Concentration Dependence of the Flory Chi Parameter within Two-State Models

The Flory chi parameter is typically assumed to depend only on the temperature, T. Experimental results often require the replacement of this chi(T) by chieff, that depends also on the monomer volume fraction, phi, chieff(phi,T). Such chieff(phi,T) can arise from two state-models, proposed for polyetheleneoxide (PEO) and other neutral water-soluble polymers. The predicted phi dependence of chibar=chieff-(1-phi)\partial \chieff/\partial phi, obtainable from colligative properties, differs qualitatively between the various models: (i) The model of Karlstrom (J. Phys. Chem. 1985, 89, 4962) yields \partial chibar/\partial phi > 0 while the model of Matsuyama and Tanaka (Phys. Rev. Lett. 1990, 65, 341) and of Bekiranov et al (Phys. Rev. E 1997, 55, 577) allows for \partial chibar/\partial phi <0 (ii) chibar(phi) as calculated from the Karlstrom model, utilizing the parameters used to fit the phase diagram of PEO, agrees semiquantitatively with the experimental values. On the other hand, chibar(phi) similarly calculated from the model of Bekiranov et al. differs qualitatively from the measured results. Altogether, chibar(phi) provides useful measure for the performance of a model.Comment: 8 pages, 5 figures, Macromolecules, in pres

Signatures of a Concentration Dependent Flory chi Parameter: Swelling and Collapse of Coils and Brushes

The quality of solvents of polymers is often described in terms of the Flory chi parameter typically assumed to depend only on the temperature, T. In certain polymer-solvent systems fitting the experimental data enforces the replacement of chi(T) by a concentration dependent chieff. In turn, this modifies the swelling and collapse behavior. These effects are studied, in the framework of a mean-field theory, for isolated coils and for planar brushes. The phi dependence of chieff gives rise to three main consequences: (i) Shift in the cross-over between Gaussian and self-avoidance regimes; (ii) A possibility of first-order collapse transition for isolated flexible coils; (iii) The possibility of a first-order phase transition leading to a vertical phase separation within the brush. The discussion relates these effects directly to thermodynamic measurements and does not involve a specific microscopic model. The implementation for the case of Poly(N-isopropylacrylamide) (PNIPAM) is discussed.Comment: 12 pages, 9 figure

Double-spiral magnetic structure of the Fe/Cr multilayer revealed by nuclear resonance scattering

We have studied the magnetization depth profiles in a [57Fe(dFe)/Cr(dCr)]x30 multilayer with ultrathin Fe layers and nominal thickness of the chromium spacers dCr 2.0 nm using nuclear resonance scattering of synchrotron radiation. The presence of a broad pure-magnetic half-order (1/2) Bragg reflection has been detected at zero external field. The joint fit of the reflectivity curves and Mossbauer spectra of reflectivity measured near the critical angle and at the "magnetic" peak reveals that the magnetic structure of the multilayer is formed by two spirals, one in the odd and another one in the even iron layers, with the opposite signs of rotation. The double-spiral structure starts from the surface with the almost antiferromagnetic alignment of the adjacent Fe layers. The rotation of the two spirals leads to nearly ferromagnetic alignment of the two magnetic subsystems at some depth, where the sudden turn of the magnetic vectors by ~180 deg (spin-flop) appears, and both spirals start to rotate in opposite directions. The observation of this unusual double-spiral magnetic structure suggests that the unique properties of giant magneto-resistance devices can be further tailored using ultrathin magnetic layers.Comment: 9 pages, 3 figure

Degradation versus self-assembly of block copolymer micelles

The stability of micelles self-assembled from block copolymers can be altered by the degradation of the blocks. Slow degradation shifts the equilibrium size distribution of block copolymer micelles and change their properties. Quasi-equilibrium scaling theory shows that the degradation of hydrophobic blocks in the core of micelles destabilize the micelles reducing their size, while the degradation of hydrophilic blocks forming coronas of micelles favors larger micelles and may, at certain conditions, induce the formation of micelles from individual chains.Comment: Published in Langmuir http://pubs.acs.org/doi/pdf/10.1021/la204625

The forecast of occurrence of risk of time disability on the basis of a complex estimation of a state of health, working conditions and qualities of a life of workers of shipbuilding

