPO, 3000 IU/kg, was administered intraperitoneally at the time of reperfusion, 4 hrs after beginning of reperfusion, or 6 hrs after permanent occlusion. MI size was measured histologically 24 hrs after coronary occlusion. The area of myocardium at risk was similar among groups. The MI size in untreated rats averaged,42 % of area at risk, or,24 % of left ventricle, and was reduced by more than 50 % (p,0.001) in rats treated with rhEPO at the time of reperfusion. The MI size was not affected by treatment administered 4 hrs after reperfusion or 6 hrs after permanent coronary occlusion. Therefore, our study in a rat experimental model of MI demonstrates that rhEPO administered within 2 hrs of a coronary occlusion effectively reduces MI size, but when rhEPO was administered following a delay similar to that encountered in clinical trials, it had no effect on MI size
Tildacerfont in Adults With Classic Congenital Adrenal Hyperplasia: Results from Two Phase 2 Studies
Context: Congenital adrenal hyperplasia due to 21-hydroxylase deficiency (21OHD) is typically treated with lifelong supraphysiologic doses of glucocorticoids (GCs). Tildacerfont, a corticotropin-releasing factor type-1 receptor antagonist, may reduce excess androgen production, allowing for GC dose reduction.
Objective: Assess tildacerfont safety and efficacy.
Design and setting: Two Phase 2 open-label studies.
Patients: Adults with 21OHD.
Intervention: Oral tildacerfont 200 to 1000 mg once daily (QD) (n = 10) or 100 to 200 mg twice daily (n = 9 and 7) for 2 weeks (Study 1), and 400 mg QD (n = 11) for 12 weeks (Study 2).
Main outcome measure: Efficacy was evaluated by changes from baseline at 8 am in adrenocorticotropic hormone (ACTH), 17-hydroxyprogesterone (17-OHP), and androstenedione (A4) according to baseline A4 ≤ 2× upper limit of normal (ULN) or A4 > 2× ULN. Safety was evaluated using adverse events (AEs) and laboratory assessments.
Results: In Study 1, evaluable participants with baseline A4 > 2× ULN (n = 11; 19-67 years, 55% female) had reductions from baseline in ACTH (-59.4% to -28.4%), 17-OHP (-38.3% to 0.3%), and A4 (-24.2% to -18.1%), with no clear dose response. In Study 2, participants with baseline A4 > 2× ULN (n = 5; 26-63 years, 40% female) had ~80% maximum mean reductions in biomarker levels. ACTH and A4 were normalized for 60% and 40%, respectively. In both studies, participants with baseline A4 ≤ 2× ULN maintained biomarker levels. AEs (in 53.6% of patients overall) included headache (7.1%) and upper respiratory tract infection (7.1%).
Conclusions: For patients with 21OHD, up to 12 weeks of oral tildacerfont reduced or maintained key hormone biomarkers toward normal
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