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Open access

Robert F. Bailey and Ismael G. Yero

Abstract

We demonstrate a construction of error-correcting codes from graphs by means of k-resolving sets, and present a decoding algorithm which makes use of covering designs. Along the way, we determine the k-metric dimension of grid graphs (i.e., Cartesian products of paths).

Open access

Nastaran Haghparast and Dariush Kiani

Abstract

An even factor of a graph is a spanning subgraph in which each vertex has a positive even degree. Jackson and Yoshimoto showed that if G is a 3-edge-connected graph with |G| ≥ 5 and v is a vertex with degree 3, then G has an even factor F containing two given edges incident with v in which each component has order at least 5. We prove that this theorem is satisfied for each pair of adjacent edges. Also, we show that each 3-edge-connected graph has an even factor F containing two given edges e and f such that every component containing neither e nor f has order at least 5. But we construct infinitely many 3-edge-connected graphs that do not have an even factor F containing two arbitrary prescribed edges in which each component has order at least 5.

Open access

Kristīne Šneidere, Nourah Alruwais, Nicholas G. Dowell, Voldemārs Arnis, Jeļena Harlamova, Kārlis Kupčs, Iveta Mintāle, Zane Ulmane, Andra Vanaga, Jeremy C. Young, Jennifer Rusted and Ainārs Stepens

Abstract

Due to increasing changes in demographics, maintaining cognitive functioning later in life has become both economic and social concerns, and thus finding a cost-effective solution is one of the priorities in research. Factors like physical and intellectual activities have been associated with better cognitive performance in later life. While several studies have considered the impact of short-term physical activity interventions on cognitive functioning, retrospective research focusing on life-time physical activity experience has been sparse. The aim of the study was to determine the relationship between memory performance and whole brain matter integrity in seniors with different regular life-long physical activity experience. Fifty-three Latvian seniors aged 65–85 (M = 72.25, SD = 5.03, 83% female) with no self-reported chronic disease participated in the study. Measures of memory, physical activity and whole brain matter integrity were obtained and analysed. The obtained results indicated no significant relationship between physical activity experience and short and long-term memory and whole brain matter integrity; however, brain matter integrity was significantly correlated with demographic factors like age and education. These results might be related to inadequate physical activity measures, as well as unequal physical activity experience in participants. In the future, more detailed assessment of physical activity experience should be considered.

Open access

Ilze Meldere, Liene Rucka, Santa Smilga, Zane Ābola and Aigars Pētersons

Abstract

Necrotising enterocolitis (NEC) is one of the leading causes of neonatal morbidity, mortality and surgical emergencies. As the survival rate of extremely low birth weight (ELBW) infants is rising, so is the risk of NEC. The aim of this study was to compare diagnostics parameters like clinical and radiological findings and laboratory indicators and the treatment and outcome of NEC patients from 2000 till 2007 (Group 1) and from 2008 till 2016 (Group 2) treated in Neonatology Clinic (NC) of Children’s Clinical University Hospital (CCUH). In the rectrospective study, 277 newborns were divided among Group I and Group II – 105 and 172 patients, respectively. There were no statistically significant differences between both study groups in mean gestational age and birth weight. In both groups the first signs of NEC appeared on average eight days after birth. Differences in the diagnostic method used in both groups were not statistically significant; specific radiological findings were seen in approximately 1/3 of the cases. There were statistically significant differences in the management of NEC and patient mortality. Conservative therapy was applied in 70.0% of patients in both study groups. Over time, peritoneal drainage (PPD) as the sole surgical treatment decreased by 6.4%, but PPD with following enterostomy decreased by 8.9%. In Group 2 mortality of NEC patients decreased by 17.4%. Mortality among surgically treated NEC patients decreased as well, by 9.0%.

Open access

Jing Wang, Zhangdong Ouyang and Yuanqiu Huang

Abstract

In [C. Thomassen, Tilings of the torus and the Klein bottle and vertex-transitive graphs on a fixed surface, Trans. Amer. Math. Soc. 323 (1991) 605–635], Thomassen described completely all (except finitely many) regular tilings of the torus S 1 and the Klein bottle N 2 into (3,6)-tilings, (4,4)-tilings and (6,3)-tilings. Many authors made great efforts to investigate the crossing number (in the plane) of the Cartesian product of an m-cycle and an n-cycle, which is a special (4,4)-tiling. For other tilings, there are quite rare results concerning on their crossing numbers. This motivates us in the paper to determine the crossing number of a hexagonal graph H 3, n, which is a special kind of (3,6)-tilings.

Open access

Urzula Nora Urbāne, Dita Gaidule-Logina, Dace Gardovska and Jana Pavāre

Abstract

The aim of this study was to investigate parental perception of febrile illness in their children, the most commonly applied management practices, as well as the expectations from clinicians when coping with fever in children. The study included parents of patients admitted to the Emergency and Observation Department of Children’s Clinical University Hospital in Rīga, Latvia. Data were collected via semi-structured interviews. All interviews were transcribed, and the transcripts analysed by inductive thematic analysis. Thirty-four parental interviews were analysed. Six themes emerged from the study, which were: signs causing concern; beliefs regarding fever; assessment and monitoring of fever; fever management practices; help-seeking behaviour; and expectations from the healthcare personnel. Many parents believed that fever could potentially cause injuries to the nervous system, kidneys, the brain, other internal organs, and even cause death. The perceived threat of fever resulted in frequent temperature measurements and administration of antipyretics. Meeting the emotional and information needs of the parents were considered as equally important to meeting the child’s medical needs. The study found that fever phobia exists among parents. Parental misconceptions of fever lead to overly zealous management practices. Parental education initiatives must be organised in order to improve parental knowledge of fever and its management in children.

