Perturbed quantization steganography

In this paper, we use the recently proposed wet paper codes and introduce a new approach to passive-warden steganography called perturbed quantization. In perturbed quantization, the sender hides data while processing the cover object with an information-reducing operation that involves quantization, such as lossy compression, downsampling, or A/D conversion. The unquantized values of the processed cover object are considered as side information to confine the embedding changes to those unquantized elements whose values are close to the middle of quantization intervals. This choice of the selection channel calls for wet paper codes as they enable communication with non-shared selection channel. Heuristic is presented that indicates that the proposed method provides better steganographic security than current JPEG steganographic methods. This claim is further supported by blind steganalysis of a specific case of perturbed quantization for recompressed JPEG images.     

Digital camera identification from sensor pattern noise

In this paper, we propose a new method for the problem of digital camera identification from its images based on the sensor's pattern noise. For each camera under investigation, we first determine its reference pattern noise, which serves as a unique identification fingerprint. This is achieved by averaging the noise obtained from multiple images using a denoising filter. To identify the camera from a given image, we consider the reference pattern noise as a spread-spectrum watermark, whose presence in the image is established by using a correlation detector. Experiments on approximately 320 images taken with nine consumer digital cameras are used to estimate false alarm rates and false rejection rates. Additionally, we study how the error rates change with common image processing, such as JPEG compression or gamma correction.     

A bit-level systolic array for digital contour smoothing

Linear operators for digital contour smoothing are described. These operators are defined by circulant Toeplitz matrices and allow to smooth digital contours in the least-squares sense. They minimize the undersampling, digitizing and quantizing error and allow to calculate invariants, such as curvature, which are not possible to calculate without smoothing. A bit-level systolic array which is capable of realizing the proposed operator is described. This array is easy to implement in VLSI, because the array cells involved are very simple. Furthermore, the array is completely pipelined on the bit-level, so that it operates with a high clock frequency achieving very high throughputs.     

Myocardial perfusion scintigraphy and radionuclide angiography for the evaluation of outpatients with suspected coronary disease

Combined ECG/myocardial perfusion szintigraphy (MPS) exercise tests were performed in 82 out-patients with suspected CAD who eventually underwent left heart catheterization. The sensitivity of MPS as compared to ECG was higher in patients with angina (86% vs. 67%) as well as in patients with atypical symptoms (63% vs. 25%). Here MPS was also more specific than ECG (86% vs. 68%). Combination of both tests improved sensitivity even more. The comparison of radionuclide and contrast ventriculography in 20 patients studied at rest revealed an excellent correlation (r = 0.90). Changes in radionuclide ejection fraction during exercise in 60 subjects showed significant differences between normals (increase of greater than 10% above resting level) and patients with CAD (decrease in patients with angina, no significant change without angina). Methods and indications are briefly discussed in the light of this experience.     

Digital image forensics

This tutorial explains how photo-response nonuniformity (PRNU) of imaging sensors can be used for a variety of important digital forensic tasks, such as device identification, device linking, recovery of processing history, and detection of digital forgeries. The PRNU is an intrinsic property of all digital imaging sensors due to slight variations among individual pixels in their ability to convert photons to electrons. Consequently, every sensor casts a weak noise-like pattern onto every image it takes. This pattern, which plays the role of a sensor fingerprint, is essentially an unintentional stochastic spread-spectrum watermark that survives processing, such as lossy compression or filtering. This tutorial explains how this fingerprint can be estimated from images taken by the camera and later detected in a given image to establish image origin and integrity. Various forensic tasks are formulated as a two-channel hypothesis testing problem approached using the generalized likelihood ratio test. The performance of the introduced forensic methods is briefly illustrated on examples to give the reader a sense of the performance.     

Matrix embedding for large payloads

Matrix embedding is a previously introduced coding method that is used in steganography to improve the embedding efficiency (increase the number of bits embedded per embedding change). Higher embedding efficiency translates into better steganographic security. This gain is more important for long messages than for shorter ones because longer messages are, in general, easier to detect. In this paper, we present two new approaches to matrix embedding for large payloads suitable for practical steganographic schemes-one based on a family of codes constructed from simplex codes and the second one based on random linear codes of small dimension. The embedding efficiency of the proposed methods is evaluated with respect to theoretically achievable bounds.     