The aim of the work was to develop a way of the forecast the risk of occurrence in time disability at the workers occupied with shipbuilding. 577 persons, occupied in shipbuilding and ship repair, have taken part in research. Objective data on disease (were estimated according to disease with time disability, morbidity rate and medical surveys), harmful production factors, levels functional intensity of the basic systems of an organism, and also subjective: working conditions and a life, quality of a life. Results: With the help of the factorial analysis it was possible to lower dimension of a correlation matrix with 142 to 34 variables. The close interrelation of the factors describing an estimation of a degree of satisfaction of relations in collective, material compensation of work and pleasure from carried out work with a self-estimation of conformity of work to health, objective parameters of a state of health has been found out. It is established, that up to 35 % of disease it is possible to prevent the competent organization of work within the precincts of the enterprise (normalization of relations in collective, material compensation of work and formation of installations on importance and necessity of carried out work). The most part (53,5 %) at the same time is enough the factors connected to health, poorly gives in to updating as is caused or features of technological process, or features of a way of life working. The problem of the forecast of risk of time disability at the workers occupied in shipbuilding branch has been solved with the help of the consecutive analysis on method of A. Wald in updating E.V Gubler (1990). The received solving rule took into account the characteristics including data on a way of life, character of labour activity, the experience, age, a field, a functional pressure of cardiovascular system. The mistake of the forecast has made less than 10 %. Thus, use of the received mathematical model allows not only it is correct to predict occurrence of time disability at the workers borrowed in ship-building branch, but to define things in common between a state of health, working conditions and quality of a life

Application of a diagnostic algorithm for differential diagnosis in a patient with recurrent abdominal pain

Introduction Among the diseases of urgent pathology the leading place belongs to acute pancreatitis, which is second only to acute appendicitis and acute cholecystitis. Moreover, a significant share is occupied by mild forms, which account for 85%. In the Clinical Recommendations for Acute pancreatitis in the section “Prevention and dispensary monitoring”, the authors recommend regular dispensary monitoring by a gastroenterologist and a surgeon. However, this nosology according to the Order of the Ministry of Health of the Russian Federation from 03.15.2022 No 168N is not included in the dispensary observation. In this regard, patients remain without proper attention of doctors when they are discharged from hospitals, or when they refuse hospitalization after examination in the emergency room. The aim of the work – is to present the result of applying the diagnostic algorithm of differential diagnosis of diseases and detection of gastrointestinal tract pathology on the clinical example of a patient with recurrent abdominal pain syndrome. Materials and methods The analysis of medical records of a 59-year-old patient who repeatedly applied to the network of polyclinics and hospitals providing emergency specialized medical care for recurrent abdominal syndrome was carried out. Results and discussion In this clinical observation of recurrent abdominal syndrome in a patient, the biliary mask of acute pancreatitis was revealed. In outpatient conditions using the developed diagnostic algorithm, choledocholithiasis, juxtapapillary diverticulum of the duodenum and hernia of the esophageal aperture of the diaphragm were detected. The diagnosis made it possible to perform the treatment competently and lead to the patient's recovery. Thanks to the dispensary observation and additional methods of investigation according to the developed algorithm, the following were detected: juxtapapillary diverticulum of the duodenum, which may not be visualized at video esophagogastroduodenoscopy with direct optics, as well as ductal stones, which are not always visualized at transabdominal ultrasound and are detected at endoscopic retrograde cholangiopancreatography or endoscopic ultrasonography. Difficulties may arise in the diagnosis of gastrointestinal diseases due to the variability of the clinical course and polymorphism of symptoms in this category of patients. Such a course of diseases causes difficulties at the stage of patients' admission to the emergency room of clinics, can lead to diagnostic errors that lead to incorrect treatment tactics. Conclusion The application of an algorithm based on the assessment of clinical criteria in conjunction with instrumental imaging methods and laboratory tests allowed to optimize the diagnostic process and facilitated the choice of optimal therapy and surgical tactics for the treatment of the patient with recurrent abdominal pain syndrome.Введение. Среди заболеваний ургентной патологии ведущее место принадлежит острому панкреатиту, который уступает лишь острому аппендициту и острому холециститу. Причем значительную долю занимают легкие формы, которые составляют 85 %. В Клинических рекомендациях по острому панкреатиту в разделе «Профилактика и диспансерное наблюдение» рекомендовано регулярное диспансерное наблюдение у врача-гастроэнтеролога и врача-хирурга. Однако данная нозология согласно Приказу Минздрава РФ от 15.03.2022 № 168Н в диспансерное наблюдение не включена. В связи с этим пациенты остаются без должного внимания врачей при выписке из стационаров либо при отказе от госпитализации после обследования в условиях приемного отделения. Цель работы – на клиническом примере пациентки с рецидивирующим абдоминальным болевым синдромом представить результат применения диагностического алгоритма дифференциальной диагностики заболеваний и выявления патологии желудочно-кишечного тракта. Материалы и методы. Проведен анализ медицинской документации пациентки 59 лет, неоднократно обращавшейся в сеть поликлиник и стационаров, оказывающих экстренную специализированную медицинскую помощь при рецидивирующем абдоминальном синдроме. Результаты и обсуждение. В данном клиническом наблюдении рецидивирующего абдоминального синдрома у пациентки была выявлена билиарная маска острого панкреатита. В амбулаторных условиях с помощью разработанного диагностического алгоритма выявлены: холедохолитиаз, юкстапапиллярный дивертикул двенадцатиперстной кишки (ДПК) и грыжа пищеводного отверстия диафрагмы. Поставленный диагноз позволил грамотно выполнить лечение и привести к выздоровлению пациентки. Благодаря диспансерному наблюдению и дополнительным методам исследования согласно разработанному алгоритму выявлены: юкстапапиллярный дивертикул ДПК, который может не визуализироваться при видеоэзофагогастродуоденоскопии с прямой оптикой, а также протоковые камни, которые не всегда визуализируются при трансабдоминальном ультразвуковом исследовании и выявляются при эндоскопической ретроградной холангиопанкреатографии либо эндоскопической ультрасонографии. В диагностике желудочно-кишечных заболеваний могут возникать трудности, связанные с вариабельностью клинического течения и полиморфизмом симптоматики у пациентов. Такое течение заболеваний обуславливает сложности на этапе поступления пациентов в приемное отделение клиник, может вызывать диагностические ошибки, которые приводят к неправильной тактике лечения. Заключение. Применение алгоритма, основанного на оценке клинических критериев, в совокупности с инструментальными методами визуализации и лабораторными тестами позволило оптимизировать процесс диагностики и способствовало выбору оптимальной терапии и хирургической тактики лечения больной с рецидивирующим абдоминальным болевым синдромом

