Blind Segment Research Articles

Tunnel and ventilation design of the Eupalinos’ aqueduct in Samos, Greece

Polycrates’ extended reign and a recently discovered extension of the distribution sector of the aqueduct prompted this review of the design and tunnelling of the Eupalinos’ aqueduct. Both aqueducts, the Archaic and Roman, cross an affluent area of the upper city, located less than 10 m below the level of the water source, a condition critical for the aqueduct’s design. The tunnel’s detour from its initial axis and the function of the tunnel as an integrated element of the city’s defensive works are also discussed. A key consideration of this review is the ventilation of the lengthiest blind segments of the Eupalinos’ tunnel, given that natural ventilation in a blind gallery is generally not effective beyond about 50 m. Considering the historical evolution of ventilation in underground works, it is proposed here that a ventilation circuit was maintained along the tunnel through an auxiliary gallery dug simultaneously a few meters below the tunnel.

Coseismic and Early Postseismic Slip Models of the 2021 Mw 7.4 Maduo Earthquake (Western China) Estimated by Space‐Based Geodetic Data

AbstractThe May 22nd, 2021,7.4 Maduo earthquake occurred on an intraplate fault of Bayan‐Har block in the Tibet Plateau. Here, we derive the coseismic and early postseismic surface deformations from the Sentinel‐1 (S1) interferometric synthetic aperture radar (InSAR) data. We use the subpixel offsets of SAR and Sentinel‐2 (S2) optical images to determine the surface rupture traces. The fault geometry and coseismic fault slip distribution of multi‐segmented ruptures are estimated by inverting InSAR interferograms and SAR pixel offsets. We show that at least five fault segments with curved geometry are activated, with a peak coseismic slip of about 5 m. The geodetic data inversion suggests that an NW‐striking blind segment near the Eling Lake may have ruptured during the 2021 event. Postseismic slip inversion with the 60‐day cumulative line‐of‐sight deformations, shows that the early afterslip of 0.1 ∼ 0.3 m occurred mostly toward the downdip direction of the main coseismic slip asperities. The afterslip geodetic moment accounts for approximately 15.3% of the coseismic one. Coulomb stress analysis shows that the nucleation of the Maduo earthquake is partially facilitated by the 1947 M7.7 Dari earthquake.

Deformation and Fault Propagation at the Lateral Termination of a Subduction Zone: The Alfeo Fault System in the Calabrian Arc, Southern Italy

The Calabrian Arc subduction, southern Italy, is a critical structural element in the geodynamic evolution of the central Mediterranean basin. It is a narrow, northwest-dipping slab bordered to the southwest by the Alfeo Fault System (AFS) and to the northeast by a gradual transition to a collision. We used a dense set of two-dimensional high-penetration (up to 12 s) multichannel seismic reflection profiles to build a three-dimensional model that spans the AFS for over 180 km of its length. We find that the AFS is made up of four deep-seated major blind segments that cut through the lower plate, offset the subduction interface, and only partially propagate upward across the accretionary wedge in the upper plate. These faults evolve with a scissor-like mechanism (mode III of rupture propagation). The shallow part of the accretionary wedge is affected by secondary deformation features well aligned with the AFS at depth but also mechanically decoupled from it. Despite the decoupling, the syn-tectonic Pliocene-Holocene deposits that fill in the accommodation space generated by the AFS activity at depth, constrain the age of inception of the AFS and allows us to estimate its throw and propagation rates. The maximum throw value is 6,000 m in the NW sector and decreases to the SE. Considering the age of faulting, the fault throw rate decreases accordingly from 2.31 mm/yr to 1 mm/yr. The propagation rate decreases from 62 mm/yr to 15 mm/yr during the Pliocene-Pleistocene, suggesting that also the Calabrian subduction process should have slowed down accordingly. The detailed spatial and temporal reconstruction of this type of faults can reveal necessary information about the evolution of subduction systems.