The arterial to end-tidal carbon dioxide gradient increases with uncorrected but not with temperature-corrected PaCO2 determination during mild to moderate hypothermia

End-tidal carbon dioxide (PETCO2) monitoring is recommended as a basic standard of care and is helpful in adjusting mechanical ventilation. Gas solubility changes with temperature, which might affect the PaCO2 and thereby the gradient between PaCO2 and PETCO2 (PA-ETCO2) under hypothermic conditions. We investigated whether the PA-ETCO2 changes during mild to moderate hypothermia (36 degrees C-32 degrees C) using PaCO2 measured at 37 degrees C (uncorrected PaCO2) and PaCO2 corrected to actual body temperature. We preoperatively investigated 19 patients. After anesthesia had been induced, controlled ventilation was established to maintain normocarbia using constant uncorrected PaCO2 to adjust ventilation (alpha-stat acid-base regimen). Body core temperature was reduced without surgical intervention to 32 degrees C by surface cooling. Continuous PETCO2 was monitored with a mainstream PETCO2 module. The PA-ETCO2 was calculated using the uncorrected and corrected PaCO2 values. During body temperature reduction from 36 degrees C to 32 degrees C, the gradient between PETCO2 and uncorrected PaCO2 increased 2.5-fold, from 4.1 +/- 3.7 to 10.4 +/- 3.8 mm Hg (P < 0.002). The PA-ETCO2 remained unchanged when the corrected PaCO2 was used for the calculation. We conclude that when the alpha-stat acid-base regimen is used to adjust ventilation, the PA-ETCO2 calculated with the uncorrected PaCO2 increases and should be added to the differential diagnosis of widened PA-ETCO2. In contrast, when the corrected PaCO2 is used for the calculation of the PA-ETCO2, the PA-ETCO2 remains unaltered during hypothermia. Implications: We investigated the impact of induced hypothermia (36 degrees C-32 degrees C) on the gradient between PaCO2 and PETCO2 (PA-ETCO2). The PA-ETCO2 increased 2.5-fold when CO2 determinations were not temperature-corrected. Hypothermia should be added to the differential diagnosis of an increased PA-ETCO2 when the alpha-stat acid-base regimen is used.     

Safety and efficacy of increasing dosages of glycyl-glutamine for total parenteral nutrition in polytrauma patients

Supplementation of parenteral nutrition with glutamine (GLN) has been suggested to improve the efficacy of nutritional support by stimulating protein synthesis and improving immunocompetence. In the present study we investigated the impact of infusing the dipeptide glycyl-glutamine (GLY-GLN) at increasing dosages on plasma amino acid concentrations in patients with polytrauma. Nine polytraumatized patients were randomly assigned according their age and their trauma score to three experimental groups. Group 1 received 280, group II 450, and group III 570 mg GLY-GLN per kg body weight/day for a period of four days (3rd to 7th posttraumatic day), resulting in a maximum daily GLN administration (calculated for a 70 kg patient) of 14 g, 21 g and 28 g, respectively. Seven polytraumatized patients receiving the nutrition solution without GLY-GLN supplementation served as controls. All patients received total parenteral nutrition with an average amino acid administration of 1.1 g/kg/day and a total energy intake of 30 kcal/kg/day. GLY-GLN infusion did not evoke any side effects. In comparison with the control group, arterial plasma GLN concentrations increased significantly on day I after start of infusion in groups II and III, but remained raised throughout the study period only in group III (p < 0.003). Similarly, plasma GLY concentrations were also significantly raised in group III (p < 0.04). The maximum increase of plasma GLY was found on the second infusion day, after which plasma concentrations of GLY fell to concentrations even below those observed in the control group at the end of the study period. Excretion of GLY-GLN, GLN or GLY in the urine during the GLY-GLN infusions was negligible. We conclude from this first available dose finding study on glutamine-containing dipeptides that in polytraumatized patients infusion of 570 mg/kg/day of GLY-GLN (corresponding to 28 g glutamine or 40 g dipeptide/70 kg, respectively) is necessary to induce a sustained effect on plasma glutamine concentrations. No pathological accumulation of free glycine or of the dipeptide was seen with any of the three dosage steps of GLY-GLN. Thus, the administration of even high doses of GLY-GLN is feasible and safe in patients with polytrauma and is not associated with any relevant renal substrate loss.     

