Rahoituskriisien ennustaminen varhaisten ennusmerkkien avulla

Erilaiset rahoituskriisit ovat vielä nykypäivänäkin merkittävä ongelma maailman eri talouksille. Kriisien reaaliset kustannukset ovat usein suuria ja ne voivat levitä laajemmille alueille aiheuttaen merkittäviä häiriöitä koko maailman taloudelle. Rahoituskriisejä on pyritty selittämään lukuisilla teorioilla, jotta niiden rakennetta ja syitä voitaisiin paremmin ymmärtää. Erityisesti 1990-luvun merkittävien valuuttakriisien motivoimana tutkijat ovat alkaneet kehittämään rahoituskriisejä ennustavia ns. varhaisten ennusmerkkien malleja. Nämä empiiriset mallit pyrkivät varoittamaan tulevasta kriisistä vertailemalla rahoituskriisiteorioista kerättyjen mahdollisten kriisi-indikaattorien normaalista poikkeavaa käytöstä ennen varsinaista kriisiä. Tämän tutkielman tarkoitus on syventyä tunnetuimpiin rahoituskriisejä ennustaviin varhaisten ennusmerkkien malleihin, niiden käyttämiin tilastollisiin menetelmiin ja malleja koskeviin ongelmiin. Tutkielmassa on myös empiirinen tutkimus, jossa estimoidaan kolmella eri menetelmällä varhaisten ennusmerkkien malli valuuttakriiseille. Tutkimuksessa käytetään vuositason dataa kuudelle kehittyvälle maalle Aasiasta ja Latinalaisesta Amerikasta vuosilta 1980 - 2010. Mallien in-sample ja out-of-sample ennusteiden avulla selvitetään, mikä menetelmä tuottaa parhaiten ennustavan mallin. Tutkimuksessa havaittiin estimoitujen varhaisten ennusmerkkien mallien olevan hyödyllisiä valuuttakriisien ennustamisessa kehittyville talouksille sekä mallin sisäisesti että out-of-sample. Rahoituskriisejä ennusti parhaiten moniarvoinen probit-malli, kun sitä verrattiin normaaliin probit-malliin ja epäparametrisen signaalimenetelmän komposiitti-indeksiin. Paras malli ennusti mallin sisäisesti rahoituskriisejä edeltävistä periodeista oikein 92 % ja talouden normaaleista periodeista 82 % oikein. Kyseinen malli ennusti myös kaikki ennalta valitut seitsemän rahoituskriisiä oikein out-of-sample. Tutkimuksen perusteella kehittyvien maiden valuuttakriisejä useimmiten edeltäisi reaalisen tuotannon supistuminen, pankkitalletusten selvä vähentyminen suhteessa maan tuotantoon, inflaation ja M2/reservit kasvu sekä kotimaisen luotonannon kasvu yksityiselle sektorille suhteessa maan tuotantoon. Datan alueellisen ja ajallisen heterogeenisuuden sekä kriisin jälkeisen harhan huomioiminen näyttää parantavan ennustetuloksia. Tutkimuksen tulokset ovat aikaisempien empiiristen tutkimusten ja teorian mukaisia.

Theses miscellaneae (1757-07-27)

Invokaatio: D.D.

13CO2 recovery fraction in expired air of septic patients under mechanical ventilation

The continuous intravenous administration of isotopic bicarbonate (NaH13CO2) has been used for the determination of the retention of the 13CO2 fraction or the 13CO2 recovered in expired air. This determination is important for the calculation of substrate oxidation. The aim of the present study was to evaluate, in critically ill patients with sepsis under mechanical ventilation, the 13CO2 recovery fraction in expired air after continuous intravenous infusion of NaH13CO2 (3.8 µmol/kg diluted in 0.9% saline in ddH2O). A prospective study was conducted on 10 patients with septic shock between the second and fifth day of sepsis evolution (APACHE II, 25.9 ± 7.4). Initially, baseline CO2 was collected and indirect calorimetry was also performed. A primer of 5 mL NaH13CO2 was administered followed by continuous infusion of 5 mL/h for 6 h. Six CO2 production (VCO2) measurements (30 min each) were made with a portable metabolic cart connected to a respirator and hourly samples of expired air were obtained using a 750-mL gas collecting bag attached to the outlet of the respirator. 13CO2 enrichment in expired air was determined with a mass spectrometer. The patients presented a mean value of VCO2 of 182 ± 52 mL/min during the steady-state phase. The mean recovery fraction was 0.68 ± 0.06%, which is less than that reported in the literature (0.82 ± 0.03%). This suggests that the 13CO2 recovery fraction in septic patients following enteral feeding is incomplete, indicating retention of 13CO2 in the organism. The severity of septic shock in terms of the prognostic index APACHE II and the sepsis score was not associated with the 13CO2 recovery fraction in expired air.

