Modelling and simulation of brinicle formation.

Below the Arctic sea ice, under the right conditions, a flux of icy brine flows down into the sea. The icy brine has a much lower fusion point and is denser than normal seawater. As a result, it sinks while freezing everything around it, forming an ice channel called a brinicle (also known as ice stalactite). In this paper, we develop a mathematical model for this phenomenon, assuming cylindrical symmetry. The fluid is considered to be viscous and quasi-stationary. The heat and salt transport are weakly coupled to the fluid motion and are modelled with the corresponding conservation equations, accounting for diffusive and convective effects. Finite-element discretization is employed to solve the coupled system of partial differential equations. We find that the model can capture the general behaviour of the physical system and generate brinicle-like structures while also recovering dendrite composition, which is a physically expected feature aligned with previous experimental results. This represents, to our knowledge, the first complete model proposed that captures the global structure of the physical phenomenon even though it has some discrepancies, such as brine accumulation.

Sites of Circadian Clock Neuron Plasticity Mediate Sensory Integration and Entrainment.

Networks of circadian timekeeping in the brain display marked daily changes in neuronal morphology. In Drosophila melanogaster, the striking daily structural remodeling of the dorsal medial termini of the small ventral lateral neurons has long been hypothesized to mediate endogenous circadian timekeeping. To test this model, we have specifically abrogated these sites of daily neuronal remodeling through the reprogramming of neural development and assessed the effects on circadian timekeeping and clock outputs. Remarkably, the loss of these sites has no measurable effects on endogenous circadian timekeeping or on any of the major output functions of the small ventral lateral neurons. Rather, their loss reduces sites of glutamatergic sensory neurotransmission that normally encodes naturalistic time cues from the environment. These results support an alternative model: structural plasticity in critical clock neurons is the basis for proper integration of light and temperature and gates sensory inputs into circadian clock neuron networks.

Giga-voxel computational morphogenesis for structural design.

In the design of industrial products ranging from hearing aids to automobiles and aeroplanes, material is distributed so as to maximize the performance and minimize the cost. Historically, human intuition and insight have driven the evolution of mechanical design, recently assisted by computer-aided design approaches. The computer-aided approach known as topology optimization enables unrestricted design freedom and shows great promise with regard to weight savings, but its applicability has so far been limited to the design of single components or simple structures, owing to the resolution limits of current optimization methods. Here we report a computational morphogenesis tool, implemented on a supercomputer, that produces designs with giga-voxel resolution-more than two orders of magnitude higher than previously reported. Such resolution provides insights into the optimal distribution of material within a structure that were hitherto unachievable owing to the challenges of scaling up existing modelling and optimization frameworks. As an example, we apply the tool to the design of the internal structure of a full-scale aeroplane wing. The optimized full-wing design has unprecedented structural detail at length scales ranging from tens of metres to millimetres and, intriguingly, shows remarkable similarity to naturally occurring bone structures in, for example, bird beaks. We estimate that our optimized design corresponds to a reduction in mass of 2-5 per cent compared to currently used aeroplane wing designs, which translates into a reduction in fuel consumption of about 40-200 tonnes per year per aeroplane. Our morphogenesis process is generally applicable, not only to mechanical design, but also to flow systems, antennas, nano-optics and micro-systems.

Strategies For Immobilization Of Bioactive Organic Molecules On Titanium Implant Surfaces - A Review.

Numerous approaches have been used to improve the tissue-implant interface of titanium (Ti) and titanium alloy (Ti6Al4V). They all aim at increasing cell migration and attachment to the metal, preventing unspecific protein adsorption and improving post-implantation healing process. Promising methods for titanium and titanium alloy surface modification are based on the immobilization of biologically active organic molecules. New and interesting biochemical approaches to such surface modification include layer-by-layer deposition of polyelectrolyte films, phage display-selected surface binding peptides and self-assembled DNA monolayer systems. The present review summarizes the scientific information about these methods, which are at in vitro or in vivo development stages, and hopes to promote their future application in dental implantology and in oral and maxillofacial surgery.

Topology optimization for optical projection lithography with manufacturing uncertainties.