Open access

Elmārs Rancāns and Anda Ķīvīte-Urtāne

Abstract

Annually, 7.9% of the general population in Latvia are suffering from depression. According to the official statistics, less than 8000 persons a year have been treated for depression in the state-paid health care services while the National Research Programme (NRP) BIOMEDICINE 2014–2017 found that more than 70 000 depressed patients annually are coming to family physicians (FPs) in Latvia. Within NRP researchers have developed an algorithm for diagnostics and treatment of depression and carried out ten educational courses for FPs all over Latvia in 2016. Data on the treatment of depression have been collected from the National Health Service (NHS) database from 01.01.2015 till 30.06.2017. Changes between the trained and control groups have been calculated for the time period before intervention — 2015–2016 and six months right after it. The “Depression School” was attended by 210 (15.2%) out of 1382 FPs, in contract with the NHS, who signed in for the course on first-to-come basis. There were no statistically significant demographic differences between trained and control groups, except, a larger proportion of FPs from rural places vs. the capital city attended the courses. Comparing the trained and control groups, during the period before the intervention there were on average 0.96 vs. 0.83 depressive episodes (F32) and 3.26 vs.1.74 recurrent depressive disorder (F33) episodes in 1/2 year (p < 0.001). Statistically significant increase was observed for F33 episodes (+1.42, p < 0.001), and numeric for F32 episodes (+0.18, p = 0.36) in the trained group of FPs in 2017. In total this gave a statistically significant (p < 0.001) increase by 43.6% of F33 diagnoses following the education course on depression for family physicians. Further analysis of data to access sustainability of training effect after 12 and 24 months are underway.

Open access

Ivars Brečs, Pēteris Stradiņš, Mārtiņš Kalējs, Uldis Strazdiņš, Iveta Ozolanta and Vladimir Kasyanov

Abstract

Aneurysms of ascending aorta are dilatation of the first part of the human aorta. They commonly show no clinical symptoms. This condition increases the risk of aorta dissection, which is a life-threatening condition. In this study we attempted to elucidate the changes in the biomechanical properties that occur in the dilated human ascending aorta. Fourteen specimens of ascending aorta wall were mechanically tested under a uniaxial tensile test. Two specimens from each ascending aorta anterior region were cut in longitudinal and circumferential directions. The samples were stretched until rupture of the sample occurred. The obtained experimental data were processed to determine maximal stress, maximal strain and the tangential modulus of elasticity in the linear part of the stress-strain curve. The obtained results showed a remarkable anisotropy of the ascending aorta tissue. We found higher strength of the tissue in the circumferential direction than in the longitudinal direction. There were no statistically significant differences between the strains of the samples. Tangential modulus of elasticity of the aortic samples in the longitudinal direction was significantly lower than the elastic modulus of the samples in the circumferential direction. The tissue in the circumferential direction is stronger and stiffer than in the longitudinal direction.

Open access

D. Pillone

Abstract

For a graph G = (V, E), a function f : V (G) → {1, 2, . . ., k} is a kranking for G if f(u) = f(v) implies that every uv path contains a vertex w such that f(w) > f(u). A minimal k-ranking, f, of a graph, G, is a k-ranking with the property that decreasing the label of any vertex results in the ranking property being violated. The rank number χr(G) and the arank number ψr(G) are, respectively, the minimum and maximum value of k such that G has a minimal k-ranking. This paper establishes an upper bound for ψr of a tree and shows the bound is sharp for perfect k-ary trees.

Open access

Valdis Pirsko, Inese Čakstiņa, Dina Nitiša, Marija Samoviča, Zanda Daneberga and Edvīns Miklaševičs

Abstract

Development of chemoresistance remains a significant limitation for the treatment of cancer and contributes to recurrence of the disease. Both intrinsic and acquired mechanisms of chemoresistance are characteristics of cancer stem cells (CSCs) or stem-like cells (SLCs). The aim of the study was to assess the stem-like properties in the breast cancer cell line MDA-MB-231 during and after pulsed treatment with doxorubicin (DOX) in comparison to the untreated controls.The experimental cultures were exposed to therapeutic concentration of DOX for 48 hours (treatment cultures), and subcultured to post-treatment cultures 24 hours after the removal of DOX. Stem-like properties of the cellular populations in the treatment and post--treatment cultures were assessed by the expression of the stem-cell marker genes (CD24, CD44, ITGA6, ITGB1, POU5F1, NANOG, ALDH1A1), colony-formation efficiency, growth rates, and sensitivity to DOX, 5-fluorouracil (5FU), cisplatin (CIS), and vinblastine (VBL). Exposure to DOX induced formation of giant polyploid cells that persisted in the post-treatment culture. The recovery period was characterised by a decrease in the proliferation rate, viability, and cellular adherence. The post-treatment cultures displayed decreased sensitivity to DOX and increased sensitivities to 5FU, CIS, and VBL. Cells treated with DOX displayed increased expression levels of CD24, CD44, and ALDH1A, while their expression levels at least partially normalised in the post-treatment culture. The post-treatment cultures demonstrated significantly increased colony-formation ability. During treatment with sub-lethal levels of doxorubicin and during the acute recovery period, the survival mechanisms in the breast cancer cell line MDA-MB-231 may be mediated by formation of the cellular population with stem-like properties.