Точно решаемая модель в теории параметрического резонанса

Проблематика. Побудова точно розв’язуваної моделі параметричного резонансу з розв’язками в аналітичному вигляді. Вивчення основних властивостей параметричного резонансу в точно розв’язуваній моделі, коли періодичним потенціалом рівняння Хілла є потенціал Ламе. Мета дослідження. Застосування одновимірних скінченнозонних потенціалів Ламе для розрахунку параметрів параметричного резонансу. Методика реалізації. Для реалізації поставленої мети використовувалися методи теоретичної фізики, методи теорії еліптичних функцій для застосування скінченнозонних потенціалів; наближення слабкого і сильного зв’язку для дослідження граничних випадків методу скінченнозонного потенціалу. Результати дослідження. Проведено дослідження точно розв’язуваної моделі, коли періодичним потенціалом рівняння Хілла є скінченнозонний потенціал Ламе, пропорційний еліптичній функції Вейєрштрасса. Таким потенціалам відповідає спектр, що складається зі скінченного числа зон. Розвинуто зонний підхід для аналізу явища параметричного резонансу. В моделі потенціалу Ламе для зовнішньої сили, прикладеної до осцилятора, розраховано інкременти наростання коливань. Показано, що інкремент наростання досягає максимуму посередині зони (умова параметричного резонансу) і що похідні від інкремента наростання за власною частотою перетворюються в нескінченність на границях зони. Цьому результату відповідає перетворення в нескінченність похідних від квазічастоти за власною частотою у випадку коливань параметричного осцилятора з обмеженою амплітудою. Висновки. Модель потенціалу Ламе дає можливість досліджувати залежність інкремента наростання від інтенсивності зовнішнього впливу, якщо за допомогою періодів потенціалу промоделювати наближення слабкого і сильного впливу.Background. Construction of the exactly solvable model of the parametric resonance with the solutions in analytical form. The study of the parametric resonance basic properties in the exactly solvable model in case that the periodic potential of the Hill equation is the Lame potential. Objective. Using of the Lame one-dimensional finite-zone potentials for calculating of the parametric resonance parameters. Methods. To achieve this purpose the methods of theoretical physics, the methods of the elliptic functions theory for use of the finite-zone potentials, the weak- and strong-binding approximations for studying of the limit cases of finite-zone potential are used. Results. The study of exactly solvable models in case that the periodic potential of the Hill equation is the Lame potential proportional to the elliptic Weierstrass function is performed. These potentials correspond to a spectrum that consists of a finite number of zones. Zone approach for the analysis of the effect of parametric resonance is developed. The increments of growth of oscillations in the Lame potential model for external force applied to the oscillator are calculated. It is shown that the increment of growth reaches a maximum in the middle of zone (parametric resonance condition) and that derivatives of the increment of growth with respect to the natural frequency tend to infinity on the zone boundaries. This result corresponds to a conversion to infinity of derivatives of quasifrequency with respect to the natural frequency in case of the parametric oscillator fluctuations with constrained amplitude. Conclusions. The Lame potential model gives an opportunity to explore the dependence of the increment of growth on the intensity of external influence in case that the weak- and strong-binding approximations are modulated by the potential periods.Проблематика. Построение точно решаемой модели параметрического резонанса с решениями в аналитическом виде. Изучение основных свойств параметрического резонанса в точно решаемой модели, когда периодическим потенциалом уравнения Хилла является потенциал Ламе. Цель исследования. Применение одномерных конечнозонных потенциалов Ламе для расчета параметров параметрического резонанса. Методика реализации. Для реализации поставленной задачи используются методы теоретической физики, методы теории эллиптических функций для применения конечнозонных потенциалов; приближения слабой и сильной связи для исследования предельных случаев метода конечнозонного потенциала. Результаты исследования. Проведено исследование точно решаемой модели, когда периодическим потенциалом уравнения Хилла является конечнозонный потенциал Ламе, пропорциональный эллиптической функции Вейерштрасса. Таким потенциалам соответствует спектр, состоящий из конечного числа зон. Развит зонный подход для анализа явления параметрического резонанса. В модели потенциала Ламе для внешней силы, приложенной к осциллятору, рассчитаны инкременты нарастания колебаний. Показано, что инкремент нарастания достигает максимума посредине зоны (условие параметрического резонанса) и производные от инкремента нарастания по собственной частоте превращаются в бесконечность на границах зоны. Этому результату соответствует преобразование в бесконечность производных от квазичастоты по собственной частоте в случае колебаний параметрического осциллятора с ограниченной амплитудой. Выводы. Модель потенциала Ламе дает возможность исследовать зависимость инкремента нарастания от интенсивности внешнего воздействия, если с помощью периодов потенциала промоделировать приближения слабого и сильного воздействия

