1,168 results on '"Krumina, A"'
Search Results
2. Clinical effectiveness/child-patient and parent satisfaction of two topical fluoride treatments for caries: a randomised clinical trial
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Maldupa, Ilze, Innes, Nicola, Viduskalne, Ilona, Brinkmane, Anda, Senakola, Egita, Krumina, Karina, and Uribe, Sergio E.
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- 2024
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3. The phenotypic spectrum of PTCD3 deficiency
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Baiba Lace, Eissa Faqeih, Namik Kaya, Zita Krumina, Johannes A. Mayr, Ieva Micule, Nathan Thompson Wright, Melanie T. Achleitner, Hanan AlQudairy, Sander Pajusalu, Janis Stavusis, Pawel Zayakin, and Inna Inashkina
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Leigh‐like syndrome ,pentatricopeptide repeat ,PTCD3 ,Diseases of the endocrine glands. Clinical endocrinology ,RC648-665 ,Genetics ,QH426-470 - Abstract
Abstract The PTCD3 gene product (protein PTCD3 or MRPS39) forms the entry channel of the mitochondrial small ribosomal subunit and binds to single‐stranded mRNA. Here, we expand on the clinical manifestations of PTCD3 pathogenic variants by describing an early‐onset patient with Leigh‐like syndrome and two patients with milder form of disease, with combined oxidative phosphorylation deficiency. A 34‐year‐old male and his 33‐year‐old sister both have horizontal nystagmus, pronounced rough tremor, truncal ataxia, dysmetria, spasticity and hyperreflexia. The basal respiration rate decreased significantly for the male patient and his mother (p A, p.(Tyr394Ter) and c.805C>T, p.(His269Tyr). Tyr394Ter variant ablates the C‐terminal half of the protein, including a significant portion of the central fold. In silico modelling for the variant His269Tyr shows that the inclusion of the slightly larger tyrosine sidechain is well tolerated, with no significant change in either the position or the movement of the surrounding area. The third case is a 9‐year‐old boy, who has a global developmental delay, central hypotonia, hyperreflexia and abnormal MRI. PTCD3 pathogenic variant c.538+4A>G was identified by whole exome sequencing. To test the variant's effect on splicing, an RT‐PCR experiment was performed, which revealed skipping of an out‐of‐frame exon 7.
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- 2024
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4. Clinical effectiveness/child-patient and parent satisfaction of two topical fluoride treatments for caries: a randomised clinical trial
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Ilze Maldupa, Nicola Innes, Ilona Viduskalne, Anda Brinkmane, Egita Senakola, Karina Krumina, and Sergio E. Uribe
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Silver diammine fluoride ,Non-invasive caries management ,Early childhood caries ,Randomised controlled trial ,Patient-centred outcomes research ,Medicine ,Science - Abstract
Abstract Knowledge gaps exist regarding optimal silver diammine fluoride (SDF) regimens and the efficacy of new products for arresting dental caries in young children. We evaluated the effectiveness of 38%-SDF (SDI-RivaStar), Tiefenfluorid (TF) comparing with Placebo (P), all in conjunction with behavioural modification (BM), in preventing major complications (endodontic/extractions/pain)—a patient-centred outcome—due to early childhood caries over 12 months in children under 71-months. A six-arm, patient/parent-blinded, superiority, placebo-controlled randomised control trial at the university clinic in Riga, Latvia, from 1/9/20-31/8/22 (Protocol registration ISRCTN17005348). The trial tested six protocols, using three compounds (P/SDF/TF) under two regimes: annual and biannual (P1/P2/TF1/TF2/SDF1/SDF2) for major complications. Secondary outcomes included minor complications and parental satisfaction. All groups received BM. 373/427 randomised children (87.3%) completed the study. SDF2 had a significantly lower rate and risk of major (21.5%, OR = 0.28, 95%CI [0.11, 0.72], p 0.05). SDF biannual application with BM effectively prevented major complications of early childhood caries and was well accepted by children and their parents. Trial registration number: ISRCTN17005348, principal investigator: Ilze Maldupa, registration date: 30/06/2021. Clinical trial registration number: ISRCTN registry: ISRCTN17005348, https://doi.org/10.1186/ISRCTN17005348 , registration date: 30/06/2021.
- Published
- 2024
- Full Text
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5. Comparative Analysis of Physiological Vergence Angle Calculations from Objective Measurements of Gaze Position
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Linda Krauze, Karola Panke, Gunta Krumina, and Tatjana Pladere
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eccentric photorefractometry ,PowerRef 3 ,kappa angle ,calibration ,objective vergence ,Chemical technology ,TP1-1185 - Abstract
Eccentric photorefractometry is widely used to measure eye refraction, accommodation, gaze position, and pupil size. While the individual calibration of refraction and accommodation data has been extensively studied, gaze measurements have received less attention. PowerRef 3 does not incorporate individual calibration for gaze measurements, resulting in a divergent offset between the measured and expected gaze positions. To address this, we proposed two methods to calculate the physiological vergence angle based on the visual vergence data obtained from PowerRef 3. Twenty-three participants aged 25 ± 4 years viewed Maltese cross stimuli at distances of 25, 30, 50, 70, and 600 cm. The expected vergence angles were calculated considering the individual interpupillary distance at far. Our results demonstrate that the PowerRef 3 gaze data deviated from the expected vergence angles by 9.64 ± 2.73° at 25 cm and 9.25 ± 3.52° at 6 m. The kappa angle calibration method reduced the discrepancy to 3.93 ± 1.19° at 25 cm and 3.70 ± 0.36° at 600 cm, whereas the linear regression method further improved the accuracy to 3.30 ± 0.86° at 25 cm and 0.26 ± 0.01° at 600 cm. Both methods improved the gaze results, with the linear regression calibration method showing greater overall accuracy.
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- 2024
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6. Individual Variations in Vergence and Accommodation Responses Following Virtual Reality Gameplay
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Alona Sumarokova, Reinis Alksnis, Dagni Rappo, Karola Panke, Gunta Krumina, and Tatjana Pladere
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virtual reality ,visual functions ,binocular and accommodative disorders ,refraction shift ,accommodation lag ,accommodative microfluctuations ,Biology (General) ,QH301-705.5 - Abstract
Virtual reality (VR) can challenge the visual system, leading to temporary oculomotor changes, though the degree of change varies among individuals. While the vergence and accommodation system plays a crucial role in VR perception, it remains unclear whether individuals whose visual functions fall outside clinical norms experience larger changes. Thus, our study aimed to investigate whether changes in vergence and accommodation responses following VR gameplay differ between individuals with and without non-strabismic binocular and accommodative disorders. To assess this, both subjective and objective measurements were conducted before and after 20 min of playing Beat Saber. Results revealed significant alterations across both subjective measurements—near point of convergence and near point of accommodation—and objective measurements, including eye refraction, accommodation lag, and accommodative microfluctuations at far. Moreover, individuals with non-strabismic binocular and accommodative disorders exhibited larger accommodative microfluctuations at far compared to the control group. Overall, these findings indicate that considering individual differences in vergence and accommodation responses is important when evaluating the impact of VR on the visual system and can be helpful in the design and use of VR systems, particularly for individuals with binocular and accommodative disorders.
