35 research outputs found
Origin of Polar Order in Dense Suspensions of Phototactic Micro-Swimmers
A main question for the study of collective motion in living organisms is the origin of orientational polar order, i.e., how organisms align and what are the benefits of such collective behaviour. In the case of micro-organisms swimming at a low Reynolds number, steric repulsion and long-range hydrodynamic interactions are not sufficient to explain a homogeneous polar order state in which the direction of motion is aligned. An external symmetry-breaking guiding field such as a mechanism of taxis appears necessary to understand this phonemonon. We have investigated the onset of polar order in the velocity field induced by phototaxis in a suspension of a motile micro-organism, the algae Chlamydomonas reinhardtii, for density values above the limit provided by the hydrodynamic approximation of a force dipole model. We show that polar order originates from a combination of both the external guiding field intensity and the population density. In particular, we show evidence for a linear dependence of a phototactic guiding field on cell density to determine the polar order for dense suspensions and demonstrate the existence of a density threshold for the origin of polar order. This threshold represents the density value below which cells undergoing phototaxis are not able to maintain a homogeneous polar order state and marks the transition to ordered collective motion. Such a transition is driven by a noise dominated phototactic reorientation where the noise is modelled as a normal distribution with a variance that is inversely proportional to the guiding field strength. Finally, we discuss the role of density in dense suspensions of phototactic micro-swimmers
Trade-offs between multifunctionality and profit in tropical smallholder landscapes
Land-use transitions can enhance the livelihoods of smallholder farmers but potential economic-ecological trade-offs remain poorly understood. Here, we present an interdisciplinary study of the environmental, social and economic consequences of land-use transitions in a tropical smallholder landscape on Sumatra, Indonesia. We find widespread biodiversity-profit trade-offs resulting from land-use transitions from forest and agroforestry systems to rubber and oil palm monocultures, for 26,894 aboveground and belowground species and whole-ecosystem multidiversity. Despite variation between ecosystem functions, profit gains come at the expense of ecosystem multifunctionality, indicating far-reaching ecosystem deterioration. We identify landscape compositions that can mitigate trade-offs under optimal land-use allocation but also show that intensive monocultures always lead to higher profits. These findings suggest that, to reduce losses in biodiversity and ecosystem functioning, changes in economic incentive structures through well-designed policies are urgently needed
