| 1. |
- Falk, Kristina, 1972, et al.
(författare)
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Antifibrinolytic proCPU is present in the peritoneal cavity during surgery.
- 2003
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Ingår i: Scandinavian journal of clinical and laboratory investigation. - 0036-5513. ; 63:4, s. 287-96
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Tidskriftsartikel (refereegranskat)abstract
- The fibrinolytic capacity of the peritoneum plays a pivotal role in peritoneal wound healing. During surgery the balance between fibrin deposition and degradation is tilted towards deposition, leading to the formation of adhesions. In blood, carboxypeptidase U (CPU) stabilizes clots by retarding fibrinolysis. The purpose of this study was to investigate whether the more stable zymogen, proCPU, is also present in the peritoneal cavity and, if so, to examine its origin. Levels of proCPU were measured in plasma and serosal peritoneal fluid collected during surgery. Peritoneal biopsies were stained for proCPU. Two-dimensional gel electrophoresis was performed to study the protein composition of the serosal fluid compared to plasma and Western blotting to identify differences in glycosylation of proCPU, indicating possible different cellular origin. Cultured human mesothelial cells were examined for proCPU production under normal conditions and conditions mimicking surgery. We found comparable and correlating levels of proCPU in serosal fluid and plasma. ProCPU was also found where fibrin covered the injured peritoneal surface. A protein composition very similar in serosal fluid and plasma was shown by two-dimensional gel electrophoresis, and the proCPU pattern did not indicate a different origin. No proCPU production was found in cultured mesothelial cells. This is the first study to report on the presence of proCPU in the peritoneal cavity, which seems to be the result of plasma oozing out during the inflammatory reaction to the surgical trauma. This is likely to be important for the balance between fibrin deposition and degradation and thereby in the formation of postoperative adhesions.
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| 2. |
- Ahnström, Ulrika, et al.
(författare)
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Detection and direction-finding of spread spectrum signals using correlation and narrowband interference rejection
- 2003
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Ingår i: Nordic Matlab Conference 2003.
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Konferensbidrag (refereegranskat)abstract
- An algorithm for correlation-based detection of direct sequence spread spectrum signals with direction finding, including direction-filtering and narrow-band interference rejection, is implemented and evaluated in MATLAB. An analog noise-free signal is generated and sampled by a test-bed system. Numerical simulations are run based on data corrupted by mutually uncorrelated white Gaussian noise sequences, and also with recorded noise from two spatially separated HF radio receivers. The simulations and measurements show promising results for detection and direction-finding of covert wideband signals in low SNR and in presence of narrowband interferers. Direction filtering is shown to improve the results.
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| 3. |
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| 4. |
- Falk, Johan, et al.
(författare)
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Direction Finding for Electronic Warfare Systems Using the Phase of the Cross Spectral Density
- 2002
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Ingår i: RadioVetenskap och Kommunikation (RVK). ; , s. 264-268
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Konferensbidrag (refereegranskat)abstract
- In modern electronic warfare systems there is a need for direction-finding of transmitters using waveforms for military stealth communication. In this paper, a correlation-based method is investigated utilizing the phase of the cross spectral density to estimate the time-difference-of-arrival from a two-channel digital receiver. A least squares method is reviewed, and its performance is investigated by theoretical analysisand by Monte-Carlo simulations. Proper Cramér-Raobounds are derived. It is shown that the method is statistically efficient for flat spectrum signals. The method is found to be a promising method for use against military communication in an electronic warfare direction-finding system.
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| 5. |
- Falk, Johan, et al.
(författare)
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Effects of frequency and phase error in electronic warfare TDOA direction-finding systems
- 2003
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Ingår i: Military Communications Conference. - : IEEE conference proceedings. - 0780381408 ; , s. 118-123
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Konferensbidrag (refereegranskat)abstract
- Electronic warfare systems for use against military communication sources include direction-finding. The considered direction-finding electronic-warfare system usestwo intercept receivers which is eavesdropping on thetransmitted signal with no knowledge of the waveformused, or its origin. Down-conversion to baseband is required in order to digitize the received signal. This canbe done using a superheterodyne receiver where an oscillator is used to mix the signal-of-interest to baseband.Errors in frequency and phase between the oscillatorsdegrade the performance. Because of this error, the per-formance derived in previous work by the authors willnot apply since the used model no longer is applicable.The extended model presented here considers the oscil-lator errors. The performance using the extended modelis determined numerically and the result is compared tothe Cramer-Rao lower bound for the ideal system usinga typical signal waveform.
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| 6. |
- Falk, J., et al.
(författare)
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Estimation of receiver frequency error in a TDOA-based direction-finding system
- 2004
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Ingår i: Conference Record - Asilomar Conference on Signals, Systems and Computers. ; , s. 2079-2083
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Konferensbidrag (refereegranskat)abstract
- Direction-finding of radio transmitters is considered and in particular correlation-based time-difference-of-arrival (TDOA) estimation between a pair of intercept receivers. In the target application, the received and down-converted signals are corrupted by a frequency error due to a receiver frequency tuning offset which degrades the performance of the TDOA estimation. Traditionally, the cross-ambiguity function (CAP) is used in a 2D scheme for joint TDOA and frequency error estimation. In this paper, sequential ID frequency error and TDOA estimators are introduced and compared to the 2D method. The 2D method attains the CRLB for both the TDOA and frequency error estimates, but have high computational and memory complexity. The proposed frequency error estimator is outperformed by the 2D method. However, the main objective is to estimate the TDOA and the proposed TDOA estimator have a performance similar to that of the 2D method. The main advantage of the proposed method is a reduction in both computational and memory complexity.