Stochastic Resonance of Ensemble Neurons for Transient Spike Trains: A Wavelet Analysis

By using the wavelet transformation (WT), we have analyzed the response of an ensemble of $N$ (=1, 10, 100 and 500) Hodgkin-Huxley (HH) neurons to {\it transient} $M$-pulse spike trains ($M=1-3$) with independent Gaussian noises. The cross-correlation between the input and output signals is expressed in terms of the WT expansion coefficients. The signal-to-noise ratio (SNR) is evaluated by using the {\it denoising} method within the WT, by which the noise contribution is extracted from output signals. Although the response of a single (N=1) neuron to sub-threshold transient signals with noises is quite unreliable, the transmission fidelity assessed by the cross-correlation and SNR is shown to be much improved by increasing the value of $N$: a population of neurons play an indispensable role in the stochastic resonance (SR) for transient spike inputs. It is also shown that in a large-scale ensemble, the transmission fidelity for supra-threshold transient spikes is not significantly degraded by a weak noise which is responsible to SR for sub-threshold inputs.Comment: 20 pages, 4 figure

Key features of palliative care service delivery to Indigenous peoples in Australia, New Zealand, Canada and the United States: A comprehensive review

Background: Indigenous peoples in developed countries have reduced life expectancies, particularly from chronic diseases. The lack of access to and take up of palliative care services of Indigenous peoples is an ongoing concern. Objectives: To examine and learn from published studies on provision of culturally safe palliative care service delivery to Indigenous people in Australia, New Zealand (NZ), Canada and the United States of America (USA); and to compare Indigenous peoples’ preferences, needs, opportunities and barriers to palliative care. Methods: A comprehensive search of multiple databases was undertaken. Articles were included if they were published in English from 2000 onwards and related to palliative care service delivery for Indigenous populations; papers could use quantitative or qualitative approaches. Common themes were identified using thematic synthesis. Studies were evaluated using Daly’s hierarchy of evidence-for-practice in qualitative research. Results: Of 522 articles screened, 39 were eligible for inclusion. Despite diversity in Indigenous peoples’ experiences across countries, some commonalities were noted in the preferences for palliative care of Indigenous people: to die close to or at home; involvement of family; and the integration of cultural practices. Barriers identified included inaccessibility, affordability, lack of awareness of services, perceptions of palliative care, and inappropriate services. Identified models attempted to address these gaps by adopting the following strategies: community engagement and ownership; flexibility in approach; continuing education and training; a whole-of-service approach; and local partnerships among multiple agencies. Better engagement with Indigenous clients, an increase in number of palliative care patients, improved outcomes, and understanding about palliative care by patients and their families were identified as positive achievements. Conclusions: The results provide a comprehensive overview of identified effective practices with regards to palliative care delivered to Indigenous populations to guide future program developments in this field. Further research is required to explore the palliative care needs and experiences of Indigenous people living in urban areas

Multi-ethnic GWAS and meta-analysis of sleep quality identify MPP6 as a novel gene that functions in sleep center neurons

Poor sleep quality can have harmful health consequences. Although many aspects of sleep are heritable, the understandings of genetic factors involved in its physiology remain limited. Here, we performed a genome-wide association study (GWAS) using the Pittsburgh Sleep Quality Index (PSQI) in a multi-ethnic discovery cohort (n = 2868) and found two novel genome-wide loci on chromosomes 2 and 7 associated with global sleep quality. A meta-analysis in 12 independent cohorts (100 000 individuals) replicated the association on chromosome 7 between NPY and MPP6. While NPY is an important sleep gene, we tested for an independent functional role of MPP6. Expression data showed an association of this locus with both NPY and MPP6 mRNA levels in brain tissues. Moreover, knockdown of an orthologue of MPP6 in Drosophila melanogaster sleep center neurons resulted in decreased sleep duration. With convergent evidence, we describe a new locus impacting human variability in sleep quality through known NPY and novel MPP6 sleep genes.Peer reviewe

