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H Farid

Publications and source records attributed to H Farid.

9 recordsLinked to original sources
PubMed1998

Range estimation by optical differentiation.

We describe a novel formulation of the range recovery problem based on computation of the differential variation in image intensities with respect to changes in camera position. This method uses a single stationary camera and a pair of calibrated optical masks to measure this differential quantity directly. We also describe a variant based on changes in aperture size. The subsequent computation of the range image involves simple arithmetic operations and is suitable for real-time implementation. We present the theory of this technique and show results from a prototype camera that we have constructed.

Humans↗
PubMed1998

Twenty-four-hour change in axial length in the rabbit eye.

PURPOSE: To study the 24-hour changes in axial length, lens thickness, and anterior chamber depth in rabbits and to examine the role of ocular sympathetic activity on these changes. METHODS: Young adult rabbits were entrained to a daily 12-hour light-12-hour dark cycle. Axial length, lens thickness, and anterior chamber depth were measured using ultrasonic techniques. In the first group of 12 rabbits, measurements were taken in the middle light phase and in the early dark phase. In the second group of 12 rabbits, measurements were taken in constant dark every 2 hours for a period of 24 hours. The latter group of rabbits underwent unilateral transection of the cervical sympathetic trunk. Three to four weeks later, axial length, lens thickness, and anterior chamber depth were measured again in constant dark every 2 hours for 24 hours. RESULTS: Under the light- dark condition, axial length and anterior chamber depth were larger in the early dark phase than in the middle light phase. Lens thickness changed in the opposite direction. Under the constant-dark condition, axial length and anterior chamber depth changed gradually during the 24-hour period. The trough appeared in the late subjective light phase, and the peak appeared in the late subjective dark phase. Lens thickness remained relatively constant. In the eyes with decentralized ocular sympathetic nerves, 24-hour changes in axial length and anterior chamber depth occurred. However, magnitudes of nocturnal enlargement were relatively smaller than those in the intact eyes. Although larger in the decentralized eyes, lens thickness appeared unchanged in either eye for 24 hours. CONCLUSIONS: Consistent 24-hour changes in axial length and anterior chamber depth occur in young adult rabbits. These changes are driven endogenously. Significant portions of the nocturnal enlargements of axial length and anterior chamber depth are unrelated to ocular sympathetic activity.

Animals↗
PubMed1996

Prediction and evaluation of side-chain conformations for protein backbone structures.

A common approach to protein modeling is to propose a backbone structure based on homology or threading and then to attempt to build side chains onto this backbone. A fast algorithm using the simple criteria of atomic overlap and overall rotamer probability is proposed for this purpose. The method was first tested in the context of exhaustive searches of side chain configuration space in protein cores and was then applied to all side chains in 49 proteins of known structure, using simulated annealing to sample space. The latter procedure obtains the correct rotamer for 57% and the correct chi 1 value for 74% of the 6751 residues in the sample. When low-temperature Monte-Carlo simulations are initiated from the results of the simulated-annealing processes, consensus configurations are obtained which exhibit slightly more accurate predictions. The Monte-Carlo procedure also allows converged side chain entropies to be calculated for all residues. These prove to be accurate indicators of prediction reliability. For example, the correct rotamer is obtained for 79% and the correct chi 1 value is obtained for 84% of the half of the sample residues exhibiting the lowest entropies. Side chain entropy and predictability are nearly completely uncorrelated with solvent-accessible area. Some precedents for and implications of this observation are discussed.

Algorithms↗
PubMed1996

Surgical management of massive splenomegaly.

Recent reports document an increased mortality and morbidity associated with splenectomy for massive splenomegaly (<1000 g), with a morbidity that is 2 to 10-fold higher than that seen for splenectomy for normal size spleens. Preoperative angiographic embolization of the splenic artery has been advocated as a means to decrease this morbidity and mortality. In a retrospective review of 100 splenectomies performed at Kaiser Permanente (Los Angeles, CA), 20 were performed for splenomegaly, average weight 1811 g (1050-3700 g), and 80 were normal sized spleens. Mortality for normal sized spleens is 1.25 per cent, and for those performed for splenomegaly is zero. Likewise, the morbidity for splenectomy of normal sized spleens was 21.25 per cent, but for splenomegaly, a 20 per cent morbidity rate was observed. Average blood loss with splenomegaly was 696 mL, slightly higher than the 600 mL blood loss for normal sized spleens. Sixty-seven per cent of patients with splenomegaly required no transfusion, and none required more than two units. Of patients with normal size spleens, 75 per cent required no transfusion, and 96 per cent required two units or less. Splenectomy for splenomegaly is possible without an increase in morbidity or mortality. In this series, preoperative embolization was not performed; however, the morbidity and mortality rates compare favorably with series in which it was performed. Preoperative embolization of the splenic artery may be unnecessary and may expose the patient to additional expense, risk, and discomfort.

