Modelling foraging competition between solitarious and gregarious organisms in increasingly heterogeneous environments.

Density dependent phase polyphenism is the exhibiting of two or more distinct phenotypes from a single genotype depending on local population density. The most well known insect to exhibit this phenomenon is the locust, with whom the profound effect on behaviour leads to the classification of the two phases; solitarious, where locusts actively avoid other locusts, and gregarious, where locusts are strongly attracted to other locusts. It has been shown that food distributions at both small and large scales have an effect on the process of gregarisation. While gregarisation offers advantages, such as greater predator avoidance, the relationship between phase polyphenism and potential foraging benefits is still not fully understood. In this paper, we explore the effect of gregarisation on foraging within increasingly heterogeneous environments using a partial differential equation model. We first consider a single two dimensional simulation of a spatially heterogeneous environment to understand the mechanics of gregarious/solitarious foraging. We then look at the steady state foraging advantage (measured as the ratio of per-capita contact with food) in environments ranging from homogeneous to very spatially heterogeneous. Finally, we perform a parameter sensitivity analysis to find which model parameters have the greatest effect on foraging advantage. We find that during the aggregation stage, prior to the onset of marching (which we do not model here), in increasingly heterogeneous food environments it is better to be gregarious than solitarious. In addition, we find that this is intrinsic to the gregarious/solitarious behavioural dynamic as it occurs almost regardless of the model parameters. That is to say, it doesn't matter how fast the organisms disperse or how strong their long range interactions as long as there is the solitarious/gregarious behaviour the gregarious foraging advantage will exist.

Outcome of partial mandibular reconstruction with fibula grafts and implant-supported prostheses.

This study sought to evaluate the outcome of patients treated with fibula grafts for partial mandibular reconstruction and implant-supported prosthesis at a Danish university hospital. Patient inclusion criteria were: partial mandibular resection, reconstruction with a fibula graft, and treatment during the period 1998-2011. Patients with incomplete medical records were excluded. Thirty-six patients were included, of whom 16 were treated with an implant-supported prosthesis. Relevant presurgical, intraoperative, and postoperative parameters were registered. The fibula graft survival rate at the last follow-up (mean follow-up 22 months, range 0-89 months) was 97%. Half of the patients experienced non-severe complications such as loosening of osteosynthesis material, fistulae, and graft exposure. One of 37 fibula grafts in the 36 patients was removed due to infection. The implant survival rate was 96%; three of 67 implants were lost due to infection. Eight implants were not included in the prosthetic rehabilitation. Fibula graft surgery for mandibular reconstruction was found to be a reliable treatment modality with a high survival rate. Rehabilitation with implant-supported prostheses was characterized by high survival rates and few complications. The results obtained are comparable to those of previous studies.

Using field data to test locust migratory band collective movement models.

Wingless locust nymphs can form massive migratory groups known as bands, whose coordinated movement results from local interactions. We analysed the spatial distribution of locusts within naturally occurring bands and compared them with computer simulations to infer which interaction rules are used by individuals. We found that the empirical radial distribution of neighbours around a focal individual was isotropic, indicating a tendency for locusts to interact with neighbours all around them, rather than a bias towards pursuing individuals ahead or escaping from the ones following behind. By using maps of neighbour densities and pair correlation functions, we found evidence for a short-range repulsion force, balanced by a clustering force, presumably alignment and/or attraction, at a distance of around 3 cm. These results were similar to those observed when using a 'zonal' self-propelled particles model where repulsion/alignment/attraction forces are delimited by concentric circular zones of set radii. However, the profiles obtained either by using different combinations of forces, limiting the number of neighbours involved in interactions, or by varying the range of some zones, all appeared to produce similar results, thereby limiting the ability to more precisely determine the rules underlying locust interactions.

From disorder to order in marching locusts.

Recent models from theoretical physics have predicted that mass-migrating animal groups may share group-level properties, irrespective of the type of animals in the group. One key prediction is that as the density of animals in the group increases, a rapid transition occurs from disordered movement of individuals within the group to highly aligned collective motion. Understanding such a transition is crucial to the control of mobile swarming insect pests such as the desert locust. We confirmed the prediction of a rapid transition from disordered to ordered movement and identified a critical density for the onset of coordinated marching in locust nymphs. We also demonstrated a dynamic instability in motion at densities typical of locusts in the field, in which groups can switch direction without external perturbation, potentially facilitating the rapid transfer of directional information.

Proton dynamics in letovicite, (NH4)3H(SO4)2: a 1H and 14N NMR spectroscopic study.

The improper ferroelastic phase letovicite (NH4)3H(SO4)2 has been studied by 1H MAS NMR as well as by static 14N NMR experiments in the temperature range of 296-425 K. The 1H MAS NMR resonance from ammonium protons can be well distinguished from that of acidic protons. A third resonance appears just below the phase transition temperature which is due to the acidic protons in the paraelastic phase. The lowering of the second moment M2 for the ammonium protons takes place in the same temperature range as the formation of domain boundaries, while the signals of the acidic protons suffer a line narrowing in the area of Tc. The static 14N NMR spectra confirm the temperature of the motional changes of the ammonium tetrahedra. Two-dimensional 1H NOESY spectra indicate a chemical exchange between ammonium protons and the acidic protons of the paraphase.

