(Nano)Granules-Involving Aggregation at a Passage to the Nanoscale as Viewed in Terms of a Diffusive Heisenberg Relation

We are looking at an aggregation of matter into granules. Diffusion plays a pivotal role here. When going down to the nanometer scale (the so-called nanoscale quantum-size effect limit), quantum mechanics, and the Heisenberg uncertainty relation, may take over the role of classical diffusion, as viewed typically in the mesoscopic/stochastic limit. A d-dimensional entropy-production aggregation of the granules-involving matter in the granule-size space is considered in terms of a (sub)diffusive realization. It turns out that when taking a full d-dimensional pathway of the aggregation toward the nanoscale, one is capable of disclosing a Heisenberg-type (diffusional) relation, setting up an upper uncertainty bound for the (sub)diffusive, very slow granules-including environment that, within the granule-size analogy invoked, matches the quantum limit of h/2πμ (μ-average mass of a granule; h-the Planck's constant) for the diffusion coefficient of the aggregation, first proposed by Fürth in 1933 and qualitatively foreseen by Schrödinger some years before, with both in the context of a diffusing particle. The classical quantum passage uncovered here, also termed insightfully as the quantum-size effect (as borrowed from the quantum dots' parlance), works properly for the three-dimensional (d = 3) case, making use of a substantial physical fact that the (nano)granules interact readily via their surfaces with the also-granular surroundings in which they are immersed. This natural observation is embodied in the basic averaging construction of the diffusion coefficient of the entropy-productive (nano)aggregation of interest.

Matter-Aggregating Low-Dimensional Nanostructures at the Edge of the Classical vs. Quantum Realm

This commentary tackles the subtle at-the-edge problem of passing locally by a mesoscopic matter-aggregating system from a classical stochastic to a quantum stochastic description. A d-dimensional entropy-productive aggregation of the matter is taken as the starting point. Then, a dimensional reduction towards a one-dimensional quantum-wire type matter-aggregation system is proposed, resulting in postponing surface-tension conditions for the effectively d = 1-dimensional quantum-wire type or nanorod-like cluster/polycrystal, which is qualitatively consistent with a physical-metallurgical (high-temperature) Louat's grain growth model. A certain recuperative interplay based on maneuvering between subtle temperature rises applied to the system under study while maintaining its quantum character (the so-called Nelson's quantum-stochastic procedure) within the limits of a vanishing Planck's constant, involved in the diffusivity measure of the aggregation, is discussed. Certain applications towards the formation of d = 1-dimensional semiconductors and other nanostructures (possibly using soft materials or (bio)polymeric materials such as nanofibers) are envisioned. As a special example, one may propose a nanotechnological process which is termed the Van der Waals heteroepitaxy. The process itself contains the main quantum vs. classical crossover due to the involvement of weak repulsion (quantum) vs. attraction (treated classically) interactions, which are represented by a Lennard-Jones-type potential.

Dissipative, Entropy Production Systems across Condensed Matter and Interdisciplinary Classical vs. Quantum Physics

This Special Issue collected ten papers addressing a range of topics in condensed matter and interdisciplinary classical vs [...].

Effect of Chitosan Deacetylation on Its Affinity to Type III Collagen: A Molecular Dynamics Study

The ability to form strong intermolecular interactions by linear glucosamine polysaccharides with collagen is strictly related to their nonlinear dynamic behavior and hence bio-lubricating features. Type III collagen plays a crucial role in tissue regeneration, and its presence in the articular cartilage affects its bio-technical features. In this study, the molecular dynamics methodology was applied to evaluate the effect of deacetylation degree on the chitosan affinity to type III collagen. The computational procedure employed docking and geometry optimizations of different chitosan structures characterized by randomly distributed deacetylated groups. The eight different degrees of deacetylation from 12.5% to 100% were taken into account. We found an increasing linear trend (R2 = 0.97) between deacetylation degree and the collagen-chitosan interaction energy. This can be explained by replacing weak hydrophobic contacts with more stable hydrogen bonds involving amino groups in N-deacetylated chitosan moieties. In this study, the properties of chitosan were compared with hyaluronic acid, which is a natural component of synovial fluid and cartilage. As we found, when the degree of deacetylation of chitosan was greater than 0.4, it exhibited a higher affinity for collagen than in the case of hyaluronic acid.

