Post-COVID-19 Brain [18F] FDG-PET Findings: A Retrospective Single-Center Study in the United States.

BACKGROUND AND PURPOSE: The pathophysiology of neurologic manifestations of postacute sequelae of Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2) infection is not clearly understood. Our aim was to investigate brain metabolic activity on [18F] FDG-PET/CT scans in patients with a history of coronavirus disease 2019 (COVID-19) infection before imaging. MATERIALS AND METHODS: This retrospective study included 45 patients who underwent [18F] FDG-PET/CT imaging for any reason and had, at least once, tested positive for COVID-19 at any time before imaging. Fifteen patients had available [18F] FDG-PET scans obtained under identical conditions before the infection. A group of 52 patients with melanoma or multiple myeloma who underwent [18F] FDG-PET/CT were used as controls. Whole-brain 2-sample t test analysis was performed using SPM software to identify clusters of hypo- and hypermetabolism and compare brain metabolic activity between patients with COVID-19 and controls. Paired sample t test comparison was also performed for 15 patients, and correlations between metabolic values of clusters and clinical data were measured. RESULTS: Compared with the control group, patients with a history of COVID-19 infection exhibited focal areas of hypometabolism in the bilateral frontal, parietal, occipital, and posterior temporal lobes and cerebellum (P = .05 uncorrected at the voxel level, family-wise error-corrected at the cluster level) that peaked during the first 2 months, improved to near-complete recovery around 6 months, and disappeared at 12 months. Hypermetabolism involving the brainstem, cerebellum, limbic structures, frontal cortex, and periventricular white matter was observed only at 2-6 months after infection. Older age, neurologic symptoms, and worse disease severity scores positively correlated with the metabolic changes. CONCLUSIONS: This study demonstrates a profile of time-dependent brain PET hypo- and hypermetabolism in patients with confirmed SARS-CoV-2 infection.

Demographics, laboratory parameters and outcomes of 1061 patients with coronavirus disease 2019: a report from Tehran, Iran.

We aimed to determine the characteristics of coronavirus disease 2019 (COVID-2019) among the Iranian population. In this study, we collected and analysed the demographics, laboratory findings and outcomes of patients with COVID-19 who were admitted to Masih Daneshvari Hospital in Tehran, Iran between 20 February 2020 and 2 April 2020. Among 1061 patients, 692 (65.2%) were male and the median age was 55 years (interquartile range (IQR), 44-66 years). Totally, 129 (12.2%) patients died during hospitalization in the ward or intensive care unit. From the remaining 932 individuals, 46 (5.0%) were admitted to the intensive care unit and 886 (95.0%) were hospitalized in the ward. Those patients who died were significantly older than those hospitalized in the ward (p < 0.001). The median absolute number of lymphocytes was 1.2 × 103/µL (IQR 0.9 × 103 to 1.6 × 103/µL) and 708 (66.7%) patients had lymphopenia (absolute lymphocyte count <1500/µL). Among the laboratory tests, D-dimer, serum ferritin and albumin had the strongest correlations with mortality (r = 0.455, r = 0.412, r = -0.406, respectively; p < 0.001 for each one). In conclusion, laboratory findings could provide useful information with regard to the management of individuals with COVID-19.

Automatic brain tissue segmentation in fetal MRI using convolutional neural networks.

MR images of fetuses allow clinicians to detect brain abnormalities in an early stage of development. The cornerstone of volumetric and morphologic analysis in fetal MRI is segmentation of the fetal brain into different tissue classes. Manual segmentation is cumbersome and time consuming, hence automatic segmentation could substantially simplify the procedure. However, automatic brain tissue segmentation in these scans is challenging owing to artifacts including intensity inhomogeneity, caused in particular by spontaneous fetal movements during the scan. Unlike methods that estimate the bias field to remove intensity inhomogeneity as a preprocessing step to segmentation, we propose to perform segmentation using a convolutional neural network that exploits images with synthetically introduced intensity inhomogeneity as data augmentation. The method first uses a CNN to extract the intracranial volume. Thereafter, another CNN with the same architecture is employed to segment the extracted volume into seven brain tissue classes: cerebellum, basal ganglia and thalami, ventricular cerebrospinal fluid, white matter, brain stem, cortical gray matter and extracerebral cerebrospinal fluid. To make the method applicable to slices showing intensity inhomogeneity artifacts, the training data was augmented by applying a combination of linear gradients with random offsets and orientations to image slices without artifacts. To evaluate the performance of the method, Dice coefficient (DC) and Mean surface distance (MSD) per tissue class were computed between automatic and manual expert annotations. When the training data was enriched by simulated intensity inhomogeneity artifacts, the average achieved DC over all tissue classes and images increased from 0.77 to 0.88, and MSD decreased from 0.78 mm to 0.37 mm. These results demonstrate that the proposed approach can potentially replace or complement preprocessing steps, such as bias field corrections, and thereby improve the segmentation performance.