Geodetic Evidence for a Blind Fault Segment at the Southern End of the San Jacinto Fault Zone

AbstractThe San Jacinto Fault (SJF) splits into several active branches southeast of Anza, including the Clark fault and the Coyote Creek fault. The Clark fault, originally believed to terminate at the southern tip of the Santa Rosa Mountains, was suggested to extend further to the southeast to a junction with the Superstition Hills fault based on space geodetic observations and geologic mapping. We present new interferometric synthetic aperture radar and GPS data that confirm high deformation rates along the southeastern extent of the Clark fault. We derive maps of horizontal and vertical average velocities by combining data from the ascending and descending satellite orbits with an additional constraint provided by the azimuth of the horizontal component of secular velocities from GPS data. The resulting high‐resolution surface velocities are differentiated to obtain a map of maximum shear strain rate. Joint inversions of InSAR and GPS data suggest that the hypothesized blind segment of the Clark fault and the Coyote Creek fault have slip rates of 13 ± 3 mm/yr and 5 ± 4 mm/yr, respectively. The blind southern segment of the Clark fault thus appears to be the main active strand of the SJF, posing a currently unrecognized seismic hazard.

The use of HVSR measurements for investigating buried tectonic structures: the Mirandola anticline, Northern Italy, as a case study

The Mirandola anticline represents a buried fault-propagation fold which has been growing during Quaternary due to the seismogenic activity of a blind segment belonging to the broader Ferrara Arc. The last reactivation occurred during the May 2012 Emilia sequence. In correspondence with this structure, the thickness of the marine and continental deposits of the Po Plain foredeep is particularly reduced. In order to better define the shallow geometry of this tectonic structure, and hence its recent activity, we investigated in a depth range which is intermediate between the surficial morphological observations and seismic profiles information. In particular, we carried out numerous passive seismic measurements (single-station microtremor) for obtaining the horizontal-to-vertical spectral ratio. The results of a combined analysis of the peak frequency and its amplitude nicely fit the available geological information, suggesting that this low-cost geophysical technique could be successfully applied in other sectors of wide morphologically flat alluvial plains to investigate blind and completely buried potential seismogenic structures.

TH‐C‐WAB‐05: Blind Functional Volume Segmentation in PET

Purpose: To propose a blind PET functional volume segmentation method that does not need any prior calibrations. Methods: The partial volume effect (PVE) in PET imaging was considered as a forward problem that convolves the original target object with the point spread function (PSF) of the PET scanner, and made a PET image blurred. We showed that the optimal threshold for accurate object localization in a PET image is a function of the ratio of the object size to the PSF standard variance. We defined a new quantity, the optimal volume ratio (OAR), which represents the ratio of the segmented volume when using the optimal threshold to the whole target volume with greater activity than the background. The OAR can be expressed as a function of the optimal threshold, and was then used to derive the optimal threshold through a sequence of region growing algorithms with different thresholds. The new method avoids solving the ill‐conditioned inverse problem, and is fully blind to the PET scanner. The proposed method was tested on PET phantom with known object location and extension, and its robustness with respect to source‐to‐background ratio (SBR) and object size was evaluated. Results: At all SBR levels and for all object sizes, the new blind segment method performed similarly to existing methods with prior calibrations, and outperformed existing methods that do not take into account PVE. In addition, the new blind segment method is robust to the changes of SBR level and object size. Conclusion: The results showed that the proposed blind method did not need any prior calibrations and performed well for the functional volume segmentation in PET.

Geodetic slip rates in the southern San Andreas Fault system: Effects of elastic heterogeneity and fault geometry

We use high resolution interferometric synthetic aperture radar and GPS measurements of crustal motion across the southern San Andreas Fault system to investigate the effects of elastic heterogeneity and fault geometry on inferred slip rates and locking depths. Geodetically measured strain rates are asymmetric with respect to the mapped traces of both the southern San Andreas and San Jacinto faults. Two possibilities have been proposed to explain this observation: large contrasts in crustal rigidity across the faults, or an alternate fault geometry such as a dipping San Andreas fault or a blind segment of the San Jacinto Fault. We evaluate these possibilities using a two‐dimensional elastic model accounting for heterogeneous structure computed from the Southern California Earthquake Center crustal velocity model CVM‐H 6.3. The results demonstrate that moderate variations in elastic properties of the crust do not produce a significant strain rate asymmetry and have only a minor effect on the inferred slip rates. However, we find that small changes in the location of faults at depth can strongly impact the results. Our preferred model includes a San Andreas Fault dipping northeast at 60°, and two active branches of the San Jacinto fault zone. In this case, we infer nearly equal slip rates of 18 ± 1 and 19 ± 2 mm/yr for the San Andreas and San Jacinto fault zones, respectively. These values are in good agreement with geologic measurements representing average slip rates over the last 104–106 years, implying steady long‐term motion on these faults.