Use of a non-associated flow rule for determining the stability of a vertical circular excavation
Combined influence of teichoic acids from Staphylococcus aureus and heterometallik Cu/Cd ethylenediamine complex on peritoneal macrophages and tumor cells
We investigated the effects of teichoic acid (TA) from Staphylococcus aureus Wood 46 on tumor growth and metastasis of the experimental Lewis lung carcinoma (LLC) in mice. Intranasal administration of TA alone aggravated both tumor growth and metastasis, whereas combined administration of TA with a synthetic bimetallic (copper: cadmium) ethylene diamine complex PO244 resulted in pronounced antitumor and antimetastatic effects. The group of animals subjected to the combined treatment with TA and PO244 manifested the highest degree of lymphocyte infiltration into the tumor tissue, compared to the control group and those exposed to TA or PO244 alone. Moreover, the combined treatment negatively affected the adhesive properties of peritoneal macrophages in the LLC bearing mice. Co-cultivation of the isolated macrophages with primary LLC cultures revealed significant (p < 0.05) cytotoxic and cytostatic effects, detected as an increased level of apoptosis and a reduced fraction of replicating cells.ΠΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π»ΠΈ ΠΌΠΎΠ΄ΠΈΡΠΈΡΠΈΡΡΡΡΠ΅Π΅ Π²Π»ΠΈΡΠ½ΠΈΠ΅ ΡΠ΅ΠΉΡ
ΠΎΠ΅Π²ΠΎΠΉ ΠΊΠΈΡΠ»ΠΎΡΡ (Π’Π) Π½Π° ΡΠΎΡΡ ΠΈ ΠΌΠ΅ΡΠ°ΡΡΠ°Π·ΠΈΡΠΎΠ²Π°Π½ΠΈΠ΅ ΠΏΠ΅ΡΠ΅Π²ΠΈΠ²Π°Π΅ΠΌΠΎΠΉ ΠΊΠ°ΡΡΠΈΠ½ΠΎΠΌΡ Π»Π΅Π³ΠΊΠΈΡ
ΠΡΡΠΈΡ Ρ ΠΌΡΡΠ΅ΠΉ. ΠΡΡΠ²Π»Π΅Π½Π° Π³ΠΈΠΏΠ΅ΡΠ°ΠΊΡΠΈΠ²Π°ΡΠΈΡ ΡΠΎΡΡΠ° ΠΈ ΠΌΠ΅ΡΠ°ΡΡΠ°Π·ΠΈΡΠΎΠ²Π°Π½ΠΈΡ ΠΏΠ΅ΡΠ²ΠΈΡΠ½ΠΎΠΉ ΠΎΠΏΡΡ
ΠΎΠ»ΠΈ ΠΏΡΠΈ ΠΈΠ½ΡΡΠ°Π½Π°Π·Π°Π»ΡΠ½ΠΎΠΌ Π²Π²Π΅Π΄Π΅Π½ΠΈΠΈ ΠΆΠΈΠ²ΠΎΡΠ½ΡΠΌ Π’Π, Π² ΡΠΎ Π²ΡΠ΅ΠΌΡ ΠΊΠ°ΠΊ ΠΏΡΠΈ ΠΊΠΎΠΌΠ±ΠΈΠ½ΠΈΡΠΎΠ²Π°Π½Π½ΠΎΠΌ Π²Π»ΠΈΡΠ½ΠΈΠΈ Ρ Π Π244 Π½Π°Π±Π»ΡΠ΄Π°Π»ΠΈ ΡΡΠΈΠ»Π΅Π½ΠΈΠ΅ ΠΏΡΠΎΡΠΈΠ²ΠΎ-ΠΎΠΏΡΡ
ΠΎΠ»Π΅Π²ΠΎΠ³ΠΎ ΡΡΡΠ΅ΠΊΡΠ°. Π‘Π°ΠΌΡΠΉ Π²ΡΡΠΎΠΊΠΈΠΉ ΡΡΠΎΠ²Π΅Π½Ρ ΠΈΠ½ΡΠΈΠ»ΡΡΡΠ°ΡΠΈΠΈ ΠΎΠΏΡΡ
ΠΎΠ»Π΅Π²ΠΎΠΉ ΡΠΊΠ°Π½ΠΈ Π»ΠΈΠΌΡΠΎΡΠΈΡΠ°ΠΌΠΈ Π·Π°ΡΠΈΠΊΡΠΈΡΠΎΠ²Π°Π»ΠΈ Π² Π³ΡΡΠΏΠΏΠ΅ ΠΆΠΈΠ²ΠΎΡΠ½ΡΡ
, ΠΊΠΎΡΠΎΡΡΠΌ ΠΏΡΠΎΠ²ΠΎΠ΄ΠΈΠ»ΠΈ ΠΊΠΎΠΌΠ±ΠΈΠ½ΠΈΡΠΎΠ²Π°Π½Π½ΡΡ ΡΠ΅ΡΠ°ΠΏΠΈΡ Π’Π Ρ Π Π 244. ΠΠΎΠΊΠ°Π·Π°Π½ΠΎ ΡΠ½ΠΈΠΆΠ΅Π½ΠΈΠ΅ Π°Π΄Π³Π΅Π·ΠΈΠ²Π½ΡΡ
ΡΠ²ΠΎΠΉΡΡΠ² ΠΏΠ΅ΡΠΈΡΠΎΠ½Π΅Π°Π»ΡΠ½ΡΡ
ΠΌΠ°ΠΊΡΠΎΡΠ°Π³ΠΎΠ² ΠΏΠΎΠ΄ Π²Π»ΠΈΡΠ½ΠΈΠ΅ΠΌ Π±ΠΈΠΌΠ΅ΡΠ°Π»Π»ΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ ΠΊΠΎΠΌΠΏΠ»Π΅ΠΊΡΠ°. ΠΠΎΡΠ»Π΅ ΡΠΎΠΊΡΠ»ΡΡΠΈΠ²ΠΈΡΠΎΠ²Π°Π½ΠΈΡ ΠΌΠ°ΠΊΡΠΎΡΠ°Π³ΠΎΠ² ΠΎΡ ΠΆΠΈΠ²ΠΎΡΠ½ΡΡ