On (sub)mesoscopic scale peculiarities of diffusion driven growth in an active matter confined space, and related (bio)material realizations

Diffusion in a confined space becomes an extremely important problem with many versatile applications, ranging from biomedical to biotechnological, and involving functional and smart (bio)materials. In this study, we have shown that the well-known Mullins-Sekerka approach to morphological stability of the diffusional non-ideal sphere's growth, for which a confinement factor disappears, is a firm starting point for further questions. It has two modifications and/or extensions for which the confinement factor is involved readily and becomes (in)finite firstly for microscale (or micrometer scale) involving biomatter packing phenomena. They are also applicable for nanoscopic biomaterial arrangements for which very tightly packed material and active-matter including outcomes of subdiffusive proveniency would manifest, as it has already been observed for the protein crystal growth in pores and globule-to-coil crossover phenomena.

Correction: Physical crosslinking of hyaluronic acid in the presence of phospholipids in an aqueous nano-environment

Correction for 'Physical crosslinking of hyaluronic acid in the presence of phospholipids in an aqueous nano-environment' by Piotr Bełdowski et al., Soft Matter, 2018, DOI: 10.1039/c8sm01388h.

Physical crosslinking of hyaluronic acid in the presence of phospholipids in an aqueous nano-environment

Hyaluronic acid and phospholipids are two components in the synovial joint cavity that contribute to joint lubrication synergistically. Molecular dynamics simulations were performed and hydrogen bonds in hyaluronic acid were analyzed to identify specific sites that are responsible for its physical cross-linking. Two molecular masses of hyaluronic acid, 10 kDa and 160 kDa, were considered. We use molecular dynamics simulations and the small world network approach to investigate dynamic couplings using a distance map applied to oxygen atoms in a chain of hyaluronic acid in the presence of phospholipids and water. The distance characterizing the coupling can be defined in various ways to bring out the most evident differences between various scenarios of the polymer chain conformation We show herein a physical distance understood as H-bond length and classes of these distances which are defined in a coarse-grained picture of the molecule. Simulation results indicate that addition of phospholipids has little influence on hyaluronic acid crosslinking. However, longer chains and addition of lipids promote appreciably long lasting (resilient) networks that may be of importance in biological systems. Specific sites for hydrogen bonding of phospholipids to hyaluronic acid have also been identified.

Entropy Production Associated with Aggregation into Granules in a Subdiffusive Environment

We study the entropy production that is associated with the growing or shrinking of a small granule in, for instance, a colloidal suspension or in an aggregating polymer chain. A granule will fluctuate in size when the energy of binding is comparable to k B T , which is the "quantum" of Brownian energy. Especially for polymers, the conformational energy landscape is often rough and has been commonly modeled as being self-similar in its structure. The subdiffusion that emerges in such a high-dimensional, fractal environment leads to a Fokker-Planck Equation with a fractional time derivative. We set up such a so-called fractional Fokker-Planck Equation for the aggregation into granules. From that Fokker-Planck Equation, we derive an expression for the entropy production of a growing granule.

Capstan-like mechanism in hyaluronan-phospholipid systems

Functionality of articular cartilage results from complex interactions between its molecular components. Among many biomolecules, two are of prime importance for lubrication: hyaluronic acid (HA) and phospholipids (PL). The purpose of this study is to discuss a mechanism of interaction between these two components and how their synergies contribute to nanobiolubrication of articular cartilage. Preliminary molecular dynamics simulations have been performed to investigate these interactions by adopting a capstan-like mechanism of action. By applying a constant pulling force to both ends of a HA molecule, wrapped around a PL micelle, we viewed the rotation of the PL micelle. The simulations were performed upon two physicochemical constraints: force- and solvent-dependency. The results show the efficiency of rotation from intermolecular bond creation and annihilation. We found a direct relation between the available surface of the micelle and the magnitude of the force, which varies significantly through the unwinding. The movement of the attached molecules is characterized by a slide-to-roll relation, which is affected by the viscosity of the surrounding medium. As a consequence, two solvents were studied for specific force conditions and the molecular dynamics simulation exhibited double the slide-to-roll coefficient for the viscous solvent as compared to its low-viscosity limit.