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- 2024
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7. Life by the Lake: Lubana Region and Its People in History and Present
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Solveiga Krumina-Konkova and Karlis Aleksandrs Konkovs
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mesolithic and neolithic settlements ,lake governance ,socio-ecological system ,local traditions ,triple governance dimensions model ,Folklore ,GR1-950 - Abstract
This article is about the coexistence of people and the lake, about the consequences and responsibility of people interfering with the natural processes of nature. Part of the framework of this research was the governance process of surface water resources in Latvia, particularly public lakes, which was studied using a three-dimensional governance framing model of complementary dimensions of governance stakeholders, governance content, and governance instruments in order to determine how the lake is governed, and how it affects local culture and what role does culture have in the lake and public water governance. Lake Lubans was selected for this research, as it is Latvia’s largest lake, and its area contains an important Natura 2000 protected site – the Lubana Wetland complex, in addition to the fact that the region has been inhabited since the Neolithic era. Lake Lubans was discovered to be governed by several national institutions, led by the Nature Conservation Agency, as the lake is located in a protected area, with the Ministry of Agriculture being responsible for the governance of the lake dam system and control of farmland around the lake. The territory of the Lake Lubans wetlands was one of the first campgrounds of ancient people in Europe after the glaciers’ retreat, which also determines its importance in the history and culture of Latvia and Europe. Lake governance is almost only focused on nature and environmental protection, with economic and social aspects needing to be considered, and residents and other stakeholders needing to be sufficiently involved in governance. Currently, their interests have yet to be considered. Altogether, lake governance also needs to be improved from its perspective. Lake Lubans and the Lubana Wetland complex have not had a mandatory governance plan since 2009, but the first is in development, again missing all governance dimensions mentioned above. It was also found that nature communication and nature tourism are not only just potential lake/nature governance sectors but, if properly developed, would be valuable lake governance instruments, keeping stakeholders’ participation while supporting national organisations.
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- 2023
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8. Role of precursor composition in the polymorph transformations, morphology control and ferromagnetic properties of nanosized TiO$_2$
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Zablotsky, Dmitry, Maiorov, Mikhail M., Krumina, Aija, Romanova, Marina, and Blums, Elmars
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Condensed Matter - Materials Science - Abstract
Pure phase and mixed phase TiO$_2$ nanoparticles have been produced using a pyrolytic method from a non-aqueous carboxylate precursor. The precursor was prepared by a multiphase cation exchange using pentanoic acid (C$_4$H$_9$COOH). The thermal stability, polymorph content, morphology, size distribution and surface region of the produced nanoparticles were studied by TGA/DSC, XRD, FTIR and TEM. High quality monodisperse nanoparticles have been produced in the size range from 7 to 27 nm. The nanoparticles showed room temperature ferromagnetism revealed by VSM within bound polaron model. The carboxylate precursor is a good alternative to standard sol-gel to produce nanoparticles free from impurities.
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- 2021
9. The Computerized Developmental Eye Movement (DEM) Test: Normative Data for School-Aged Children
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Daniela Protasevica, Evita Kassaliete, Anete Klavinska, Madara Alecka, Asnate Berzina, Viktorija Goliskina, Marija Koleda, Rita Mikelsone, Elizabete Ozola, Tomass Ruza, Evita Serpa, Aiga Svede, Daniela Toloka, Sofija Vasiljeva, Liva Volberga, Ilze Ceple, and Gunta Krumina
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school-aged children ,DEM test ,fixations ,reading disorders ,Biology (General) ,QH301-705.5 - Abstract
The aim of the study was to determine the normative data of the computerized DEM test for school-age children in Latvia. The study analyzed data on the performance (test execution time, duration, number of fixations, and number of errors) of 291 children while completing the computerized DEM test. Eye movement fixations were recorded with a Tobii Pro Fusion video-oculograph (250 Hz). According to the results of the study, the performance of the computerized DEM test is 77 %. For the study, 1 SD (one standard deviation) was chosen as a criterion for determining test norms. In the study, the norms of the computerized DEM test in Latvia were developed in class groups—from 1st to 6th grade (aged 7 to 12 years), the results were summarized in a table as the minimum performance values of the computerized DEM test.
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- 2024
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10. Quality of life assessment for nuclear, cortical, posterior subcapsular patients before and after cataract surgery
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Jansone-Langina, Zane, Solomatin, Andrei, Solomatins, Maksims, and Krumina, Gunta
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- 2024
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11. The persistent viral infections in the development and severity of myalgic encephalomyelitis/chronic fatigue syndrome
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Rasa-Dzelzkaleja, Santa, Krumina, Angelika, Capenko, Svetlana, Nora-Krukle, Zaiga, Gravelsina, Sabine, Vilmane, Anda, Ievina, Lauma, Shoenfeld, Yehuda, and Murovska, Modra
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- 2023
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12. Brain activity underlying visual search in depth when viewing volumetric multiplanar images
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Naderi, Mehrdad, Pladere, Tatjana, Alksnis, Reinis, and Krumina, Gunta
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- 2023
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13. Test for the Assessment of Crossed and Uncrossed Stereovision Acuity
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Volberga, Liva, Adami, Carlo, Strauta, Elizabete, Lyakhovetskii, Vsevolod, Krumina, Gunta, Magjarevic, Ratko, Series Editor, Ładyżyński, Piotr, Associate Editor, Ibrahim, Fatimah, Associate Editor, Lackovic, Igor, Associate Editor, Rock, Emilio Sacristan, Associate Editor, Dekhtyar, Yuri, editor, and Saknite, Inga, editor
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- 2023
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14. Assessment of Children Eye Movement Performance: An Eye-Tracker Approach