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| 7. |
- Falk, Johan, et al.
(författare)
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Multisource time delay estimation subject to receiver frequency errors
- 2003
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Ingår i: CONFERENCE RECORD OF THE THIRTY-SEVENTH ASILOMAR CONFERENCE ON SIGNALS, SYSTEMS & COMPUTERS, VOLS 1 AND 2. - 0780381041 ; , s. 1156-1160
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Konferensbidrag (refereegranskat)abstract
- An electronic warfare (EW) system with two spatially separated intercept receivers, targeting military communication systems is considered. The EW system estimates the direct ion-of-arrival via a correlation-based time-difference-of-arrival (TDOA) method without any prior knowledge of the signals-of-interest. An important practical consideration is the oscillator frequencies of the two intercept receivers where a difference, or error, degrades the TDOA estimator performance. A measure of this degradation, or loss in power due to the frequency error, is derived and used to describe the robustness against receiver frequency errors. In the multisource scenario, time and frequency overlapping sources can be separated using direction-filtering of the cross-correlation function between the receiver outputs with good result if one signal at a time can be selected by the direction-filter. However, the performance of the considered estimator is degraded in a multisource scenario compared to the single source case.
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| 8. |
- Falk, Peter, 1962, et al.
(författare)
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Differential regulation of mesothelial cell fibrinolysis by transforming growth factor beta 1.
- 2000
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Ingår i: Scandinavian journal of clinical and laboratory investigation. - 0036-5513. ; 60:6, s. 439-47
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Tidskriftsartikel (refereegranskat)abstract
- Inflammation and tissue trauma during the surgical procedure reduce the peritoneal fibrinolytic capacity. These conditions promote adhesion formation, and are associated with increased expression of transforming growth factor beta 1 (TGF-beta1). The objective of the present study was to investigate whether TGF-beta1 regulates the expression of fibrinolytic components in peritoneal mesothelial cells. Human peritoneal mesothelial cells (HPMC) were cultured and treated with various concentrations of human recombinant TGF-beta1 (0.1, 1.0 and 10 ng/mL) for 24 h. Levels of tissue- and urokinase plasminogen activator (t-PA and uPA), plasminogen activator inhibitor type-1 (PAI-1) and type-2 (PAI-2) mRNA and protein were assessed by quantitative reverse transcriptase polymerase chain reaction (Q-RT-PCR) and ELISA, respectively. HPMC expressed these components at the gene and protein level. TGF-beta1 downregulated, dose-dependently t-PA mRNA and protein to about 50% of control values (p = 0.0010), and doubled PAI-1 protein production (p = 0.0008) compared to untreated controls. Although uPA gene expression increased in cells exposed to TGF-beta1, the corresponding protein concentration in conditioned media did not. PAI-2 was not affected, either at the gene or protein level. In conclusion, the results indicate that fibrinolytic capacity of mesothelial cells is reduced by TGF-beta1, suggesting that peritoneal adhesion formation induced by TGF-beta1 may be mediated, in part, through reduction in fibrin degradation capacity at an early stage of peritoneal tissue repair.
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| 9. |
- Falk, Peter, 1962, et al.
(författare)
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Examination gloves affect secretion of matrix metalloproteinases and their inhibitors from human abdominal skin fibroblasts.
- 2003
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Ingår i: Wound repair and regeneration : official publication of the Wound Healing Society [and] the European Tissue Repair Society. - 1067-1927. ; 11:3, s. 230-4
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Tidskriftsartikel (refereegranskat)abstract
- Overexpression of matrix metalloproteinases (MMPs) has been observed in chronic, compared to acute, wounds and altered levels might impair healing. During treatment of wounds, examination gloves are routinely used, and the wound environment thus gets exposed to gloves. The aim of this study was to characterize secretion of MMPs and tissue inhibitors of metalloproteinases (TIMPs) in cultured fibroblasts with or without exposure to gloves. Cultures were exposed to glove washings from powdered or powder-free latex examination gloves and compared to untreated controls. MMP-1, -2, -3, -9 and their inhibitors TIMP-1 and -2 were assayed in conditioned media. Cells exposed to gloves reduced their release of MMP-1, -2, and -3 with no differences between the manufacturers of the gloves. The inhibitor TIMP-1 was reduced to 10-15% of untreated control values (p < 0.001), being less affected by the powder-free than by the powdered glove (p < 0.05). MMP-9 and TIMP-2 were not significantly altered. We therefore conclude that secretion of MMPs and TIMPs from cultured fibroblasts were affected by glove washings. Powdered and powder-free gloves had similar effects, except for a less pronounced reduction of TIMP-1 production by the powder-free glove. Examination gloves might therefore affect wound healing, with the least pronounced effect observed using the powder-free glove.
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| 10. |
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