We use smoothed particle hydrodynamic simulations of cold, uniform density, self-gravitating filaments, to investigate their longitudinal collapse time-scales; these time-scales are important because ...they determine the time available for a filament to fragment into cores. A filament is initially characterized by its line-mass, μO, its radius, R
O (or equivalently its density
$\rho _{{\rm O}}= \mu _{{\rm O}}/\pi R_{{\rm O}}^2$
), and its aspect ratio, A
O (≡Z
O/R
O, where Z
O is its half-length). The gas is only allowed to contract longitudinally, i.e. parallel to the symmetry axis of the filament (the z-axis). Pon et al. (2012) have considered the global dynamics of such filaments analytically. They conclude that short filaments (A
O ≲ 5) collapse along the z-axis more-or-less homologously, on a time-scale t
HOM ∼ 0.44 A
O (GρO)−1/2; in contrast, longer filaments (A
O ≳ 5) undergo end-dominated collapse, i.e. two dense clumps form at the ends of the filament and converge on the centre sweeping up mass as they go, on a time-scale
$t_{{\rm END}} \sim 0.98\,A_{{\rm O}}^{1/2}\,(G\rho _{{\rm O}})^{-1/2}$
. Our simulations do not corroborate these predictions. First, for all A
O ≳ 2, the collapse time satisfies a single equation
\begin{equation*}
t_{{\rm COL}}\sim (0.49+0.26A_{{\rm O}})(G\rho _{{\rm O}})^{-1/2}\,,
\end{equation*}
which for large A
O is much longer than the Pon et al. prediction. Secondly, for all A
O ≳ 2, the collapse is end-dominated. Thirdly, before being swept up, the gas immediately ahead of an end-clump is actually accelerated outwards by the gravitational attraction of the approaching clump, resulting in a significant ram pressure. For high aspect ratio filaments, the end-clumps approach an asymptotic inward speed, due to the fact that they are doing work both accelerating and compressing the gas they sweep up. Pon et al. appear to have neglected the outward acceleration and its consequences.
Self-monitoring blood glucose (SMBG) systems have the potential to play an important role in the management of diabetes and in the reduction of risk of serious secondary clinical complications. This ...review describes the transition from simple urine sugar screening tests to sophisticated meter and reagent strip systems to monitor blood glucose. Significant developments in design and technology over the past four decades are described since the first meter was introduced in 1970. Factors that have influenced this evolution and the challenges to improve analytical performance are discussed. Current issues in the role of SMBG from the clinical, patient and manufacturer perspectives, notably adherence, costs and regulations, are also considered.
Rationale
50-kHz ultrasonic vocalizations (USVs) emitted by adult rats are heterogeneous; they occur over a wide frequency range, show varying degrees of frequency modulation, and appear to differ in ...their behavioral significance. However, they have not been extensively categorized.
Objectives
The main objective of this study was to identify subtypes of 50-kHz USVs emitted by adult rats and to determine how amphetamine (AMPH) or social testing condition affects their relative and absolute production rate and acoustic characteristics. A second objective was to determine the extent of individual differences in call rate, call subtype profile, and acoustic parameters (i.e., duration, bandwidth, and mean peak frequency).
Methods
Adult male Long–Evans rats were administered systemic amphetamine (0.25–2 mg/kg, IP) and tested individually or with a cage mate for 20 min. Call categories were defined based on visual inspection of over 20,000 USV spectrograms. Surgical devocalization was performed on a subset of AMPH-tested rats in order to confirm the authenticity of call subtypes.
Results
Fourteen categories of 50-kHz USVs were recognized. Call subtypes were differentially affected by social context, AMPH dose, and time within session. In contrast, the acoustic characteristics of call subtypes were notably stable. Marked and stable inter-individual differences occurred with respect to overall 50-kHz call rate, acoustic parameters, and call profile.
Conclusions
The present findings, obtained under saline and amphetamine test conditions, provide the first detailed classification of adult rat 50-kHz USVs. Consideration of 50-kHz USV subtypes may advance our understanding of inter-rat communication and affective state.
Perturbation growth in accreting filaments Clarke, S. D; Whitworth, A. P; Hubber, D. A
Monthly notices of the Royal Astronomical Society,
05/2016, Letnik:
458, Številka:
1
Journal Article
Recenzirano
Odprti dostop
We use smoothed particle hydrodynamic simulations to investigate the growth of perturbations in infinitely long filaments as they form and grow by accretion. The growth of these perturbations leads ...to filament fragmentation and the formation of cores. Most previous work on this subject has been confined to the growth and fragmentation of equilibrium filaments and has found that there exists a preferential fragmentation length-scale which is roughly four times the filament's diameter. Our results show a more complicated dispersion relation with a series of peaks linking perturbation wavelength and growth rate. These are due to gravo-acoustic oscillations along the longitudinal axis during the sub-critical phase of growth. The positions of the peaks in growth rate have a strong dependence on both the mass accretion rate onto the filament and the temperature of the gas. When seeded with a multiwavelength density power spectrum, there exists a clear preferred core separation equal to the largest peak in the dispersion relation. Our results allow one to estimate a minimum age for a filament which is breaking up into regularly spaced fragments, as well as an average accretion rate. We apply the model to observations of filaments in Taurus by Tafalla & Hacar and find accretion rates consistent with those estimated by Palmeirim et al.
Advances in the treatment of metastatic colorectal cancer (mCRC) in the last decade have significantly improved survival; however, simple biomarkers to predict response or toxicity have not been ...identified, which are applicable to all community oncology settings worldwide. The use of inflammatory markers based on differential white-cell counts, such as the neutrophil/lymphocyte ratio (NLR), may be simple and readily available biomarkers.