Anomalous Behavior of Hyaluronan Crosslinking Due to the Presence of Excess Phospholipids in the Articular Cartilage System of Osteoarthritis

Lubrication of articular cartilage is a complex multiscale phenomenon in synovial joint organ systems. In these systems, synovial fluid properties result from synergistic interactions between a variety of molecular constituent. Two molecular classes in particular are of importance in understanding lubrication mechanisms: hyaluronic acid and phospholipids. The purpose of this study is to evaluate interactions between hyaluronic acid and phospholipids at various functionality levels during normal and pathological synovial fluid conditions. Molecular dynamic simulations of hyaluronic acid and phospholipids complexes were performed with the concentration of hyaluronic acid set at a constant value for two organizational forms, extended (normal) and coiled (pathologic). The results demonstrated that phospholipids affect the crosslinking mechanisms of hyaluronic acid significantly and the influence is higher during pathological conditions. During normal conditions, hyaluronic acid and phospholipid interactions seem to have no competing mechanism to that of the interaction between hyaluronic acid to hyaluronic acid. On the other hand, the structures formed under pathologic conditions were highly affected by phospholipid concentration.

Molecular Dynamic Analysis of Hyaluronic Acid and Phospholipid Interaction in Tribological Surgical Adjuvant Design for Osteoarthritis

Tribological surgical adjuvants constitute a therapeutic discipline made possible by surgical advances in the treatment of damaged articular cartilage beyond palliative care. The purpose of this study is to analyze interactions between hyaluronic acid and phospholipid molecules, and the formation of geometric forms, that play a role in the facilitated lubrication of synovial joint organ systems. The analysis includes an evaluation of the pathologic state to detail conditions that may be encountered by adjuvants during surgical convalescence. The synovial fluid changes in pH, hyaluronic acid polydispersity, and phospholipid concentration associated with osteoarthritis are presented as features that influence the lubricating properties of adjuvant candidates. Molecular dynamic simulation studies are presented, and the Rouse model is deployed, to rationalize low molecular weight hyaluronic acid behavior in an osteoarthritic environment of increased pH and phospholipid concentration. The results indicate that the hyaluronic acid radius of gyration time evolution is both pH- and phospholipid concentration-dependent. Specifically, dipalmitoylphosphatidylcholine induces hydrophobic interactions in the system, causing low molecular weight hyaluronic acid to shrink and at high concentration be absorbed into phospholipid vesicles. Low molecular weight hyaluronic acid appears to be insufficient for use as a tribological surgical adjuvant because an increased pH and phospholipid concentration induces decreased crosslinking that prevents the formation of supramolecular lubricating forms. Dipalmitoylphosphatidylcholine remains an adjuvant candidate for certain clinical situations. The need to reconcile osteoarthritic phenotypes is a prerequisite that should serve as a framework for future adjuvant design and subsequent tribological testing.

Dynamical Systems Theory in Quantitative Psychology and Cognitive Science: A Fair Discrimination between Deterministic and Statistical Counterparts is Required

This article addresses a set of observations framed in both deterministic as well as statistical formal guidelines. It operates within the framework of nonlinear dynamical systems theory (NDS). It is argued that statistical approaches can manifest themselves ambiguously, creating practical discrepancies in psychological and cognitive data analyses both quantitatively and qualitatively. This is sometimes termed in literature as 'questionable research practices.' This communication points to the demand for a deeper awareness of the data 'initial conditions, allowing to focus on pertinent evolution constraints in such systems.' It also considers whether the exponential (Malthus-type) or the algebraic (Pareto-type) statistical distribution ought to be effectively considered in practical interpretations. The role of repetitive specific behaviors by patients seeking treatment is examined within the NDS frame. The significance of these behaviors, involving a certain memory effect seems crucial in determining a patient's progression or regression. With this perspective, it is discussed how a sensitively applied hazardous or triggering factor can be helpful for well-controlled psychological strategic treatments; those attributable to obsessive-compulsive disorders or self-injurious behaviors are recalled in particular. There are both inherent criticality- and complexity-exploiting (reduced-variance based) relations between a therapist and a patient that can be intrinsically included in NDS theory.

