Central Defect Research Articles

Acute central corneal haze and thinning with atypical keratitis presentation

A 24-year-old woman presented with a 7-day history of blurry vision, redness, and extreme pain in her right eye. She had no pertinent medical or ocular history and did not use spectacles or contacts. Uncorrected distance visual acuity (UDVA) was 20/40 in the right eye and could not be improved with refraction. Slitlamp examination revealed a 1.5 × 1.5 mm central epithelial defect with surrounding white blood cell recruitment. Confocal microscopy (Figure 1JOURNAL/jcrs/04.03/02158034-202304000-00020/figure1/v/2023-03-24T200747Z/r/image-tiff) was performed, and she was treated with chlorhexidine 0.02% drops every hour in the right eye. 2 weeks later, the cornea had completely re-epithelialized; however, persistent corneal haze, decreased visual acuity, and corneal thinning and flattening was noted. Pachymetry was 484 µm in the right eye and UDVA was 20/40 (Supplemental Figure 1, available at http://links.lww.com/JRS/A836). In the following 2 weeks, UDVA improved to 20/25. 6 months after the initial presentation, UDVA was unchanged and faint central corneal haze was noted on examination (Figure 2JOURNAL/jcrs/04.03/02158034-202304000-00020/figure2/v/2023-03-24T200747Z/r/image-tiff). Of interest, her family history is significant for her younger 16-year-old brother with 3 prior episodes of a similar type of keratitis/keratopathy over the course of 2 years in both eyes with similar central paracentral corneal haze, thinning, and flattening and similar confocal findings (Figure 3JOURNAL/jcrs/04.03/02158034-202304000-00020/figure3/v/2023-03-24T200747Z/r/image-tiff). He also was unresponsive to topical antibiotics and antivirals except topical chlorhexidine. Her brother has been our patient for the last several years prior to her first visit to our clinic. What is your diagnosis? What medical diagnostic tests, if any, would you recommend? Is this an infectious or simply an inflammatory response? Is there any genetic or familial predisposition?

Utility of Contrast Echocardiography in the Diagnosis of a Primary Nonfunctioning Cardiac Paraganglioma with a Coronary Aneurysm

Cardiac paragangliomas (PGLs) are rare neuroendocrine tumors, and data regarding the features of nonfunctioning PGLs are limited. These tumors are extensively vascularized and have high risk of hemorrhage for surgery and even biopsy. Differential diagnosis including biochemical analysis of these PGLs is important for further management. In this case report, we present the clinical, laboratory, imaging, and radionuclide presentations of a rare primary nonfunctioning cardiac PGL with a coronary aneurysm. Echocardiography initially showed a large echogenic mass in the left atrioventricular groove. The mass presented a diffuse hyperenhancement pattern with a central perfusion defect on contrast echocardiography. The tumor enclosed the left coronary artery from the coronary orifice, and an aneurysm was found in the left circumflex artery, with significantly increased flow velocity. These echocardiographic features and its susceptible location are indicative of the presence of a cardiac PGL. Although all biochemical evaluations of catecholamines from blood and urine samples were negative, positron emission tomography and scintigraphy finally confirmed the diagnosis of a primary cardiac PGL. Therefore, when imaging features are indicative of the presence of PGLs, the implementation of radionuclide imaging for final diagnosis is required even if the biochemical results are negative. Recognizing these uncommon Doppler and contrast echocardiographic characteristics is important for early diagnosing these nonfunctioning PGLs.

Patterns of glenoid bone loss in revision of anatomic shoulder arthroplasty: the impact of prior glenoid resurfacing