Brain and CSF Volumes in Fetuses and Neonates with Antenatal Diagnosis of Critical Congenital Heart Disease: A Longitudinal MRI Study.

BACKGROUND AND PURPOSE: Fetuses and neonates with critical congenital heart disease are at risk of delayed brain development and neurodevelopmental impairments. Our aim was to investigate the association between fetal and neonatal brain volumes and neonatal brain injury in a longitudinally scanned cohort with an antenatal diagnosis of critical congenital heart disease and to relate fetal and neonatal brain volumes to postmenstrual age and type of congenital heart disease. MATERIALS AND METHODS: This was a prospective, longitudinal study including 61 neonates with critical congenital heart disease undergoing surgery with cardiopulmonary bypass <30 days after birth and MR imaging of the brain; antenatally (33 weeks postmenstrual age), neonatal preoperatively (first week), and postoperatively (7 days postoperatively). Twenty-six had 3 MR imaging scans; 61 had at least 1 fetal and/or neonatal MR imaging scan. Volumes (cubic centimeters) were calculated for total brain volume, unmyelinated white matter, cortical gray matter, cerebellum, extracerebral CSF, and ventricular CSF. MR images were reviewed for ischemic brain injury. RESULTS: Total fetal brain volume, cortical gray matter, and unmyelinated white matter positively correlated with preoperative neonatal total brain volume, cortical gray matter, and unmyelinated white matter (r = 0.5-0.58); fetal ventricular CSF and extracerebral CSF correlated with neonatal ventricular CSF and extracerebral CSF (r = 0.64 and 0.82). Fetal cortical gray matter, unmyelinated white matter, and the cerebellum were negatively correlated with neonatal ischemic injury (r = -0.46 to -0.41); fetal extracerebral CSF and ventricular CSF were positively correlated with neonatal ischemic injury (r = 0.40 and 0.23). Unmyelinated white matter:total brain volume ratio decreased with increasing postmenstrual age, with a parallel increase of cortical gray matter:total brain volume and cerebellum:total brain volume. Fetal ventricular CSF:intracranial volume and extracerebral CSF:intracranial volume ratios decreased with increasing postmenstrual age; however, neonatal ventricular CSF:intracranial volume and extracerebral CSF:intracranial volume ratios increased with postmenstrual age. CONCLUSIONS: This study reveals that fetal brain volumes relate to neonatal brain volumes in critical congenital heart disease, with a negative correlation between fetal brain volumes and neonatal ischemic injury. Fetal brain imaging has the potential to provide early neurologic biomarkers.

An interlocked flexible piezoresistive sensor with 3D micropyramidal structures for electronic skin applications.

The development of flexible pressure sensors with human-like sensing capabilities is an emerging field due to their wide range of applications from human robot interactions to wearable electronics. Piezoresistive sensors respond to externally induced mechanical stimuli through changes in their electrical resistance. The current state-of-the-art piezoresistive sensors are mainly constructed via dispersion of conductive nanofillers in an elastomer matrix making their performance strongly reliable on the degree of dispersion. Alternatively, changes in the contact area of conductive elastomers result in higher sensitivity and more tunable variables. Herein, an interlocked sensor comprising two flexible layers of 3D pyramidal microstructures is fabricated with a thin layer of carbon nanotubes deposited onto the micropatterns. The introduced array of micropyramids with varying height and pitch sizes allows for higher changes in the contact area upon applying an external load. The results indicate that the height and pitch of the structures together with a newly defined variable, the critical dimension, affect the sensor's sensitivity. An optimal performance is observed for minimized values of the critical dimension. Furthermore, to verify the obtained results, a finite-element-assisted analytical constriction-resistance model is used to capture the piezoresistive response of the sensor. The theoretical results show the high tracking ability of their experimental counterparts.

