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Hydrogen abstraction in astrochemistry: formation of ˙CH2CONH2 in the reaction of H atom with acetamide (CH3CONH2) and photolysis of ˙CH2CONH2 to form ketene (CH2CO) in solid para-hydrogen

Haupa KA, Ong WS, Lee YP

Phys Chem Chem Phys, 2020 Mar 18;22(11):6192-6201.
PMID: 32129366 DOI: 10.1039/c9cp06279c

Acetamide (CH3CONH2) is the largest molecule containing an amide bond that has been detected in an interstellar medium; it is considered to be a precursor for complex organic molecules (COM). We utilized the advantages of a para-hydrogen (p-H2) quantum-solid matrix host to perform efficient reactions of hydrogen atoms with CH3CONH2. The H-abstraction reaction from the methyl group of CH3CONH2 to produce the 2-amino-2-oxoethyl radical, ˙CH2CONH2, was observed as the sole reaction channel in solid p-H2 at 3.3 K, consistent with theoretical predictions that this reaction has the smallest barrier among all possible channels. Our results show that the amide bond of acetamide is unaffected by hydrogen exposure, but the hydrogen abstraction activates this molecule to react with other species on its methyl site to extend its size or to include other functional groups as a first step to form COM under prebiotic or abiotic conditions. This previously neglected path should be considered in the astrochemical modeling. The photolysis of ˙CH2CONH2 at wavelengths 380-450 nm produces ketene; this step might provide a plausible mechanism to explain the anti-correlated abundance of ketene and acetamide in some astronomical observations.
Comprehensive Geriatric Assessment (CGA) based risk factors for increased caregiver burden among elderly Asian patients with cancer

Rajasekaran T, Tan T, Ong WS, Koo KN, Chan L, Poon D, et al.

J Geriatr Oncol, 2016 05;7(3):211-8.
PMID: 27067580 DOI: 10.1016/j.jgo.2016.03.003

OBJECTIVE: This study aims to identify Comprehensive Geriatric Assessment (CGA) based risk factors to help predict caregiver burden among elderly patients with cancer.

MATERIALS AND METHOD: The study evaluated 249 patients newly diagnosed with cancer, aged 70years and above, who attended the geriatric oncology clinic at the National Cancer Centre Singapore between 2007 and 2010.

RESULTS: Out of 249 patients, 244 patients had information available on family caregiver burden and were analysed. On univariate analysis, ADL dependence, lower IADL scores, ECOG performance status of 3-4, higher fall risk, lower scores in dominant hand grip strength test and mini mental state examination, polypharmacy, higher nutritional risk, haemoglobin <12g/dL and presence of geriatric syndromes were significantly associated with mild to severe caregiver burden. On multivariate analysis, only ECOG performance status of 3-4 (odds ratio [OR], 4.47; 95% confidence interval [CI], 2.27-8.80) and haemoglobin <12g/dL (OR, 2.38; 95% CI, 1.14-4.99) were associated with an increased probability of mild to severe caregiver burden. The model achieved a good fit (Hosmer-Lemeshow's p=0.196) and discrimination (area under the curve [AUC]=0.742; bias-corrected AUC=0.737). Based on this, patients were stratified into 3 risk groups with different proportion of patients with increased caregiver burden (low risk: 3.9% vs intermediate risk: 18.8% vs high risk: 39.6%; p<0.001).

CONCLUSION: ECOG performance status and haemoglobin were associated with increased caregiver burden among elderly patients with cancer. Using these two factors in the clinic may help clinicians identify caregivers at risk and take preventive action to mitigate that.
Fulltext Identification of Comprehensive Geriatric Assessment Based Risk Factors for Malnutrition in Elderly Asian Cancer Patients

Tan T, Ong WS, Rajasekaran T, Nee Koo K, Chan LL, Poon D, et al.

PLoS One, 2016;11(5):e0156008.
PMID: 27231951 DOI: 10.1371/journal.pone.0156008

PURPOSE: Elderly cancer patients are at increased risk for malnutrition. We aim to identify comprehensive geriatric assessment (CGA) based clinical factors associated with increased nutritional risk and develop a clinical scoring system to identify nutritional risk in elderly cancer patients.
PATIENTS AND METHODS: CGA data was collected from 249 Asian patients aged 70 years or older. Nutritional risk was assessed based on the Nutrition Screening Initiative (NSI) checklist. Univariate and multivariate logistic regression analyses were applied to assess the association between patient clinical factors together with domains within the CGA and moderate to high nutritional risk. Goodness of fit was assessed using Hosmer-Lemeshow test. Discrimination ability was assessed based on the area under the receiver operating characteristics curve (AUC). Internal validation was performed using simulated datasets via bootstrapping.
RESULTS: Among the 249 patients, 184 (74%) had moderate to high nutritional risk. Multivariate logistic regression analysis identified stage 3-4 disease (Odds Ratio [OR] 2.54; 95% CI, 1.14-5.69), ECOG performance status of 2-4 (OR 3.04; 95% CI, 1.57-5.88), presence of depression (OR 5.99; 95% CI, 1.99-18.02) and haemoglobin levels <12 g/dL (OR 3.00; 95% CI 1.54-5.84) as significant independent factors associated with moderate to high nutritional risk. The model achieved good calibration (Hosmer-Lemeshow test's p = 0.17) and discrimination (AUC = 0.80). It retained good calibration and discrimination (bias-corrected AUC = 0.79) under internal validation.
CONCLUSION: Having advanced stage of cancer, poor performance status, depression and anaemia were found to be predictors of moderate to high nutritional risk. Early identification of patients with these risk factors will allow for nutritional interventions that may improve treatment tolerance, quality of life and survival outcomes.

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