The amphoteric effect on friction between the bovine cartilage/cartilage surfaces under slightly sheared hydration lubrication mode

The amphoteric effect on the friction between the bovine cartilage/cartilage contacts has been found to be highly sensitive to the pH of an aqueous solution. The cartilage surface was characterized using a combination of the pH, wettability, as well as the interfacial energy and friction coefficient testing methods to support lamellar-repulsive mechanism of hydration lubrication. It has been confirmed experimentally that phospholipidic multi-bilayers are essentially described as lamellar frictionless lubricants protecting the surface of the joints against wear. At the hydrophilicity limit, the low friction would then be due to (a) lamellar slippage of bilayers and (b) a short-range (nanometer-scale) repulsion between the interfaces of negatively charged (PO4(-)) cartilage surfaces, and in addition, contribution of the extracellular matrix (ECM) collagen fibers, hyaluronate, proteoglycans aggregates (PGs), glycoprotein termed lubricin and finally, lamellar PLs phases. In this paper we demonstrate experimentally that the pH sensitivity of cartilage to friction provides a novel concept in joint lubrication on charged surfaces.

[Anti-aging medicine, a science-based, essential medicine]

Anti-aging medicine is booming. It enters more and more in the programs of universities. Its hormone and nutritional tests and therapies rely on numerous scientific studies, including double-blind placebo-controlled randomized studies. Its methods are often innovative to obtain more information or benefits with greater safety. The fundamental purpose of anti-aging medicine is to optimize health and the quality of life, and through this, make the physical appearance more youthful. Well-chosen and well-dosed these treatments should not increase the risk of age-related diseases such as cancer and cardiovascular diseases, but on the contrary decrease it by the preventive aspect of the treatments. Opponents to anti-aging medicine fail in collecting valid scientific arguments. Their insistence on maintaining a society of elderly people looking and feeling as elderly people rather than actively participating in searching for ways to attenuate aging is harmful to all who follow them, to themselves in the first place.

[On Two Opposing (Bio)surfaces as Comprehended in Terms of an Extension of the Coulomb-Amontons Law of Friction, with Its Virtual Usefulness for Biotribology in Nanoscale]

An extension of the Coulomb-Amontons law is proposed in terms of an interaction-detail involving renormalization (simplified) n-th level scheme. The coefficient of friction is obtained in a general exponential (nonlinear) form, characteristic of virtually infinite (or, many body) level of the interaction map. Yet, its application for a hydration repulsion bilayered system, prone to facilitated lubrication, is taken as linearly confined, albeit with an inclusion of a decisive repelling force/pressure factor. Some perspectives toward related systems, fairly outside biotribological issues, have been also addressed.

Some conceptual thoughts toward nanoscale oriented friction in a model of articular cartilage

This work presents a conceptual framework as to how a deficit in the synovial-fluid content, exemplified by hyaluronan or any other amphiphilic species, is capable of decisively altering the complex lubrication and wear conditions observed clinically in articular cartilage. The effect is revealed in (non)stationary regimes if the cartilage is subjected to some normal periodic load, revealing over its exploitation time increasingly dissipative, in general entropy-addressing, characteristics. It can be hypothesized that a Grotthuss-type proton transport physiology-concerning mechanism in channel-like, phospholipid-water cartilage's articulating nanospaces will be responsible for the expression of the lubrication mode. The corresponding wear involving overall change is then manifested adequately in the stationary regime, and in a viable system-parametric correlation with its lubrication counterpart. Certain analytic formulae for the nanoscale oriented coefficient of friction, involving generically H-bonds breaking mechanism, and pointing to some local-viscosity context, have been proposed for fitting the experimental data and clinical observations involving proton management at articular cartilage surfaces.

The role of lamellate phospholipid bilayers in lubrication of joints

This study aims to determine the effect of progressive loss of the surface active phospholipids on the characteristics, and hence tribological function of articular cartilage. In accordance to Hill's hypothesis, 3-7 lipid bilayers at pH 7.4 operate as the solid lubricant in the cartilage-cartilage interface during physiological function. These bilayers are known to be depleted during cartilage degeneration. This study models this loss of phospholipid bilayers, studying experimentally both wet and dry cartilage surfaces, measuring surface wettability, and friction coefficient under a constant stress of 1.2 MPa. The results demonstrate that the friction coefficient increases gradually with loss of the phospholipid bilayers, and gains in value with decrease in wettability.