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Serpa, Evita, Alecka, Madara, Berzina, Asnate, Goliskina, Viktorija, Kassaliete, Evita, Klavinska, Anete, Koleda, Marija, Mikelsone, Rita, Ozola, Elizabete, Ruza, Tomass, Svede, Aiga, Toloka, Daniela, Vasiljeva, Sofija, Volberga, Liva, Ceple, Ilze, Krumina, Gunta, Magjarevic, Ratko, Series Editor, Ładyżyński, Piotr, Associate Editor, Ibrahim, Fatimah, Associate Editor, Lackovic, Igor, Associate Editor, Rock, Emilio Sacristan, Associate Editor, Dekhtyar, Yuri, editor, and Saknite, Inga, editor
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- 2023
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15. The Development of Objective and Quantitative Eye-Tracking-Based Method for the Diagnostics of Oculomotor Dysfunctions
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Krumina, Gunta, Ceple, Ilze, Goliskina, Viktorija, Kassaliete, Evita, Ruza, Tomass, Serpa, Evita, Svede, Aiga, Volberga, Liva, Magjarevic, Ratko, Series Editor, Ładyżyński, Piotr, Associate Editor, Ibrahim, Fatimah, Associate Editor, Lackovic, Igor, Associate Editor, Rock, Emilio Sacristan, Associate Editor, Dekhtyar, Yuri, editor, and Saknite, Inga, editor
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- 2023
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16. The Impact of Different Lighting Conditions on the Neural Processes Underlying Relative Depth Perception in 3D Visualization Using Volumetric Multiplanar Display
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Naderi, Mehrdad, Abdullayeva, Albina, Pladere, Tatjana, Krumina, Gunta, Magjarevic, Ratko, Series Editor, Ładyżyński, Piotr, Associate Editor, Ibrahim, Fatimah, Associate Editor, Lackovic, Igor, Associate Editor, Rock, Emilio Sacristan, Associate Editor, Dekhtyar, Yuri, editor, and Saknite, Inga, editor
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- 2023
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17. Vision Screening and Training Tool for School-Aged Children
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Slabcova, Jelena, Krumina, Gunta, Magjarevic, Ratko, Series Editor, Ładyżyński, Piotr, Associate Editor, Ibrahim, Fatimah, Associate Editor, Lackovic, Igor, Associate Editor, Rock, Emilio Sacristan, Associate Editor, Dekhtyar, Yuri, editor, and Saknite, Inga, editor
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- 2023
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18. Brain activity underlying visual search in depth when viewing volumetric multiplanar images
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Mehrdad Naderi, Tatjana Pladere, Reinis Alksnis, and Gunta Krumina
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Medicine ,Science - Abstract
Abstract The study investigated the cortical activity associated with 3D and 2D image perception on a volumetric multiplanar display by analyzing event-related potentials (ERPs) and power spectral density (PSD). In this study, we used a volumetric multiplanar display to present visual targets, and the brain signals were recorded via an EEG amplifier and analyzed using the EEGLAB toolbox on MATLAB. The study found no significant differences in amplitude between the 3D and 2D conditions across five occipital and parietal electrodes. However, there was a significant difference in latency of the P3 component on the Pz electrode. The analysis of PSD showed no significant differences between the two conditions, although there was a slightly higher alpha and beta activity observed in the 2D visualization. The study concluded that 3D image representation on a volumetric multiplanar display has no more sensory or cognitive load on the human brain than 2D representation, and that depth perception on a multiplanar display requires less brain activity.
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- 2023
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19. Exploring the joint potential of inflammation, immunity, and receptor-based biomarkers for evaluating ME/CFS progression
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Uldis Berkis, Simons Svirskis, Angelika Krumina, Sabine Gravelsina, Anda Vilmane, Diana Araja, Zaiga Nora-Krukle, and Modra Murovska
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Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) ,immunome ,inflammatome ,artificial intelligence (AI) supported diagnosis ,prognostic and therapy assessment biomarkers ,Immunologic diseases. Allergy ,RC581-607 - Abstract
BackgroundMyalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a debilitating chronic condition with no identified diagnostic biomarkers to date. Its prevalence is as high as 0.89% according to metastudies, with a quarter of patients bed- or home-bound, which presents a serious public health challenge. Investigations into the inflammation–immunity axis is encouraged by links to outbreaks and disease waves. Recently, the research of our group revealed that antibodies to beta2-adrenergic (anti-β2AdR) and muscarinic acetylcholine (anti-M4) receptors demonstrate sensitivity to the progression of ME/CFS. The purpose of this study is to investigate the joint potential of inflammatome—characterized by interferon (IFN)-γ, tumor necrosis factor (TNF)-α, interleukin (IL)-2, IL-21, Il-23, IL-6, IL-17A, Activin-B, immunome (IgG1, IgG2, IgG3, IgG4, IgM, and IgA), and receptor-based biomarkers (anti-M3, anti-M4, and anti-β2AdR)—for evaluating ME/CFS progression, and to identify an optimal selection for future validation in prospective clinical studies.MethodsA dataset was used originating from 188 individuals, namely, 54 healthy controls, 30 patients with a “mild” condition, 73 patients with a “moderate” condition, and 31 patients with a “severe” condition, clinically assessed by Fukuda/CDC 1994 and international consensus criteria. Inflammatome, immunome, and receptor-based biomarkers were determined in blood plasma via ELISA and multiplex methods. Statistical analysis was done via correlation analysis, principal component analysis, linear discriminant analysis, and random forest classification; inter-group differences were tested via nonparametric Kruskal–Wallis H test followed by the two-stage linear step-up procedure of Benjamini, Krieger, and Yekutieli, and via Mann–Whitney U test.ResultsThe association between inflammatome and immunome markers is broader and stronger (coupling) in the severe group. Principal component factoring separates components associated with inflammatome, immunome, and receptor biomarkers. Random forest modeling demonstrates an excellent accuracy of over 90% for splitting healthy/with condition groups, and 45% for splitting healthy/severity groups. Classifiers with the highest potential are anti-β2AdR, anti-M4, IgG4, IL-2, and IL-6.DiscussionThe association between inflammatome and immunome markers is a candidate for controlled clinical study of ME/CFS progression markers that could be used for treatment individualization. Thus, the coupling effects between inflammation and immunity are potentially beneficial for the identification of prognostic factors in the context of ME/CFS progression mechanism studies.