BackgroundHistorically, glenoid resurfacing has been avoided in the young patient due to a perceived risk of early glenoid loosening and destructive bone loss. As a result, many young patients with end-stage arthritis undergo humeral-based hemiarthroplasty with subsequent incomplete pain relief. The aim of this study was to determine the status of glenoid bone stock in patients undergoing revision of a painful hemiarthroplasty versus anatomic total shoulder arthroplasty (aTSA). MethodsUsing an institutional shoulder arthroplasty revision database, all patients undergoing revision for aseptic glenoid-based pain after hemiarthroplasty or glenoid loosening of aTSA were identified. Patient demographics, implant longevity prior to revision, and implanted construct at revision were collected for each patient. Based upon preoperative plain films, computed tomography when available, and intraoperative documentation, the status of the glenoid bone stock was described. ResultsA total of 39 patients (14 aTSA and 25 hemiarthroplasty) met the inclusion criteria. No statistically significant difference in age at the time of index arthroplasty (56.4 vs. 52.4 years; P = .18), age at time of revision (64.5 vs. 59.0 years; P = .07), proportion of males (64.2% vs. 56.0%; P = .74), or longevity of the revised implant (110.9 vs. 79.2 months; P = .08) were identified between the aTSA and hemiarthroplasty cohorts, respectively. Patients undergoing revision of aTSA were more likely to receive a reverse total shoulder arthroplasty at revision (85.7% vs. 48%; P = .04). Peripheral wear alone was noted in 40% (10/25) of hemiarthroplasty revisions and central defect alone was noted in 79% (11/14) of aTSA revisions. Combined defects (central and peripheral bone loss) were noted in three patients undergoing revision of an aTSA (21.4%) and five undergoing revision of a hemiarthroplasty (20%; P = 1.0). The number of cases with medialization at or beyond the coracoid (Kocsis Grade 2; 42.9% vs. 40%) and at or beyond the spinoglenoid notch (Kocsis Grade 3; 14% vs. 12%) was not different between groups (P = 1.0). Structural bone graft or augmented glenoid components were used at the time of revision in 29% (4/14) and 32% (8/25) of failed aTSA and hemiarthroplasty, respectively (P = 1.0). ConclusionDespite variability in the cohorts, this study demonstrates no significant improvement in residual glenoid bone stock by deferring glenoid resurfacing at the time of shoulder arthroplasty. At the time of glenoid-based failure, glenoid resurfacing results in central bone loss while hemiarthroplasty results in peripheral/eccentric bone loss.

Finite element analysis of biplanar customized reconstruction plates for lateral and central segmental defects of mandible

The purpose of this study is to compare biplanar custom mandibular reconstruction plates with locking reconstruction plates in bridging central and lateral mandibular segmental defects by using the finite element method. Central and two different types of lateral segmental defects were created on mandibular model that was generated from computed tomography of a male patient. Segmental defects were fixed with conventional locking reconstruction plates and two different custom designed plates with caudobuccal and dorsobuccal cover. Stress formation on hardware and screws, strain on bone under masticatory simulation were evaluated with a finite element model. The stress values on plate and screws were higher in conventional reconstruction plate than custom plates. Simulations of central segmental defect revealed maximum von Mises stresses of 643.62 MPa and 101.83 MPa in conventional reconstruction plate and biplanar plate, respectively. Biplanar plates revealed slightly higher von Mises stresses than extended surfaced biplanar plates. The screws close to resection area were exposed to higher stress than farther screws for whole groups. In conventional reconstruction plate, the maximum von Mises stress values of fixation screws were 268.66 MPa and 95 MPa for central segmental defect and lateral segmental defect, respectively. The study reveals that the biplanar custom reconstruction plates had a favourable effect on stress distribution and can enhance function and aesthetics as supporting mandible and flaps from two different planes.

Relationship between the Macular Microvasculature and Central Visual Field Sensitivity in Patients with Advanced Glaucoma

To evaluate the relationship between central visual field sensitivity (cVFS) and the structural parameters in patients with advanced glaucoma. Cross-sectional study. In total, 226 eyes of 226 patients with advanced glaucoma were classified into the "minor central defect" (mean deviation on 10-2 visual field test [MD10] > -10 dB) and "significant central defect" (MD10 ≤ -10 dB) groups. We examined the structural parameters using RTVue OCT and angiography, including the retinal nerve fiber layer, ganglion cell complex, peripapillary vessel density (VD), and superficial and deep macular VD (mVD). The assessment of cVFS included MD10 and the mean deviation of the central 16 points on the 10-2 VF test (MD16). We used Pearson correlation and segmented regression to assess the global and regional relationships between the structural parameters and cVFS. Correlation between structural parameters and cVFS. In the minor central defect group, the best global correlations existed between the superficial macular and parafoveal mVD and MD16 (r= 0.52 and 0.54, P < 0.001). In the significant central defect group, superficial mVD best correlated with MD10 (r= 0.47, P < 0.001). Segmented regression between superficial mVD and cVFS revealed no breakpoint was found as MD10 declined, but a breakpoint was identified at -5.95 dB for MD16, which was statistically significant (P < 0.001). The regional correlations between the grid VD and sectors of the central 16 points were significant (r= 0.20-0.53, P= 0.010 ∼P < 0.001). The fair global and regional relationships between mVD and cVFS suggest that mVD may be beneficial for monitoring cVFS in patients with advanced glaucoma. The author(s) have no proprietary or commercial interest in any materials discussed in this article.