Controlling protein crystal growth rate by means of temperature

We have proposed a model to analyze the growth kinetics of lysozyme crystals/aggregates under non-isothermal conditions. The model was formulated through an analysis of the entropy production of the growth process which was obtained by taking into account the explicit dependence of the free energy on the temperature. We found that the growth process is coupled with temperature variations, resulting in a novel Soret-type effect. We identified the surface entropy of the crystal/aggregate as a decisive ingredient controlling the behavior of the average growth rate as a function of temperature. The behavior of the Gibbs free energy as a function of temperature is also analyzed. The agreement between theory and experiments is very good in the range of temperatures considered.

On the spherical prototype of a complex dissipative late-stage formation seen in terms of least action Vojta-Natanson principle

The spherical prototype of a crystalline and/or disorderly formation may help in understanding the final stages of many complex biomolecular arrangements. These stages are important for both naturally organized simple biosystems, such as protein (or, other amphiphilic) aggregates in vivo, as well as certain their artificial counterparts, mimicking either in vitro or in silico their structure-property principal relationship. For our particular one-seed based realization of a protein crystal/aggregate late-stage nucleus grown from nearby fluctuating environment, it turns out that the (osmotic-type) pressure could be, due to local inhomogeneities, and their dynamics shown up in the double layer tightly surrounding the growing object, still an appreciably detectable quantity. This is due to the fact that a special-type generalized thermodynamic (Vojta-Natanson) momentum, subjected to the nucleus' surface, is manifested interchangeably, whereas the total energy of the solution in the double layer could not be such within the stationary regime explored. It is plausible since the double layer width, related to the object's surface, contributes ultimately, while based on the so-defined momentum's changes, to the pressure within this narrow flickering zone, while leaving the total energy fairly unchanged. From the hydrodynamic point of view, the system behaves quite trivially, since the circumventing flow should rather be of laminar, thus not-with-matter supplying, character.

On the protein crystal formation as an interface-controlled process with prototype ion-channeling effect

A superdiffusive random-walk action in the depletion zone around a growing protein crystal is considered. It stands for a dynamic boundary condition of the growth process and competes steadily with a quasistatic, curvature-involving (thermodynamic) free boundary condition, both of them contributing to interpret the (mainly late-stage) growth process in terms of a prototype ion-channeling effect. An overall diffusion function contains quantitative signatures of both boundary conditions mentioned and indicates whether the new phase grows as an orderly phase or a converse scenario occurs. This situation can be treated in a quite versatile way both numerically and analytically, within a generalized Smoluchowski framework. This study can help in (1) elucidating some dynamic puzzles of a complex crystal formation vs biomolecular aggregation, also those concerning ion-channel formation, and (2) seeing how ion-channel-type dynamics of non-Markovian nature may set properly the pace of model (dis)ordered protein aggregation.

Thermokinetic approach of single particles and clusters involving anomalous diffusion under viscoelastic response

We present a thermokinetic description of anomalous diffusion of single particles and clusters in a viscoelastic medium in terms of a non-Markovian diffusion equation involving memory functions. The scaling behavior of these functions is analyzed by considering hydrodynamics and cluster-size space random walk arguments. We explain experimental results on diffusion of Brownian particles in the cytoskeleton, in cluster-cluster aggregation, and in a suspension of micelles.

Ruptured appendicitis among children as an indicator of access to care

OBJECTIVE

To determine factors associated with ruptured appendicitis among children, using administrative databases. Insurance-related differences in the risk of ruptured appendix among adults in California have previously been described (Braveman, Schaaf, Egerter, et al. 1994).

DATA SOURCES/STUDY SETTING

State of Maryland Medicaid claims data for children < or = 18 years of age from 1989 to 1993 and hospital discharge data for children < or = 19 years of age from 1989 to 1994 were analyzed.

STUDY DESIGN

Administrative data analysis pre- and post-implementation of a Medicaid managed care program called Maryland Access to Care.

DATA COLLECTION/EXTRACTION METHODS

Medicaid claims and hospital discharge ICD-9-CM codes were used to define hospitalization for ruptured and nonruptured appendicitis. Linear regression was used to model trends. Logistic regression was used to model the probability of ruptured appendicitis.