The crystallization kinetics of sodalites grown by the hydrothermal transformation of kaolinite studied by 29Si MAS NMR.

The hydrothermal transformation of kaolinite to basic sodalite Na8[AlSiO4]6 (OH.H2O)2 and hydroxoborate sodalite Na8[AlSiO4]6 [B(OH)4]2 has been investigated at different temperatures (353 and 473 K). In the early stage of the reactions, the crystallization kinetics was studied by X-ray powder diffraction, thermogravimetry, IR spectroscopy and 29Si MAS NMR spectroscopy. Besides the crystallization of the sodalites, no further intermediate phases were formed. MAS NMR of the 29Si nucleus has been found to be a versatile tool to follow the progress of reactions from the signal ratio of the initial material and the crystallization product because the differences in chemical shifts result in well-separated signals. From these measurements, the growth rates of the sodalites could be determined quantitatively even for the very early stages of crystallization. It was found that sodium carbonate impurities in the NaOH solution used for the synthesis has an important influence on the reaction kinetics.

Ponderal index: a better definition of the 'at risk' group with intrauterine growth problems than birth-weight for gestational age in term infants.

A study was undertaken at Nepean Hospital, Penrith to compare the outcome of pregnancies with growth retarded infants; 2,508 consecutive births were analyzed between August 1, 1989 and April 30, 1990. A comparison of outcome was made between infants whose birth-weight for gestational age was below the tenth percentile and infants who had a low ponderal index from 37 weeks' gestation. The Caesarean section delivery and fetal distress rates were significantly higher for infants with a low ponderal index than for infants with a low birth-weight. Ponderal index appears to be a better measure of infants with intrauterine growth problems than birth-weight percentiles.

Verapamil-induced inhibition of theophylline elimination in healthy humans.

The interaction between theophylline and verapamil was investigated in 7 healthy volunteers. Oral administration of verapamil in a dose of 120 mg t.i.d. for 7 days caused a significant inhibition of the elimination of theophylline (5 mg/kg intravenously). Theophylline clearance was reduced from 45.2 to 36.1 ml/hr/kg (20.1%; P less than 0.005). The apparent steady-state volume of distribution of the drug was not influenced. The terminal half-life of theophylline was increased from 6.80 to 8.23 hr (21.0%; P less than 0.001). Increased steady-state plasma theophylline concentrations may thus be expected when verapamil is added to a drug regimen which includes theophylline.

Deficiency of reticular fibers in cerebral arteries. On the etiology of saccular aneurysms in childhood.

A 5-year-old, previous healthy, girl developed a large hematoma of the right cerebral hemisphere and died. An aneurysm was strongly suggested. As previously found in adult aneurysm patients, histological and morphometric investigations showed an abnormality of the reticular fibers of the cerebral arteries. We suggest that arterial deficiency of reticular fibers is of importance in formation and rupture of saccular aneurysm, also in childhood.

Flow rates in the head and neck lymphatics after food stimulation in healthy subjects. Clinical value.

In 22 healthy subjects lymph transport flow rates was studied in the head lymphatics after food stimulation, mastication (chewing) and taste. After food stimulation there was a significantly higher transport rate (0.67 meter/hour) than after taste (0.57 meter/hour) and mastication (0.55 meter/hour). The calculation of transport flow rate was independent of quantitative distribution of radioactivity in the head and neck lymphatics, and it could therefore perhaps be of clinical value.

Lymphoscintigraphy in the head and neck in normals diagnostic value.

The lymphoscintigraphic pattern in the head and neck lymphatics was studied in 45 healthy subjects. After submucous injection of Lymphoscint-solco in the oral cavity there was visualization of regional lymph nodes immediately after food intake. There was an extreme variation in the number of visualized lymph nodes and a lack symmetry between right and left side of the neck. The accumulated radioactivity in subsequent lymph nodes showed an extreme variation. Accordingly no characteristics of diagnostic value could be evaluated from this study.

Velocity of lymph flow in the head and neck lymphatics during food stimulation. Preliminary communication.

In 12 healthy volunteers the velocity of food stimulated lymph flow in the head and neck lymphatics was studied. The velocity of lymph flow between subsequent lymph nodes had a mean of 0,6 mm/sec with a range of 0,4--1.4 mm/sec thus reaching the range of the velocity of blood in the capillaries.

Recurrent urinary incontinence treated neurosurgically.

Neurogenic bladder dysfunction can be difficult to manage and is usually impossible to cure. This case report describes neurosurgical treatment of a case of recurrent urinary incontinence in a 56 years old woman who was previously treated on four occasions with vaginal repair operations with no beneficial effect. Cystometry revealed detrusor hyperreflexia (supranuclear bladder paresis). Myelography demonstrated cervical spinal cord compression. She was treated with spondylodesis of the cervical spine with complete relief of incontinence. 18 months postoperative cystometry was normal and after three years she was free of symptoms.

Recurrent urinary incontinence treated with quite another type of prolapse operation.

A case of neurosurgical treatment of recurrent urinary incontinence caused by detrusor hyperreflexia is reported. The importance of cystometry in the diagnosis of recurrent urinary incontinence is stressed.