Genome-Wide Association Study Identifies Chromosome 10q24.32 Variants Associated with Arsenic Metabolism and Toxicity Phenotypes in Bangladesh

Arsenic contamination of drinking water is a major public health issue in many countries, increasing risk for a wide array of diseases, including cancer. There is inter-individual variation in arsenic metabolism efficiency and susceptibility to arsenic toxicity; however, the basis of this variation is not well understood. Here, we have performed the first genome-wide association study (GWAS) of arsenic-related metabolism and toxicity phenotypes to improve our understanding of the mechanisms by which arsenic affects health. Using data on urinary arsenic metabolite concentrations and approximately 300,000 genome-wide single nucleotide polymorphisms (SNPs) for 1,313 arsenic-exposed Bangladeshi individuals, we identified genome-wide significant association signals (P<5×10−8) for percentages of both monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) near the AS3MT gene (arsenite methyltransferase; 10q24.32), with five genetic variants showing independent associations. In a follow-up analysis of 1,085 individuals with arsenic-induced premalignant skin lesions (the classical sign of arsenic toxicity) and 1,794 controls, we show that one of these five variants (rs9527) is also associated with skin lesion risk (P = 0.0005). Using a subset of individuals with prospectively measured arsenic (n = 769), we show that rs9527 interacts with arsenic to influence incident skin lesion risk (P = 0.01). Expression quantitative trait locus (eQTL) analyses of genome-wide expression data from 950 individual's lymphocyte RNA suggest that several of our lead SNPs represent cis-eQTLs for AS3MT (P = 10−12) and neighboring gene C10orf32 (P = 10−44), which are involved in C10orf32-AS3MT read-through transcription. This is the largest and most comprehensive genomic investigation of arsenic metabolism and toxicity to date, the only GWAS of any arsenic-related trait, and the first study to implicate 10q24.32 variants in both arsenic metabolism and arsenical skin lesion risk. The observed patterns of associations suggest that MMA% and DMA% have distinct genetic determinants and support the hypothesis that DMA is the less toxic of these two methylated arsenic species. These results have potential translational implications for the prevention and treatment of arsenic-associated toxicities worldwide

New Mediterranean marine biodiversity records (December, 2013)

Based on recent biodiversity studies carried out in different parts of the Mediterranean, the following 19 species are included as new records on the floral or faunal lists of the relevant ecosystems: the green algae Penicillus capitatus (Maltese waters); the nemertean Am- phiporus allucens (Iberian Peninsula, Spain); the salp Salpa maxima (Syria); the opistobranchs Felimida britoi and Berghia coerulescens (Aegean Sea, Greece); the dusky shark Carcharhinus obscurus (central-west Mediterranean and Ionian Sea, Italy); Randall’s threadfin bream Nemipterus randalli, the broadbanded cardinalfish Apogon fasciatus and the goby Gobius kolombatovici (Aegean Sea, Turkey); the reticulated leatherjack Stephanolepis diaspros and the halacarid Agaue chevreuxi (Sea of Marmara, Turkey); the slimy liagora Ganon- ema farinosum, the yellowstripe barracuda Sphyraena chrysotaenia, the rayed pearl oyster Pinctada imbricata radiata and the Persian conch Conomurex persicus (south-eastern Kriti, Greece); the blenny Microlipophrys dalmatinus and the bastard grunt Pomadasys incisus (Ionian Sea, Italy); the brown shrimp Farfantepenaeus aztecus (north-eastern Levant, Turkey); the blue-crab Callinectes sapidus (Corfu, Ionian Sea, Greece). In addition, the findings of the following rare species improve currently available biogeographical knowledge: the oceanic pufferfish Lagocephalus lagocephalus (Malta); the yellow sea chub Kyphosus incisor (Almuñécar coast of Spain); the basking shark Cetorhinus maximus and the shortfin mako Isurus oxyrinchus (north-eastern Levant, Turkey).peer-reviewe

Mice Doubly-Deficient in Lysosomal Hexosaminidase A and Neuraminidase 4 Show Epileptic Crises and Rapid Neuronal Loss