PRINCIPAL FINDINGS

Among the 374 Medicaid inpatient claims for appendicitis, 37 percent were for ruptured appendicitis. Among the 5,141 hospital discharges for appendicitis, 30 percent were for ruptured appendicitis. Using Medicaid claims data, the probability of ruptured appendicitis was inversely related to age (OR = 0.86, 95% CI 0.81-0.91), white race (OR = 0.35, 95% CI 0.17-0.71) and preventive care visits (OR = 0.19, 95% CI 0.05-0.77). Using hospital discharge data, age (OR = 0.91, 95% CI 0.90-0.93) and female gender (OR = 0.87, 95% CI 0.77-0.99) were significant covariates. Insurance-related covariates were not significant in multivariate models addressing the probability of ruptured appendicitis.

CONCLUSIONS

During a period of rapid managed care growth, insurance type was not associated with an increased risk of ruptured appendicitis among children in this geographic area. Age, female gender, and the number of preventive care visits are inversely related to the risk of ruptured appendix among children. The protective effect of preventive care visits suggests that a primary care relationship facilitates access to care, thus reducing delay in the management of appendicitis.

Echocardiographic assessment of right atrial thrombus related to the implanted port device in patient receiving chemotherapy for non-Hodgkin's lymphoma

The case of a potentially life-threatening complication related to the use of implanted port device in a 8 year old Non-Hodgkin's Lymphoma patient receiving chemotherapy is described. The device was inserted in early 1997 and used repeatedly for chemotherapy without any complications. In late 1997 during routine screening for cardiac left ventricular function before re-introduction of chemotherapy, an abnormal 1.43 x 1.53 cm mass, consistent with a non-mobile thrombus was found in the right atrium. The initial thrombolytic therapy with recombinant tissue plasmin activator (rt-PA) infused by a central venous catheter was combined with daily echocardiographic examination in order to assess both the timing and mode of thrombus resolution. After 8 days systemic fibrinolytic therapy was discontinued as major hemorrhage from venipuncture sites occurred and the clot dissolution was not obtained. Patient underwent right atriotomy utilizing cardiopulmonary bypass and subsequent surgical thrombus removal was successful. The study evaluated the contribution of two-dimensional echocardiography (2D) in the follow-up of vascuport and other central venous catheter (CVC) location and early diagnosis of related complications such as thrombi. The authors consider that pulmonary flow analyzed with Doppler echocardiography as a reliable, suitable and non-invasive method to evaluate increased pulmonary artery pressure in children with right atrial thrombi and probability of pulmonary microembolism or embolism. As the incidence of right atrial thrombi is highly associated with the catheter tip position in the right atrium, in contrast to their positioning in the superior vena cava or in its junction with the right atrium, the authors recommend that special attention and effort should be given to placing of the catheter tip in the superior vena cava or in its junction with the right atrium avoiding the right atrium during the implantation procedure. The surgical right atrium thrombus removal in patients with no clot dissolution despite systemic thrombolytic treatment underscores the importance of surgical therapy in treating this life-threatening complication of indwelling catheters.

[Cyst of lower mediastinum in a 14-year-old boy with tumor of mediastinum in the course of Hodgkin's disease]

Bilateral enlarged lymph nodes in supraclavian regions, bilateral large tumour of mediastinum and enlarged lymph nodes of hiluses of the lungs were detected in a boy with stage III of Hodgkin's disease. After chemotherapy (MVPP/B-DOPA) and radiotherapy partial remission was achieved. However abnormal mass in the lower mediastinum on the right side of the heart was still present. Results of USG and CT studies showed solid character of this mass. MRI revealed a mediastinal cyst at the place of this mass. The boy has been in the first remission for eight months.

[Right atrial thrombus complicating chemotherapy by central venous catheterization in a child with Hodgkin's disease]

The atrial catheter (subcutaneous port) was used in a 5 year old boy with Hodgkin's disease for the administration of antineoplastic agents and other drugs. Catheter was flushed daily or every 2 weeks with heparin solution (5 U/ml)). The complications including infection and occlusion were not observed in this patient during observation time. Routine echocardiography performed after eight months of usage of the catheter showed right atrial thrombus. Because of the failure of 14 days fibrinolytic therapy (Actylise) surgical thrombectomy was performed. Bacteriological culture of the surgical specimen was positive for Pseudomonas aeruginosa. The post-operative period passed without complications. Follow-up echocardiography findings were normal. The probable reason of thrombus formation could be damage of the right atrium by stream of drugs or balloting ending of the catheter.