STK36 splice site variant in an Australian Shepherd dog with primary ciliary dyskinesia.

Primary ciliary dyskinesia (PCD) represents a group of diseases characterized by impaired movement of cilia and subsequent health problems in diverse organ systems, notably the respiratory tract. Almost 50 candidate genes for PCD are known in humans. In this study, we investigated an Australian Shepherd dog with a history of recurrent respiratory infections and nasal discharge. A transmission electron microscopy investigation led to the diagnosis of PCD with central pair defect, in which the normal 9:2 arrangement of respiratory cilia was altered and reduced to a 9:0 arrangement. Whole genome sequencing data from the affected dog was obtained and searched for variants in PCD candidate genes that were not present in 918 control genomes from different breeds. This revealed a homozygous single base pair exchange at a splice site of STK36, XM_038585732.1:c.2868-1G>A. The mutant allele was absent from 281 additionally genotyped Australian Shepherd dogs. RT-PCR confirmed aberrant splicing in the affected dog with the skipping of exon 20 and the insertion of a cryptic exon, which is predicted to lead to a premature stop codon and truncation of 36% of the STK36 wild-type open reading frame, XP_038441660.1:(p.Met957Profs*11). STK36 variants were previously reported to cause PCD in humans and mice. The knowledge from other species together with the absence of the mutant allele in more than 1000 control dogs suggests STK36:c.2868-1G>A as the most likely candidate variant for PCD in the investigated case.

A Review of the Use of Buccal Fat Pad in Cleft Palate Repair.

To review the available evidence on the use of the Buccal Fat Pad in primary and secondary Cleft Palate repair. This is a narrative review. A computerized literature search was conducted for articles published till February 2022 using the Mesh phrases buccal fat pad AND cleft palate, Bichat's Fat pad AND cleft palate, buccal fat pad OR Bichats Fat pad AND cleft palate. A total of 35 articles were included in this review based on the set eligibility criteria. Most of the studies were retrospective case reviews (n = 16, 45.7%), and the aggregate number of patients from all included studies was 666. Reported uses of the buccal fat pad (BFP) in association with cleft palate repair include the closure of central cleft palate defect and nasal floor in primary cleft palate repair, oronasal fistula repair following primary repair of cleft palate, and closure of relieving incision defect in primary repair of cleft palate. Complications reported were 24 cases of Oronasal Fistula (ONF), 2 dehiscences, and 4 transient mucosal defects. The high success rate, vascularity, ease of tissue harvest, and low donor site morbidity all support its use as an adjunct flap in cleft palate repair, especially in the closure of wide palatal clefts, to prevent post-palatal repair fistula, wound contracture, and subsequently velopharyngeal insufficiency and possibly midface hypoplasia.

Central Facial Soft-Tissue Defect Following Surgical Resection: An Algorithm for Reconstruction