A constriction resistance model of conjugated polymer based piezoresistive sensors for electronic skin applications.

Human intervention can be replaced through the development of tools resulting from utilization of sensing devices possessing a wide range of applications including humanoid robots or remote and minimally invasive surgeries. Similar to the five human senses, sensors interface with their surroundings to stimulate a suitable response or action. The sense of touch which arises in human skin is among the most challenging senses to emulate due to its ultra high sensitivity. This has brought forth novel challenging issues to consider in the field of biomimetic robotics. In this work, using a multiphase reaction, a polypyrrole (PPy) based hydrogel is developed as a resistive type pressure sensor with an intrinsically elastic microstructure stemming from three dimensional hollow spheres. It is shown that the electrical conductivity of the fabricated PPy based piezoresistive sensors is enhanced as a result of adding conductive fillers and therefore, endowing the sensors with a higher sensitivity. A semi-analytical constriction resistance based model accounting for the real contact area between the PPy hydrogel sensors and the electrode along with the dependency of the contact resistance change on the applied load is developed. The model is then solved using a Monte Carlo technique and its corresponding sensitivity is obtained. Comparing the results with their experimental counterparts, the proposed modeling methodology offers a good tracking ability.

Late umbilical cord clamping, neonatal hematocrit and Apgar scores: a randomized controlled trial.

OBJECTIVE: Based on current evidence, there is a little agreement on the best timing for after birth umbilical cord clamping. This study was designed to compare the impact of using two different times for cord clamping on hematocrit concentration and Apgar scores of the neonate. STUDY DESIGN: Fifty-six healthy full-term vaginally born neonates were allocated to early (10 seconds after delivery) and late (3 minutes after delivery) umbilical cord clamping groups in this randomized clinical trial. We recorded the length of the 3rd stage of labor and Apgar score at 5 minutes. Infant's hematocrit was measured at 2 and 18 hours of age. RESULTS: Neonatal hematocrit differed between the two groups. Late cord clamping group had greater hematocrit at 2 hours (45.5 ± 4 vs. 49.5 ± 4.4, P = 0.0003) and 18 hours (47.7 ± 5.5 vs. 52.9 ± 4.3, P = 0.0002). Apgar scores at 5 minutes (9.3 ± 0.6 vs. 9.4 ± 0.6, p = 0.5) and duration of delivery 3rd stage (10.2 ± 3.7 min vs. 8.9 ± 5 min, P = 0.2) did not differ between early and late cord clamping groups respectively. CONCLUSION: Late cord clamping leads to a significant increase in the hematocrit of the neonate but it does not have effects on Apgar score and duration of the 3rd stage of labor.

The effect of acupressure on sleep quality in hemodialysis patients.

OBJECTIVE: Our purpose was to investigate the effects of acupressure on sleep quality in hemodialysis patients. DESIGN: Randomized clinical trial. SETTING: The setting of the study was dialysis wards located in two university hospitals (Imam and Golestan) in Ahvaz, Iran. INTERVENTIONS: 48 end-stage renal disease patients on hemodialysis who scored 5 points or higher on the Pittsburgh Sleep Quality Index (PSQI) were enrolled to the study. Acupressure group received acupressure intervention on the Shenmen (He7) and He Gu (Li4) points in the hands and Sanyingjao (sp6) point in the feet for 4 weeks beside routine care and control group received only routine care. MAIN OUTCOME MEASURES: subjective sleep quality, latency and duration, habitual sleep efficiency; sleep disturbances, daytime functional status, and use of sleeping medications. RESULTS: The result indicated significant differences between the acupressure group and the control group after intervention in PSQI global scores (p<0.001) and all sleep quality indices between two groups after intervention: subjective sleep quality (p<0.001), sleep latency (p<0.001), sleep duration (p<0.001), sleep efficiency (p=0.006), sleep disturbance (p<0.001), the use of sleeping medication (p=0.028), and daytime dysfunction (p<0.001). CONCLUSION: This study supports the effectiveness of acupressure in improving sleep quality of end-stage renal disease patients as a noninvasive therapy.

Hyperuricemia after renal transplantation.