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- 2023
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20. The Advantages of an Integrative Approach in the Primary Healthcare of Post-COVID-19 and ME/CFS Patients
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Araja, Diana, primary, Krumina, Angelika, additional, Berkis, Uldis, additional, Nora-Krukle, Zaiga, additional, and Murovska, Modra, additional
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- 2023
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21. Implications of the Covid-19 Pandemic on High School Graduates’ Plans and Education Path
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Varpina, Zane, primary, Fredheim, Kata, additional, and Krumina, Marija, additional
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- 2023
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22. The persistent viral infections in the development and severity of myalgic encephalomyelitis/chronic fatigue syndrome
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Santa Rasa-Dzelzkaleja, Angelika Krumina, Svetlana Capenko, Zaiga Nora-Krukle, Sabine Gravelsina, Anda Vilmane, Lauma Ievina, Yehuda Shoenfeld, Modra Murovska, and the VirA project
- Subjects
Myalgic encephalomyelitis/chronic fatigue syndrome ,HHV-6A ,HHV-6B ,HHV-7 ,Human parvovirus B19 ,Medicine - Abstract
Abstract Background Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a multifactorial disease with an unexplained aetiology in which viral infections are possible trigger factors. The aim of this study was to determine the involvement of human herpesvirus (HHV)-6A/B, HHV-7, and parvovirus B19 (B19V) in the etiopathogenesis of ME/CFS. Methods 200 patients with clinically diagnosed ME/CFS and 150 apparently healthy individuals were enrolled in this study. Single-round, nested, and quantitative real-time polymerase chain reactions (PCR) were used to detect the presence and load of HHV-6A/B, HHV-7, and B19V. HHV-6A and HHV-6B were distinguished by PCR and restriction analysis. Immunoenzymatic assays were applied to estimate the presence of virus-specific antibodies and the level of cytokines. Results HHV-6A/B, HHV-7, and B19V specific antibodies were detected among patients and healthy individuals in 92.1% and 76.7%, 84.6% and 93.8%, and 78% and 67.4% of cases. HHV-6B had 99% of HHV-6 positive patients. Latent HHV-6A/B, HHV-7, and B19V infection/co-infection was observed in 51.5% of the patients and 76.7% of the healthy individuals, whereas active–45% of the ME/CFS patients and 8.7% of healthy individuals. HHV-6A/B load in patients with a persistent infection/co-infection in a latent and active phase was 262 and 653.2 copies/106 cells, whereas HHV-7 load was 166.5 and 248.5 copies/106 cells, and B19V-96.8 and 250.8 copies/106 cells, respectively. ME/CFS patients with persistent infection in an active phase had a higher level of pro-inflammatory cytokines (interleukin(IL)-6, tumor necrosis factor-alpha(TNF-α) and IL-12) and anti-inflammatory (IL-10) than with a persistent infection in a latent phase. A significant difference was revealed in the levels of TNF-α, IL-12, and IL-10 among the patient groups without infection, with latent infection/co-infection, active single, double and triple co-infection. The levels of TNF-α, IL-12, and IL-10 are significantly higher in patients with severe compared with a moderate course of ME/CFS. Conclusions Significantly more persistent HHV-6A/B, HHV-7, and B19V infection/co-infection in an active phase with a higher viral load and elevated levels of pro- and anti-inflammatory cytokines among patients with ME/CFS than healthy individuals indicate the importance of these infections/co-infections in ME/CFS development. The presence of these infections/co-infections influences the ME/CFS clinical course severity.
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- 2023
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23. Coaching to strengthen critical success factors in integrative care for chronic fatigue patients: the Patient Needs-Resources Model
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Diana Araja, Angelika Krumina, Zaiga Nora-Krukle, Marion E. Schneider, Uldis Berkis, and Modra Murovska
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myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) ,holistic approach ,multidisciplinary team ,patient engagement ,health-related quality of life (HRQoL) ,Neurosciences. Biological psychiatry. Neuropsychiatry ,RC321-571 - Abstract
Theoretical and empirical studies discover that an integrative approach is particularly important in chronic disorders and multiple long-term conditions, such as chronic fatigue. Chronic fatigue syndrome (CFS) is a classic example of a potentially severe, multisystemic illness with a wide diversity of symptoms and the corresponding diagnostic complexity. The prevalence of CFS-like syndromes expanded in the context of the COVID-19 pandemic, increasing the disorder and treatment burden. Thus, this article aimed to draw attention to the possibilities to strengthen the integrative approach to diagnosing and treating chronic disorders and multiple long-term conditions. The main critical success factors identified for integrative approaches were: a holistic approach, that provides a more comprehensive diagnostic and personalized treatment strategy, a multidisciplinary team, and patient engagement. The strengths and weaknesses of these factors were explored and coaching was identified as a potential unifying and reinforcing element. Coaching has a wide spectrum of manifestations clearly representing a holistic approach, that has been successfully used in multidisciplinary team building. Moreover, coaching exposes support addressing the patient engagement issues identified by the Patient Needs-Resources Model (PN-R Model) such as low levels of self-efficacy, optimism, and subjective well-being. Coaching may assist patients to identify and prioritize their goals, becoming aware of their personal resources, developing strategies for managing symptoms, and building skills to increase their self-efficacy and active engagement in the treatment process. Therefore, the authors emphasize coaching as a perspective element of optimization of patient care, that requires additional theoretical and long-term empirical research.
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- 2023
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24. Comparative Analysis of Physiological Vergence Angle Calculations from Objective Measurements of Gaze Position.
- Author
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Krauze, Linda, Panke, Karola, Krumina, Gunta, and Pladere, Tatjana
- Subjects
VISUAL accommodation ,GAZE ,CALIBRATION ,COMPARATIVE studies ,ANGLES ,ATTENTION - Abstract
Eccentric photorefractometry is widely used to measure eye refraction, accommodation, gaze position, and pupil size. While the individual calibration of refraction and accommodation data has been extensively studied, gaze measurements have received less attention. PowerRef 3 does not incorporate individual calibration for gaze measurements, resulting in a divergent offset between the measured and expected gaze positions. To address this, we proposed two methods to calculate the physiological vergence angle based on the visual vergence data obtained from PowerRef 3. Twenty-three participants aged 25 ± 4 years viewed Maltese cross stimuli at distances of 25, 30, 50, 70, and 600 cm. The expected vergence angles were calculated considering the individual interpupillary distance at far. Our results demonstrate that the PowerRef 3 gaze data deviated from the expected vergence angles by 9.64 ± 2.73° at 25 cm and 9.25 ± 3.52° at 6 m. The kappa angle calibration method reduced the discrepancy to 3.93 ± 1.19° at 25 cm and 3.70 ± 0.36° at 600 cm, whereas the linear regression method further improved the accuracy to 3.30 ± 0.86° at 25 cm and 0.26 ± 0.01° at 600 cm. Both methods improved the gaze results, with the linear regression calibration method showing greater overall accuracy. [ABSTRACT FROM AUTHOR]
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- 2024
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25. Individual Variations in Vergence and Accommodation Responses Following Virtual Reality Gameplay.
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Sumarokova, Alona, Alksnis, Reinis, Rappo, Dagni, Panke, Karola, Krumina, Gunta, and Pladere, Tatjana
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- 2024
- Full Text
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26. Why 2D layout in 3D images matters: evidence from visual search and eye-tracking
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Linda Krauze, Mara Delesa-Velina, Tatjana Pladere, and Gunta Krumina
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depth perception ,binocular disparity ,3D image ,2D layout ,item distance ,area of interest ,Human anatomy ,QM1-695 - Abstract
Precise perception of three-dimensional (3D) images is crucial for a rewarding experience when using novel displays. However, the capability of the human visual system to perceive binocular disparities varies across the visual field meaning that depth perception might be affected by the two-dimensional (2D) layout of items on the screen. Nevertheless, potential difficulties in perceiving 3D images during free viewing have received only a little attention so far, limiting opportunities to enhance visual effectiveness of information presentation. The aim of this study was to elucidate how the 2D layout of items in 3D images impacts visual search and distribution of maintaining attention based on the analysis of the viewer’s gaze. Participants were searching for a target which was projected one plane closer to the viewer compared to distractors on a multi-plane display. The 2D layout of items was manipulated by changing the item distance from the center of the display plane from 2° to 8°. As a result, the targets were identified correctly when the items were displayed close to the center of the display plane, however, the number of errors grew with an increase in distance. Moreover, correct responses were given more often when subjects paid more attention to targets compared to other items on the screen. However, a more balanced distribution of attention over time across all items was characteristic of the incorrectly completed trials. Thus, our results suggest that items should be displayed close to each other in a 2D layout to facilitate precise perception of 3D images and considering distribution of attention maintenance based on eye-tracking might be useful in the objective assessment of user experience for novel displays.