Biomolecule surface patterning may enhance membrane association

Under dehydration conditions, amphipathic Late Embryogenesis Abundant (LEA) proteins fold spontaneously from a random conformation into alpha-helical structures and this transition is promoted by the presence of membranes. To gain insight into the thermodynamics of membrane association we model the resulting alpha-helical structures as infinite rigid cylinders patterned with hydrophobic and hydrophilic stripes oriented parallel to their axis. Statistical thermodynamic calculations using Single Chain Mean Field (SCMF) theory show that the relative thickness of the stripes controls the free energy of interaction of the alpha-helices with a phospholipid bilayer, as does the bilayer structure and the depth of the equilibrium penetration of the cylinders into the bilayer. The results may suggest the optimal thickness of the stripes to mimic the association of such protein with membranes.Comment: Published in ACS Nano http://pubs.acs.org/doi/pdf/10.1021/nn204736

ЭКСТРАКЦИОННО-ХРОМАТОГРАФИЧЕСКОЕ ОПРЕДЕЛЕНИЕ НЕПТУНИЯ И ПЛУТОНИЯ В РАФИНАТНЫХ РАСТВОРАХ ПЕРЕРАБОТКИ ОТРАБОТАННОГО ЯДЕРНОГО ТОПЛИВА С ИСПОЛЬЗОВАНИЕМ СОРБЕНТА, ИМПРЕГНИРОВАННОГО СМЕСЬЮ ФОСФОРИЛПОДАНДА КИСЛОТНОГО ТИПА И НИТРАТА МЕТИЛТРИОКТИЛАММОНИЯ