BACKGROUND: Hyperuricemia is a common complication after kidney transplantation, and may adversely affect graft survival. OBJECTIVE: To assess the prevalence of and predictors for development of hyperuricemia after renal transplantation. MATERIALS AND METHODS: Hyperuricemia was defined as a serum uric acid concentration of at least 7.0 mg/dL in men and 6.0 mg/dL in women. From March 2008 to May 2010, uric acid concentration was measured in 12,767 blood samples from 2961 adult renal transplant recipients (64% male and 36% female patients). RESULTS: Hyperuricemia was observed in 1553 patients (52.4%). The disorder frequently occurred in women (P=.003) and in patients with impaired renal graft function (P=.00). After adjustment for sex, serum creatinine concentration, diabetes mellitus, cyclosporine concentration, and dyslipidemia, only female sex (P=.03) and renal allograft dysfunction (P=.05) were associated with hyperuricemia after kidney transplantation. CONCLUSION: Hyperuricemia is a common complication after kidney transplantation, and renal allograft insufficiency predisposes to higher uric acid concentration.

Hyperhomocysteinemia after kidney transplantation.

OBJECTIVE: To determine the prevalence of hyperhomocysteinemia (plasma homocysteine[Hcy] concentration≥15 µmol/L) and evaluate its correlation with allograft function. MATERIALS AND METHODS: The study included 159 stable renal transplant recipients (104 men and 55 women). The prevalence and severity of hyperhomocysteinemia were compared in the transplant recipients vs 72 patients (48 men and 24 women) receiving hemodialysis therapy. RESULTS: The mean (SD; range) fasting total Hcy concentration was higher in the hemodialysis group compared with the renal transplantation group: 27.4 (18.3; 10-95) µmol/L vs 16.6 (9.5; 4.5-45.0) µmol/L (P=.00). Hyperhomocysteinemia occurred more frequently in patients receiving hemodialysis therapy (74% vs 49%). No significant correlation was observed between Hcy concentration and recipient sex, cyclosporine trough concentration and concentration at 2 days after dosing, dyslipidemia,cytomegalovirus infection, diabetes mellitus, or aspartate or alanine aminotransferase concentration. Multivariate regression analysis revealed that serum creatinine concentration (P=.02) was the major determinant of increased total Hcy concentration in renal transplant recipients. CONCLUSION: A high prevalence of moderate hyperhomocysteinemia was observed in renal transplant recipients. There was no correlation between graft function and Hcy concentration.

The role of thyroid autoantibodies in the etiology of endemic goiter in schoolchildren of Isfahan, Iran.

BACKGROUND: Eleven years after the initiation of universal salt iodization program in Iran, the prevalence of goiter is still high in some areas. AIM: To investigate the role of thyroid autoimmunity in the etiology of residual goiter in schoolchildren of Isfahan, Iran. MATERIAL AND METHODS: In a cross-sectional study, 2331 schoolchildren were selected by multi-stage random cluster sampling. Thyroid size was estimated in each child by inspection and palpation. Urinary iodine concentration (UIC), serum anti-thyroperoxidase antibody (anti-TPO Ab), and anti-thyroglobulin antibody (Anti-Tg Ab) were measured. RESULTS: Overall, 32.9% of children had goiter. The median UIC was 1955.5 microg/dl. There was significant difference in prevalence of positive anti-TPO Ab in goitrous (grade 2) and non-goitrous children (9.7 vs 3.7%, p= 0.02). Goitrous children had higher prevalence of positive anti-Tg Ab than non-goitrous ones (15.1 vs 3.1%, p<0.001). CONCLUSIONS: According to the present study, goiter is still a public health problem in this region. This study suggests that thyroid autoimmunity is among the contributors of goiter persistence after elimination of iodine deficiency in Isfahan.

Evaluation of liposomal and conventional formulations of octyl methoxycinnamate on human percutaneous absorption using the stripping method.