Clinical information and baseline laboratory parameters were available for 349 patients, from two independent cohorts, with unresectable mCRC receiving first-line palliative chemotherapy. Associations between baseline prognostic variables, including inflammatory markers such as the NLR and tumour response, progression and survival were investigated.
In the training cohort, combination-agent chemotherapy (P=0.001) and NLR ≤ 5 (P=0.003) were associated with improved clinical benefit. The ECOG performance status 1 (P=0.002), NLR>5 (P=0.01), hypoalbuminaemia (P=0.03) and single-agent chemotherapy (P<0.0001) were associated with increased risk of progression. The ECOG performance status ≥ 1 (P=0.004) and NLR>5 (P=0.002) predicted worse overall survival (OS). The NLR was confirmed to independently predict OS in the validation cohort (P<0.0001). Normalisation of the NLR after one cycle of chemotherapy in a subset of patients resulted in improved progression-free survival (P=0.012).
These results have highlighted NLR as a potentially useful clinical biomarker of systemic inflammatory response in predicting clinically meaningful outcomes in two independent cohorts. Results of this study have also confirmed the importance of a chronic systemic inflammatory response influencing clinical outcomes in patients with mCRC.
Increased efficiency of energy harvest, due to alterations in the gut microbiota (increased Firmicutes and decreased Bacteroidetes), has been implicated in obesity in mice and humans. However, a ...causal relationship is unproven and contributory variables include diet, genetics and age. Therefore, we explored the effect of a high-fat (HF) diet and genetically determined obesity (ob/ob) for changes in microbiota and energy harvesting capacity over time.
Seven-week-old male ob/ob mice were fed a low-fat diet and wild-type mice were fed either a low-fat diet or a HF-diet for 8 weeks (n=8/group). They were assessed at 7, 11 and 15 weeks of age for: fat and lean body mass (by NMR); faecal and caecal short-chain fatty acids (SCFA, by gas chromatography); faecal energy content (by bomb calorimetry) and microbial composition (by metagenomic pyrosequencing).
A progressive increase in Firmicutes was confirmed in both HF-fed and ob/ob mice reaching statistical significance in the former, but this phylum was unchanged over time in the lean controls. Reductions in Bacteroidetes were also found in ob/ob mice. However, changes in the microbiota were dissociated from markers of energy harvest. Thus, although the faecal energy in the ob/ob mice was significantly decreased at 7 weeks, and caecal SCFA increased, these did not persist and faecal acetate diminished over time in both ob/ob and HF-fed mice, but not in lean controls. Furthermore, the proportion of the major phyla did not correlate with energy harvest markers.
The relationship between the microbial composition and energy harvesting capacity is more complex than previously considered. While compositional changes in the faecal microbiota were confirmed, this was primarily a feature of high-fat feeding rather than genetically induced obesity. In addition, changes in the proportions of the major phyla were unrelated to markers of energy harvest which changed over time. The possibility of microbial adaptation to diet and time should be considered in future studies.
Sucrose preference (SP) is a widely used measure of anhedonia in rat models of depression, yet depressed patients do not reliably show an analogous deficit. As an alternative affect-related measure, ...adult rat ultrasonic vocalizations (USVs) are attracting interest, but it is unclear whether SP and USVs provide independent measures. Here, we have assessed whether SP and USV emission are correlated in the absence of a depressogenic procedure. To this end, 24 male Long-Evans rats were tested daily for 24 days, with alternating SP tests and USV recordings; after a 3-month hiatus, USV emission was re-evaluated for 6 more days. SP was measured in simultaneous two-bottle choice tests, and USVs were recorded in an open field. The main measures were: SP, 50-kHz call rate, and relative prevalence of trill and flat call subtypes. These measures showed temporally-stable individual differences across the initial 24-day testing period, and at the 3-month USV follow-up tests. Correlational analysis revealed no significant relationships between SP and the three main USV measures. Rats differed consistently, not only in their 50-kHz call rates but also in their 50-kHz call profiles (i.e., the relative prevalence of 14 call subtypes); most rats preferentially emitted either trill or flat calls. Several inter-call subtype associations were detected, including a strong negative relationship between the relative prevalence of flat and trill calls. The 50-kHz call rate was correlated with the relative prevalence of only one call subtype (short calls, negative correlation), but was positively correlated with absolute emission rates for almost all subtypes. In conclusion, adult rats exhibited temporally-stable individual differences over weeks (SP) or months (USVs) of testing. This trait-like stability helped to reveal a lack of relationship between SP and the USV-related variables under study, suggesting that these measures may capture different constructs of possible relevance to animal models of depression.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The neutrophil lymphocyte ratio (NLR) has prognostic value in patients with a variety of cancers. Many chemotherapeutic trial databases hold information on white cell and neutrophil counts only. The ...aim of the present study was to compare the prognostic value of the NLR with a derived score (dNLR), composed of white cell and neutrophil counts.
Patients (n=27,031) who were sampled incidentally between 2000 and 2007 for neutrophil, lymphocyte and white cell counts, and also had a diagnosis of cancer (Scottish Cancer Registry), were identified. Of this group, 12,118 patients who had been sampled within 2 years of their cancer diagnosis were studied.
On follow-up, there were 7366 deaths, of which 6198 (84%) were cancer deaths. The median time from blood sampling to diagnosis was 2.1 months. The area under the receiver-operating characteristic (ROC) curve for cancer-specific survival was 0.650 for the NLR and 0.640 for the dNLR. The NLR and dNLR were independently associated with survival in all cancers studied (all P<0.001). The optimal thresholds, on the basis of hazard ratios and area under the curve, were 4 : 1 for the NLR and 2 : 1 for the dNLR.
The results of the present study show that the dNLR has similar prognostic value to the NLR. Therefore, the universally available dNLR is to be commended for use in the risk stratification of patients undergoing chemotherapy.
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