An extraction chromatographic separation of Np(IV) and Pu(IV) from the raffinate reprocessing solutions of spent nuclear fuel using polymer sorbent impregnated with the mixture of acid type phosphorylpodand 1,5-bis[2-(oxyethoxyphosphinyl)-4-(ethyl)phenoxy]-3-oxapentan and quaternary ammonium base methyltrioctylammonium nitrate was performed. The effect of nitric acid and ammonium oxalate concentrations on the sorption of neptunium, plutonium, uranium, thorium and zirconium was studied. The techniques for measuring the content of  Np(IV) and Pu(IV) in the processed products of spent nuclear fuel using high performance liquid chromatography with spectrophotometric detection were proposed. Limits of detection for neptunium and plutonium were 5·10‑5 g·dm‑3 and 1.3·10-5 g·dm‑3  respectively. The duration of the analysis considering two parallel determinations does not exceed 40 min.Key words: еxtraction chromatography, phosphorylpodand, methyltrioctylammonium nitrate (МТОАN), carrier, plutonium, neptunium(Russian)DOI: http://dx.doi.org/10.15826/analitika.2013.17.3.007E.V. Chukhlantseva1, A.N. Usolkin1, V.E. Baulin 2,3, O.V. Kovalenko2, L.K. Neudachina4, A.Yu. Tsivadze3  1Federal State Unitary Enterprise "Production Association Mayak", Ozyorsk, Russia2Russian academy of sciences A.N. Frumkin Institute of Physical chemistry and Electrochemistry RAS, Moscow, Russia3Russian academy of sciences Institute of Physiologically Active Compounds RAS, Chernogolovka, Russia4Ural Federal University named after the first President of Russia B.N. Yeltsin, Ekaterinburg, RussiaОсуществлено экстракционно-хроматографическое выделение Np(IV), Pu(IV) из рафинатных растворов переработки отработанного ядерного топлива (ОЯТ) полимерным сорбентом, импрегнированным смесью фосфорилподанда кислотного типа - 1,5-бис[2-(оксиэтоксифосфинил)-4-(этил)фенокси]-3-оксапентаном, с четвертичным аммониевым основанием нитратом метилтриоктиламмония. Изучено влияние концентрации азотной кислоты, оксалата аммония на сорбцию нептуния, плутония, урана, тория и циркония. Предложены методики измерений содержания Np(IV) и Pu(IV) в продуктах переработки ОЯТ в варианте высокоэффективной жидкостной хроматографии со спектрофотометрическим детектированием. Пределы обнаружения нептуния и плутония составили 5·10-5 г/дм3 и 1.3·10-5 г/дм3 соответственно. Продолжительность анализа с учетом выполнения двух параллельных определений – не более 40 мин. Ключевые слова: экстракционная хроматография, фосфорилподанд, метилтриоктиламмоний нитрат (МТОАН), носитель, плутоний, нептунийDOI: http://dx.doi.org/10.15826/analitika.2013.17.3.007 Литература1. Саввин С. Б. Органические реагенты группы арсеназо III. М.: Атомиздат, 1971. 350 с.2. Браун Т., Герсини Г. Экстракционная хроматография. М.: Мир, 1978. 628 с.3. Баулин В.Е. Фосфорилсодержащие поданды. Синтез, свойства и применение. Автореф. … д-ра хим. наук. М., 2012. 49 с.4. Экстракционно-хроматографическое выделение и разделение тория, урана, нептуния и плутония сорбентами, импрегнированными фосфорилподандом кислотного типа и его смесями с нитратом метилтриоктиламмония / Е.В. Чухланцева и [др.] // Аналитика и контроль. 2013. Т. 17, № 2. С. 219-227. 5. Экстракционно-хроматографическое отделение плутония от других веществ с применением альфа-детектора для измерения его концентрации в растворах / В.К. Марков и [др.] // Радиохимия. 1976. Т. 18, № 5. С. 751-765.6. МИ 2335-2003. Внутренний контроль качества результатов количественного химического анализа. ФГУП «УНИИМ», 2003. 7. Дерффель К. Статистика в аналитической химии. М.: Мир, 1994. 268 с. 

Vortices in vibrated granular rods

We report the experimental observation of novel vortex patterns in vertically vibrated granular rods. Above a critical packing fraction, moving ordered domains of nearly vertical rods spontaneously form and coexist with horizontal rods. The domains of vertical rods coarsen in time to form large vortices. We investigate the conditions under which the vortices occur by varying the number of rods, vibration amplitude and frequency. The size of the vortices increases with the number of rods. We characterize the growth of the ordered domains by measuring the area fraction of the ordered regions as a function of time. A {\em void filling} model is presented to describe the nucleation and growth of the vertical domains. We track the ends of the vertical rods and obtain the velocity fields of the vortices. The rotation speed of the rods is observed to depend on the vibration velocity of the container and on the packing. To investigate the impact of the direction of driving on the observed phenomena, we performed experiments with the container vibrated horizontally. Although vertical domains form, vortices are not observed. We therefore argue that the motion is generated due to the interaction of the inclination of the rods with the bottom of a vertically vibrated container. We also perform simple experiments with a single row of rods in an annulus. These experiments directly demonstrate that the rod motion is generated when the rods are inclined from the vertical, and is always in the direction of the inclination.Comment: 6 pages, 10 figure, 2 movies at http://physics.clarku.edu/vortex uses revtex