Children's mental health: recommendations for research, practice and policy

A recent study documented a large increase in prescriptions of stimulants and antidepressants among preschoolers, and has prompted public and professional concern about the effects of mood-altering drugs on young children. In response, the White House announced a broad initiative on children's mental health, including more government money for research, new labels on drugs for pediatric use, educational materials for parents, and a fall White House conference. To place these events in their larger context, this Issue Brief summarizes the findings of the Children's Mental Health Alliance Project, which conducted a multidisciplinary consensus conference in November 1998 followed by a year-long dialogue with clinicians, researchers, and families.

Polymorphic phase transitions in systems evolving in a two-dimensional discrete space

Polymorphic phase transitions in systems evolving in a two-dimensional discrete space have been studied. The driving force of the transitions appears to be a difference between two main energetic contributions: one, related to the thermal activation of the process, and another, being of quantum nature. The former (high temperature limit) is naturally assigned to the expansion (melting) part of the transition, while the latter (low temperature limit) has much in common with the contraction (solidification) part. Between the two main physical states distinguished, there exists a certain state, corresponding to a discontinuity point (pole) in the morphological phase diagram, represented by the well-known Bose-Einstein (Planck) formula, in which the system blows up. This point is related to an expected situation in which the contour of the object under investigation stands for the Brownian or purely diffusional path, with the fractal dimension dw=2, and the situation can be interpreted as some emergence of an intermediate "tetratic" phase. This, in turn, recalls a certain analogy to the equilibrium (order-disorder) phase transition of Kosterlitz-Thouless type, characteristic of, e.g., rough vs rigid interfaces in a two-dimensional space, with some disappearance of interface correlation length at dw=2. Otherwise, the contours of the objects are equivalent to fractional Brownian paths either in superlinear or "turbulent" (dw<2; the expansion case), or sublinear, viz., anomalously slow (dw>2; the contraction case) regimes, respectively. It is hoped that the description offered will serve to reflect properly the main subtleties of the dynamics of the polymorphic transitions in complex "soft-matter" systems, like formation of lipid mesomorphs or diffusional patterns, with nonzero line tension effect.

Impact of a Medicaid primary care provider and preventive care on pediatric hospitalization

OBJECTIVE

This study evaluates the impact that a Medicaid managed care program had on avoidable hospitalization, a form of health care misuse that we hypothesize can be reduced by improved access to and quality of primary care in the context of a managed care program. Ambulatory care sensitive (ACS) hospitalizations, a previously defined categorization of hospitalization, as well as all pediatric hospitalizations were also studied.

INTERVENTION

The Maryland Access to Care (MAC) was a fee-for-service, gatekeeper, Medicaid managed care program with assigned primary medical providers and required Early Periodic Screening, Diagnosis, and Treatment (EPSDT) examinations. Medicaid managed care elements include: 1) assignment to primary medical provider (PMP) either by voluntary choice or mandatory enrollment of eligible Aid to Families With Dependent Children (AFDC), Medical Assistance (medical needy), and Supplemental Security Income; 2) a medical home accessible 24 hours a day, 7 days a week; 2) PMP must authorize emergency department (ED), inpatient, and specialty care but there were no disincentives to PMP for referral; 3) fee-for-services reimbursement (with a physician rate increase) for primary care, authorized specialist care, and hospitalization; and 4) an on-line eligibility verification system was available to all medical providers. Pre-enrollment as well as publicity allowed MAC to be phased in rapidly, resulting in 70% to 80% enrollment by the end of the first program year.

DESIGN

The design of this study is that of a pre- and postevaluation of the MAC program using Medicaid claims analysis of data 3 years pre-MAC and 2 years post-MAC. In multivariate analyses, this study also compares MAC-enrolled children to non-MAC-enrolled children (before and after MAC began) to estimate the impact of MAC enrollment while controlling for potential confounders.

SETTING

State of Maryland from 1989 to 1993.

PATIENTS

MAC-eligible children 18 years of age.