Effects of growth hormone (GH) replacement on bone metabolism and mineral density in adult onset of GH deficiency: results of a double-blind placebo-controlled study with open follow-up

It is known that GH stimulates bone turnover and that GH-deficient adults have a lower bone mass than healthy controls. In order to evaluate the influences of GH replacement therapy on markers of bone turnover and on bone mineral density (BMD) in patients with adult onset GH deficiency, a double-blind placebo-controlled study of treatment with recombinant human GH (rhGH; mean dose 2.4 IU daily) in 20 patients for 6 months and an extended open study of 6 to 12 months were conducted. Eighteen patients, fourteen men and four women, with a mean age of 44 years with adult onset GH deficiency were evaluated in the study. Compared with placebo, after 6 months serum calcium (2.39 +/- 0.02 vs 2.32 +/- 0.02 mmol/l, P = 0.037) and phosphate (0.97 +/- 0.06 vs 0.75 +/- 0.05 mmol/l, P = 0.011) increased and the index of phosphate excretion (0.03 +/- 0.03 vs 0.19 +/- 0.02, P < 0.001) decreased significantly, and there was a significant increase in the markers of bone formation (osteocalcin, 64.8 +/- 11.8 vs 17.4 +/- 1.8 ng/ml, P < 0.001; procollagen type I carboxyterminal propeptide (PICP), 195.3 +/- 26.4 vs 124.0 +/- 15.5 ng/ml, P = 0.026) as well as those of bone resorption (type I collagen carboxyterminal telopeptide (ICTP), 8.9 +/- 1.2 vs 3.3 +/- 0.5 ng/ml, P < 0.001; urinary hydroxyproline, 0.035 +/- 0.006 vs 0.018 +/- 0.002 mg/100 ml glomerular filtration rate, P = 0.009). BMD did not change during this period of time. IGF-I was significantly higher in treated patients (306 +/- 45.3 vs 88.7 +/- 22.5 ng/ml, P < 0.001). An analysis of the data compiled from 18 patients treated with rhGH for 12 months revealed similar significant increases in serum calcium and phosphate, and the markers of bone turnover (osteocalcin, PICP, ICTP, urinary hydroxyproline). Dual energy x-ray absorptiometry (DXA)-measured BMD in the lumbar spine (1.194 +/- 0.058 vs 1.133 +/- 0.046 g/cm2, P = 0.015), femoral neck (1.009 +/- 0.051 vs 0.936 +/- 0.034 g/cm2, P = 0.004), Ward's triangle (0.881 +/- 0.055 vs 0.816 +/- 0.04 g/cm2, P = 0.019) and the trochanteric region (0.869 +/- 0.046 vs 0.801 +/- 0.033 g/cm2, P = 0.005) increased significantly linearly (compared with the individual baseline values). At 12 months, BMD in patients with low bone mass (T-score < -1.0 S.D.) increased more than in those with normal bone mass (lumbar spine 11.5 vs 2.1%, P = 0.030, and femoral neck 9.7 vs 4.2%, P = 0.055). IGF-I increased significantly in all treated patients. In conclusion, treatment of GH-deficient adults with rhGH increases bone turnover for at least 12 months. BMD in the lumbar spine and the proximal femur increases continuously in this time (open study) and the benefit is greater in patients with low bone mass. Therefore, GH-deficient patients exhibiting osteopenia or osteoporosis should be considered candidates for GH supplementation. However, long-term studies are needed to establish that the positive effects on BMD are persistent and are associated with a reduction in fracture risk.