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- 2023
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27. The Lutheran and Roman Catholic Churches in Latvia
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Krumina-Konkova, Solveiga, Dragovic-Soso, Jasna, Series Editor, Subotic, Jelena, Series Editor, Petrova, Tsveta, Series Editor, Turcescu, Lucian, editor, and Stan, Lavinia, editor
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- 2021
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28. The phenotypic spectrum of PTCD3 deficiency
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Lace, Baiba, primary, Faqeih, Eissa, additional, Kaya, Namik, additional, Krumina, Zita, additional, Mayr, Johannes A., additional, Micule, Ieva, additional, Wright, Nathan Thompson, additional, Achleitner, Melanie T., additional, AlQudairy, Hanan, additional, Pajusalu, Sander, additional, Stavusis, Janis, additional, Zayakin, Pawel, additional, and Inashkina, Inna, additional
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- 2024
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29. Web-Based Intervention for Developing Long-Term Health Literacy of Individuals: Possibilities and Limitations
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Krumina, Aira Aija and Lubenko, Jelena
- Abstract
Web-based interventions (WBI) are purposefully developed online programs designed for wide range of users (clients, patients, health care specialists, as well as medical practitioners) which allow obtaining and using information on various issues related to health maintenance and improvement. On the basis of the analysis of scientific literature, the article provides an overview of WBI types and components, as well as a structural model of WBI and its user in the context of environment factors. The possibilities of using WBI for developing long-term health literacy of individuals are specified. By summarising the main advantages and limitations of using WBI, the possible suggestions for the WBI use and development are offered.
- Published
- 2016
30. Inclusivity in stereoscopic XR: Human vision first
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Tatjana Pladere, Ellen Svarverud, Gunta Krumina, Stuart J. Gilson, and Rigmor C. Baraas
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XR ,stereoscopic images ,stereo vision ,vision problems ,inclusivity ,HMD ,Electronic computers. Computer science ,QA75.5-76.95 - Abstract
Full accessibility to eXtended Reality Head-Mounted Displays (XR HMDs) includes a requirement for well-functioning eyes and visual system. Eye and vision problems—that affect visual skills and abilities to various degrees—are common and may prevent an individual from comfortably wearing and using XR HMDs. Yet, vision problems have gained little attention in the XR community, making it difficult to assess the degree of accessibility and how to increase inclusivity. This perspective article aims to highlight the need for understanding, assessing, and correcting common eye and vision problems to increase inclusivity—to help broaden a responsible uptake of XR HMDs. There is a need to apply an interdisciplinary, human-centered approach in research. Guidelines are given for conducting reproducible research to contribute to the development of more inclusive XR technologies, through consideration of the individual variations in human visual skills and abilities.
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- 2022
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31. Individual responsibilities, collective issues: The framing of dietary practices in Latvian media
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Orste, Lina, Krumina, Alise, Kilis, Emils, Adamsone-Fiskovica, Anda, and Grivins, Mikelis
- Published
- 2021
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32. The Effect of Stimulus Contrast and Spatial Position on Saccadic Eye Movement Parameters
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Viktorija Goliskina, Ilze Ceple, Evita Kassaliete, Evita Serpa, Renars Truksa, Aiga Svede, Linda Krauze, Sergejs Fomins, Gatis Ikaunieks, and Gunta Krumina
- Subjects
saccadic eye movements ,saccadic eye movement parameters ,stimulus parameters ,Biology (General) ,QH301-705.5 - Abstract
(1) Background: Saccadic eye movements are rapid eye movements aimed to position the object image on the central retina, ensuring high-resolution data sampling across the visual field. Although saccadic eye movements are studied extensively, different experimental settings applied across different studies have left an open question of whether and how stimulus parameters can affect the saccadic performance. The current study aims to explore the effect of stimulus contrast and spatial position on saccadic eye movement latency, peak velocity and accuracy measurements. (2) Methods: Saccadic eye movement targets of different contrast levels were presented at four different spatial positions. The eye movements were recorded with a Tobii Pro Fusion video-oculograph (250 Hz). (3) Results: The results demonstrate a significant effect of stimulus spatial position on the latency and peak velocity measurements at a medium grey background, 30 cd/m2 (negative and positive stimulus polarity), light grey background, 90 cd/m2 (negative polarity), and black background, 3 cd/m2 (positive polarity). A significant effect of the stimulus spatial position was observed on the accuracy measurements when the saccadic eye movement stimuli were presented on a medium grey background (negative polarity) and on a black background. No significant effect of stimulus contrast was observed on the peak velocity measurements under all conditions. A significant stimulus contrast effect on latency and accuracy was observed only on a light grey background. (4) Conclusions: The best saccadic eye movement performance (lowest latency, highest peak velocity and accuracy measurements) can be observed when the saccades are oriented to the right and left from the central fixation point. Furthermore, when presenting the stimulus on a light grey background, a very low contrast stimuli should be considered carefully.
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- 2023
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33. Comparative assessment of spatial perception in augmented reality depending on the consistency of depth cues
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Linda Krauze, Tatjana Pladere, Roberts Zabels, Rendijs Smukulis, Viktorija Barkovska, Vita Konosonoka, Ibrahim Musayev, Aiga Svede, and Gunta Krumina
- Subjects
visual perception ,augmented reality ,depth cues ,distance matching ,head-mounted display ,multiple planes. ,Science - Abstract
Discrepancies between depth cues (accommodation and vergence) is one of the major issues caused in a stereoscopic augmented reality at close viewing distances. It adversely affects not only user comfort but also spatial judgements. Images with consonant cues at different distances have become available due to the implementation of multifocal architecture in the head-mounted displays, although its effect on spatial perception has remained unknown. In this psychophysical study, we investigated the effects of consonant and conflicting depth cues on perceptual distance matching in the stereoscopic environment of augmented reality using a head-mounted display that was driven in two modes: multifocal mode and single-focal plane mode. The participants matched the distance of a real object with the images projected at three viewing distances (45 cm, 65 cm, and 115 cm). As a result, no significant differences in the accuracy of spatial perception were shown depending on the consistency of cues. However, the perceptual tasks were completed faster when the depth cues were consonant. Overall, the results of our experiment show that consonant depth cues facilitate faster judgements on spatial relations between real objects and images projected in augmented reality, which can be achieved when images are displayed using multiple depth planes in the head-mounted display. Further technological advancements might be required to improve the accuracy of spatial judgements in augmented reality.