This article presents a topology optimization approach for micro- and nano-devices fabricated by optical projection lithography. Incorporating the photolithography process and the manufacturing uncertainties into the topology optimization process results in a binary mask that can be sent directly to manufacturing without additional optical proximity correction (OPC). The performance of the optimized device is robust toward the considered process variations. With the proposed unified approach, the design for photolithography is achieved by considering the optimal device performance and manufacturability at the same time. Only one optimization problem is solved instead of two as in the conventional separate procedures by (1) blueprint design and (2) OPC. A micro-gripper design example is presented to demonstrate the potential of this approach.

A retrospective study on the approach to the tooth in the fracture line of the mandible.

UNLABELLED: The presence of a tooth in the fracture line constitutes a specific problem in mandibular fractures. Therefore, our objective was to characterize the approach to teeth in the fracture line used in the Department of Maxillofacial Surgery, Plovdiv, by retrospectively investigating the association between various preoperative factors and the decision to extract or preserve the tooth. MATERIAL AND METHODS: The following variables were studied based on data from available hospital records: 1) gender and age of patients; 2) local preoperative infections; 3) time from trauma to treatment; 4) degree of fracture displacement; 5) relationship between tooth and fracture line; 6) periapical pathology; 7) periodontal diseases; 8) type of tooth in the fracture line; 9) degree of eruption; 10) method of treatment. RESULTS: 593 fractures with a tooth in the fracture line were included in the study. The tooth was preserved in 69.90 +/- 0.14% of the cases, it was extracted in 29.30 +/- 1.91% and exarticulated in 0.80 +/- 0.38% of all fracture lines. The results demonstrated the existing association between the studied variables and the decision to extract or preserve the tooth. Extraction was generally preferred in the following cases: if a local preoperative infection was present; the time from trauma to treatment was more than 72 hours; there was a significant displacement of the fracture; the dental root was fractured; periapical pathology or periodontal disease was present; the tooth was multi-rooted; or treatment consisted of open reduction and internal fixation. CONCLUSIONS: Making a decision to extract or preserve the tooth in the fracture line is a complex process. Each case, therefore, should be approached individually.

Growth factors--importance and possibilities for enhancement of the healing process in bone fractures.

UNLABELLED: The healing process after bone fractures is subject to complex regulation. A major part in it is played by biologically active molecules, called growth factors. The most important of these are the bone morphogenetic proteins (BMPs), transforming growth factor--beta (TGF-beta), platelet-derived growth factor (PDGF), fibroblast growth factor (FGF), insulin-like growth factor (IGF), vascular endothelial growth factor (VEGF), and epidermal growth factor (EGF). AIM: The aim of the present study was to do a short review of data in the scientific literature about the specific role of each factor in reparative osteogenesis in relation to the healing of bone fractures, as well as the possibilities for enhancement of this process by growth factors. MATERIAL AND METHODS: A detailed Medline search was conducted with emphasis on reports from the last ten years. CONCLUSION: The information gathered demonstrated the key role of growth factors and their potential for stimulation of healing of fractures and their complications. This conclusion is supported by results from numerous animal experiments.

Impact of adjunctive testing on the diagnosis and clinical course of patients with acute appendicitis.

The diagnosis of acute appendicitis is usually made from the history and physical examination. Recently, abdominal ultrasonography (US), laparoscopy, computerized tomography (CT), and barium enema (BE) have been used in the preoperative evaluation of patients with presumed appendicitis in order to improve the diagnostic accuracy. However, the usefulness of these tests in verifying the diagnosis of appendicitis has not been established. We reviewed the medical records of 203 patients who underwent appendectomy. One hundred patients were surgically treated before 1984 (group I) and 103 patients underwent surgery after 1988 (group II). Patients in group II were more likely to have preoperative US, laparoscopy, CT, or BE (24 in group II versus 3 in group I, p < 0.05). When groups I and II were compared, the rates of perforation (27% versus 20%), normal appendectomy (8% versus 11%), and the interval between admission and operation (12.2 hours versus 10.7 hours) and length of hospitalization (5.0 days versus 5.1 days) were not significantly different. We concluded that although adjunctive testing may be beneficial in selected patients, its routine use in patients suspected of having appendicitis cannot be advocated at present.