Trypanosoma cruzi infection induces up-regulation of cardiac muscarinic acetylcholine receptors in vivo and in vitro

The pathogenesis of chagasic cardiomyopathy is not completely understood, but it has been correlated with parasympathetic denervation (neurogenic theory) and inflammatory activity (immunogenic theory) that could affect heart muscarinic acetylcholine receptor (mAChR) expression. In order to further understand whether neurogenic and/or immunogenic alterations are related to changes in mAChR expression, we studied two models of Trypanosoma cruzi infection: 1) in 3-week-old male Sprague Dawley rats chronically infected with T. cruzi and 2) isolated primary cardiomyocytes co-cultured with T. cruzi and peripheral blood mononuclear cells (PBMC). Using [³H]-quinuclidinylbenzilate ([³H]-QNB) binding assays, we evaluated mAChR expression in homogenates from selected cardiac regions, PBMC, and cultured cardiomyocytes. We also determined in vitro protein expression and pro-inflammatory cytokine expression in serum and cell culture medium by ELISA. Our results showed that: 1) mAChR were significantly (P < 0.05) up-regulated in right ventricular myocardium (means ± SEM; control: 58.69 ± 5.54, N = 29; Chagas: 72.29 ± 5.79 fmol/mg, N = 34) and PBMC (control: 12.88 ± 2.45, N = 18; Chagas: 20.22 ± 1.82 fmol/mg, N = 19), as well as in cardiomyocyte transmembranes cultured with either PBMC/T. cruzi co-cultures (control: 24.33 ± 3.83; Chagas: 43.62 ± 5.08 fmol/mg, N = 7 for both) or their conditioned medium (control: 37.84 ± 3.84, N = 4; Chagas: 54.38 ± 6.28 fmol/mg, N = 20); 2) [³H]-leucine uptake was increased in cardiomyocytes co-cultured with PBMC/T. cruzi-conditioned medium (Chagas: 21,030 ± 2321; control 10,940 ± 2385 dpm, N = 7 for both; P < 0.05); 3) plasma IL-6 was increased in chagasic rats, IL-1β, was increased in both plasma of chagasic rats and in the culture medium, and TNF-α level was decreased in the culture medium. In conclusion, our results suggest that cytokines are involved in the up-regulation of mAChR in chronic Chagas disease.

Meditationes sancti evangelii 82

Invokaatio: Deo duce.

L-histidine reduces inhibitory avoidance in Carassius auratus submitted to cerebellar ablation

The effect of post-training treatment with L-histidine (LH) on the memory consolidation of inhibitory avoidance was investigated in Carassius auratus submitted to cerebellar ablation. The inhibitory avoidance procedure included 3 days: one habituation day, one training day (5 trials, T1-T5) and one test day. On the training day, each fish was placed individually in a white compartment separated from a black compartment by a sliding door. When the fish crossed into the black compartment, a weight was dropped in front of it (aversive stimulus) and the time to cross was recorded. Saline or LH (100 mg/kg) was injected intraperitoneally 10 min after the trials. Data were log10 transformed and analyzed by ANOVA and the Student-Newman-Keuls test (P < 0.05). In T5, all groups [ablation/LH (N = 15; 189.60 ± 32.52), ablation/saline (N = 14; 204.29 ± 28.95), sham/LH (N = 14; 232.36 ± 28.15), and sham/saline (N = 15; 249.07 ± 25.82)] had similar latencies that were significantly higher than T1 latencies [ablation/LH (89.33 ± 20.41), ablation/saline (97.00 ± 25.16), sham/LH (73.86 ± 18.42), and sham/saline (56.71 ± 17.59)], suggesting acquisition of inhibitory avoidance. For the test, there was a significant reduction in latencies of ablation/LH (61.53 ± 17.70) and sham/saline (52.79 ± 25.37) groups compared to the ablation/saline (213.64 ± 29.57) and sham/LH (199.43 ± 24.48) groups, showing that cerebellum ablation facilitated retention of inhibitory avoidance and LH reversed the effect of ablation. The results support other evidence that LH impairs memory consolidation and/or reduces the interpretation of aversion value.

Visual communication stimulates reproduction in Nile tilapia, Oreochromis niloticus (L.)

Reproductive fish behavior is affected by male-female interactions that stimulate physiological responses such as hormonal release and gonad development. During male-female interactions, visual and chemical communication can modulate fish reproduction. The aim of the present study was to test the effect of visual and chemical male-female interaction on the gonad development and reproductive behavior of the cichlid fish Nile tilapia, Oreochromis niloticus (L.). Fifty-six pairs were studied after being maintained for 5 days under one of the four conditions (N = 14 for each condition): 1) visual contact (V); 2) chemical contact (Ch); 3) chemical and visual contact (Ch+V); 4) no sensory contact (Iso) - males and females isolated. We compared the reproductive behavior (nesting, courtship and spawning) and gonadosomatic index (GSI) of pairs of fish under all four conditions. Visual communication enhanced the frequency of courtship in males (mean ± SEM; V: 24.79 ± 3.30, Ch+V: 20.74 ± 3.09, Ch: 0.1 ± 0.07, Iso: 4.68 ± 1.26 events/30 min; P < 0.05, two-way ANOVA with LSD post hoc test), induced spawning in females (3 spawning in V and also 3 in Ch+V condition), and increased GSI in males (mean ± SEM; V: 1.39 ± 0.08, Ch+V: 1.21 ± 0.08, Ch: 1.04 ± 0.07, Iso: 0.82 ± 0.07%; P < 0.05, two-way ANOVA with LSD post hoc test). Chemical communication did not affect the reproductive behavior of pairs nor did it enhance the effects of visual contact. Therefore, male-female visual communication is an effective cue, which stimulates reproduction among pairs of Nile tilapia.