- Published
- 2021
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34. Accommodative response in various design soft contact lens wearers
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Evita Kassaliete, Anastasija Gordeja, Karola Panke, Anete Petrova, and Gunta Krumina
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accommodative lag ,multifocal contact lenses ,near addition ,myopia control. ,Science - Abstract
The progression of myopia in young adults due to inadequate accommodation is currently one of the global research challenges. Studies have demonstrated that multifocal contact lenses have a different effect on accommodative response. The aim of this study was to assess the accommodative lag using various design multifocal contact lenses at different working distances. The study was conducted on 10 emmetropic subjects aged 22â28 years. An open-field autorefractor PowerRef 3 was used to assess the response of eye accommodation to stimuli placed at a distance of 25 cm and 40 cm for subjects wearing monofocal and multifocal contact lenses. To determine the effectiveness of contact lens design for accommodative lag compensation, the results of the accommodative lag with and without contact lenses were compared. The measured accommodative lag for stimuli at 40 cm was 1.05 ± 0.11 D and for stimuli at 25 cm 1.53 ± 0.11 D. Regarding the effect of multifocal contact lenses, it was determined that the near vision power zone in the centre of the lens reduces the accommodative lag, while the respective distance vision power zone does not produce a statistically significant change. The near power zone in the centre of the multifocal contact lens effectively affects the accommodative lag by reducing accommodation inaccuracy as effectively as spherical contact lenses with positive power. The addition design for multifocal lenses (Med or Hi) does not significantly affect the accommodative lag. The results of centre-distance multifocal contact lenses depend on the strength of the addition used.
- Published
- 2021
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- View/download PDF
35. The effect of blue-light-blocking lenses on retinal straylight
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Gatis Ikaunieks, Inese Petrovica, Kristine Kalnica-Dorosenko, and Gunta Krumina
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spectacle lenses ,retinal straylight ,blue light. ,Science - Abstract
Sometimes yellow-tinted lenses are recommended to help improve visual quality. As yellow lenses filter blue light, it is believed that their use could decrease the intensity of scattered light in the eye (retinal straylight). However, the results of some studies have contradicted this assumption (Van Os et al. 2017). Currently various nontinted blue-light-blocking lenses are used to protect the eyes from short-wavelength light. The objective of this study was to determine whether blue-light-blocking lenses affect the levels of retinal straylight in the eye. A straylight meter (C-Quant, Oculus) was used for retinal straylight measurements. The measurements were performed under four different conditions: 1. without a spectacle lens in front of the eye, 2. with a plano lens without an antireflective (AR) coating, 3. with a lens with a blue-light-blocking coating, and 4. with a yellow-tinted lens without an AR coating. The study involved 37 subjects with a mean age of 22 ± 1.3 (SD) years. No significant differences in straylight parameters (s) (p > 0.05) were observed for measurements obtained without a lens in front of the eye (log[s] = 0.90 ± 0.02 [SE]), with the uncoated lens (log[s] = 0.92 ± 0.02) and with the lens with a blue-light-filtering coating (log[s] = 0.92 ± 0.02). Retinal straylight was significantly increased with the use of a yellow-tinted lens (log[s] = 0.96 ± 0.02) compared with no lens (p < 0.001). Neither yellow-tinted lenses nor nontinted blue-light-blocking lenses reduce the levels of retinal straylight in the eye.
- Published
- 2021
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36. The use of specialized computer games for the treatment of amblyopia in Latvia
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Kristine Kalnica-Dorosenko, Sandra Valeina, Aiga Svede, and Gunta Krumina
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amblyopia ,specialized computer games ,occlusions ,amblyopia treatment ,stereovision. ,Science - Abstract
The classical treatment option for amblyopia in Latvia is occlusions of the non-amblyopic eye. The newest methods involve specialized computer games that involve both eyes in visual processing during the treatment as well as stimulate binocularity. To assess the efficiency of specialized computer games in the treatment of amblyopia in school-age children in Latvia, 237 children (7â18 years old) participated in the experiment, of whom only 22 completed it: 11 participants had occlusion therapy, 11 participants played the specialized dichoptic computer game Tetris®. The visual acuity of the amblyopic eye as well as stereopsis were evaluated at near and far distances before the treatment, 2 months and 4 months after the beginning of the treatment. The results show statistically significant improvement in visual acuity in both treatment groups after four months of therapy. The extent of improvement is similar in both groups. Specialized computer games for amblyopia treatment may be recommended to patients from an age when they are able to use a computer along with a keyboard and computer mouse, who want to improve their visual acuity in the amblyopic eye but are not willing to use occlusions. The only requirement for using specialized games is that the patients need to have binocular single vision. In conclusion, the use of specialized computer games is an alternative type of amblyopia treatment compared to occlusion therapy.
- Published
- 2021
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- View/download PDF
37. Study of phase composition, photocatalytic activity, and photoluminescence of TiO2 with Eu additive produced by the extraction-pyrolytic method
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Serga, Vera, Burve, Regina, Krumina, Aija, Pankratova, Viktorija, Popov, Anatoli I., and Pankratov, Vladimir
- Published
- 2021
- Full Text
- View/download PDF
38. Breastfeeding preterm born infant: Chance and challenge
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Zukova, Svetlana, Krumina, Valda, and Buceniece, Jelena
- Published
- 2021
- Full Text
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39. Biomarkers in the diagnostic algorithm of myalgic encephalomyelitis/chronic fatigue syndrome
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Sabine Gravelsina, Anda Vilmane, Simons Svirskis, Santa Rasa-Dzelzkaleja, Zaiga Nora-Krukle, Katrine Vecvagare, Angelika Krumina, Iana Leineman, Yehuda Shoenfeld, and Modra Murovska
- Subjects
ME/CFS ,β2AdR antibodies ,AChR antibodies ,HHV-6 ,biomarkers ,Immunologic diseases. Allergy ,RC581-607 - Abstract
Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a complex disease that is mainly diagnosed based on its clinical symptoms. Biomarkers that could facilitate the diagnosis of ME/CFS are not yet available; therefore, reliable and clinically useful disease indicators are of high importance. The aim of this work was to analyze the association between ME/CFS clinical course severity, presence of HHV-6A/B infection markers, and plasma levels of autoantibodies against adrenergic and muscarinic acetylcholine receptors. A total of 134 patients with ME/CFS and 33 healthy controls were analyzed for the presence of HHV-6A/B using PCRs, and antibodies against beta2-adrenergic receptors (β2AdR) and muscarinic acetylcholine receptors (M3 AChR and M4 AChR) using ELISAs. HHV-6A/B U3 genomic sequence in whole-blood DNA was detected in 19/31 patients with severe ME/CFS, in 18/73 moderate ME/CFS cases, and in 7/30 mild ME/CFS cases. Severity-related differences were found among those with a virus load of more than 1,000 copies/106 PBMCs. Although no disease severity-related differences in anti-β2AdR levels were observed in ME/CFS patients, the median concentration of these antibodies in plasma samples of ME/CFS patients was 1.4 ng/ml, while in healthy controls, it was 0.81 ng/ml, with a statistically significant increased level in those with ME/CFS (p = 0.0103). A significant difference of antibodies against M4 AChR median concentration was found between ME/CFS patients (8.15 ng/ml) and healthy controls (6.45 ng/ml) (p = 0.0250). The levels of anti-M4 plotted against disease severity did not show any difference; however, increased viral load correlates with the increase in anti-M4 level. ME/CFS patients with high HHV-6 load have a more severe course of the disease, thus confirming that the severity of the disease depends on the viral load—the course of the disease is more severe with a higher viral load. An increase in anti-M4 AchR and anti-β2AdR levels is detected in all ME/CFS patient groups in comparison to the control group not depending on ME/CFS clinical course severity. However, the increase in HHV-6 load correlates with the increase in anti-M4 level, and the increase in anti-M4 level, in turn, is associated with the increase in anti-β2AdR level. Elevated levels of antibodies against β2AdR and M4 receptors in ME/CFS patients support their usage as clinical biomarkers in the diagnostic algorithm of ME/CFS.