Adolescent↗
PubMed1995

Methods to decrease the morbidity of abdominoperineal resection.

Recent reports stress that abdominoperineal resections (APR) are associated with many complications, including hemorrhage, long hospitalization, and delayed closure of an open perineal wound. Thirty-five patients underwent an abdominoperineal resection for cancer at Kaiser Permanente Medical Center, Los Angeles, from January 1989 to December 1993. All patients, except two, had their perineal wound closed after closure of the peritoneum and insertion of closed system suction catheters. Ninety-one per cent of patients achieved successful primary healing. Three patients (8.5%) suffered perineal wound dehiscence. Overall morbidity was 55 per cent, with urinary retention being the most common, occurring in 23 per cent of patients. This was managed successfully by early in-and-out self catheterization. There was no incidence of urinary tract infections. There were no operative deaths. Length of stay averaged 8.6 days, with a median of 7 days. Five patients had previous radiation therapy. Of those, two (40%) had perineal wound dehiscence, compared to only one of 33 (3.3%) patients without previous radiation. APRs can be done with minimal mortality, although with an increased morbidity in irradiated patients. Primary closure and drainage of the perineal wound significantly lowers the complication rate, as does early Foley removal and self in-and-out catheterization.

Adenocarcinoma↗
PubMed1994

Hepatic resections: changing mortality and morbidity.

Hepatic resections have been associated with high mortality and morbidity; therefore, this procedure was not used frequently. With increasing safety, acceptance of the procedure grew. A review of recent series still reveals a strikingly high incidence of complications. However, in a review of the last 100 hepatic resections performed at Kaiser Permanente Medical Center, Los Angeles, the average blood loss was 1351 mL, (range 90-10,000 mL) with a median of 900 mL. Blood transfusion requirements averaged 1.5 units, with 50 per cent of patients requiring no transfusion, and 80 per cent of patients requiring two units or less. Cirrhosis, present in 15 per cent of our patients, was associated with increased blood loss and morbidity. The use of the Cavitron Ultrasonic Aspirator (CUSA) and the liver clamp have had a major impact on reducing intraoperative blood loss and transfusion requirement. Operative time was significantly reduced from previous reports, to an average of 221 minutes (90 to 410 minutes). Hospital stay averaged 7 days, with a median of 6 days. Both the mortality rate of 2 per cent and the morbidity rate of 22 per cent represent significant improvements. Utilizing modern techniques, hepatic resections can be done with acceptable mortality and mortality, and may lead to its increased application.

Adolescent↗
PubMed1994

Gastrointestinal complications associated with cardiopulmonary bypass procedures.

Gastrointestinal complications after cardiopulmonary bypass (CPB) procedures are rare, but when they do occur, they carry a significant incidence of morbidity and mortality. Over a 5-year period spanning 1988-1992, 4923 CPB procedures were performed and 64 patients were identified who suffered a GI complication, giving an incidence of 1.3 per cent. The most frequent complications were GI bleeding (40%) and pancreatitis (34%). Other complications included acute cholecystitis (11%), perforated duodenal ulcer (8%), ischemic bowel (5%), and diverticulitis (2%). Complications occurred most frequently in patients undergoing procedures with longer pump and cross-clamp times, such as valvular and combination (CABG/valve) procedures. Redo procedures and the use of an intra-aortic balloon pump increased the risk of developing a GI complication 2.5 and 12 times, respectively. Patients were treated aggressively both medically and surgically, but suffered a higher mortality (16%) as compared to those not suffering a GI complication (3%). We conclude that GI complications after CPB procedures are infrequent but lethal. Clinical features are often subtle, and a high index of suspicion is needed for early diagnosis and aggressive treatment.

Adolescent↗