OUTCOME MEASURES

Claims data were used to define avoidable hospitalization (based on ambulatory care received before hospitalization), to define ACS hospitalizations (based on the International Classification of Diseases-Clinical Modification, Ninth Revision [ICD-9-CM] codes), and to summarize use of ambulatory and inpatient care. ACS hospitalizations have been defined as those conditions for which timely and effective primary care can help to reduce the risk of hospitalizations. These are based solely on ICD-9-CM discharge codes that were studied by Billings and Teicholz in 1990 and used by an Institute of Medicine report in 1993. Examples include hospital discharge diagnoses of asthma (ICD-9-CM = 493), gastroenteritis (ICD-9-CM = 558.9), and dehydration (ICD-9-CM = 276.5). Usage measures, such as preventive care visits or ED visits, were created using Maryland Medicaid codes, Current Procedural Terminology codes, and ICD-9-CM codes. Linear regression was used to model trend. Logistic regression was used to model the probability of ambulatory and inpatient care given MAC enrollment and other covariates. First, logistic regression was used to predict the probability of any ambulatory care use among all MAC-eligible children during a quarter to model changes in access that may have occurred during MAC. Then, among users of ambulatory care or inpatient care, logistic regression was used to predict the probability of hospitalization.

RESULTS

Most of the children studied were in the AFDC program, about half were African-American, one third resided in Baltimore City, and 9% of children had ICD-9-CMs reflecting chronic disease. The mean percentage of time children were MAC-eligible per quarter was 91%. Only 5% of children were continuously enrolled for all 20 quarters included in this study. Per-capita ambulatory care visits, especially per-capita preventive care visits, increased significantly during the study period (b = 0.003) whereas per-capita ED visits did not change. The mean n

The rational clinical examination. Does this infant have pneumonia?

Acute lower respiratory tract illness is common among children seen in primary care. We reviewed the accuracy and precision of the clinical examination in detecting pneumonia in children. Although most cases are viral, it is important to identify bacterial pneumonia to provide appropriate therapy. Studies were identified by searching MEDLINE from 1982 to 1995, reviewing reference lists, reviewing a published compendium of studies of the clinical examination, and consulting experts. Observer agreement is good for most signs on the clinical examination. Each study was reviewed by 2 observers and graded for methodologic quality. There is better agreement about signs that can be observed (eg, use of accessory muscles, color, attentiveness; kappa, 0.48-0.66) than signs that require auscultation of the chest (eg, adventitious sounds; kappa, 0.3). Measurements of the respiratory rate are enhanced by counting for 60 seconds. The best individual finding for ruling out pneumonia is the absence of tachypnea. Chest indrawing, and other signs of increased work of breathing, increases the likelihood of pneumonia. If all clinical signs (respiratory rate, auscultation, and work of breathing) are negative, the chest x-ray findings are unlikely to be positive. Studies are needed to assess the value of clinical findings when they are used together.

[Use of filgrastim (RHU G-CSF) in supplemental treatment of non Hodgkin's lymphoma (NHL) in children]

Clinical application of glycoproteins stimulating the growth (G-CSF), differentiation and activity of the cells of granulocyte line has become a landmark in the treatment of patients with neutropenia. It has been proved that filgrastim (rHU G-CSF) applied after intensive chemotherapy shortens the duration of neutropenia and decreases the frequency of occurrence of infections. The paper discusses the efficiency and tolerance of filgrastim in children treated for NHL. Filgrastim was applied in children with NHL T cell and B cell treated according to BFM 86 protocols. It was given in a dose of 5 micrograms/kg daily i.v. The duration of therapy ranged from 5-20 days. Altogether 47 cycles were performed. 25 cycles were performed in 12 children during granulocytopenia (< 1 x 10(9)/l). The median time of neutropenia recovery, the frequency of severe infection and chemotherapy retardation were significantly lower in the examined than in the control group (p < 0.05). In 6 children 22 courses of filgrastim were given prophylactically after the cycles of intensive chemotherapy of NHL. Only during two courses due to neutropenia the chemotherapy retardation was necessary. Toleration of filgrastim was good. Application of filgrastim right after the intensive chemotherapy in children with NHL has considerably improved persistent realization of treatment programmes. Tolerance of the drug was good.