The objective of this study was to determine the influence of vehicles on the penetration of octyl methoxycinnamate (OMC), as a UV absorber, to the stratum corneum by the stripping method. The experimental formulations consisted of a conventional o/w emulsion and multilamellar and small unilamellar liposomes (MLVs and SUVs) containing OMC. MLVs containing OMC were prepared by the fusion method and then converted to SUVs by probe sonication. Various formulations were then applied onto the midvolar forearms of six volunteers at a dose of 2 mg/cm2. After determined timepoints, the stripping method was conducted whereby 22 tape strips were applied and subsequently divided into different stripping groups. The sunscreen agent was assessed by HPLC while the SPF (sun protection factor) of the formulations was determined in human volunteers in accordance with the Australian standard. Overall the results indicate that skin accumulation of OMC in MLVs was significantly greater than in the o/w emulsion and SUVs. Furthermore, SUV's penetration into the deeper skin layers was significantly greater than MLV's and that of a conventional o/w emulsion. Also, higher amounts of OMC were recovered from the upper layers of the stratum corneum than from the deeper layers in all the formulations tested. Finally, the SPF of the liposomes containing OMC was slightly greater than that of the control lotions at a similar concentration of OMC. In conclusion, the result of this study indicates that an MLV prepared by the fusion method could be a better vehicle for OMC as a sunscreen since it has a slightly better SPF compared to a conventional formulation and more remains in the stratum corneum, reducing its penetration to the deeper layers.

Is spinal cord isolation a good model of muscle disuse?

The patterns of normal daily activity that are required to maintain normal skeletal muscle properties remain unknown. The present study was designed to determine whether spinal cord isolation can be used as a reliable experimental model of neuromuscular inactivity, that is, as a baseline for the absence of activity. Electromyograms (EMGs) were recorded from selected hindlimb muscles of unanesthetized rats over 24-hour periods before and 7, 30, 60, and 90 days after surgical isolation of the lumbar spinal cord. Our data indicate that some rat slow muscle fibers pre-surgery were activated for less than 3 hours per day. Spinal cord isolation (SI) reduced the mean daily integrated EMG (IEMG) and daily EMG duration in the primary slow extensor muscle (soleus) to <1% of control, and in the primary fast extensor muscles [medial gastrocnemius (MG) and vastus lateralis (VL)] to <2% of control. These parameters were decreased to <8% and 3% of control, respectively, in a primary fast flexor muscle, the tibialis anterior (TA). From 30 to 90 days post-SI, the mean amplitudes of the spontaneous EMG bursts were relatively normal in the soleus, increased approximately 2-fold in the MG and VL, and increased approximately 4-fold in the TA. Some evidence of the normal antagonistic flexor-extensor relationship was apparent in the brief periods of recorded activity post-SI. These results indicate that SI eliminates nearly all of the normal EMG activity in the hindlimb muscles in the presence of relatively normal muscle innervation and functional intraspinal neural circuitry.

Individual voxel-based analysis of gray matter in focal cortical dysplasia.

High-resolution MRI of the brain has made it possible to identify focal cortical dysplasia (FCD) in an increasing number of patients. There is evidence for structural abnormalities extending beyond the visually identified FCD lesion. Voxel-based morphometry (VBM) has the potential of detecting both lesions and extra-lesional abnormalities because it performs a whole brain voxel-wise comparison. However, on T1-weighted MRI, FCD lesions are characterized by a wide spectrum of signal hyperintensity that may compromise the results of the segmentation step in VBM. Our purpose was to investigate gray matter (GM) changes in individual FCD patients using voxel-based morphometry (VBM). In addition, we sought to assess the performance of this technique for FCD detection with respect to lesion intensity using an operator designed to emphasize areas of hyperintense T1 signal. We studied 27 patients with known FCD and focal epilepsy and 39 healthy controls. We compared the GM map of each subject (controls and patients) with the average GM map of all controls and obtained a GM z-score map for each individual. The protocol being designed to achieve a maximal specificity, no differences in GM concentration were found in the control group. The z-score maps showed an increase in GM that coincided with the lesion in 21/27 (78%) patients. Five of the six remaining patients whose lesions were not detected by VBM presented with a strong lesion hyperintensity, and a significant part of their lesion was misclassified as white matter. In 16/27 (59%) patients, there were additional areas of GM increase distant from the primary lesion. Areas of GM decrease were found in 8/27 (30%) patients. In conclusion, individual voxel-based analysis was able to detect FCD in a majority of patients. Moreover, FCD was often associated with widespread GM changes extending beyond the visible lesion. In its current form, however, individual VBM may be unable to detect lesions characterized by strong signal intensity abnormalities.

In situ fluidization for peat bed rupture, and preliminary economic analysis.