Background: Central facial soft tissue defect poses a unique challenge for the reconstructive surgeon. The three-dimensional properties of the aesthetic facial subunit and its related function are the goals for reconstruction. Considering the prominent social role of the face, the procedure to achieve a good quality of life for patients may cost more than a single surgery. This single-center study presents an algorithm of treatment for central facial soft tissue defect and it’s proposed classification according to the authors’ experiences. Methods: A retrospective review of medical records and photos of patients who underwent central facial soft tissue defect reconstruction in Cipto Mangunkusumo National Hospital, Jakarta, Indonesia, from 2009 to 2019. Patients who underwent free flap reconstruction were followed up, and the primary outcomes were assessed using the FACE-Q head and neck cancer (FACE-Q H&amp;N) scale. A classification system for central facial soft tissue defect with seven subtypes (1–7) based on the facial subunit and its treatment was proposed. Results: Twenty-five patients were included. The malignant tumor was the main etiology (88%), with basal cell carcinoma being the primary cancer pathology (64%). The average defect size was 120 cm2 (32-416 cm2) and most defects fell into subtype 6 of the classification (32%). Anterolateral thigh free flap (ALT) was the main flap of choice (64%), followed by radial forearm free flap (36%), with 92% of flaps succeeding rate from this series. All of the patients underwent at least one ancillary procedure following the reconstruction, while the average was 2 (1-6) procedures. FACE-Q H&amp;N outcomes, especially on the appearance and appearance distress scale, showed a low to moderate score with a 72% response rate. Conclusions: Central facial soft-tissue defect continues to challenge reconstructive surgeons. While the advances in free tissue transfer might improve the general outcomes, the numerous and costly secondary procedures do not usually end up in the best appearance. This study displayed the need for modern reconstruction modalities that provide high satisfaction in aesthetic and functional outcomes with fewer secondary procedures. Vascularized Composite Allotransplantation (VCAT) might be the future choice.

Uncemented total hip replacement with impaction bone grafting in protrusio acetabuli

Protrusio acetabuli is a central acetabular defect resulting from migration of femoral head medial to Kohler’s line. Idiopathic central displacement of femoral head within the acetabulum is quite rare. However, it may be seen in arthritic hips secondary to rheumatoid arthritis, ankylosing spondylitis, previous trauma, osteomalacia, etc. Primary Total Hip Replacement (THR) in such cases is difficult because of the deficient medial bone, decreased peripheral bony support to the acetabular component and proximal and medial migration of the joint centre. Several techniques described previously in the surgical management of protrusio acetabuli include cemented acetabular components with cement alone or in association with morselized bone graft to reconstruct the acetabulum. However, cement has high rates of migration and loosening of cemented acetabular components in young patients leads to more revision surgeries within the first decade of implantation. The purpose of the study is to describe the technique and results of using impacted morselized bone graft with a porous coated cementless acetabular component in patients with protrusio acetabuli.A total of 20 primary THR’s (10 unilateral and 5 bilateral) in 15 patients (8 females and 7 males) with protrusio acetabuli were performed between 2018 and 2021, out of which 4 had mild,7 had moderate and 9 had a severe grade of protrusion. A total of 10 hips were affected by rheumatoid arthritis,3 by ankylosing spondylitis and 7 had unknown etiology. After the surgery, all bone grafts had united by the sixth month with no perceptible change in acetabular component position in any case. The mean preoperative Harris Hip Score was 48 which improved to 82 at the latest follow-up. 45% had excellent,33% had good, and 22% had fair results. There was no dislocation. The use of impacted morselized autograft with a cementless porous acetabular component is a good technique of restoration of hip biomechanics and sound fixation in cases of protrusio acetabuli.

One-Dimensional Phononic Crystals: A Simplified Platform for Effective Detection of Heavy Metals in Water with High Sensitivity.

Recently, the pollution of fresh water with heavy metals due to technological and industrial breakthroughs has reached record levels. Therefore, monitoring these metals in fresh water has become essentially urgent. Meanwhile, the conventional periodic one-dimensional phononic crystals can provide a novel platform for detecting the pollution of heavy metals in fresh water with high sensitivity. A simplified design of a defective, one-dimensional phononic crystals (1D-PnC) structure is introduced in this paper. The sensor is designed from a lead-epoxy multilayer with a central defect layer filled with an aqueous solution from cadmium bromide (CdBr2). The formation of a resonant peak through the transmittance spectrum is highly expected. This study primarily aims to monitor and detect the concentration of cadmium bromide in pure water based on shifting the position of this resonant peak. Notably, any change in cadmium bromide concentration can affect the acoustic properties of cadmium bromide directly. The transfer matrix method has been used to calculate the transmission spectra of the incident acoustic wave. The numerical findings are mainly based on the optimization of the cadmium bromide layer thickness, lead layer thickness, epoxy layer thickness, and the number of periods to investigate the most optimum sensor performance. The introduced sensor in this study has provided a remarkably high sensitivity (S = 1904.25 Hz) within a concentration range of (0-10,000 ppm). The proposed sensor provides a quality factor (QF), a resolution, and a figure of merit of 1398.51752, 48,875,750 Hz, and 4.12088 × 10-5 (/ppm), respectively. Accordingly, this sensor can be a potentially robust base for a promising platform to detect small concentrations of heavy metal ions in fresh water.