Micro-lightguide spectrophotometry for tissue perfusion in ischemic limbs

To validate micro-lightguide spectrophotometry (O2C) in patients with lower limb ischemia and to compare results with those obtained from toe blood pressure. We prospectively examined 59 patients, 24 of whom complained of claudication, 31 had critical ischemia, and four were asymptomatic. Diabetes was present in 19 (32%) patients. Saturation (SO(2)) and flow measured with O2C were determined with the limb in the horizontal position followed by a 55-cm elevation. Toe pressures were determined in the horizontal position only. In addition, 13 patients were examined before and, on average, 3 days after revascularization. Median SO(2) was 62% (25%-75% percentile: 37%-75%) with the limb in the horizontal position and 16% (3%-41%) with the limb elevated. Comparing the individual toe pressures with SO(2) values measured in the horizontal position and elevated position revealed a significant correlation (r(s) = 0.40; P < .01 and r(s) = 0.56; P < .01, respectively). A low SO(2) (ie, <40% in the horizontal position and <20% in the elevated position) was highly predictive of a toe pressure of 40 mm Hg or less. In the horizontal position, the positive predictive value was 100%, whereas the negative predictive value was 47%. The similar figures in the elevated position were a positive predictive value of 97% and a negative predictive value of 68%. Postoperatively, SO(2) increased significantly from 27% (P25%-75%: 11%-75%) to 79% (68%-87%) in the horizontal position (P = .008) and from 14% (P25%-75%: 2%-39%) to 55% (30%-73%) in the elevated position (P = .011), respectively. Looking at the individual 13 cases in which revascularization was performed, three patients had a partial reconstruction (ie, superficial femoral artery occlusion distal to a central reconstruction or reconstruction to a popliteal blind segment). These patients had significantly lower postoperative SO(2) as well as toe pressure compared with the 10 patients with unobstructed flow to the foot. O2C was easy to use, fast, and painless. The most useful finding was the high predictive value of a low saturation and the rise in O2C values after successful revascularization.

Fecal-tagging computed tomographic eolonography with structure-analysis electronic cleansing for detection of colorectal flat lesions

Objective To evaluate the feasibility and sensitivity of the 3D-reading of fecal-tagging computed tomographic colonography0 (CTC) with a novel structure-analysis electronic cleansing (SAEC) in detecting colorectal flat lesions in comparison with a prospective 3D reading with Viatronix colon system (V3D) and 2D reading without electronic cleansing (2D). Methods Forty CTC cases with flat lesions were retrospectively observed. The subjects from a muhicenter clinical trial underwent cathartic bowel preparation with orally administrated barium-based fecal tagging. Sixty-nine flat lesions were confirmed using colonoscopy and histopathology as a reference standard. The results from SAEC reading were compared with those of prospective V3D and 2D readings. Results Overall detection sensitivity with SAEC was 51% (35/69), which was statistically higher than that of 32% (22/69) and 29% (20/69) with V3D and 2D readings, respectively (P<0.05). The sensitivities in detecting not-on-fold flat lesions were 61% (23/38), 45% ( 17/38), and 42% (16/38) with SAEC, V3D, and 2D readings, respectively; whereas those of on-fold flat lesions were 39% (12/31), 16% (5/31), and 13% (4/31), respectively. None of the eight fiat lesions (2-9 mm) at cecum was detected by any of the three reading methods. Excluding the flat lesions at cecum, the sensitivity with SAEC for detecting flat lesion ≥ 4 mm increased to 84% (31/37). Conclusions The fecal-tagging CTC with structure-analysis electronic cleansing could yield a high sensitivity for detecting flat lesions ≥ 4 mm. The not-on-fold flat lesions were detected with higher sensitivity than on-fold flat lesions. Cecum may be a blind segment in the detection of flat lesions. Key words: Colonic diseases; Cecal diseases; Colonography, computed tomographic

An 18,000‐year record of recurrent folding inferred from sediment slices and cores across a blind segment of the Biwako‐seigan fault zone, central Japan