This study concerns in situ fluidization (ISF), a new remediation method with potential application to the remediation of NAPL and heavy metal contaminants, by their release from the fluidized zone generated by a water jet. The present study examines the effect of ISF on layers of peat, of significance owing to its role as an important NAPL and metal contaminant trap. Once trapped, such contaminants are not readily accessible by most remedial methods, due to the low permeability and diffusivity of the peat. A simple tank experiment is used to demonstrate rupture of a peat layer by ISF, with removal of the peat as elutriated fines and segregated peat chunks. The application of ISF in the field is then examined by three field trials in uncontaminated sands, in both saturated and unsaturated conditions. Fluidized depths of up to 1.9 m in the saturated zone (with refusal on a peat layer) and 2.5 m in the unsaturated zone (no refusal) were attained, using a 1.9-m-long, 50 mm diameter jet operated at 5-13 1 s(-1). Pulses of dark turbidity and shell fragments in the effluent indicated the rupture of peat and shelly layers. The experiments demonstrate the hydraulic viability of ISF in the field, and its ability to remove peat-based contaminants. The issues of appropriate jet design and water generation during ISF are discussed, followed by a preliminary economic analysis of ISF relative to existing remediation methods.

Synthesis and characterization of catalysts produced from paper mill sludge. I. Determination Of NOx removal capability.

Characteristics and catalytic properties of a series of carbon-based catalysts (CBCs) produced from paper mill sludge were evaluated. The major processes involved in the production of the catalysts were chemical activation, impregnation, pyrolysis, and post pyrolysis rinsing. The porous structure, catalytic activity and thermostability of the catalysts were tailored during the production stage by introducing hetero-atoms (zinc chloride, and ferric nitrate) in the carbon structure. Characterization of the produced CBCs included determination of the surface area, pore size, and pore size distribution (PSD) from standard N2-adsorption isotherm data. The extent of graphitization and the presence of metal crystals were identified from X-ray diffraction (XRD). The limit of the catalyst gasification was estimated from thermogravimetric analysis (TGA) conducted in an oxidized environment. The NOx reduction capability of the produced catalysts was evaluated in the presence of carbon monoxide using a fixed bed reactor. The reaction temperature ranged from 300 to 500 degrees C. It was shown that paper mill sludge is an excellent precursor for the production of CBCs with NOx removal capability of 66-94%. The catalytic capability of the produced CBCs varied according to the method of production, catalyst surface properties (surface area, pore structure, PSD), metal composition and reaction temperature. The highest NOx removal capacity was observed for the catalytic reactions carried out at 400 degrees C. The mesoporous catalyst produced with a Zn:Fe molar ratio of 1:0.5 exhibited the maximum NOx removal catalytic activity of 94%.

WebSTer: a web-based surgical training system.

Training of medical staff on minimally invasive surgery (MIS) is an area where new effective training methods are needed. We have studied stent grafting, a type of MIS, which is used to treat abdominal aortic aneurysm. Our analysis revealed that this procedure requires a range of motor, perceptual and cognitive skills. In this paper, we present a training environment that could be used to acquire these skills. Our proposed solution differs from the usual VR solutions by operating within the World Wide Web as an environment for our system. This paper discusses how our solution covers the training skills and presents the results of an appraisal process, which we conducted to evaluate our solution.

Performance enhancement of batch aerobic digesters via addition of digested sludge.

The impact of the feed sludge (FS) concentration and addition of digested sludge (DS) to an aerobic digester was evaluated with respect to its capability for removal of the total suspended solids (TSS) and volatile suspended solids (VSS). The aerobic digesters, which operated in a batch mode at constant temperature and mixing rate, were initially filled with FS to 25%, 50%, 75%, and 100% of the reactor's volume. The remaining volume of the reactor was occupied by the DS, having DS/FS ratio of 3, 1, 1/3, and 0. Analysis of the experimental data showed that in the absence of DS, TSS, and VSS destruction rates are very small; however, increasing DS/FS ratio from 1/3 to 3 results in 74-77% increase in VSS and TSS destruction, respectively. The increase of the DS/FS ratio associated with increased ratio of the measured viable biomass (Cc) to VSS concentration (Xv) suggested that DS serves as the source of viable cell mass needed for degradation of organic solids. Assuming pseudo-first-order kinetics, it was shown that while organic solid destruction rate constants (k) are inversely related to initial concentrations of sludge, their values increase with increasing DS/FS ratios.