Heavy metals biosensor based on defective one-dimensional phononic crystals

In recent years, the detection of water pollution with low levels of heavy metals has attracted the great attention of many researchers as a result of the imminent danger of this type of pollution to all mankind. Meanwhile, we introduce a theoretical approach based on the one-dimensional phononic crystals (1D-PnCs) with a central defect layer as a novel platform for the highly sensitive detection of heavy metal pollution in freshwater. Therefore, the creation of a resonant peak in the transmittance spectrum related to this defect layer is highly conceivable. In this regard, the detection of cadmium chloride (CdCl2) as a dangerous, toxic, and extremely hazardous heavy metal could be investigated based on the small displacement in the position of this resonant peak with the changes in the CdCl2 concentration. Notably, any change in CdCl2 concentration has a direct impact on its acoustic properties. The theoretical framework of our research study is essentially based on the 2 × 2 transfer matrix method and the acoustic properties of the constituent materials as well. The optimization of all sensor parameters represents the mainstay of this study to get the best sensor performance. In this regard, the proposed sensor has a remarkably high sensitivity (S = 1904.25 Hz/ppm) over a concentration range of 0 – 10000 ppm. In addition, the sensor has a high quality factor (QF), and figure of merit of 1771.318, and 73529410−5 (ppm−1), respectively. Finally, we believe this sensor could be a key component of a feasible platform for detecting low concentrations of different heavy metal ions in freshwater.

Variability of input gunshot injuries of clothing fabrics

One of the main components of a gunshot injury is the entrance hole. Its characteristic features: round shape, size, the presence of a central tissue defect, abrasion collar (contamination, metallization), are differential diagnostic signs of an entrance gunshot injury. Under the conditions of the conducted experiments, the peculiarities of the variability of the described signs of the entrance holes on the clothing fabrics were studied, depending on the nature of the objects to be subjected and the contact velocity of the firearm projectile. The identified features must be taken into account when examining gunshot injuries, as well as planning and conducting experimental studies with firearms.

線維走行と直交するスリット状損傷部に形成されるマウス膝蓋腱治癒組織の巨視的・微視的力学解析

A lack of the application of appropriate mechanical stimuli to cells within healing tissue in tendon defects has been proposed as a possible mechanism of incomplete defect healing with scar formation. This suggested that different mechanical environment in a tendon defect with a different geometry may result in different healing outcome. Therefore, the present study adopted a slit injury model in a mouse patellar tendon model and performed macroscopic and microscopic mechanical analysis on tissue regenerated in the central slit defect. Tensile strength and tangent modulus of the tissue in the defect at 3 weeks of healing were lower significantly than that of normal patellar tendon, which recovered to a level still lower than the normal level but without statistical significance at 6 weeks of healing. Micromechanical analysis on local strain field revealed that microscopic tensile strain was not different between normal patellar tendon and healing tissue at 6 weeks. However, microscopic transverse and shear strain was significantly lower in healing tissue than normal tendon tissue. The former may indicate that collagen fibers in healing tissue exhibit no crimp morphology, and the latter demonstrates that collagen fibers were not aligned to the long axis of the tendon. Although healing tissue in the slit defect possessed better strength that that in a rectangular defect examined in our previous study, microscopic strain field was similar between two models, possibly due to that healing tissue in both models was still immature structurally at 6 weeks of healing when compared to the normal patellar tendon.