Closely spaced sediment slices and cores reveal evidence for recurrent folding in the past 18 ka across the tip of a blind thrust fault near Kyoto, central Japan. The slices, 0.4 m wide and up to 5.5 m long, collected with “geoslicer” technique, exposed the central 100 m of a stratigraphic cross section that extends across a fold scarp in the southern Biwako‐seigan fault zone. A chronology inferred with 109 radiocarbon ages suggests that the most recent blind thrust earthquake occurred in the range A.D. 1060–1260, most likely around A.D. 1170. Historical accounts strongly support that this earthquake correlates with the 1185 M 7.4 Genryaku Kyoto earthquake. The earthquake produced a broad surficial fold more than 200 m wide with a vertical displacement of 3 m or more. Earlier paleoearthquakes lack well‐defined event horizons, but we find that the deformation of the 18‐ka unit is likely 4 times that from the most recent earthquake. Our results show the application of geoslicer technique to blind thrust paleoseismology, for which traditional trenching is rarely applicable or useful because of broad surficial deformation and commonly shallow groundwater at potential paleoseismic sites.

Choledochoduodenostomy in calculous biliary tract disease.

During a 14-year period ending in June 1979, 342 patients with calculous biliary disease underwent choledochoduodenostomy either as a primary procedure or during reoperation. Eighty per cent of the patients were aged 50 years or more. Follow-up was either by personal interview and physical examination or by means of a questionnaire, 90 per cent of the patients being assessed at periods ranging from 6 months to 14 years. A high incidence of common bile duct dilatation was found in older patients, in patients with a long history and in patients submitted to reoperation. There were no operative deaths. Postoperative complications occurred in 22 cases (6.4 per cent) and, in particular, no patient developed ascending cholangitis or symptoms related to the "blind segment". Choledochoduodenostomy is a valuable and safe procedure and can be used on wide indications, especially where peroperative cholangiography is not available.

Blind-ending ureteral duplication with calculi

or reflux. 3 Because of non-filling of the blind ureter on intravenous urography (IVU), the diagnosis of blind-ending ureteral duplication is best made with the help of retrograde pyelography. However, a blind-ending bifid ureter can be opacified on IVU if uretero-ureteral reflux is present. The anomaly can also be seen on computerized tomography. 4 We report a case featuring a long, blind-ending ureteral duplication complicated by stone formation. Case Report A 45-year old male was admitted with right loin pain, dysuria and frequency of micturition of 3 months duration. He reported passing stones in urine in the past, but had no history of fever or recurrent urinary tract infection (UTI). The patient had presented to another hospital with the same complaints 6 weeks before reporting to our unit. Cystoscopy at that hospital showed a normal bladder with no calculus in the bladder or the ureters. He came to our unit because of persistent pain. Laboratory investigations showed normal renal function. Urine microscopy and culture showed red blood cells in the urine, but no bacterial growth. Plain radiograph of the kidneys, ureters and bladder (KUB) revealed two radio-opaque shadows in the region of the lower third of the right ureter (Figure 1). However, IVU showed patent ureters with no calculus seen in either ureter (Figure 2). A pre-operative CT scan showed grossly normal kidneys and ureters with 2 extravesical masses in the pelvis. Cystoscopy in our unit revealed an edematous mass just caudal and medial to the right ureteric orifice. A guide wire introduced into the right ureter under fluoroscopic control showed that the radio-opaque shadows seen on KUB were extraureteral and extravesical. Right retrograde pyelography showed a patent ureter with opacification of a normal pelvicalyceal system. Transurethral resection of the bullous, edematous mass revealed another ureteric orifice. Retrograde pyelography through the other ureteric orifice revealed multiple filling defects and a long blind-ending ureter, with no opacification of the pelvi-calyceal system (Figure 3). Ureteroscopy through the second ureteric orifice confirmed the presence of 2 calculi, which were removed using a Dormia basket. Post-operatively the patient became pain free. Postoperative micturating cystourethrogram (MCUG) performed 3 months after calculus extraction from the duplicated ureter, showed no vesicoureteric reflux (VUR).