Method for automatic detection of wheezing in lung sounds

The present report describes the development of a technique for automatic wheezing recognition in digitally recorded lung sounds. This method is based on the extraction and processing of spectral information from the respiratory cycle and the use of these data for user feedback and automatic recognition. The respiratory cycle is first pre-processed, in order to normalize its spectral information, and its spectrogram is then computed. After this procedure, the spectrogram image is processed by a two-dimensional convolution filter and a half-threshold in order to increase the contrast and isolate its highest amplitude components, respectively. Thus, in order to generate more compressed data to automatic recognition, the spectral projection from the processed spectrogram is computed and stored as an array. The higher magnitude values of the array and its respective spectral values are then located and used as inputs to a multi-layer perceptron artificial neural network, which results an automatic indication about the presence of wheezes. For validation of the methodology, lung sounds recorded from three different repositories were used. The results show that the proposed technique achieves 84.82% accuracy in the detection of wheezing for an isolated respiratory cycle and 92.86% accuracy for the detection of wheezes when detection is carried out using groups of respiratory cycles obtained from the same person. Also, the system presents the original recorded sound and the post-processed spectrogram image for the user to draw his own conclusions from the data.

Effect of frequency of static stretching on flexibility, hamstring tightness and electromyographic activity

We compared the effect of the number of weekly repetitions of a static stretching program on the flexibility, hamstring tightness and electromyographic activity of the hamstring and of the triceps surae muscles. Thirty-one healthy subjects with hamstring tightness, defined as the inability to perform total knee extension, and shortened triceps surae, defined by a tibiotarsal angle wider than 90° during trunk flexion, were divided into three groups: G1 performed the stretching exercises once a week; G2, three times a week, and G3, five times a week. The parameters were determined before and after the stretching program. Flexibility improved in all groups after intervention, from 7.65 ± 10.38 to 3.67 ± 12.08 in G1, from 10.73 ± 12.07 to 0.77 ± 10.45 in G2, and from 14.20 ± 10.75 to 6.85 ± 12.19 cm in G3 (P < 0.05 for all comparisons). The increase in flexibility was higher in G2 than in G1 (P = 0.018), while G2 and G3 showed no significant difference (G1: 4 ± 2.17, G2: 10 ± 5.27; G3: 7.5 ± 4.77 cm). Hamstring tightness improved in all groups, from 37.90 ± 6.44 to 29 ± 11.65 in G1, from 39.82 ± 9.63 to 21.91 ± 8.40 in G2, and from 37.20 ± 6.63 to 26.10 ± 5.72° in G3 (P < 0.05 for all comparisons). During stretching, a statistically significant difference was observed in electromyographic activity of biceps femoris muscle between G1 and G3 (P = 0.048) and G2 and G3 (P = 0.0009). No significant differences were found in electromyographic activity during maximal isometric contraction. Stretching exercises performed three times a week were sufficient to improve flexibility and range of motion compared to subjects exercising once a week, with results similar to those of subjects who exercised five times a week.

Effect of metabolic syndrome and of its individual components on renal function of patients with type 2 diabetes mellitus

The objective of this study was to evaluate the effect of metabolic syndrome (MetS) and its individual components on the renal function of patients with type 2 diabetes mellitus (DM). A cross-sectional study was performed in 842 type 2 DM patients. A clinical and laboratory evaluation, including estimated glomerular filtration rate (eGFR) calculated by the modification of diet in renal disease formula, was performed. MetS was defined according to National Cholesterol Education Program - Adult Treatment Panel III criteria. Mean patient age was 57.9 ± 10.1 years and 313 (37.2%) patients were males. MetS was detected in 662 (78.6%) patients. A progressive reduction in eGFR was observed as the number of individual MetS components increased (one: 98.2 ± 30.8; two: 92.9 ± 28.1; three: 84.0 ± 25.1; four: 83.8 ± 28.5, and five: 79.0 ± 23.0; P < 0.001). MetS increased the risk for low eGFR (<60 mL·min-1·1.73 (m²)-1) 2.82-fold (95%CI = 1.55-5.12, P < 0.001). Hypertension (OR = 2.2, 95%CI = 1.39-3.49, P = 0.001) and hypertriglyceridemia (OR = 1.62, 95%CI = 1.19-2.20, P = 0.002) were the individual components with the strongest associations with low eGFR. In conclusion, there is an association between MetS and the reduction of eGFR in patients with type 2 DM, with hypertension and hypertriglyceridemia being the most important contributors in this sample. Interventional studies should be conducted to determine if treatment of MetS can prevent renal failure in type 2 DM patients.

Theoremata nonnulla miscellanea (1685-03-07)

Variantti B.