Hyperbaric oxygen treatment for paracentral acute middle maculopathy: a case study

A 47-year-old active-duty Navy diver with a complicated past medical history which resulted in his designation as not physically qualified (NPQ) for diving duty in 2016 presented on 07 May 2021 complaining of left-sided blurred vision. On exam by the attending undersea medical officer he was found to have a left upper inner and upper outer quadrant visual field defect along with a central scotoma. Urgent referral to ophthalmology ruled out retinal detachment but resulted in an initial diagnosis of a left branch retinal artery occlusion without embolus. Considering this a variant of central retinal artery occlusion, hyperbaric oxygen (HBO2) therapy was initiated approximately 12 hours after symptom onset, resulting in complete, though temporary, resolution of the visual field defect. He reported that after completion of his first HBO2 treatment, his visual field deficit began to return, but the deficit again resolved after initiating surface oxygen therapy between HBO2 treatments. After two days of continuous surface oxygen and daily HBO2 treatments, which kept his visual field defect minimized, his deficits changed to a persistent left lateral peripheral defect and a recurrent central nasal defect. At this time, his periodic ophthalmology evaluation revised his diagnosis to cilioretinal artery occlusion (CrAO). Further evaluation by ophthalmology revealed retinal changes consistent with a secondary diagnosis of paracentral acute middle maculopathy (PAMM), an ophthalmologic condition only recently defined in the literature (2013) [10] secondary to advances in retinal imaging technology. This case is presented to share the findings of this complicated case and to postulate a benefit from the use of HBO2 for cilioretinal artery occlusion with PAMM.

A novel approach to improve the macro-segregation defect and mechanical properties of Al–Mg–Mn aluminum alloys during twin-roll continuous casting

In this paper, the microstructure and properties of Al–Mg–Mn alloy slabs with different thicknesses by twin-roll continuous casting were investigated. Under the twin-roll continuous casting process, the alloy melt conducts directional crystallization due to the near-horizontal heat transfer direction. In this way, the growth direction of the columnar crystal is changed to improve the shape and size of the sump and effectively eliminate the central segregation defect. Additionally, the improvement of segregation defects was more significant with the increase in thickness. As low angle grain boundary content and solution degree increased, the electrical conductivity decreased, the hardness increased, and the phenomenon of hard-soft-hard core-shell was significantly improved.

Influence of pinning centers of different natures on surrounding vortices

Studies involving vortex dynamics and their interaction with pinning centers are an important issue to reach higher critical currents in superconducting materials. The vortex distribution around arrays of engineered defects, such as blind and through holes, may help to improve the superconducting properties. Thus, in this work, we used the time-dependent Ginzburg-Landau theory to investigate the vortex dynamics in superconductors of mesoscopic dimensions with a large central square defect with three different configurations: (i) a hole which passes through the sample (interface with the vacuum); (ii) a superconducting region with lower critical temperature Tc; and (iii) a region with a more robust superconductivity, i.e., with a higher Tc. Such systems can be envisaged as elementary building blocks of a macroscopic decorated specimen. Therefore, we evaluated the influence of different interfaces on the vortex dynamics and their effects in the field-dependent magnetization and time-dependent induced electric potential variation. The results show that the superheating field is independent from the nature of the defect. However, the currents crowd at the vertices of the through hole producing a lower degradation of the local superconductivity, which may increase the upper critical field. On the other hand, the last type of defect can be used to control the vortex dynamics in the main superconducting region around the defect with more accuracy. While the first two defects are attractive for the vortices, the third type is repulsive, being needed several penetrated vortices in the superconducting matrix to allow penetration of vortices into the higher Tc domain.

Comparative study of the effect of different temperatures on bovine bone used for bone repair of critical calvaria defects in rats.