Progressive growth of San Clemente Island, California, by blind thrust faulting: implications for fault slip partitioning in the California Continental Borderland

We find that the genesis of San Clemente Island and its surrounding submarine platform is consistent with progressive slip on two, southeast-striking, southwest-dipping, blind thrust fault segments. Since their inception 2 to 5 Ma, 3 km of compression normal to the N150°E fault strike has been accommodated with 1700 m of domal uplift of the San Clemente Anticlinorium. The existence of an extensive suite of Pleistocene marine terraces provides evidence that slip and uplift are continuing today. Based on direct terrace fossil age determinations and correlations of terrace heights with global sea-level curves, we estimate that San Clemente Island is currently uplifting at between 0.2 and 0.5 mm yr−1. This translates into 0.6–1.5 mm yr−1 of thrusting on the causative blind thrusts beneath the island. Unlike the situation at nearby Palos Verdes, where a simple twist in a regional strike-slip fault accommodated both fault-parallel and fault-normal motions, the shallow dips of the thrusts suggest that, if regional strike-slip motion on the San Clemente Fault exists, it must be partitioned onto through-going surfaces distinct from the thrusts. Current GPS data are sparse and equivocal, but they indicate that 1–4 mm yr−1 of compression and 4–7 mm yr−1 of strike slip are absorbed in the California Continental Borderland. With the Palos Verdes Fault taking some 3 mm yr−1 from the strike-slip budget, 1–4 mm yr−1 of motion could be present on a through-going San Clemente Fault. When translated into an annual moment release rate using Kostrov's formula, GPS strains predict that between 2.5 and 4.9 times 1017 N m yr−1 of earthquake potential is available offshore from San Diego to the Santa Barbara Channel. Distribution of this moment budget among various earthquake magnitudes is arguable, but we predict that M > 6 quakes in the Borderland could recur between 30 and 80 years, and M > 7 quakes might be found every 310 to 580 years.

The “ad hoc” estimation of outflow does not predict patency of infrainguinal reconstructions

This prospective study was performed to evaluate the clinical implication of the adhoc estimation (also called SVS score) of outflow on patency of infrainguinal in situ femoropopliteal or -distal bypasses. The bypasses were followed with Duplex scanning at 1, 3, 6, and 12 months after surgery. Fifty-three bypasses were recruited for the study, 20 of which were performed in 17 diabetics. In 47% the adhoc scoring was < or = 4.5 and in 53% it was between 5 and 10 (1 corresponds to an excellent outflow and 10 to a blind segment). Within the first 30 days eight occlusions occurred, all of which were surgically corrected. The adhoc score for these bypasses was 4.2 vs. 4.9 (NS) for those who did not occlude. During follow-up, revisions were performed in 21 cases (40%) with 30 interventions. At the end of 1 year, 68% of the bypasses were patent (80% among diabetics and 64% among non-diabetics, NS). Patency at 1 year was not influenced by the adhoc classification. The estimation of outflow from angiography seems to be of no value in predicting graft patency in infrainguinal grafting.

Respiratory failure due to retained esophagus: A complication of esophageal replacement

Recurrent fistulas occur in about 10% of infants treated for esophageal atresia with distal tracheosophageal fistula. Failed repair of a recurrent fistula rarely requires esophageal replacement and removal or diversion of the native esophagus. We present a patient who underwent multiple operations for recurrent tracheosophageal fistula whose native esophagus was eventually replaced with a colonic interposition graft. Over the subsequent 9 years he experienced failure to thrive, respiratory distress, and repeated pulmonary infections attributed to chronic aspiration. Eventually, he developed respiratory failure and required endotracheal intubation and mechanical ventilation. He became increasingly difficult to ventilate and, in spite of aggressive efforts, suffered a cardiac arrest from which he could not be resuscitated. At postmortem, a ditated blind segment of native esophagus, which was compressing and obstructing the malacic trachea, was found in the posterior mediastinum. Death was caused by massive air embolus, which was in turn attributed to the high airway pressures needed to ventilate the patient. Tracheal compression by a remnant of native esophagus should be considered in the differential diagnosis of respiratory failure after esophageal replacement.

Why the Operation I Prefer is Vertical Banded Gastroplasty 5.0.