, ΠΊΠΎΡΠΎΡΡΠΌ ΠΏΡΠΎΠ²ΠΎΠ΄ΠΈΠ»ΠΈ ΠΊΠΎΠΌΠ±ΠΈΠ½ΠΈΡΠΎΠ²Π°Π½Π½ΡΡ ΡΠ΅ΡΠ°ΠΏΠΈΡ Ρ ΠΏΠ΅ΡΠ²ΠΈΡΠ½ΠΎΠΉ ΠΊΡΠ»ΡΡΡΡΠΎΠΉ LLC, Π²ΡΡΠ²Π»Π΅Π½ΠΎ Π·Π½Π°ΡΠΈΡΠ΅Π»ΡΠ½ΠΎΠ΅ (p < 0.05) ΡΠΈΡΠΎΡΠΎΠΊΡΠΈΡΠ΅ΡΠΊΠΎΠ΅/ΡΠΈΡΠΎΡΡΠ°ΡΠΈΡΠ΅ΡΠΊΠΎΠ΅ Π²Π»ΠΈΡΠ½ΠΈΠ΅, ΡΡΠΎ ΠΏΡΠΎΡΠ²Π»ΡΠ»ΠΎΡΡ Π² ΡΠ²Π΅Π»ΠΈΡΠ΅Π½ΠΈΠΈ ΡΡΠΎΠ²Π½Ρ Π°ΠΏΠΎΠΏΡΠΎΠ·Π° ΠΈ ΡΠΌΠ΅Π½ΡΡΠ΅Π½ΠΈΠΈ ΠΏΠΎΠΏΡΠ»ΡΡΠΈΠΈ ΠΊΠ»Π΅ΡΠΎΠΊ ΠΏΡΠΎΠ»ΠΈΡΠ΅ΡΠ°ΡΠΈΠ²Π½ΠΎΠ³ΠΎ ΠΏΡΠ»Π°
Investigating the role of mind wandering in computer-supported collaborative work:A proposal for an EEG study
Utilization of CT scanning associated with complex spine surgery
BACKGROUND: Due to the risk associated with exposure to ionizing radiation, there is an urgent need to identify areas of CT scanning overutilization. While increased use of diagnostic spinal imaging has been documented, no previous research has estimated the magnitude of follow-up imaging used to evaluate the postoperative spine. METHODS: This retrospective cohort study quantifies the association between spinal surgery and CT utilization. An insurance database (Humana, Inc.) withβββ19 million enrollees was employed, representing 8 consecutive years (2007β2014). Surgical and imaging procedures were captured by anatomic-specific CPT codes. Complex surgeries included all cervical, thoracic and lumbar instrumented spine fusions. Simple surgeries included discectomy and laminectomy. Imaging was restricted to CT and MRI. Postoperative imaging frequency extended to 5-years post-surgery. RESULTS: There were 140,660 complex spinal procedures and 39,943 discectomies and 49,889 laminectomies. MRI was the predominate preoperative imaging modality for all surgical procedures (median: 80%; range: 73β82%). Postoperatively, CT prevalence following complex procedures increased more than two-fold from 6Β months (18%) to 5Β years (β₯40%), and patients having a postoperative CT averaged two scans. For simple procedures, the prevalence of postoperative CT scanning never exceeded 30%. CONCLUSIONS: CT scanning is used frequently for follow-up imaging evaluation following complex spine surgery. There is emerging evidence of an increased cancer risk due to ionizing radiation exposure with CT. In the setting of complex spine surgery, actions to mitigate this risk should be considered and include reducing nonessential scans, using the lowest possible radiation dose protocols, exerting greater selectivity in monitoring the developing fusion construct, and adopting non-ferromagnetic implant biomaterials that facilitate MRI postoperatively. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12891-017-1420-9) contains supplementary material, which is available to authorized users