To evaluate the osteoconductive potential of inorganic biomaterials of bovine origin submitted to different temperatures in the bone repair of critical defects in rat calvaria. Forty-eight rats were divided into four groups according to the material used to fill the defect: control group (GC), the defect was filled only with blood clot (n=12); GBO, defect filled with Bio-Oss®, deproteinzed at 300°C (n=12); GOX, defect filled with Inorganic GenOx®, deproteinzed from 850 to 1200°C (n=12) and G700, defect filled with Inorganic GenOx 700, deproteinzed at 700°C (n=12). In each animal's calvaria, a trephine bur with 5 mm internal diameter was used to produce a 6 mm-diameter central defect. Gen Derm® resorbable bovine membrane was superimposed over all defects. Subsequently, animals were euthanized at 30 and 60 days after surgery. The pieces were sent for histological and histometric analysis to evaluate the following variables: bone neoformation, presence of biomaterial, mononuclear and polymorphonuclear leukocytes, presence of other tissues (granulation and medullary) and maturation of collagen fibers. The most representative group for bone neoformation was GC. At 30 days, there was a higher mean of mature bone tissue (75.8). At 60 days, there was no statistical difference between the GC (64.9), GBO (32.9), GOX (45.3), and G700 (26.6) groups. GBO presented the highest amount of biomaterial after 30 days (115.9) and 60 days (118.5). All bovine biomaterials were biocompatible and osteoconductive. GOX promoted the best bone repair of the studied materials.

Optical vortex beam controlling based on fork grating stored in a dye-doped liquid crystal cell.

In this paper, we investigate the generation and controlling of the optical vortex beam using a dye-doped liquid crystal (DDLC) cell. The spatial distribution of the quasi-sinusoidal orientation of the liquid crystal molecules creates a quasi-sinusoidal phase grating (PG) in the DDLC cell. Depending on the incident light pattern, Trans to Cis photoisomerization of the dye molecules affects the orientation of the liquid crystal molecules. To do so, an amplitude fork grating (FG) is used as a mask, and its pattern is stored in the cell by a pattern printing method as the PG. One of the particular features of the stored grating in the cell is its capability in the diffraction efficiency controlled by the applied electric field. The results show, based on the central defect in the FG pattern, the diffracted probe beam in different orders is optical vortices. As a new technique, this type of stored pattern acts like an amplitude grating but according to the results, its structure is in fact a PG. This technique leads to the vortex beam switching capability by applying an electric field to the cell. The results show that by applying 22V, all the diffraction orders vanish. Meanwhile, the vortex beams reappear by removing the applied voltage. The diffraction efficiency of the vortex beams as well as its generation dependency on the polarization of the incident beam studied. The maximum efficiency of the first diffraction order for linear polarized incident beam was obtained at 0V, about 8%. Based on the presented theory, a simulation has been done which shows the Cis form of the dye molecules has been able to change the angle of LC molecules on average about 12.7°. The study of diffracted beam profiles proves that they are electrically controllable vortex beams.

Tunable spatial Goos-Hänchen shift in periodic PT-symmetric photonic crystals with a central defect

The Goos-Hänchen (GH) effects are investigated for a transverse magnetic beam totally reflected by periodic PT-symmetric photonic crystals. A dielectric layer with a real refractive index situates as a defect in the center. Both positive and negative spatial GH shifts are induced around the defect mode. The GH shifts sensitively change with the refractive index of the defect layer. More importantly, giant negative GH shift effect with big reflectance could be found and modulated by increasing the gain-loss factor in PT-symmetric systems, which could improve the detecting sensitivity of the defect. Our study may be valuable in potential applications for highly sensitive sensors.

Relative prevalence and outcome of fetal posterior fossa abnormality.

To find out the relative incidence and outcome of posterior fossa abnormality (PFA) in terms of survival at birth until 2 years of age. We conducted a prospective study; all fetuses diagnosed with posterior fossa abnormality were followed-up. The outcome was observed with respect to survival, the presence of associated anomalies, the existence of developmental delay after a telephonic interview. Out of 2703 children with congenital anomalies, 921 (34.1%) had a central nervous system defect;76 cases of PFA were fully followed. Dandy-Walker malformation (DWM) was present in 50% (38/76), mega cisterna magna 18.4% (14/76), Blake pouch cyst 13.2% (10/76), vermian hypoplasia (VH) 13.2% (10/76) and arachnoid cyst 5.2% (4/76). The diagnosis was possible before 20 weeks in only 12 (15.8%) cases.The mean gestational age at delivery was 34.7 ± 6.7 weeks. Associated anomalies were seen in 35/76 (46.1%) cases. A total of 35/76 (46.1%) survived after 2 years; there was developmental delay in 9.2% of cases. There is a large variation in the outcome of PFA depending upon the type of anomaly. Associated anomalies are common in VH and DWM, making their prognosis worse.