- Published
- 2022
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- View/download PDF
40. Study of phase composition, photocatalytic activity, and photoluminescence of TiO2 with Eu additive produced by the extraction-pyrolytic method
- Author
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Vera Serga, Regina Burve, Aija Krumina, Viktorija Pankratova, Anatoli I. Popov, and Vladimir Pankratov
- Subjects
Extraction-pyrolytic method ,Nanocrystalline TiO2 ,Eu3+ ,Degradation of methylene blue ,Photoluminescence ,Mining engineering. Metallurgy ,TN1-997 - Abstract
Due to the unique properties and wide array of applications of nanocrystalline materials based on titanium dioxide, the study of new synthesis approaches remains relevant. In this study, within the framework of the extraction-pyrolytic method (EPM), we suggest using the mixtures of Ti- and Eu-containing organic extracts based on valeric acid as precursors for fabrication of nanocrystalline TiO2-based powders with different Eu content: 0.5 mol%, 5 mol%, and 50 mol%. The thermal behavior of individual metal-containing extracts and their mixture was studied by thermogravimetric analysis and differential scanning calorimetry (TGA–DSC). To characterize phase composition and morphology of produced materials, the X-ray diffraction (XRD) method and scanning electron microscopy (SEM) were used. Photoluminescence properties of Eu3+ ions in TiO2 nanocrystals have been studied. Photocatalytic activity of produced materials was tested in the reaction of methylene blue (MB) oxidation under UV-VIS irradiation. Correlation between synthesis parameters (Eu content and pyrolysis temperature) and properties of produced materials (phase composition, photoluminescence and photocatalytic properties) has been studied. It was demonstrated that the presence of a Eu-containing extract in the precursor mixture increases the anatase-to-rutile phase transformation temperature. The highest efficiency (degradation degree of MB 96%) was shown by TiO2 powder consisting of mixed polymorphs, anatase (main phase) and rutile, with 0.5 mol% Eu additive. It was shown that anatase-to-rutile phase transformation in TiO2:Eu3+ nanoparticles manifests in a degradation of Eu3+ luminescence intensity.
- Published
- 2021
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41. From Synthesis to Clinical Trial: Novel Bioinductive Calcium Deficient HA/β-TCP Bone Grafting Nanomaterial
- Author
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Oleg Mishchenko, Anna Yanovska, Oksana Sulaieva, Roman Moskalenko, Mykola Pernakov, Yevheniia Husak, Viktoriia Korniienko, Volodymyr Deineka, Oleksii Kosinov, Olga Varakuta, Simonas Ramanavicius, Suren Varzhapetjan, Almira Ramanaviciene, Dzanna Krumina, Gundega Knipše, Arunas Ramanavicius, and Maksym Pogorielov
- Subjects
bone grafting nanomaterials ,bionanotechnology ,maxillary sinus lifting ,synthetic bone materials ,HA/β-TCP ,bionanomaterials ,Chemistry ,QD1-999 - Abstract
Maxillary sinus augmentation is a commonly used procedure for the placement of dental implants. However, the use of natural and synthetic materials in this procedure has resulted in postoperative complications ranging from 12% to 38%. To address this issue, we developed a novel calcium deficient HA/β-TCP bone grafting nanomaterial using a two-step synthesis method with appropriate structural and chemical parameters for sinus lifting applications. We demonstrated that our nanomaterial exhibits high biocompatibility, enhances cell proliferation, and stimulates collagen expression. Furthermore, the degradation of β-TCP in our nanomaterial promotes blood clot formation, which supports cell aggregation and new bone growth. In a clinical trial involving eight cases, we observed the formation of compact bone tissue 8 months after the operation, allowing for the successful installation of dental implants without any early postoperative complications. Our results suggest that our novel bone grafting nanomaterial has the potential to improve the success rate of maxillary sinus augmentation procedures.
- Published
- 2023
- Full Text
- View/download PDF
42. The Computerized Developmental Eye Movement (DEM) Test: Normative Data for School-Aged Children.
- Author
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Protasevica, Daniela, Kassaliete, Evita, Klavinska, Anete, Alecka, Madara, Berzina, Asnate, Goliskina, Viktorija, Koleda, Marija, Mikelsone, Rita, Ozola, Elizabete, Ruza, Tomass, Serpa, Evita, Svede, Aiga, Toloka, Daniela, Vasiljeva, Sofija, Volberga, Liva, Ceple, Ilze, and Krumina, Gunta
- Published
- 2024
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43. The phenotypic spectrum of PTCD3 deficiency.
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Lace, Baiba, Faqeih, Eissa, Kaya, Namik, Krumina, Zita, Mayr, Johannes A., Micule, Ieva, Wright, Nathan Thompson, Achleitner, Melanie T., AlQudairy, Hanan, Pajusalu, Sander, Stavusis, Janis, Zayakin, Pawel, and Inashkina, Inna
- Published
- 2024
- Full Text
- View/download PDF
44. Porous biomorphic ceramics for catalytic decomposition of phenol
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Sedmale, Gaida, Rundans, Maris, Randers, Martins, Grase, Liga, and Krumina, Aija
- Published
- 2020
- Full Text
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45. P1222 Gut microbiome differences regarding lifestyle and the history of COVID-19 infection in ulcerative colitis patients
- Author
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Straume, Z, primary, Krumina, N, additional, Elbere, I, additional, Rozenberga, M, additional, Rudzite, D, additional, Ozolina, J, additional, Pjalkovskis, J, additional, Megnis, K, additional, Skuja, V, additional, and Krumina, A, additional
- Published
- 2024
- Full Text
- View/download PDF
46. Determinants of Bank Profitability: Case of Latvia
- Author
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Krumina Dace, Lejniece Ilona, and Skvarciany Viktorija
- Subjects
bank performance ,performance factors ,banking sector ,commercial banks ,g21 ,Business ,HF5001-6182 ,Economics as a science ,HB71-74 - Abstract
Research purpose. The goal of the current paper is to investigate the impact of internal factors on bank performance. All the performance indicators and explanatory factors have been distinguished from the scientific literature.