Tay-Sachs disease is a severe lysosomal disorder caused by mutations in the HexA gene coding for the α-subunit of lysosomal β-hexosaminidase A, which converts GM2 to GM3 ganglioside. Hexa−/− mice, depleted of β-hexosaminidase A, remain asymptomatic to 1 year of age, because they catabolise GM2 ganglioside via a lysosomal sialidase into glycolipid GA2, which is further processed by β-hexosaminidase B to lactosyl-ceramide, thereby bypassing the β-hexosaminidase A defect. Since this bypass is not effective in humans, infantile Tay-Sachs disease is fatal in the first years of life. Previously, we identified a novel ganglioside metabolizing sialidase, Neu4, abundantly expressed in mouse brain neurons. Now we demonstrate that mice with targeted disruption of both Neu4 and Hexa genes (Neu4−/−;Hexa−/−) show epileptic seizures with 40% penetrance correlating with polyspike discharges on the cortical electrodes of the electroencephalogram. Single knockout Hexa−/− or Neu4−/− siblings do not show such symptoms. Further, double-knockout but not single-knockout mice have multiple degenerating neurons in the cortex and hippocampus and multiple layers of cortical neurons accumulating GM2 ganglioside. Together, our data suggest that the Neu4 block exacerbates the disease in Hexa−/− mice, indicating that Neu4 is a modifier gene in the mouse model of Tay-Sachs disease, reducing the disease severity through the metabolic bypass. However, while disease severity in the double mutant is increased, it is not profound suggesting that Neu4 is not the only sialidase contributing to the metabolic bypass in Hexa−/− mice

Bacterial Colonization of Low‐Wettable Surfaces is Driven by Culture Conditions and Topography

Effect of surface low‐wettability on bacterial colonization has become a prominent subject for the development of antibacterial coatings. However, bacteria's fate on such surfaces immersed in liquid as well as causal factors is poorly understood. This question is addressed by using a range of coatings with increasing hydrophobicity, to superhydrophobic, obtained by an atmospheric plasma polymer method allowing series production. Chemistry, wettability, and topography are thoroughly described, as well as bacterial colonization by in situ live imaging up to 24 h culture time in different liquid media. In the extreme case of superhydrophobic coating, substrates are significantly less colonized in biomolecule‐poor liquids and for short‐term culture only. Complex statistical analysis demonstrates that bacterial colonization on these low‐wettable substrates is predominantly controlled by the culture conditions and only secondary by topographic coating's properties (variation in surface structuration with almost constant mean height). Wettability is less responsible for bacterial colonization reduction in these conditions, but allows the coatings to preserve colonization‐prevention properties in nutritive media when topography is masked by fouling. Even after long‐term culture in rich medium, many large places of the superhydrophobic coating are completely free of bacteria in relation to their capacity to preserve air trapping

Investigating neuromagnetic brain responses against chromatic flickering stimuli by wavelet entropies

BACKGROUND: Photosensitive epilepsy is a type of reflexive epilepsy triggered by various visual stimuli including colourful ones. Despite the ubiquitous presence of colorful displays, brain responses against different colour combinations are not properly studied. METHODOLOGY/PRINCIPAL FINDINGS: Here, we studied the photosensitivity of the human brain against three types of chromatic flickering stimuli by recording neuromagnetic brain responses (magnetoencephalogram, MEG) from nine adult controls, an unmedicated patient, a medicated patient, and two controls age-matched with patients. Dynamical complexities of MEG signals were investigated by a family of wavelet entropies. Wavelet entropy is a newly proposed measure to characterize large scale brain responses, which quantifies the degree of order/disorder associated with a multi-frequency signal response. In particular, we found that as compared to the unmedicated patient, controls showed significantly larger wavelet entropy values. We also found that Renyi entropy is the most powerful feature for the participant classification. Finally, we also demonstrated the effect of combinational chromatic sensitivity on the underlying order/disorder in MEG signals. CONCLUSIONS/SIGNIFICANCE: Our results suggest that when perturbed by potentially epileptic-triggering stimulus, healthy human brain manages to maintain a non-deterministic, possibly nonlinear state, with high degree of disorder, but an epileptic brain represents a highly ordered state which making it prone to hyper-excitation. Further, certain colour combination was found to be more threatening than other combinations