Vertical banded gastroplasty (VBG) is easy for the patient, requiring no nasal gastric tube, gastrostomy, feeding enterostomy, or central venous line. Clear liquids are begun the first morning and pursed foods the second day. VBG with a 5.0 cm collar and a 13 ml pouch provides sufficient weight control with minimal risk and side effects. Splenectomy risk is 0.3%, peritonitis from leak 0.6% and operative mortality 0.24%. VBG causes no malabsorption or bacterial overgrowth because there are no blind segments. VBG does not predispose to difficult to diagnose, lethal, closed segment obstruction because of the absence of exclusion. VBG minimizes risk of acid peptic disease by preserving normal feedback control of acid secretion. Revisions have been less than 2% per year. The first 250 patients to be followed for 5 years with VBG-5.0 showed an 80% success in achieving 25% of excess weight loss without revision. For these successful patients the average percentage excess weight loss was 60% for the morbid obese (MO 160 to 225% of ideal) and 52% for the super (SO over 225% of the ideal). Absolute weight averages changed from 122 to 86 kg for MO and from 159 to 110 kg for SO.

Vascular Rereconstruction and Major Amputations A Case Report

In an effort to increase the probability of primary below-knee amputation healing the author converted a common femoral artery to dorsalis pedis artery vein bypass to a common femoral artery to below-knee popliteal bypass to a blind popliteal segment along with a below-knee amputation in a patient with an osteomyelitic Chopart amputation. The patient was rapidly and successfully rehabilitated with a prosthesis and the bypass remained patent. This case report illustrates that preservation of the important functional aspect of the knee joint in the elderly population is justification for vascular reconstruction since the probability of primary below-knee amputation healing is enhanced.

Microdissection Demonstration of the Lesion of the Endocrine Kidney in Children

Microdissection of nephrons of kidneys of children showing advanced ischemic tubular atrophy, and removed for control of hypertension, demonstrates marked proximal convoluted tubular atrophy, with formation of multiple small proximal tubular diverticula. These diverticula presumably contribute to the microscopic appearance of large numbers of small tubules lined by low epithelial cells with pale or clear cytoplasm, adjacent to glomeruli in the cortices of kidneys showing ischemic tubular atrophy (endocrine kidney). Segmentation of such atrophic tubules leads to formation of blind segments (microcysts), as demonstrated in this study and by Oliver. The distinctive microscopic appearance of the endocrine kidney, a not infrequent finding in kidneys of children with chronic renal insufficiency who require nephrectomy for control of hypertension, has not hitherto been emphasized in the literature on pediatric renal disease.

Aberrant Carotid Artery Injured at Myringotomy-Reply

In Reply.— We appreciate Dr Ehni and Dr Sugar's comments regarding our report. During our research, we found references describing aberrant passage of the carotid artery through the middle ear dating back some 15 years. This anomaly is now readily detected via tomography or angiography or both. Biopsy of such a mass beneath the tympanic membrane should certainly be deferred until such studies have excluded this anomaly. We cannot state categorically that simple carotid artery ligation would have failed to control hemorrhage in our patient. The issue, of course, is retrograde flow. We disagree with Dr Sugar regarding such flow in the internal carotid artery. We have observed retrograde flow below the ophthalmic artery in several patients. His suggestion that, after internal carotid artery ligation, the carotid artery below the ophthalmic artery would become a blind segment may be true, but not in this instance. In our patient, this portion

Unexpected problems of external choledochoduodenostomy: Fiberscopic examination in 15 patients

Fiberscopic examination was carried out to investigate the condition of the stoma and bile duct and to assess the postoperative effects of the procedure on the upper gastrointestinal tract in 15 patients who received external side-to-side choledochoduodenostomy. The stoma remained patent, with a round or oval shape, in all 15 patients. Residual sutures were found at the stoma in 4 of 15 patients, 3 of whom had inflamed stomal mucosa. Food debris was found in the blind segment in four of seven patients, but all 4 had large stomas. In three patients food debris was floating and easily discharged through a stoma. In the other patient much food debris had accumulated and was firmly attached to the mucosal surface. Gastroduodenal lesions were noted in 9 of 15 patients: redness at the antrum in 3, multiple erosions at the antrum in 2, gastric ulcer in 1, redness at the bulbus in 1 and duodenal ulcer in 2. Bile reflux into the stomach was found in 9 of 15 patients, 5 of whom had gastric lesions, and duodenal mucosa was constantly exposed to bile in all 15 patients.