- Published
- 2020
- Full Text
- View/download PDF
47. The impact of irregular corneal shape parameters on visual acuity and contrast sensitivity
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Sanita Liduma, Artis Luguzis, and Gunta Krumina
- Subjects
Keratoconus ,Visual acuity ,Contrast sensitivity ,Apex slope ,Corneal surface ,Ophthalmology ,RE1-994 - Abstract
Abstract Background To understand which irregular corneal parameters determine the visual quality in keratoconus subjects. Methods The cross-sectional study examined the eyes of 44 subjects, graded from the first to third keratoconus stages by Amsler-Krumeich classification. We obtained measurements in two ways: (a) by projecting two perpendicular axes onto a cornea (first, through the central point of the cornea and keratoconus apex; second, as the perpendicular axis) to read the elevation values at points on these axes as parameters characterising the corneal surface; (b) by projecting circles with different diameters around the central part of the cornea (1, 2, and 3 mm) and reading elevation values at points equally displaced on these circles as parameters characterising an anterior surface slope. Irregular corneal shape parameters’ correlations with visual acuity and contrast sensitivity were determined in order to understand which corneal slope parameter has the strongest correlation with visual acuity and contrast sensitivity. Results Parameters characterising the corneal surface’s correlations with contrast sensitivity were from r = 0.25 (p = 0.03) at 3 cpd to r = 0.47 (p
- Published
- 2020
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- View/download PDF
48. Ectomycorrhizal Fungal Transformation of Dissolved Organic Matter: Consequences for Reductive Iron Oxide Dissolution and Fenton-Based Oxidation of Mineral-Associated Organic Matter
- Author
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Lelde Krumina, Michiel Op De Beeck, Viktoriia Meklesh, Anders Tunlid, and Per Persson
- Subjects
ferrihydrite ,goethite ,hydroxyl radicals ,reductive dissolution ,Fenton reactions ,Paxillus involutus ,Science - Abstract
Recent studies have shown that dissolved organic matter (DOM) decomposed by ectomycorrhizal (ECM) fungi increases adsorptive properties of organic matter towards soil mineral surfaces. Concomitantly, ECM fungi secrete secondary metabolites with iron reducing capacity that are thought to participate in non-enzymatic Fenton-based decomposition of DOM. The aim of this study was to investigate if the iron reduction induced by the ECM fungus Paxillus involutus during organic matter decomposition was conserved in the decomposed DOM. We explored how the modified DOM reductively dissolved ferrihydrite and goethite nanoparticles and how these processes affected the reactions with H2O2 and the Fenton-based oxidation of mineral-associated organic matter. Culture filtrates were obtained from incubation of the ECM fungus on DOM from forest litter of a spruce forest. This modified DOM was separated by extraction into an ethyl acetate and a water fraction. These fractions were reacted with ferrihydrite and goethite in absence and presence of H2O2. Dissolved Fe2+ and HO• were measured and the reactions at the iron oxide-water interfaces were monitored in real-time with in-situ IR spectroscopy. Experiments showed that decomposition of DOM by P. involutus generated a modified DOM that displayed an increased and persistent reductive capacity. Most of the reductants were isolated in the aromatic- and carboxyl-dominated ethyl acetate fraction but some reduction capacity was also captured in the water fraction mainly containing carbohydrates. Reductive dissolution was more extensive for ferrihydrite than goethite, and this process generated significant oxidation of the DOM-ferrihydrite associations. Oxidation of adsorbed DOM was triggered by H2O2via heterogenous and homogeneous Fenton reactions. These oxidation processes were favored by ferrihydrite because of a high reduction potential and a high efficiency of heterogeneous Fenton as compared to goethite. An optimal timing between the heterogeneous and homogeneous Fenton processes triggered extensive radical oxidation of the DOM-ferrihydrite associations generating a high concentration of surface-associated oxalate. Overall, the results show that organic matter associated with ferrihydrite may be more susceptible to radical oxidation than on goethite, and that fungal decomposition of DOM in general may have consequences for other important soil processes such as mineral dissolution, adsorption and initiation of radical reactions.
- Published
- 2022
- Full Text
- View/download PDF
49. Figure–Ground Segmentation and Biological Motion Perception in Peripheral Visual Field
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Ilze Ceple, Jurgis Skilters, Vsevolod Lyakhovetskii, Inga Jurcinska, and Gunta Krumina
- Subjects
biological motion ,visual periphery ,cortical magnification ,Neurosciences. Biological psychiatry. Neuropsychiatry ,RC321-571 - Abstract
Biological motion perception is a specific type of perceptual organization, during which a clear image of a moving human body is perceptually generated in virtue of certain core light dots representing the major joint movements. While the processes of biological motion perception have been studied extensively for almost a century, there is still a debate on whether biological motion task performance can be equally precise across all visual field or is central visual field specified for biological motion perception. The current study explores the processes of biological motion perception and figure–ground segmentation in the central and peripheral visual field, expanding the understanding of perceptual organization across different eccentricities. The method involved three different tasks of visual grouping: (1) a static visual grouping task, (2) a dynamic visual grouping task, and (3) a biological motion detection task. The stimuli in (1) and (2) were generated from 12–13 dots grouped by proximity and common fate, and, in (3), light dots representing human motion. All stimuli were embedded in static or dynamics visual noise and the threshold value for the number of noise dots in which the elements could still be grouped by proximity and/or common fate was determined. The results demonstrate that biological motion can be differentiated from the scrambled set of moving dots in a more intensive visual noise than static and dynamic visual grouping tasks. Furthermore, in all three visual tasks (static and dynamic grouping, and biological motion detection) the performance was significantly worse in the periphery than in the central visual field, and object magnification could not compensate for the reduced performance in any of the three grouping tasks. The preliminary results of nine participants indicate that (a) human motion perception involves specific perceptual processes, providing the high-accuracy perception of the human body and (b) the processes of figure–ground segmentation are governed by the bottom-up processes and the best performance can be achieved only when the object is demonstrated in the central visual field.
- Published
- 2023
- Full Text
- View/download PDF
50. A Conceptual Approach to Learning Chemistry in Professional Secondary School in Latvia
- Author
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Priede, Daina and Krumina, Aira
- Abstract
After the year 1991, great structural reforms were launched in Latvia at all levels of education, including secondary education. Still, there are many reforms that must be implemented in secondary professional education. The objective of our research was to develop a contemporary didactic coverage for teaching chemistry in professional secondary education. New teaching/learning material in chemistry for professional secondary schools was elaborated as a result of this study. It consists of the following units: basic (invariable) theory a unit based on the curriculum of the "State Educational Standard" in chemistry. Variable theory, a unit, includes various and specific information about environmental chemical processes that are vital to ensure definite students' professional competences in future. A unit that develops students' self-dependent skills and activity this unit includes exercises of different difficulty based on the implementation of the didactic approach: knowledge understanding application. A unit that promotes students' experimental skills and activity this unit contains descriptions of environmentally "friendly" laboratory exercises. (Contains 2 figures and 1 table.)
- Published
- 2012
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